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Human  Anatomy 


The  skeleton  in  relation  to  the  contour  of   the  body. 


HUMAN   ANATOMY 

INCLUDING  STRUCTURE  AND  DEVELOPMENT 

AND 

PRACTICAL  CONSIDERATIONS 


THOMAS  DWIGHT,  M.D.,  LL.D.  J.  PLAYFAIR  McMURRICH,  PH.D. 

ilKMAN     PROFESSOR      OF      ANATOMY      IN      HARVARD  PROFESSOR     OF     ANATOMY     IN     THE     UNIVERSITY     O 

UNIVERSITY  MICHIGAN 

CARL  A.  HAMANN,  M.D.  GEORGE  A.  PIERSOL,  M.D.,  SC.D. 


J.  WILLIAM  WHITE,  M.D.,  PH.D.,  LL.D. 

JOHN  RHEA   BARTON  PROFESSOR  OF  SURGERY   IN  THE   UNIVERSITY  OF   PENNSYLVANIA 


WITH    SEVENTEEN    HUNDRED    AND    THIRTY-FOUR     ILLUSTRATIONS. 

OF    WHICH    FIFTEEN    HUNDRED    AND    TWENTY-TWO  ARE  ORIGINAL 

AND  LARGELY  FROM  DISSECTIONS  BY 

JOHN  C.  HEISLER,  M.D. 

PROFESSOR    OF   ANATOMY    IN    THE    MEDICO-CHIRURGICAL  COLLEGE 


EDITED    BY 

GEORGE  A.  PIERSOL 


VOL.   I. 

THIRD    EDITION 


PHILADELPHIA  &  LONDON 
J.  B.  LIPPINCOTT  COMPANY 


' 


Copyright,  1906,  by  J.  B.  Lippincott  Company. 
Copyright,  1907,  by  J.  B.  Lippincott  Company. 
Copyright,  1908,  by  J.  B.  Lippincott  Company. 
Copyright,  191 1,  by  J.  B.  Lippincott  Company. 


Entered  at  Stationers'  Hall,  London,  England. 

All  Rights  Reserved. 


PREFACE. 


The  preparation  of  this  work  was  undertaken  with  three  chief  considerations  in 
mind.  i.  The  presentation  of  the  essential  facts  of  human  anatomy,  regarded  in  its 
broadest  sense,  by  a  descriptive  text  which,  while  concise,  should  be  sufficiently  com- 
prehensive to  include  all  that  is  necessary  for  a  thorough  understanding  not  only  of 
the  gross  appearances  and  relations  of  the  various  parts  of  the  human  body,  but  also 
of  their  structure  and  development.  2.  Adequate  emphasis  and  explanation  of  the 
many  and  varied  relations  of  anatomical  details  to  the  conditions  claiming  the  atten- 
tion of  the  physician  and  surgeon.  3.  The  elucidation  of  such  text  by  illustrations 
that  should  portray  actual  dissections  and  preparations  with  fidelity  and  realism. 

To  the  first  of  these  ends  the  co-operation  of  several  American  teachers  of 
anatomy  was  enlisted,  whose  contributions  have  been  welded  into  a  homogeneous 
whole. 

Dr.  Thomas  Dwight  has  written  the  description  of  the  skeleton,  including  the 
joints,  and  that  of  the  gastro-pulmonary  system  and  of  the  accessory  organs  of 
nutrition. 

Dr.  Carl  A.  Hamann  has  contributed  the  account  of  the  cerebro-spinal  and 
sympathetic  nerves. 

Dr.  J.  Playfair  McMurrich  has  supplied  the  systematic  description  of  the  mus- 
cular and  of  the  blood-  and  lymph-vascular  system. 

Dr.  George  A.  Piersol  has  written  the  introductory,  histological  and  embryolog- 
ical  paragraphs  throughout  the  work  and  contributed  the  description  of  the  central 
nervous  system,  including  the  deep  relations  of  the  cranial  nerves,  of  the  organs  of 
special  sense,  of  the  carotid,  coccygeal  and  aortic  bodies,  and  of  the  uro-genital  system. 

The  second  desideratum — adequate  consideration  of  the  practical  applications 
of  anatomy — has  been  ensured  by  the  co-operation  of  Dr.  J.  William  White, 
whose  ripe  experience,  both  as  a  surgeon  and  as  a  teacher  of  surgery,  has  enabled 
him  to  point  out  with  unusual  force  the  relations  of  anatomy  to  the  requirements  of 
the  practitioner,  and  to  associate  for  the  benefit  of  the  student  anatomical  facts  with 
those  conditions,  resulting  from  injury  or  disease,  that  these  facts  elucidate. 

While  no  attempt  has  been  made  to  cover  the  field  of  operative  surgery,  brief 
descriptions  of  operative  methods  have  been  given  when  they  have  seemed  necessary 
to  complete  the  study  of  an  anatomical  region  or  of  an  important  organ.  Occasion- 
ally a  relatively  rare  operation  has  been  included  because  of  the  exceptional  practical 
importance  of  the  subject  from  an  anatomical  standpoint. 

The  writer  of  the  Practical  Considerations  has  aimed  at  presenting,  in  connection 
with  each  organ  or  system,  enough  facts  illustrative  of  the  dependence  of  the  diag- 
nostician and  practitioner  upon  anatomical  knowledge  to  awaken  interest  and  to  com- 
bat the  tendency  to  regard  anatomy  as  something  to  be  memorized  during  student 
days  and  forgotten  when  examinations  are  over.  Even  when  such  facts  do  not  seem 
at  a  first  glance  to  come  within  the  scope  of  a  text-book  of  anatomy,  it  will  be  found 
that  a  careful  comparison  of  this  text  with  the  descriptive  portion  of  the  book  will 
show  a  real  and  practical  relation  between  them — a  relation  which,  once  established 


vi  PREFACE. 

in  the  minds  of  the  student  and  the  physician,  will  make  it  easier  for  the  former  to 
learn  his  anatomy  and  for  the  latter  to  remember  and  apply  it. 

Dr.  White  desires  to  acknowledge  fully  his  obligations  to  the  existing  treatises 
on  applied  anatomy  and  to  the  various  text-books  and  encyclopedias  on  surgery  and 
medicine  from  which  many  valuable  suggestions  were  gathered.  To  Drs.  Gwilym 
G.  Davis  and  T.  Turner  Thomas,  his  thanks  are  due  for  a  careful  search  for  possible 
errors,  for  friendly  criticism,  and  for  help  in  the  selection  of  illustrations. 

The  illustrations  for  the  anatomy — a  matter  of  fundamental  importance  in  a  work 
of  this  character — have  received  most  conscientious  attention.  The  determination  to 
produce  a  series  of  original  drawings  that  should  faithfully  record  the  dissections  and 
preparations  as  they  actually  appear,  and  not  as  diagrammatic  figures,  has  involved 
an  expenditure  of  time  and  painstaking  effort  that  only  those  having  experience  with 
similar  tasks  can  appreciate.  When  it  is  stated  that  considerably  more  than  two 
thousand  original  drawings  have  been  made  in  the  preparation  of  the  figures  illus- 
trating the   work,   some  conception  will  be  had  of   the  magnitude  of  this  feature. 

In  the  completion  of  this  labor  the  editor  has  been  most  fortunate  in  having 
the  assistance  of  Dr.  John  C.  Heisler,  to  whose  skill  and  tireless  enthusiasm  he  is 
indebted  for  the  admirable  dissections  from  which  most  of  the  illustrations  of  the 
muscles,  blood-vessels,  nerves,  perineum  and  inguinal  region  were  drawn,  as  well  as 
for  many  suggestions  for  and  revision  of  the  drawings  themselves.  Professor  Gwilym 
G.  Davis  has  also  rendered  valuable  assistance  in  supplying  the  dissections  for  the 
drawings  relating  to  the  Practical  Considerations,  as  well  as  in  supervising  that 
portion  of  the  artist's  work. 

In  addition  to  the  numerous  dissections  and  preparations  made  especially  for  the 
illustrations,  advantage  has  been  taken  of  the  rich  collections  in  the  museums  of  the 
Medical  Department  of  the  University  of  Pennsylvania,  of  the  Harvard  Medical 
School  and  of  the  Wistar  Institute  of  Anatomy,  which  were  kindly  placed  at  the 
editor's  service. 

Records  of  the  dissections,  in  many  cases  life  size,  were  made  in  water  colors 
chiefly  by  Mr.  Hermann  Faber,  whose  renditions  combine  faithful  drawing  with 
artistic  feeling  to  a  degree  unusual  in  such  subjects.  The  records  not  made  by  the 
last-named  artist  are  from  the  brush  of  Mr.  Ludwig  E.  Faber.  The  translations 
of  the  colored  records  into  black  and  white,  from  which  the  final  blocks  have  been 
made,  as  well  as  the  original  drawings  of  the  bones  and  of  the  organs,  have  been 
made  by  Mr.  Erwin  F.  Faber.  To  the  conscientious  and  tireless  efforts  of  this  artist 
are  due  the  technical  beauty  that  distinguish  these  illustrations.  Mr.  J.  H.  Emerton 
drew  the  joints,  as  well  as  some  figures  relating  to  the  gastro-pulmonary  system,  from 
dissections  and  sections  supplied  by  Professor  Dwight-. 

The  numerous  illustrations  representing  the  histological  and  embryological  de- 
tails throughout  the  work,  and  in  addition  the  sections  of  the  brain-stem  under  low 
magnification,  are  by  Mr.  Louis  Schmidt.  In  all  cases  sketches  with  the  camera 
lucida  or  projection  lantern  or  photographs  have  been  the  basis  of  these  drawings, 
the  details  being  faithfully  reproduced  by  close  attention  to  the  original  specimens 
under  the  microscope. 

Notwithstanding  the  unusually  generous  allotment  of 'drawings  from  original 
dissections  and  preparations,  advantage  has  also  been  taken  of  a  number  of  illus- 
trations which  have  appeared  in  special  monographs  or  in  foreign  journals  or  works. 
With  very  few  exceptions  such  borrowed  illustrations  have  been  redrawn  and  modi- 
fied to  meet  the  present  requirements,  due  acknowledgment  in  all  cases  being  given. 


PREFACE.  vii 

The  editor  gratefully  acknowledges  the  many  kindnesses  shown  by  a  number  of 
his  associates.  Dr.  William  G.  Spiller  generously  placed  at  his  disposal  a  large 
collection  of  microscopical  preparations  of  the  central  nervous  system,  from  which 
drawings  of  selected  sections  were  made.  To  Dr.  George  Fetterolf  the  editor  is 
indebted  for  valuable  assistance  in  preparing  for  and  seeing  through  the  press  the 
section  on  the  peripheral  nervous  system.  The  collaboration  of  Dr.  Edward  A. 
Shumway  very  materially  facilitated  the  preparation  of  the  description  of  the  eye, 
which  received  only  the  editor's  revision.  Likewise,  Dr.  Ralph  Butler,  by  placing 
in  the  editor's  hands  a  painstaking  review  of  the  more  recent  literature  on  the  ear 
and  preliminary  account  of  that  organ,  greatly  lightened  the  labor  of  writing  the  text. 
Further,  Dr.  Butler  supplied  the  microscopical  preparations  from  which  several  of 
the  drawings  were  made.  In  addition  to  assuming  the  preparation  of  the  index — a  no 
insignificant  undertaking  in  a  work  of  this  character — Dr.  Ewing  Taylor  gave  valu- 
able assistance  in  the  final  revision  of  the  first  hundred  pages  of  the  book.  The 
editor  is  indebted  to  Dr.  W.  H.  F.  Addison  for  repeated  favors  in  preparing  special 
microscopical  specimens.  Dr.  T.  Turner  Thomas  kindly  assisted  in  locating  cross- 
references.  This  opportunity  is  taken  to  express  full  appreciation  and  thanks  to  the 
various  authors  and  publishers,  who  so  kindly  have  given  permission  to  use  illus- 
trations which  have  appeared  elsewhere. 

Very  earnest  consideration  of  the  question  of  nomenclature  led  to  the  conclusion, 
that  the  retention,  for  the  most  part,  of  the  terms  in  use  by  English-speaking 
anatomists  and  surgeons  would  best  contribute  to  the  usefulness  of  the  book.  While 
these  names,  therefore,  have  been  retained  as  the  primary  terminology,  those 
adopted  by  the  Basle  Congress  have  been  included,  the  BNA  synonyms  appear- 
ing in  the  special  type  reserved  for  that  purpose.  The  constant  aim  of  the  editor 
has  been  to  use  the  simplest  anatomical  terminology  and  preference  has  always 
been  given  to  the  anglicized  names,  rather  than  to  the  more  formal  designations. 
Although  in  many  cases  the  modifications  suggested  by  the  new  terminology  have 
been  followed  with  advantage,  consistent  use  of  the  Basle  nomenclature  seems  less  in 
accord  with  the  conceded  directness  of  English  scientific  literature  than  the  enthusi- 
astic advocates  of  such  adoption  have  demonstrated. 

The  editor  desires  to  express  his  appreciation  of  the  generous  support  given  him 
by  the  publishers  and  of  the  unstinted  facilities  placed  by  them  at  his  disposal 
throughout  the  preparation  of  the  work. 

University  of  Pennsylvania, 
September,   1907. 


CONTENTS. 

VOL.    I. 
INTRODUCTION. 


Relation  of  Anatomy  to  Biology  .  . 
Subdivisions  of  Anatomical  Study 


General  Plan  of  Vertebrate  Construction 
Descriptive  Terms 


THE  ELEMENTS  OF  STRUCTURE. 


The  Elementary  Tissues 

The    Cells    and    Intercellular    Sub- 
stances  

The  Embryonal  Cell 

Vital  Manifestations 

Metabolism 

Growth 

Reproduction  


Irritability 6 

The  Animal  Cell 6 

Structure  of  the  Cytoplasm 7 

Structure  of  the  Nucleus 8 

The  Centrosome 9 

Division  of  Cells 10 

Mitotic  Division 11 

Amitotic  Division 14 


EARLY  DEVELOPMENT. 


The  Ovum 

The    Spermatozoon 

Maturation  of  the  Ovum 

Fertilization  of  the  Ovum 

Segmentation  of  the  Ovum 

The  Blastoderm  and   the  Blastodermic 

Layers 

Derivatives  of  the  Blastodermic  Layers.  . 
The  Primitive  Streak  and  the  Gastrula.  . 
The  Significance  of  the  Primitive  Streak.  . 
The  Fundamental  Embryological  Pro- 
cesses   

The  Neural  Canal 

The  Notochord 

The  Ccelom 

The  Somites 

The  Fcetal   Membranes 

The   Amnion 

The  Serosa 

The  Vitelline  Sac 

The  Allantois  and  the  Chorion 


The  Human  Fcetal  Membranes 35 

The  Amnion  and  Allantois 35 

The  Chorion 41 

The  Amniotic  Fluid 41 

The  Umbilical  Vesicle 42 

The  Deciduae 44 

The  Trophoblast 46 

The  Decidua  Vera 46 

The  Decidua  Placentalis 48 

The  Placenta 49 

The  Umbilical  Cord 53 

The  After-Birth 55 

Development  of  Body-Form 56 

The  Stage  of  the  Blastodermic  Ves- 
icle    56 

The  Stage  of  the  Embryo 56 

The  Visceral   Arches   and  Fur- 
rows    59 

The  Development  of  the  Face  .  .  62 

The  Stage  of  the  Fcetus 63 


THE  ELEMENTARY  TISSUES. 


The  Epithelial  Tissues 67 

Squamous  Epithelium 68 

Columnar  Epithelium 69 

Modified  Epithelium 70 

Specialized  Epithelium 70 

Endothelium 71 

The  Connective  Tissues 73 

The  Cells  of  Connective  Tissue 73 

The  Intercellular  Constituents 74 

Fibrous  Tissue 74 

Reticular  Tissue 75 

Elastic  Tissue 76 

Development  of  Connective  Tissue  .  77 

Tendon 77 

Adipose  Tissue 79 

Cartilage 80 


fhe  Connective  Tissues — Continued 

Hyaline  Cartilage 80 

Elastic  Cartilage Si 

Fibrous  Cartilage 82 

Development  of  Cartilage 82 

Bone .-.■■•■ S4 

Chemical  Composition 84 

Physical  Properties 85 

Structure  of  Bone S5 

Bone  Marrow 90 

Red   Marrow 91 

Yellow  Marrow 93 

Development  of  Bone 94 

Endochondral  Bone 94 

Membranous  Bone 9S 

Subperiosteal  Bone 98 


THE  SKELETON,    INCLUDING  THE  JOINTS. 


The  Axial  Skeleton 103 

The  Appendicular  Skeleton 104 

General  Considerations  of  the  Bones ....     104 


General  Considerations  of  the  Joints  ....     107 

The  Spinal  Column 114 

The  Thoracic  Vertebra? 115 


X 


CONTENTS. 


PAGE 

The  Thoracic  Vertebra; — Continued 

The  Cervical  Vertebra; 116 

The  Lumbar  Vertebra? 117 

Peculiar  Vertebra; 119 

Dimensions  of  Vertebra; 122 

Gradual  Regional  Changes 122 

The  Sacrum 124 

The  Coccyx 127 

Development  of  the  Vertebra; 128 

Variations  of  the  Vertebrae 131 

Articulations  of  the  Vertebral  Column  .  .  132 

Ligaments  Connecting  the  Bodies  .  .  132 
Ligaments  Connecting  the  Laminae 

and  the  Processes 133 

Articulations  of  the  Occipital  Bone,  the 

Atlas  and  the  Axis 135 

The  Spine  as  a  Whole 13S 

Dimensions  and  Proportions 141 

Movements  of  the.  Head 142 

Movements  of  the  Spine 142 

Practical  Considerations  :  The  Spine.  ...  143 

Curvature  of  the  Spine 144 

Sprains,  Dislocations  and  Fractures  .  144 

Landmarks 146 

The  Thorax 149 

The  Ribs 149 

The  Costal  Cartilages 153 

The  Sternum 155 

Articulations  of  the  Thorax 157 

The  Anterior  Thoracic  Articulations .  158 

The  Intersternal  Joints 159 

The  Costo-Sternal  Joints 160 

The  Interchondral  Joints 160 

The  Costo- Vertebral  Articulations.  .  160 

The  Thorax  as  a  Whole ' 162 

The  Movements  of  the  Thorax 165 

Practical  Considerations  :  The  Thorax  .  .  167 

Deformities 167 

Fractures  and  Disease  of  the  Ribs  .  .  169 

Landmarks 170 

The  Skull 172 

The  Cranium 172 

The  Occipital  Bone 172 

The  Temporal  Bone 176 

The  Tympanic  Cavity 1S3 

The  Sphenoid  Bone 1S6 

The  Ethmoid  Bone 191 

The  Frontal  Bone 194 

The  Parietal  Bone 197 

The  Bones  of  the  Face 199 

The  Superior  Maxilla 199 

The  Palate  Bone 204 

The  Vomer 205 

The  Lachrymal  Bone 207 

The  Inferior  Turbinate  Bone 208 

The  Nasal  Bone : 209 

The  Malar  Bone 209 

The  Inferior  Maxilla 211 

The  Temporo-Maxillary  Articulation.  . .  .  214 

The  Hyoid  Bone 216 

The  Skull  as  a  Whole ■ 216 

The  Exterior  of  the  Cranium 218 

The  Interior  of  the  Cranium 220 

The  Architecture  of  the  Cranium  .  .  .  220 

The  Face 222 

The  Orbit 222 

The  Nasal  Cavity 223 

The  Accessory  Pneumatic  Cav- 
ities   226 

The  Architecture  of  the  Face  . .  .  22S 

The  Anthropology  of  the  Skull 228 

Practical  Considerations  :  The  Skull  ....  235 

The  Cranium 235 


Pract.  Consid. :  The  Skull — Continued 

Malformations 235 

The  Wormian  Bones 236 

Diseases  of  the  Cranial  Bones  .  .  237 

Fractures  238 

Landmarks 240 

The  Face 242 

Deformities  and  Fractures 243 

Dislocation  of  the  Jaw 246 

Landmarks 246 

The  Bones  of  the  Upper  Extremity 24S 

The   Shoulder-Girdle 248 

The  Scapula 248 

Practical  Considerations 253 

Malformations 253 

Fractures  and  Disease 254 

Landmarks 255 

Ligaments  of  the  Scapula 256 

The  Clavicle 257 

Practical  Considerations 258 

Malformations 259 

Fractures  and  Disease 259 

Landmarks 260 

The  Sterno-Clavicular  Articulation  .  261 
The  Coraco-Clavicular  Ligament  .  .  .  262 
Movements  of  the  Clavicle  and  Scap- 
ula    262 

Surface  Anatomy  of  the  Shoulder- 
Girdle  263 

Practical  Considerations 263 

The  Sternoclavicular  Articula- 
tion    263 

The  Acromio-Clavicular  Articu- 
lation   ; . .  .  264 

The  Humerus 265 

Practical  Considerations 270 

Malformations 270 

Separation  of  the  Epiphyses  ....  271 

Fractures  and  Disease 273 

The  Shoulder-Joint 274 

Practical  Considerations 27S 

Dislocations  and  Diseases 278 

Landmarks 280 

The  Ulna 281 

Practical  Considerations 285 

Malformations 285 

Fractures 286 

Landmarks 287 

The  Radius 287 

Practical  Considerations 293 

Malformations 293 

Fractures  and  Disease 294 

Landmarks 296 

The  Radio-Ulnar  Articulations 297 

The  Forearm  as  a  Whole 299 

The  Elbow-Joint 301 

Practical  Considerations 305 

Dislocations  and  Disease 305 

Landmarks 308 

The  Bones  of  the  Hand 309 

The  Carpal  Bones 309 

The  Metacarpal  Bones 314 

The  Phalanges 317 

Practical  Considerations 319 

The  Carpus 319 

The  Metacarpus 319 

The  Phalanges 320 

Landmarks 320 

Ligaments  of  Wrist  and  Metacarpus  ....  320 
Movements  and  Mechanics  of  Wrist 
and     Carpo-Metacarpal    Articu- 
lations    326 

Surface    Anatomy  of    Wrist  and  Hand  328 


CONTENTS. 


Practical     Considerations:   The     Wrist- 
Joint 329 

Landmarks 330 

The  Joints  of  the  Carpus,  Metacarpus 

and  Phalanges 630 

The  Bones  of  the  Lower  Extremity 332 

The  Pelvic  Girdle 332 

The  Innominate  Bone 332 

Joints  and  Ligaments  of  the  Pelvis .  .  337 

The  Sacro-Iliac  Articulation.  ..  .  338 

The  Symphysis  Pubis 339 

The  Sacro-Sciatic  Ligaments  .  .  339 

The  Pelvis  as  a  Whole 341 

Mechanics  of  the  Pelvis 342 

Surface  Anatomy 345 

Practical  Considerations:  The   Pelvis  .  .  345 

Malformations 345 

Fractures  and   Disease 346 

Landmarks 349 

Joints  of  the  Pelvis 350 

The  Femur 352 

Surface  Anatomy 360 

Practical  Considerations: :  . .  .  361 

The  Epiphyses 361 

Fractures  and  Disease 363 

Landmarks 366 

The  Hip-Joint 367 

Practical  Considerations 374 

Outward  or  Posterior  Luxations.  ..  .  375 

Inward  or  Anterior  Luxations 377 

Congenital  Luxation 380 

Disease  of  the  Hip-Joint 380 

The  Framework  of  the  Leg 382 

The  Tibia 382 

Practical  Considerations 387 

Separation  of  the  Epiphyses 387 

Fractures  and  Disease 389 

Landmarks 390 


The  Fibula 391 

Practical  Considerations 393 

Separation   of   Upper  Epiphysis.  ..  .  393 

Fractures   and   Disease 394 

Landmarks 396 

Connections  of  the  Tibia  and  Fibula.  . .  .  396 

The  Bones  of  the  Leg  as  one  Apparatus  397 

The  Patella 398 

The  Ligamentum  Patella; , .  400 

The  Knee-joint 400 

Practical     Considerations  :     The     Knee- 
joint  409 

Dislocations 409 

Subluxation  of  Semilunar  Cartilages  411 

Disease  of  Knee-joint 412 

The  Patella 416 

The  Bones  of  the   Foot 419 

The  Tarsal   Bones 419 

The  Metatarsal  Bones 428 

The   Phalanges 432 

Practical     Considerations :     The     Foot- 
Bones  436 

Fracture,  Dislocation  and  Disease.  .  437 

Landmarks 437 

The  Ankle-joint 438 

The  Articulations  of   the  Foot 440 

Intertarsal   Joints 445 

Tarso-Metatarsal  Joints 446 

Metatarso-Phalangeal  Joints 447 

Synovial  Cavities 447 

The  Foot  as  a  Whole 447 

Surface  Anatomy 449 

Practical    Considerations:     The   Ankle- 
joint 450 

Dislocations  and  Disease 450 

Tarsal,    Metatarsal    and   Phalangeal 

Joints 451 

Landmarks 453 


THE    MUSCULAR    SYSTEM. 


Muscular  Tissue   in  general 454 

Nonstriated  or  Involuntary  Muscle.  .  454 

Structure 455 

Development .  457 

Striated  or  Voluntary  Muscle 457 

General  Structure 458 

Structure  of  the  Muscle-Fibre.  .  459 

Cardiac  Muscle 462 

Development  of  Striated  Muscle.  465 
Myomeres    and    their    Modifica- 
tions    467 

General  Consideration  of  the  Muscles.  . .  .  468 

Attachments 468 

Form 469 

Fascia; 47° 

Tendon-Sheaths 470 

Bursa; 471 

Classification 471 

Nerve-Supply 473 

The  Branchiomeric  Muscles 474 

The  Trigeminal  Muscles 474 

Muscles  of  Mastication 474 

Submental  Muscles 477 

Trigeminal  Palatal  Muscle 479 

Trigeminal  Tympanic  Muscle 479 

The  Facial  Muscles 479 

Hyoidean  Muscles  480 

Platysma  Muscles 4S0 

Superficial  Layer 4S1 

Deep  Layer 4s6 


Practical   Considerations :    Muscles   and 

Fascia;  of  Cranium 489 

The  Scalp 4S9 

The  Face 492 

Landmarks 494 

The  Vago-Accessory  Muscles 495 

Muscles  of  Palate  and  Pharynx 495 

Muscles  of  Larynx  . .  Vol.  II 1824 

Trapezius  Muscles 499 

The  Metameric  Muscles 502 

The  Axial  Muscles 5°2 

Orbital  Muscles 5°2 

Fasciae  of  Orbit 504 

Movements  of  Eyeball 505 

Hypoglossal  Muscles 506 

The  Trunk  Muscles 5°7 

The  Dorsal  Muscles 5°7 

Transverso-Costal  Tract 508 

Transverso-Spinal  Tract 511 

The  Ventral  Muscles 515 

Abdominal  Muscles 515 

Rectus  Muscles 516 

Obliquus  Muscles 517 

Ventral  Aponeurosis 521 

Inguinal  Canal 523 

Anterior  Abdominal  Wall .  .  525 

Hyposkeletal  Muscles 526 

Practical   Considerations  :     The     Abdo- 
men    526 

The  Loin 530 


CONTENTS. 


Practical  Considerations — Continued 

Landmarks    a  nd     Topography     o  f 

Abdomen 531 

Anatomy  of  Abdominal  Incisions.  .  .  535 

Examination  of  Abdomen 537 

The  Thoracic  Muscles 538 

Rectus  Muscles 538 

Obliquus  Muscles 538 

.    Hyposkeletal  Muscles 542 

The  Cervical  Muscles 542 

The  Deep  Cervical  Fascia 542 

Rectus  Muscles 543 

Obliquus  Muscles 546 

Triangles  of  the  Neck 547 

Hyposkeletal  Muscles 548 

Practical  Considerations  :  The  Neck.  . .  .  550 

Cervical  Fascia  and  its  Spaces 551 

Landmarks 554 

The  Diaphragm 556 

The  Pelvic  and  Perineal  Muscles 558 

Pelvic  Fascia 55S 

Obturator  Fascia 559 

Pelvic  Muscles 559 

Perineal  Muscles 562 

The  Appendicular  Muscles 566 

The  Muscles  of  the  LTpper  Limb 568 

Muscles  extending  between  Axial  Skele- 
ton and  Pectoral  Girdle 56S 

Pectoral  Fascia 568 

Preaxial  Muscles 568 

Postaxial  Muscles 571 

The  Axilla 574 

Muscles  passing   from  Pelvic   Girdle   to 

Brachium 575 

Preaxial  Muscles 575 

Postaxial  Muscles 575 

Practical   Considerations :    Muscles  and 

Fascia  of  Axilla  and  Shoulder.  .  579 

Fracture  of  Clavicle 579 

Dislocation  of  Shoulder- Joint 582 

The  Brachial  Muscles 5S5 

Preaxial  Muscles 585 

Postaxial  Muscles 5SS 

Practical   Considerations :    Muscles  and 

Fascia  of  the  Arm 589 

Fractures  of  Humerus 590 

The  Antibrachial  Muscles 591 

Preaxial  Muscles 592 

Postaxial  Muscles 598 

Practical  Considerations  :   The  Forearm.  603 

The  Muscles  of  the  Hand 606 

Deep  Fascia 606 


PAGE 

The  Muscles  of  the  Hand — Continued 

Preaxial   Muscles 607 

Muscles  of  First  Layer   607 

Muscles  of  Second  Layer 610 

Muscle  of  Third  Layer 610 

Muscles  of  IV  and  V  Layers.  ...  611 

Postaxial  Muscle 613 

Pract.  Consid. :   The  Wrist  and  Hand..  .  613 

Palmar  Abscesses 616 

Dislocation  of  Thumb 617 

Surface  Landmarks  of  Upper  Extremity  .  618 

The  Muscles  of  the  Lower  Limb 623 

Muscles  extending  from  Pelvic  Girdle  to 

Femur 623 

Preaxial  Muscles 623 

Postaxial  Muscles 630 

The  Femoral  Muscles 633 

Fascia  Lata 633 

Preaxial  Muscles 636 

Postaxial  Muscles 639 

Practical    Considerations :    Muscles   and 

Fasciae 641 

The  Buttocks 641 

The  Hip  and  Thigh 642 

Fractures  of  the  Femur 644 

The  Knee 645 

Bursa;  of  Popliteal  Region 646 

The  Crural  Muscles 647 

The  Crural  Fascia 647 

Preaxial  Muscles 648 

Superficial  Layer 649 

Middle  Layer 651 

Deep  Layer 654 

Postaxial  Muscles 655 

The  Muscles  of  the  Foot 659 

The  Plantar  Fascia 659 

Preaxial  Muscles 659 

First  Layer 660 

Second  Layer 662 

Third  Layer 662 

Fourth  and  Fifth  Layers 663 

Postaxial  Muscles 665 

Practical   Considerations  :    Muscles    and 

Fasciae 665 

The  Leg 665 

The  Ankle  and  Foot 666 

Club-Foot 667 

Surface  Landmarks  of  Lower  Extremitv  669 

The  Buttocks  and  Hip 669 

The  Thigh 670 

The  Knee 671 

The  Leg 671 

The  Ankle  and  Foot 672 


THE    VASCULAR    SYSTEM. 


The  Blood-Vascular  System. 

The  Structure  of  Blood- Vessels 673 

The  Arteries 675 

The  Veins 677 

The  Capillaries 678 

The  Blood 680 

General  Characteristics 680 

Blood-Crystals 680 

The  Colored  Blood-Cells 6S1 

The  Colorless  Blood-Cells 684 

The  Blood-Plaques 6S5 

Development     of     Blood- Vessels      and 

Cells 686 


The  Heart 6S9 

General  Description 689 

Position  and  Relations 692 

Chambers  of  the  Heart 693 

Architecture  of  the  Heart-Muscle.  .  .  700 

Structure 702 

Blood- Vessels  and  Lymphatics 703 

Nerves 7°4 

Development 705 

Practical  Considerations:   The  Heart.  ..  .  710 

Valvular  Disease 711 

Rupture  and  Wounds 713 

The  Pericardium 714 


CONTENTS. 


Practical   Considerations:    The   Pericar- 
dium    717 

The  General  Plan  of  the  Circulation  ....  719 

The  Arteries 719 

General  Plan  of  Arterial  System ....  720 

The  Pulmonary  Aorta 722 

The  Systemic  Aorta 723 

The  Aortic  Arch 723 

Practical    Considerations:    Aortic    Arch 

and  Thoracic  Aorta 726 

Surface  Relations 726 

Aneurisms 727 

The  Coronary  Arteries 728 

The  Innominate  Artery 729 

Practical  Considerations 729 

The  Common  Carotid  Arteries 730 

Practical  Considerations 731 

The  External  Carotid  Artery 733 

Practical  Considerations 733 

Branches   of    External    Carotid   Ar- 
tery    734 

The  Internal  Carotid  Artery 746 

Practical  Considerations 747 

Branches    of     Internal    Carotid    Ar- 
tery     748 

Anastomoses  of  Carotid  System.  ..  .  753 

The  Subclavian  Artery 753 

Practical  Considerations 756 

Branches  of  Subclavian  Artery 758 

The  Axillary  Artery 767 

Practical  Considerations 769 

Branches  of  Axillary  Artery 771 

The  Brachial  Artery 773 

Practical  Considerations 775 

Branches  of  Brachial  Artery 777 

The  Ulnar  Artery.  . 778 

Practical  Considerations 780 

Branches  of  Ulnar  Artery 781 

The  Radial  Artery 785 

Practical  Considerations 7S6 

Branches  of  Radial  Artery 7S7 

The  Thoracic  Aorta 791 

Branches  of  Thoracic  Aorta 792 

The  Abdominal  Aorta 794 

Practical  Considerations 796 

The  Visceral  Branches 797 

The  Parietal  Branches 805 

The  Common  Iliac  Arteries 807 

Practical  Considerations 807 

The  Internal  Iliac  Artery 808 

Practical  Considerations 810 

Branches  of  Internal  Iliac  Artery.  . .  .  810 

The  External  Iliac  Artery 818 

Practical  Considerations S19 

Branches  of  External  Iliac  Artery. .  .  820 

The  Femoral  Artery S21 

Practical  Considerations 824 

Branches  of  Femoral  Artery 826 

Anastomoses  of  Femoral  Artery  ...  831 

The  Popliteal  Artery 831 

Practical  Considerations S32 

Branches  of  Popliteal  Artery S33 

The  Posterior  Tibial  Artery 835 

Practical  Considerations 836 

Branches  of  Posterior  Tibial  Artery.  83S 

The  Anterior  Tibial  Artery S42 

Practical  Considerations S42 

Branches  of  Anterior  Tibial  Artery,  844 

The  Dorsal  Artery  of  the  Foot 845 

Development  of  the  Arteries 846 

The  Veins 850 

General  Characteristics 850 

Classification 852 


The  Pulmonary  System 852 

The  Pulmonary  Veins 852 

The  Cardinal  System 854 

The  Cardiac  Veins 854 

The  Superior  Caval  System 857 

Vena  Cava  Superior 857 

Practical  Considerations 858 

The  Innominate  Veins 858 

Practical  Considerations 859 

Tributaries  of  Innominate  Veins  .  . .'.  859 

The  Internal  ]  ugular  Vein 861 

Practical  Considerations 863 

Tributaries  of  Internal  Jugular  Vein.  863 

The  Sinuses  of  the  Dura  Mater 867 

Practical  Considerations 869 

The  Diploic  Veins 874 

Practical  Considerations. 875 

The  Emissary  Veins 875 

Practical  Considerations 876 

The  Cerebral  Veins 877 

Practical  Considerations 878 

The  Ophthalmic  Veins 879 

Practical  Considerations 880 

The  External  Jugular  Vein 880 

Practical  Considerations 881 

Tributaries  of  External  Jugular  Vein  882 

The  Subclavian  Vein 884 

Practical  Considerations 885 

Veins  of  the  Upper  Limb 886 

The  Deep  Veins 886. 

The  Superficial  Veins 889 

Practical  Considerations 891 

The  Azygos  System 893 

The  Azygos  Vein 893 

Tributaries 893 

Practical  Considerations 895 

The   Hemiazygos   Vein 895 

The  Accessory  Hemiazygos  Vein.  .  S95 

The  Intercostal  Veins 896 

The  Spinal  Veins 897 

Practical  Considerations 898 

The  Veins  of  the  Spinal  Cord S9S 

The  Inferior  Caval  System 898 

Vena  Cava  Inferior 899 

Practical  Considerations 900 

Tributaries  of  Inferior  Cava.  ..  .  901 

Practical  Considerations. .  .  904 

The  Common  Iliac  Veins 905 

The  Internal  Iliac  Veins 905 

Tributaries  of  Internal  Iliac  .  . .  .  905 

The  External  Iliac  Vein 909 

Tributaries  of  External  Iliac.  . .  .  909 

The  Veins  of  the  Lower  Limb 910 

The  Deep  Veins 910 

The  Superficial  Veins 914 

Practical   Considerations  of  Iliac  Veins 

and  Veins  of  Lower  Limb 917 

The  Portal  System 919 

The  Portal  Vein 919 

Tributaries  of  Portal  Vein 920 

Practical  Considerations 925 

Development  of  the  Veins 926 

The  Fcetal  Circulation 929 

The  Lymphatic  System. 

General  Consideration 931 

Lymph-Spaces 931 

Lymph-Capillaries 933 

Lymph-Vessels 93^ 

Lymph-Nodes 935 

Structure  of  Lymphoid  Tissue 936 

Development  of  Lymphatic  Vessels  and 

Tissues 939 


CONTENTS. 


The  Thoracic  Duct 941 

Practical  Considerations 944 

The  Right  Lymphatic  Duct 945 

The  Lymphatics  of  the  Head 945 

The  Lymph-Nodes 945 

The  Lymph-Vessels 949 

Practical  Considerations 955 

The  Lymphatics  of  the  Neck 957 

The  Lymph-Nodes 957 

The  Lymph-Vessels 958 

Practical  Considerations 959 

The  Lymphatics  of  the  Upper  Limb  ....  961 

The  Lymph-Nodes 961 

The  Lymph-Vessels 963 

Practical  Considerations 965 


PAGE 

The  Lymphatics  of  the  Thorax 966 

The  Lymph-Nodes 966 

The  Lymph- Vessels 96S 

Practical  Considerations 971 

The  Lymphatics  of  the  Abdomen 972 

The  Lymph-Nodes 972 

The  Lymph-Vessels 976 

The  Lymphatics  of  the  Pelvis 983 

The  Lymph-Nodes 983 

The  Lymph -Vessels 984 

Practical  Considerations 990 

The  Lymphatics  of  the  Lower  Limb  ....  991 

The  Lymph-Nodes 991 

The  Lymph-Vessels 993 

Practical  Considerations 994 


VOLUME 


GENERAL   CONSIDERATIONS 

THE  CELL  EARLY  DEVELOPMENT  THE  ELEMENTARY  TISSUES 

THE   SKELETON 

THE  BONES  THE  ARTICULATIONS 

THE   MUSCULAR   SYSTEM 
THE   VASCULAR   SYSTEM 

THE  HEART  THE  ARTERIES  THE  VEINS 

THE  LYMPHATICS 


HUMAN   ANATOMY. 


Anatomy  is  that  subdivision  of  morphology — the  science  of  form  as  contrasted 
with  that  of  function  or  physiology — which  pertains  to  the  form  and  the  structure  of 
organized  beings,  vegetal  or  animal.  Phytotomy  and  Zootomy,  the  technical  names 
for  vegetal  and  animal  anatomy  respectively,  both  imply  etymologically  the  dissocia- 
tion, or  the  cutting  apart,  necessary  for  the  investigation  of  plants  and  animals. 

The  study  of  organized  bodies  may  be  approached,  evidently,  from  several  stand- 
points. When  the  details  of  the  structure  of  their  various  tissues  and  organs  par- 
ticularly is  investigated,  such  study  constitutes  General  Anatomy  or  Histology,  fre- 
quently also  called  Microscopical  Anatomy,  from  the  fact  that  the  magnifying  lens  is 
used  to  assist  in  these  examinations.  The  advantages  of  comparing  the  organization 
of  various  animals,  representing  widely  different  types  as  well  as  those  closely  related, 
are  so  manifest  in  arriving  at  a  true  estimate  of  the  importance  and  significance  of 
structural  details,  that  Comparative  Anatomy  constitutes  a  department  of  biological 
science  of  far-reaching  interest,  not  merely  for  the  morphologist,  but  likewise  for 
the  student  of  human  anatomy,  since  we  are  indebted  to  comparative  anatomy  for 
an  intelligent  conception  of  many  details  encountered  in  the  human  body.  Devel- 
opmental  Anatomy,  or  Embryology,  also  has  been  of  great  service  in  advancing  our 
understanding  of  numerous  problems  connected  with  the  adult  organism  by  tracing 
the  connection  between  the  complex  relations  of  the  completed  structures  and  their 
primitive  condition,  as  shown  by  the  sequence  of  the  phases  of  development.  These 
three  departments  of  anatomical  study — general,  comparative,  and  developmental 
anatomy — represent  the  broader  aspects  of  anatomical  study  in  which  the  features 
of  the  .human  body  are  only  incidents  in  the  more  extended  contemplation  of 
organized  beings. 

The  exceptional  importance  of  an  accurate  knowledge  of  the  body  of  man  has 
directed  to  human  anatomy,  or  a7ithropotomy ,  so  much  attention  from  various  points 
of  view  that  certain  subdivisions  of  the  subject  are  conveniently  recognized  ;  thus, 
the  systematic  account  of  the  human  body  is  termed  Descriptive  Anatomy,  while 
when  the  mutual  relations  and  peculiarities  of  situation  of  the  organs  located  in  par- 
ticular parts  of  the  body  especially  claim  attention,  such  study  is  spoken  of  as  Topo- 
graphical or  Regional  Anatomy.  Consideration  of  the  important  group  of  anatomi- 
cal facts  directly  applicable  to  the  diagnosis  and  the  treatment  of  disease  constitutes 
Applied  Anatomy. 

General  Plan  of  Construction. — Vertebrate  animals,  of  which  man  rep- 
resents the  most  conspicuous  development  of  the  highest  class,  — fishes,  amphibians, 
reptiles,  birds,  and  mammals  being  the  recognized  subdivisions  of  the  vertebrata, — 
possess  certain  characteristics  in  common  which  suffice  to  distinguish  the  numerous 
and  varied  members  of  the  extended  group. 

The  fundamental  anatomical  feature  of  these  animals  is  the  possession  of  an 
axial  column,  or  spine,  which  extends  from  the  anterior  or  cephalic  to  the  poste- 
rior or  caudal  pole  and  establishes  an  axis  around  which  the  various  parts  of  the 
elongated  body  are  grouped  with  more  or  less  symmetry.  While  this  body-axis  is 
usually  marked  by  a  series  of  well-defined  osseous  segments  constituting  the  ver- 
tebralcolumn  of  the  higher  animals,  among  certain  of  the  lower  fishes,  as  the  sharks 
or  sturgeons,  the  axial  rod  is  represented  by  cartilaginous  pieces  alone  ;  in  fact,  the 
tendency  towards  the  production  of  a  body-axis  is  so  pronounced  that  the  formation 


2  HUMAN  ANATOMY. 

of  a  primitive  axis,  the  notochord,  takes  place  among  the  early  formative  processes-  oi 
the  embryo. 

In  addition  to  the  fundamental  longitudinal  axis,  vertebrate  animals  exhibit  a 
transverse  cleavage  into  somatic  or  body-segments.  While  such  segmentation  is  rep- 
resented in  the  maturer  conditions  by  the  series  of  vertebrae  and  the  associated  ribs, 
the  tendency  to  this  division  of  the  body  is  most  marked  in  the  early  embryo,  in 
which  the  formation  of  body-segments,  the  somites,  takes  place  as  one  of  the  primary 
developmental  processes.  Although  these  primary  segments  do  not  directly  corre- 
spond to  the  permanent  vertebrae,  they  are  actively  concerned  in  the  formation  of 
the  latter  as  well  as  the  segmental  masses  of  the  earliest  muscular  tissue.  In  man 
not  only  the  skeleton,  but  likewise  the  muscular,  vascular,  and  nervous  systems  are 
affected  by  this  segmentation,  the  effects  of  which,  however  are  most  evident  in  the 
structure  of  the  walls  of  the  thoracic  portion  of  the  body-cavity. 

Disregarding  the  many  variations  in  the  details  of  arrangement  brought  about 
by  specialization  and  adaptation,  the  body  of  every  vertebrate  animal  exhibits  a 
fundamental  plan  of  construction  in  which  bilateral  symmetry  is  a  conspicuous  fea- 
ture.    Viewed  in  a  transverse  section  passing  through  the  trunk,  the  animal  body- 


Neural  arch  — 
Neural  tube 
Spinal  cord 

Vertebral  a 


Parietal  mesoblast 


Costal  segment 
Parietal  mesoblast 


Aorta 

Parietal  mesothelium 
Visceral  mesothelium 
Entoblastic  epithelium 
Subepithelial  mesoblast 
Visceral  mesoblast 


Diagrammatic  plan  of  vertebrate  body  in  transverse  section.     {Modified from  Wiedersheim.") 

may  be  regarded  as  composed  primarily  of  the  axis,  formed  by  the  bodies  of  the 
vertebras,  and  two  tubular  cavities  of  very  unequal  size  enclosed  by  the  tissues  con- 
stituting the  body-walls  and  invested  externally  by  the  integument  (Fig.  i). 

The  smaller  of  these,  the  neural  tube,  is  situated  dorsally,  and  is  formed  by  the 
series  of  the  vertebral  arches  and  associated  ligaments  ;  it  surrounds  and  protects 
the  great  cerebro-spinal  axis  composed  of  the  spinal  cord  and  the  specialized  cephalic 
extremity,  the  brain.  The  larger  space,  the  visceral  tube  corresponding  to  the  body- 
cavity,  or  ceelom,  lies  on  the  ventral  side  of  the  axis  and  contains  the  thoracic  and 
abdominal  viscera,  including  the  more  or  less  convoluted  digestive-tube  with  its 
accessory  glandular  organs,  the  liver  and  the  pancreas,  and  the  appended  respiratory 
tract,  together  with  the  genito-urinary  organs  and  the  vascular  and  lymphatic  appa- 
ratus. 

The  digestive-tube,  which  begins  anteriorly  at  the  oral  orifice  and  opens 
posteriorly  by  the  anus,  is  extended  by  two  ventral  evaginations  giving  rise  to  the 
respiratory  tract  and  the  liver,  a  dorsal  glandular  outgrowth  representing  the  pan- 
creas. The  sexual  and  urinary  glands  and  their  ducts  primarily  occupy  the  dorsal 
wall  of  the  body  cavity.  The  vascular  system  consists  essentially  of  the  ventrally 
placed  contracting  dilatation,  the  heart,  divided  into  a  venous  and  an  arterial  com- 


DESCRIPTIVE   TERMS. 


partment,  and  the  great  arterial  trunk,  the  aorta,  the  major  part  of  which  occupies 
the  dorsal  wall  of  the  space. 

The  elongated  typical  vertebrate  body  terminates  anteriorly  in  the  cephalic 
segment,  posteriorly  in  the  caudal  appendage  ;  between  these  two  poles  extends  the 
trunk,  from  which  project  the  ventrally  directed  limbs,  when  these  appendages  exist. 
Just  as  the  axial  segments,  represented  by  the  bodies  of  the  vertebra;,  take  part, 
in  conjunction  with  the  neural  arches,  in  the  formation  of  the  neural  canal,  so  do  these 
segments  also  aid  in  forming  the  supporting  framework  of  the  ventral  body-cavity 
in  connection  with  the  series  of  ribs  and  the  sternum. 

Descriptive  Terms. — The  three  chief  planes  of  the  vertebrate  body  are  the 
sagittal,  the  transverse,  and  the  frontal.  The  sagittal  plane,  when  central,  passes 
through  the  long  axis  of  the  body  vertically  and  bisects  the  ventral  or  anterior  and 
the  dorsal  or  posterior  surfaces.  The  transverse  plane  passes  through  the  body 
at  right  angles  to  its  long  axis  and  to  the  sagittal  plane.  The  frontal  plane  passes 
vertically  but  parallel  to  the  anterior  or  ventral  surface,  being  at  right  angles  to  both 
the  sagittal  and  transverse  planes  (Fig.  -2.  ) 

The  vertical  position  of  the  long  axis  in  the  human  body  is  unique,  since  man, 


Fig.  2. 


Fig.  3. 


Human  embryo  showing  primary  relations  of 
limbs,  a,  a,  preaxial  surfaces;  bt  b,  postaxial ; 
j,  j,  somitic  segments  of  trunk. 


Three  principal  planes  of   human  body.      T,  T, 
transverse  ;  .5",  5,  sagittal ;  F,  F,  frontal. 


of  all  animals,  is  capable  of  habitually  maintaining  the  erect  posture  with  full  exten- 
sion of  the  supporting  extremities.  The  lack  of  correspondence  between  the  actual 
position  of  the  chief  axis  of  man  and  the  horizontal  fore-and-aft  axis  of  vertebrates 
in  general  results  in  discrepancies  when  the  three  principal  planes  of  the  human 
body  are  compared  with  those  of  other  animals.  Thus,  the  sagittal  plane  alone 
retains  the  relation,  as  being  at  right  angles  to  the  plane  of  the  support,  in  all  verte- 
brates, although  in  man  its  greatest  expansion  is  vertical.  The  transverse  plane  in 
man  is  parallel  with  the  supporting  surface,  while  it  is,  obviously,  at  right  angles 
to  the  corresponding  plane  in  the  four-footed  vertebrate  ;  likewise,  the  frontal  plane 
in  man  is  vertical,  while  it  is  horizontal  in  other  animals. 

The  various  terms  employed  in  describing  the  actual  position  of  the  numerous 
parts  of  the  human  body  and  their  relations  to  surrounding  structures  have  been 
adopted  with  regard  to  the  erect  attitude  of  man  and  the  convenience  of  the  student 
of  human  anatomy  ;  hence,  in  many  cases,  they  must  be  recognized  as  having  a 
limited  specific  and  technical  application  and  often  not  directly  applicable  to  other 


4  HUMAN   ANATOMY. 

vertebrates.  Superior  and  inferior,  tipper  and  lower,  as  indicating  relations  towards 
or  away  from  the  head-end  of  the  body,  are,  probably,  too  convenient  and  useful  as 
expressing  the  peculiar  relations  in  man  to  be  readily  relinquished,  although  when 
directly  applied  to  animals  possessing  a  horizontal  body-axis  they  refer  entirely  to 
relations  with  the  plane  of  support,  the  additional  terms  cephalic  and  caudal  being 
necessary  to  indicate  relations  with  the  head- and  tail-pole.  Likewise,  "anterior" 
and  "posterior,"  as  referring  respectively  to  the  front  and  back  surfaces  of  the 
human  body,  are  more  logically  described  as  ventral  and  dorsal,  with  the  advantage 
that  these  terms  are  directly  applicable  to  all  vertebrates.  ' '  Outer' '  and  ' '  inner, ' '  as 
expressing  relations  with  the  sagittal  plane,  are  now  largely  replaced  by  the  more 
desirable  terms  lateral  and  mesial  respectively,  external  and  internal  being  reserved 
to  indicate  relations  of  depth.  Cephalic  and  caudal,  central  and  peripheral,  prox- 
imal and  distal,  are  all  terms  which  have  found  extensive  use  in  human  anatomy. 

Preaxial  and  postaxial,  in  addition  to  their  general  and  obvious  significance 
with  reference  to  axes  in  common,  have  acquired  a  specific  meaning  with  regard  to 
the  limbs,  the  appreciation  of  which  requires  consideration  of  the  primary  relations 
observed  in  the  embryo.  In  the  earliest  stage  the  limbs  appear  as  flattened  buds 
which  project  from  the  side  of  the  trunk  and  present  a  dorsal  and  ventral  surface  ; 
subsequently  the  limbs  become  folded  against  the  body,  the  free  ends  being  directed 
ventrally,  while  one  border  looks  headward,  the  other  tailward.  If  an  axis  corre- 
sponding to  the  transverse  plane  of  the  body  be  drawn  through  the  length  of  the 
extremities,  each  limb  will  be  divided  into  two  regions,  one  of  which  lies  in  front  of 
the  axis,  and  is,  therefore,  preaxial,  the  other  behind,  or  postaxial.  On  reference  to 
Fig.  3  it  is  obvious  that  the  preaxial  border  or  surface  of  each  limb  is  primarily 
directed  towards  the  cephalic  or  head-end  of  the  animal,  and,  conversely,  that  the 
postaxial  faces  the  caudal  or  tail-end.  These  fundamental  relations  are  of  great  im- 
portance in  comparing  the  skeleton  of  the  upper  and  lower  extremities  with  a  view 
of  determining  the  morphological  correspondence  of  the  several  component  bones, 
since  the  primary  relations  become  masked  in  consequence  of  the  secondary  dis- 
placements which  the  limbs  undergo  during  their  development. 

The  terms  homologue  and  analogue  call  for  a  passing  notice,  since  an  exact 
understanding  of  their  significance  is  important.  Structures  or  parts  are  homologous 
when  they  possess  identical  morphological  values  founded  on  a  common  origin  ;  thus, 
the  arm  of  a  man,  the  front  leg  of  a  dog,  and  the  wing  of  a  bat  are  homologues,  because 
each  represents  the  fore-limb  of  a  vertebrate,  although  they  differ  in  individual  func- 
tion. On  the  other  hand,  the  wing  of  a  bat  and  that  of  a  butterfly  are  analogous, 
since  they  are  structures  of  functional  similarity,  although  of  wide  morphological 
diversity.  Homologue,  therefore,  implies  structural  identity,  analogue  implies 
functional  similarity.  Parts  are  said  to  be  homotypes  when  they  are  serial  homo- 
logues ;  thus,  the  humerus  and  the  femur  are  homotypes,  being  corresponding 
structures  repeated  in  the  same  animal.  Where  parts  possess  both  morphological 
and  functional  identity,  as  the  wing  of  a  bird  and  of  a  bat,  they  are  analogous  as  well 
as  homologous. 


THE   ELEMENTS   OF  STRUCTURE. 

When  critically  examined,  the  various  organs  and  parts  going  to  make  up  the 
complex  economy  of  the  most  highly  specialized  vertebrate — and,  indeed,  the  same 
is  true  of  all  animals  whose  organization  does  not  approach  the  extremely  simple  uni- 
cellular type — are  found  to  be  constituted  by  the  various  combinations  of  a  very 
small  number  of  elementary  tissues ;  these  latter  may  be  divided  into  four  funda- 
mental groups  : 

Epithelial  tissues  ; 

Connective  tissues  ;    ■ 

Muscular  tissues  ; 

Nervous  tissues. 

Of  these  the  nervous  tissues  are  most  specialized  in  their  distribution,  while  the 
connective  tissues  are  universally  present,  in  one  or  another  form  contributing  to  the 
composition  of  every  organ  and  part  of  the  body.  The  tissues  of  the  circulatory 
system,  including  the  walls  of  the  blood-vessels  and  lymph-channels  and  the  corpus- 
cular elements  of  their  contained  fluids,  the  blood  and  the  lymph,  represent  special- 
izations of  the  connective  tissues  of  such  importance  that  they  are  often  conceded 
the  dignity  of  being  classed  as  independent  tissues  ;  consideration  of  the  develop- 
ment of  the  vascular  tissues,  however,  shows  their  genetic  relations  to  be  so  nearly 
identical  with  those  of  the  great  connective-tissue  group  that  a  separation  from  the 
latter  seems  undesirable. 

Each  of  the  elementary  tissues  may  be  resolved  into  its  component  morphologi- 
cal constituents,  the  cells  and  the  intercellular  substances.     The  first  of  these  are  the 


Fig.  4. 


Nucleus    Vacuole 


B 

Nucle 


Pseudopod 


Exoplasm 
A,  unicellular  animal  {amoeba) ;  B.  embryonal  cell, — leucocyte. 


descendants  of  the  embryonal  elements  derived  from  the  division  or  segmentation  of 
the  parent  cell,  the  ovum,  and  are  highly  endowed  with  vital  activity  ;  the  intercellu- 
lar substances,  on  the  other  hand,  represent  secondary  productions,  comparatively 
inert,  since  they  are  formed  through  the  more  or  less  direct  agency  of  the  cells.  The 
animal  cell  may  exist  in  either  the  embryonal,  matured,  or  metamorphosed  condition. 
The  embryonal  cell,  as  represented  by  the  early  generations  of  the  direct  off- 
spring of  the  ovum,  or  by  the  lymphoid  cells  or  colorless  blood-corpuscles  of  the 
adult,  consists  of  a  small,  irregularly  round  or  oval  mass  of  finely  granular  gelati- 
nous substance — the  protoplasm — in  which  a  smaller  and  often  indistinct  spherical 
body — the  nucleus — lies  embedded.  In  the  embryonal  condition,  when  the  cell  is 
without  a  limiting  membrane,  and  composed  almost  entirely  of  active  living  matter, 
the  outlines  are  frequently  undergoing  change,  these  variations  in  shape  being  known 
as  amceboid  movements ;  from  their  similarity  to  the  changes  observed  in  the  outline 
of  an  active  amoeba,  the  representative  of  the  simplest  form  of  animal  life,  in  which 

5 


6  HUMAN  ANATOMY. 

the  single  cell  constitutes  the  entire  organism,  and  as  such  is  capable  of  performing 
the  functions  essential  for  the  life-cycle  of  the  animal. 

As  the  embryonal  cell  advances  in  its  life-history,  the  conditions  to  which  it  is 
subjected  induce,  with  few  exceptions,  further  specializations,  since  in  all  but  the 
lowest  forms  division  of  labor  is  associated  with  a  corresponding  differentiation  and 
adaptation  to  specific  function. 

Vital  manifestations  of  the  cell  include  those  complex  physico-chemical 
phenomena  which  are  exhibited  during  the  life  of  the  cellular  constituents  of  the 
body  in  the  performance  of  the  functions  necessary  for  fulfilment  of  their  appointed 
life-work.      These  embrace  metabolism,  growth,  reproduction,  and  irritability. 

Metabolism,  the  most  distinctive  characteristic  of  living  matter,  is  that  process 
by  which  protoplasm  selects  from  the  heterogeneous  materials  of  food  those  partic- 
ular substances  suitable  for  its  nutrition  and  converts  them  into  part  of  its  own  sub- 
stance. Metabolism  is  of  two  forms, — constructive  and  destructive.  Constructive 
metabolism,  or  anabolism,  is  the  process  by  which  the  cell  converts  the  simpler  com- 
pounds into  organic  substances  of  great  chemical  complexity;  destructive  metabolism, 
or  katabolism,  on  the  contrary,  is  the  process  by  which  protoplasm  breaks  up  the 
complex  substances  resulting  from  constructive  metabolism  into  simpler  compounds. . 
Vegetal  cells  possess  the  power  of  constructive  metabolism  in  a  conspicuous  degree, 
and  from  the  simpler  substances,  such  as  water,  carbon  dioxide,  and  inorganic  salts, 
prepare  food-material  for  the  nutritive  and  katabolic  processes  which  especially  dis- 
tinguish the  animal  cell,  since  the  latter  is  dependent,  directly  or  indirectly,  upon 
the  vegetal  cell  for  the  materials  for  its  nutrition. 

Growth,  the  natural  sequel  of  the  nutritive  changes  effected  by  metabolism, 
may  be  unrestricted  and  equal  in  all  directions,  resulting  in  the  uniform  expansion 
of  the  cell,  as  illustrated  in  the  growth  of  the  ovum  in  attaining  its  mature  condition. 
Such  unrestricted  increase,  however,  is  exceptional,  since  cells  are  usually  more  or 
less  intimately  related  to  other  structural  elements  by  which  their  increase  is  modi- 
fied so  as  to  be  limited  to  certain  directions ;  such  limitation  and  influence  result  in 
unequal  growth,  a  force  of  great  potency  in  bringing  about  the  differentiation  and 
specialization  of  cells,  and,  secondarily,  of  entire  parts  and  organs  of  the  body. 
Familiar  examples  of  the  result  of  unequal  growth  are  observed  in  the  columnar 
elements  of  epithelium,  the  fibres  of  muscular  tissue,  and  the  neurones  of  the  ner- 
vous system. 

Reproduction  may  be  regarded  as  the  culminating  vital  manifestation  in  the 
vegetative  life-cycle  of  the  cell,  since  by  this  process  the  parent  element  surrenders 
its  individuality  and  continues  its  life  in  the  existence  of  its  offspring.  While  the 
details  of  the  process  by  which  new  cells  arise  from  pre-existing  cells  are  reserved  for 
consideration  in  connection  with  the  more  extended  discussion  of  the  cell  to  follow 
(see  page  9),  it  may  here  be  stated  that  reproduction  occurs  by  two  methods, — 
the  indirect  or  mitotic  and  the  direct  or  amitotic.  The  first  of  these,  involving  the 
complicated  cycle  of  nuclear  changes  collectively  known  as  mitosis  or  karyokinesis, 
is  the  usual  method ;  the  second  and  simpler  process  of  direct  division,  or  amitosis, 
is  now  recognized  as  exceptional  and  frequently  associated  with  conditions  of  im- 
paired vital  vigor. 

Irritability  is  that  property  of  living  matter  by  virtue  of  which  the  cell  ex- 
hibits changes  in  its  form  and  intimate  constitution  in  response  to  external  impres- 
sions. These  latter  may  originate  in  mechanical,  thermal,  electrical,  or  chemical 
stimuli  to  which  the  protoplasm  of  even  the  lowest  organisms  responds,  or  they  may 
be  produced  in  consequence  of  the  obscure  and  subtle  changes  occurring  within  the 
protoplasm  of  neighboring  elements,  as  illustrated  by  the  reaction  of  the  neurones  in 
response  to  the  stimuli  transmitted  from  other  nervous  elements. 

THE  ANIMAL  CELL. 

Ever  since  the  establishment  of  the  Cell  Doctrine,  in  1838,  by  the  announcement 
of  the  results  of  the  epoch-making  investigations  of  Schleiden  and  Schwann  on  "The 
Accordance  of  Structure  and  Growth  of  Animals  and  Plants,"  the  critical  examination 
of  the  cell  has  been  a  subject  of  continuous  study.     Notwithstanding  the  tireless  enthu- 


STRUCTURE   OF  THE   CELL.  7 

siasm  with  which  these  researches  have  been  pursued  by  the  most  competent  investi- 
gators and  the  great  advance  in  our  accurate  knowledge  concerning  the  intricate 
problems  relating  to  the  morphology  and  the  physiology  of  the  cell,  much  pertaining 
to  the  details  of  the  structure  and  the  life  of  the  cell  still  remains  uncertain,  and  must 
be  left  to  the  future  achievements  in  cytology.  The  account  here  given  of  the  mor- 
phology of  the  cell  presents  only  those  fundamental  facts  which  at  the  present  time 
may  be  accepted  as  established  upon  the  evidence  adduced  by  the  most  trustworthy 
observers.  The  more  speculative  and  still  unsettled  and  disputed  problems  of  cy- 
tology, interesting  as  such  theoretical  considerations  may  be,  lie  beyond  the  purpose 
of  these  pages  ;  for  such  discussions  the  student  is  referred  to  the  special  works  and 
monographs  devoted  to  these  subjects.  An  appreciation,  however,  of  the  salient 
facts  of  cytology  as  established  by  the  histologists  of  the  present  generation  is  essen- 
tial not  only  for  an  intelligent  conception  of  the  structure  of  the  morphological  ele- 
ments, but  likewise  for  the  comprehension  of  the  highly  suggestive  modern  theories 
concerning  inheritance,  since,  as  will  appear  in  a  later  section,  the  present  views 
regarding  these  highly  interesting  problems  are  based  upon  definite  anatomical 
details. 

Fig.  5. 


Exoplasm 


Cytoplasm 


Nuclear  membrane 
Nucleolus 


Metaplastic  inclusions 


Diagram  of  cell-structu 


Centrosome  surrounded  by 
trosphere 


Notwithstanding  the  great  variations  in  the  details  of  form  and  structure,  cells 
possess  a  common  type  of  organization  in  which  the  presence  of  the  cell-body  or  cyto- 
plasm and  the  nucleus  is  essential  in  fulfilling  the  modern  conception  of  a  cell.  The 
latter  may  be  defined,  therefore,  as  a  nucleated  mass  of  protoplasm. 

The  term  protoplasm,  as  now  generally  employed  by  histologists,  signifies  the 
organized  substance  composing  the  entire  cell,  and  with  this  application  includes 
both  the  cytoplasm  and  the  nucleus. 

Structure  of  the  Cytoplasm. — The  cytoplasm,  or  the  substance  of  the  cell- 
body,  by  no  means  invariably  presents  the  same  appearance,  since  it  may  be  regarded 
as  established  that  the  constituents  of  this  portion  of  the  cell  are  subject  to  changes  in 
their  condition  and  arrangement  which  produce  corresponding  morphological  varia- 
tions ;  thus,  the  cytoplasm  may  be  devoid  of  definite  structure  and  appear  homoge- 
neous ;  at  other  times  it  may  be  composed  of  aggregations  of  minute  spherical  masses 
and  then  be  described  as  gratiular,  or,  where  the  minute  spheres  are  larger  and  con- 
sist of  fluid  substances  embedded  within  the  surrounding  denser  material  of  the  cell, 
as  alveolar ;  or,  again,  and  most  frequently,  the  cytoplasm  contains  a  mesh- work  of 
fibrils,  more  or  less  conspicuous,  which  arrangement  gives  rise  to  the  7'eticular  con- 
dition. The  recognition  of  the  fact  established  by  recent  advances  in  cytology,  that 
the  structure  of  cytoplasm  is  not  to  be  regarded  as  immutable,  but,  on  the  contrary, 
as  capable  of  undergoing  changes  which  render  it  probable  that  a  cell  may  appear 


8  HUMAN   ANATOMY. 

during  one  stage  of  its  existence  as  granular  and  at  a  later  period  as  reticular,  has 
done  much  to  bring  into  accord  the  conflicting  and  seemingly  irreconcilable  views 
regarding  the  structure  of  the  cell  championed  by  competent  authorities. 

Whatever  be  the  particular  phase  of  structural  arrangement  exhibited  by  the 
cell,  histologists  are  agreed  that  the  cytoplasm  consists  of  two  substances, — an  active 
and  a  passive  ;  while  both  must  be  regarded  as  living,  the  vital  manifestations  of  con- 
tractility are  produced  by  the  former. 

Since  a  more  or  less  pronounced  reticular  arrangement  of  the  active  and  passive 
constituents  of  cytoplasm  is  of  wide  occurrence  in  mature  cells,  this  condition  may 
serve  as  the  basis  for  the  description  of  the  morphology  of  the  typical  cell. 

Critical  examination  of  many  cells,  especially  the  more  highly  differentiated 
forms  of  glandular  epithelium,  shows  the  cytoplasm  to  contain  a  mesh-work  com- 
posed of  delicate  fibrils  and  septa  of  the  more  active  substance,  the  spongioplasm ; 
although  conspicuous  after  appropriate  staining,  the  spongioplastic  net-work  may  be 
seen  in  the  unstained  and  living  cell,  thereby  proving  that  such  structural  details  are 
not  artefacts  due  to  the  action  of  reagents  upon  the  albuminous  substances  com- 
posing the  protoplasm. 

The  interstices  of  the  mesh-work  are  filled  with  a  clear  homogeneous  semifluid 
material  to  which  the  name  of  hyaloplasm  has  been  applied.  Embedded  within  the 
hyaloplasm,   a  variable  amount  of    foreign  substances  is  frequently  present ;    these 


Spermatogenic  cells,  showing  variations  in  the  condition  and  the  arrangement  of  the  constituents  of  the  cyto- 
plasm and  the  nucleus  ;  the  centrosomes  are  seen  within  the  cytoplasm  close  "to  the  nucleus.  A,  from  the  guinea-pig 
X  1685  (Meves) ;  B,  from  the  salamander  X  500  (Meves) ;  C  from  the  cat  X  750  (von  Lenhossek). 

include  particles  of  oil,  pigment,  secretory  products,  and  other  extraneous  materials, 
which,  while  possibly  of  importance  in  fulfilling  the  purposes  of  the  cell,  are  not  among 
its  essential  morphological  constituents.  These  substances,  which  are  inert  and  take 
no  part  in  the  vital  activity  of  the  cell,  are  termed  collectively  metaplasm. 

Cytoplasm  consists,  therefore,  morphologically,  of  the  spongioplasm  and  the 
hyaloplasm  ;  chemically,  cytoplasm  consists  of  certain  organic  compounds,  salts  and 
water.  The  organic  compounds  are  grouped  under  the  term  proteins,  which  are 
complex  combinations  of  carbon,  hydrogen,  nitrogen,  and  oxygen,  with  often  a  small 
percentage  of  sulphur.     The  proteins  of  the  cytoplasm  contain  little  or  no  phosphorus. 

Structure  of  the  Nucleus. — The  nucleus,  during  the  vegetative  condition  of 
the  cell,  or  the  "resting  stage,"  as  often  less  accurately  called,  appears  as  a  more 
or  less  spherical  body  whose  outline  is  sharply  defined  from  the  surrounding  cyto- 
plasm by  a  definite  envelope,  the  nuclear  7?iembra?ie.  Since  the  nucleus  is  the 
nutritive,  as  well  as  reproductive,  organ  of  the  cell,  the  fact  that  this  part  of  the  cell 
is  relatively  large  in  young  and  actively  growing  elements  is  readily  explained. 

The  nucleus  consists  of  two  parts,  an  irregular  reticulum  of  nuclear  jibi'es  and 
an  intervening  semifluid  nuclear  matrix,  therein  resembling  the  cytoplasm.  Exam- 
ined under  high  magnification,  after  appropriate  treatment  with  particular  stains,  such 
as  haematoxylin,  safranin,  and  other  basic  dyes,  the  nuclear  fibres  are  shown  to  be 
composed  of  minute  irregular  masses  of  a  deeply  colored  substance,  appropriately 


STRUCTURE   OF   THE   CELL.  9 

called  chromatin  in  recognition  of  its  great  affinity  for  certain  stains  ;  the  chromatin 
particles  are  supported  upon  or  within  delicate  inconspicuous  and  almost  colorless 
threads  of  linin.  The  latter,  therefore,  forms  the  supporting  net-work  of  the  nuclear 
fibrils  in  which  the  chromatin  is  so  prominent  by  virtue  of  its  capacity  for  staining. 
The  forms  of  the  individual  masses  of  chromatin  vary  greatly,  often  being  irregular, 
at  other  times  thread-like  or  beaded  in  appearance.  Not  infrequently  the  chromatin 
presents  spherical  aggregations  which  appear  as  deeply  stained  nodules  attached  to 
the  nuclear  fibres  ;  these  constitute  the  false  nucleoli,  or  karyosomes,  as  distinguished 
from  the  true  nucleolus  which  is  frequently  present  within  the  karyoplasm.  Chemi- 
cally, chromatin,  the  most  essential  part  of  the  nucleus,  contains  nuclein,  a  com- 
pound rich  in  phosphorus. 

The  matrix,  or  nuclear  juice,  which  occupies  the  interstices  of  the  net-work, 
possesses  an  exceedingly  weak  affinity  for  the  staining  reagents  employed  to  color 
the  chromatin,  and  usually  appears  clear  and  untinted.  It  is  probably  closely  related 
to  the  achromatin  and  contains  a  substance  described  as  paralinin. 

The  nucleolus,  or  plasmosome ;  ordinarily  appears  as  a  small  spherical  body — 
sometimes  multiple — lying  among,  but  unattached  to,  the  nuclear  fibres  ;  its  color  in 
stained  tissues  varies,  sometimes  resembling  that  of  the  chromatin,  although  less 
deeply  stained,  but  usually  presenting  a  distinct  difference  of  tint,  since  it  responds 
readily  to  dyes  which,  like  eosin  or  acid  fuchsin,  particularly  affect  the  linin  and 
cytoplasm.  Concerning  the  exact  nature,  purpose,  and  function  of  the  nucleolus 
much  uncertainty  still  exists  ;  according  to  certain  authorities,  these  bodies  are  to  be 
regarded  as  storehouses  of  substances  which  are  used  in  the  formation  of  the  chro- 
matin segments  during  division,  while  other  cytologists  attribute  to  the  nucleolus  a 
passive  role,  even  regarding  it  as  by-product  which,  at  least  in  some  cases,  is  cast  out 
from  the  nucleus  into  the  cytoplasm,  where  it  degenerates  and  disappears.  Since 
trustworthy  observations  may  be  cited  in  support  of  both  of  these  conflicting 
views,  definite  conclusions  regarding  the  exact  nature  of  this  constituent  of  the 
nucleus  must  be  deferred.  The  nucleolus  is  credited  with  containing  a  peculiar 
substance  known  as  pyrenin.  The  term  amphipyrenin,  as  applied  to  the  substance 
of  the  nuclear  membrane,  is  of  doubtful  value. 

The  Centrosome. — In  addition  to  the  parts  already  described,  which  are  con- 
spicuous and  readily  seen,  the  more  recent  investigations  into  the  structure  of  cells 
show  the  presence  of  a  minute  body,  the  cen- 
trosome,   which    plays    an    important   role    in  Fig.  7. 
elements   engaged   in   active  change,    as   con-       . ..  .  .  A 

spicuously    during   division    and,    in    a   lesser  ,._.••. 

degree,  during  other  phases  of  cellular  activity.  "" ""  ^^    ■£&  V^ 

Ordinarily  the    centrosome    escapes    attention  's,     ..    „;.<«.  ^r.%^     tt 

because,  on  account  of  its  minute  size  and  varia-       '  »J '»>,:'* j ■  ?;|.  j 
ble  staining  affinity,  it  is  with  difficulty  distin-  .^W^; 

guished  from   the  surrounding  particles.      Its  n 

usual  position  is  within  the  cytoplasm,  but  the  _  C  '•*-■'' <®k 

exact  location  of  the  centrosome  seems  to  de-  .'r-.—  <■. 

pend  upon  the  focus  of  greatest  motor  activity, 

since,    as    shown    by   Zimmermann,   this    little  '■"... 
body,  or  bodies,  being  often  double,  is  always        /£»!  0. 
found  in  that  part  of  the  cell  which  is  the  seat        w  |p                        . 
of  greatest  change  ;   thus,    in   a   dividing  ele- 
ment, the  centrosome  lies  immediately  related          _    ,  „ M  ,      .  .    .  ...  ,. 

'  -       ,         1  •  -i  •  1  •  Centrosomes   (c,  c)    in   human   epithelium ; 

tO   the   actively  Changing    nucleus,   while  Within  A,  B,  cells  from  gastric  glands;    C,  from  duo- 

m*    j.    j  '^i_    1*  "^    •  i  z  it-  denal  glands ;  Z>,  from  tongue ;  /,  leucocyte  with 

Ciliated    epithelium  It   IS   removea  from   the    nu-  centrolome  X  625.    (K.  W.  Zimmermann.) 

cleus  and  is  found  closely  associated  with  the 

contractile  filaments  which  probably  produce  the  movements  of  the  hair-like  ap- 
pendages. In  recognition  of  the  intimate  relations  between  this  minute  body  and  the 
active  motor  changes  affecting  the  morphological  constituents  of  the  cell,  the  cen- 
trosome may  be  regarded  physiologically  as  its  dynamic  centre  ;  the  name  kino- 
centrum  has  been  suggested  by  Zimmerman  as  best  expressing  this  probable 
function  of  the  centrosome.      This  little  body  is  frequently  surrounded  by  a  clear 


HUMAN    ANATOMY. 


area  or  halo,  the  centrosphere  or  the  attraction  sphere,  within  which  it  appears  as  a 
minute  speck,  frequently  being  double  instead  of  single. 

In  recapitulation,  the  chief  constituents  of  the  animal  cell  may  be  tabulated  as 
follows  : 

{Meshwork — Spongioplasm. 
Ground-substance — Hyaloplasm,  containing  inclusions,  Hfela- 
p/asm. 

f  Linin  fibrils. 
Protoplasm    \  f  Nuclear  reticulum  consisting  of    \  Chromatin   (containing  Nu- 

Centrosome  [      clein). 

Nuclear  matrix  (containing  Paralinin). 
Nucleus  -j  Nucleolus  (containing  Pyrenin.) 

I  I  Nuclear  membrane. 


DIVISION   OF  CELLS. 

Disregarding  for  the  present,  at  least,   the  occurrence  of    direct  fission  as  a 
means  of  producing  new  elements  observed  among  the  simplest  forms  of  animal  life, 


Diagram  of  mitosis.  A,  resting  stage,  chromatin  irregularly  distributed  in  nuclear  reticulum  ;  a,  centrosphere 
containing  double  centrosome;  w,  nucleolus.  B,  chromatin  arranged  as  close  spirem  ;  c,  c,  centrosomes  surrounded 
by  achromatic  radial  striations.  C,  stage  of  loose  spirem,  achromatic  figure  forming  amphiaster  (amp).  Z>,  chro- 
matin broken  into  chromosomes;  nucleolus  has  disappeared,  nuclear  membrane  fading;  amphiaster  consists  of  two 
asters  (a,  a)  surrounding  the  separating  centrosomes,  connected  by  the  spindle  (s).  E,  longitudinal  cleavage  of  the 
chromosomes  which  are  arranged  around  the  polar  field  (p)  occupied  by  the  spindle.  Et  migration  of  chromatic 
segments  towards  new  nuclei,  as  established  by  centrosomes  (c.  c) ;  ep,  equatorial  plate  formed  by  intermingling 
segments.  G,  separating  groups  of  daughter  chromosomes  id,  d)  united  by  connecting  threads  (c  t).  H.  daughter 
chromosomes  (d,  d)  becoming  arranged  around  daughter  centrosomes  which  have  already  divided  ;  C,  C,  beginning 
cleavage  of  cytoplasm  across  plane  of  equatorial  spindle.  I,  completed  daughter  nuclei  (D,  D)  ;  cytoplasm  almost 
divided  into  two  new  cells.     (Modified  from  Wilson). 


or  as  an  exceptional  method  among  effete  and  diseased  cells  of  the  higher  types,  the 
production   of  new  generations  of   cells  may  be   assumed  as  accomplished   for   all 


DIVISION   OF   CELLS.  n 

varieties  of  elements  by  a  complicated  series  of  changes,  collectively  known  as  kar- 
yokinesis,  or  mitosis,  especially  affecting  the  nucleus.  As  already  pointed  out,  in 
addition  to  presiding  over  the  nutritive  and  chemical  changes,  the  nucleus  is  par- 
ticularly concerned  in  the  process  of  reproduction  ;  further,  of  the  several  morpho- 
logical constituents  of  the  nucleus,  the  chromatin  displays  the  most  active  change, 
since  this  substance  is  the  vehicle  by  which  the  characteristics  of  the  parent  cell  are 
transmitted  to  the  new  elements.  So  essential  is  this  substance  for  the  perpetuation 
of  the  characteristics  of  each  specific  kind  of  cell  that  the  entire  complex  mitotic 
cycle  has  for  its  primary  purpose  the  insurance  of  the  equal  division  of  the  chroma- 
tin of  the  mother  cell  between  the  two  new  nuclei,  such  impartial  distribution  of  the 
chromatin  taking  place  irrespective  of  any,  or  even  very  great,  dissimilarity  in  the 
size  of  the  daughter  cells,  the  smaller  receiving  exactly  one-half  of  the  maternal 
chromatin. 

Mitotic   Division. — The  details  of  karyokinesis,   or  mitosis,  sometimes  also 
spoken  of  as  indirect  division,  include  a  series  of  changes  involving  the  centrosome, 


Sfflj 


// 


m 

J.  H5  X 


tr- 
i- 


chromatic figures  in  dividing  cells  from  epidermis  of  salamander  embryo.  X  960-  -4.  resting  stage:  B  close 
spireme  ;  C,  loose  spireme  ;  D.  chromosomos  ("  wreath  " ),  seen  frcm  surface  ;  E,  similar  stage,  seen  111  profile ;  F, 
longitudinal  cleavage  01  chromosomes  ;  G,  beginning  migration  of  segments  towards  centrosoines  ;  H,  separating 
groups  of  daughter  segments  ;  /,  daughter  groups  attracted  towards  poles  of  new  nuclei,  cytoplasm  exhibits  begin- 
ning cleavage. 


the  nucleus,  and  the  cytoplasm,  which  are  conveniently  grouped  into  four  stages  ; 
(1)  the  Prophases,  or  preparatory  changes;  (2)  the  Metaphase,  during  which  the 
chromatin  is  equally  divided;  (3)  the  Anaphases,  in  which  redistribution  of  the 
chromatin  is  accomplished  ;  (4)  the  Telophases,  during  which  the  cytoplasm  under- 
goes division  and  the  daughter  cells  are  completed. 


12  HUMAN   ANATOMY. 

In  anticipation  of  the  consideration  of  the  details  of  mitosis,  it  should  be  pointed 
out  that  the  process  includes  two  distinct,  but  intimately  associated  and  coinci- 
dent series  of  phenomena,  the  one  involving  the  chromatin,  the  other  the  centro- 
somes  and  the  linin.  While  as  a  matter  of  convenience  these  two  sets  of  changes  are 
described  separately,  it  must  be  understood  that  they  take  place  simultaneously  and 
in  coordination.  The  purpose  of  the  changes  affecting  the  chromatin  is  the  accu- 
rate and  equal  division  of  this  substance  by  the  longitudinal  cleavage  of  the  chroma- 
tin segments  ;  the  object  of  the  activity  of  the  centrosomes  and  the  linin  is  to  supply 
the  requisite  energy  and  to  produce  the  guiding  lines  by  which  the  chromatin 
segments  are  directed  to  the  new  nuclei,  each  daughter  cell  being  insured  in  this 
manner  one-half  of  the  maternal  chromatin. 

The  Prophases,  or  preparatory  stages,  include  a  series  of  changes  which 
involve  the  nuclear  substances  and  the  centrosomes  and  result  in  the  formation  of  the 
kary  o  kinetic  figure ;  the  latter  consists  of  two  parts,  (i)  the  deeply  staining  chro- 
matin filaments,  and  (2)  the  achromatic  figure,  which  colors  but  slightly  if  at  all. 
The  chromatin  loses  its  reticular  arrangement  and,  increasing  in  its  staining  affinities, 
becomes  transformed  into  a  closely  convoluted  thread  or  threads,  constituting  the 
"  close  skein  ;"  the  filaments  composing  the  latter  soon  shorten  and  thicken' to  form 
the  "  loose  skein."  The  skein,  or  spii'eme,  may  consist  of  a  single  continuous  fila- 
ment, or  it  may  be  formed  of  a  number  of  separate  threads.  Sooner  or  later  the 
skein  breaks  up  transversely  into  a  number  of  segments  or  chromosomes,  which  ap- 
pear as  deeply  staining  curved  or  straight  rods.  A  very  important,  as  well  as  remark- 
able, fact  regarding  the  chromosomes  is  their  numerical  constancy,  since  it  may  be 
regarded  as  established  that  every  species  of  animal  and  plant  possesses  a  fixed  and 
definite  number  of  chromosomes  which  appear  in  its  cells  ;  further,  that  in  all  the 
higher  forms  the  number  is  even,  in  man  being  probably  twenty-four.  During  these 
changes  affecting  the  chromatin  the  nucleolus,  or  plasmosome,  disappears,  and,  prob- 
ably, takes  no  active  part  in  the  karyokinesis  ;  the  nuclear  membrane  likewise  fades 
away  during  the  prophases,  the  nuclear  segments  now  lying  unenclosed  within  the 
cell,  in  which  the  cytoplasm  and  the  nuclear  matrix  become  continuous. 

Coincident  with  the  foregoing  changes,  the  centrosome,  which  by  this  time  has 
already  divided  into  two,  is  closely  associated  with  phenomena  which  include  the  ap- 
pearance of  a  delicate  radial  striation  within  the  cytoplasm  around  each  centrosome, 
thereby  producing  an  arrangement  which  results  in  the  formation  of  two  stars  or 
asters.  The  centrosomes  early  show  a  disposition  to  separate  towards  opposite  poles 
of  the  cell,  this  migration  resulting  in  a  corresponding  migration  of  the  asters.  In 
consequence  of  these  changes,  the  retreating  centrosomes  become  the  foci  of  two 
systems  of  radial  striation  which  meet  and  together  form  an  achromatic  figure  known 
as  the  amphiaster,  which  consists  of  the  two  asters  and  the  intervening  spindle. 
Notwithstanding  the  observations  which  tend  to  question  the  universal  importance 
of  the  centrosome  as  the  initiator  of  dynamic  change  within  the  cell,  as  held  by  Van 
Beneden  and  Boveri,  there  seems  to  be  little  doubt  that  the  centrosome  plays  an 
important  role  in  establishing  foci  towards  which  the  chromosomes  of  the  new  nuclei 
become  attracted. 

The  nuclear  spindle,  which  originates  as  part  of,  or  secondarily  from  the 
amphiaster,  often  occupies  the  periphery  of  the  nucleus,  whose  limiting  membrane  by 
this  time  has  probably  disappeared.  The  delicate  threads  of  linin  composing  the 
nuclear  spindle  lie  within  an  area,  the  polar  field,  around  which  the  chromosomes 
become  grouped.  The  chromosomes,  which  meanwhile  have  arisen  by  transverse 
division  of  the  chromatin  threads  composing  the  loose  skein,  appear  often  as 
V-shaped  segments,  the  closed  ends  of  the  loops  being  directed  towards  the  polar 
field  which  they  encircle.  Owing  to  this  disposition,  when  seen  from  the  broader 
surface,  the  chromosomes  constitute  a  ring-like  group,  sometimes  described  as  the 
mother  wreath  ;  the  same  segments,  when  viewed  in  profile,  appear  as  a  radiating 
group  of  .fibrils  known  as  the  mother  star  ;  the  apparent  differences,  therefore,  be- 
tween these  figures  depend  upon  the  point  of  view  and  not  upon  variations  in  the 
arrangement  of  the  fibres. 

The  Metaphase  includes  the  most  important  detail  of  karyokinesis, — namely, 
the  longitudinal  cleavage  of  the  chromosomes,  whereby  the  number  of  the  latter  is 


MITOTIC    DIVISION.  13 

doubled  and  the  chromatin  is  equally  divided.  This  division  is  the  first  step  towards 
the  actual  apportionment  of  the  chromatin  between  'the  new  nuclei,  each  of  which 
receives  exactly  one-half  of  the  chromatin,  irrespective  of  even  marked  inequality 
in  the  size  of  the  daughter  cells. 

Meanwhile  the  centrosomes  have  continued  to  separate  towards  the  opposite 
poles  of  the  cell,  where,  surrounded  by  their  attraction  spheres,  each  forms  the 
centre  of  the  astral  striation  that  marks  either  pole  of  the  amphiaster,  the  nuclear 
spindle  being  formed  by  the  junction  of  the  prolonged  and  opposing  striae.  The 
purpose  of  the  achromatic  figure  is  to  guide  the  longitudinally  divided  chromosomes 
towards  the  new  nuclei  during  the  succeeding  changes. 

The  Anaphases  accomplish  the  migration  of  the  chromosomes,  each  pair  of 
sister  segments  contributing  a  unit  to  each  of  the  two  groups  of  chromosomes  that 
are  passing  towards  the  poles  of  the  achromatic  spindle  ;  in  this  manner  each  new 
nucleus  receives  not  only  one-half  of  the  chromatin  of  the  mother  nucleus,  but  also 
the  same  number  of  chromosomes  that  originally  existed  within  the  mother  cell,  the 
numerical  constancy  of  the  particular  species  being  thus  maintained. 

Anticipating  their  passage  towards  the  poles  of  the  achromatic  figure,  the  mi- 
grating chromatic  segments,  attracted  by  the  linin  threads,  for  a  time  form  a  com- 
pact group  about  the  equator  of  the  spindle  known  as  the  equatorial  plate.  As  the 
receding  segments  pass  towards  their  respective  poles,  the  opposed  ends  of  the  sep- 
arating chromosomes  are  united  by  intervening  achromatic  threads,  the  connecting 
fibres.  Sometimes  the  latter  exhibit  a  linear  series  of  thickenings  known  as  the 
cell-plate  or  mid-body.  The  migration  of  the  chromosomes  establishes  the  essential 
features  of  the  division  of  the  nucleus,  since  the  subsequent  changes  are  only  repe- 
titions, in  inverse  order,  of  the  changes  already  noted. 

The  Telophases,  in  addition  to  the  final  stages  in  the  rearrangement  of  the 
chromatic  segments  of  the  new  nuclei,  including  the  appearance  of  the  daughter 
wreath,  the  daughter  skeins,  the  new  nuclear  membrane,  and  the  nucleolus,  witness 
the  participation  of  the  cytoplasm  in  the  formation  of  the  new  cells.  In  these  final 
stages  of  mitosis  the  cell-body  becomes  constricted  and  then  divides  into  two,  the 
plane  of  division  passing  through  the  equator  of  the  nuclear  spindle.  Each  of  the 
resulting  masses  of  cytoplasm  invests  a  new  nucleus  and  receives  one-half  of  the 
achromatic  figure  consisting  of  a  half-spindle  and  one  of  the  asters  with  a  centro- 
some.  The  new  cell,  now  possessing  all  the  constituents  of  the  parent  element, 
usually  acquires  the  morphological  characteristics  of  its  ancestor  and  passes  into  a 
condition  of  comparative  rest  until  called  upon,  in  its  turn,  to  enter  upon  the  com- 
plicated cycle  of  mitosis. 

MITOTIC   DIVISION. 

I.  Prophases. 

A.  Changes  within  the  nucleus  :   Chromatic  figure. 

Chromatin  loses  reticular  arrangement, 

Close  skein, 

Loose  skein, 

Disappearance  of  nucleolus, 

Division  of  skein  into  chromosomes, 

Arrangement  around  polar  field — mother  wreath, 

Disappearance  of  nuclear  membrane. 

B.  Changes  within  the  cytoplasm  :  Achromatic  figure. 

Division  of  centrosome, 

Appearance  of  asters, 

Migration  of  centrosomes, 

Appearance  of  spindle, 

Formation  of  amphiaster, 

Appearance  of  nuclear  spindle  and  polar  field. 

II.  Metaphase. 

Longitudinal  cleavage  of  chromosomes, 


i4  HUMAN    ANATOMY. 

III.  Anaphases. 

Rearrangement  of  chromosomes  into  two  groups, 
Migration  of  groups  towards  poles  of  amphiaster. 
Appearance  of  connecting  fibres  between  receding  groups, 
Construction  of  daughter  nuclei. 

IV.  Telophases. 

Constriction  of  cell-body  appears  at  right  angles  to  spindle, 

Chromosomes  rearranged  in  daughter  nuclei  to  form  skeins, 

Reappearance  of  nuclear  membrane, 

Reappearance  of  nucleoli, 

Complete  division  of  cell-body, 

Daughter  nuclei  assume  vegetative  condition, 

Achromatic  striation  usually  disappears, 

Centrosomes,  single  or  divided,  lie  beside  new  nuclei. 

AMITOTIC   DIVISION. 

The  occurrence  of  cell  reproduction  without  the  foregoing  complex  cycle  of 
karyokinetic  changes  is  known  as  amitotic  or  direct  division.  That  this  process  does 
take  place  as  an  exceptional  method  in  the  reproduction  of  the  simplest  forms  of  ani- 
mal life,  or  in  the  multiplication  of  cells  within  pathological  growths  or  tissues  of  a 

transient  nature,  as  the  fcetal  envelopes,  may 
Fig.  io.  be  regarded  as  established  beyond  dispute. 

•s^Brs  The  essential  difference  between  amitotic 

-J.    v-~-..  ir  and  the  usual  method  of  division  lies  in  the 

fjtSm     k  /     ^  fact  that,  while  in  the  latter  the  chromatin  of 

k±u7'      |  L       f^  the  nucleus  is  equally  divided  and  the  number 

s?      -x      sgri^ss**  of  chromosomes  carefully  maintained,  in  direct 

~*  ~  ,.    "t ,::..,  division  the  nucleus  remains  passive  and  suffers 

■>'; ■;      j  cleavage  of  its  total  mass,  but  not  of  its  indi- 

•  '■    ~~ '■■-..  D  vidual    components.       Since  the   nucleus    re- 

E   ■• '      ~x.  rV7!.       .  ~-;-\  mains    in    the    vegetative    condition,    neither 

.yi:  -.  T&\i  -/ r-\  the  chromatic  nor  achromatic   figure  is  pro- 

\    '-'.?/'"  -'"'    Vg*  duced,  the  activity  of  the  centrosome,  when 

&?~  '       ■  exhibited,  being  possibfy  directly  expended  in 

effecting  a  division  of  the  cytoplasm,  and  inci- 
dentally that  of  the  nucleus.      In  many  cases 

Decidual  cells  showing  amitotic  division  of         tUp    arnitntir  division    nf    thp  niii-lpns  is  rmt  a<~ 
nucleus  (A-D) ;   in  E  an  attempt  at  mitosis  has        Ine    amitOUC  UlVlSlon   OI    me  nucleus  IS  not  ac- 

occurred.   x  410.  companied  by  cleavage  of  the  cytoplasm,  such 

processes  resulting  in  the  production  of  multi- 
nuclear  and  aberrant  nuclear  forms.  In  general,  it  may  be  assumed  that  cells  which 
undergo  direct  division  are  elements  destined  to  suffer  premature  degeneration, 
since  such  cells  subserve  special  purposes  and  are  not  capable  of  perpetuating  their 
kind  by  normal  reproduction.  Flemming  has  pointed  out  the  fact  that  those  leuco- 
cytes which  arise  by  amitotic  division,  and  therefore  deviate  from  the  usual  mode  of 
origin  of  these  elements,  are  cells  which  are  doomed  to  early  death;  this  form  of 
cell-division  among  the  higher  forms  must  be  regarded,  probably,  as  a  secondary 
process. 


EARLY   DEVELOPMENT. 

The  human  body  with  all  its  complex  organism  is  the  product  of  the  differentia- 
tion and  specialization  of  the  cells  resulting  from  the  union  of  the  parental  sexual 
elements, — the  ovum  and  the  spermatozoon. 

The  Ovum. — The  maternal  germ-cell  is  formed  within  the  female  sexual  gland, 
the  ovary,  in  which  organ  it  passes  through  all  stages  of  its  development,  from  the 
immature  differentiation  of  its  early  condition  to  the  partially  completed  matura- 
tion of  the  egg  as  it  is  liberated  from  the  ovary. 

The  human  ovum,  in  common  with  the  ova  of  other  mammals,  is  of  minute 
size,  being,  as  it  is  discharged  from  the  ovary,  about  .  2  millimetre  in  diameter.  Ex- 
amined microscopically  and  after  sectioning,  the  human  ovum  is  seen  to  be  enclosed 
within  a  distinct  envelope,  the  zona  pellucida,  .014  millimetre  in  thickness,  which 
in  favorable  preparations  exhibits  a  radial  striation,  and  hence  is  also  named  the 
zona  radiata.  This  envelope  at  first  was  confounded  with  the  proper  limiting  mem- 
brane of  the  cell,  and  for  a  time  was  erroneously  regarded  as  corresponding  to  the 


Fig.  11. 

/Jv'sffjV-."! "'-'■  '-•    I        - 

. 

Corona,  radiata. 

,  :_..'_■« 

S      —  Zona  pellucida 

r .  ^-r- 

:..':V>|| 

n  ^ — Germinal  vesicle  (nu- 

■B          cleus)  containing- germ- 
Bw         inal  sPot  (nucleolus) 

-Zone  rich  in  deutoplasm 


-Zone  poor  in  deutoplasm 
fading  into  homogene- 
ous peripheral  zone 


Human  ovum  from  ripe  Graafian  follicle.    X  170.    (Nagel.) 

cell-wall.  The  nature  of  the  zona  pellucida  is  now  generally  conceded  to  be  that  of 
a  protecting  membrane,  produced  through  the  agency  of  cells  surrounding  the 
ovum. 

The  substance  of  the  ovum,  the  yolk,  or  vitellus,  consists  of  soft,  semifluid  pro- 
toplasm modified  by  the  presence  of  innumerable  yolk-granules,  the  representatives 
of  the  important  stores  of  nutritive  materials  present  in  the  bird's  egg.  Critically 
examined,  the  vitellus  is  resolvable  into  a  reticulum  of  active  protoplasm,  or  ooplasm, 
and  the  nutritive  substance,  or  deutoplasm.  At  times  the  yolk  is  limited  externally 
by  a  very  delicate  envelope,  the  vitelline  membrane,  which  usually  lies  closely  placed, 
or  adherent,  to  the  protecting  zona  radiata  ;  sometimes,  however,  it  is  separated 
from  the  latter  by  a  perivitelline  space.  The  vitelline  membrane  is  probably  absent 
in  the  unfertilized  human  ovum. 

A  large  spherical  nucleus,  '•Axe  germinal  vesicle,  approximately  .037  millimetre  in 
diameter,  usually  lies  eccentrically  within  the  yolk,  surrounded  by  the  distinct  nuclear 
membrane.      Within   the   germinal   vesicle   the    constituents   common    to   nuclei    in 


i6 


HUMAN   ANATOMY. 


Fig.  12. 


general  are  found,  including  the  all-important  chromatin  fibrils,  nuclear  matrix,  and 
nucleolus  ;  the  latter,  in  the  original  terminology  of  the  ovum,  is  designated  as  the 
germinal  spot,  and  measures  about  .005  millimetre  in  diameter.  In  addition  to 
these  more  easily  distinguished  components  of  the  maternal  cell,  the  centrosome 
must  be  accepted  as  a  constant  constituent  of  the  fully  formed,  but  unmatured, 
ovum,  although  its  presence  may  escape  detection. 

The  Spermatozoon. — The  male  germ-cell,  the  spermatic  filament,  is  produced 
by  the  specialization  of  epithelial  elements  lining  the  seminiferous  tubules  within  the 
testicle.  The  human  spermatozoon  consists  of  three  parts, 
— the  ovoid  head,  the  cylindrical  middle-piece,  and  the  attenu- 
ated, greatly  extended  tail ;  of  these  the  head  and  middle- 
piece  are  the  most  important,  since  these  parts  contain  re- 
spectively the  chromatin  and  the  centrosome  of  the  cells  from 
which  the  spermatic  filaments  are  derived.  The  centrosome 
is  represented  by  a  minute  spherical  body,  the  end-knob,  which 
lies  in  the  middle-piece  immediately  beneath  the  head  at  the 
extremity  of  the  axial  fibre  ;  the  latter  extends  throughout  the 
spermatozoon  from  the  head  to  the  termination  of  the  tail, 
ending  as  an  extremely  attenuated  thread,  the  terminal  fila- 
ment. The  tail  corresponds  to  a  flagellum  and  serves  the 
purposes  of  propulsion  alone,  taking  no  part  in  the  important 
changes  produced  in  the  ovum  by  the  entrance  of  the  male 
element.  It  is  of  interest  to  note  that  both  the  ovum  and 
the  spermatozoon  are  the  direct  specializations  of  epithelial 
tissue,  the  active  elements  of  the  primary  indifferent  sexual 
glands  being  derived  from  the  mesodermic  lining  of  the 
body-cavity. 

Maturation  of  the  Ovum. — Maturation,  or  ripening 
of  the  ovum,  is  that  process  by  which  the  female  element  is 
prepared  for  the  reception  of  the  spermatozoon.  It  takes  place, 
however,  entirely  independently  of  the  influence  of  the  male 
or  of  the  probability  of  fertilization,  every  healthy  ovum  un- 
dergoing these  changes  before  it  becomes  sexually  ripe. 
About  the  time  that  the  ovum  is  liberated  from  the  ovary  by 
the  bursting  of  the  Graafian  follicle,  as  the  sac  which  encloses 
the  egg  within  the  ovarian  stroma  is  called,  its  nucleus  en- 
gages in  the  complicated  cycle  already  described  as  mitotic 
division.  The  nucleus  migrates  to  the  periphery  of  the  ovum, 
loses  its  limiting  membrane,  and  undergoes  division,  one  pole 
of  the  nuclear  spindle  being  located  within  the  protrusion  of 
protoplasm  which  has  coincidently  taken  place.  With  the 
division  of  the  nuclear  chromatin,  the  protruded  protoplasm 
becomes  constricted  and  finally  separated  from  the  ovum  ;  the  minute  isolated  mass 
thus  formed,  containing  one-half  of  the  maternal  chromatin,  is  the  first  polar  body. 
Almost  immediately  the  mitotic  cycle  is  repeated,  and  again  results  in  the  constric- 
tion and  final  separation  of  a  minute  cell,  the  second  polar  body.  These  two  isolated 
portions  of  the  ovum  remain  visible  for  a  long  time  as  small,  deeply  stained  cells 
lying  within  the  perivitelline  space  beneath  the  zona  pellucida. 

The  chromatin  remaining  within  the  ovum  after  the  repeated  division  becomes 
collected  within  a  new  nucleus,  which  now  takes  a  non-central  position  within  the 
egg,  and  is  henceforth  known  as  the  female  pronucleus  or  egg-nucleus.  After  matu- 
ration the  ovum  is  prepared  for  union  with  the  spermatozoon,  although  in  many 
cases  the  male  sexual  element  has  actually  entered  the  ovum  before  the  completion 
of  the  maturation  cycle  :  should,  however,  impregnation  not  occur,  the  ovum  passes 
along  the  oviduct  into  the  uterus  and  is  finally  lost.  The  passage  of  the  human 
egg  from  the  ovary  to  the  uterus  occupies,  probably,  about  eight  days,  a  period 
corresponding  closely  to  the  length  of  time  that  the  ovum  retains  its  capability  of 
fertilization. 

The  significance  of  the  extrusion  of  the  polar  bodies— a  process  which  .occurs 


-Terminal  filament 


EARLY    DEVELOPMENT.  i7 

with  great  constancy  in  almost  all  animals,  and,  indeed,  is  probably  represented  in 
the  development  of  vegetal  organisms  as  well— has  been  the  subject  of  much  dis- 
cussion and  speculation.  The  most  satisfactory  explanation  of  the  significance  of 
maturation  has  been  proposed  by  Van  Beneden,  Boveri,  and  others,  based  upon  the 
comparison  of  the  changes  which  take  place  in  the  development  of  the  germ-cells 
of  the  two  sexes. 

In  order  to  appreciate  the  necessity  and  the  meaning  of  maturation  of  the  ovum, 
it  will  be  of  advantage  to  take  a  brief  survey  of  the  phenomena  attending  the  devel- 
opment of  the  male  sexual  elements.  The  seminiferous  tubules  of  the  testicle  are 
lined  with  epithelial   cells,   certain  of  which,  known  as  the  primary  spermatocytes, 

Fig.  13. 


f^-f  e   •••:?\_^/' 


(" 


Semi-diagrammatic  representation  of  the  formation  of  the  polar  hodies,  based  upon  observations  of  invertebrate 
ova  {Ascaris  and  Physd).  n,  nucleus;  c,  c,  centrosomes;  i,  nuclear  spindle;  p' ,  p" ,  first  and  second  polar  bodies; 
e>  egg-nucleus.     {After  Kostanecki  and  Wierzejski.) 

increase  in  size  and  undergo  division,  the  daughter  cells  constituting  the  secondary 
spermatocytes.  Each  of  the  latter,  in  turn,  gives  rise  to  a  new  generation,  the  sper- 
matids, from  which  the  spermatozoa  are  directly  formed,  the  chromatin  of  the  sper- 
matid being  stored  within  the  head,  and  the  centrosome  forming  the  end-knob  within 
the  middle-piece.  The  spermatozoon,  therefore,  represents  the  third  generation 
and  corresponds  to  the  mature  ovum. 

Turning  to  the  phenomena  of  maturation,  a  parallel  process  is  presented,  since 
the  ovarian  egg,  or  primary  oocyte,  divides  into  two  cells,  the  secondary  oocytes, 
represented  by  the  ovum  and  the  first  polar  body,  each  of  which  receives  one-half  of 
the  chromatin,  notwithstanding  that  one  of  the  daughter  cells,  the  first  polar  body, 
is  disproportionately  small  ;  the  repetition  of  division  effects  a  second  distribution  of 


1 8  HUMAN    ANATOMY. 

the  chromatin,  so  that  the  mature  egg,  after  the  completion  of  maturation,  represents 
the  third  generation,  and  is,  therefore,  morphologically  equivalent  to  a  spermatozoon. 
Attention  has  already  been  directed  to  the  important  fact  that  the  cells  of  a 
given  species  contain  a  fixed,  definite,  and  even  number  of  chromosomes  (page 
12);  hence,  in  their  primary  condition,  each  germ-cell  contains  the  full  complement 
of  chromatin  segments.  Since,  however,  the  new  being  arises  from  the  elements 
derived  from  the  segmentation  of  a  cell  to  the  nucleus  of  which  both  parents  con- 
tribute an  equal  number  of  chromosomes,  it  follows  that,  unless  some  provision  be 
made  whereby  the  number  of  chromosomes  in  each  germ-cell  be  reduced  to  one- 


Primordial  germ-cell 


Fig.  14. 


Division-period 


Growth-period 


Primordial  germ-cell 


Maturation-period 


Primary  1 


egg) 

Secondary  oocytes 
(egg  and  first 
polar  body) 

Mature  egg  and 
polar  bodies 

Diagram  illustrating  the  genesis  of  the  male  and  female  germ-cells.    {A/ter  Boveri. ) 

half  the  full  number,  the  elements  of  the  new  being  would  be  provided  with  double 
the  number  required  to  satisfy  the  normal  complement  for  the  particular  species. 
In  fact,  such  reduction  of  the  chromosomes  of  the  germ-cells  does  take  place  during 
the  development  of  these  elements,  in  consequence  of  which  the  ovum  and  the 
spermatozoon  each  contribute  only  one-half  the  number  of  chromosomes,  the  nor- 
mal quota  being  restored  to  the  segmentation  nucleus,  and  subsequently  to  the  cells 
of  the  new  being,  by  the  sum  of  the  contributions  of  both  parents. 

Interpreted  in  the  light  of  these  considerations,  maturation  may  be  regarded  as 
the  means  by  which  correspondence  between  the  sexual  cells  is  secured,  and,  further, 
the  polar  bodies  may  be  considered  as  abortive  ova. 

Fertilization  of  the  Ovum. — Impregnation,  or  fertilization  of  the  ovum, 
includes  the  meeting  of  the  male  and  female  elements,  the  penetration  into  the  sub- 
stance of  the  latter  by  the  former,  and  the  changes  immediately  induced  by  the 
presence  of  the  spermatozoon  within  the  egg. 

Coincidently  with  the  rupture  of  the  distended  Graafian  follicle,  the  surface  of 
the  ovary  is  embraced  by  the  expanded  fimbriated  extremity  of  the  oviduct,  along  the 
plications  of  which  the  liberated  matured  ovum  is  guided  into  the  tube.  It  is  highly 
probable  that  not  an  inconsiderable  number  of  the  ova  discharged  from  the  ovary  fail 
to  reach  the  oviduct  and  are  lost  in  the  abdominal  cavity. 

Fertilization  usually  takes  place  in  the  upper  third  of  the  oviduct,  shortly  after 
the  ovum  has  escaped  from  the  Graafian  follicle,  although  any  part  of  the  tract  from 
the  ovary  to  the  uterus  may  be  the  seat  of  impregnation. 

The  spermatozoa  overcome  the  obstacles  offered  within  the  narrow  channels 
by  the  mucus  and  the  opposed  ciliary  currents  of  the  uterine  and  tubal  mucous 
membranes  by  virtue  of  their  long  actively  vibrating  tails,  and  advance  at  a  rate 
estimated  at  from  1.5  to  2.5  millimetres  per  minute  ;  it  is  therefore  probable  that 
the  seminal  cells  accomplish  the  journey  from  the  mouth  of  the  uterus  to  the  ovum 
in  from  eight  to  ten  hours.  Spermatozoa  retain  their  vitality  and  fertilizing  pow- 
ers for  many  days  within  the  normal  female  genital  tract  ;  repeated  observation  on 
the  human  subject  has  shown  that  this  period    may  extend  throughout  an  entire 


FERTILIZATION    OF    THE    OVUM. 


19 


menstrual  cycle  of  twenty-eight  days,— a  possibility  to  be  remembered  when  calcu- 
lating the  probable  termination  of  pregnancy. 

Of  the  many  millions  of  spermatic  elements  deposited  within  the  vagina,  only 

Fig.  15. 

A  B  *  C 


'# 


<    •* 


Fertilization  of  the  ovum  as  nitrated  by  sections  of    ^f  ^  mou         (Sottta^  Al    ^figures  are 
magnified  437  diameters  except £-G,  m  ,  amp ifica    on  ,s  ^^^     ^  P,^^     ,  t 

zoon  E  intc ^lyu(ntlnd,subslqlue,n  cnanges  H-M,  sequence  of  change?  during  the  formation,  approach,  and  blend- 
ing of  the  male  (m)  and  female  (/)  pronuclei  ;/■./>,  polar  bodies. 

an  insignificant  number  ever  reach  the  vicinity  of  the  ovum.  _  Notwithstanding 
that  probably  a  number  of  spermatozoa  penetrate  the  zona  pellucida  normal  fertili- 
zation in  man  and  the  higher  animals  is  effected  by  a  single  seminal  element.     Alter 


20  HUMAN   ANATOMY. 

the  entrance  of  the  favored  spermatozoon  into  the  substance  of  the  ovum,  an  effec- 
tual barrier  to  the  penetration  of  additional  seminal  cells  is  presented  by  the  thick 
vitelline  membrane  which  immediately  forms.  The  point  at  which  the  spermatozoon 
is  about  to  enter  the  egg  is  indicated  by  a  conical  elevation,  the  receptive  eminence, 
into  which  the  male  germ-cell  sinks, — the  tail  only  partly  entering  the  protoplasm 
of  the  egg  and  very  soon  disappearing. 

The  position  of  the  remains  of  the  spermatozoon  within  the  substance  of  the 
ovum  is  indicated  by  an  ovoid  body,  the  male  pronucleus ,  which  contains  the  chro- 
matin and  centrosome  of  the  paternal  germ-cell.  The  sperm-?iuclez(s  and  the  egg- 
nucleus,  as  the  male  and  female  pronuclei  are  now  often  designated,  usually  break 
up   into   their   respective  chromosomes  without  fusing  into   a  single  segmentation 


Early  stages  of  segmentation  as  seen  in  ova  of  mouse,  surface  view.  X  450.  (Sobotta.)  The  external  double 
contour  represents  the  zona  pellucida;  the  cell  marked  with  X,  the  polar  body.  A,  fertilized  ovum  at  stage  of  the 
pronuclei;  B,  two  segmentation  spheres  of  equal  size;  C,  segmentation  spheres  of  unequal  size;  £>,  three-cell  stage 
resulting  from  division  of  larger  sphere ;  E,  stage  of  four  spheres ;  F,  six ;  G,  eight ;  H,  sixteen  ;  /,  twenty-five. 

nucleus.      In  this  case  the  two  groups    of  chromosomes  unite  in  the  first  mitotic 
figure,  the  segmentation  spindle  (Fig.  17). 

After  the  fusion  of  the  pronuclei,  and  just  as  segmentation  is  beginning,  the 
fertilized  ovum  presents  a  clear  oval  area  which  contains  the  two  groups  of  chromo- 
somes contributed  by  the  germ-cells  of  both  parents  ;  on  opposite  sides  of  the  chro- 
matin figure  are  the  centrospheres,  each  containing  a  centrosome  and  surrounded 
by  a  marked  polar  striation  within  the  substance  of  the  egg.  The  centrosomes  now 
present  within  the  ovum  are  usually  both  derived  from  the  substance  of  the  cen- 
trosome of  the  spermatid,  which  entered  the  ovum  as  the  end-knob  within  the  mid- 
dle-piece of  the  fertilizing  spermatozoon.  The  role  of  the  latter,  therefore,  is  two- 
fold — to  contribute  the  chromatin  necessary  to  restore  to  the  parent  cell  the  normal 


SEGMENTATION    OF   THE   OVUM.  21 

complement  of  chromosomes,  and  to  furnish  the  stimulus  required  to  inaugurate  the 
karyokinetic  cycle  of  segmentation. 

Segmentation  of  the  Ovum. — The  union  of  the  male  and  female  pronuclei 
and  the  resulting  formation  of  the  segmentation  nucleus  is  followed  immediately 
by  the  division  of  the  ovum  into  two  new  elements  ;  each  of  these  gives  rise  to  two 
additional  cells,  which,  in  turn,  produce  following  generations  of  segmentation  cells, 
or  blastomeres.      This   process  of   repeated  division  of   the  fertilized  ovum  and  its 


Early  stages  of  segmentation  as  seen  in  sections  of  ova  of  mouse.  X  500.  {Sobotta.)  A-D  show  the  rearrange- 
ment of  the  chromosomes  contributed  by  the  male  (m)  and  female  (/)  pronuclei  as  preparatory  to  the  first  cleavage 
of  the  fertilized  ovum;  />,p,  polar  bodies;  ep,  stage  of  equatorial  plate;  a,  />,  daughter  groups  of  chromosomes. 
E,  F,  the  daughter  cells  arising  from  first  cleavage.  G,  one  cell  (6)  is  larger  and  is  preparing  to  divide.  H,  later 
stage  of  this  division.     /,  stage  of  three  segmentation  spheres  (a  and  ct  c)  resulting  from  this  division. 


descendants  constitutes  segmentation, — a  process  common  to  the  development  of 
all  animals  and  plants  above  the  very  simplest. 

Study  of  the  details  of  segmentation  in  the  various  classes  of  animals  shows 
that  a  close  relation  exists  between  the  character  of  the  cleavage  and  that  of  the 
ovum  with  regard  to  the  amount  and  distribution  of  the  nutritive  yolk,  or  deuto- 
plasm,  present. 

In  the  human  and  mammalian  egg  the  nutritive  yolk  particles  are  compara- 
tively meagre  and  are  uniformly  distributed  throughout  the  vitellus  ;  in  such  eggs 
there  is  no  aggregation  of  the  food  particles,  hence  such  ova  are  termed  hoinokcithal 
or  with  a  homogeneous  yolk.      In  the  eggs  of  birds,  reptiles,  and  fishes,  on  the  con- 


22  HUMAN   ANATOMY. 

trary,  the  deutoplasm,  or  nutritive  material,  is  collected  towards  one  pole  of  the  egg, 
while  the  protoplasm,  or  formative  material,  is  limited  to  the  other  ;  eggs  in  which 
these  conditions  obtain  possess  a  distinctly  polar  yolk,  and  hence  are  known  as 
telolecithal  ova.  These  aggregations  of  the  protoplasm  and  the  deutoplasm  con- 
stitute respectively  the  formative  and  the  nutritive  yolk,  and  correspond  in  position 
to  the  animal  and  the  vegetative  poles  of  the  egg.  In  an  additional  class  of  eggs, 
the  centrolecithal,  the  yolk  occupies  the  centre  of  the  ovum,  being  covered  by  a 
peripheral  zone  of  formative  material  ;  since  such  ova  belong  alone  to  certain  in- 
sects and  are  not  found  among  vertebrates,  they  possess  limited  interest  to  students 
of  mammalian  forms. 

Comparison  of  the  behavior  of  these  various  groups  of  ova  during  segmen- 
tation shows  that  only  eggs  poor  in  deutoplasm,  as  the  alecithal  mammalian  and 
amphibian  ova,  undergo  complete  cleavage  during  segmentation,  those  of  the  bird, 
reptile,  and  fish  undergoing  cleavage  only  within  the  formative  yolk.  Ova,  there- 
fore, are  classified  according  to  the  completeness  of  their  division  into  those  exhibit- 
ing complete  segmentation  and  those  undergoing  partial  segmentation;  the  former 
are  known  as  holoblastic,  the  latter  as  meroblastic.  The  embryologist  further  recog- 
nizes an  equal  and  an  unequal  complete  segmentation  according  to  the  equality  or 
inequality  of  the  cells,  or  blastomeres,  resulting  from  the  division  of  the  ovum. 
Since  the  segmentation  spheres  derived  from  the  mammalian  egg  may  be  regarded 
as  practically  of  equal  size,  the  egg  of  this  class  of  animals,  including  the  human 
ovum,  is  described  as  an  homolecithal  holoblastic  ovum,  undergoing  equal  segmenta- 
tion.     It  must  be  understood,  however,  that  even  in  the  segmentation  of  such  ova 

Fig.  19. 

Ectoblast 
— Entoblast 


Zona  pellucidf 


Diagram  of  early  mammalian  blastodermic  vesicle,  Diagram  of  mammalian  blastodermic  vesicle  ;  inner 

consisting  of  trophoblast  and  inner  cell-mass.  cells  differentiating  into  ectoblast  and  entoblast.   '{After 

{After  I  an  Beneden.)  Van  Beneden.) 

the  blastomeres  very  early  exhibit  inequality  in  size  and  in  rapidity  of  division  (Fig. 
16),  the  effect  of  this  differentiation  being,  that  the  more  rapidly  multiplying  blas- 
tomeres are  smaller  than  the  more  slowly  dividing  elements.  It  is  of  interest,  in  this 
connection,  to  note  that  the  purest  type  of  total  equal  segmentation  is  observed  in 
the  ovum  of  the  lowest  vertebrate,  the  amphioxus, — an  animal  whose  development 
has  shed  much  light  on  many  obscure  problems  in  the  embryology  of  the  higher 
forms,  including  mammals  and  even  man. 

The  meroblastic  bird's  egg,  on  the  contrary,  undergoes  cleavage  only  within  a 
limited  circular  field  at  its  animal  pole  ;  it  is  said,  therefore,  to  undergo  partial  dis- 
coidal  segmentation.  In  contrast  to  this,  the  centrolecithal  ova  exhibit  partial  super- 
ficial segmentation,  the  peripheral  zone  of  formative  material  alone  undergoing 
cleavage. 

The  Blastoderm  and  the  Blastodermic  Layers. — The  completion  of 
segmentation  in  holoblastic  ova  results  in  the  production  of  a  mass  of  blastomeres, 
which  is  a  solid  sphere  composed  of  mutually  compressed  segmentation  cells ;  to  this 
sphere  the  older  anatomists  gave  the  name  of  the  morula,  or  the  mulberry  mass. 
The  solidity  of  the  morula  is  temporary,  since  a  cavity  is  soon  developed  within  it. 
This  cavity,  often  called  the  segmentation  cavity,  increases  to  such  an  extent  that  a 


THE    BLASTODERMIC    VESICLE. 


23 


hollow  sac  is  formed,  walled  by  a  single  layer  of  cells,  at  one  point  on  the  inner  sur- 
face of  which  is  attached  a  small  mass  of  cells.  The  outer,  covering  layer  of  cells  is 
known  as  the  trophoblast ;  the  small  group  of  cells  attached  to  the  inner  surface  of 
the  trophoblast  is  known  as  the  inner  cell-mass  (Fig.  18).  Examined  from  the  sur- 
face, this  aggregation  of  inner  cells  appears  as  an  opaque  circular  field,  the  embryonic 
area,  due  to  the  increased  thickness  and  consequent  diminished  transparency  of  the 
wall  of  the  blastodermic  vesicle  at  the  place  of  attachment  of  the  included  cells.  In 
the  purest  type  of  the  blastodermic  vesicle,  that  seen  in  the  amphioxus  (Fig.  26, 
A),  the  sac  consists  of  a  single  layer  of  blastomeres  of  almost  uniform  size  ;  the 
mammalian  blastodermic  vesicle,  however,  presents  greater  complexity,  due  to  the 
unequal  rate  at  which  some  of  the  segmentation  cells  divide  and  to  the  rapid  increase 
in  the  size  of  the  vesicle. 

The  inner  mass  of  germinal  cells  soon  undergoes  differentiation  (Fig.  19)  into 
two  strata, — an  outer  layer,  closely  applied  to  the  trophoblast,  and  an  inner  layer. 
These  layers  are  respectively  the  ectoblast  and  the  entoblast, — two  of  the  three  great 
primary  blastodermic  layers  from  which  the  embryo  is  differentiated. 

Coincidently  with  the  formation  of  these  germinal  layers,  the  mammalian  blas- 
todermic vesicle  grows  with  great  rapidity,  increasing  from  a  sphere  of  microscopic 
size  to  a  vesicle  of  one  or  more  millimetres  in  diameter.  In  consequence  of  this 
precocious  growth  the  trophoblast  undergoes  great  expansion,  with  the  result 
that  its  cells,  in  some  cases  at  least,  become  temporarily  reduced  to  flattened 
plate-like  elements.  For  a  time  these  flattened  trophoblast  cells  may  extend  over 
the  embryonic  ectoblast,  as  in  the  rabbit,  and  have  been  called  the  cells  of  Rauber. 
In  such  cases,  therefore,  the  ectoblast  is  overlaid  within  the  embryonic  area  by  the 
cells  of  Rauber,  but  at  the  margin  of  the  area,  the  embryonic  ectoblast  is  continuous 
with  the  trophoblast  forming  the  outer  layer  of  the  wall  of  the  blastodermic  vesicle. 
With  the  subsequent  expansion  of  the  blastodermic  vesicle,  the  cells  of  Rauber  dis- 
appear from  the  surface  of  the  embryonic  ectoblast,  which  then  lies  upon  the  surface 
of  the  vesicle. 


Diagram  of  mammalian  blastodermic  vesicle ; 
entoblast  forms  an  almost  complete  inner  layer. 


Trophoblast 


Diagram  of  mammalian  blastodermic  vesicle  ;  the 
mesoblast  is  just  appearing  as  the  third  blastodermic 
layer. 


The  early  blastodermic  vesicle  at  first  consists  of  only  two  primary  layers,  the 
ectoblast  and  the  entoblast  ;  this  stage  of  development  is  appropriately  termed  that 
of  the  bilaminar  blastoderm  (Fig.  20);  a  little  later,  a  third  layer,  the  mesoblast, 
makes  its  appearance  between  the  outer  and  inner  blastodermic  sheets  ;  this  stage  is 
designated  as  that  of  the  trilaminar  blastoderm  (Fig.  21). 

The  early  embryo,  shortly  after  the  formation  of  the  blastodermic  vesicle,  con- 
sists of  three  layers  of  cells, — the  ectoblast,  the  mesoblast,  and  the  entoblast.  The 
histological  characters  of  the  outer  and  inner  of  these  primary  layers  differ,  almost 


24  HUMAN   ANATOMY. 

from  the  first,  from  those  of  the  mesoblast,  their  component  elements  being  more 
compact  in  arrangement  and  early  manifesting  a  tendency  to  acquire  the  character- 
istics of  covering  cells  or  epithelium. 

The  mesoblastic  elements,  on  the  contrary,  soon  assume  irregular  forms  and 
are  loosely  held  together  by  intercellular  substance,  thus  early  foreshadowing  the 
special  features  which  distinguish  the  subsequently  differentiated  connective  tissues. 
This  early  distinction  becomes  more  marked  as  differentiation  proceeds,  the  epithelial 
tissues  possessing  elements  of  comparatively  regular  form,  separated  by  minute 
amounts  of  intercellular  substance  ;  the  latter  in  the  connective  tissues,  on  the  con- 
trary, becomes  conspicuous  on  account  of  its  excessive  quantity  and  the  resulting 
profound  modifications  in  the  physical  character  of  the  tissue;  the  cells  of  the  con- 
nective tissues  rapidly  assume  the  irregularly  stellate  or  triangular  form  so  charac- 
teristic in  young  tissues  of  this  class.  Since  the  three  primary  layers  give  rise  to  all 
the  tissues  of  the  organism,  a  brief  synopsis  presenting  these  genetic  relations  here 
finds  an  appropriate  place. 

DERIVATIVES  OF  THE  BLASTODERMIC  LAYERS. 

From  the  ectoderm  are  derived — 

The  epithelium  of  the  outer  surface  of  the  body,  including  that  of  the  conjunc- 
tiva and  anterior  surface  of  the  cornea,  the  external  auditory  canal,  to- 
gether with  the  epithelial  appendages  of  the  skin,  as  hair,  nails,  sebaceous 
and  sweat-glands  (including  the  involuntary  muscle  of  the  latter). 

The  epithelium  of  the  nasal  tract,  with  its  glands,  as  well  as  of  the  cavities 
communicating  therewith. 

The  epithelium  of  the  mouth  and  of  the  salivary  and  other  glands  opening  into 
the  oral  cavity. 

The  enamel  of  the  teeth. 

The  tissues  of  the  nervous  system. 

The  retina  ;  the  crystalline  lens,  and  perhaps  part  of  the  vitreous  humor. 

The  epithelium  of  the  membranous  labyrinth. 

The  epithelium  of  the  pituitary  and  pineal  bodies. 

From  the  mesoderm  are  derived — 

The  connective  tissues,  including  areolar  tissue,  tendon,  cartilage,  bone,  den- 
tine of  the  teeth. 

The  muscular  tissues,  except  that  of  the  sweat-glands  and  dilator  pupillae. 

The  tissues  of  the  vascular  and  lymphatic  systems,  including  their  endothelium 
and  circulating  cells. 

The  sexual  glands  and  their  excretory  passages,  as  far  as  the  termination  of  the 
ejaculatory  ducts  and  vagina. 

The  kidney  and  ureter. 

From  the  entoderm  are  derived — 

The  epithelium  of  the  digestive  tract,  with  that  of  all  glandular  appendages 
except  those  portions  derived  from  ectodermic  origin  at  the  beginning 
(oral  cavity)  and  termination  of  the  tube. 

The  epithelium  of  the  respiratory  tract. 

The  epithelium  of  the  urinary  bladder  and  urethra. 

The  epithelium  of  the  thyroid  and  thymus  bodies,  the  modified  primary  epithe- 
lium of  the  latter  giving  rise  to  Hassall's  corpuscles. 

The  Primitive  Streak  and  the  Gastrula. — Examined  from  the  surface 
during  the  formation  of  the  primary  layers,  the  mammalian  blastodermic  vesicle,  as 
represented  by  that  of  the  rabbit,  presents  a  circular  light-colored  field,  the  embryonic 
area,  which  corresponds  to  the  expansion  of  the  original  embryonic  spot,  the  latter 
becoming  larger  with  the  extension  of  the  ectoblast  and  the  entoblast  differentiated 
from  the  inner  cell  mass.  At  first  circular,  the  embryonic  area  later  becomes  oval 
or  pyriform  in  outline  (Figs.  22,  23),  the  larger  end  corresponding  with  the  cephalic 


THE    EMBRYONIC    AREA.  2-5 

pole  of  the  future  embryo.  In  consequence  of  the  proliferation  of  the  ectoblastic 
cells,  the  embryonic  area  becomes  differentiated  into  a  central  field,  the  embryonic 
shield,  and  a  peripheral  zone,  the  area  pellucida,  which  by  transmitted  light  appear 
respectively  dark  and  light,  owing  to  the  varying  transparency  cf  the  thicker  cen- 
tral and  thinner  peripheral  portions  of  the  germinal  field. 


Fig.  22. 


Fig. 


-Area  pellucida 


-7~Embryonic  shield 
7 — Area  pellucida 


Embryonic  area  of  rabbit  of  about 
half  days,  seen  from  the  surface  by  trail' 
/  26.     {Kallmann.) 


-Embryonic  shield 
-Wall  of  blastodermic 


Embryonic  area  of  rabbit  of  about  seven  days 
the  surface.    X  26.     (Kollmann.) 


Fig.  24. 


-Hensen's  node 


Extra-embryonic 
part  of  biasto- 


Coincidently  with  the  assumption  of  the  oval  or  pyriform  outline,  the  caudal 
border  of  the  embryonic  area  exhibits  a  luniform  thickening,  the  embryonic  crescent ; 
from  the  latter  proceeds  the  formation  of  a  conspicuous,  although  transient,  structure, 
known  as  the  primitive  streak  (Fig.  24).  The  latter  appears  as  a  lineal  thicken- 
ing which  extends  forward  well  towards  the 
centre  of  the  embryonic  area.  The  pro- 
liferation of  the  outer  blastodermic  layer 
along  the  primitive  streak  is  accompanied 
by  the  appearance  of  a  narrow  longitudinal 
furrow,  the  primitive  groove,  throughout  its 
extent  with  the  exception  of  its  anterior  end, 
at  which  point  the  primitive  streak  termi- 
nates in  a  thickened  extremity,  the  node  of 
Hensen.  Although  indicating  the  direction 
of  the  axis  of  the  future  embryo,  the  primi- 
tive streak  takes  no  part  in  the  formation 
of  the  new  organism,  being  entirely  tran- 
sient in  its  career.  Transverse  section  of  the 
anterior  end  of  the  primitive  streak  (Fig. 
25)  shows  that  in  that  place  all  three  of  the 
blastodermic  layers — ectoblast,  mesoblast, 
and  entoblast — are  completely  fused,  the 
mesoblast  in  this  situation — and  here  alone — forming  a  continuous  sheet  interposed 
between,  as  well  as  blended  with,  the  ectoblast  and  entoblast. 

The  Significance  of  the  Primitive  Streak  and  the  mode  of  formation  of 
the  mesoblast  are  vexed  problems  in  embryology.  A  brief  note  on  this  topic  will 
suffice  here.  In  amphioxus,  the  lowest  vertebrate,  the  immediate  result  of  segmen- 
tation is  a  hollow  sphere,  the  blastula,  filled  with  fluid,  lined  by  a  single  layer  of  cells. 
Invagination  at  one  point  of  the  wall  of  the  blastula  occurs,  forming  eventually  a 
two-layered  cup,  the  gastrula,  the  outer  layer  of  which  is  the  ectoblast,  and  the 
inner  one  the  entoblast.  The  cavity  within  the  entoblast  is  the  archenteron  or  primi- 
tive gut.  The  opening  into  the  archenteron  is  the  blastopore.  Cells  given  off  from 
the  entoblast,  near  the  blastopore,  form  a  third  layer,  the  mesoblast.  Typical  gas- 
trulation  does  not  occur  in  the  higher  mammals,  although  in  the  early  human 
embryo  a  canal  appears,  known  as  the  neurentcric  canal,  the  opening  of  which  is 
often  regarded  as  homologous  with  the  blastopore.  The  primitive  streak  is  regarded 
by  some  authorities,  notably  Hertwig,  as  an  elongated  blastopore  with  lips  fused. 
The  mesoblast  is  commonly  thought  to  arise  from  the  entoblast,  although  the  ecto- 
blast, in  the  region  of  the  primitive  streak,  seems  to  have  a  share  in  the  production 
of  the  middle  germ-layer. 


Embryonic  area  of  rabbit  of  about  eight  days,  seen 
from  the  surface.    X  20.    {Ajler  Van  Beneden.) 


26 


HUMAN    ANATOMY. 


THE    FUNDAMENTAL    EMBRYOLOGICAL    PROCESSES. 

Shortly  after  the  appearance  of  the  primitive  streak — a  structure,  it  will  be 
remembered,  which  is  only  transient  and  takes  no  part  in  the  formation  of  the 
embryo  proper — a  series  of  phenomena  mark  the  earliest  stages  of  the  future  new 
being.  These  changes  are  known  as  the  fundamental  embryological  processes,  and 
result  in  the  formation  of  the  neural  canal,  the  notochord,  and  the  somites.  While 
described  for  convenience  as  separate  processes,  they  progress  to  a  great  extent 
simultaneously. 


Transverse  sectio 


ijh  cephalic  end  of  pri 


streak  of  very  you 


The  Neural  Canal. — The  earliest  indication  of  the  embryo  consists  in  the 
appearance  of  two  slightly  diverging  folds  (Fig.  27),  enclosing  the  anterior  end  of 
the  primitive  streak,  which  are  produced  by  a  local  proliferation  and  thickening 
of  the  ectoblast.  These  are  the  medullary  folds  and  mark  the  beginning  of  the 
formation  of  the  neural  ca?ial,  from  which  the  great  cerebro-spinal  nervous  axis, 
together  with  its  outgrowths,  the  peripheral  nerves,  is  derived.  The  medullary  folds 
at  first  border  a  shallow  and  widely  open  furrow  (Fig.  28),  the  medullary  groove  ; 


Fig.  26. 


C 


E 


I 

■■..: 

I'     1 


A.  _-''—  "  '  e  n 


en 


Blastula  and  gastrula  stages  in  the  development  of  amphioxus,  drawn  from  the  models  of  Hatschek.  X  260. 
>4,blastula  composed  of  single  layer  of  cells  surrounding  segmentation  cavity;  ec,  en,  respectively  ectoblastic  and 
entoblastic  areas.  B,  beginning  invagination  of  entohlastic  area  (en).  C,  completed  gastrula ;  ec,  en,  ectoblast  and 
entoblast ;  m,  mesoblast  cell ;  b,  blastopore,  leading  into  archenteron. 

the  latter  becomes  rapidly  deeper  and  narrower  as  the  medullary  folds  increase 
in  height  and  gradually  approach  each  other.  The  approximation  of  the  folds 
(Fig.  29)  and  subsequent  fusion  take  place  earliest  at  some  distance  behind  the 
cephalic  end  of  the  groove,  at  a  point  which  later  corresponds  to  the  upper  cervical 
region  of  the  spinal  cord. 

After  the  closure  of  the  groove  and  its  conversion  into  the  medullary  canal 
(Fig.  32),  the  thickened  and  invaginated  ectoblast  forming  the  lining  of  the  neural 
tube  becomes  separated  from  the  outer  layer  of  the  embryo  by  the  ingrowth  of  the 


THE    NOTOCHORD. 


27 


mesoblast.     The  subsequent  differentiation  of  the  walls  of  the  neural  tube  will  be 

more  fully  considered   in  connection   with   the  nervous  system  ;    suffice  it   here  to 

state  that  the  cephalic  portion   expands  into  the  brain  vesicles,  and  subsequently 

becomes  the  brain  with  the  contained 

ventricles,    while    the    remainder    of  ^1G'  27- 

the    tube   becomes    the   spinal   cord, 

enclosing  the  minute  central  canal. 

The  Notochord. — Coinci- 
dently  with  the  formation  of  the  med- 
ullary groove  the  entoblast  opposite 
the  bottom  of  that  furrow  exhibits 
proliferation  and  thickening  ;  the 
group  of  cells  thus  differentiated  be- 
comes separated  from  the  general 
mass  of  the  inner  layer  and  takes 
up  a  position  immediately  below  the 
neural  tube  (Figs.  30,  31).  This 
isolated  column  of  entoblastic  cells 
constitute  the  notochord,  or  chorda 
dorsalis,  the  earliest  suggestion  of 
the  cardinal  vertebrate  axis  around 
which  the  parts  of  the  early  embryo 

are  symmetrically  arranged.      While  for  a  time  constituting  the  sole  longitudinal  axis 
of  the  embryo,  extending  from  a  point  near  the  cephalic  pole,  which  corresponds  later 


-Medullary  fold 
-Medullary  groove 


Prirqitive  streak 
Embryonic  area 


Embryonic  area  of  rabbit  of  about  eight  and  one-half  days, 
seen  from  the  surface.    X  24.     (Kollmann.) 


Medullary  fold 


Transverse  section  of  rabbit  embryo  of  about  eight  and  one-half  days.     X  80.     Future  1 

widely  open  groove. 


aral  canal  is  represented  by 


Amniotic  sac 


Fig.  29. 

Closing  neural  canal 


Visceral  mesoblast     Entoblast     Chorda    Open  gut-tube 
Transverse  section  of  rabbit  embryo  of  about  nine  and  one-quarter  days 


just  closing. 


to  the  base  of  the  skull,  to  the  caudal  extremity,  the  notochord  is  but  a  temporary 
structure,    and   subseauently   is    supplanted    by   the   true  vertebral    column.      It   is 


28 


HUMAN    ANATOMY. 


interesting  to  note,  that  in  the  connecting  link  between  the  vertebrates  and 
invertebrates,  the  amphioxus,  the  notochord  remains  as  the  permanent  and  sole 
spinal   axis. 

The  history  of  the  notochord  in  man  and  mammals  presents  three  stages  :  (a) 
it  exists  as  an  unbroken  cord  which  extends  uninterruptedly  through  the  series 
of  cartilaginous  vertebrae  ;  (b)  the  notochord  suffers  segmentation  in  such  manner 
that  the  breaks  in  its  continuity  correspond  to  the  vertebral  bodies,  conspicuous 
proliferation  and    local    increase  in   its  substance,    on    the  contrary,    marking    the 


Fig.  31. 


m 


,^  % 


Transverse  sections  through  axis  of  early  human  embryo  of  about  fifteen  days,  showing  formation  of  notochord 
from  entoblast.  High  magnification.  {After  Kollmayin.)  n,  neural  canal;  c/i,  cells  forming  notochord  differenti- 
ating from  entoblast  {e) ;  ?«,  mesoblast ;  j,  early  somite ;  b}  sections  of  primitive  aortse. 

position  of  the  intervertebral  disks  in  which  the  chordal  tissue  during  the  first 
months  after  birth  is  represented  by  a  considerable  mass  of  central  spongy 
substance  ;  (c)  atrophy  of  the  remains  of  the  notochord,  resulting  in  the  entire 
disappearance  of  the  chordal  tissue  within  the  vertebras  and  the  reduction  of  the 
proliferated  intervertebral  cell-mass  to  the  pulpy  substance  existing  within  the 
intervertebral  disks. 

The  cephalic  end  of  the  notochord  in  man  corresponds  in  position  to  the  dorsum 
sellas,  and  marks  the  division  of  the  skull  into   two   parts,  that  lying  in   front  of 

Fig.  32. 


Body-cavity     Splanchno-      Open   Ento-   Chorda    Neural    Visceral     Body-cavity 
pleura  gut       blast  tube       mesoblast 

Transverse  section  of  rabbit  embryo  of  about  nine  and  one-quarter  days.     X  80.     Neural  canal  is  now  closed. 


the  termination  of  the  notochord,  the  prechordal  portion,  and  that  containing  the 
notochord,  the  chordal  portion  ;  the  latter  is  sometimes  described  as  the  vertebral 
segment  of  the  skull. 

The  Ccelom. — The  downward  growth  of  the  neural  ectoblast  and  the  upward 
extension  of  the  chordal  entoblast  effect  a  division  of  the  mesoblast  along  the 
embryonic  axis  into  two  sheets  (Fig.  28).  These  latter  undergo  further  division 
in  consequence  of  the  formation  of  a  cleft  within  their  substance,  as  the  result  of 
which  the  mesoblast  becomes  split  into  two  layers  enclosing  a  space,  the  ccelom,  or 
pj'ii?iaiy  body-cavity  (Fig.  29). 


THE    SOMITES. 


29 


The  cleavage  of  the  mesoblast,  however,  does  not  extend  as  far  as  the  mid-lint- 
of  the  embryo,  but  ceases  at  some  distance  on  either  hand,  thus  leaving  a  tract  of 
uncleft  mesoblast  on  either  side  of  the  medullary  groove  and  the  chorda.  The 
uncleft  area  constitutes  the  paraxial  mesoblast  (Fig.  32),  which  extends  from  the 
head  towards  the  caudal  pole  and  appears  upon  the  dorsal  surface  of  the  embryo  as 
two  distinct  ribbon-like  tracts  bordering  the  neural  canal.  Beyond  the  paraxial 
mesoblast,  the  cleft  portions  of  the  middle  layer  extend  on  either  side  as  the  lateral 
plates  ;  each  lateral  plate  consists  of  two  lamina;,  the  one  forming  the  dorsal  and  the 


Fjg.  33. 


Transverse    sect 
fifteen  days,  showing 
X  210.     (Kollmann.) 


of    human    embryo   of   abo 
arly  differentiation 


Fig.  34- 


-Neural  canal 


'&§#  t\ 


Transverse  section  of  human  embryo  of  about 
twenty-one  days,  showing  differentiation  of  somite. 
X  90.     (Kolbnann.) 


Fig.  35. 


■  Dorsal  border  of 
myotome 


other  the  ventral  boundary  of  the  enclosed  primary  body-cavity  ;  in  view  of  their 
subsequent  relations  to  the  formation  of  the  body-walls  and  the  digestive  tube 
respectively,  the  dorsal  mesoblastic  lamina  is  appropriately  named  the  parietal  layer 
and  the  ventral  lamina  the  visceral  layer  (Fig.  32).  In  the  separation  of  these 
layers,  which  soon  takes  place  in  consequence  of  the  dorsal  and  ventral  folding 
occurring  during  the  formation  of  the  amnion  and  the  gut-tube,  the  parietal  mesoderm 
adheres  to  the  ectoblast,  in  conjunction  with  which 
it  constitutes  the  somatopleiira  (Fig.  29),  the 
ecto-mesoblastic  sheet  of  great  importance  in  the 
production  of  the  lateral  and  ventral  body-walls. 
Similarly,  the  visceral  mesoblast  unites  with  the 
entoblast  to  form  the  splanchnopleura  (Fig.  29), 
the  ento-mesoblastic  layer  from  which  the  walls  of 
the  primary  digestive  canal  are  formed. 

The  Somites. — The  paraxial  mesoblast  at  an 
early  stage — about  the  twentieth  day  in  man — exhibits 
indications  of  transverse  division,  in  consequence 
of  which  this  band-like  area  becomes  differentiated 
into  a  series  of  small  quadrilateral  masses,  the 
somites,  or  protovertebree.  This  segmentation  of 
the  embryonic  mass  appears  earliest  at  some 
distance  behind  the  cephalic  end  of  the  embryo, 
at  a  point  which  later  corresponds  to  the  beginning 

of  the    cervical   region.      The  somites   are   seen  to   best  advantage  in   the   human 
embryo  at  about  the  twenty-eighth  day   (Fig.  71). 

The  early  somites,  on  transverse  section,  appear  as  irregular  quadrilateral  bodies, 
composed  of  mesoblast  and  covered  externally  by  ectoblast,  lying  on  either  side  of 
the  neural  canal  and  the  notochord  (Fig.  33).  Each  somite  consists  of  a  dorsomesial 
principal  cell-mass,  which  is  connected  with  the  lateral  plate  by  means  of  an 
intervening  cell-aggregation,   the  intermediate  cell-mass  (Fig.  33).      Subsequently, 


Differentiation  of  myotome  of  human 
embryo  of  about  twenty-one  days.  X  525. 
{Kolbnann.) 


30  HUMAN    ANATOMY. 

the  latter  becomes  separated  from  the  remaining  portion  of  the  somite  and  is  probably 
identified  with  the  formation  of  the  segmented  excretory  apparatus  of  the  embryo, 
the  Wolffian  body,  and  hence  is  known  as  the  nephrotome. 

The  principal  mass,  including  the  greater  part  of  the  somite  proper,  consists  of 
an  outer  or  peripheral  zone  of  condensed  mesoblast  enclosing  a  core  of  looser  struc- 
ture. The  less  dense  mesoblastic  tissue  later  breaks  through  the  surrounding  zone 
on  the  side  directed  towards  the  notochord  and  forms  a  fan-shaped  mass  of  embryonic 
connective  tissue  which  envelops  the  chorda  and  grows  around  the  neural  canal. 
The  cell-mass  derived  from  the  core  of  the  myotome  constitutes  the  sclerotome,  and 
directly  contributes  the  tissue  from  which  the  permanent  vertebrae  and  the  associated 
ligamentous  and  cartilaginous  structures  arise.  The  remaining  denser  part,  the 
myotome,  which  collectively  forms  a  compressed  C-like  mass,  becomes  differentiated 
into  a  lateral  and  a  mesial  stratum  (Fig.  35).  The  lateral  stratum,  sometimes  called 
the  cutis-plate,  consists  of  several  layers  of  closely  packed  elements.  By  some  these 
cells  are  regarded  as  concerned  in  producing  the  connective  tissue  portion  of  the 
skin  ;  according  to  others  they  are  in  large  part  converted  into  myoblasts,  which,  with 
those  of  the  mesial  stratum,  or  muscle-plate,  give  rise  to  the  voluntary  muscles  of  the 
trunk.      The  genetic  relations  of  the  somite,  therefore,  may  be  expressed  as  follows  : 

I    Myotome — muscle  segment. 

Somite J   Sclerotome — axial  segment. 

(.  Nephrotome — excretory  gland  segment. 

The  number  of  somites  of  the  human  embryo  is  about  thirty-seven,  comprising  eight 
cervical,  twelve  thoracic,  five  lumbar,  five  sacral,  and  from  five  to  seven  caudal 
segments. 

THE    FCETAL    MEMBRANES. 

The  Amnion. — With  the  exception  of  fishes  and  amphibians, — animals  whose 
development  takes  place  in  water, — the  young  vertebrate  embryo  is  early  enveloped 
in  a  protecting  membrane,  the  amnion.  Animals  possessing  this  structure,  including 
reptiles,  birds,  and  mammals,  are  classed,  therefore,  as  amniota,  in  contrast  to  the 
anamnia,  in  which  no  such  envelope  is  formed.     An  additional  fcetal  appendage,  the 

alla/itois,  is  always  developed 
FlG-  36-  as  a   structure    complemental 

to  the  amnion  ;  hence  the  am- 
niota possess  both  amnion  and 
allantois. 

Since  the  development  of 
the  fcetal  membranes  in  man 
presents  certain  deviations 
from  the  process  as  seen  in 
other  mammals,  due  to  pecu- 
liarities affecting  the  early 
human  embryo,  it  is  desirable 
■  cavity  of  blastodermic  to  examine  briefly  the  forma- 
utobiast  vesicle      tion  of  these  structures  as  ob- 

-Ti-ophobiast  served  in  animals  less  highly 

specialized. 

Referring    to    the    early 

Diagram  of  mammalian  blastodermic  vesicle.-  mammalian   embryo,   in  which 

the  blastodermic  layers  are 
arranged  as  somatopleura  and  splanchnopleura  on  either  side  of  the  embryonic  axis 
and  the  surrounding  uncleft  mesoderm,  and  extend  as  parallel  sheets  over  the  en- 
larging blastodermic  vesicle,  the  first  trace  of  the  amnion  appears  as  a  duplicature 
of  the  somatopleura.  The  earliest  indication  of  the  process  is  seen  slightly  in  front 
of  the  cephalic  end  of  the  embryo,  the  resulting  head-fold  being,  however,  soon  fol- 
lowed by  the  appearance  of  the  lateral  and  tail-folds.      The  rapid  growth  of  these 


THE    AMNION. 


3i 


Diagram  showing  formatii 


frophoblast 


folds  and  of  gut-tube  ;  trans- 
f  embryo. 


duplicatures  of  somatopleura  from  all  sides  results  in  the  encircling  of  the  embryo 
within  a  wall  which  increases  in  height  until  the  prominent  edges  of  the  folds  meet 
and  coalesce  over  the  dorsal  aspect  of  the  enclosed  embryo.  The  folds  of  the 
amnion  first  meet  over  the  head-end,  from  which  point  the  union  extends  tailward, 
where,  however,  fusion  may  be  delayed  for  some  time.  The  line  along  which  the 
junction  of  the  folds  takes  place  is  known  as  the  amniotic  suture. 

The  amnion  thus  forms 
a  closed   sac   completely   in-  FlG-  37- 

vesting  the  embryo  and  con- 
taining a  fluid,  the  liquor 
amnii  ;  at  first  closely  sur- 
rounding the  embryo,  the 
amniotic  sac  rapidly  expands 
until  its  dimensions  allow  the 
enclosed  fcetus  to  turn  freely, 
practically  supported  by  the 
amniotic  fluid,  which  pos- 
sesses a  specific  gravity  of 
1003.  It  has  long  been 
known  that  in  certain  forms, 
conspicuously  in  the  chick, 
the  amnion  executes  rhythmi- 
cal contractions,  at  the  rate 
of  ten  per  minute,  whereby 
the  embryo  is  swayed  from 
end  to  end  of  the  sac.  From 
the  manner  of  its  formation, 
as  folds  of  the  somatopleura 
(Figs.  37  and  38),  it  is  evident  that  the  amnion  consists  of  an  inner  ectoblastic  and 
an  outer  mesoblastic  layer. 

The  Serosa,  or  False  Amnion. — Coincident  with  the  fusion  of  the  inner 
layers  of  the  somatopleuric  folds  to  form  the  closed  sac  of  the  amnion,  the  outer 

layers  of  the  same  folds  unite  to 
pIG    3s.  produce  a  second  external   en- 

velope, the  serosa,  or  false  am- 
nion. The  serosa  soon  becomes 
separated  from  the  amnion  by 
an  intervening  space  to  form  the 
primitive  chorion;  the  latter, 
therefore,  consists  of  ectoblastex- 
ternallyand  mesoblast  internally, 
the  reverse  of  the  disposition  of 
these  layers  in  the  amnion. 

The   outer   surface   of    the 
mammalian  primitive  chorion — ■ 
the    outer   envelope    formed   of 
the  serosa  and   the   trophoblast 
— is  distinguished  by  prolifera- 
tion of   the  epithelial  elements, 
which    process    results    in    the 
production  of  more  or  less  con- 
spicuous    projections     or     villi 
fFig.  40),  this  villous  condition 
being    particularly  well  marked 
in  man. 
The    ectoblast   of   the    primitive    chorion    takes    no    part  in    the    formation   of 
the  body  of  the  embryo,   but,   on   the  other  hand,    assumes  an   important  role  in 
establishing  the  earliest  connection  between  the  embryo  and   the  maternal   tissues 
and,    later,    participates   in   the   formation   of   the   placenta.      The  ectoblast   of   the 


32 


HUMAN   ANATOMY. 


Fig.  39. 


primitive  chorion  is  the  direct  derivative  of  the  original  ectodermal  layer  of  the 
blastodermic  vesicle  beyond  the  embryonic  region  proper,  a  layer  which,  on 
account  of  this  important  nutritive  function,  has  been  called  by  Hubrecht  the 
trophoblast. 

As  already  noted  (Fig.  32),  the  cleft  between  the  parietal  and  visceral  layers 
of  the  mesoblast  is  the  primary  body-cavity  or  ccelom  ;  with  the  separation  of  these 
layers  following  the  dorsal  and  the  ventral  folding  associated  respectively  with  the 
formation  of  the  amniotic  sac  and  the  gut-tube,  the  intramesoblastic  .space  becomes 
greatly  expanded  and  extends  between  the  amnion  and  primitive  chorion.  This 
large  space  is  appropriated  only  to  a  limited  extent  by  the  future  definite  body- 
cavity,  and  hence  is  divisible  into  an  embryonic  and  an  extra-embryonic  portion,  or 
exoccelom  (Fig.  38),  which  are  temporarily  continuous. 

The  Vitelline  Sac. — While  the  somatopleura  is  engaged  in  producing  the 
protecting  amniotic  sac,  the  splanchnopleura,  composed  of  the  entoblast  and  the 
adherent  visceral  layer  of  mesoblast,  becomes  approximated  along  the  ventral  sur- 
face of  the  embryo  to  define  the  primitive  gut-tube  by  enclosing  a  part  of  the 
blastodermic  vesicle  ;  the  remaining,  and  far  larger,  portion  of  the  latter  cavity 
constitutes  the  vitelline  sac,  and  corresponds  to  the  yolk-sac  of  the  lower  forms. 

The  constriction  and  separation  of  the  gut-tube  from  the  vitelline  sac  is  accom- 
plished earliest  at  the 
cephalic  and  caudal  ends 
of  the  future  alimentary 
canal,  the  intervening  por- 
tion remaining  for  a  time 
in  widely  open  communi- 
cation with  the  yolk-sac. 
During  the  rapid  diminu- 
tion of  the  latter  the  com- 
munication becomes  re- 
duced to  a  narrow  channel, 
the  vitelline  duct,  which 
persists  as  a  slender  stalk 
terminating  at  its  distal  end 
in  the  remains  of  the  yolk- 
sac. 

In  animals  other  than 
mammals  in  which  a  pla- 
centa is  developed,  the 
yolk-sac  is  the  chief  nutri- 
tive organ  of  the  embryo  ; 
the  mesoblastic  tissue  of 
the  vesicle  becomes  vascu- 
larized by  the  development 
of  the  blood-vessels  consti- 
tuting the  vitelline  circulation,  of  which  the  vitelline  or  omphalomesenteric  arteries 
and  veins  form  the  main  trunks.  The  contents  of  the' yolk-sac  as  such  do  not 
directly  minister  to  the  nutrition  of  the  embryo,  but  only  as  materials  absorbed  by 
the  vitelline  blood-vessels.  In  man  and  other  high  mammals  the  nutritive  function  of 
the  yolk  is  at  best  insignificant,  the  vitelline  sac  of  these  animals  representing  the 
more  important  organ  of  their  humbler  ancestors.  In  the  lowest  members  of  the 
mammalian  group,  the  monotremata,  in  which  the  large  ova  are  comparatively  rich 
in  deutoplasm,  the  vitelline  circulation  is  of  great  importance  for  respiration  and  nu- 
trition, since  it  constitutes  the  means  for  the  performance  of  these  functions  until  the 
immature  animals  are  transferred  to  the  marsupial  pouch  to  complete  their  develop- 
ment. In  the  kangaroo  and  opossum  the  yolk-sac  at  one  point  forms  a  disk-like 
organ,  which,  from  the  fact  that  it  becomes  provided  with  vascular  villi  that  lie  in 
contact  with  the  uterine  mucous  membrane,  is  termed  the  vitelline  placenta. 

The  Allantois  and  the  Chorion. — Coincidently  with  the  formation  of  the 
amnion,  another  foetal  appendage,   the  allantois,   makes  its  appearance  as  an  out- 


l  Manning  allantois  and 


THE    VITELLINE    SAC.  33 

growth  from  the  caudal  segment  of  the  primary  gut-tract.  Although  modified  in 
man  and  certain  mammals  to  such  an  extent  that  its  typical  form  and  relations  are 
obscured,  the  allantois,  when  developed  in  a  characteristic  manner,  as  in  the  chick, 
assumes  the  appearance  of  a  free  vesicle  connected  with  the  embryo  near  its  caudal 
pole  by  means  of  a  narrow  pedicle,  the  allantoic  stalk.  Since  the  allantois  is  an 
evagination  from  the  primitive  gut,  its  walls  are  formed  by  direct  continuations  of 
the  primary  layers  enclosing  the  digestive  canal, — namely,  a  lining  of  entoblastic 
cells,  reinforced  externally  by  a  layer  of  visceral  mesoblast. 

Beginning  as  a  wide  bay  on  the  ventral  wall  of  the  hind-gut,  the  allantois  elon- 
gates and  appears  as  a  pyriform  sac  projecting  from  the  embryo  behind  the  attach- 
ment of  the  still  large  vitelline  stalk  (Fig.  39).  It  rapidly  grows  into  the  exoccelom, 
and  in  mammals  expands  in  all  directions  until  it  comes  into  contact  with  the  inner 
surface  of  the  primitive  chorion,  with  which  it  fuses  to  constitute  the  true  chorion. 
The  latter,  sometimes  spoken  of  as  the  allantoic  chorion  in  contrast  to  the  amniotic 
or  primitive  chorion,  now  becomes  the  most  important  envelope  of  the  mammalian 
embryo  on  account  of  the  role  that  it  is  destined  to  play  in  establishing  the  respira- 


Amniotic  sac 


Vitelline  sac 
Diagram  showing  villous  condition  of  serosa,  expanding  allantois,  and  diminishing  vitelline  sac. 

tory  and  nutritive  organ  of  the  fcetus,  the  placenta.  After  the  fusion  of  the  allantois 
with  the  primitive  chorion  to  form  the  chorion,  the  villous  projections  upon  the 
external  surface  of  the  latter  become  more  highly  developed,  consisting  of  a  core  of 
mesoblastic  tissue  covered  externally  by  the  ectoblast. 

The  primary  purpose  of  the  allantois,  as  a  receptacle  for  the  effete  materials  ex- 
creted by  the  Wolffian  body  of  the  early  fcetus,  is  soon  overshadowed  by  its  function 
as  a  respiratory  organ  ;  this  occurs  with  the  appearance  of  the  rich  vascular  supply 
within  the  chorion  following  the  invasion  of  its  mesoblastic  tissue  by  the  blood-vessels 
constituting  the  allantoic  circulation.  The  latter  includes  the  two  allantoic  arteries, 
which  are  extensions  from  the  aortic  stem  of  the  embryo  and  convey  venous  blood, 
and  the  two  allantoic  veins,  which  return  the  oxygenated  blood  to  the  embryo  and 
become  tributary  to  the  great  venous  segment  of  the  primitive  heart.  The  vascu- 
larization of  the  chorion  extends  to  the  highly  developed  villi  occupying  its  outer 
surface  in  many  mammalian  forms,  especially  man. 

The  vascular  villi  of  the  chorion,  bearing  the  terminal  loops  of  the  blood-vessels 
conveying  the  fcetal  blood,  are  important  structures  on  account  of  their  intimate 
relations  with  the  uterine  mucous  membrane  (Fig.  41),  in  conjunction  with  which 

3 


34 


HUMAN    ANATOMY. 


they  form  a  respirative  and  nutritive  apparatus.  The  intimacy  between  the  uterine 
mucous  membrane  and  the  chorionic  tufts  presents  all  degrees  of  association,  from 
simple  apposition,  as  seen  in  the  sow,  where  the  feebly  developed  and  almost  uni- 
formly distributed  vascular  projections  are  received  within  corresponding  depressions 
in  the  richly  vascular  uterine  tissue,  to  the  firm  and  complex  attachment  found  in  the 
highly  developed  human  placenta. 


Fig.  41. 


Villi  of  extraplacental  chorion 
Gut-tube 


Mesoblast 

Entoblast 


-Allantois 

Allantoic  blood- 
-Allantoic  sac 


Maternal  blood-spaces 


""Decidua  placentalis 
Diagram  showing  villous  chorion,  differentiation  of  placental  area,  and  vascularization  of  chorion. 

In  contrast  with  the  chorion  of  those  animals  in  which  the  nutritive  relations 
between  the  maternal  tissues  and  the  embryo  are  uniformly  distributed  are  the  local 
specializations  seen  in  the  chorion  of  those  types  in  which  a  placental  area  is  de- 
veloped. The  animals  in  which  the  latter  condition  obtains  are  known  as  placentalia, 
of  which  three  subgroups  are  recognized  depending  upon  the  multiple  (cotyledons), 

Fig.  42. 


^-~^tN 


^rs^ft 


lustrating  the  various  types  of  development  of  the  chorion.  A,  uniformly  developed  villi  (hog, 
horse)  ;  B,  multiple  placenta?  or  cotyledons  (cow,  sheep) ;  C,  zonular  placenta  (cat,  dog)  ;  D,  discoidal  placenta 
(monkey,  man).    A-B  comprise  non-deciduate  ;   C-D.  deciduate  mammals. 


zonular,  or  discoidal  form  of  the  placenta,  man  and  the  apes  representing  the  highest 
specialization  of  the  last  division.  In  its  general  plan  of  development,  therefore,  the 
placenta  is  formed  of  a  fatal  and  a  maternal  portion,  the  former  consisting  of  the 
vascular  villi  which  are  unusually  well  developed  within  a  particular  portion  of  the 
chorion,  and  the  latter  of  the  opposed  uterine  lining  which  becomes  highly  special- 
ized throughout  a  corresponding  area  and  more  or  less  intimately  united  with  the 


THE    HUMAN    FCETAL    MEMBRANES.  35 

fcetal  structures.  The  mucous  membrane  of  the  entire  uterine  cavity,  in  many  of  the 
higher  mammals,  suffers  profound  change,  and  before  the  end  of  gestation  becomes 
inseparably  attached  to  the  chorion  even  in  its  extent  beyond  the  placental  area  ;  in 
such  animals  the  fused  uterine  and  chorionic  tissue  constitute  the  decidna  which, 
lined  internally  by  the  closely  applied  amnion,  form  the  membranous  envelope  en- 
closing the  foetus.  After  rupture  consequent  upon  the  expulsion  of  the  foetus  at  the 
termination  of  pregnancy,  the  deciduse,  including  the  specialized  placental  portion, 
are  separated  from  the  uterine  wall  and  expelled  as  the  membranes  and  the  placenta 
which  are  known  collectively  as  the  after-birth. 

The  foregoing  sketch  of  the  general  development  of  the  foetal  membranes  in 
the  higher  mammals  must  be  now  supplemented  by  consideration  of  the  peculiarities 
encountered  in  the  development  of  these  structures  in  man. 

THE    HUMAN    FCETAL    MEMBRANES. 

The  young  human  embryo  is  distinguished  by  the  very  early  formation  of  the 
amniotic  cavity,  by  the  precocious  development  of  the  mesoblast  and  extra- 
embryonic coelom,  by  the  presence  of  the  body-stalk  and  by  the  great  thickening  of 
the  trophoblast.  It  must  be  remembered,  in  considering  the  formation  of  the  human 
foetal  membranes,  that  the  earliest  stages  of  development,  to  wit,  fertilization, 
segmentation,  the  formation  of  the  blastodermic  vesicle,  the  earliest  differentiation  of 
the  embryonic  area  and  the  formation  of  the  amniotic  cavity  have  not  yet  been 
observed  on  human  specimens.  Our  knowledge  of  these  processes  is  derived  from  a 
study  of  some  of  the  lower  types  ;  beyond  these  very  early  stages,  however,  the 
conditions  in  the  human  embryo  have  been  subject  to  direct  study. 

The  Human  Amnion,  Amniotic  Cavity  and  Allantois. — The  accompany- 
ing diagrams  (Fig.  43)  will  serve  to  illustrate  the  process  of  formation  of  the  foetal 
membranes  in  man.  Of  these  five  diagrams,  A  alone  is  purely  hypothetical  with 
reference  to  the  human  embryo.  In  diagram  A  the  amniotic  cavity  is  already 
indicated  as  a  small  cleft  between  the  embryonic  area  below  and  a  covering  layer  of 
cells  above  continuous  with  the  trophoblast.  This  layer,  the  trophoblast,  forms  the 
outer  covering  of  the  entire  vesicle.  It  is  presumably  already  thickened  at  as  early 
a  stage  as  this  diagram  represents.  Presumably  also  the  surface  of  the  trophoblast 
shows  irregularities,  for  this  tissue  it  is  which  comes  into  direct  contact  with  the 
uterine  mucous  membrane  and  which,'  by  its  activities,  forces  its  way  into  the 
maternal  decidua.  This  latter  process  is  known  as  implantation,  a  process  which 
supposedly  is  taking  place,  if  not  completed,  at  about  the  stage  of  this  diagram. 
Whether  the  trophoblastic  layer  in  man  is  originally  a  thin  single  sheet  of  cells,  as 
for  instance  is  the  case  in  the  rabbit,  or  whether  it  is  from  the  beginning  thickened, 
we  do  not  know.  Certainly  the  thickened  condition  appears  at  a  very  early  stage. 
The  embryonic  area  shows  the  embryonic  ectoblast  proper,  which  is  of  small  extent ; 
this  ectoblast  being  so  distinguished  from  the  trophoblastic  ectoblast.  The  ento- 
blast  beneath  is  represented  as  already  arranged  in  the  form  of  a  sac.  Between  the 
entoblast  and  ectoblast  the  mesoblast  has  made  its  appearance.  It  will  be  noted 
that  in  the  diagram  the  entoblastic  sac  is  much  smaller  than  the  outer  trophoblastic 
vesicle.  We  do  not  know  that  this  is  really  the  condition  when  the  entoblastic  sac 
is  first  formed  or  only  appears  in  conjunction  with  the  great  development  of  the  extra 
embryonic  ccelom  in  the  mesoblast.  It  is  certainly  not  unreasonable  to  suppose  that 
the  former  case  is  the  true  one. 

The  early  appearance  of  the  amniotic  cavity  is  to  be  explained  in  this  way. 
After  the  blastodermic  vesicle  has  reached  the  stage  when  the  inner  cell  mass  is 
attached  to  one  point  on  the  inner  surface  of  the  trophoblast,  the  formation  of  a 
cavity  occurs  in  the  region  of  the  inner  mass.  This  cavity,  at  first  very  small,  has 
below  it  the  cells  of  the  inner  mass,  which  soon  become  arranged  into  the  two 
primary  germ  layers  of  the  embryonic  area,  ectoblast  and  entoblast,  while  above 
the  cavity  is  a  layer  of  cells  continuous  with  the  trophoblast.  Such  a  method 
of  formation  of  the  amniotic  cavity  has  been  observed  in  some  of  the  lower 
forms,  for  instance,  by  Hubrecht,  in  the  hedge  hog,  and  since  the  earliest  human 
embryo  accurately   studied  shows  a  completely   closed   amniotic   cavity,    while  in 


36 


HUMAN    ANATOMY. 


a  very  early  stage  of  development    it  is  a  reasonable  inference  that  in  man  such 
a  process  actually  occurs. 

In  diagram  B  the  mesoblast  has  not  only  surrounded  the  entoblastic  sac  and 
the  inner  surface  of  the  trophoblast,  so  enclosing  the  large  extra-embryonic  ccelom, 
but  has  invaded  the  layer  of  cells  above  the  amniotic  cavity,  dividing  this  layer  into 
two  parts,  the  inner  part  going  to  form  the  ectoblast  of  the  amnion,  the  outer  part 
being  a  continuation  of  the  trophoblast  of  the  chorion.  There  is  here  evidently  a 
very  great  development  of  the  extra-embryonic  ccelom.  In  explanation  of  this 
condition,  it  may  be  assumed  that  the  entoblastic  sac  is  at  first  much  smaller  than  the 
trophoblastic  covering  of  the  vesicle  ;   that  the  mesoblast,  shortly  after  its  appearance, 

Fig.  43. 


Diagrams  illustrating:  development  of  human  fcetal  membranes.  Stage  A  is  hypothetical ;  others  are  based  on 
stages  which  have  been  actually  observed.  Red  represents  trophoblast;  purple,  embryonic  ectoblast;  gray,  meso- 
blast;  blue,  entoblast.  ac,  amniotic  cavity;  a/,  allantois  ;  am,  amnion;  6,  body-stalk;  ch,  chorion;  ee.  embryonic 
ectoblast;   en,  entoblast;  g,  gut-tube;  m,  mesoblast ;  p,  placental  area;  /.trophoblast;  v,  yolk-sac ;  vs,  yolk-stalk. 

develops  a  ccelom  ;  that  the  two  layers  of  the  mesoblast  so  formed  grow  separately 
around  the  vesicle  ;  the  splanchnic  layer  around  the  entoblast,  the  somatic  layer 
around  the  trophoblast,  so  enclosing  between  them  as  they  grow,  the  considerable 
space  which  becomes,  by  this  process,  extra-embryonic  body  cavity.  This  diagram 
corresponds  roughly  to  the  condition  of  Peters'  embryo  (Fig.  44).  The  trophoblast 
is  greatly  thickened  ;  its  outer  surface  very  irregular,  showing  lacunae  or  spaces 
filled  with  maternal  blood.  This  early  intimate  contact  of  the  fcetal  tissue  with  the 
maternal  blood  permits  nutrition  of  the  young  embryo  from  the  maternal  blood  to  be 
carried  on  through  the  trophoblast  cells  some  time  before  the  allantoic  circulation 
and  definite  placenta  are  established.      Hence  the  significance  of  this  term  trophoblast. 


THE    HUMAN    FCETAL    MEMBRANES.  37 

In  the  next  diagram,  (Fig.  43),  C,  the  extra-embryonic  coelom  has  invaded  the 
sheet  of  mesoblast  above  the  amniotic  cavity  to  such  an  extent  that  the  chorion  is 
completely  separated  from  the  amnion  and  the  body  of  the  erhbryo  except  at  one 
point,  the  posterior  end  of  the  body,  where  a  solid  stalk  of  mesoblast  connects 
the  chorion  and  embryo.  This  solid  band  of  mesoblast  is  called  the  body-stalk. 
It  represents,  therefore,  a  primary  and  permanent  connection  between  the  chorion 
and  the  body  of  the  embryo.  A  small  diverticulum  from  the  entoblastic  sac  growing 
into  the  mesoblast  of  the  body-stalk  marks  the  beginning  of  the  allantois.  As  the 
diagram  shows,  the  amnion  is  at  first  a  comparatively  small  membrane  overlying  the 
embryonic  area.  The  ectoblast  of  the  amnion  is  on  the  inner  side  facing  the  embryo, 
the  mesoblast  on  the  outer  side.  In  the  chorion  these  layers  are  placed  inversely, 
the  mesoblast  on  the  inner  side,  the  ectoblast  (trophoblast)  outside.  The  space 
between  amnion  and  chorion  is  seen  to  be  a  continuation  of  the  extra-embryonic 
ccelom. 

In  diagram  D,  the  amnion  has  become  considerably  expanded  in  association 
with  the  growth  of  the  body  of  the  embryo  and  the  accumulation  of  amniotic  fluid. 
A  constriction  in  the  entoblastic  sac  has  made  its  appearance,  a  constriction  which 
separates  the  gut  of  the  embryonic  body  from  its  appendage,  the  yolk-sac,  the 
narrower  connecting  piece  being  known  as  the  yolk-stalk,  or  sometimes  as  the 
vitello-intcstinal  duct.  This  constricted  area  is  brought  about  b)'  the  rapid  growth  of 
the  body  of  the  embryo.  In  the  early  condition  the  entoblastic  sac  is  attached  to 
the  embryonic  body  practically  along  its  entire  ventral  surface.  The  body  region 
grows  very  rapidly,  particularly  the  head  end,  which  comes  to  project  from  the 
entoblastic  sac  to  a  marked  extent ;  the  tail  end  also  projects  somewhat.  There  is  a 
corresponding  growth  of  the  gut  within  the  body  of  the  embryo.  As  a  consequence 
of  this  process  of  expansion  of  the  body,  the  area  of  attachment  of  the  entoblast 
external  to  the  body  becomes  relatively  much  reduced  in  size,  occupying  only  a 
small  portion  of  the  ventral  surface  of  the  body,  and  a  progressively  smaller  portion 
as  the  body  increases  in  bulk.  In  other  words,  the  narrow  area  of  the  yolk-stalk 
makes  its  appearance. 

In  the  diagram  (D,  al)  the  allantois  projects  from  the  posterior  end  of  the 
embryonic  gut  into  the  body-stalk.  It  will  be  noticed  that  the  human  allantois  is 
never  a  free  structure  as  it  is  in  many  of  the  lower  types,  where  it  grows  from  the 
body  freely  into  the  extra-embryonic  ccelom  and  only  later  becomes  connected  with 
the  chorion  to  form  the  placenta,  but  that  in  man  it  grows  directly  into  the  body- 
stalk,  where,  outside  of  the  body  of  the  embryo,  it  is  an  insignificant  structure. 
Inside  the  body,'  part  of  the  allantois  persists  as  the  bladder.  The  urachus,  a  fibrous 
cord  which  in  the  adult  passes  from  the  top  of  the  bladder  to  the  umbilicus,  is  also  a 
remnant  of  the  allantois.  The  thick  irregular  projections  of  the  trophoblast  have 
received  a  core  of  mesoblast  tissue,  so  forming  the  early  chorionic  villi.  These  villi, 
at  the  point  of  attachment  of  the  body-stalk,  the  area  where  the  placenta  is 
developing,  are  increasing  in  size,  while  the  villi  over  the  remainder  of  the  chorion 
are  diminishing  in  size. 

In  diagram  £,  the  amnion  has  become  greatly  expanded.  It  lies  closer  to  the 
inner  surface  of  the  chorion.  In  close  association  with  this  expansion  of  the  amnion, 
and  the  accompanying  growth  of  the  body  of  the  embryo,  the  structures  which  form 
the  umbilical  cord  .are  so  closely  approximated  that  the  area  of  the  cord  is  clearly 
defined.  These  structures  are  the  body-stalk  containing  the  allantois  and  allantoic 
vessels,  the  yolk-stalk,  and,  bounding  the  other  side  of  this  area,  the  fold  of  the 
amnion  from  beneath  the  head.  At  first  the  body-stalk  projects  from  beneath 
the  extreme  posterior  end  of  the  body  of  the  embryo,  but  as  growth  in  this  part  of 
the  body  advances  and  the  tail  projects  more  and  more,  the  body-stalk  is  brought  to 
the  ventral  surface  of  the  abdominal  region  in  close  proximity  to  the  yolk-stalk. 
The  allantoic  blood-vessels  grow  from  the  embryo  through  the  body-stalk  to  the 
chorion,  where  they  ramify  in  the  chorionic  villi.  At  first  there  is  an  extension  of 
the  ccelom  about  the  yolk-stalk  in  the  umbilical  cord,  but  the  mesoblast  tissues  of  the 
structures  of  the  cord  soon  fuse  together,  obliterating  this  cavity.  The  area  of  attach- 
ment to  the  abdomen  of  the  umbilical  cord  becomes  relatively  very  much  reduced  in 
size  and  is  known  in  the  adult,  after  the  separation  of  the  cord,  as  the  umbilicus 
or  navel. 


38 


HUMAN    ANATOMY. 


The  chorionic  villi  at  the  point  of  attachment  to  the  chorion  of  the  body-stalk 
are  enlarged.  These  villi  constitute  the  fcetal  portion  of  the  placenta,  the  so-called 
chorion  frondosum.  They  are  imbedded  in  the  maternal  decidua,  more  specifically, 
the  decidua  basalis  or  placentalis.  It  must  be  remembered  that  the  villi  contain  a 
core  of  mesoblast  tissue  in  the  stage  represented  by  diagram  E,  although  this  meso- 
blastic  core  is  not  shown  in  the  figure,  and  that  the  allantoic  blood-vessels  run  in 

Fig.  44. 

Comp.     Ca      B.  Z.        Tr.   g. 

:         1  m. 

I  ■  -  '     ;      II         / 


/,.... 


/ 


•■  %£    "A 

hWi 

I 

..,  •?  3 

=g  .7 

.-'&• 

-%\ 

"  ?*•'' 

ir\ 

--'%{ 

'     \ 

*$u 

Tr.  Af.  Ca.       g. 


Section  of  mucous  membrane,  decidua,  of  a  pregnant  uterus  containing  imbedded  in  it  an  extremely  young 
human  embryonic  vesicle,  described  by  Peters,  a,  6,  points  of  entrance  of  embrvonic  vesicle  ;  B.  L.,  blood  lacuna?  ; 
B.  Z.,  Bordering  zone;  Ca.,  capillary  in  uterine  tissue;  Cap.,  beginning  of  decidua  capsularis ;  Comp..  compact 
tissue  of  uterine  mucosa;  E.,  embryo;  g.,  gland  of  uterus  :  M .  mesoblast ;  Sy..  syncytium  ;  T.  M.,  covering  tissue 
over  break  in  uterine  surface;    Tr.,  trophobiast ;   U.  E.,  epithelium  of  uterine  mucosa.     X  50  {Peters). 


this  mesoblast:  also  that  the  villi  are  in  reality  considerably  branched,  not  straight 
as  in  the  diagram.  The  remainder  of  the  chorion  is  acquiring-  a  smooth  surface  and 
is  commonly  known  as  the  chotio?i  lesve,  as  a  means  of  distinguishing  the  extra- 
placental  portion  of  this  membrane.  The  yolk-sac,  sometimes  called  the  umbilical 
vesicle,  at  the  extremity  of  the  yolk-stalk,  is  retained  usually  in  the  placental  area 
just  beneath  the  amnion.      It  is  possible  to  find  the  yolk-sac  in  nearly  every  placenta 


THE    HUMAN    FCETAL    MEMBRANES. 


39 


by  slightly    stretching   the    umbilical   cord  at   its    insertion,   when    a    fold   appears 
containing   no   large   vessels.      This   fold  points   to   the    position  of    the    yolk-sac. 

To  sum  up,  the  chief  peculi- 
arities of    the   human   fcetal  mem-  Fig.  45. 
branes  are  the  following  : 

1.  The  amniotic  cavity  is  Vitelline  sac — 
developed  at  a  very  early  period 
apparently  by  a  process  of  hollowing 
out  in  the  region  of  the  cells  of  the 
inner  mass,  and  not  by  any  folding 
process.  The  cells  above  this  primi- 
tive amniotic  cavity  are  later  split 
into  two  portions  by  the  entrance  of 
the  mesoblast  and  extra-embryonic 
ccelom  ;  the  inner  portion  becomes 
the  ectoblast  of  the  amnion,  the 
outer  portion  is  merely  a  part  of  the 
the  trophoblast  of  the  chorion. 

2.  The  mesoblast  and  extra- 
embryonic ccelom  are  precociously 
developed  at  a  very  early  period. 

3.  The  body-stalk  constitutes 
a  primary  and  permanent  connection 
between  the  embryo  and  the  chorion. 

4.  The  allantois,  which,  ex- 
ternal to  the  body  of  the  embryo,  is 
an  insignificant  structure,  grows 
into  the  body-stalk  and  therefore  is 
never  a  free  vesicle. 

5.  The  trophoblast  is  very  early  greatly  proliferated  and  very  early  in  intimate 
contact  with  the  maternal  blood. 

Fig.  46. 


Medullary  fold: 
Medullary  groovt 


urenteric  canal 


Chorion . 
Chorionic  villi- 


Dorsal  surface  of  early  human 


Spee.)     The  amnion  has  been  divided 


Wall  of  vitelline 


preceding  figu 


X  23.     {After  Spe 


Longitudinal  section  of  human  embryo  represented  i 

Fig.  44,  page  38,  is  a  reproduction  of  the  drawing  of  Peter's  embryo  and 
deserves  special  attention.  The  figure  shows  a  small  portion  of  the  mucous  mem- 
brane  of  the  uterus  in   which    is  "imbedded   the   embryonic   or   chorionic   vesicle. 


4o  HUMAN    ANATOMY. 

Between  the  points  a,  b  in  the  figure  lies  the  area  through  which  the  embryonic 
growth  has  made  its  way  into  the  mucous  membrane  of  the  uterus,  and,  in  consequence, 
the  uterine  epithelium  in  this  area  has  disappeared.  Above  this  small  area  there 
lies  a  covering  mass  of  tissue  (  Z!  M.')  mainly  composed  of  blood,  the  result  evidently 
of  hemorrhage  following  the  breaking  of  the  mucosa  of  the  uterus  in  this  region. 
The  chorionic  vesicle  as  a  whole  is  quite  large,  especially  in  proportion  to  the 
embryonic  area  E,  the  surface  of  which  is  covered  with  a  distinct  columnar  epithelium. 
Surrounding  the  chorionic  vesicle  there  are  two  kinds  of  tissue,  which  make  a  very 
striking  feature  of  the  picture.  First,  there  is  the  thickened  and  very  irregular 
trophoblast,  the  cells  of  which  appear  dark,  and  which  forms  the  outer  covering  of  the 
wall  of  the  embryonic  vesicle  itself.      Then  there  are  numerous  large  blood-spaces  or 

Fig.  47. 


Umbilical  or  yolk-sac  - 


Body-stalk  - 


Human  embryo  of  about  twenty  days,  enclosed  within  the  amnion.     X  30. 

blood-lacunse  lying  among  the  irregular  projections  of  the  trophoblast.  The  maternal 
blood,  therefore,  in  this  very  early  condition  bathes  the  trophoblast  cells  of  the 
embryo,  a  relation  very  significant  with  reference  to  the  nutrition  of  the  embryo 
before  the  allantoic-placental  circulation  is  established.  The  mesoderm  (M)  extends 
around  the  vesicle  on  the  inner  side  of  the  trophoblast.  In  several  places  there  are 
outgrowths  of  the  mesoderm  into  the  trophoblast,  so  indicating  the  beginnings  of  the 
villi  of  the  chorion.  It  will  be  remembered  that  the  cells  of  the  trophoblast  form  the 
epithelial  covering  of  the  chorion.  At  several  places  in  the  figure  the  syncytial 
layer  of  the  trophoblast  Sy  can  be  distinguished.  The  proportionally  large  cavity 
within  the  vesicle  is  extra-embryonic  ccelom,  a  fact  which  can  readily  be  verified  by 
observing  the  relations  of  the  mesoderm.  The  latter  layer  of  tissue  is  seen  to  extend 
around  the  small  yolk  sac  as  the  visceral  layer  of  the  mesoderm,  while  the  layer  of  the 
mesoderm  on  the  inner  side  of  the  trophoblast  is  of  course  the  parietal  layer,  hence 
the  cavity  within  these  respective  layers  is  the  extra-embryonic  ccelom,  precociously 
developed  for  this  early  stage.  There  is  a  small  amniotic  cavity  above  the  embryo. 
Between  this  cavity  and  the  trophoblast  the  mesoderm  extends  as  a  solid  sheet. 
There  are  one  or  two  more  points  to  be  noted  in  the  figure.      In  the  areas 


THE    HUMAN    CHORION. 


4i 


Extraplacental  area 
{Chorion  lave) 


f 


marked  B.  Z.,  which  are  merely  portions  of  the  uterine  mucosa  lying  against  the 
trophoblast,  the  tissue  is  oedematous  in  character.  This  tissue  is  described  by  Peters 
as  the  bordering  zone.  In  other  portions  of  the  mucous  membrane  there  are  seen 
parts  of  some  of  the  uterine  glands  (_g).  In  the  region  marked  Cap.,  is  seen  the 
beginning  of  the  decidua  capsularis,  growing  in  over  the  area  through  which  the 
embryonic  vesicle  broke  into  the  surface  of  the  uterus.  This  layer,  decidua  capsu- 
laris, is  at  this  stage  scarcely  developed,  only  the  beginning  of  it  is  apparent. 

This  embryo,  described  by  Peters,  is  the  youngest  human  embryo  which  has 
been  accurately  studied.  The  inner  dimensions  of  the  vesicle,  as  given  by  Peters, 
are  as  follows  :  1.6  by  o.  S  by  0.9  mm.  The  growth  was  found  on  the  dorsal  wall 
of  the  body  of  the  uterus.  The  mucous  membrane,  decidua,  of  the  fundus  and 
dorsal  wall  was  about  8  mm.  thick,  that  of  the  ventral  wall  about  5  mm. 

The   Human    Chorion. — The  vascular  chorionic  villi,    although  becoming 
more  complex  by  the  addition  of  secondary  branches,  are  for  a  time  equally  well 
developed  over  the  external  surface  of  the  entire  embryonic  vesicle  ;  subsequently, 
from  the  end  of  the  second  month,  a  noticeable  differentiation  takes  place,  the  villi 
included  within  the  field  that  later  corre- 
sponds to  the  placental  area  undergoing  Fig.  48. 
unusual  growth  and  far  outstripping  those                                           .^       ■•■.    .?_, 
covering  the  remaining  parts  of  the  chorion.  -    *    t    •' 
This  inequality  in  the  development  of  the 
villi  led  to  the  recognition  of  the  chorion 
frondosum  and  the  chorion  lave,   as  the 
placental  and  non-placental  portions  of  the 
chorion  respectively  are  termed  (Fig.  48). 
The  vascular  supply  of  the  villi  also  shares 
in  this  differentiation,  the  vessels  to  those 
of  the  placental  area  becoming  progres- 
sively more  numerous,  while,  on  the  con- 
trary,  those  distributed  to  the  remaining 
villi    gradually    atrophy    as    the    chorion 
comes   into   intimate   apposition  with   the 
uterine  tissue.      When  well  developed,  the 
chorionic  villi  possess  a  distinctive  appear- 
ance,   the    terminal    twigs    of    the    richly 
branched  projections  being   clubbed    and 
slightly  flattened  in  form.      Their  recogni- 
tion in  discharges  from  the  vagina  often 
affords  valuable  information  as  to  the  ex- 
istence of  pregnancy. 

The  Amniotic  Fluid. — The  amnion 
at  first  lies  closely  applied  to  the  embryo, 

but  soon  becomes  separated  by  the  space  which  rapidly  widens  to  accommodate  the 
increasing  volume  of  the  contained  liquor  amnii.  The  accumulation  of  fluid  within 
the  amniotic  sac,  which  in  man  takes  place  with  greater  rapidity  than  in  other  mam- 
mals, results  in  the  obliteration  of  the  cleft  between  the  chorion  and  amnion  until 
the  latter  envelope  lies  tightly  pressed  against  the  inner  surface  of  the  chorion. 
The  union  between  the  two  envelopes,  however,  is  never  very  intimate,  as  even  after 
the  expulsion  of  the  membranes  at  birth  the  attenuated  amnion  may  be  stripped  off 
from  the  chorion,  although  the  latter  is  then  inseparably  fused  with  the  remaining 
portions  cf  the  deciduse. 

The  amniotic  fluid,  slightly  alkaline  in  reaction,  is  composed  almost  entirely 
of  water  ;  of  the  one  per  cent,  of  solids  found,  albumin,  urea,  and  grape-sugar  are 
constituents.  The  quantity  of  liquor  amnii  is  greatest  during  the  sixth  month  of 
gestation,  at  which  time  it  often  reaches  two  litres.  With  the  rapid  increase  in  the 
general  bulk  of  the  foetus  during  the  later  months  of  pregnancy,  the  available  space 
for  the  amniotic  fluid  lessens,  resulting  in  a  necessary  and  marked  decrease  in  the 
quantity  of  the  liquid  ;  at  birth,  less  than  one  litre  of  amniotic  fluid  is  usually 
present.      Sometimes,    however,    the    amount   of    the  liquor  amnii   may  reach   ten 


.;<" 


External  surface  of  part  of  the  human  chorion  of 
the  third  month  ;  the  lower  portion  is  covered  with  the 
highly  developed  villi  of  the  placental  area. 


42  HUMAN    ANATOMY. 

litres,  due  to  pathological  conditions  of  the  fcetal  envelopes  ;  such  excessive  secre- 
tion constitutes  hydramnion.  During  the  later  months  of  pregnancy  the  foetus  swal- 
lows the  amniotic  fluid,  as  shown  by  the  presence  of  hairs,  epithelial  cells,  etc. , 
within  the  stomach.  In  view  of  the  composition  of  the  fluid,  consisting  almost  en- 
tirely of  water,  it  seems  certain  that  the  introduction  of  the  liquor  amnii  does  not 
serve  the  purposes  of  nutrition  ;  on  the  other  hand,  it  is  probable,  as  held  by  Preyer, 
that  the  unusual  demands  of  the  fcetal  tissues  for  water  may  be  met  largely  in  this 
manner. 

The  source  of  the  amniotic  fluid  in  man  has  been  the  subject  of  much  discus- 
sion. While  it  has  been  impossible  to  determine  accurately  the  extent  to  which  the 
mother  participates  in  the  formation  of  this  fluid,  it  may  be  accepted  as  established 
that  the  maternal  tissues  are  the  principal  contributors  ;  it  is  also  probable  that  the 
fcetus  likewise  aids  in  the  production  of  the  liquor  amnii  ;  the  latter,  therefore,  orig- 
inates from  a  double  source, — maternal  and  fcetal.     The  early  amniotic  fluid  resembles 

Fig.  49. 


Umbilical  vesicle 


Umbilical  stalk  - 


Umbilical  cord  - 


Human  embryo  of  about  thirty-three  days.     X  4-     Amnion  and  chorion  have  been  cut  and  turned  aside. 

in  appearance  and  chemical  composition  a  serous  exudate  ;  later,  after  the  formation 
of  the  urogenital  openings,  the  liquor  amnii  becomes  contaminated,  as  well  as  aug- 
mented, by  the  addition  of  the  fluid  derived  from  the  excretory  organs  of  the  fcetus. 
During  the  later  weeks  of  gestation  the  contents  of  the  digestive  tube  are  discharged 
into  the  amniotic  sac  as  meconium. 

The  Umbilical  Vesicle. — The  umbilical  vesicle,  as  the  yolk-sac  in  man  is 
termed,  presents  a  reversed  growth-ratio  to  the  amnion  and  body-stalk  since  it  pro- 
gressively decreases  as  these  latter  appendages  become  more  voluminous.  The  early 
human  embryo  is  very  imperfectly  differentiated  from  the  large  and  conspicuous 
yolk-sac,  with  which  its  ventral  surface  widely  communicates.  With  the  advances 
made  during  the  third  week  in  the  formation  of  the  primitive  gut,  the  connection 
between  the  latter  and  the  vitelline  sac  becomes  more  definitely  outlined  in  conse- 
quence of  the  beginning  constriction  which  indicates  the  first  suggestion  of  the  later 
vitelline  or  umbilical  duct  (Fig.  47).      By  the  end  of  the  fourth  week  the  connection 


THE    UMBILICAL    VESICLE. 


43 


between  the  umbilical  sac  and  the  embryo  has  become  reduced  to  a  contracted  channel 
extending  from  the  now  rapidly  closing  ventral  body-wall  to  the  yolk-sac,  which  is 
still,  however,  of  considerable  size.  The  succeeding  fifth  (Fig.  50)  and  sixth  weeks 
effect  marked  changes  in  the  umbilical  duct,  now  reduced  to  a  narrow  tube,  which 
extends  from  the  embryo  to  the  chorion,  where  it  ends  in  the  greatly  diminished 
vitelline  sac.  The  lumen  of  the  umbilical  duct  is  conspicuous  during  the  earliest 
months  of  gestation,  but  later  disappears,  the  entoblastic  epithelial  lining  remaining 
for  a  considerable  time  within  the  umbilical  cord  to  mark  the  position  of  the  former 
canal. 

The  chief  factor  in  producing  the  elongation  of  the  umbilical  duct  is  the  rapid 
expansion  of  the  amnion  ;  with  the  increase  in  the  amniotic  sac  the  distance  between 
this  envelope  and  the  embryo  increases,  until  the  amnion  fills  the  entire  space  within 

Fig.  50. 


Umbilical 

vesicle, 
(yolk-sac) 


Chorionic  sac  of  thirty-five  day  embryo  laid  open,  showing  embryc 


the  chorion,  against  which  it  finally  lies.  In  consequence  of  this  expansion,  the 
attachment  between  the  embryo  and  the  amnion  around  the  ventral  opening,  which 
later  corresponds  to  the  umbilicus,  becomes  greatly  elongated  and  narrowed.  At 
this  point  the  tissues  of  the  embryonic  body-wall  and  the  amniotic  layers  are  directly 
continuous.  The  tubular  sheath  of  amnion  thus  formed  encloses  the  tissue  and 
structures  which  extend  between  the  embryo  and  the  chorion,  as  the  constituents  of 
the  belly-stalk,  together  with  the  umbilical  duct  and  the  remains  of  the  vitelline 
blood-vessels  ;  the  delicate  mesoblastic  layer  of  the  amnion  fuses  with  the  similar 
tissue  of  the  allantois,  the  whole  elongated  pedicle  constituting  the  umbilical  cord  or 
funiculus.  The  latter  originates,  therefore,  from  the  fusion  of  three  chief  com- 
ponents, the  amniotic  sheath,  the  belly-stalk,  and  the  vitelline  duct  ;  the  belly-stalk. 


44  HUMAN    ANATOMY. 

as  already  noted,  includes  the  allantois,  with  its  blood-vessels,  and  diverticulum, 
while  traces  of  the  vitelline  circulation  are  for  a  time  visible  within  the  atrophied 
walls  of  the  umbilical  duct.  As  gestation  advances,  the  amnion  and  the  chorion 
become  closely  related,  but  not  inseparably  united  ;  between  these  attenuated  mem- 
branes lie  the  remains  of  the  once  voluminous  yolk-sac,  which  at  birth  appears  as 
an  inconspicuous  vesicle,  from  three  to  ten  millimetres  in  diameter,  situated  usually 
several  centimetres  beyond  the  insertion  of  the  umbilical  cord. 

In  cases  in  which  the  closure  and  the  obliteration  of  the  vitelline  duct  before  birth 
are  imperfectly  effected,  a  portion,  or  even  the  whole,  of  the  intra-embryonic  segment 
of  the  canal  may  persist  as  a  pervious  tube.  Although  in  extreme  cases  of  faulty 
closure  a  passage  may  lead  from  the  digestive  tube  to  the  umbilicus,  and  later  open 
upon  the  exterior  of  the  body  as  a  congenital  umbilical  anus,  the  retention  of  the 
lumen  of  the  vitelline  duct  is  usually  much  less  extensive,  being  limited  to  the  prox- 
imal end  of  the  canal,  where  it  is  known  as  Meckel' s  diverticulum.  The  latter  is  con- 
nected with  the  ileum  at  a  point  most  frequently  about  82  centimetres  (thirty-two 
inches)  from  the  ileo-caecal  valve.  Such  diverticula  usually  measure  from  five  to 
7.5  centimetres  in  length,  and  possess  a  lumen  similar  to  that  of  the  intestine  with 
which  they  communicate. 

The  foregoing  envelopes,  the  amnion  and  the  chorion,  are  the  product  of  the 
embryo  itself  ;  their  especial  purpose,  in  addition  to  affording  protection  for  the  deli- 
cate organism,  is  to  aid  in  establishing  close  nutritive  relations  between  the  embryo 
and  the  maternal  tissues,  which,  coincidently  with  the  development  of  the  fcetal 
envelopes,  undergo  profound  modifications  ;  these  changes  must  next  be  considered. 

The  Deciduae. — The  birth  of  the  child  is  followed  by  the  expulsion  of  the 
after-birth,  consisting  of  the  membranes  and  the  placenta,  which  are  separated  from 
the  uterine  wall  by  the  contractions  of  this  powerful  muscular  organ.  Close  inspection 
of  the  inner  surface  of  the  uterus  and  of  the  opposed  outer  surface  of  the  extruded 
after-birth  shows  that  these  surfaces  are  not  smooth,  but  roughened,  presenting  evi- 
dences of  forcible  separation.  The  fact  that  the  external  layer  of  the  expelled  after- 
birth consists  of  the  greater  portion  of  the  modified  mucous  membrane  which  is 
stripped  off  at  the  close  of  parturition  suggested  the  name  decidua  for  the  mater- 
nal portion  of  the  fcetal  envelopes  shed  at  birth. 

Since  the  deciduae  are  directly  derived  from  the  uterine  mucous  membrane,  a 
brief  sketch  of  the  normal  character  of  the  last-named  structure  appropriately  pre- 
cedes a  description  of  the  changes  induced  by  pregnancy.  The  normal  mucous 
membrane  lining  the  body  of  the  human  uterus  (Fig.  51)  presents  a  smooth,  soft, 
velvety  surface,  of  a  dull  reddish  color,  and  measures  about  one  millimetre  in  thick- 
ness. The  free  inner  surface  is  covered  with  columnar  epithelium  (said  to  be  cili- 
ated) which  is  continued  directly  into  the  uterine  glands.  The  latter,  somewhat 
sparingly  distributed,  are  cylindrical,  slightly  spiral  depressions,  the  simple  or  bifur- 
cated blind  extremities  of  which  extend  into  the  deeper  parts  of  the  mucosa  in  close 
relation  to  the  inner  bundles  of  involuntary  muscle  ;  all  parts  of  the  tubular  uterine 
glands  are  lined  by  the  columnar  epithelium.  The  muscular  bundles  representing 
the  muscularis  mucosae  are  enormously  hypertrophied  and  constitute  the  greater 
part  of  the  inner  more  or  less  regularly  disposed  circular  layer  of  the  uterine  muscle. 
The  unusual  development  of  the  muscular  tissue  of  the  mucous  membrane  reduces 
the  submucous  tissue  to  such  an  insignificant  structure  that  the  submucosa  is  gener- 
ally regarded  as  wanting,  the  extremities  of  the  uterine  glands  being  described  as 
reaching  the  muscular  tunic.  The  glands  lie  embedded  in  the  connective-tissue 
complex,  rich  in  connective-tissue  elements  and  lymphatic  spaces,  that  forms  the 
tunica  propria  of  the  mucosa. 

With  the  beginning  of  pregnancy  the  uterine  mucous  membrane  undergoes 
marked  hypertrophy,  becoming  much  thicker,  more  vascular,  and  beset  with  nu- 
merous irregularities  of  its  free  surface  caused  by  the  elevations  of  the  soft  spongy 
component  tissue.  These  changes  take  place  during  the  descent  of  the  fertilized 
ovum  along  the  oviduct  and  indicate  the  active  preparation  of  the  uterus  for  the 
reception  of  the  ovum. 

According  to  the  classical  description  of  the  encapsulation  of  the  ovum  (Fig.  52) 
by  the  uterine  mucous  membrane,  the  embryonic  vesicle  becomes  arrested  within 


THE    DECIDLMi.  45 

one  of  the  depressions  of  the  uterine  lining,  usually  near  the  entrance  of  the  ovi- 
duct, whereupon  the  adjacent  mucosa  undergoes  rapid  further  hypertrophy,  which 
results  in  the  formation  of  an  annular  fold  surrounding  the  product  of  concep- 
tion. This  encircling  wall  of  uterine  tissue  continues  its  rapid  growth  until  the 
embryonic  vesicle  is  entirely  enclosed  within  a  capsule  of  modified  mucous  mem- 
brane, known  as  the  decidua  reflexa,  as  distinguished  from  the  decidua  vera,  the 
name  applied  to  the  general  lining  of  the  pregnant  uterus.  That  portion  of  the 
uterine  mucosa,  however,  which  lies  in  close  apposition  to  the  embryonic  vesicle, 
constituting  the  outer  wall  of  the  decidual  sac,  is  termed  the  decidua  serotina  ;  later 
it  becomes  the  maternal  part  of  the  placenta. 

Fig.  51. 


-Spiral  portion  of 
gland 


-Process  of  muscular 
tissue  extending  be- 


-Mus<  ul. 11  tissue 


-llerine  blood- 


mbrane  with  part  of  muscular  tissue.     X  45- 

Our  knowledge  of  the  details  regarding  the  encapsulation  of  the  ovum  has 
been  materially  advanced  by  the  recent  observations  of  Peters,  who  had  the  rare 
good  fortune  of  carefully  studying  the  details  of  the  process  at  an  earlier  stage  than 
any  hitherto  accurately  investigated.  The  results  of  Peters' s  observations  lead  to  a 
somewhat  modified  conception  of  the  early  phases  of  the  encapsulation  of  the  ovum, 
as  well  as  shed  additional  light  on  some  of  the  vexed  problems  concerning  the  details 
of  the  formation  of  the  placenta. 

According  to  these  investigations,  the  embryonic  vesicle,  on  reaching  the  uterine 


46 


HUMAN    ANATOMY. 


cavity  and  becoming  arrested  at  some  favorable  point,  usually  in  the  vicinity  of 
the  oviduct,  brings  about  a  degeneration  of  the  uterine  epithelium  over  the  area  of 
contact.  The  disappearance  of  the  epithelial  lining  is  followed  by  sinking  and  em- 
bedding of  the  embryonic  vesicle  within  the  softened  mucous  membrane,  the  process 
being  accompanied  by  erosion  of  some  of  the  uterine  capillaries  and  consequent 
hemorrhage  into  the  opening  representing  the  path  of  the  ovum.  The  extravasated 
blood  escapes  at  the  point  of  entrance  on  the  uterine  surface  and,  later,   forms  a 

mushroom-shaped  plug  marking  the 


Fig.  52. 


position  of  the  embedded  ovum. 
The  latter  thus  comes  into  closer 
relations  with  the  maternal  tissues  at 
an  earlier  period  than  was' formerly 
recognized. 

The  Trophoblast. — The  ear- 
liest human  embryonic  vesicle  that 
has  been  accurately  studied, — that 
of  Peters, — while  measuring  only 
1.6  millimetres  in  its  greatest  di- 
ameter, was  already  enclosed  exter- 
nally by  a  conspicuous  ectoblastic 
envelope,  in  places  .5  millimetre 
or  more  in  thickness.  This  thick 
ectoblastic  layer  is  evidently  the  proliferated  trophoblast  (page  31),  a  membrane  so 
designated  to  indicate  the  important  nutritive  functions  which  it  early  assumes. 
Very  early  the  trophoblast  becomes  honeycombed  by  the  extension  of  the 
maternal  vascular  channels  into  the  ectoblastic  tissue  (Fig.  53),  which  consequently 
is  broken  up  into  irregular  epithelial  trabeculse  separating  the  maternal  blood-spaces. 
The  inner  surface  of  the  trophoblastic  capsule  presents  numerous  irregular  depres- 
sions into  which  corresponding  processes  of  the  adjacent  young  mesoblast  project  ; 
this  arrangement  foreshadows  the  formation  of  the  chorionic  villi  which  soon  become 
so  conspicuous  in  the  human  embryonic  vesicle.  Coincidently  with  the  invasion  of 
the  trophoblast  by  the  vascular  lacuna 


Diagrams  representing  relations  of  the  uterine  mucous 
brane  to  the  embryonic  vesicle,  or  ovum,  during  the  embedding 
of  the  latter,  s,  v,  c,  decidua  serotina,  vera,  and  reflexa,  re- 
spectively ;  o,  ovum. 


Fig.  53. 


externally  and  the  penetration  of  the 
mesoblastic  tissue  internally,  the  pe- 
ripheral portions  of  the  ectoblastic 
capsule  undergo  proliferation  and 
extend  more  deeply  into  the  sur- 
rounding maternal  tissues.  In  con- 
sequence of  the  rapid  growth  of  the 
embryonic  vesicle,  that  part  of  the 
hypertrophied  uterine  mucosa  which 
overlies  the  embedded  embryonic 
vesicle  soon  becomes  elevated  and 
projects  into  the  uterine  cavity,  thus 
giving  rise  to  the  structure  described 
as  the  decidua  reflexa,  or,  preferably, 
the  decidua  capsularis. 

The  Decidua  Vera. — The 
changes  which  affect  the  uterine  mu- 
cous   membrane,    the    decidua  vera, 

result  in  great  thickening,  so  that  the  mucosa  often  measures  nearly  a  centimetre  ; 
this  thickening,  however,  is  most  marked  in  the  immediate  vicinity  of  the  embedded 
ovum,  throughout  the  greater  part  of  the  uterus  the  decidua  attaining  a  much  less 
conspicuous  hypertrophy.  Towards  the  cervix  the  mucosa  is  least  affected,  and  at 
the  internal  orifice  of  the  cervical  canal  presents  its  normal  appearance.  Examina- 
tion of  the  decidua  shows  that  the  normal  constituents  of  the  uterine  mucosa  undergo 
hypertrophy  which  results  in  enlargement  of  the  uterine  glands  (Fig.  54),  as  well 
as  in  increase  of  the  intervening  connective-tissue  stroma.  The  enlargement  of  the 
glands  is  not  uniform,  but  is  limited  to  the  middle  and  terminal  or  deeper  parts  of 


ittachment  between  fcetal 
trophoblast  by  maternal 


THE    DECIDUA    VERA. 


47 


the  tubular  depressions  ;  the  inner  portions  of  the  glands,  directed  towards  the  sur- 
face of  the  uterus,  become  elongated  and  lie  embedded  within  a  comparatively 
dense  matrix.  In  consequence  of  these  changes,  the  decidua  in  the  vicinity  of  the 
ovum,  where  the  hypertrophy  is  most  marked,  presents  in  section  two  strata,  an 
inner  compact  and  an  outer  spongy  layer.  The  ciliated  columnar  epithelium  that 
normally  clothes  the  free  surface  of  the  uterus,  and  perhaps  also  the  uterine  glands, 
gradually  disappears,  the  degeneration  beginning  before  the  end  of  the  first  month. 
The  integrity  of  the  cells  lining  the  uterine  glands  is  maintained  for  a  longer  period, 
but  the  glandular  epithelium  likewise,  after  a  time,  suffers,  losing  its  columnar 
character  and  changing  to  small  cubical  or  flattened  elements,  which,  after  appear- 
ing as  shrunken  columns  during  the  fourth  and  fifth  months,  finally  disappear 
during  the  latter  half  of  gestation.  An  important  exception,  however,  is  to  be  noted 
in  the  behavior  of  the  epithelium  lining  the  deeper  portion,  or  the  fundus,  of  the 
glands  next  the  muscular  tissue  ;  the  epithelium  situated  in  this  position  does  not 
participate  in  the  atrophic  changes  above  described,  but  retains  more  or  less  per- 

Fig.  54. 


Enlarged  gland- 


Uterine  muscle 


inr   m 


Section  of  mucous  membrane  lining  body  of  uterus  (decidua  vera) ;  fourth  month  of  pregnancy.     (After  Leopold.} 

fectly  its  normal  condition  to  the  close  of  pregnancy.  After  the  expulsion  of  the 
decidual  portion  of  the  uterine  mucous  membrane,  the  epithelium  remaining  in  the 
fundus  of  the  glands  becomes  the  centre  of  regeneration  for  the  new  lining  of  the 
uterus. 

The  connective-tissue  elements  of  the  matrix  surrounding  the  glands,  especially 
in  the  compact  layer  in  the  vicinity  of  the  ovum,  undergo  active  proliferation,  in 
consequence  of  which  large  spherical  elements,  the  decidtial  cells,  are  produced.  The 
latter,  from  .030  to  .040  millimetre  in  diameter,  in  places  are  so  densely  packed 
that  they  assume  the  appearance  of  epithelium  ;  although  most  typical  and  nu- 
merous in  the  compact  layer,  they  are,  nevertheless,  present  in  the  spongy  stratum, 
in  this  situation  being  more  elongated  and  lanceolate  in  form. 

The  decidua  vera  retains  this  general  character  during  the  first  half  of  preg- 
nancy ;  from  this  time  on,  however,  the  increasing  volume  of  the  uterine  contents 
subjects  the  decidua  to  undue  pressure,  in  consequence  of  which  the  hypertrophied 
mucosa  undergoes  the  atrophic  changes  characteristic  of  the  so-called  second  stage. 
These  include  a  gradual  reduction  in  the  thickness  of  the  decidua  vera  from  nearly 


48 


HUMAN    ANATOMY. 


one  centimetre  to  about  two  millimetres,  the  disappearance  of  the  ducts  and  open- 
ings of  the  uterine  glands,  and  the  conversion  of  the  compact  layer  into  a  dense 
homogeneous  stratum,  in  which  the  tightly  compressed  glands  later  entirely  disap- 
pear. The  spongy  layer,  on  the  contrary,  retains  the  dilated  gland-lumina,  which, 
however,  in  consequence  of  pressure,  are  converted  into  irregular  spaces  arranged 
with  their  longest  dimensions  parallel  to  the  uterine  surface.      The  clefts  next  the 

Fig-  55- 


Blood-space — 

Giant  cell — Sg 


=«=» — Amnion 
—Chorion 
— Decidua  reflexa 


-  Blood-space  of 
compact  layer 


&     Spongy  layer 


Section  through  fcetal  membranes  and  uterus  at  margin  of  the  placenta  ;  sixth  month  of  pregnancy.  {After  Leopold.) 


muscular  tissue  are  clothed  with  well-preserved  epithelium  ;   the  lining  cells  of  those 
towards  the  compact  layer,  on  the  contrary,  early  atrophy  and  disappear. 

The  Decidua  Placentalis. — The  decidua  placentalis,  or  decidua  sei'otina,  being 
destined  to  contribute  the  maternal  portion  of  the  placenta,  undergoes  profound 
changes  which  particularly  affect  the  blood-vessels  of  the  mucosa.  In  addition  to 
the  initial  general  hypertrophy  of  the  mucous  membrane,  which  the  placental  decidua 
shares  in  common  with  other  parts  of  the  uterine  lining,  peculiar  polynucleated  ele- 
ments, the  giant  cells,  make 
pIG_  55  their  appearance  during  the  fifth 

month  ;  by  the  end  of  preg- 
nancy they  are  found  in  large 
numbers  within  the  basal  plate 
and  the  septa  of  the  placenta, 
although  they  are  not  wanting 
within  the  remains  of  the  spongy 
layer.  The  giant  cells  are  par- 
ticularly numerous  in  the  im- 
mediate vicinity  of  the  large 
blood-vessels.  The  relations 
between  the  ingrowing  fcetal 
trophoblastic  tissue  and  the  ma- 
ternal structures  early  become 
so  intimate  within  the  placental 
area  that  especial  modifications 
are  instituted  destined  for  the  production  of  the  vascular  arrangement  by  which  the 
maternal  and  fcetal  blood-streams  are  brought  into  close  relations. 

The  proliferating  trophoblastic  tissue  invades  the  stroma  of  the  mucous  mem- 
brane and  encroaches  upon  the  capillaries  until  the  latter  in  places  become  ruptured, 
allowing  the  escape  of  the  maternal  blood,  which  thus  is  brought  into  direct  contact 
with  the  trophoblast.  The  erosion  effected  by  the  blood,  on  the  one  hand,  and  the 
encroachment  of  the  fcetal  mesoblast,  on  the  other,  gradually  reduces  the  tropho- 
blastic stratum,  which  is  broken  up  into  narrow  epithelial  trabecular  separating  the 
rapidly  enlarging  vascular  lacuna?,   the  primary  representatives  of  the  intervillous 


Sections  of  chorionic  villi 
branches  of  umbilical  artery  a 
aggregations  of  syncytium  {d) 


placenta.  X  170.  o, 
in ;  v,  capillary  vessels 
;resoblastic  stroma  of  vil 


THE   PLACENTA. 


49 


Fig.  57. 


V-~-Ma/S";a 


maternal  blood-spaces  of  the  placenta.  The  active  outgrowth  of  the  mesoblastic 
tissue  of  the  chorion  into  the  trophoblastic  envelope  results  in  the  production  of  the 
characteristic  villous  condition  distinguishing  the  early  human  embryonic  vesicle. 

When  sectioned,  the  well-developed  chorionic  villi  are  seen  to  be  composed  of 
two  portions,  («)  the  central  core  of  gelatinous  connective  tissue,  'containing  nu- 
merous stellate  cells  and  blood-vessels,  repre- 
senting the  fcetal  mesoblast,  and  (6)  the  epi- 
thelial covering  derived  from  the  trophoblast. 
The  investment  of  the  villi  consists  of  two 
layers,  — an  inner  stratum,  next  the  connective- 
tissue  core,  composed  of  low,  distinctly  out- 
lined polyhedral  cells,  the  chorionic  epithe- 
lium, and  an  outer  stratum,  the  syncytium, 
composed  of  an  apparently  continuous  proto- 
plasmic layer,  in  which  nuclei  are  visible,  but 
definite  cell  boundaries  are  wanting.  Irregu- 
larly distributed  aggregations  of  nuclei,  or 
cell-patches  (Fig.  56),  form  slight  elevations 
on  the  surface  of  the  villi.  The  derivation 
of  the  outer  layer,  or  syncytium,  has  been 
the  subject  of  much  discussion  ;  its  close  rela- 
tion to  the  maternal  blood-spaces  suggested  a 
maternal  origin  to  some  investigators,  while 
others  regard  it  as  a  fcetal  production.  The 
observations  of  Peters  on  the  very  early  human 
ovum,  already  mentioned,  conclusively  show 
the  correctness  of  the  latter  view,   and  lhat 

the  syncytium  is  formed  by  the  transformation  of  the  trophoblast  next  the  vascular 
lacunae  (Fig.  58)  ;  the  syncytium,  as  well  as  the  remaining  parts  of  the  villi  of  the 
chorion,  therefore,  is  of  fcetal  origin.  The  epithelium  covering  the  villi  of  the  pla- 
cental area  early  evinces  a  tendency  towards  regression,  and  by  the  fourth  month 
exists  only  as  isolated  patches  ;  during  the  later  stages,  and  particularly  on  the 
larger  villi,  the  layer  of  chorionic  epithelium  disappears,  the  syncytium  remaining 
as  the  sole  attenuated  covering  of  the  connective-tissue  core  of  the  villi.  In  certain 
parts  of  its  extent,  especially  where  it  covers  the  chorion  and  the  decidua  serotina, 


Isolated  tuft  of  chorionic  villi  from  placenta. 


Fig.  58. 


ig? 


Mesoblastic  core  of  fcetal 
Trophoblast 
£T^Z~~~  Syncytium 

pi'}'' — Maternal  blood-space 

|K~  Muscle 

^^Endothelium 
ial  blood-vessel 


Diagr 


as  well  as  upon  some  of  the  villi,  the  syncytium  undergoes  degeneration  and  is 
replaced  by  a  peculiar  layer  of  hyaline  refracting  material  known  as  canalised 
fibrin. 

The  Placenta. — The  placenta  constitutes,  from  the  third  month  of  intra- 
uterine life,  the  nutritive  and  respiratory  organ  of  the  fcetus.  As  seen  at  birth,  it  is 
of  irregular  discoidal  form,  concavo-convex  in  section,  and  measures  from  fourteen 
to  eighteen  centimetres  in  diameter  and  from  three  to  four  centimetres  in  thickness. 

4 


5° 


HUMAN    ANATOMY. 


Its  convex  external  or  uterine  surface  is  rough,  owing  to  the  separation  from  the 
deeper  part  of  the  lining  of  the  uterus  which  has  taken  place  at  the  termination  of 
labor.  This  surface,  moreover,  presents  a  number  of  divisions,  the  cotyledons,  de- 
fined by  deep  fissures.  The  inner  or  fcetal  surface  is  smooth,  being  covered  by  the 
amnion,  and  slightly  concave.  The  weight  of  the  fully  developed  placenta  averages 
about  500  grammes. 

The  position  of  the  placenta  is  determined,  evidently,  by  the  point  at  which  the 
ovum  forms  its  attachment  with  the  maternal  tissues  ;  in  the  majority  of  cases  this 
location  is  at  the  fundus  of  the  uterus  in  the  vicinity  of  the  oviduct,  right  or  left, 
the  orifice  of  which  becomes  occluded  by  the  expansion  of  the  placental  structures. 
Less  frequently  the  placenta  occupies  the  more  dependent  portions  of  the  uterine 
wall  and,  in  exceptional  cases,  its  position  is  in  the  immediate  vicinity  of  the  internal 
mouth  of  the  uterus  ;  in  these  latter  cases  the  placenta  may  partially,  or  even  com- 
pletely, grow  over  the  latter  opening,  thus  constituting  the  grave  condition  known  as 
placenta  praevia.      The  general  constitution  of  the  placenta  (Fig.  59),  as  consisting 


Fig.  59. 

Uterine  blood-vessels 

Ma 

ternal  blood-spaces 

^^ 

Foetal  villi 

\^ 

%.     /r 

^& 

.--7:v     ^Decidua  placentalis 

.    \-— Allantois 

Umbilical  vesicl 


Decidua  capsularis 


Amniotic  sac 


Diagrari 


Intcrdecidual  space 


illustrating  the  relations  of  the  fcetus,  the  membranes,  and  the  uterus  during  the  early  1 
pregnancy. 


of  the  fcetal  and  the  maternal  portions,  has  already  been  sketched  ;  it  now  remains  to 
consider  briefly  the  arrangement  of  these  structures. 

The  foetal  portio?i  of  the  placenta,  the  contribution  of  the  chorion  frondosum, 
soon  becomes  a  mass  of  richly  branching  villi,  the  more  robust  main  stalks  of  which 
are  attached  to  the  maternal  tissue,  while  the  smaller  secondary  ramifications  are 
free,  completely  surrounded  by  the  contents  of  the  maternal  blood-sinuses  in  which 
they  float.  In  all  cases  the  villous  processes  support  the  terminal  loops  of  the  fcetal 
blood-vessels,  the  blood  being  conveyed  to  and  from  the  placenta,  along  the  umbil- 
ical cord,  by  the  umbilical  arteries  and  vein.  Although  coming  into  close  relation, 
the  syncytium  and  the  meagre  connective  tissue  surrounding  the  fcetal  capillaries 
alone  intervening,  the  blood-streams  of  the  mother  and  of  the  child  never  actually 
mingle  ;  the  delicate  septum,  however,  allows  the  free  interchange  of  gases  necessary 
for  the  respiratory  function  as  well  as  the  passage  of  nutritive  substances  into  the 
fcetal  circulation. 


THE    PLACENTA. 


5i 


The  maternal  portion  of  the  placenta  is  contributed  by  that  portion  of  the  uterine 
mucous  membrane  known  as  the  decidua  serotina  ;  its  especial  peculiarities  consist 
in  the  intervillous  blood-spaces,  which  may  be  regarded  as  derivations  from  the 
eroded  maternal  blood-vessels.  As  already  described,  the  trophoblast  and  maternal 
tissues  early  come  into  close  relation,  and  the  capillary  blood-vessels  are  opened  by 
the  invasion  of  the  feetal  tissue,  which  latter,  in  turn,  is  eroded  and  channelled  out 
by  the  maternal  blood  which  escapes  upon  the  rupture  of  the  blood:vessels  of  the 
mucosa.  The  extension  of  the  blood-spaces  thus  originating  constitutes  the  elaborate 
system  of  vascular  lacunae,  or  intervillous  spaces,  forming  so  conspicuous  a  part  of 
the  full)'  developed  placenta. 

In  its  earlier  changes  the  decidua  serotina  closely  resembles  the  decidua  vera, 
presenung  an  inner  compact  and  an  outer  spongy  layer  ;  by  the  middle  of  preg- 
nancy, however,  the  previously  enlarged  glands  have  entirely  disappeared  in  conse- 
quence of  the  atrophy  induced  by  the  increasing  pressure  caused  by  the  augmenting 
volume  of  the  uterine  contents.  .  When  the  placenta  is  detached  from  the  uterus  the 

Fig.  60. 

Stump  of  umbilical  cord 


Villus 


.-Placental  septu 


)ecidua  serotina 
.Line  of  separatic 


Basal  - 
plate 


Spiral  branches  of  uterine  artery  Inner  limit  Arte 

of  muscle 

Section  of  placenta  and  uterus  at  the  seventh  month.     (Ecker.) 

line  of  separation  passes  through  the  junction  of  the  former  spongy  and  compact 
layers  ;  according  to  Webster,  however,  the  separation  occurs  in  the  compact  layer. 
The  condensed  decidual  tissue  closing  in  the  vascular  lacuna,  on  the  one  hand,  and 
covering  the  surface  of  separation,  on  the  other,  constitutes  the  basal  plate.  The 
latter  is  continued  deeply  within  the  placenta  by  connective-tissue  portions,  the  septa 
placenta,  which  extend  between  the  groups  of  chorionic  villi,  forming  the  cotyledons 
visible  on  the  outer  surface  of  the  placenta  as  irregular  lobules  separated  by  deep 
furrows.  These  septa  do  not  reach  as  far  as  the  chorion  except  at  the  margin  of  the 
placenta,  where  they  form,  a  thin  membranous  sheet  beneath  the  chorion,  the  subcho- 
rionic  occludi?ig  plate  of  Waldever.  Large,  round,  multinucleated  elements,  the 
giant  cells,  measuring  from  .04  to  .08  millimetre  in  diameter,  are  present  within  the 
tissue  of  the  maternal  placenta,  especially  within  the  basal  plate  and  the  septa.  At 
the  margin  the  placental  tissue  becomes  directly  continuous  with  the  feetal  mem- 
branes, the  chorion  and  the  decidua  being  closely  united. 

The  numerous  branches  of  the  arteries  supplying  the  uterus  pierce  the  muscular 
tunic  and  gain  the  basal  plate  ;  here  the  arterial  vessels  lose  their  muscular  coat  and 


52 


HUMAN    ANATOMY. 


penetrate  the  placental  septa  as  spirally  directed  channels  of  enlarged  calibre  bounded 
by  endothelial  walls.      After  a  shorter  or  longer  course  within  the  septa,  the  arterial 


Stalk  of  villus 


Intervillous  blood-spaces 


Section  of  larger  villi] 


Intervillous  blood-spaces 


Maternal  blood-vessel 


*  «-v 


-Maternal  blood-space 

-Maternal  blood-vessel 
-Basal  plate 


Section  of  human  placenta  at  end  of  pregnancy.     X  12.     The  fcetal  blood-vessels  have  been  injected  ;  the  maternal 
blood-spaces  appear  as  clear  areas  surrounding  the  sections  of  the  fcetal  villi. 


trunks  open  directly  into  the  intervillous  or  intraplacental  blood-spaces  which  are 
limited  by  the  chorion  and  the  villi  on  the  one  side  and  by  the  septa  and  basal  plate 


THE    UMBILICAL    CORD. 


53 


on  the  other.  Maternal  capillaries  are  wanting  within  the  placenta,  since  they  have 
become  early  replaced  by  the  intervillous  lacunae.  The  maternal  blood  is  carried 
away  from  these  spaces  by  wide  venous  channels  which  pass  directly  from  the  lacunae 
through  the  placental  septa  into  the  basal  plate,  where  they  form  net-works  from  which 
proceed  the  larger  venous  trunks.  At  the  edge  of  the  placenta  the  anastomosing  cav- 
ernous spaces  form  an  annular  series  of  intercommunicating  venous  channels  known 
collectively  as  the  marginal  sinus,  into  which  empty  numerous  placental  veins,  on  the 
one  hand,  and  from  which,  on  the  other,  pass  tributaries  to  the  larger  veins  of  the 
uterus. 

Fig.  62. 


Umbilical  avtcr: 


preparation  of  human  placenta,  showing  general  grouping  of  fcetal  vessels  into  lobules. 


The  Umbilical  Cord. — The  umbilical  cord,  or  funiculus  umbilicalis,  which 
connects  the  body  of  the  foetus  with  the  placenta,  thereby  conveying  the  fcetal  blood 
to  and  from  the  respiratory  and  nutritive  apparatus,  is  formed  in  consequence 
of  the  fusion  of  three  originally  distinct  structures, — the  belly-stalk,  the  vitelline 
stalk,  and  the  amnion.  The  first  of  these,  in  addition  to  forming  the  early  attach- 
ment of  the  fcetus  to  the  chorion,  supports  the  rudimentary  allantoic  canal  and  the 
allantoic,  later  umbilical,  blood-vessels.  The  vitelline  stalk  encloses  the  diminish- 
ing vitelline  duct  and  the  remains  of  the  vitelline  blood-vessels,  while  surrounding 
these  stalks  the  amniotic  sheath  gradually  becomes  more  closely  applied.      These 


54  HUMAN   ANATOMY. 

three  constituents  of  the  cord  lie  embedded  within  the  delicate  stroma  formed  by 
the  gelatinous  connective  tissue,  the.  jelly  of  Wharton,  surrounded  externally  by  the 
common  amniotic  investment. 

The  details  of  the  cord  must  necessarily  vary  with  the  period  of  gestation, 
since  the  component  structures  undergo  marked  changes.  On  section  of  the  funic- 
ulus at  the  end  of  pregnancy,  the  following  features  may  usually  be  distinguished  : 

(i)  The  amniotic  sheath,  which  is  closely  united  with  the  underlying  connective 
tissue,  except  for  a  short  distance  beyond  the  umbilical  opening,  at  which  point  the 
amnion  may  be  separated  as  a  distinct  layer. 

(2)  The  jelly  of  Wharton  forms  the  common  ground-substance  in  which  the 
remaining  constituents  of  the  cord  lie  embedded.  This  tissue  corresponds  to  the 
mucoid  type,  and  contains  a  generous  distribution  of  stellate  connective-tissue  cells 
which  form  a  reticulum  by  their  anastomosing  processes. 

(3)  The  umbilical  blood-vessels — two  arteries  and  one  vein — are  the  most  con- 
spicuous components  of  the  cord,  since  their  size  increases  with  the  demands  made  by 
the  growing  fcetus.  The  markedly  tortuous  umbilical  arteries  usually  entwine  the  single 
umbilical  vein  and  slightly  increase  in  lumen  in  their  progress  towards  the  placenta, 
in  the  immediate  vicinity  of  which  an  anastomosis  very  constantly  is  to  be  found. 
Seldom  in  man,  but  always  in  certain  mammals,  as  the  mouse,  the  umbilical  artery  is 
single.      According  to  His,  even  the  youngest  human  cords  possess  only  a  single 

umbilical  vein,  except  in  the  immediate  vi- 
P       ,  cinity  of  the  placenta  ;  again,  on  entering 

umbilical  vein  the  body  of  the  foetus  tl?e  single  vessel  is 

„  .        represented  by  two  umbilical  veins  which, 

Remains  of  r  .  J  .  ,  .  ,  ... 

allantoic  for  a   time,    course  within   the   abdominal 

wall.      The  right  vein,  however,  soon  un- 
dergoes atrophy,  while  the  left  takes  part 
,«~-i  in  the  formation  of  the  hepatic  circulation. 

--„,,.        i-/  '.A       i  Valves  have  been  described  within  the  um- 

\y  bilical  vein.       The   latter  shares   with   the 

/^Umbilical     pulmonary  vein  the  distinction  of  conveying 
artery        Di00d  which  has  been  oxygenated  by  respi- 

^ A—-""       '    Remains  of  vitelline  rat0ry  function. 

\  _ ._  duct  and  vessels  (4)   The  allantoic  duct,   as  a  distinct 

canal,   is  usually  obliterated   by  the   third 

Transverse  section  of  umbilical  cord  of  third  month.  .1  r     r      .    1     ,-r  *.    l_"   *-l-       u 

x  I2.  month   of    fcetal    life  ;    at    birth,    however, 

atrophic  remains,  consisting  of  a  narrow 
column  of  epithelial  cells  situated  between  the  umbilical  blood-vessels,  are  seen  in 
sections  of  the  cord  taken  from  the  vicinity  of  the  navel. 

The  stalk  of  the  vitelline  sac,  or  umbilical  vesicle,  enclosing  the  vitelline  duct 
and  supporting  the  vitelline,  or  omphalomesenteric,  blood-vessels,  is  still  present 
during  the  second  month  ;  at  this  period  it  lies  within  the  extension  of  the  ccelom, 
which  is  continued  into  the  young  cord.  With  the  early  disappearance  of  this  space 
the  vitelline  stalk  and  the  associated  structures  disappear,  and  by  the  end  of  gesta- 
tion usually  all  traces  of  these  structures  have  vanished  from  the  cord.  The  most 
conspicuous  details  of  the  umbilical  cord  at  birth,  therefore,  are  the  three  umbilical 
vessels,  embedded  within  the  gelatinous  connective  tissue  and  invested  by  the  sheath 
of  amnion. 

The  human  umbilical  cord  is  conspicuous  on  account  of  its  exceptional  length, 
which  averages  from  fifty  to  sixty  centimetres,  while  measuring  only  about  twelve 
millimetres  in  thickness.  The  extremes  of  length  include  a  wide  range,  varying  from 
twelve  to  160  centimetres  (four  and  three-quarters  to  sixty-three  inches). 

The  cord  almost  constantly  exhibits  a  torsion,  the  spirals  passing  from  left  to 
right  when  traced  towards  the  placenta.  In  addition  to  the  general  twisting  of  the 
cord,  which  -begins  towards  the  close  of  the  second  month,  the  umbilical  arteries 
display  even  more  marked  spiral  windings,  usually  enclosing  the  somewhat  less 
twisted  umbilical  vein.  The  cause  of  this  conspicuous  torsion  is  probably  to  be 
sought  in  the  spiral  growth  of  the  umbilical  blood-vessels,  the  twisting  of  the  cord, 
as  well  as  the  revolutions  of  the  fcetus,  being  secondary. 


THE    AFTER-BIRTH. 


55 


€ 


V 


section  ot  umbilical  cord  at  end  of  pregnancy, 
placental  end;  the  umbilical  blood-vessels  are  em- 
in  the  embryonal  connective  tissue.     X  to. 


While  the  attachment  of  the  cord  usually  is  situated  near  the  middle  of  the 
placenta,  it  is  seldom  exactly  central  ;  the  insertion  is  subject  to  great  variation, 
however,  the  eccentricity  sometimes  being  so  great  that  the  cord  is  fixed  to  the 
periphery  of  the  placenta,  such  disposition  constituting  insertio  margiyialis .  Among 
the  more  exceptional  variations  in  the  arrangement  of  the  cord  are  the  cleft  and  the 
extraplacental  attachment  known  respectively  as  insertio  furcata  and  insertio  vela- 
mentosa.  In  the  former  condition,  where  the  cord  divides  before  reaching  the  pla- 
centa, each  limb  conveys  one  of  the  umbilical  arteries  and  a  branch  of  the  umbilical 
vein.      When  the  insertion  of  the 

cord  is   into   the  chorion  entirely  pIG  6d 

outside  the  placental  area,  in  ex- 
ceptional cases  being  as  far  re- 
moved as  the  opposite  pole  of  the 
membranous  capsule,  the  umbilical 
vessels  course  within  the  non-vil- 
lous  portions  of  the  chorion  until 
they  reach  the  fcetal  placenta.  In 
addition  to  the  true  knots,  which 
often  occur  and  are  due  to  the 
excursions  of  the  fcetus,  the  um- 
bilical cord  sometimes  presents 
nodular  thickenings  and  irregular 
constrictions,  as  well  as  projections 
formed  by  loops  and  varicosities  of 
the  blood-vessels. 

The  After-Birth.— The  ex- 
pulsion of  the  child  through  the 
rupture  in  the  enveloping  mem- 
branes, which  is  produced  by  the 
powerful  contractions  of  the  uterine 

muscle  at  the  close  of  pregnancy,  is  followed,  after  a  short  interval,  by  the  separa- 
tion and  expulsion  of  the  ' '  after-birth  ;' '  under  this  term  are  included  the  placenta 
and  the  enveloping  membranes.  The  latter,  as  will  be  understood  from  the  fore- 
going consideration  of  the  encapsulation  of  the  fcetus,  consist  of  three  chief  constit- 
uents,— the  remains  of  the  decidua  vera,  the  chorion,  and  the  amnion  ;  the  reflexa 
undergoes  complete  absorption.  Since  the  decidua  represents  the  shed  portion  of 
the  modified  uterine  mucosa,  the  outer  surface  of  the  after-birth  appears  rough  and 
studded  with  shreds  of  uterine  tissue  ;  the  inner  surface  of  the  decidua  is  so  closely 

fused  with  the  adjacent  cho- 

Fig.  65.  rion  by  means   of    delicate 

Amnion      ^-^^^ny^a^^^^^^^y,       connective  tissue  that  only 

rhon""      "  ;'    -'    .":-""',;  '"^-J-i      '-■    ?'-"—"''-*        a     limited     and     uncertain 

Decidua  _  ..       '  ^s^s^a-i       separation  is  possible.     The 

__;.    "-;.-.-_.. .    --.,.  ._.._„_-:-      'amnion,  on  the  other  hand, 
C^TT^T- v? ■■'"•■   "'J^^-F^       although    attached    to   the 
"""-.—-'  .  ^^^-^^"^^ ■■■■      chorion  by  bands  of  connec- 
tive tissue,  may  be  peeled 
vJle%doid?US  St  e"d  °£  pre£na,'c>-  off  the  chorion  with  relative 

ease,  since  the  union  be- 
tween the  two  membranes  is  never  firm.  The  inner  ectoblastic  surface  of  the 
amnion  in  contact  with  the  fcetus  is  smooth  and  bathed  in  the  liquor  amnii.  The 
external  and  unshed  portion  of  the  modified  uterine  mucosa  contains  the  incon- 
spicuous remains  of  the  epithelium  lining  the  fundus  of  the  glands  :  these  elements 
are  of  the  utmost  importance  for  the  regeneration  of  the  glandular  and  epithelial 
tissues  of  the  new  uterine  mucous  membrane,  since  the  reparation  of  these  struc- 
tures, which  is  effected  within  a  few  weeks  after  labor,  begins  in  the  proliferation  of 
the  deeper  glandular  epithelium,  which  remains  throughout  pregnancy  as  the  latent 
source  of  subsequent  repair. 


uterine  gla 
Uterine  mi 


Section  through  fcetal  1 


5& 


HUMAN    ANATOMY. 


DEVELOPMENT    OF   THE    GENERAL    BODY-FORM. 

In  considering  the  evolution  of  the  external  form  of  the  human  product  of  con- 
ception, it  is  convenient  to  recognize  the  three  developmental  epochs  suggested  by 
His, — the  stage  of  the  ovum,  the  stage  of  the  embryo,  and  the  stage  of  the  fcetus. 

The  Stage  of  the  Blastodermic  Vesicle. — This  stage,  or  the  stage  of  the 
ovum,  embraces  the  first  two  weeks  of  intra-uterine  life,  during  which  the  initial  phases 
of  development,  including  fertilization,  segmentation,  and  the  formation  of  the  blasto- 

Fig.  66. 


<ac: 


<V.Af-k_ 


t<il 


":\  a,.;  l 

q  ': 

>~\ 

'■'■:---..Xv>. 

':'     ' 

>> 

i 

k 

v" 

^^ 

J)' 

Villous  chorion 


Ectoblast 
Mesoblast 


Umbilical  vesi- 
cle; blood- 
islands  appear- 


Early  human  embryonic  vesicle  of  about  thirteen  days  laid  open,  showing  the  young  embryo  (.37  millimetre 
long)  attached  to  the  wall  of  the  serosa  by  means  of  the  belly-stalk.     X  25.     {After  Spee.) 


dermic  vesicle,  are  completed,  and  the  fundamental  processes  resulting  in  the  differ- 
entiation of  the  medullary  tube,  the  notochord,  the  somites,  and  the  mesoblastic  plates 
are  begun.  The  early  details  of  many  of  these  processes  have  never  been  observed 
in  man,  but  there  is  little  reason  to  doubt  that  in  its  essential  features  the  early  human 
embryo  closely  follows  the  changes  directly  observed  in  other  mammals. 

The  Stage  of  the  Embryo.— The  stage  of  the  embryo,  from  the  second  to 

the    fifth   week,    is    distin- 
F|G-  67.  guished  by  the  formation  of 

organs  essentially  embry- 
onic and  transient  in  char- 
acter, as  the  somites,  the 
notochord,  the  Wolffian 
body,  and  the  visceral 
arches. 

The  earliest  phase  in 
the  differentiation  of  the 
vertebrate  body-form  con- 
>  sists  in  the  establishment  of 
a  dorsal  tube  by  the  appo- 
sition and  fusion  of  the  ectoblastic  medullary  folds,  and  a  ventral  tube  by  the  approxi- 
mation and  final  union  of  the  folds  directly  derived  from  the  somatopleura.  The 
dorsal,  or  animal,  tube  represents  the  early  neural  canal,  and  becomes  the  great 
cerebro-spinal  nervous  axis  ;  the  ventral,  or  vegetative,  tube,  formed  by  the  ventral 
extension  and  approximation  of  the  somatopleura,  constitutes  the  body-cavity,  and 
encloses  the  primary  gut  and  the  associated  thoracic  and  abdominal  viscera,  and  the 
vascular  system.      The  primitive  gut-tube  originates  by  the  delimitation  of  a  part  of 


Section  of  preceding  embryc 


Umbilical  sac 
nd  embrvo.     X  25. 


THE    EARLY    HUMAN    EMBRYO. 


57 


the  vitelline  sac  accomplished  by  the  ventral  approximation  of  the  splanchnopleura, 

and  for  a  time  maintains  a  wide  communication  with  the  remains  of  the  yolk-cavity. 

The  early  embryo,  lying  flatly  expanded  upon  the  blastodermic  vesicle,  becomes 

differentiated  in  form  by  the  appearance  of  head-  and  tail-grooves,  in  consequence  of 


6  * 
t?  Q 


which  constriction  the  cephalic  and  the  caudal  poles  of  the  body  become  defined  and 
partially  separated  from  the  embryonal  area  ;  the  middle  segment,  however,  em- 
bracing the  widely  open  gut-tract,  for  a  time  remains  closely  blended  with  the  vitel- 
line sac,  of  which,  at  first,  the  embryo  appears  as  an  appendage  (Fig.  6S,  i  and  2). 


58 


HUMAN    ANATOMY. 


The  more  complete  differentiation  of  the  digestive  tube  and  the  ventral  folding  in  of 
the  body-walls  change  this  relation,  the  rapidly  decreasing  umbilical  vesicle  soon 
becoming  secondary  to  the  embryo. 

At  the  close  of  the  stage  of  the  vesicle — about  the  fifteenth  day — the  human 
embryo  possesses  a  general  cylindrical  body-form,  the  dilated  cephalic  pole  being 
free,  while  the  belly-stalk  attaches  the  caudal  segment  to  the  chorion  ;  the  amniotic 
sac  invests  the  dorsal  aspect,  the  large  umbilical  vesicle  occupying  the  greater  part 

of  the  ventral  surface.      Human 
Fig.  69. 

Otic  vesicle  Second  visceral  arch 

Cephalic  flexure — ^. - 

_  ~Third  visceral 
Optic  vesicle 

„     .„  X^i-f-^l i — Fourth  visceral 

Maxillary  process fc       ^     \-.  *        arcn 


r  proces: 


Mandibul; 

of  first  visceral  arch 
Caudal  end  ot 
embryo 


Lower  linih-!nul 


Upper  limb-bud 


:  days,  drawn  from  the  model 


embryos  of  the  fourteenth  and 
fifteenth  days  (Fig.  68,  3  and  4) 
are  distinguished  by  a  conspicu- 
ous flexure  opposite  the  attach- 
ment of  the  umbilical  vesicle,  the 
convexity  being  directed  ven- 
trally,  the  deep  corresponding 
concavity  producing  a  marked 
change  of  profile  in  the  dorsal 
outline.  During  these  changes 
the  expansion  of  the  cerebral 
segments  outlines  the  three  pri- 
mary divisions  of  the  cephalic 
portion  of  the  neural  tube,  the 
anterior,  the  middle,  and  the 
posterior  brain-vesicles. 
A  little  later  a  series  of  conspicuous  bars,  the  visceral  arches,  appears  as  ob- 
liquely directed  parallel  ridges  on  either  side  of  the  head,  immediately  above  the 
prominent  heart-tube,  which  is  now  undergoing  marked  torsion.  By  the  nineteenth 
day  the  dorsal  concavity,  which  is  peculiar  to  the  human  embryo,  has  entirely  disap- 
peared, the  profile  of  this  part  of  the  embryo  presenting  a  gentle  convexity  ;  the 
cephalic  axis,  however,  exhibits  a  marked  bend,  the  cephalic  flexure,  in  the  vicinity 
of  the  middle  cerebral  vesi- 
cle, in  consequence  of  which 
the  axis  of  the  anterior  cere- 
bral segment  lies  almost  at 
right  angles  to  that  of  the 
middle  vesicle.  The  com- 
pletion of  the  third  week 
finds  the  characteristic  de- 
tails of  the  cephalic  end  of 
the  embryo,  the  cerebral, 
the  optic,  and  the  otic  vesi- 
cles, and  the  visceral  arches 
and  intervening  furrows  well 
advanced,  with  correspond- 
ing definition  of  the  primitive 
heart  and  the  umbilical  stalk 
and  vesicle.  The  limb-buds 
usually  appear  about  this 
time,  those  of  the  upper  ex- 
tremity slightly  preceding 
those  of  the  lower.  x  I0- 

The  period  between  the 
twenty-first  and  the  twenty-third  days  witnesses  remarkable  changes  in  the  general 
appearance  of  the  embryo  ;  in  addition  to  greater  prominence  of  the  visceral  arches, 
the  cerebral  segments,  and  the  limb-buds,  the  embryonic  axis,  which,  with  the 
exceptions  already  noted,  up  to  this  time  is  only  slightly  curved,  now  undergoes 
flexion  to  such  extent  that  by  the  twenty-third  day  the  overlapping  cephalic  and 
caudal  ends  of  the  embryo  are  in  close  apposition,  the  body-axis  describing  rather 
more  than  a  complete  circle  (Fig.  69). 


Cephalic  fle 


Optic  vesicle 


Umbilical  cord 


Lower  limb-b 


1  flexure 
Second  visceral  arch 

Third  visceral  arch 
Fourth  visceral  arch 


L'pper  limb-bud 


>  of  about  twenty-fiv 


THE    VISCERAL    ARCHES    AND    FURROWS. 


59 


From  the  twenty-third  to  the  twenty-eighth  day  the  excessive  flexion  gradually 
disappears,  owing  to  the  increased  volume  of  the  heart  and  the  growth  of  the  head, 
and  by  the  end  of  the  fourth  week  the  embryo  has  acquired  the  most  characteristic 
development  of  the  embryonic  stage  (Fig.  71).  The  reduction  in  the  curvature 
of  the  body-axis  and  the  consequent  separation  of  its  poles  and  the  raising  of  the  head 
are  accompanied  by  the  appearance  of  four  well-marked  axial  flexions,  the  cephalic, 
the  cervical,  the  dorsal,  and  the  sacral  flexures  (Fig.  71 ).  The  first  of  these,  the 
cephalic,  is  an  accentuation  of  the  primary  flexure,  which  is  seen  as  early  as  the 
eighteenth  clay,  and  is  indicated  by  the  projection  of  the  midbrain  ;  it  corresponds 
in  position  to  the  future  sella  turcica.  The  second  and  very  conspicuous  bend,  the 
cervical  flexure,  marks  the  caudal  limit  of  the  cephalic  portion  of  the  neural  axis, 
and  agrees  in  position  with  the  subsequent  upper  cervical  region.  The  dorsal  and 
sacral  flexures  are  less  well  defined,  the  former  being  situated  opposite  the  upper 
limb-bud,  where  the  cervical  and  dorsal  series  of  somites  join,  the  latter,  near  the 
lower  limb-bud,  corresponding  with  the  junction  of  the  lumbar  and  sacral  somites. 

The  cephalic  segment  at  this  stage  presents  numerous  prominent  details,  the 


Fig.  71. 


Cervical  flexure 


Maxillary  process  of  first— ^^ 
visceral  arch 

f 
Cephalic  flexure-1 

\ 


visceral  arch 

First  external  visceral  furrow 


Second  visceral  arch 


Sacral  flex 
Human  embryo  of  about  twenty-eight  days,  drawn  fn 


the  model  of  Hi: 


secondary  cerebral  vesicles,  the  forebrain,  the  interbrain,  the  midbrain,  the  hind- 
brain,  and  the  after-brain,  the  visceral  arches  and  furrows,  the  optic  and  otic  vesicles, 
the  olfactory  pits,  and  the  primitive  oral  cavity  all  being  conspicuous.  The  heart  ap- 
pears as  a  large  protrusion,  occupying  the  upper  half  of  the  ventral  body-wall,  on 
which  the  primary  auricular  and  ventricular  divisions  are  distinguishable.  The  somites 
form  a  conspicuous  longitudinal  series  of  paraxial  quadrate  areas,  about  thirty-seven 
in  number  ;  they  correspond  to  the  intervertebral  muscles,  and  may  be  grouped  to 
accord  with  the  primary  spinal  nerves,  being,  therefore,  distinguished  as  eight  cer- 
vical, twelve  dorsal,  five  lumbar,  five  sacral,  and  five  or  more  coccygeal  somites. 

THE   VISCERAL   ARCHES   AND    FURROWS. 

Since  the  visceral  arches  are  best  developed  in  the  human  embryo  during  the 
last  half  of  the  third  week,  a  brief  consideration  of  these  structures  in  this  place  is 
appropriate.  The  visceral  arches  in  mammalian  embryos  constitute  a  series  of  five 
parallel  bars  separated  by  intervening  furrows,  obliquely  placed  on  the  ventro-lateral 
aspect  of  the  cephalic  segment,  occupying  the  region  which  later  becomes  the 
neck.     They  represent,  in  rudimentary  development,  the  important  branchial  or  gill- 


60  HUMAN    ANATOMY. 

apparatus  of  water-breathing  vertebrates,  in  which  the  respiratory  function  is  per- 
formed by  means  of  the  rich  vascular  fringes  lining  the  clefts  through  which 
the  water  passes,  thus  permitting  the  exchange  between  the  oxygen  of  the  water 
and  the  carbon  dioxide  of  the  blood.  Each  arch  is  supplied  by  a  blood-vessel,  or 
aortic  bow,  which  passes  from  the  main  ventral  stem,  the  truncus  arteriosus,  through 
the  substance  of  the  visceral  arch  backward  to  unite  with  the  similar  bows  to  form 
the  dorsal  aortcB.  In  aquatic  vertebrates  the  aortic  bows  supply  an  elaborate  system 
of  secondary  branchial  twigs,  which  form  rich  capillary  plexuses  within  the  gills  ;  in 
air-breathing  vertebrates,  however,  in  which  these  structures  are  only  rudimen- 
tary, the  main  stems,  the  aortic  bows,  are  alone  represented.  With  the  loss  of  func- 
tion which  follows  the  acquisition  of  aerial  respiration  in  the  higher  vertebrates,  the 
number  of  visceral  arches  is  reduced  from  six,  or  even  seven,  as  seen  in  fishes,  to 
five,  the  fifth  arch  in  man,  however,  being  so  blended  with  the  surrounding  struc- 
tures that  it  is  not  visible  externally  as  a  distinct  bar.  In  their  condition  of  great- 
est perfection,  as  in  fishes,  each  visceral  arch  contributes  an  osseous  bar,  which 
forms  part  of  the  branchial  skeleton  ;  these  bony  bars  are  represented  in  man  and 
mammals  by  cartilaginous  rods,  which  temporarily  occupy  the  upper  arches,  for  the 
most  part  entirely  disappearing.  When  viewed  in  frontal  section  (Fig.  73),  the 
mammalian  visceral  arches  are  seen  as  mesodermic  cylinders  imperfectly  separated 
by  external  and  internal  grooves,  the  visceral  furrows  and  the  pharyngeal  pouches 
respectively  ;  this  arrangement  emphasizes  another  modification  following  loss  of 
function, — namely,  the  conversion  of  the  true  visceral  clefts  of  the  lower  forms  into 

furrows, — since  in  man  and  mammals  the 
Pjg.  72.  fissures  are  closed  by  the  occluding  mem- 

brane formed  by  the  apposition  of  the 
ectoblast  and  the  entoblast  at  the  bottom 
of  the  outer  and  inner  furrows. 

The  First  or  Mandibular  Arch 

Maxillary    \  J ■  ■       .  ,._.,. 

process — ;,■ '.at -      g  ,  early  becomes  differentiated  into  a  short 

p  -    •,  •  !.^^        /    ,       -:  __ Second  arch  J 

oraUavily T      ^.7—      ---Third  arch       uPPer  or  maxillary  process  and  a  longer 

Mandibular 


>.__     '  J  \  lower  or  mandibular  process.     The  maxil- 

process  t<r -—Fourth  arch        ,  :       i        _^-__  ___*^i_  :,__  r_n 


lary  process,  in  conjunction  with  its  fellow 


-Fifth  arch 


of  the  opposite  side  and  the  fronto-nasal 

Head  ot  human  embryo  of  about  twenty-one  days,        A-rnrps?    wriirri  Hf^rpnrlc:  nc  o  mprlian  nrrt- 
seen  from  the  side,  showing  visceral  arches  and  external       process    wniCtl  descends  as  a  median  pro 

visceral  furrows,    x  20.    (After  His.)  jection  from  the  head  (Fig.  75),  contrib- 

utes the  tissue  from  which  the  superior 
and  lateral  boundaries  of  the  oral  cavity  and  the  nasal  region  are  derived.  The 
mandibular  process  joins  with  its  mate  in  the  mid-line  and  gives  rise  to  the  lower 
jaw  and  other  tissues  forming  the  inferior  boundary  of  the  primary  oral  cavity.  The 
latter  in  its  original  condition  appears  as  a  widely  open  space  leading  into  the  primi- 
tive pharyngeal  cavity  ;  later  the  septum  is  formed  which  divides  the  oral  from  the 
nasal  cavity.  The  mandibular  process  contains  a  cartilaginous  rod,  which  for  a 
time  represents  the  corresponding  bony  arch  of  the  visceral  skeleton  of  lower  types. 
The  ventral  and  larger  part  of  this  rod,  known  as  Meckel' s  cartilage,  entirely  disap- 
pears, the  lower  jaw  being  developed  independently  around  this  bar  of  cartilage  ; 
the  upper  end  of  the  cartilaginous  bar,  however,  persists  and  forms  two  of  the  ear- 
ossicles,  the  malleus  and  the  incus. 

The  Second  or  Hyoid  Arch  also  contains  a  cartilaginous  bar,  from  the  ven- 
tral segment  of  which  (known  as  the  cartilage  of  Reicherf)  is  derived  the  smaller 
cornu  of  the  hyoid  bone  ;  the  dorsal  end  of  the  bar,  which  is  fused  with  the  tem- 
poral bone,  gives  rise  to  the  styloid  process,  the  intervening  portion  of  the  cartilage 
persisting  as  the  stylo-hyoid  ligament.  The  cartilage  of  the  second  arch  is  also  con- 
cerned in  the  formation  of  the  stapes.  The  origin  of  this  ear-ossicle  is  double,  since 
the  crura  of  the  stapes  are  derived  from  the  cartilage  of  the  hyoid  arch,  while  the 
base  is  contributed  by  the  general  cartilaginous  capsule  of  the  labyrinth.  The  char- 
acteristic form  of  the  stapes  is  secondary  and  due  to  the  perforation  of  the  triangu- 
lar plate,  the  early  representative  of  this  bone,  which  thus  acquires  its  characteristic 
stirrup-shape  in  consequence  of  the  penetration  of  a  minute  blood-vessel,  the' perfo- 
rating stapedial  artery,  a  branch  of  the  internal  carotid,  which  later  disappears. 


THE    VISCERAL    ARCHES. 


61 


The  Third  or  First  Branchial  Arch  contains  a  rudimentary  cartilaginous 
bar  from  which  part  of  the  body  and  the  greater  cornu  of  the  hyoid  bone  are  derived. 
The  fourth  and  fifth  arches,  or  second  and  third  branchial,  enclose  rudimentary 
cartilaginous  bars  which  early  fuse  into  plates  ;  these  unite  along  their  ventral  borders 
and  give  rise  to  the  thyroid  cartilage  of  the  larynx. 

The  External  Visceral  Furrows  (Fig.  73),  the  representatives  of  the  true 
clefts  of  the  lower  types,  appear  with  decreasing  distinctness  from  the  first  towards  the 
fourth  ;  the  third  and  fourth  early  suffer  modification,  so  that  by  the  twenty-eighth 
day  the  first  and  second  furrows  alone  are  clearly  defined. 

The  First  Visceral  Furrow,  the  hyomandibular  cleft,  undergoes  obliteration 
except  at  its  dorsal  part,  which  becomes  converted  into  the  external  auditory  meatus, 
the  surrounding  tissue  giving  rise  to  the  walls  of  the  canal  and  the  external  ear.  The 
remaining  clefts  gradually  disappear,  becoming  closed  and  covered  in  by  the  over- 
hanging  corresponding  arches  ;    this   relation   is  particularly  marked  towards   the 


Fig.  73. 


Maxillary  process 


Dorsal  wall  of  primitive 
oropharynx 


Primitive  oesophagus 
Upper  end  of  body-cavity 

Right  umbilical  i 


Upper  half  of  human  embryo  of  about  eighteen  days,  drawn  from  His's  models.  X  45.  A.  dorsal  wall  of  primitive 
oropharynx  bounded  by  visceral  arches,  external  and  internal  furrows.  B,  anterior  wall  of  primitive  oropharynx, 
seen  from  behind.     1-5,  sections  of  aortic  arches;   I-IV,  external  visceral  furrows. 

caudal  end  of  the  series,  where  the  sinking  in  of  the  arches  and  the  included  furrows 
produces  a  depression  or  fossa — the  sinus  prcecerzncalis  of  His — in  the  lower  and  lateral 
part  of  the  future  neck  region.  This  recess  subsequently  entirely  disappears  on 
coalescence  of  the  bordering  parts  ;  sometimes,  however,  such  union  is  defective, 
the  imperfect  closure  resulting  in  a  permanent  fissure  situated  at  the  side  of  the  neck, 
known  as  cervical  fistula,  by  means  of  which  communication  is  often  established 
between  the  pharynx  and  the  exterior  of  the  body.  Such  communication  must, 
however,  be  regarded  as  secondary,  as  originally  the  external  furrows  were  sepa- 
rated from  the  primitive  pharyngeal  cavity  by  the  delicate  epithelial  septum  already 
mentioned  as  the  occluding  plate.  Where  entrance  into  the  pharynx  through  the 
fistula  is  possible,  it  is  probable  that  the  septum  has  been  destroyed  as  the  result 
of  absorption  or  of  mechanical  disturbance  following  the  use  of  the  probe. 

The  Inner  Visceral  Furrows,  or  pharyngeal  pouches,  repeat  the  general 
arrangement  of  the  external  furrows.  The  first  pharyngeal  pouch  becomes 
narrowed  and  elongated,  and  eventually  forms  the  Eustachian  tube  ;  a  secondary 


62 


HUMAN    ANATOMY. 


Olfactory— ^j?" 
Dit  at^. 


Head  of  human  emD 
showing  boundaries  of 
(After  His.) 


dorsal  expansion  gives  rise  to  the  middle  ear,  while  the  occluding  plate  separating 
the  outer  and  inner  furrows  supplies  the  tissue  from  which  the  tympanic  membrane  is 
formed.  The  second  furrow  in  great  part  disappears,  but  its  lower  portion  con- 
tributes the  epithelium  of  the  faucial  tonsil  and  the  supratonsillar  fossa.  The  fossa  of 
Rosenmiiller  is  a  secondary  depression  and  probably  does  not  represent  the  original 
furrow.  The  third  and  fourth  pouches  give  rise  to  ventral  entoblastic  outgrowths 
from  which  the  epithelial  portions  of  the  thymus  and  of  the  thyroid  body  are  developed 
respectively.  The  last-named  organ  has  an  additional  unpaired  origin  from  the  ento- 
blast  forming  the  ventral  wall  of  the  pharynx  in  the  vicinity  of  the  second  visceral  arch. 

The  Development  of  the   Face 
Fig174.  and   the    Oral    Cavity. — The   earliest 

suggestion  of  the  primitive  oral  cavity  is 
the  depression,  or  stomodceum,  which  ap- 
-  Lateral  nasal  process    pears   about  the    thirteenth   day   on    the 
,,    .  ,        ,  ventral  surface  of  the  cephalic  end  of  the 

Mesial  nasal  process  .  r 

Maxillary  process  embryo  immediately  beneath  the  ex- 
Mandibuiar  process  panded  anterior  cerebral  vesicle.  The 
oral  pit  at  first  is  separated  from  the  ad- 
jacent expanded  upper  end  of  the  head- 
gut  by  the  delicate  septum,  the  pharyn- 
,  geal  membrane,  composed  of  the  opposed 
ectoblast  and  the  entoblast,  which  in  this 
location  are  in  contact  without  the  inter- 
vention of  mesoblastic  tissue.  With  the  rupture  of  the  pharyngeal  membrane,  the 
deepened  oral  pit  opens  into  the  cephalic  extremity  of  the  head-gut,  now  known  as 
the  primitive  pharynx. 

The  formation  of  the  face  is  closely  associated  with  the  growth  and  fusion  of 
the  upper  visceral  arches  in  conjunction  with  the  surrounding  parts  of  the  ventral 
surface  of  the  head.  The  first  visceral  arch,  as  already  described,  presents  two 
divisions,  the  maxillary  and  the  mandibular  process.  The  latter  grows  ventrally  and 
joins  in  the  mid-line  its  fellow  of  the  opposite  side,  to  form,  with  the  aid  of  the 
second  visceral  arches,  the  tissues  from  which  the  lower  boundary  and  the  floor  of 
the  mouth  are  derived.      The  upper  and 

lateral  boundaries  of  the  primitive  oral  Fig.  75. 

cavity  and  the  differentiation  of  the  nasal 
region  proceed  from  the  modification  and 
fusion  of  three  masses,  the  two  lateral 
paired  maxillary  processes  of  the  first 
visceral  arches  and  the  mesial  unpaired 
fronto-nasal process,  which  descends  as  a 
conspicuous  projection  from  the  ventral 
surface  of  the  anterior  part  of  the  head. 
The  maxillary  processes  grow  towards 
the  mid-line  and,  in  conjunction  with  the 
descending  fronto-nasal  projection,  form 
the  lateral  and  superior  boundary  of  the 
primitive  oral  cavity  (Fig.  74).  Very 
soon  the  development  of  the  future 
nares  is  suggested  by  the  appearance  of 
slight  depressions,  the  olfactoiy  pits,  one  on  each  side  of  the  fronto-nasal  process  ; 
these  areas  constitute  part  of  the  wall  of  the  forebrain,  a  relation  which  foreshadows 
the  future  close  association  between  the  olfactory  mucous  membrane  and  the  cortex 
of  the  olfactory  lobe. 

During  the  fifth  week  the  thickened  margins  of  the  fronto-nasal  process  undergo 
differentiation  into  the  mesial  nasal  processes,  while  coincidently  the  lateral  portions 
of  the  fronto-nasal  projection  grow  downward  as  the  lateral  nasal  processes,  these 
newly  developed  projections  constituting  the  inner  and  outer  boundaries  of  the 
rapidly  deepening  nasal  pits.  The  line  of  contact  between  the  lateral  nasal  process 
and  the  maxillary  process  is  marked  by  a  superficial  furrow,  the  naso-optic  groove, 


Lateral  nasal  process 
Maxillary  process 
First  external  vis- 
ceral furrow 
Second  visceral  arch 
Third  visceral  arch 


Head  of  human  < 


THE    STAGE    OF    THE    FCETUS. 


63 


Anlage  producing 
nasal  tip 


Nasal  groove--- 


Naso-optic  g 


Dorsum  of  nose 


1  pro- 


Portion  of  head  of  h'j 
roof  of  prim 


Roof  of  oropharynx 


of  about  thirty-four 
ity.     X  10.     (After 


s,  showing 


which  leads  from  the  nasal  pit  to  the  angle  of  the  eye  ;  this  furrow,  however,  merely 
indicates  the  position  of  the  naso-lachrymal  duct  which  develops  independently  at  the 
bottom  of  the  primary  groove.  Reference  to  Figs.  74  and  75  emphasizes  the  fact 
that  the  nasal  pits  and  the  primitive  oral  cavity  are  for  a  time  in  widely  open  com- 
munication ;  towards  the  close  of  the  sixth  week,  however,  the  maxillary  processes 
of  the  first  arch  have  approached  the  mid-line  to  such  an  extent  that  they  unite  with 
the  lateral  margins  of  the  fronto-nasal  process  as  well  as  fuse  with  the  lateral  nasal 
processes  above.  Owing  to  this  union  of  the  three  processes,  the  nasal  pits  become 
separated  from  the  oral  cavity, 

and  with  the  appearance  and  Fig.  76. 

completion  of  the  palatal  sep- 
tum the  isolation  of  the  nasal 
fossae  from  the  mouth  is  ac- 
complished. The  lateral  nasal 
processes  contribute  the  nasal 
alas,  while  from  the  conjoined 
mesial  nasal  process  are  devel- 
oped the  nasal  septum  and  the 
bridge  of  the  nose  in  addition 
to  the  middle  portion  of  the 
upper  lip  and  the  intermaxil- 
lary segment  of  the  upper  jaw, 
the  superior  maxillary  part  of 
the  latter  being  a  derivative  of 
the  maxillary  process  of  the  first  arch.  Arrested  development  and  imperfect  union 
between  the  maxillary  processes  and  the  fronto-nasal  process  result  in  the  congenital 
defects  known  as  harelip  and  cleft  palate,  the  degree  of  the  malformation  depending 
upon  the  extent  of  the  faulty  union. 

The  Stage  of  the  Foetus. — The  fifth  week  marks  the  completion  of  the 
period  of  development  during  which  the  product  of  conception  has  acquired  the 
characteristic  features  of  its  embryonal  stage  ;  beginning  with  the  second  month  and 
continuing  until  the  close  of  gestation,  the  succeeding  stage  of  the  foetus  is  distin- 
guished by  the  gradual  assumption  of  the  external. features 
which  are  peculiar  to  the  young  human  form.  In  addition  to 
the  already  mentioned  changes  affecting  the  visceral  arches 
and  frontal  process  in  the  development  of  the  face,  the  fifth 
week  witnesses  the  differentiation  of  the  limbs  into  segments, 
the  distal  division  of  the  upper  extremity  exhibiting  indica- 
tions of  the  future  fingers,  which  thus  anticipate  the  appear- 
ance of  the  toes.  The  liver  is  already  conspicuous  as  a 
marked  protuberance  occupying  the  ventral  aspect  of  the 
trunk  immediately  below  the  heart.  The  head  by  this  time 
has  acquired  a  relatively  large  size,  the  prominent  cephalic 
flexure  which  marks  the  position  of  the  midbrain  being  par- 
ticularly conspicuous.  At  the  end  of  the  fifth  week,  or  the 
thirty-fifth  day,  the  fcetus  measures  about  fourteen  millimetres 
in  its  longest  dimension. 

The  sixth  week  finds  the  fcetus  elongated  with  greater 
distinctness  of  the  human  form,  the  large  size  of  the  head, 
on  which  the  cervical  flexure  is  very  evident,  being  highly 
characteristic  when  compared  with  corresponding  stages  of  the 
lower  mammals.  The  several  constituents  of  the  face  become  more  perfectly  formed, 
including  the  completion  of  the  superior  boundary  of  the  oral  cavity  and  its  separation 
from  the  nasal  pits  by  the  septum  resulting  from  the  union  of  the  fronto-nasal  process 
with  the  maxillary  processes  ;  the  fusion  of  the  latter  with  the  lateral  frontal  processes 
now  defines  the  external  boundary  of  the  nostrils  of  the  still,  however,  broad  and 
flattened  nose,  which  lies  immediately  above  the  transverse  cleft-like  oral  opening. 
The  visceral  arches  are  no  longer  visible  as  individual  bars,  having  undergone  com- 
plete fusion.     The  differentiation  of  the  digits  on  both  hands  and  feet  has  so  far 


Fig.  77. 


Head  ol  human  e 
of  about  seven  weeks 
(After  Ecker.) 


64  HUMAN    ANATOMY. 

progressed  that  fingers  and  toes  are  distinctly  indicated,  although  the  fingers  only 
are  imperfectly  separated.  The  first  suggestion  of  the  external  genitals  appears 
about  the  end  of  the  sixth  week.  At  this  time  the  foetus  measures  about  nineteen 
millimetres. 

During  the  seventh  and  eighth  weeks  the  foetal  form  of  the  body  and  the 
limbs  attain  greater  perfection,  the  large  head  becoming  raised  from  the  trunk  and  the 
toes,  as  well  as  fingers,  being  now  well  formed,  although  the  rudiments  of  the  nails 
do  not  appear  until  some  time  during  the  third  month.  At  the  close  of  the  second 
month  the  extra-embryonic  protrusion  of  the  intestine  through  the  umbilicus  into 
the  umbilical  cord  reaches  its  greatest  extent.  The  genito-urinary  system  is  repre- 
sented by  the  fully  developed  Wolffian  body,  the  vesical  dilatation  of  the  allantoic 
duct,  the  separation  of  the  cloaca  into  rectum  and  genito-unnary  passage,  the  indif- 

Fig.  7S. 


Umbilical  vesicle 


Umbilical  stalk 


Inner  surface  of- 


Umbilieal  cord. 


Human  embryo  of  about  thirty-five  days.     X  4.     Amnion  and  chorion  cut  and  turned  aside. 

ferent  sexual  gland,  and  the  undifferentiated  external  genitals,  consisting  of  the  geni- 
tal eminence  and  the  associated  genital  folds  and  genital  ridges.  The  external  ear 
has  assumed  its  characteristic  form,  and  the  eyelids  appear  as  low  folds  encircling  the 
conspicuous  eye,  in  which  the  pigmentation  of  the  ciliary  region  is  visible.  Although 
the  face  is  well  formed,  the  nose  is  still  flat,  the  lips  but  slightly  prominent,  and  the 
palate  not  completely  closed.  The  rapid  growth  of  the  brain  results  in  the  dispro- 
portionate size  of  the  head,  which  at  this  stage  almost  equals  the  trunk  in  bulk.  It 
is  to  be  noted  that  by  the  close  of  the  second  month  the  permanent  organs  are  so 
far  advanced  that  the  subsequent  growth  of  the  fcetus  is  effected  by  the  further  de- 
velopment of  parts  already  formed  and  not  by  the  accession  of  new  organs.  The 
beginning  of  the  second  month  marks  the  period  of  greatest  relative  growth;  at 
the  end  of  this  month  the  fcetus  measures  about  thirty  millimetres  in  its  longest 
dimension. 


STAGE    OF    THE    FCETUS.  65 

The  third  month  is  characterized  by  greater  perfection  of  the  external  form, 
the  rounded  head  is  raised  from  the  trunk  so  that  a  distinct  neck  appears,  while  the 
thorax  and  abdomen  are  less  prominent  ;  the  limbs,  which  are  well  developed  with 
completed  differentiation  of  the  fingers  and  toes,  provided  with  imperfect  nails,  now 
assume  the  characteristic  fcetal  attitude.  The  eyelids  become  united  by  the  tenth 
week,  remaining  closed  until  the  end  of  the  seventh  month.  The  cloacal  opening 
becomes  differentiated  during  the  ninth  and  tenth  weeks  into  the  genito-urinary  and 

Fig.  79. 


Umbilical  cord— % 


Umbilical  vesicle 


Human  fcetus  of  aDOut  eight  weeks.    X  3lA-    Amnion  has  been  cut  and  reflected,  but  still  covers  the  umbilical  vesicle 

and  its  stalk. 

the  anal  orifice,  while  during  the  eleventh  and  twelfth  weeks  the  external  genital 
organs  acquire  the  distinguishing  peculiarities  of  a  definite  sex.  The  greatest  length 
of  the  fcetus,  measured  in  its  natural  position  and  excluding  the  limbs,  at  the 
end  of  the  third  month,  is  about  eighty  millimetres  ;  its  weight  approximates  twenty 
grammes. 

The  fourth    month  witnesses  augmented  growth  in  the  fcetus,  whfch,    how- 
ever, resembles  in  its  general  appearance  the  fcetus  of  the  preceding  month.      The 

5 


66  HUMAN    ANATOMY. 

extra-fcetal  portion  of  the  intestinal  canal,  which  at  an  earlier  period  passes  into 
the  umbilical  cord,  duriag  the  fourth  month  recedes  within  the  abdomen.  The 
differentiation  of  sex  is  still  more  sharply  exhibited  by  the  external  organs  :  in  the 
male  the  penis  is  acquiring  a  prepuce,  and  in  the  female  the  labia  majora  and  the 
clitoris  are  becoming  well  developed.  At  the  close  of  this  period  the  foetus  measures 
approximately  150  millimetres  and  weighs  about  120  grammes. 

During  the  fifth  month  the  first  fcetal  movements  are  usually  observed.  The 
heart  and  the  liver  are  relatively  of  large  size.  The  decidua  capsularis  fuses  with 
the  decidua  vera,  thereby  obliterating  the  remains  of  the  uterine  cavity.  The  meco- 
nium within  the  intestinal  canal  shows  traces  of  bile.  The  advent  of  the  fine  hair, 
the  lanugo,  first  upon  the  forehead  and  the  eyebrows,  and  somewhat  later  upon 
the  scalp  and  some  other  parts  of  the  body,  represents  a  conspicuous  advance. 
Likewise  adipose  tissue  appears  in  places  within  the  subcutaneous  layer.  The 
approximate  length,  at  the  end  of  the  fifth  month,  is  twenty-three  centimetres 
and  the  average  weight  about  320  grammes. 

The  sixth  month  is  characterized  by  complete  investment  of  the  body  by 
lanugo  and  by  the  appearance  of  the  vernix  caseosa,  the  protecting  sebaceous  secre- 
tion which  coats  the  body  of  the  fcetus  to  prevent  as  far  as  possible  maceration  of 
the  epidermis  in  the  amniotic  fluid.  The  latter  now  reaches  the  maximum  quantity, 
being  contained  within  the  large  sac  of  the  amnion.  The  sixth  month  is  distin- 
guished by  the  conspicuous  increase  both  in  the  size  and  weight  of  the  fcetus,  and 
is  known,  therefore,  as  the  period  of  gi'eatest  absolute  growth.  At  the  close  of  the 
sixth  month  the  fcetus  measures  approximately  thirty-four  centimetres  in  its  longest 
dimension  and  weighs  about  980  grammes. 

The  seventh  month  is  marked  by  progressive  changes  in  the  various  parts 
of  the  fcetus,  whereby  the  more  advanced  details  become  pronounced  in  the  central 
nervous  system  and  digestive  tract.  The  length  of  the  fcetus  at  the  close  of  the 
seventh  month  approximates  forty  centimetres  and  its  weight  about  1700  grammes. 

The  eighth  month  is  occupied  by  the  continued  growth  and  general  develop- 
ment, as  part  of  which  the  fcetus  acquires  greater  plumpness  than  before  and  a 
brighter  hue  of  the  integument,  now  entirely  covered  with  vernix  caseosa.  The 
lanugo  begins  to  disappear,  while  the  scalp  is  plentifully  supplied  with  hair  ;  the  nails 
have  reached,  or  project  beyond,  the  tips  of  the  fingers.  By  the  close  of  the  eighth 
month  the  foetus  has  attained  a  length  of  about  forty-six  centimetres  and  a  weight 
of  about  2400  grammes. 

The  ninth  month  witnesses  the  gradual  assumption  of  the  characteristics  of 
the  child  at  birth,  among  which  are  the  rounder  contours,  the  extensive,  although 
not  complete,  disappearance  of  the  lanugo,  except  from  the  face,  where  it  largely 
persists  throughout  life,  the  completed  descent  of  the  testicles  within  the  scrotum, 
the  approximation  of  the  labia  majora,  the  permanent  separation  of  the  eyelids,  with 
well-developed  lashes,  and  the  presence  of  dark  greenish  meconium  within  the  in- 
testinal canal.  The  umbilicus  has  reached  a  position  almost  exactly  in  the  middle 
of  the  body.  The  average  length  of  the  fcetus  at  birth  is  about  fifty  centimetres, 
or  twenty  inches  ;  its  average  weight,  while  included  between  widely  varying 
extremes,  may  be  assumed  as  approximately  3100  grammes,  or  6.8  pounds.  The 
weight  of  the  fcetus  at  term  is  materially  influenced  by  the  age  of  the  mother, 
women  of  about  thirty-five  years  giving  birth  to  the  heaviest  children.  The  weight 
and  stature  of  the  mother  probably  also  affect  the  weight  of  the  child.  Repeated 
pregnancies  exert  a  pronounced  effect  upon  the  fcetus,  since  the  weight  of  the  child 
reaches  the  maximum  with  the  fifth  testation. 


The  purpose  of  the  preceding  pages  is  to  present  an  outline  of  the  general 
developmental  processes  leading  to  the  differentiation  and  establishment  of  the  defi- 
nite body-form  of  the  human  embryo  :  a  more  detailed  account  of  the  development 
of  the  various  parts  of  the  body  is  given  in  connection  with  the  descriptions  of  the 
systems  and  the  individual  organs,  to  which  the  reader  is  referred. 


THE    ELEMENTARY    TISSUES. 

The  various  parts  and  organs  of  the  complex  body  may  be  resolved,  in  their 
morphological  constitution,  into  a  few  component  or  elementary  tissues,  of  which 
there  are  four  principal  groups, — the  epithelial,  the  connective,  the  muscular,  and 
the  nervous  tissues.  The  first  two  of  these  may  be  discussed  at  this  place  ;  the  re- 
maining groups,  the  muscular  and  the  nervous  tissues,  are  considered  most  advan- 
tageously in  connection  with  the  muscular  and  nervous  systems  to  which  they  are 
directly  related  and  under  which  sections  they  will  be  found. 

THE    EPITHELIAL    TISSUES. 

The  epithelial  tissues  include,  primarily,  the  integumentary  sheet  of  protecting 
cells  covering  the  exterior  of  the  body  and  the  epithelium  lining  the  digestive  tube. 
Secondarily,  they  embrace  the  epithelial  derivatives  of  the  epidermis,  such  as  the 
nails,  hairs,  and  glands  of  the  skin  and  its  extensions,  and  the  epithelial  lining  of 
the  ducts  and  compartments  of  the  glands  formed  as  outgrowths  from  the  primi- 
tive gut-tube,  as  well  as  the  epithelium  clothing  the  respiratory  tract  which  originates 
as  an  evagination  from  the  digestive  canal. 

An  apparent  exception  to  the  usual  origin  of  the  epithelial  tissues  from  either 
the  ectoblast  or  the  entoblast  is  presented  by  the  lining  of  the  genito-urinary  tract, 
since  all  the  epithelium  occurring  in  connection  with  these  organs,  as  far  as  the 
bladder,  is  of  mesoblastic  origin,  and  hence  genetically  related  closely  with  the 
extensive  mesoblastic  group  of  tissues.  It  is  to  be  noted  in  this  connection  that  the 
epithelium  of  the  bladder  and  of  a  part  of  the  urethra  is  derived  from  outgrowths  of 
the  primary  gut,  and  therefore  is  entoblastic  in  origin. 

The  primary  purpose  of  epithelium  being  protection  of  the  more  delicate 
vascular  and  nervous  structures  lying  within  the  subjacent  connective  tissue  of  the 
integument  or  of  the  mucous  membrane,  the  protecting  cells  are  arranged  as  a  con- 
tinuous sheet,  the  individual  elements  being  united  by  a  small  amount  of  inter- 
cellular substance. 

Epithelium  contains  no  blood-vessels,  the  necessary  nutrition  of  the  tissue  being 
maintained  by  the  absorption  of  the  nutritive  juices  which  pass  to -the  cells  by  way 
of  the  minute  clefts  within  the  intercellular  substance.  Likewise,  the  supply  of 
nerve-fibres  within  epithelium  ordinarily  is  scanty,  although  in  certain  localities 
possessing  a  high  degree  of  sensibility,  as  the  cornea  or  tactile  surfaces,  the  termi- 
nations of  the  nerves  may  lie  between  the  epithelial  elements. 

The  epithelial  tissues  are  frequently  separated  from  the  subjacent  connective 
tissue  by  a  delicate  basement  membrane ,  or  membrana  propria  ;  the  latter,  which  may 
be  regarded  as  a  derivative  or  modification  of  the  connective  tissue,  usually  appears 
as  a  delicate  subepithelial  boundary,  being  particularly  well  marked  beneath  the 
epithelium  of  glands. 

According  to  the  predominating  form  of  the  component  cells,  the  epithelial 
tissues  are  best  divided  into  two  chief  groups,  — squamous  and  columnar, — with  sub- 
divisions as  shown  in  the  following  table  : 

VARIETIES   OF   EPITHELIUM. 

I.— Squamous  : 

a.  Simple, — consisting  of  a  single  layer. 

b.  Stratified, — consisting  of  several  layers. 
II. — Columnar  : 

a.  Simple, — consisting  of  a  single  layer. 

b.  Stratified, — consisting  of  several  layers. 
III. — Modified  : 

a.  Ciliated,     b.   Goblet,     c.   Pigmented. 
IV. — Specialized  : 

a.  Glandular  epithelium,     b.  Neuro-epithelium. 


68 


HUMAN   ANATOMY. 


Squamous  epithelium,  when  occurring  as  a  single  layer,  is  composed  of 
flattened  polyhedral  nucleated  plates  which,  when  viewed  from  the  surface,  present 
a  regular  mosaic,  sometimes  described  by  the  terms  "pavement"  or  "tessellated." 
Such  arrangement  of  the  squamous  type  is  unusual  in  the  human  body,  the  lining 
of  the  alveoli  of  the  lungs,  the  posterior  surface  of  the  anterior  capsule  of  the 
crystalline  lens,  the  membranous  labyrinth,  and  a  few  other  localities  being  the 
chief  places  where  a  single  layer  of  squamous  cells  occurs. 

The  far  more  usual  arrangement  of  such  cells  is  several  superimposed  layers, 
this    constituting    the    important   group   of   stratified   squamous    epithelia.      When 

Fig.  Si. 


Fig.  80. 


Cvy 


m  ®  <gj  ' 


Simple  squamous  epithelium  from 
anterior  capsule  of  crystalline  lens. 
X  400. 


Section  of  stratified  squamous  epithelium  from  anterior  surface  of 
X  5°°- 


seen  in  section,  the  deepest  cells  are  not  scaly,  but  irregularly  columnar,  resting 
upon  the  basement  membrane  by  slightly  expanded  bases.  The  surface  of  the  un- 
derlying connective  tissue  supporting  this  variety  of  epithelium  is  beset  with  minute 
elevations  or  papilla?,  which  serve  as  advantageous  positions  for  the  terminations  of 
the  blood-vessels,  as  well  as  specialized  nerve-endings.  Owing  to  the  more  favored 
nutrition  of  the  deepest  stratum,  the  cells  next  the  connective  tissue  exhibit  the 
greatest  vitality,  and  often  are  the  exclusive  source  of  the  new  elements  necessary. 


Fig.  S2. 


Fig.  83. 


gSMfl 


Isolated  surface   cells  from   epithe- 
lium lining  the  mouth.     X  350. 


Epithelial  cells  from  epider- 
mis, showing  intercellular  bridges. 
X675. 


to  replace  the  old  and  effete  cells  which  are  continually  being  removed  at  the  free 
surface  ;  this  loss  is  due  not  only  to  mechanical  abrasion,  but  also  to  the  displace- 
ment of  the  superficial  elements  by  the  new  cells  formed  within  the  deeper  layers. 

Passing  from  the  basement  membrane  towards  the  free  surface,  the  form  of  the 
cells  undergoes  a  radical  change.  The  columnar  type  belongs  to  the  deepest  layer 
alone  ;  the  superimposed  cells  assume  irregularly  polyhedral  forms  and  then  gradu- 
ally expand  in  the  direction  parallel  to  the  free  surface  to  become,  finally,  converted 
into  the  large,  thin  scales  so  characteristic  of  the  superficial  layers  of  stratified 
epithelium.      The  position  of  the  nucleus  also  varies  with  the  situation  of  the  cells, 


EPITHELIUM. 


69 


since  within  those  next  the  basement  membrane  the  relatively  large  nucleus — the 
nutritive  organ  of  the  cell — occupies  the  end  nearest  the  subjacent  connective  tissue  ; 
in  the  middle  and  superficial  strata,  the  nucleus,  comparatively  small  in  size,  is 
placed  about  the  centre  of  the  cell. 

The  irregularly  polyhedral  cells  of  the  deep  or  middle  strata  frequently  are 
connected  by  delicate  processes  which  bridge  the  intervening  intercellular  clefts  ; 
when  such  elements  are  isolated,  the  delicate  connecting  threads  are  broken  and  the 
disassociated  elements  appear  beset  with  minute  spines,  then  constituting  the  prickle- 
cells. 

In  certain  localities,  as  in  the  urinary  bladder,  the  columnar  cells  of  the  deepest 
layer  rapidly  assume  the  scaly  character  of  the  superficial  strata  ;  such  epithelium 


m  ■ 


Fig.  85. 


liiwiiil 


Transitional  epithelium  from  bladder  of  child. 
X  300. 


Simple  columnar  epi- 
thelium from  intestinal 
mucosa.     X  750. 


possesses  relatively  few  layers,  and  from  the  readiness  with  which  the  type  of  the 
cells  changes,  is  often  described  as  transitio?ial  epithelium ;  the  latter  cannot  be 
regarded  as  a  distinct  variety,  but  only  as  a  modification  of  the  stratified  scaly  group. 
Columnar  epithelium,  when  occurring  as  a  single  layer  of  cells,  constitutes 
the  simple  columnar  variety,  which  enjoys  a  much  wider  distribution  than  the  cor- 
responding squamous  group,  the  lining  of  the  stomach  and  of  the  intestinal  tube 
being  important  examples.  When  the  single  layer  of  such  epithelial  tissues  is  re- 
placed by  several,  as  in  the  stratified  columnar  variety,  the  superficial  cells  alone 


Fig.  S7. 


4J 


.  from  trachea  of 


\   ■■■■  :i;h:  A^A'V  Z.\  \ 


Ciliated  epithelial  cells.    A,irom  i 
tine  of  a  mollusk  {cyclas) ;    B,  from  nasal 
cavity  of  frog.     X  750.     {Engelmann.) 


are  typically  columnar.  The  free  ends  of  the  columnar  elements  not  infrequently 
present  specializations  in  the  form  of  a  cuticidar  border  or  of  cilia,  while  their  ends 
which  rest  upon  the  basement  membrane  are  pointed,  forked,  or  club-shaped.  The 
intervals  thus  formed  by  irregularities  of  contour  are  occupied  by  the  cells  of  the 
deeper  stratum  next  the  basement  membrane.  Each  cell  is  provided  with  a  nucleus, 
which  is  situated  about  midway  between  the  ends  of  the  superficial  elements  and 
nearer  the  base  within  the  deeper  ones.  The  surface  cells  often  contain  collections 
of  mucous  secretion  which  distend  their  bodies  into  conspicuous  chalice  forms  known 
as  goblet-cells,  which  occur  in  great  profusion  in  the  lining  of  the  large  intestine  and 
the  respiratory  mucous  membrane. 


7o 


HUMAN    ANATOMY. 


Fig.  89. 


Goblet-cells  from  epithelium 
intestine.    X  500. 


Modified  Epithelium. — The  free  surface  of  the  epithelium  in  many  localities, 
as  in  the  trachea,  the  inferior  and  middle  nasal  meatuses,  and  the  uterus,  is  pro- 
vided with  minute,  hair-like  vibratile  processes,  or  cilia,  which  are  produced  by  the 
specialization  of  the  cytoplasm  of  the  free  end  of  the  cell.  The  exact  relations  of 
the  cilia  to  the  cytoplasm  are  still  matters  of  uncertainty,  although  the  investigations 
of  Engelmann  and  others  on  the  ciliated  epithelium  of  invertebrates  render  it  prob- 
able that  the  hair-like  processes  attached  to  the  cells  of  higher  animals  are  also 
connected  with  intracellular  fibrillae,  which  appear  as  delicate  striations  within  the 
superficial  and  more  highly  specialized  parts  of  the  cells.  In  man  and  the  higher 
mammals  ciliated  epithelium  is  limited  to  the  columnar  variety.  The  exact  number 
of  individual  cilia  attached  to  the  free  surface  of  each  cell  varies,  but  there  are  usually 
between  one  and  two  dozen  such  appendages.  Their 
length,  likewise,  differs  with  locality,  those  lining 
the  epididymis  being  about  ten  times  longer  than 
those  attached  to  the  tracheal  mucous  membrane. 
When  favorable  conditions  obtain,  including  a  suffi- 
cient supply  of  moisture,  oxygen,  and  heat,  ciliary 
motion  may  continue  for  many  hours  and  even  days. 
On  surfaces  clothed  with  columnar  epithelium 
certain  cells  are  distinguished  by  unusually  clear 
.  cytoplasm  and  exceptional  form  and  size  ;  these  are 
the  goblet-cells,  the  peculiar  elliptical  or  chalice 
form  of  which  results  from  the  accumulation  of  the 
mucoid  secretion  elaborated  within  their  protoplasm.  When  the  distention  becomes 
too  great  the  cell  ruptures  in  the  direction  of  least  resistance,  and  the  secretion  is 
poured  out  upon  the  surface  of  the  mucous  membrane  as  the  lubricating  mucus. 
The  goblet-cells,  therefore,  may  be  regarded  as  unicellular  glands,  and  represent  the 
simplest  phase  in  the  specialization  of  glandular  tissues. 

The  protoplasm  of  epithelial  cells  often  becomes  invaded  by  particles  of  foreign 
substances  ;  thus,  granules  of  fatty  and  proteid  matters  are  very  commonly  encoun- 
tered, while  the  presence  of  granules  of  eleidin  in  certain  cells  of  the  epidermis  char- 
acterizes the  stratum  granulosum.  When  the  invading  particles  are  colored,  as  when 
composed  of  melanin,  the  affected  cells  acquire  a  dark  brown  tint,  and  are  then  known 
as  pigmented  epithelium.  Examples  of  such  cells  are  seen  in  the 
retina  and  in  the  deeper  cells  of  the  epidermis  in  certain  races. 
Specialized  Epithelium. — Reference  has  already  been 
made  to  goblet-cells  as  representing  unicellular  glands  ;  these 
may  be  regarded,  therefore,  as  instances  of  a  temporary 
specialization  of  epithelium  into  glandular  tissue.  When  the 
epithelial  elements  become  permanently  modified  to  engage  in 
the  elaboration  of  secretory  substances,  they  are  recognized 
as  glandular  epithelium.  The  cells  lining  the  ducts  and  the 
ultimate  compartments  of  glands  are  modified  extensions  of 
the  epithelial  investment  of  the  adjacent  mucous  membrane. 
Their  form  and  condition  depend  upon  the  degree  of  speciali- 
zation, varying  from  columnar  to  spherical  and  polyhedral,  on 
the  one  hand,  and  upon  the  nature  and  number  of  the  secre- 
tion particles  on  the  other.  The  cells  lining  parts  of  certain  glands,  as  those  clothing 
the  ducts  of  the  salivary  glands,  or  the  irregular  portion  of  the  uriniferous  tubules, 
exhibit  a  more  or  less  pronounced  striation  ;  cells  presenting  this  peculiarity  are 
termed  rod-epithelium. 

The  highest,  and  often  exceedingly  complex,  specializations  affecting  epithelial 
tissues  are  encountered  in  connection  with  the  neurones  supplying  the  organs  of 
special  sense.  The  epithelium  in  these  localities  is  differentiated  into  two  groups  of 
elements, — the  sustentacular  and  the  perceptive  ;  to  the  latter  the  name  of  neuro- 
epithelium  is  applied.  Conspicuous  examples  of  such  specialization  are  the  rod-  and 
cone-cells  of  the  retina  and  the  hair-cells  of  Corti's  organ  in  the  internal  ear. 

A  more  detailed  description  of  the  glandular  tissues  is  given  with  the  digestive 
tract  ;  that  of  the  neuro-epithelia  with  the  organs  of  special  sense. 


Fig.  90. 


Pigmented  epithelium  from 
human  retina.     X  435- 


ENDOTHELIAL   TISSUES. 


7' 


*.     X  300.     Intercellular 
rgentic  nitrate. 


ENDOTHELIUM. 

The  modified  mesoblastic,  later  connective-tissue,  cells  that  line  serous  surfaces, 
including  those  of  the  pericardial,  the  pleural,  and  the  peritoneal  divisions  of  the 
body-cavity,  together  with  those  of  the  blood-  and  lymph-vessels  and  the  lymphatic 
spaces  throughout  the  body,  constitute  endothelium.  These  spaces,  in  principle,  are 
intramesoblastic  clefts  and  the  elements  forming  their  lining  are  derivatives  of  the 
great  connective-tissue  layer.  The  endothelia,  therefore,  belong  to  the  connective 
tissues  and  are  properly  regarded  as 

modified  elements  of  that  class  ;  as  Fro.  91. 

a  matter  of  convenience,  however, 
they  may  be  considered  at  this  place 
in  connection  with  the  epithelial  tis- 
sues. 

The  most  striking  difference  in 
situation  between  the  endothelia  and 
the  epithelia  is  found  in  the  fact  that 
the  former  cover  surfaces  not  com- 
municating with  the  atmosphere, 
while  the  epithelial  tissues  clothe 
mucous  membranes  all  of  which  are 
directly  or  indirectly  continuous 
with  the  integumentary  surface.  A 
further  contrast  between  these  tis- 
sues is  presented  in  their  genetic  re- 
lations with  the  primary  blastodermic 
layers,  since  the  epithelia,  with  the 
exception  of  those  lining  certain 
parts  of  the  genito-urinary  tracts  which  are  derived  from  the  mesoblast,  are  the  trans- 
formations and  outgrowths  from  the  ectoblast  and  the  entoblast,  while  the  endo- 
thelia are  direct  modifications  of  the  mesoblastic  cells. 

The  young  mesoblastic  cells  bordering  the  early  body-cavity  become  differenti- 
ated into  a  delicate  lining,  the  mesothelium,   and  later  give  rise  to  the  characteristic 

plate-like    elements   which    constitute    the 
Fig.  92.  lining  of  the  permanent  serous  sacs.      The 

name  mesothelium  is  sometimes  retained  to 
designate  the  permanent  investment  of  the 
great  serous  cavities,  as  distinguished  from 
the  endothelium  which  clothes  the  vascular 
and  other  serous  spaces. 

Seen  in  typical  preparations,  as  ob- 
tained from  the  peritoneum  after  treatment 
with  argentic  nitrate  and  subsequent  stain- 
ing with  heematoxylin,  the  endothelial  cells 
on  surface  view  appear  as  irregularly  polyg- 
onal areas  mapped  out  by  deeply  tinted 
lines.  The  latter  represent  the  silver- 
,  „  ...     „  ,.  .  .  ,        .,      .,  stained    albuminous    intercellular    cement- 

Endothehal  cells  lining  artery  01  dog,  after  silver  .  .  in  j         n 

staining,   x  500.  substance  which   unites  the  flattened  cells 

in  a  manner  similar  to  that  observed  in 
simple  squamous  epithelium  ;  this  superficial  likeness  is  so  marked  that  it  has  led  to 
much  confusion  as  to  the  proper  classification  of  endothelium  under  the  connective 
tissues.  The  lines  of  apposition  are  sinuous  and  less  regular  than  between  epithelial 
elements,  in  many  cases  appearing  distinctly  dentated.  The  exact  form  of  the  cells 
and  the  character  of  their  contours,  however,  are  not  constant,  since  they  probably 
depend  largely  upon  the  degree  of  tension  to  which  the  tissue  has  been  subjected. 

Not  infrequently  the  intercellular  substance,  at  points  where  several  endothelial 
cells  are  in  apposition,  shows  irregular,  deeply  colored  areas  after  silver  staining  ; 


72  HUMAN   ANATOMY. 

these  figures  are  described  as  stigmata  or  pseudostomata,  and  by  some  are  interpreted 
as  indications  of  the  existence  of  openings  leading  from  the  serous  cavity  into  the 
subjacent  lymphatics.  Critical  examination  of  these  areas,  however,  leads  to  the 
conclusion  that  they  are  largely  accidental,  and  due  to  dense  local  accumulations  of 
the  stained  intercellular  materials  ;  they  are  not,  therefore,  to  be  regarded  as  intercellu- 
lar passages.  True  orifices  or  stomata,  however,  undoubtedly  exist  in  certain  serous 
membranes,  as  in  the  septum  between  the  peritoneal  cavity  and  the  abdominal 
lymph-sac  of  the  frog,  and,  possibly,  the  peritoneal  surface  of  the  diaphragm  of 
mammals.  The  positions  of  these  stomata  are  marked  by  a  conspicuous  modification 
in  the  form  and  arrangement  of  the  surrounding  endothelial  plates,  which  exhibit  a 
radial  disposition  about  the  centres  occupied  by  the  stomata.  The  immediate  walls 
of  the  orifices  are  formed  by  smaller  and  more  granular  elements,  the  guard  or  ger- 
minating cells,  the  contraction  and  expansion  of  which  probably  modify  the  size  of 
the  openings. 

Although  the  ectoblast  and  the  entoblast  are  the  germ  layers  which  furnish  great 
tracts  of  epithelium  in  the  adult  body,  yet  the  mesoblast,  the  middle  germ  layer, 
also  supplies  distinct  epithelial  tissues.  As  it  has  been  already  pointed  out,  the 
epidermis,  the  epithelial  portion  of  the  skin,  with  its  derivatives,  is  a  product  of  the 
ectoblast.  The  epithelial  lining  of  the  mouth  cavity  as  far  back  as  the  region  of  the 
palatine  arches,  and  the  epithelium  of  the  anus  are  also  of  ectoblastic  origin,  since 
they  are  formed  as  in-pocketings  of  the  outer  germ  layer  during  early  embryonic 
life.  With  the  exception  of  these  areas,  the  epithelium  lining  the  entire  digestive 
tube,  and  that  of  its  accessory  glands,  notably  the  liver  and  the  pancreas,  is  of 
entoblastic  origin.  The  same  thing  is  true  of  the  epithelium  of  the  respiratory  tract, 
since  this  entire  tract  is  an  outgrowth  from  the  primitive  intestine.  But  in  the  case  of 
the  uro-genital  system,  the  epithelium  there  found,  or  most  of  it,  is  derived  directly 
from  the  mesoblast.  To  be  more  specific,  the  Fallopian  tubes  (uterine  tubes), 
uterus  and  vagina  of  the  female,  which  have,  of  course,  a  distinct  layer  of  epithelium 
on  their  inner  surface,  are  formed  from  certain  embryonic  tubes  known  as  the 
Miillerian  ducts,  which  are  derived  from  the  mesoblast.  The  vas  (ductus)  deferens 
of  the  male  is  first  represented  in  the  embryo  by  a  tube  known  as  the  Wolffian  duct, 
which,  with  its  epithelium,  is  also  derived  from  the  mesoblast.  The  sex-cells  found  in 
the  sex -glands,  which  in  the  case  of  the  male  retain  a  distinct  epithelial  character, 
are  apparently  of  mesoblastic  origin.  The  ureter  and  part  of  the  kidney  are  out- 
growths from  the  Wolffian  duct  and  therefore  mesoblastic,  while  the  rest  of  the 
kidney  not  formed  in  this  way  is  also  of  mesoblastic  origin.  Hence,  it  is  evident 
that  distinct  layers  of  epithelium  are  formed'  from  all  three  germ  layers,  and  that 
in  this  respect  no  peculiarity  is  attributable  to  any  one  of  them. 


THE   CONNECTIVE  TISSUES. 


Fig.  93. 


7';% 


The  important  group  of  connective  substances  the  most  widely  distributed  of 
all  tissues,  is  the  direct  product  of  the  great  mesoblastic  tract  ;  the  several  members 
of  this  extended  family  are  formed  by  the  differentiation  and  specialization  of  the 
intercellular  substance  wrought  through  the  more  or  less  direct  agency  of  the  meso- 
blastic cells.  The  variation  in  the  physical  characteristics  of  the  connective  tissues 
is  due  to  the  condition  of  their  intercellular  constituents.  During  the  period  of  em- 
bryonal growth  these  latter  are  represented  by  gelatinous,  plastic  substances  ;  a 
little  later  by  the  still  soft,  although  more  definitely  formed,  growing  connective 
tissue,  which,  in  turn,  soon  gives  place  to  the  yielding,  although  strong,  adult 
areolar  tissue. 

Grouped  as  masses  in  which  white  fibrous  tissue  predominates,  the  intercellular 
substance  presents  the  marked  toughness  and  inextensibility  of  tendon  ;  where,  on 
the  contrary,  large  quantities  of  yellow  elastic  tissue  are  present,  extensibility  is 
conspicuous.  Further  conden- 
sation of  the  intercellular  sub- 
stance produces  the  resistance 
encountered  in  hyaline  carti- 
lage, intermediate  degrees  of 
condensation  being  presented 
by  the  fibrous  and  elastic  varie- 
ties. In  those  cases  in  which 
the  ground-substance  becomes 
additionally  impregnated  with 
calcareous  salts,  the  well-known 
hardness  of  bone  or  dentine  is 
attained.  Notwithstanding  these 
variations  in  the  density  of  the 
intercellular  substance,  the  cel- 
lular elements  have  undergone 
but  little  change,  the  connective- 
tissue  corpuscle,  the  tendon-cell, 
the  cartilage- cell,  and  the  bone- 
corpuscle  being  morphologically 
identical. 

The  principal  forms  in  which  the  connective  substances  occur  may  be  grouped  as 
follows  : 

1.  Immature  connective  tissue,  as  the  jelly  of  Wharton  in  the  umbilical  cord 
and  the  tissues  of  embryos  and  of  young  animals. 

2.  Areolar  tissue,  forming  the  subcutaneous  layer  and  filling  intermuscular 
spaces,  and  holding  in  place  the  various  organs. 

3.  Dense  fibro-elastic  tissue,  found  in  the  fascia?,  the  sclera,  the  ligaments,  etc. 
Where  white  fibrous  tissue  predominates  and  yellow  elastic  tissue  is  practically 
wanting,  structures  of  the  character  of  tendon  or  of  the  cornea  are  produced  ;  where, 
on  the  other  hand,  elastic  tissue  is  in  excess  of  fibrous  tissue,  highly  extensible 
structures,  as  the  ligamentum  nuchae  or  the  ligamenta  subflava,  result. 

4.  Cartilage,  fibrous,  elastic,  and  hyaline  varieties. 

5.  Bone  and  dentine,  in  which  impregnation  of  lime  salts  contributes  character- 
istic hardness. 

6.  Reticulated  connective  tissue,  occurring  as  the  supporting  framework  in  the 
lymphatic  tissues,  and  as  the  interstitial  reticulum  of  many  organs. 

7.  Adipose  tissue. 

The  Cells  of  Connective  Tissue. — The  cellular  elements  of  the  connective 

73 


nbryonal  connective-tissue  cells  from  the  umbilical  cord.     X  500. 


74 


HUMAN    ANATOMY. 


tissues  are  usually  described  as  of  two  kinds, — the  fixed  or  connective-tissue  cells 
proper,  and  the  migratory  or  wandering  cells.  The  latter,  while  frequently  included 
among  the  elements  of  these  tissues,  are  usually  only  migratory  leucocytes  which 
temporarily  occupy  the  lymphatic  clefts  within  the  connective  substance. 


Fig.  94. 


Fig.  95. 


SPs^sg 


Young    connectn 
from    subcutaneous 
embryo.     X  590. 


Granule-cells  (mast-cells)  from  subn 


,  sections  of  blood-vessels. 


Fig.  96. 


-Connective- 
tissue  cell 
(Fixed  cell) 


The  typical  connective-tissue  cell,  in  its  younger  condition,  possesses  a  flattened, 
plate-like  body  from  which  branched  processes  extend.     With  the  completed  growth 

of  the  tissue,  the  expanded, 
often  irregularly  stellate, 
element  contracts  to  the 
inconspicuous  spindle  cell 
commonly  observed  in  adult 
areolar  tissue. 

Gra?iule-cells  are  addi- 
tional elements  occasionally 
encountered  in  connective 
tissues.  They  are  irregularly 
spherical  in  form  and  are  dis- 
tinguished by  conspicuous 
granules  within  their  proto- 
plasm possessing  a  strong 
affinity  for  dahlia  and  other 
basic  aniline  stains.  They 
include  the  plasma-cells  of 
Waldeyer  and  the  mast-cells 
of  Ehrlich. 

Pigment-Cells. — The 
fixed  cells  sometimes  contain 
accumulations  of  dark  parti- 
cles within  their  cytoplasm, 
the  elements  then  appearing 
as  large,  irregularly  branched 
pigment-cells ;  these  are  con- 
spicuous in  man  within  the  choroid,  the  iris,  and  certain  parts  of  the  pia  mater. 
The  nucleus  usually  remains  uninvaded,  and  hence  appears  as  a  lighter  area  within 
the  dark  brown,  or  almost  black,  cell-body. 

The  Intercellular  Constituents  of  the  connective  substances  occur  in  three 
forms, — -fibrous  tissue,  reticular  tissue,  and  elastic  tissue. 

Fibrous  tissue  consists  morphologically  of  varying  bundles  of  silky  fibrils  of 


J 


1  of  subcutaneous  tissue,  showing  the 
tissue.     X  3°°. 


usual  constituents  of  areola 


FIBROUS   TISSUE. 


75 


such  fineness  that  they  possess  no  appreciable  width.  The  fibrils  are  united  by  and 
embedded  within  a  semifluid  ground-substance,  which  may  be  present  in  such  meagre 
amount  that  it  suffices  only  to  hold  together  the  fibrillse,  or,  on  the  other  hand,  it 
may  constitute  a  large  part  of  the  entire  intercellular  tissue,  as  in  the  matrix  of  hya- 


Fig.  97. 


Fig.  98. 


cells  from  choroid. 


r: 


--V- 


■J 


Surface  view  of  portion  of  oment 
brous  and  elastic  tissue  are  arranged 
membrane;  the  nuclei  belong  to  the 
and  the  endothelial  cells. 


line  cartilage.  Depending  upon  the  dis- 
position of  the  bundles,  fibrous  tissue 
occurs  in  two  principal  varieties, — areolar  ^***Ot#'S^, 

and  dense  connective  tissue. 

The  fibrous  tissue  of  the  areolar 
group  is  arranged  in  delicate  wavy  bun- 
dles which  are  loosely  and  irregularly  in- 
terwoven, as  seen  in  the  subcutaneous 
layer,  the  intervening  clefts  being  largely 
occupied  by  the  ground-substance.  In 
the  denser  connective  tissues  the  fibrous 
tissue  is  disposed  with  greater  regularity, 
either  as  closely  packed,  parallel  bundles, 
as  in  tendon  and  aponeuroses,  or  as  intimately  felted,  less  regularly  arranged,  bands 
forming  extended  sheets,  as  in  fasciae,  the  cornea,  and  the  dura  mater.  The  ground- 
substance  uniting  the  fibrillar  of  dense  connective  tissues  often  contains  a  system  of 

definite   interfascicular  lymph-spaces, 
Fig.  99.  which,    in   suitably   stained    prepara- 

•  tions,    appear  as    irregularly  stellate 

"•'  _ ,..  " -N        clefts   that   form,    by   union   of    their 

.  ■...    ■:-;."-'.■•  •-'.,'-:?i   i;wA  „-■,.,„  -'      ramifications,  a  continuous  net-work 

fo-«;:.  -  ^  .  . -'    t^r?      -       *^„i<~      V  ..      of  channels  for  the  conveyance  of  the 
.  v|)         '(:.:.■    ^.'%j^^d'  '' Al'L     .~v  i'.^'-'^i      tissue-juices    throughout    the    dense 

f        f.:\~'-\  <r~^:  r"   ■      '"■"-'-:;        (       connective  substances  ;  in  non-vascu- 

lar structures,  as  the  cornea  and  the 
denser  parts  of  bone,  these  systems 
of  intercommunicating  lymph-spaces 
serve  to  convey  the  nutritive  sub- 
'  stances  to  the  connective-tissue  cells 
which  lie  within  these  clefts.  Fibrous 
tissue  yields  gelatin  on  boiling  in 
water,  and  is  not  digested  by  pan- 
creatin  ;  on  the  addition  of  acetic  acid 
this  tissue  becomes  swollen  and  trans- 
parent, the  individual  fibrillas  being 
no  longer  visible. 

Reticular    Tissue. — The    in- 

vestigations  of  Mall  have  emphasized 

the  presence  of  a  modified  form  of  fibrous  tissue  in  many  localities,  especially  in 

organs  rich  in  lymphoid  cells.      This  variety  of  intercellular  substance,   known  as 

reticular  tissue  or  reticulum,  consists  of  very  fine  fibrillar,  either  isolated  or  associated 


/-• 


Cell-spaces  of  d 


^ 


nnective  tissue  from  cornea  of  calf; 


dingground-substance  has  been  stained  with  argen- 


76 


HUMAN   ANATOMY. 


as  small  bundles,  which  unite  in  all  planes  to  form  delicate  net-works  of  great  intri- 
cacy. In  lymphatic  tissues,  where  the  reticulum  reaches  a  typical  development,  the 
mesh-work  contains  the  characteristic  lymphoid  elements  and,  in  addition,  supports 
the  superimposed  stellate  connective-tissue   cells  which  formerly  were  erroneously 

regarded  as  integral  parts  of  the  fibrillar 
PiG   iO0  net-work.       Reticular    tissue,    associated 

with  fibrous  and  elastic  tissue,  is  also 
present  in  many  other  organs,  as  the 
liver,  kidney,  and  lung.  This  modifica- 
tion of  fibrous  tissue  differs  from  the  more 
robustly  developed  form  in  the  absence 
of  the  ground-substance  and  not  yield- 
ing gelatin  upon  boiling  in  water  (Mall); 
like  fibrous  tissue,  the  reticulum  resists 
pancreatic  digestion. 

The  development  of  fibrous  tissue 
has  been  a  subject  of  much  discussion  re- 
garding which  authorities  are  still  far  from 
accord.  Two  distinct  views  are  held  at 
the  present  time  ;  according  to  the  one, 
the  fibres  appear  within  the  originally 
homogeneous  intercellular  matrix  of  the 
early  embryonal  connective  tissue  without 
the  direct  participation  of  the  cells,  the  fibres  being  formed  as  the  result  of  a  process 
somewhat  resembling  coagulation.  This  conception  of  the  formation  of  the  fibres  of 
connective  tissue,  known  as  the  indirect  mode,  is  held  to  account  for  the  earliest 
production  of  the  fibrils  in  embry- 
onic  tissue.  FlG-  WI- 

The  other  view,  held  by  Flem- 
ming,  Reinke,  and  others,  attributes 
an  active  participation  of  the  young 
connective  tissue  cell,  the  peripheral 
zone  of  its  protoplasm,  known  as  ex- 
oplasm,  being  directly  transformed 
into  fibrillar.  In  consideration  of 
the  careful  observations  of  Hem- 
ming, it  is  now  generally  believed 
that  the  method  of  formation  of  the 
fibres  of  connective  tissue  directly 
from  the  exoplasm  of  young  con- 
nective tissue  cells  is  the  usual  one. 
It  is  highly  probable  that  the 
connective  tissue  cells  are  concerned 
in  the  production  of  the  fibrous 
tissue,  since  these  elements  become 
much  smaller  as  the  formation  of 
the  fibrous  tissue  advances. 

Elastic  tissue  usually  occurs 
as  a  net-work  of  highly  refracting, 
homogeneous  fibres  lying  among  the 
bundles  of  fibrous  tissue.  The  indi- 
vidual fibres  are  much  thicker  than 
the    fibrillae    of    fibrous    tissue   and,- 

although  differing  in  width,  maintain  a  constant  diameter  until  augmented  by  fusion 
with  others.  When  disassociated,  as  in  teased  preparations,  the  elastic  fibres  assume 
a  highly  characteristic  form,  being  wavy,  bowed,  or  coiled.  The  proportion  of  elastic 
tissue  in  connective  substances  is,  ordinarily,  small  ;  in  certain  localities,  however,  as 
the  ligamenta  subflava  of  man,  or  especially  the  ligamentum  nucha;  of  the  lower 
mammals,  almost  the  entire  structure  consists  of  bundles  of  robust  fibres  of  elastic 


Fibrous  and  reticular  connective  tissue  from  hu 
pancreatic  digestion.     X  230. 


ELASTIC   TISSUE. 


77 


tissue  held  together  by  a  small  amount  of  intervening  fibrous  tissue.  In  transverse 
section  of  such  ligaments  (Fig.  104),  the  individual  elastic  fibres  appear  as  minute 
polygonal  areas  separated  by  the  fibrous  fibrillse  and  the  associated  connective-tissue 
cells.      Within  the  walls  of  the  large  blood-vessels  the  elastic  tissue  is  arranged  as 

membranous    expansions    containing    numerous 
Fig.  102.  openings  of  varying  size  :  these  fenestrated  mem- 

branes, as  they  are  called,  are  probably  formed 
by  the  junction  and  fusion  of  broad  ribbon-like 
elastic  fibres.      Elastic  tissue  yields  elastin  upon 


~A2p 


eticular    connective  tis 

X  350.     The  cells  li< 

:  at  the  points  of  intersi 


of  isolated  elastic  fibres  from  ligamen- 
tum  nucha?  of  ox.     X  375- 


boiling  in  water,  and  disappears  upon  being  subjected  to  pancreatic  digestion,  thus 
differing  from  fibrous  and  reticular  tissue  ;  by  taking  advantage  of  the  especial  affinity 
that  elastic  tissue  possesses  for  certain  stains,  as  orcein,  a  much  wider  and  more 
generous  distribution  of  elastic  tissue  has  been  established  than  was  formerly  appre- 
ciated. 

The   development   of  elastic  tissue  has  shared  the  uncertainty  surrounding 
the  mode  of  production  of  fibrous  tissue,  since  here,  as  there,  two  opposed  views 


Fig.  104. 


have  been  held, — one  of  a  cellular  and 
one  of  an  independent  origin.  Accord- 
ing to  the  view  of  an  independent  o?'igin, 
the  older  one,  the  elastic  fibres  first 
appear  as  rows  of  minute  beads  in  the 
intercellular  matrix.  These  linearly  dis- 
posed beads  gradually  fuse,  thus  produc- 
ing the  primary  elastic  fibres.  According 
to  the  view  of  an  intracellular  origin, 
the  one  now  generally  accepted,  the 
elastic  fibres  are  derived  directly  from 
the  exoplasm  of  the  young  connective 
tissue  cells,  as  in  the  case  of  the  white 
fibrils. 

The  density  of  connective  substances 
depends  upon  the  amount  and  arrange- 
ment of  the  fibrous  tissue  ;  the  extensibility 
is  determined  by  the  proportion  of  elastic 
tissue  present.  When  the  former  occurs 
in   well-defined    bundles,    felted    together 

into  interlacing  lamellae,  dense  and  resistant  structures  result,  as  fasciae,  the  cornea, 
etc. ;  in  such  structures  the  cement-  or  ground-substance  within  the  interfascic- 
ular clefts  usually  contains  the  lymph-spaces  occupied  by  the  connective-tissue 
cells. 

Tendon. — Tendon  consists  of  dense   connective  tissue  composed  almost  en- 
tirely of  white  fibrous  tissue  arranged  in  parallel  bundles.      The  individual  fihrillae 


Nucleus 

nective-tissue 
cell 

Transverse  sectu 


78 


HUMAN   ANATOMY. 


of  the  fibrous  tissue,  held  together  by  cement-substance,  are  associated  as  compara- 
tively large  primary  bundles,  which  in  turn  are  united  by  interfascicular  ground- 

Fig.  105. 


Tendon-bundle 


Oblique 


Longitudinal  secliuu  of  tendon  from   young  subject;         Tendon-bundles  from  tailor  mouse,  showing  different 
the  tendon-cells  are  seen  in  profile  between  the  bundles  views  of  the  cells.     X  300. 

of  fibrous  tissue.     X  300. 


substance  and  grouped  into  secondary  bundles. 
areolar  sheath  and  partially  covered  by  plate- 


Fig.  107. 


Blood-vessel  within  septa 
enclosing  tertiary  bundles 


Transverse  section  of  a  tendon,  showing  grouping  of  primary,  s 
and  tertiary  bundles  of  tendon-tissue.     X  85. 

stellate   bodies,    the   extended   limbs  of  which, 
represent  sections  of  the  wing-plates. 

Examined  in  cross-section  (Fig.  107),  the 
dies  appear  as  light  irregular  polygonal  areas 


The  latter,  invested  \>y  a  delicate 
like  cells,  are  held  together  by  the 
septal  extensions  of  the 
general  connective-tissue 
envelope  which  surrounds 
the  entire  tendon  ;  the 
larger  septa  support  the 
interfascicular  blood-ves- 
sels and  the  lymphatics. 

The  flattened  connec- 
tive-tissue elements,  here 
known  as  the  tendo?i-ce//s, 
occur  in  rows  within  the 
clefts  between  the  primary 
bundles,  upon  and  between 
which  the  thin,  plate-like 
bodies  and  wings  of  the 
tendon-cells  expand.  Seen 
from  the  surface,  these 
cells  appear  as  nucleated 
quadrate  bodies  (Fig. 
„  .  106)  ;  viewed  in  longitudi- 

Primary  ,  ft  i  11 

bundle  nal  profile,  the  tendon-cells 
present  narrow  rectangular 
areas,  while,  when  seen  in 

econdarv,  .  , 

transverse      section,      the 

same   elements   appear  as 

often  stretching  in  several  planes, 

cut  ends  of  the  primarv  tendon-bun- 
.,  which,  under  high  amplification,  at 


ADIPOSE   TISSUE. 


79 


times  exhibit  a  delicate  stippling  due  to  the  transversely  sectioned  fibrillae.  The 
interfascicular  clefts  frequently  are  represented,  in  such  preparations,  by  stellate 
figures  in  which  the  sections  of  the  tendon-cells,  lying  upon  the  primary  bundles,  can 
be  distinguished  ;    the  remaining  portion   of   the  stellate  cleft  is  occupied   by  the 

Fig.   ioS. 


'W     k. 


coagulated  and  stained  interfascicular  cement-substance.      The  larger  divisions  of 
the  tendon,  composed  of  the  groups  of    secondary  bundles,   are  separated  by  the 
septa  prolonged  inward  from  the  general  sheath  investing  the  entire  tendon.      Ten- 
don  is   composed   almost   exclu- 
sively   of    fibrous    tissue,    elastic  F,G-  io9- 
fibres  being  practically  absent. 

Adipose  Tissue. — The 
fatty  material  contained  within 
the  body  is  to  a  large  extent  en- 
closed within  connective-tissue 
cells  in  various  localities  ;  these 
modified  elements  are  known  as 
fat-cells,  which,  together  with 
the  areolar  tissue  connecting  the 
cells  and  supporting  the  rich 
supply  of  blood-vessels,  consti- 
tute the  adipose  tissue. 

The  distribution  of  adipose 
tissue  includes  almost  all  parts  of 
the  body,  although  accumulations 
of  fat  are  especially  conspicuous 
in  certain  localities.      Among  the 

latter  are  the  subcutaneous  areolar  tissue,  the  marrow  of  bones,  the  mesentery  and 
the  omentum,  the  areolar  tissue  surrounding  the  kidney,  the  vicinity  of  the  joints,  and 
the  subpericardial  tissue  of  the  heart.  On  the  other  hand,  in  a  few  situations,  in- 
cluding the  subcutaneous  areolar  tissue  of  the  eyelids,  the  penis  and  the  labia 
minora,  the  lungs,  except  near  their  roots,  and  the  interior  of  the  cranium,  adipose 


^AA 


Young  fat-cell- 


Connective-tissiiL' 


Voiina;  fat-cells  fr< 


So  HUMAN   ANATOMY. 

tissue  does  not  occur  even  when  developed  to  excess  in  other  parts.  As  ordinarily 
seen,  adipose  tissue  is  of  a  light  straw  color  and  often  presents  a  granular  texture 
due  to  the  groups  of  fat-cells  within  the  supporting  areolar  tissue. 

Examined  microscopically  in  localities  where  the  fat-cells  are  not  crowded,  but 
occur  in  a  single  stratum  and  hence  retain  their  individual  form,  adipose  tissue  is 
seen  to  be  made  up  of  relatively  large,  clear,  spherical  sacs  held  together  by  deli- 
cate areolar  tissue.  Unless  treated  with  some  stain,  as  osmic  acid,  Sudan  III.  or 
quinoline-blue,  possessing  an  especial  affinity  for  fat,  the  oily  contents  of  the  cells 
appear  transparent  and  uncolored,  and  apparently  occupy  the  entire  cell-body. 
Critical  study  of  the  fat-cell,  however,  demonstrates  the  presence  of  an  extremely 
thin  enveloping  layer  of  protoplasm,  a  local  thickening  on  one  side  of  the' sac  mark- 
ing the  position  of  the  displaced  and  compressed  nucleus  (Fig.  109). 

Fat-cells  occur  usually  in  groups,  supported  and  held  together  by  highly  vas- 
cular connective  tissue.  In  localities  possessing  considerable  masses  of  fat,  as  be- 
neath the  scalp  and  the  skin,  the  cells  are  grouped  into  lobules  which  appear  as 
yellow  granules  to  the  unaided  eye  ;  in  such  localities  the  typical  spherical  shape  of 
the  individual  fat-cells  is  modified  to  a  polyhedral  form  as  the  result  of  the  mutual 
pressure  of  the  closely  packed  vesicles. 

In  connective-tissue  elements  about  to  become  fat-cells,  isolated  minute  oil- 
drops  first  appear  within  the  protoplasm  ;  these  increase  in  size,  coalesce,  and  grad- 
ually encroach  upon  the  cytoplasm  until  the  latter  is  ,reduced  to  a  thin,  almost 
inappreciable,  envelope,  which  invests  the  huge  distending  oil-drop.  The  nucleus, 
likewise,  is  displaced  towards  the  periphery,  where  it  appears  in  profile  as  an  incon- 
spicuous crescent  embedded  within  the  protoplasmic  zone.  After  the  disappearance 
of  the  fatty  matters,  as  during  starvation,  the  majority  of  fat-cells  are  capable  of 
resuming  the  usual  appearance  and  properties  of  connective-tissue  corpuscles  ;  cer- 
tain groups  of  cells,  the  fat-organs  of  Toldt,  however,  exhibit  an  especial  tendency 
to  form  adipose  tissue,  and  hence  only  under  exceptional  conditions  part  with  their 
oily  contents. 

CARTILAGE. 

Cartilage  includes  a  class  of  connective  tissue  in  which  the  intercellular  substance 
undergoes  increasing  condensation  until,  as  in  the  hyaline  variety,  the  intercellular 
matrix  appears  homogeneous,  the  constituent  fibres  being  so  closely  blended  that 
the  fibrous  structure  is  ordinarily  no  longer  appreciable. 

Depending  upon  the  differences  presented  by  the  intercellular  matrix,  three 
varieties  of  cartilage  are  recognized, — hyaline,  elastic,  and  fibrous.  Considered  in 
relation  to  the  denser  connective  tissues,  the  description  of  fibrous  cartilage,  which 
differs  but  little  from  white  fibrous  tissue,  should  next  follow  ;  since,  however,  the 
term  "  cartilage"  is  usually  applied  to  the  hyaline  variety,  the  latter  will  first  claim 
attention. 

Hyaline  cartilage,  or  gristle  (Fig.  no), enjoys  a  wide  distribution,  forming 
the  articular  surfaces  of  the  bones,  the  costal  cartilages,  the  larger  cartilages  of  the 
larynx  and  the  cartilaginous  plates  of  the  trachea  and  bronchi,  the  cartilages  of  the 
nose  and  of  the  Eustachian  tube.  In  the  embryo  the  entire  skeleton,  with  the  ex- 
ception of  part  of  the  skull,  is  mapped  out  by  primary  hyaline  cartilage. 

The  apparently  homogeneous  matrix  of  hyaline  cartilage,  after  appropriate 
treatment,  is  resolvable  into  bundles  of  fibrous  tissue  ;  ordinarily,  however,  these  are 
so  closely  united  and  blended  by  the  cementing  ground-substance  that  the  presence 
of  the  component  fibrils  is  not  evident. 

The  cartilage-cells,  as  the  connective-tissue  elements  which  lie  embedded  within 
the  hyaline  matrix  are  called,  are  irregularly  oval  or  spherical,  nucleated  bodies. 
They  occupy  more  or  less  completely  the  interfascicular  clefts,  or  lacuna?,  within 
which  they  are  lodged.  In  adult  tissue  usually  two  or  more  cells  share  the  same 
compartment,  the  group  representing  the  descendants  from  the  original  occupant  of 
the  space.  The  matrix  immediately  surrounding  the  lacunae  is  specialized  as  a  layer 
of  different  density,  and  is  often  described  as  a  capsule;  a  further  differentiation 
of  the  ground-substance  is  presented  by  the  more  recently  formed  matrix,  which 


CARTILAGE. 


81 


i'^^r — *r- —  Pcrichnndr 


-Young  cartilage- 


often  stains  with  greater  intensity,  thereby  producing  the  appearances  known  as 
the  cell-areas.  The  lacunae  of  hyaline  cartilage  are  homologous  with  the  lymph- 
spaces  of  other  dense  forms  of  connective  tissue  ;  although  canals  establishing  com- 
munication between  the  adjacent  lacunae  are  not  demonstrable  in  the  tissues  of 
the  higher  vertebrates,  it  is  not  improbable  that  minute  interfascicular  passages 
exist  which  facilitate  the  access  of  nutritive  fluids  to  the  cells  enclosed  within  the 
lacunae. 

The  free  surface  of  cartilage  is  covered  by  an  envelope  of  dense  connective 
tissue,  the  perichondrium  ;  the  latter  consists  of  an  external  fibrous  layer  of  dense 
fibro-elastic  tissue  and  an  inner  looser  stratum  or  chondrogenetic  layer,  containing 
numerous  connective-tissue  cells.  These  are  arranged  in  rows  parallel  to  the  sur- 
face of  the  cartilage  and,  during  the  growth  of  the  tissue,  gradually  assume  the 
characteristics  of  the  cartilage-cells,  being  at  first  spindle-shaped  and  later  ovoid 
and  spherical.  The  young  cartilage-cells  thus  formed  become  gradually  separated 
by  more  extensive  tracts  of  the  newly  deposited  intercellular  matrix  ;  as  the  groups  of 
cells  originating  from  the  division  of  the  original  occupant  of  the  lacuna  recede  from 
the  perichondrial  surface,  they 

lose  their  primary  parallel  dis-  Fig.  iio. 

position  and  become  irregu- 
larly arranged  and  still  further 
separated.  Those  portions  of 
the  ground-substance  most  re- 
mote from  the  perichondrium 
at  times  appear  granular,  this 
feature  being- intensified  when, 
as  in  aged  subjects,  a  deposition 
of  calcareous  matter  takes  place 
in  these  situations. 

In  articular  cartilage  the  su- 
perficial zone  contains  sparsely 
distributed  groups  of  small  cells 
arranged  parallel  to  the  free 
surface  ;  in  the  deeper  strata 
these  groups  are  replaced  by 
elongated  rows  of  larger  ele- 
ments lying  perpendicular  to 
the  articular  surface.  This 
columnar  disposition  of  the  car- 
tilage-cells is  particularly  evi- 
dent towards  the  underlying 
zone  of  calcified  matrix. 

The  blood-vessels  of  normal 
cartilage  are  usually  limited  to 
the  periphery,  within  the  perichondrium  or  the  associated  synovial  membranes  ;  the 
nutrition  of  the  cartilage  is  maintained  by  imbibition  of  the  fluids  through  the  matrix 
into  lacunae,  the  existence  of  minute  interfascicular  canals  being  highly  probable. 
In  the  thicker  masses  of  the  tissue,  as  in  the  cartilages  of  the  ribs,  nutrient  canals 
exist  in  those  portions  most  remote  from  the  perichondrium  ;  these  spaces  contain  a 
small  amount  of  areolar  tissue  supporting  the  blood-vessels,  which  are,  however, 
limited  to  the  channels,  the  nutrition  of  the  cartilage  tissue  being  effected  here,  as  at 
the  periphery,  by  absorption  through  the  matrix. 

Nerves  have  never  been  demonstrated  within  the  cartilages,  which  fact  explains 
the  conspicuous  insensibility  of  these  tissues  so  well  adapted  to  the  friction,  concus- 
sion, and  compression  incident  to  their  function. 

Elastic  cartilage,  called  also  yellow  elastic  or  reticular  cartilage  (Fig.  m), 
has  a  limited  distribution,  occurring  principally  in  the  cartilages  of  the  external  ear, 
part  of  the  Eustachian  tube,  the  epiglottis,  the  cartilages  of  Wrisberg  and  of  San- 
torini,  and  part  of  the  arytenoid  cartilages  of  the  larynx.  In  its  physical  properties 
this  variety  differs  markedly  from  hyaline  cartilage,  as  it  is  dull  yellowish  in  color 

6 


w 

P  : 

r^=~. 

'''••* 

Lacuna  contaii 
ing  nest  of 
cells 


Empty  lacuna 
surrounded  by 


#>€)^ 


Transverse  section  of  peripheral  portion  of  costal  cartilage,    X  250. 


82  HUMAN   ANATOMY. 

and  pliable  and  tough  in  consistence,  in  contrast  to  the  bluish  opalescent  tint  and 
comparative  brittleness  of  the  hyaline  variety. 

The  characteristic  feature  of  the  structure  of  the  elastic  cartilage  is  the  presence 
of  elastic  fibres  within  the  intercellular  matrix.  The  cell-nests  are  immediately  sur- 
rounded by  limited  areas  of  hyaline  intercellular  substance  corresponding  to  the 
matrix  of  hyaline  cartilage.  The  matrix  intervening  between  these  homogeneous 
fields,  however,  is  penetrated  by  delicate,  often  intricate,  net-works  of  elastic  fibres 
extending  in  all  directions.  The  connective-tissue  cells  lie  within  the  lacunae,  in  the 
hyaline  areas,  and  closely  resemble  the  elements  of  hyaline  cartilage.  Elastic  carti- 
lage possesses  a  perichondrium  of  the  usual  description. 

Fibrous  cartilage,  or  fibro- cartilage  (Fig.  112),  as  the  fibrous  variety  is  usu- 
ally designated,  is  found  in  comparatively  few  localities,  the  marginal  plates  and  the 
interarticular  disks  of  certain  joints,  the  symphyses,  the  intervertebral  disks,  sesamoid 
cartilages,  and  the  lining  of  bony  grooves  for  tendons  being  its  chief  representatives. 


Elastic  net-work ,/^.!,, '  '*-*■;       ■'  :'.'■  .  \* 

of  intercellular      ^   ~:~'y  ■','-     '       '        '• 
tissue  fr      .iiV',".   \  .    s  '  , 


Lacuna  contain-     i^4^ ?"  #?^    '«    .K ,( ■/;'.  /»  '"S !) !;< 

ingceii  #c::ftt'.-    "        '  Ju/  :-m  ...p.  ''.;  ^  -!■;;.'., 

llfeb      J  V    I 

Section  of  elastic  cartilage  from  the  epiglottis.     X  450. 

In  its  physical  properties  this  tissue  resembles  both  fibrous  tissue  and  cartilage,  pos- 
sessing the  flexibility  and  toughness  of  the  former  combined  with  the  firmness  and 
elasticity  of  the  latter.      A  proper  perichondrium  is  wanting. 

In  structure  fibro-cartilage  closely  resembles  dense  fibrous  tissue,  since  its  prin- 
cipal constituent  is  the  generally  parallel  wavy  bundles  of  fibrous  connective  tissue  ; 
among  the  latter  lie  small,  irregularly  disposed  oval  or  circular  areas  of  hyaline 
matrix  which  surround  the  cartilage-cells,  singly  or  in  groups.  The  number  of  cells 
and  the  proportion  of  fibrous  matrix  differ  in  various  localities. 

The  development  of  cartilage  proceeds  from  the  mesoblast,  the  cells  of  which 
undergo  proliferation  and,  forming  compact  groups,  become  the  embryonal  cartilage- 
cells  ;  at  first  the  latter  lie  in  close  apposition,  since  the  matrix  is  wanting.  During 
the  later  stages,  when  the  masses  of  embryonal  cartilage  map  out  the  subsequent 
skeletal  segments,  the  cells  are  separated  by  a  small  amount  of  homogeneous  matrix 
formed  through  the  influence  of  these  elements. 


DEVELOPMENT   OF   CARTILAGE.  83 

Cartilage  grows  in  two  ways  :   {a)  by  the  expansion  produced  by  the  inter- 
stitial growth    effected  by  the  formation  of  new  cells  and  the  associated  matrix,  and 
(&)   by  the  addition  of  the  new 

tissue    developed    by  perichon-  Fig.  112. 

drial  growth  at  the  periphery  of         .  v.,     ,,,...  .-.v^.^.  ....  ...  ,     ,  .. 

the  cartilage  from  the  chondro-  -,' v  ■;.- '  ' 

genetic  layer.     The  latter  mode  ($|  AH' 

continues  throughout  the  period         ;      ?^.,  "   '--y  -i      V; 

of  growth,  and  includes  the  di-  /,'  •'.-*  ^ 

rect  conversion  of  the  connec-         ;..       ,*2r  '•  ->,/]'..       ""surrounding 

tive-tissue  cells  of  the  perichon-         /<     "      ''.  "  ""  \   '_■  ■-  '      cartilage-cells 

drium  intothecartilage  elements,         \!\,;,\,   .'      '   ]{ti.,'" 

and  the  accompanying  formation         V- *i     <       '•*'■'%>  ''    , 

of  new  matrix.  .■       s        -    m.       .   If,  \        h  ',■■ 

The    development    of    the        ,;i"\    '       -    %;.     .if  ''  ■'.;  ■-'-'. 

elastic  fibres  within   the   elastic        '-!',,,        ~  '*■    'vX;        .  '\-~  )    '■ 

cartilage  is  secondary,  the  matrix         ^    -.,        '    ,    \       %•}         ■    >>.$ 
during  the  early  stages  of  growth        ,V  .\*  ':'■.     \      '%    -     ,    "'.j,— ;-v —         .  ■■•Fibrous  inter- 
being  hyaline.     The  elastic  tis-        ; '  '  (y  •      (■  -k^i         '--  stance 

sue  first  appears  in  the  form  of        s    '  %  I;,-  ^%'-'*- 

minute    granules,     which    later        }( ,    ,.V>S^;  •-       %      '.-■,    x    /'■"'       ;\' 
fuse    and    become    the    elastic        \,      l'^ .;;  «■'  -.  ; 'gs\ 

fibres;  this  change  first  appears        ' ,'.  ■      "  "■  ■.  ;         -        vS3^w      ~'     ~\    ~Cartllaee"cells 
in  the  vicinity  of  the  cartilage-        ,   >.-  "N{\   ';  \  ■    ,     '  -;' 

cells,  the  elastic  reticulum  sub-  '  ;A\ 

sequently  invading  the  more  re- 
mote portions  of  the  matrix.     In  Section  of  fibrous  cartilage  from  intervertebral  disk.    X  225. 

the   development  of   the   fibro- 

cartilage,  the  fibres  appear  coincidently  with  the  limited  pericellular  areas  of  hyaline 

substance. 

Chemical  Composition  of  the  Connective  Substances. 

Connective  Tissue. — The  fibrils  of  white  fibrous  connective  tissue  consist  of  a 
substance  known  as  collagen.  The  interfibrillar  ground-substance  contains  mainly 
mucoid  and  the  albuminous  materials  serum  globuli  and  serum  albumin.  Gelatin  is 
the  hydrate  of  collagen,  and  is  obtained  by  boiling  fibrous  tissue  with  water,  when 
the  gelatin  separates  like  a  jelly  on  cooling.  In  the  case  of  the  yellow  elastic 
fibres,  elastin  is  found  in  place  of  collagen.  In  reticular  tissue  rcticulin  is 
found.  The  latter  substance  contains  phosphorus.  These  substances,  namely, 
collagen  with  its  hydrate  gelatin,  elastin  and  perhaps  reticulin,  are  among  those 
known  as  albuminoids,  which  are  closely  related  to  the  true  albumins,  yet  differ  in 
some  important  respects.  The  albuminoids,  for  the  most  part,  contain  less  carbon 
and  more  oxygen  than  the  albumins  proper. 

Cartilage. — The  fibres  which  are  found  in  the  matrix  of  fibro-cartilage  and 
elastic  cartilage  are  respectively  composed  of  collagen  and  of  elastin,  just  as  they  are 
in  the  corresponding  connective  tissues. 

According  to  His,  the  chemical  composition  of  human  cartilage  is  as  follows  : 

Costal  cartilage.  Articular  cartilage. 

Water 67.67  73.59 

Solids 32-33  26-4J 

Organic  matter 30-r3  24.S7 

Mineral  salts 2.20  1.54 

In  the  mineral  salts  there  is  about  45  per  cent,  of  sodium  sulphate.  A  somewhat 
smaller  percentage  of  potassium  sulphate,  and  smaller  amounts  of  the  phosphates  of 
sodium,  calcium  and  magnesium,  as  well  as  of  sodium  chloride,  are  present. 

Adipose  Tissue. — The  fats  in  the  animal  body  are  mainly  the  triglycerides  of 
stearic,  palmitic  and  oleic  acid.  There  is  found  in  man  a  comparatively  large  amount 
of  olein.  Small  quantities  of  lecithin,  cholesterin  and  free  fatty  acids  are  also  found 
in  fat  tissue. 


84  HUMAN    ANATOMY. 

BONE   OR    OSSEOUS    TISSUE. 

In  the  higher  vertebrates,  osseous  tissue  forms  the  bony  framework,  or  skeleton, 
which  gives  attachment  and  support  to  the  soft  parts,  affords  protection  to  the  more 
or  less  completely  surrounded  delicate  organs,  supplies  the  passive  levers  for  the 
exercise  of  muscular  action,  insures  stability,  and  maintains  the  definite  form  of  the 
animal. 

In  addition  to  contributing  the  individual  bones  composing  the  principal,  and 
in  man  the  only,  framework,  or  entoskeleton,  osseous  tissue  occurs  in  the  lower  ver- 
tebrates associated  with  the  integument  as  an  exoskeletmi.  Representatives  of  the 
latter  are  seen  in  the  bony  plates  present  in  the  skin  of  certain  ganoid  fishes, 
the  dermal  plates  of  crocodiles,  the  dorsal  and  ventral  shields  of  turtles,  or  the 
dermal  armor  of  the  armadillo.  Osseous  tissue  also  exists  within  various  organs  in 
certain  animals  and  then  constitutes  the  splanchnoskeleton.  Examples  of  the  latter 
are  furnished  by  the  bony  plates  encountered  in  the  sclerotic  coat  of  the  eyes  of 
birds,  in  the  diaphragmatic  muscle  of  the  camel,  in  the  tongue  of  certain  birds,  in 
the  heart  of  ruminants,  in  the  nose,  as  the  snout-bones  of  the  hog,  in  the  respiratory 
organs,  as  the  laryngeal,  tracheal,  and  bronchial  bones  of  birds,  and  in  the  genital 
organs,  as  the  penile  bone  of  carnivorous  and  certain  other  mammals. 

True  osseous  tissue  does  not  occur  outside  the  vertebrates.  Many  invertebrate 
animals  possess  a  skeletal  framework,  usually  external  but  in  some  cases  internal. 
Such  a  framework,  however,  consists  of  calcareous  incrustations,  hardened  excre- 
tions or  concretions  composed  principally  of  calcium  carbonate  and  of  silicious 
structures.  These  earthy  or  mineral  hard  parts  of  invertebrates  are  structureless 
deposits,  so  differing  materially  from  the  bone  tissue  of  the  higher  vertebrates  as 
well  in  structure  as  in  chemical  composition.  Sometimes  a  deposit  of  calcareous 
material  occurs  in  adult  cartilage,  a  process  entirely  distinct  from  the  formation  of 
bone  tissue.  Familiar  examples  of  such  calcification  are  seen  in  the  costal  and  some 
of  the  laryngeal  cartilages. 

Chemical  Composition. — Bone  is  a  dense  form  of  connective  tissue,  the 
matrix  of  which  is  impregnated  with  lime  salts  ;  it  consists,  therefore,  of  two  parts, 
an  animal  and  an  earthy  portion,  the  former  giving  toughness  and  the  latter  hardness 
to  the  osseous  tissue. 

The  animal  or  organic  part  of  bone  may  be  removed  by  calcination,  leaving  the 
inorganic  constituents  undisturbed.  If  a  bone  be  heated  in  a  flame  with  free  access 
of  air,  the  animal  matter  at  first  becomes  charred  and  the  bone  black  ;  continued 
combustion  entirely  removes  the  organic  materials,  the  earthy  portion  alone  remain- 
ing. After  such  treatment,  while  retaining  its  general  form,  the  bone  is  fragile  and 
easily  crushed,  and  has  suffered  a  loss  of  one-third  of  its  weight,  due  to  the  destruc- 
tion and  elimination  of  the  animal  constituents.  The  latter,  evidently,  constitute 
one-third  and  the  mineral  matters  two-thirds  of  the  bone.  The  inorganic  constitu- 
ents include  a  large  amount  of  calcium  phosphate,  much  less  calcium  carbonate,  with 
small  proportions  of  calcium  fluoride  and  chloride,  and  of  the  salts  of  magnesium  and 
sodium. 

The  animal  portion  of  the  bone,  on  the  other  hand,  may  be  separated  from  the 
inorganic  salts  by  the  action  of  dilute  hydrochloric  acid,  which  dissolves  out  the 
earthly  constitutents  ;  after  such  treatment  the  bone,  although  retaining  perfectly 
its  form  and  details,  is  tough  and  flexible,  a  decalcified  rib  or  fibula  being  readily 
tied  into  a  knot.  The  animal  constituents  of  bone  yield  gelatin  upon  prolonged 
boiling  in  water,  therein  resembling  fibrous  connective  tissue. 

The  composition  of  bone,  according  to  Berzelius,  is  as  follows  : 

Organic  matter Gelatin  and  blood-vessels,  33.30 

f  Calcium  phosphate,  51.04 

i   Calcium  carbonate,  11.30 

Inorganic  matter \  Calcium  fluoride,  2.00 

Magnesium  phosphate,  1.16 

Sodium  oxide  and  sodium  chloride,  1.20 


PHYSICAL  PROPERTIES  OF  BONE. 


85 


Fig 


Physical  Properties. — Rauber  has  shown  that  a  five-millimetre  cube  of  com- 
pact bone  of  an  ox  when  calcined  will  resist  pressure  up  to  298  pounds ;  when  decal- 
cified up  to  136  pounds  ;  under  normal  conditions  up  to  852  pounds,  the  pressure 
being  applied  in  the  line  of  the  lamellae. 

It  results  from  its  composition  that  while  bone  is  very  hard  and  resistant  to  press- 
ure, it  is  also  somewhat  flexible,  elastic,  and  capable  of  withstanding  a  tearing  strain. 
It  is  remarkable  that  in  many  substances  the  power  to  resist  a  crushing  strain  is  very 
different  from  that  of  resisting  a  tearing  one.  Thus,  cast  iron  is  more  than  five  times 
as  resistant  to  the  former  strain  as  to  the  latter,  and  wrought  iron  is  nearly  twice  as 
resistant  to  the  latter  as  to  the  former.  Neither  of  these  materials,  therefore,  is  well 
fitted  to  resist  both  strains,  since  a  much  greater  quantity  must  be  used  than  would 
be  needed  were  either  material  to  be  exposed  only  to  the  strain  it  is  best  able  to  with- 
stand. Bone,  however,  has  the  property 
of  resisting  both  strains  with  approximately 
equal  facility,  its  tearing  limit  being  to  its 
crushing  limit  about  as  3  is  to  4.  This  has 
the  advantage  that  strength  need  not  be 
obtained  by  great  increase  of  weight,  con- 
sequently the  plan  of  bone  structure  com- 
bines lightness  and  strength. 

Structure  of  Bone. — On  sawing 
through  a  bone  from  which  the  marrow  and 
other  soft  parts  have  been  removed  by  ma- 
ceration and  boiling,  the  osseous  tissue  is 
seen  (Fig.  113)  to  be  arranged  as  a  pe- 
ripheral zone  of  compact  bone  enclosing  a 
variable  amount  of  spongy  or  cancellated 
bone.  In  the  typical  long  bones,  as  the 
humerus  or  femur,  the  compact  tissue  al- 
most exclusively  forms  the  tubular  shaft 
enclosing  the  large  marrow-cavity,  the  can- 
cellated tissue  occupying  the  expanded 
extremities,  where,  with  the  exception  of 
a  narrow  superficial  stratum  of  compact 
bone,  it  constitutes  the  entire  framework  ; 
the  clefts  between  the  lamellae  of  the  spongy 
bone  are  direct  extensions  of  the  general 
medullary  cavity  and  are  filled  with  mar- 
row-tissue. In  the'  flat  bones  (Fig.  116), 
as  those  of  the  skull,  the  compact  substance 
consists  of  an  outer  and  inner  plate,  or 
tables,  enclosing  between  them  the  cancel- 
lated tissue,  or  diplo'c,  as  this  spongy  bone 
is  often  termed.  Short  and  irregular  bones 
are  made  up  of  an  inner  mass  of  spongy 

bone  covered  by  an  external  shell  of  compact  substance  which  often  presents  local 
thickenings  in  order  to  insure  additional  strength  where  most  needed. 

The  cancellated  bone  consists  of  delicate  bars  and  lamellae  which  unite  to 
form  an  intricate  reticulum  of  osseous  tissue  well  calculated  to  insure  considerable 
strength  without  undue  weight  ;  in  many  positions,  conspicuously  in  the  neck  of  the 
femur  (Fig.  374),  the  more  robust  lamellae  are  disposed  in  a  definite  manner  with 
a  view  of  meeting  the  greatest  strains  of  pressure  and  of  tension. 

Although  composed  of  the  same  structural  elements,  compact  and  spongy  bone 
differ  in  their  histological  details  in  consequence  of  the  secondary  modifications 
which  take  place  during  the  conversion  of  the  spongy  bone,  the  original  form,  into 
the  compact  substance.  To  obtain  the  classic  picture  of  osseous  tissue,  in  order  to 
study  its  general  arrangement  in  the  most  typical  form,  it  is  desirable  to  examine 
thin  ground  sections  of  the  compact  substance  cut  at  right  angles  to  the  axis  of  a 
long  bone  which  has  been  macerated  and  dried,  and  in  which  the  spaces  contain  air. 


Section  of  upper  end  of  humerus,  showing  the 
external  layer  of  compact  bone  surrounding  the  med- 
ullary cavity  below  and  the  spongy  bone  above. 


HUMAN    ANATOMY. 


The  compact  bone  in  such  preparations,  when  examined  under  low  ampli- 
fication (Fig.  114),  is  seen  to  be  composed  of  osseous  layers  arranged  as  three 
chief  groups  :  (a)  the  circumferential  lamella,  which  extend  parallel  to  the  external 
and  internal  surfaces  of  the  compact  bone  ;  (Ji)  the  Haversian  lamellas,  which  are 
disposed  concentrically  and  form  conspicuous  annular  groups,  the  Haversian  systems, 
enclosing  the  Haversian  canals  ;  and  (c)  the  interstitial  or  ground  la?7iell<z,  which 
constitute  the  intervening  more  or  less  irregularly  arranged  bony  layers  filling  up 
the  spaces  between  the  Haversian  systems  and  the  peripheral  strata. 

Fig.  114. 


Haversian  canal 
ded  by  Ha 
lamellae 


Interstitial  lamella 


■•■v*S-^,    y-.-i *■•..■*.,<**  AC  )■■...<  '^r~^Tvt^ 


section  of  compact  bone  (metatarsal)  ;  the  section  has  been  ground  and  dried,  hence  the  lacunas 
filled  with  air.     V  8^. 


'  filled 

Each  Haversian  system  consists  of  the  concentrically  disposed  lamellae  and 
the  centrally  situated  channel,  or  Haversian  canal,  enclosing  the  ramifications  of  the 
medullary  blood-vessels  and  associated  marrow-tissue.  Between  the  annularly 
arranged  lamellas  are  seen  small  spindle-shaped  or  oval  spaces,  the  lacuna,  about 
.02  millimetre  long,  .01  millimetre  wide,  and  .006  millimetre  thick,  from  which  ex- 
tend minute  radiating  channels,  the  canalimli,  establishing  communication  between 
the  adjacent  lacunae  of  the  same  Haversian  system.  The  lacunas  and  the  canaliculi 
constitute  an  intercommunicating  net-work  of  lymph-spaces  similar  to  those  encoun- 


STRUCTURE    OF    BONE. 


87 


tered  in  other  forms  of  dense  connective  tissue.  Since  the  lacunae  are  compressed 
oval  cavities  lying  between  the  lamellae  of  the  osseous  matrix,  when  viewed  in  sec- 
tions which  pass  through  the  layers  at  right  angles  (Fig.  117),  the  lacunae  present 
their  narrower  dimensions,  appearing  thus  in  profile  as  small  lentiform  spaces  ;  seen 
in  sections,  on  the  contrary,  which  pass  parallel  to  the  lamellae  (Fig.  118),  the 
lacunae  are  broader  and  more  circular,  the  spaces  with  the  canaliculi  forming  the 
spider-like  figures  so  conspicuous  in  longitudinal  sections  of  dried  bone. 

The  characteristic  arrangement  of  the  lamellae  of  the  Haversian  systems  is  due 
to  the  secondary  formation  of  the  osseous  tissue  during  the  conversion  of  the  older 
spongy  bone  into  compact  tissue,  the  circumference  of  the  system  corresponding  to 
the  Haversian  space  in  which  the  subsequent  development  of  the  concentric  lamellae 

Fig.  115. 


Longitudinal  section  of  compact  b 


took  place.  It  follows,  from  this  relation,  that  Haversian  systems  exist  only  in  com- 
pact bone,  since  the  necessary  secondary  deposit  does  not  occur  during  the  growth 
of  the  spongy  or  cancellous  tissue. 

The  lamellae  of  osseous  tissue,  when  deprived  of  the  mineral  matters  and  exam- 
ined in  thin  fragments,  often  display  the  ultimate  fibrous  structure  which  they  pos- 
sess, since  they  consist  of  delicate  fibrils  of  fibrous  tissue  embedded  within  a  ground- 
substance  and  associated  into  bundles  which  are  arranged  as  crossing  and  interwoven 
layers.  Within  the  Haversian  lamellae  the  fibrous  bundles  cross  generally  at  right 
angles,  but  in  other  locations  they  are  less  regularly  and  more  acutely  disposed. 

The  perforating  fibres  of  Sharpey  (Fig.  119)  consist  of  bundles  of  fibrous 
tissue  which  penetrate  the  lamellae  in  a  direction  perpendicular  or  oblique  to  their 


88  HUMAN   ANATOMY. 

surface,  and  thus  pin  or  bolt  the  layers  together.  These  fibres  are  especially  numer- 
ous in  the  superficial  lamellae  beneath  the  periosteum,  to  which  membrane  they  owe 
their  formation,  and  with  which  many  seem  to  be  directly  continuous.      They  are 

Fig.  116. 


.^«':""-n";.¥S"-';^-S^5->'-v- 
''^V--is*:,:--.1''.'':'v'":v'"--';--' 


Section  of  frontal  bone,  showing  the  absence  of  Haversian  syste 


Fig.  117. 


readily  found  on  the  surfaces  of  the  lamellae  of  decalcified  bone  which  have  been 
forcibly  separated.  Although  usually  consisting  of  bundles  of  fibrous  tissue,  it  is 
probable  that  in  some  cases  the  perforating  fibres  are  elastic  in  nature.  They  are 
sometimes   imperfectly   calcified   and   leave,   therefore,    on   drying,    tubular   canals, 

which  pierce  the  lamella  from  the  ex- 
terior of  the  bone.  Since  the  perfo- 
rating fibres  are  associated  genetically 
with  the  periosteum,  they  are  never 
found  in  the  secondary  lamellae  consti- 
tuting the  Haversian  systems. 

The  Haversian  canals  are  con- 
tinuations of  the  medullary  cavity  and 
serve  the  important   purpose  of   con- 
veying   the    blood-vessels  within    the 
compact  substance  ;  from  these  vessels 
the  nutritive  fluids  pass  into  the  peri- 
vascular   lymph-spaces    between    the 
walls  of  the  canal  and  the  blood-ves- 
sels and  thence,  by  way  of  the  cana- 
liculi,  which  open  into  these  lymph- 
spaces,  into  the  adjacent  lacunae,  and 
so  on  into  the  surrounding  portions  of 
the  compact  substance,  the  nutrition  of  which  is  thus  maintained.      Although  the 
average  size  of  the  canals  is  about  .05  millimetre,  those  next  the  medullary  cavity 
are  larger,  some  measuring  .  1  millimetre  or  more  in  diameter,  and  contain,  in  addi- 


Lacuna 
profili 


Portion  of  adjacent  Ha 


W/d/ 


1  systems  cut  transversely. 


THE    BONE-CELLS. 


Lacuna  and  canalii 


tion  to  the  blood-vessels,  an  extension  of  the  marrow-tissue.  The  individual  chan- 
nels are  short,  and  communicate  by  oblique  branches  with  adjacent  canals  (Fig. 
115).  The  Haversian  canals  indirectly  communicate  with  the  external  surface  of 
the  bone  by  means  of  the  channels,  or  Volkmami  s  canals,  within  the  circumfer- 
ential lamellae,  which  open  by  minute  orifices  and  receive  vascular  twigs  from  the 
periosteal  blood-vessels  (Fig.  122);  the  latter  are  thus  brought  into  free  anasto- 
mosis with  the  branches  derived  from  the  medullary  vessels,  the  two  constituting  a 
freely  communicating  vascular  net-work  throughout  the  compact  substance. 

The  Bone-Cells.— The  details  of 
osseous  tissue  thus  far  considered  per- 
tain to  the  structure  of  the  passive  in- 
tercellular constituents  of  a  dense  con- 
nective tissue  ;  in  addition  to  these,  as 
in  other  forms  of  connective  substances, 
the  more  active  elements  are  the  con- 
nective-tissue cells,  here  known  as  the 
bo7ie-cells.  As  already  pointed  out,  the 
lacuna?  and  the  canaliculi  represent  in- 
tercommunicating lymph-spaces,  similar 
to  those  encountered  in  the  cornea  or 
other  dense  connective  tissue  ;  as  in  the 
latter  so  also  in  the  osseous  tissue,  the 
cellular  elements  occupy  the  lymph- 
spaces,  the  bone-cells  lying  within  the  lacunae.  Since  the  classic  pictures  of  bone 
are  derived  from  ground  sections  of  dried  tissue,  in  such  preparations  the  deli- 
cate bone-cells  have  shrunken  and  disappeared,  and  the  lacunae  contain,  at  best, 
only  the  indistinguishable  remains  of  the  cells  mingled  with  dtbris  produced  during 
the  preparation  of  the  section  ;  the  lacunae  and  the  canaliculi  in  dried  sections 
are  filled  with  air,  by  reason  of  which  condition  they  appear  as  the  familiar  dark, 

sharply  defined,  conspicuous  spider- 
Fig.  119.  like  figures. 

In  order  to  study  the  bone- 
cells,  the  tissue  after  fixation  is  de- 
calcified and  stained,  and  mounted 
in  an  approved  preserving  medium  ; 
in  consequence  of  such  treatment 
the  air  is  displaced  from  the  spaces 
within  the  bone,  which  now  appear 
faintly  outlined,  the  delicate  ramifi- 
cations of  the  canaliculi  in  places 
being  almost  invisible.  The  bone- 
cells,  after  being  stained  in  such 
decalcified  preparations,  appear  as 
small  lenticular  or  stellate  bodies 
within  the  lacunae  (Fig.  121),  which 
they  almost  entirely  fill.  Each  cell- 
body  consists  of  granular  cytoplasm 
from  which  delicate  processes  ex- 
tend for  a  variable  distance  into  the 
canaliculi,  in  favorable  localities  the 
protoplasmic  processes  sent  out  by  adjacent  bone-cells  sometimes  meeting.  The 
deeply  staining  nucleus  appears  as  a  brilliant  point  within  the  stellate  cell. 

The  Periosteum. — The  external  surface  of  bones  is  closely  invested,  except 
where  covered  with  cartilage,  with  a  fibrous  membrane,  the  periosteum,  a  structure 
of  great  importance  during  development  and  growth,  and  later  for  the  nutrition 
and  protection  of  the  osseous  tissue.  During  childhood  an  end  of  the  immature 
bone  may  be  broken  off  and  yet  held  in  place  by  the  periosteum.  The  adult  peri- 
osteum consists  of  two  layers,  an  outer  fibrous  and  an  inner  fibro-elastic ;  when 
covering  young  bones,  however,  in  which  growth  is  actively  progressing,  the  peri- 


Semi-diagrammatic  view  of  perforating  fibres  of  Sharpey ;  the 
lamellae  of  decalcified  bone  have  been  partially  separated. 


9o  HUMAN    ANATOMY. 

osteum  contains  an  additional  stratum,  the  osteogenetic  layer,  which  lies  closely  asso- 
ciated with  the  exterior  of  the  bone.  After  growth  has  ceased,  the  osteogenetic 
layer  becomes  reduced  to  an  inconspicuous  stratum  included  as  part  of  the  fibro- 
elastic  constituent  of  the  periosteum. 

The  fibrous  layer  is  composed  of  closely  placed  bundles  of  fibrous  connective 
tissue,  and  serves  to  support  larger  blood-vessels  which  break  up  within  the  deeper 
parts  of  the  periosteum  into  the  minute  twigs  entering  the  canals  opening  onto  the 
surface  of  the  bone. 

Fig.  i  20. 


Sharpey'* 


Oblique  section  of  decalcified  tibia,  showing  fibrous  character  of  lamella;  and  groups  of  Sharpey's  fibres.     X  420. 

The  fibi'o-elastic  layer  consists  of  a  rich  felt-work  of  elastic  fibres,  often  arranged 
as  several  distinct  strata  ;  the  elastic  tissue  is  separated  from  the  surface  of  the  bone 
by  a  layer  of  fibrous  tissue  comparatively  rich  in  flat,  plate-like  connective-tissue 
cells,  the  remains  of  the  elements  of  the  osteogenetic  layer.  The  inner  surface  of 
the  periosteum  is  intimately  attached  to  the  osseous  tissue  by  means  of  delicate 
processes  of  connective  tissue  which  accompany  the  blood-vessels  into  the  nutrient 
canals  ;  this  relation  persists  from  the  continuity  of  the  formative  tissue  of  the  young 

periosteum  with   the    early  marrow-tissue. 
Fig.  i2i.  Between  the  fibrous  bundles  next  the  bone 

numerous    cleft-like    lymph-spaces    exist ; 
these  are  imperfectly  lined  by  the  endothe- 
'.  *•  ,  <-  lioid  connective-tissue  cells  and  communi- 

cate with   the    lymph-channels  within   the 
'.;%•-  ,  bone. 

^kij-  '.  The    osteogenetic    layer,     conspicuous 

■'■l.WmJ&'v}  ^^&is'  ■■'■         during  the  development  and  growth  of  the 

";•"•'*  f*"-"'"...'  *$&;■£%         ,  osseous  tissue,  consists  of  delicate  bundles 

.  >  ; :  *'  '■•■*}/££}'        "'.       of    fibrous    tissue    and    large    numbers    of 

'-.  i- !:'J''       tip,       connective-tissue    cells    of    an     embryonal 

-,v.;  ...       .'.       type.      Those   next  the  growing  bone  as- 

~  ■...-'■•         sume  a  low,  irregular  columnar  form,  and 

are  disposed  in  rows  upon  the  surface  of 

Bone-ceils  lying  within  the  lacuna;,    x  700.  the  developing  osseous  tissue  ;  since  these 

cells  are  concerned  in  the  production  of  the 
latter,  they  are  appropriately  termed  osteoblasts.  Later  some  of  them  become  sur- 
rounded by  the  bony  matrix,  and  are  thus  transformed  into  bone-cells.  The  osteo- 
genetic layer  is  rich  in  blood-vessels  which,  as  the  bone  is  formed,  are  continued  into 
the  primary  marrow-cavities. 

The  Marrow. — The  spaces  in  the  interior  of  bones,  whether  the  large 
medullary  cavities  surrounded  by  the  compact  substance  forming  the  shaft  of  the 
long  bones  or  the  irregular  interstices  between  the  trabecular  composing  the  cancel- 


THE    RED    BONE-MARROW. 


9i 


lated  tissue,  are  filled  with  bone-marrow.  The  latter  also  extends  within  the  larger 
Haversian  canals. 

Although  originally  only  of  one  variety  within  the  bones  of  the  early  skeleton, 
the  marrow  in  the  adult  consists  of  two  kinds,  the  yellow  and  the  red.  Thus,  within 
the  shaft  of  the  long  bones  it  consists,  of  a  light  yellowish  tissue,  presenting  the  char- 
acteristics of  ordinary  adipose  tissue,  while  within  the  spaces  of  the  cancellated  tissue 
at  the  ends  of  the  same  bones  the  marrow  appears  of  a  dull  red  color.  In  addition 
to  the  ends  of  the  long  bones,  the  localities  in  which  red  marrow  especially  occurs 
are  the  bodies  of  the  vertebrae,  the  ribs,  the  sternum,  the  diploe  of  the  cranium,  and 
the  short  bones. 

Red  Marrow. — The  ingrowth  of  the  periosteal  tissue  and  blood-vessels  con- 
stitutes the  primary  marrow  within  the  embryonal  skeleton  ;  from  this  tissue  the  red 
marrow  filling  the  young  bones  is  directly  derived.      The  red  marrow  is,  therefore, 


yr\\ 


I   Mi  itn\l 


-  Dense  fibrous  laye 


1' 


fi 


Periosteal  blood-  .'ft. 

vessel  passing  into  '■ 


*/.'■: 


■    if:-/*  f  -'r  ' 


s?# 


M 

-+7W- Marrow-tissue  continu- 
\\fy.       ous  with  periosteum 


Bone-cell  within 1 


-Remains  of  osteogenetic 


Y 


Section  of  young  periosteum  and  subjacent  bone.     X  275. 


the  typical  and  first  formed  variety  within  the  foetus  and  the  young  animal  ;  subse- 
quently, that  situated  within  the  shaft  of  the  long  bones  becomes  converted  into 
yellow  marrow  by  the  replacement  of  the  majority  of  the  marrow  elements  by  fat- 
cells. 

The  red  marrow  (Fig.  123),  when  examined  in  section  after  fixation  and  staining, 
presents  a  delicate  reticulum  of  connective  tissue  which  supports  the  numerous 
medullary  blood-vessels  and  the  cellular  elements.  Next  the  bone  the  fibrous  tissue 
forms  a  thin  membrane,  the  e?idosteum,  lining  the  medullary  cavity  and  the  larger 
Haversian  canals  into  which  the  marrow  extends.  This  membrane  is  highly  vascu- 
lar, its  vessels  joining  those  within  the  osseous  canals  on  the  one  side  and  those  of 
the  marrow  on  the  other. 

The  delicate  fibrous  reticulum,  in  addition  to  the  thin-walled  blood-channels 
which  it  supports,  contains  within  its  meshes  the  several  varieties  of  elements  char- 


92 


HUMAN    ANATOMY. 


acteristic  of  the  red  marrow  ;  these  are  :  (i)  the  marrow-cells,  (2)  the  eosinophile 
cells,  (3)  the.  giant  cells,  and  (4)  the.  nucleated  red  blood-cells. 

The  marrow-cells,  or  myelocytes,  resemble  the  large  lymphocytes  of  the 
blood,  but  may  differ  from  the  latter  in  their  slightly  larger  size  and  in  the  possession 
of  a  relatively  large  round  or  oval  nucleus  which  contains  comparatively  little 
chromatin;  the  presence  of  neutrophile  granules  within  the  cytoplasm  of  the  marrow- 
cells  affords  an  additional  differential  characteristic  when  compared  with  the  large 
lymphocytes  in  which  these  granules  are  absent. 

The  eosinophile  cells  occur  in  considerable  numbers  within  the  red  marrow, 
and  appear  in  varying  stages  of  growth,  as  evidenced  by  their  round  mononuclear, 
the  indented  transitional  and  segmented  polymorphonuclear  condition  ;  the  cells  con- 
taining the  latter  form  of  nucleus  are  most  abundant  and  represent,  probably,  the 
mature  elements. 

The  giant  cells,  or  myeloplaxes,  are  huge  elements  of  irregular  oval  form,  and 
contain  simple   or  polymorphous  nuclei.      They  represent  specialized  myelocytes, 

Fig.  123. 


-^^-, 


^M:, 


<§>. 


Marrow-cells 


Young  red  blood-cell 


^/^J>/9*?>  <^'%%!R  ■  Giant  , 


Blood-vessel-"""^     / 


Connective-tissue  reticulu 


Section  of  red  marrow  from  epiphysis  of  young  femur.    X  300. 


and  during  the  processes  resulting  in  the  removal  of  osseous  tissue  they  are  the 
osteoclasts  which  are  actively  engaged  in  effecting  the  absorption  of  the  bony 
matrix.  Ordinarily  the  giant  cells  occupy  the  central  portions  of  the  marrow  ; 
when,  however,  they  enter  upon  the  role  of  bone-destroyers,  they  lie  on  the  sur- 
face of  the  osseous  trabeculae  within  the  depressions  known  as  Hows  hip' s  lacuna 
(Fig.  128). 

The  nucleated  red  blood-cells  within  the  red  marrow  are  concerned  in  the 
important  function  of  renewing  the  colored  cells  of  the  blood,  the  red  marrow  being 
the  chief  seat  in  which  this  process  takes  place  after  birth  ;  hence  the  red  marrow  is 
classed  as  a  blood-forming  organ.  The  nucleated  red  blood-cells  exist  within  the 
marrow  in  two  forms,  an  older  and  a  younger.  The  genetically  older  cells,  the 
eiythroblasts,  are  the  descendants  of  the  embryonal  nucleated  blood- cells  on  the  one 
hand  and  the  immediate  parents  of  the  younger  blood-elements  on  the  other.  The 
erythroblasts  possess  relatively  large  nuclei,  with  chromatin  reticulum  and  cytoplasm 
tinged  with  haemoglobin  ;  they  are  frequently  observed  during  mitosis,  since  they  give 
rise  to  the  second  generation  of  nucleated  red  blood-cells.      The  latter,  the  normo- 


THE   YELLOW   BONE-MARROW.  93 

blasts,  are  directly  converted  into  the  mature,  non-nucleated  red  blood-disks  on  the 
disappearance  of  their  nucleus.  In  addition  to  a  larger  amount  of  haemoglobin  in  their 
cytoplasm,  the  normoblasts  differ  from  the  erythroblasts  in  the  possession  of  a  deeply 
staining  nucleus,  in  which  the  chromatin  no  longer  appears  as  a  reticulum. 

It  is  usual  to  find  isolated  groups  of  fat-cells  distributed  within  the  red  marrow, 
although  the  amount  of  adipose  tissue  is  very  meagre  in  localities  farthest  removed 
from  the  medulla  of  the  long  bones.  The  varieties  of  leucocytes  usually  seen  in  the 
blood  are  also  encountered  within  the  red  marrow  in  consequence  of  the  intimate 
relations  between  the  latter  tissue  and  the  blood-stream  conveyed  by  the  medullary 
capillaries. 

Yellow  Marrow. — Since  the  appearance  of  the  yellow  marrow  is  due  to  the 
preponderating  accumulation  of  fat-cells  which  have  replaced  the  typical  elements 
of  the  marrow  contained  within  the  shaft  of  certain  bones,  the  formation  of  this 
variety  is  secondary  and  must  be  regarded  as  a  regression. 

Examined  in  section,  yellow  marrow  resembles  ordinary  adipose  tissue,  since 
it  consists  chiefly  of  the  large  oval  fat-cells  supported  by  a  delicate  reticulum  of 
connective  tissue.  In  localities  in  which  the  latter  exists  in  considerable  quantity, 
numerous  lymphoid  cells  represent  the  remaining  elements  of  the  originally  typical 
marrow-tissue.  After  prolonged  fasting  the  yellow  marrow  loses  much  of  its  oily 
material  and  becomes  converted  into  a  gelatinous  substance  containing  compara- 
tively few  fat-cells  ;  upon  the  re-establishment  of  normal  nutrition  this  tissue  may 
again  assume  the  usual  appearance  of  yellow  marrow. 

Blood-Vessels. — The  generous  blood-supply  of  bones  is  arranged  as  two  sets 
of  vessels,  the  periosteal  and  the  medullary.  The  former  constitutes  an  external 
n'et-work  within  the  periosteum,  from  which,  on  the  one  hand,  minute  twigs  enter 
the  subjacent  compact  substance  through  channels  (  Volkma?i?i'  s  canals')  communi- 
cating with  the  Haversian  canals,  within  which  the}r  anastomose  with  the  branches 
derived  from  the  medullary  system  ;  additional  vessels,  on  the  other  hand,  pass  to 
the  cancellated  tissue  occupying  the  ends  of  the  long  bones. 

The  medullary  artery  is  often,  as  in  the  case  of  the  long  bones,  a  vessel  of  con- 
siderable size,  which,  accompanied  by  companion  veins,  traverses  the  compact  sub- 
stance through  the  obliquely  directed  medullary  canal  to  gain  the  central  part  of  the 
marrow.  On  reaching  this  position  the  medullary  artery  usually  divides  into  ascend- 
ing and  descending  branches,  from  which  radiating  twigs  pass  towards  the  periphery. 
The  latter  terminate  in  relatively  narrow  arterial  capillaries,  which,  in  turn,  expand 
somewhat  abruptly  into  the  larger  venous  capillaries.  Such  arrangement  results  in 
diminished  rapidity  of  the  blood-stream,  the  blood  slowly  passing  through  the  net- 
work formed  by  the  venous  capillaries.  The  latter  vessels,  within  the  red  marrow, 
possess  thin  walls  and  an  imperfect  endothelial  lining  in  consequence  of  which  the 
blood  comes  into  close  relation  with  the  elements  of  the  medullary  tissue.  During 
its  sluggish  course  within  the  blood-spaces  of  the  red  marrow,  the  blood  takes  up  the 
newly  formed  red  cells,  which  thus  gain  entrance  into  the  circulation  to  replace  the 
effete  corpuscles  which  are  continually  undergoing  destruction  within  the  spleen.  It 
is  probable  that  leucocytes  also  originate  in  the  bone-marrow. 

After  thus  coming  into  intimate  relations  with  the  marrow-tissue,  the  blood  is 
collected  by  capillaries  which  form  small  veins.  In  addition  to  the  companion  veins 
accompanying  the  nutrient  artery  along  the  medullary  canal,  in  many  instances  the 
larger  veins  pursue  a  course  independent  of  the  arteries  and  emerge  from  the  can- 
cellous tissue  by  means  of  the  canals  piercing  the  compact  substance  at  the  ends  of 
the  bones.  Although  destitute  of  valves  within  the  medulla,  the  veins  possess  an 
unusual  number  of  such  folds  immediately  after  escaping  from  the  bone. 

Lymphatics. — The  definite  lymphatic  channels  of  the  bones  are  principally 
associated  with  the  blood-vessels  of  the  periosteum  and  the  marrow  as  perivascular 
channels,  although  it  is  probable  that  lymphatic  spaces  exist  within  the  deeper  layers 
of  the  periosteum,  in  close  relation  to  the  osseous  tissue.  The  perivascular  lym- 
phatics follow  the  blood-vessels  into  the  Haversian  canals,  where,  as  well  as  on  other 
surfaces  upon  which  the  canaliculi  open,  the  system  of  intercommunicating  juice- 
channels  represented  by  the  lacunae  and  the  canaliculi  is  closely  related  with  the 
lymphatic  trunks. 


94 


HUMAN   ANATOMY. 


Nerves. — The  periosteum  contains  a  considerable  number  of  nerves,  the  ma- 
jority of  which,  however,  are  destined  for  the  supply  of  the  underlying  osseous 
tissue,  since  those  distributed  to  the  fibrous  envelope  of  the  bone  are  few.  The 
periosteal  nerves  follow  the  larger  blood-vessels,  in  the  walls  of  which  they  chiefly 
terminate.  Medullary  nerves  accompany  the  corresponding  blood-vessels  through 
the  medullary  canal,  and  within  the  marrow  break  up  into  fibrillse  to  be,  probably, 
distributed  to  the  walls  of  the  vascular  branches  along  which  they  lie.  Regarding 
the  ultimate  endings  and  arrangement  of  the  sensory  fibres  little  is  known  ;  in  view 
of  the  low  degree  of  sensibility  possessed  by  healthy  bones  and  their  periosteum, 
the  number  of  such  nerves  present  in  osseous  structures  must  be  very  small. 


Fig.  124. 


DEVELOPMENT   OF   BONE. 

The  bones  composing  the  human  skeleton,  with  few  exceptions,  are  preceded 
by  masses  of  embryonal  cartilage,  which  indicate,  in  a  general  way,  the  forms  and 
relations  of  the  subsequent  osseous  segments,  although  many  details  of  the  model- 
ling seen  in  the  mature  bones  appear  only  after  completed  development  and  the  pro- 
longed exercise  of  the  powerful  modifying  influences  exerted  by  the  action  of  the 
attached  muscles.  Since  the  primary  formation  of  such  bones  takes  place  within 
the  cartilage,  the  process  is  appropriately  termed  endochondral  developinent. 

Certain  other  bones,  notably  those  forming  the  vault  of  the  skull  and  almost  all 
those  of  the  face,  are  not  preceded  by  cartilage,  but,  on 
the  contrary,  are  produced  within  sheets  of  connective  tis- 
sue ;  such  bones  are  said,  therefore,  to  arise  by  intra- 
menibranous  development.  It  will  be  seen,  however,  that 
the  greater  part  of  the  bone  formed  by  endochondral  de- 
velopment undergoes  absorption,  the  spongy  substance 
within  the  ends  of  the  long  and  the  bodies  of  the  irregu- 
lar bones  representing  the  persistent  contribution  of  this 
process  of  bone-production.  Even  in  those  cases  in  which 
the  intracartilaginous  mode  is  conspicuous,  as  in  the  de- 
velopment of  the  humerus,  femur,  and  other  long  bones, 
the  important  parts  consisting  of  compact  substance  are  the 
product  of  the  periosteal  connective  tissue,  and  hence  ge- 
netically resemble  the  intramembranous  group.  Although 
both  methods  of  bone-formation  in  many  instances  proceed 
coincidently  and  are  closely  related,  as  a  matter  of  con- 
venience they  may  be  described  as  independent  processes. 
Endochondral  Bone  Development. — The  pri- 
mary cartilage,  formed  by  the  proliferation  and  condensa- 
tion of  the  elements  of  the  young  mesoblastic  tissue,  grad- 
ually assumes  the  characteristics  of  embryonal  cartilage, 
which  by  the  end  of  the  second  month  of  intra-uterine  life 
maps  out  the  principal  segments  of  the  fcetal  cartilaginous 
skeleton.  These  segments  are  invested  by  an  immature 
form  of  perichondrium,  or  primary  periosteum,  from  which 
proceed  the  elements  actively  engaged  in  the  production 
of  the  osseous  tissue.  The  primary  periosteum  consists  of  a 
compact  outer  fdrous  and  a  looser  inner  osteogenetic  layer; 
the  latter  is  rich  in  cells  and  delicate  intercellular  fibres. 
The  initial  changes  appear  within  the  cartilage  at  points  known  as  centres  of 
ossification,  which  in  the  long  bones  are  situated  about  the  middle  of  the  future  shaft. 
These  early  changes  (Fig.  125)  involve  both  cells  and  matrix,  which  exhibit  con- 
spicuous increase  in  size  and  amount  respectively.  As  a  further  consequence  of  this 
activity,  the  cartilage-cells  become  larger  and  more  vesicular,  and  encroach  upon  the 
intervening  matrix,  in  which  deposition  of  lime  salts  now  takes  place,  as  evidenced 
by  the  gritty  resistance  offered  to  the  knife  when  carried  through  such  ossific  centres. 
On  acquiring  their  maximum  growth  the  cartilage-cells  soon  exhibit  indications  of 
impaired  vitality,   as  suggested  by   their  shrinking   protoplasm  and   degenerating 


Clarified  human  fcetus  of  about 
three  and  one-half  months,  show- 
ing the  partially  ossified  skeleton. 
Two-thirds  natural  size. 


DEVELOPMENT    OF    BONE. 


95 


nuclei.  The  enlarged  spaces  enclosing  these  cells  are  sometimes  designated  as  the 
primary  areoles. 

Coincidently  with  these  intracartilaginous  changes,  a  thin  peripheral  layer  of 
bone  has  been  formed  beneath  the  young  periosteum  ;  from  the  latter  bud-like 
processes  of  the  osteogenetic  layer  grow  inward  from  the  periphery  and  invade 
the  embryonal  cartilage,  by  absorption  of  the  cartilage-matrix  gaining  the  centre 
of  ossification  and  there  effecting  a  destruction  of  the  less  resistant  cells  and  inter- 
vening matrix.  In  consequence  of  the  penetration  of  the  periosteal  processes  and 
the  accompanying  absorption  of  the  cartilage,  a  space,  the  primary  marrow-cavity, 
now  occupies  the  centre  of  ossification  and  contains  the  direct  continuation  of  the 
osteogenetic  layer.  This  tissue,  the  primary  marrow,  which  has  thus  gained  access 
to  the  interior  of  the  cartilage,  contributes  the  cellular  elements  upon  which  a  double 
r61e  devolves, — to  produce  osseous  tissue  and  to  remove  the  embryonal  cartilage. 

The  cartilage-matrix  closing  the 


rf% 


W 


Fig.  125. 


-Embryonal  cartilage 


-Cartilage-cells  be- 
and  regrouped 


Enlarged  cartilage- 
cells  at  centre  of 
ossification 


enlarged  cell-spaces  next  the  pri- 
mary marrow-cavity  suffers  absorp- 
tion, whereby  the  cartilage-cells  are 
liberated  and  the  opened  spaces  are 
converted  into  the  secondary  areola, 
and  directly  communicate  with  the 
growing  medullary  cavity.  After 
the  establishment  of  this  communi- 
cation, the  cartilage- cells  escape  from 
their  former  homes  and  undergo  dis- 
integration, taking  no  part  in  the 
direct  production  of  the  osseous  tissue. 

Beyond  the  immediate  limits  of 
the  primary  marrow-cavity  the  car- 
tilage-cells, in  turn,  repeat  the  pre- 
paratory stages  of  increased  size  and 
impaired  vitality  already  described, 
but  in  addition  they  often  exhibit  a 
conspicuous  rearrangement,  where- 
by they  form  columnar  groups  sepa- 
rated by  intervening  tracts  of  calci- 
fied matrix  (Figs.  126,  129).  This 
characteristic  belt,  or  zone  of  calci- 
fication, surrounds  the  medullary 
cavity  and  marks  the  area  in  which 
the  destruction  of  the  cartilage  ele- 
ments is  progressing  with  greatest 
energy.  In  consequence  of  the 
columnar  grouping  of  the  enlarged 
cartilage-cells  and  the  intervening 
septa  of  calcified  matrix,  an  arrange- 
ment particularly  well  marked  in  the  ends  of  the  diaphysis  of  the  long  bones,  a  less 
and  a  more  resistant  portion  of  the  cartilage  are  offered  to  the  attacks  of  the  marrow- 
tissue  by  the  cell-  and  matrix-columns  respectively  ;  as  a  result  of  this  difference, 
the  cells  and  the  immediately  surrounding  partitions  are  first  absorbed,  while  the 
intervening  trabecular  of  calcified  cartilage-matrix  remain  for  a  time  as  irregular  and 
indented  processes,  often  deeply  tinted  in  sections  stained  with  haematoxylin,  which 
extend  beyond  the  last  cartilage-cells  into  the  medullary  cavity.  These  trabecular 
of  calcified  cartilage-matrix  serve  as  supports  for  the  marrow-cells  assigned  to  pro- 
duce the  true  bone,  since  these  elements,  the  osteoblasts,  become  arranged  along 
these  trabecular,  upon  which,  through  the  influence  of  the  cells,  the  osseous  tissue  is 
formed. 

Simultaneously  with  the  destructive  phase  attending  the  absorption  of  the  car- 
tilage, the  constructive  process  is  instituted  by  the  osteoblasts  by  which  the  bone- 
tissue  is  formed.      These  specialized   connective-tissue   elements,   resting  upon  the 


Section  of  tarsal  be 


96 


HUMAN    ANATOMY. 


irregular  trabecule  of  the  calcified  cartilage,  bring  about,  through  the  influence  of 
their  protoplasm,  the  deposition  of  a  layer  of  bone-matrix  upon  the  surface  of  the 


Young  periosteum 


Cartilage- eel  Is  becoming  < 
larged  and  grouped 


■>w 


III 


Ill 

Ci-7 


Zone  of  calcification  - 


Central   spongy  bone  en- 
closing remains  of  carti- 


Longitudinal  section  of  metatarsal  bone  of  fcetal  sheep,  showing  stages  of  endochondral  bone-development.    X  40. 

trabecule,  which  thus  becomes  enclosed  within  the  new  bone.  After  the  latter  has 
attained  a  thickness  of  at  least  the  diameter  of  the  osteoblasts,  some  of  the  cells  in 
closest  apposition  are  gradually  surrounded  by  the  osseous  matrix  (Fig.  127),  until, 


ENDOCHONDRAL    BONE. 


97 


Osteoblast  ■ 
becoming 
a  bone-cell 


Osteoblasts  <^ 


finally,  they  lie  isolated  within  the  newly  formed  bone  as  its  cells  ;  the  bone-cells  are 
therefore  imprisoned  osteoblasts,  which,  in  turn,  are  specialized  connective-tissue 
elements.  The  bone-cells  occupy  minute  lenticular  spaces,  the  piimary  lacuna,  at 
this  immature  stage  the  canaliculi  being  still  unformed.  The  early  bone-matrix  is  at 
first  soft,  since  the  deposition  of  the  calcareous  materials  takes  place  subsequently. 

The  increase  in  the  thickness  of  the  new  bone  is  attended  by  the  gradual  disap- 
pearance of  the  enclosed  remains  of  the  calcified  cartilage,  the  last  traces  of  which, 
however,   can   be  seen  for  some   considerable  time  as 

irregular  patches  within   the   osseous   trabecular  (Fig.  Fig.  127. 

131),  somewhat  removed  from  the  zone  of  calcification. 
The   cartilage  and   the   bone   of    the   trabecular   stand, 

therefore,  in  inverse  relations,  since  the  stratum  of  bone  .^^  |  : 

is  thinnest  where  the    cartilage  is  thickest,   and,   con-  '       ,;'  < 

versely,  the  calcified  matrix  disappears  within  the  robust  "fe^f^;';'      -- 

bony  trabecular.  A  number  of  the  latter,  together  with 
the  enclosed  remains  of  the  calcified  cartilage,  soon 
undergo  absorption,  with  a  corresponding  enlargement 
of  the  intervening  marrow-spaces.  The  remaining  tra- 
becular increase  by  the  addition  of  new  lamellar  on  the 
surface  covered  by  the  osteoblasts,  and  at  some  distance 
from  the  zone  of  calcification  form  a  trabecular  reticulum, 
the  primary  central  spongy  bone.  In  the  case  of  the 
irregular  bones,  the  central  spongy  bone  is  represented 
by  the  cancellated  substance  forming  the  internal  frame- 
work ;  in  the  long  bones,  on  the  contrary,  the  primary 

cancellated  tissue  undergoes  further  absorption  within  the  middle  of  the  shaft  simul- 
taneously with  its  continued  development  at  the  ends  of  the  diaphysis  from  the  car- 
tilage. As  the  result  of  this  absorption,  a  large  space — the  central  inarrow- cavity — is 
formed  (Fig.  129),  the  growth  of  which  keeps  pace  with  the  general  expansion  of 
the  bone. 

The  absorption  of  the  young  osseous  tissue  to  which  reference  has  been  made 
is  effected  through  the  agency  of  large  polymorphonucleated  elements,   the  osteo- 
clasts.    These  are  specialized  marrow- 
F|G-  I28-  cells  whose  particular  role  is  the  break- 

c^M-  ing  up  and  absorption  of  bone-matrix. 

\£m  They   are  relatively   very  large,   their 

H|     '.'.  -       .    •  irregularly  oval  bodies  measuring  from 

;>iJ    ■#  v,,  -050  to  .100  millimetre  in  length  and 

-:jllt: ..-'■■-  from  .030  to  .040  millimetre  in  breadth. 

\    \<         _,     ,    .       The  osteoclasts  (Fig.    128),  singly  or 

i  \.  'M.  ■   '  ^^Osteoclast  .  -       &  J  \  * 

W  ^-^"^  ln  groups,  he  in  close   relation  to  the 

surface  of  the  bone  which  they  are  at- 
|  ji"  Bone-ceil  tacking  within  depressions,  or  How- 
%     4fe     lacuna  ship' s  lacuncs,  produced  in  consequence 

)      ':  of   the  erosion   and   absorption  of  the 

.y-.^'  osseous     matrix    which     they    effect. 

M'  When  not  engaged  in  the  destruction  of 

bone,  these  cells  occupy  the  more  central 
portions  of  the  marrow-tissue,  where, 
in  the  later  stages,  they  are  probably 
identical  with  the  myeloplaxes  or  giant 
cells  encountered  in  the  red  marrow. 
The  only  part  of  the  central  spongy  bone  which  persists  after  the  completed 
development  and  growth  of  the  long  bones  is  that  constituting  the  cancellated  tissue 
occupying  their  ends.  It  will  be  seen,  therefore,  in  many' cases,  that  the  product  of 
the  endochondral  bone-formation,  the  primary  central  osseous  tissue,  is  to  a  large 
extent  absorbed,  and  constitutes  only  a  small  part  of  the  mature  skeleton.  The 
early  marrow-cavity,  as  well  as  all  its  ramifications  between  the  trabecular,  is  filled 
with  the  young  marrow-tissue  ;   the  latter  gives  rise  to  the  permanent  red  marrow 


.-0^ 


,m 


ndergoing  absorp- 


HUMAN    ANATOMY. 


Fig.  129. 


in  the  limited  situations  where  the  central  spongy  bone  persists,  as  in  the  vertebrae, 
the  ribs,  the  sternum,  and  the  ends  of  the  long  bones. 

The  important  fact  may  be  here  emphasized  that  the  process  sometimes  spoken 
of  as  the  "  ossification  of  cartilage"  is  really  a  substitution  of  osseous  tissue  for  car- 
tilage, and  that  even  in  the  endochondral  mode  of  formation  cartilage  is  never 
directly  converted  into  bone. 

The  ossificatioji  of  the  epiphyses  (Fig.  130),  which  in  the  majority  of  cases 
does  not  begin  until  some  time  after  birth,  the  cartilage  capping  the  diaphysis  mean- 
while retaining  its  embryonal  character,  repeats  in  the  essential  features  the  details 
already  described  in  connection  with  endochondral  bone-formation  of  the  shaft. 
After  the  establishment  of  the  primary  marrow-cavity  and  the  surrounding  spongy 
bone,  ossification  extends  in  two  directions, — towards  the  periphery  and  towards  the 
adjacent  end  of  the  diaphysis.  As  this  process  continues,  the  layer  of  cartilage  in- 
terposed between  the  central  spongy  bone  and  the  free  surface  on  the  one  hand, 

and  between  the  central  bone  of  the  epiphysis 
and  the  diaphysis  on  the  other,  is  gradually 
reduced  until  in  places  it  entirely  disappears. 
Over  the  areas  which  correspond  to  the  later 
joint-surfaces  the  cartilage  persists  and  be- 
comes the  articular  cartilage  covering  the 
free  ends  of  the  bone.  With  the  final  ab- 
sorption of  the  plates  separating  the  epiphyses 
from  the  shaft  the  osseous  tissue  of  the  seg- 
ments becomes  continuous,  "bony  union" 
being  thus  accomplished. 

Intxamembranous  Bone-Develop- 
ment.— The  foregoing  consideration  of  the 
formation  of  bone  within  cartilage  renders  it 
evident  that  the  true  osteogenetic  elements 
are  contributed  by  the  periosteum  when  the 
latter  membrane  sends  its  processes  into  the 
ossific  centre  ;  the  distinction,  therefore,  be- 
tween endochondral  and  membranous  bone 
is  one  of  situation  rather  than  of  inherent 
difference,  since  in  both  the  active  agents  in 
the  production  of  the  osseous  tissue  are  the 
osteoblasts,  and  in  essential  features  the  pro- 
cesses are  identical.  Since  in  the  produc- 
tion of  membrane-bone  the  changes  within 
pre-existing  cartilage  do  not  come  into  ac- 
count, the  development  is  less  complicated 
and  concerns  primarily  only  a  formative  pro- 
cess. 

Although  the  development  of  all  osseous 
tissue  outside  of  cartilage  may  be  grouped 
under  the  general  heading  of  intramembranous,  two  phases  of  this  mode  of  bone- 
formation  must  be  recognized  ;  the  one,  the  intramembranous.  in  the  more  literal 
sense,  applying  to  the  development  of  such  bones  as  those  of  the  vault  of  the  skull 
and  of  the  face,  in  which  the  osseous  tissue  is  formed  within  the  mesoblastic  sheets, 
and  the  other,  the  subperiosteal,  contributing  with  few  exceptions  to  the  production 
of  every  skeletal  segment,  in  which  the  bone  is  deposited  beneath  rather  than  within 
the  connective-tissue  matrix.  In  consideration  of  its  almost  universal  participation, 
the  periosteal  mode  of  development  will  be  regarded  as  the  representative  of  the 
intramembranous  formation. 

Subperiosteal  Bone. — The  young  periosteum,  it  will  be  recalled,  consists  of 
an  outer  and  more  compact  fibrous  and  an  inner  looser  osteogenetic  layer.  The 
latter,  in  addition  to  numerous  blood-vessels,  contains  young  connective-tissue  ele- 
ments and  delicate  bundles  of  fibrous  tissue.  These  cells,  or  osteoblasts,  become 
more  regularly  and  closely  arranged  along  the  fibrillae,  about  which  is  deposited  the 


Embryonal 
cartilage 


V 


:  of  foetus  of  five 


SUBPERIOSTEAL    BONE. 


99 


new  bone-tissue,  the  osteoblasts  becoming  enclosed  within  the  homogeneous  matrix 
to  constitute  the  bone-cells.     The  osseous  trabecula  thus  begins  to  increase  not  only 

Fig.  130. 

PllPfF-  '      '•'•l*       '  ''^.^L  Articular  cartilage 


%i|§§ Columns  :f  • 

?* ?fl.  lage-cells 


'■•■«>>.v-^ 


V 


-  Marrow-tissue 


-  Epiphyseal  bone 


.««»: 


-      ..  'J;3     '5!   ,.  ■%!;-■    5      .-":.,  r\3        ,.=  -:,  -"'  -".!  .•S.'7.-;  •    "';"'•; Remains     of     caiti 

1....K-..I  ep.pln-. 


nd  diaphysis 


■!'-:."•  'Hi'm.'/^ 


■Ilia- 


■  Diaphyseal  bone 


Longitudinal  section  including  epiphysis  and  upper  end  of  diaphysis  of  long  bone  of  cat,  just  befi 
of  the  head  and  shaft  takes  place.     X  50. 

in  length,  by  the  addition  of  the  last-formed  matrix  upon  the  supporting  fibres,  but 
also  in  width,  by  the  deposition  of  new  layers  of  osseous  material  by  the  osteoblasts. 


ioo  HUMAN    ANATOMY. 

These  cells  cover  the  exterior  of  the  trabecular  as  they  lie  surrounded  by  the  young 
marrow-tissue  which  extends  from  the  osteogenetic  layer  of  the  periosteum  into  the 
intertrabecular  spaces.  The  union  of  the  young  trabecular  results  in  the  production 
of  a  subperiosteal  net-work  of  osseous  tissue,  the  peripheral  spongy  bone.  The  latter 
forms  a  shell  surrounding  the  central  endochondral  bone,  or,  where  the  latter  has 
already  disappeared,  the  central  marrow-cavity  of  the  shaft.  The  two  processes, 
central  and  peripheral  bone-formation,  progress  simultaneously,  so  that  the  produc- 
tions of  both  lie  side  by  side,  often  in  the  same  microscopical  field  (Fig.  131). 

Fig.  131. 


-Fibrous  layer  of 
periosteum 


-<  isteogenetic 
layer  of  peri- 
osteum 


i  m 


_Bone  trabecula 


tf*      \      PI  ^8L^r*,f* - -^ : Remains  of, 


Portion  of  developing  humerus  of  foetal  sheep,  showing  periosteal  and  central  spongy  bone.     X  160. 

The  development  of  compact  bone  involves  the  partial  absorption  of  the 
subperiosteal  net-work  of  osseous  trabecular  and  the  secondary  deposition  of  new 
bone-tissue.  The  initial  phase  in  the  conversion  of  the  peripheral  spongy  bone  into 
compact  substance  is  the  partial  absorption  of  the  trabeculae  by  the  osteoclasts  of  the 
primary  marrow-tissue  ;  in  consequence  of  this  process  the  close  reticulum  of  perios- 
teal bone  is  reduced  to  a  delicate  framework,  in  which  the  comparatively  thin  remains 
of  the  trabecular  separate  the  greatly  enlarged  primary  marrow-cavities,  which,  now 
known  as  the  Haversian  spaces,  are  of  round  or  oval  form. 

After  the  destructive  work  of  the  osteoclasts  has  progressed  to  the  required 
extent,  the  osteoblastic  elements  of  the  young  marrow  contained  within  the  Haver- 


INTRAMEMBRANOUS    BONE. 


-         '-:«':', 


( 


sian  spaces  institute  a  secondary  formative  process,  by  which  new  bone  is  deposited 
on  the  walls  of  the  Haversian  spaces.  This  process  is  continued  until,  layer  after 
layer,  almost  the  entire  Haversian  space  is  rilled  with  the  resulting  concentrically 
disposed  osseous  lamellae  ;  the  cavity  remaining  at  the  centre  of  the  new  bone  per- 
sists as  the  Haversian  canal,  while  the  concentrically  arranged  layers  are  the  lamella? 
of  the  Haversian  system,  the  extent  of  the  latter  corresponding  to  the  form  and  size 
of  the  Haversian  space  in  which  the  secondary  deposit  of  bone  occurs.  It  is  evident 
from  the  development  of  the  compact  substance  that  the  interstitial  or  ground- 
lamellae  of  the  adult  tissue  correspond  to  the  remains  of  the  trabecular  of  the  primary 
spongy  bone  ;  these  lamellae  are,  therefore,  genetically  older  than  those  constituting 
the  Haversian  systems.  The  details  of  the  formation  of  the  Haversian  lamellae,  in- 
cluding the  deposition  of  the  matrix  and  the  inclusion  of  the  osteoblasts  to  form  the 
bone-cells,  are  identical  with  those  of  the  production  of  the  trabeculae  of  the  earlier 
bone. 

Intramembranous  Bone. — The  development  of  certain  bones,  as  those  con- 
stituting  the  vault  of  the  skull  and   the  greater  part  of  the  skeleton  of  the  face, 
differs  in  its  earliest  details  from  that  of  the  subperiosteal  bone,  although  the  essen- 
tial features  of  the  processes  are  identi- 
cal.     The  mode  by  which  these  mem-  Fig.  132. 
brane-bones    are    formed    may    claim, 
therefore,  a  brief  consideration. 

The  early  roof  of  the  skull  consists, 
except  where  developing  muscle  occurs, 
only  of  the  integument,  the  dura  mater, 
and  an  intervening  connective-tissue 
layer  in  which  the  membranous  bones 
are  formed.  The  earliest  evidences  of 
ossification  usually  appear  about  the 
middle  of  the  area  corresponding  to  the 
later  bone,  delicate  spicules  of  the  new 
bone  radiating  from  the  ossific  centre 
towards  the  periphery.  As  the  tra- 
beculae increase  in  size  and  number  they 
join  to  form  a  bony  net-work  (Fig. 
132),  close  and  robust  at  the  centre  and 
wide-meshed  and  delicate  towards  the 
margin  where  the  reticulum  fades  into 
the  connective  tissue.  With  the  con- 
tinued growth  of  the  bony  tissue  the 

net-work  becomes  more  and  more  compact  until  it  forms  an  osseous  plate,  which 
gradually  expands  towards  the  limits  of  the  area  devoted  to  the  future  bone.  For  a 
time,  however,  until  the  completion  of  the  earliest  growth,  the  young  bones  are 
separated  from  their  neighbors  by  an  intervening  tract  of  unossified  connective  tissue. 
Subsequent  to  the  earlier  stages  of  the  formation  of  the  tabular  bones,  the  continued 
growth  takes  place  beneath  the  periosteum  in  the  manner  already  described  for 
other  bones. 

On  examining  microscopically  the  connective  tissue  in  which  the  formation  of 
membrane-bone  has  begun,  this  layer  is  seen  to  contain  numerous  osteogenetic fibres 
around  and  upon  which  are  grouped  many  irregularly  oval  or  stellate  cells  ;  the  latter 
correspond  to  the  osteoblasts  in  other  locations,  since  through  the  agency  of  these 
elements  the  osseous  matrix  is  deposited  upon  the  fibres.  As  the  stratum  of  bony 
material  increases  some  of  the  cells  are  enclosed  to  form  the  future  bone-cor- 
puscles. Although  the  osteogenetic  fibres  correspond  to  delicate  bundles  of  fibrous 
tissue,  they  are  stiffer,  straighter,  and  present  less  indication  of  fibrillar  structure. 
Since  the  fibres  forming  the  ends  of  the  bony  spicules  generally  spread  out,  they  fre- 
quently unite  and  interlace  with  the  fibres  of  adjacent  spicules,  thus  early  suggesting 
the  production  of  the  bony  net-work  which  later  appears. 

Growth  of  Bone. — It  is  evident,  since  the  new  bone  is  deposited  beneath  the 
periosteum,  that  the  growth  of  the  subperiosteal  bone  results  in  an  increased  diame- 


Parietal  bone  of  human  foetus  of  three  months,  showing 
trabecular  net-work  of  intramembranous  bone.     X  5. 


102  HUMAN   ANATOMY. 

ter  of  the  shaft  as  well  as  in  thickening  of  the  osseous  wall  separating  the  medullary 
cavity  from  the  surface.  In  order,  therefore,  to  maintain  the  balance  between  the 
longitudinal  growth  of  the  medullary  cavity,  effected  by  the  absorption  of  the  endo- 
chondral bone,  and  its  lateral  expansion,  the  removal  of  the  innermost  portions  of 
the  subperiosteal  bone  soon  becomes  necessary.  Absorption  of  the  older  internal 
trabecular  thus  accompanies  the  deposition  of  new  osseous  tissue  at  the  periphery  ; 
by  this  combination  of  destructive  and  formative  processes  the  thickness  of  the 
cylindrical  wall  of  the  compact  substance  of  the  diaphysis  is  kept  within  the  proper 
limits  and  the  increased  diameter  of  the  medullary  cavity  insured. 

Throughout  the  period  of  early  growth  the  increase  in  length  of  the  bone  is 
due  to  the  addition  of  new  cartilage  at  the  ends  ;  later,  the  cartilaginous  increments, 
contributed  by  the  chondrogenetic  layer  of  the  perichondrium,  are  supplemented  by 
interstitial  expansion  following  the  multiplication  of  the  existing  cartilage-cells.  On 
attaining  the  maximum  growth  and  the  completion  of  epiphyseal  ossification,  a  por- 
tion of  the  cartilage  may  persist  to  form  the  articular  surfaces.  After  the  cessation 
of  peripheral  growth  and  the  completion  of  the  investing  layer  of  compact  substance, 
the  osteogenetic  layer  of  the  periosteum  becomes  more  condensed  and  less  rich  in 
cellular  elements,  retaining,  however,  an  intimate  connection  with  the  last-formed 
subjacent  bone  by  means  of  the  vascular  processes  of  its  tissue,  which  are  in  con- 
tinuity with  the  marrow-tissue  within  the  intraosseous  canals.  In  addition  to  being 
the  most  important  structure  for  the  nutrition  of  the  bone,  on  account  of  the  blood- 
vessels which  it  supports,  the  periosteum  responds  to  demands  for  the  production  of 
new  osseous  tissue,  whether  for  renewed  growth  or  repair,  and  again  becomes  active 
as  a  bone-forming  tissue,  its  elements  assuming  the  role  of  osteoblasts  in  imitation 
of  their  predecessors. 


THE   SKELETON: 


INCLUDING 


THE   BONES   AND   THE   JOINTS. 


Fig. 


133- 


The  skeleton  forms  the  framework  of  the  body.  In  the  widest  sense  it  includes, 
besides  the  bones,  certain  cartilages  and  the  joints  by  which  the  different  parts  are 
held  together.  '  The  skeleton  of  vertebrates 
is  divided  into  the  axial  and  the  appendic- 
ular ;  the  former  constitutes  the  support- 
ing framework  of  the  trunk  and  head  ;  the 
latter,  that  of  the  extremities. 

The  Axial  Skeleton. — The  general 
plan  of  the  axial  skeleton  of  the  trunk  is 
as  follows  :  a  rod  composed  of  many  bony 
disks  (the  vertebral  bodies)  connected  by 
fibro-cartilage  separates  two  canals,  a  dorsal 
and  a  ventral.  In  most  vertebrates  the  rod 
is  in  the  main  horizontal,  with  the  dorsal 
canal  above  and  the  ventral  below  ;  but  in 
man  the  rod  is  practically  vertical,  with  the 
dorsal  canal  behind  and  the  ventral  in  front. 
The  former  is  called  the  neural,  because  it 
encloses  the  central  nervous  system  ;  the 
latter,  the  visceral.  The  vertebral  column 
has  developed  about  the  primary  axis,  the 
notochord.  The  neural  canal  is  enclosed 
by  a  series  of  separate  arches  springing  one 
from  each  vertebra.  The  skeletal  parts  of 
the  anterior,  or  ventral,  canal  are  less  nu- 
merous ;  they  are  the  ribs,  the  costal  carti- 
lages, and  the  breast  bone.  Above  is  the 
bony  framework  of  the  head,  or  the  skull. 
This  also  is  divided  into  a  dorsal  and  a  ven- 
tral portion  by  a  bony  element  which  is 
apparently  a  continuation  of  the  bodies  of 
the  vertebrae,  and,  indeed,  is  actually  de- 
veloped, in  part,  around  the  front  of  the 
notochord.  The  cephalic  axis,  however,  is 
bent  at  an  angle  with  the  vertebral  bodies, 
so  that  the  neural  arches,  which  here  en- 
close the  brain,  are  chiefly  no  longer  be- 
hind but  above.  Below  and  in  front  of 
the  brain-case  is  the  face,  which  contains 
the  beginning  of  the  digestive  tube,  of 
which  the  jaws  and  teeth  are  special  organs. 
In  the  head  we  do  not  find  the  separation 
of  the  parts  enclosing  the  brain  into 
series  of  vertebrae,  but  they  are  clearly  a 
continuation  of  the  vertebral  arches,  the 
posterior,  or  occipital,  division  strongly  suggesting  a  vertebra.  The  face  is  far  more 
complicated,  the  vertebral  plan  being  lost.     In  short,  the  axial  skeleton  consists  of  a 


The  tinted  port 


constitute  the  axial  skeleton ; 
nted,  the  appendicular  skeleton. 


104  HUMAN    ANATOMY. 

central,  many-jointed  rod  bent  forward  near  the  top,  with  very  perfect  bony  walls 
behind  and  above  it,  enclosing  the  central  nervous  system,  and  very  imperfect  bony 
and  cartilaginous  walls  before  and  below  it,  enclosing  the  digestive  apparatus  and  its 
associates,  the  circulatory,  respiratory,  urinary,  and  reproductive  organs. 

The  Appendicular  Skeleton  has  an  entirely  distinct  origin  ;  it  is  the  frame- 
work of  the  limbs.  It  consists  of  two  girdles,  a  thoracic  and  a  pelvic,  to  each  of 
which  is  attached  a  series  of  segments,  the  terminal  one  of  which  expands  into  five 
rays, — -fingers  and  toes.  According  to  some  anatomists,  the  true  vertebrate  plan  is 
of  seven  terminal  rays,  but,  the  question  being  still  undecided,  the  more  usual  sys- 
tem is  followed.  Each  of  these  rays  consists  of  three  or  four  bones.  Proximal  to  this 
comes  a  series  of  short  bones, — wrist  and  ankle  ;  still  nearer,  a  pair  of  bones, — -fore- 
arm and  leg  ;  then  a  single  bone, — arm  and  thigh;  and  lastly  a  bony  arch, — the 
girdle. 

In  man,  the  thoracic  girdle,  made  up  of  collar-bone  and  shoulder-blade,  lies 
external  to  the  chest,  while  the  pelvic  girdle  fuses  on  each  side  into  one  bone,  meets 
its  fellow  in  front,  and  unites  with  the  bodies  of  certain  vertebrae.  Thus,  besides 
bearing  a  limb,  the  pelvic  girdle  forms  a  part  of  the  wall  of  the  abdominal  and  the 
pelvic  cavities  and  would  seem  to  belong  to  the  axial  skeleton,  but  embryology  and 
comparative  anatomy  show  that  it  does  not. 

GENERAL   CONSIDERATION   OF   THE   BONES. 

The  bones  have  the  physiological  function  of  bearing  weight,  of  affording  pro- 
tection, and  especially,  by  the  systems  of  levers  composing  the  limbs,  of  effecting 
movements  through  the  action  of  the  muscles.  They  must,  therefore,  be  capable  of 
resisting  pressure,  accidental  violence,  and  the  strain  caused  by  the  pull  of  the 
muscles.  The  size  of  the  bones  must  be  such  that  besides  serving  the  obvious  needs 
of  support  and  protection  they  may  be  sufficiently  large  to  offer  adequate  surface  for 
the  origin  and  insertion  of  muscles,  and  the  shape  must  be  such  as  to  allow  this 
without  undue  weight. 

Shapes  of  Bones. — Bones  are  divided,  according  to  their  form,  into  long, 
flat,  and  irregular ;  such  classification,  however,  is  of  little  value,  since  many  bones 
might  be  variously  placed. 

Long  bones  form  the  best-defined  group.  They  consist  of  a  shaft  and  two 
extremities,  each  of  which  takes  part  in  the  formation  of  a  joint,  or,  as  in  the  case  of 
the  last  phalanges,  is  terminal. 

Flat  bones,  where  very  thin,  consist  of  a  single  plate  ;  where  thicker,  they  con- 
sist of  two  plates  separated  by  spongy  substance  called  diploe. 

Irregular  bones  may  be  regarded  as  embracing  all  others.  The  group  of  the 
so-called  short  bones  has  no  significance. 

Sesamoid  Bones,  with  the  exception  of  the  patella,  are  not  usually  included 
in  the  description  of  the  skeleton.  With  the  above  exception,  they  are  small  rounded 
bones  developed,  for  the  most  part,  in  the  capsules  of  joints,  but  sometimes  in  ten- 
dons. Usually  one  surface  is  cartilage-covered,  and  either  enters  into  the  formation 
of  a  joint  or,  separated  by  a  bursa,  plays  on  another  bone,  or  on  cartilage  or  liga- 
ment. Their  function  is  to  obviate  friction,  and,  in  some  cases,  to  change  the  direc- 
tion of  the  pull  of  a  muscle.  The  number  of  sesamoid  bones  is  very  variable  ;  but 
the  usual  idea  that  they  are,  so  to  speak,  accidental,  depending  on  the  mechanics  of 
a  certain  joint  or  tendon,  must  probably  be  abandoned.  They  are  rather  to  be  con- 
sidered as  real  parts  of  the  skeleton,1  all  of  which  have  their  places  in  certain 
animals,  but  all  of  which  either  are  not  developed,  or,  if  they  do  appear,  are  again 
lost  in  others.  Thus,  certain  sesamoid  bones  of  the  fingers  are  very  frequent  in  the- 
fcetus  and  very  rare  in  the  adult. 

Growth  of  Bones. — The  microscopical  details  of  bone-growth  are  given  else- 
where (page  94).  Suffice  it  to  say  here  that  each  bone  has  certain  so-called  centres 
of  ossificatio7i  from  which  the  formation  of  the  new  bone  spreads.  In  the  long  bones 
there  is  one  main  centre  in  the  shaft,  or  diaphysis,  which  appears  in  the  first  half  of 
total  life.      Other  centres  appear,  usually  some  time  after  birth,  in  the  ends  of  the 

1  Thilenius  :  Morpholog.  Arbeiten,  Bd.  vi.,  1896. 


MECHANICS   OF    BONE.  105 

bones.  There  may  be  one  or  several  in  each  end.  The  part  formed  around  each 
of  these  secondary  centres  is  called  an  epiphysis.  Growth  takes  place  chiefly  in  the 
cartilage  between  the  epiphyses  and  the  shaft.  When,  therefore,  a  joint  is  resected 
in  childhood  the  surgeon  tries  to  leave  a  part  of  the  epiphysis  in  place.  A  curious 
relation  exists  between  the  course  of  the  chief  medullary  artery  of  the  shaft  of  a  long 
bone  and  the  behavior  of  the  epiphyses.  The  epiphysis  towards  which  the  vessel  is  di- 
rected is  the  last  to  appear  and  the  first  to  unite.  (The  fibula  furnishes  an  exception.  ) 
As  a  rule,  also,  the  largest  epiphyses  appear  first  and  unite  last.  In  long  bones  with 
an  epiphysis  at  one  end  only,  the  nutrient  canal  leads  towards  the  opposite  extremity. 

Mechanics  of  Bone. — A  long  bone  has  a  hollow  shaft  containing  marrow, 
the  wall  being  of  compact  bone.  The  hollowness  of  the  shaft  takes  from  the  weight, 
and,  moreover,  conforms  to  the  well-known  law  that  a  given  quantity  of  matter  is 
much  stronger,  both  lengthwise  and  crosswise,  when  disposed  as  a  hollow  cylinder 
than  as  a  solid  one  of  equal  length.  The  proportion  of  the  central  or  medullary 
cavity  is  not  the  same  in  all  bones.  Perhaps,  as  an  average,  its  diameter  may  be 
said  to  equal  one-third  of  that  of  the  bone.  In  the  shaft  this  cavity  is  crossed  by  a 
few  bony  trabecular,  almost  all  of  which  are  destroyed  in  maceration.  Towards  the 
ends,  as  the  outer  wall  becomes  thinner,  large  numbers  of  thin  plates  spring  from  its 
inner  surface  and  incline  towards  one  another  in  graceful  curves,  until  at  last  the 
expanded  end  of  the  bone  consists  of  spongy  or  cancellated  tissue  enclosed  within  a 
delicate  wall  of  compact  substance.  The  arrangement  of  these  plates  is  distinctly  pur- 
poseful, since  it  has  been  shown  that  they  are  so  disposed  as  to  correspond  with  the 
stress-lines  an  engineer  would  construct  for  the  special  purpose  served  by  the  end  of 
the  bone.  None  the  less,  it  would  be  unwarranted  to  maintain  that  mathematical 
correctness  is  always  to  be  found,  or  that  there  are  not  other  modifying  influences. 
The  internal  structure  of  all  bones,  excepting,  perhaps,  those  of  the  skull,  is  of  this 
nature,  so  that  the  following  remarks  apply  to  spongy  bone  in  general. 

The  delicate  cancellated  structure  is  for  the  most  part  in  thin  plates.  The  sim- 
plest arrangement  occurs  in  a  short  bone  exposed  to  pressure  only  at  two  opposite 
surfaces  ;  in  such  cases  the  plates  run  between  these  surfaces  with  few  and  insignifi- 
cant cross-pieces.  Where  severe  pressure  may  come  in  almost  any  direction,  as  in 
the  case  of  the  globular  heads  of  the  humerus  and  femur,  the  round-meshed  pattern 
predominates,  producing  a  very  dense  spongy  structure  which  may  be  represented 
diagrammatically  by  drawing  lines  crossing  at  right  angles  and  by  enlarging  every 
point  of  intersection.  In  the  midst  of  this  round-meshed  type  there  is  very  fre- 
quently a  central  core  with  stronger  plates  and  larger  spaces.  The  vaulted  system 
is  found  at  the  projecting  ends  of  bones,  and  between  the  round-meshed  cancellated 
substance  and  the  shaft.  Several  special  arrangements  will  be  described  in  connec- 
tion with  the  bones  in  which  they  occur.  An  epiphysis,  until  it  has  fused,  shows  the 
mechanical  structure  of  a  separate  bone.  A  process  for  the  attachment  of  muscles 
or  ligaments  generally  contains  a  very  light  internal  structure,  the  surface  of  the  shaft 
of  the  bone  being  rarely  continued  under  it.  The  continuation  of  the  fibres  of 
attached  tendons  is  not  represented  by  internal  plates  of  bone,  although  the  oppo- 
site opinion  has  supporters. 

Certain  of  the  bones  of  the  cranium  and  the  face  are  in  parts  hollowed  out  into 
mere  shells  bounding  a  cavity  lined  with  mucous  membrane  continuous  with  that  of 
the  nose  or  the  pharynx. 

The  elasticity  of  bones  is  enhanced  by  curves.  The  long  bones  very  usually 
present  a  double  curve.  It  has  been  maintained  that  these  curves  form  a  spiral 
structure.  There  are  striking  instances  of  it,  but  the  universality  of  the  law  is  not 
proved  ;  although  shocks  are  thus  lessened,  the  passage  of  one  curve  to  another  is 
a  weak  point  in  the  bone. 

The  ends  of  the  long  bones  are  enlarged  for  articulation  with  their  neighbors. 
The  greater  part  of  this  enlargement  forms  the  joint,  the  various  shapes  of  which 
will  be  discussed  later.  Besides  this,  there  are  usually  at  the  ends  prominences  for 
muscles.  The  shaft  generally  bears  ridges,  which  in  some  cases  are  made  of  dense 
bone  and  materially  add  to  the  strength  of  the  bone.  A  ridge  or  prominence 
usually  implies  the  insertion  of  a  fibrous  aponeurosis  or  a  tendon.  Muscular  fibres, 
however,  may  spring  from  the  periosteum  over  a  flat  surface. 


106  HUMAN   ANATOMY: 

Parts  of  Bones. — The  following  are  some  of  the  names  applied  to  features 
of  bone  : 

A  process  is  a  general  term  for  a  projection. 

A  spine  or  spinous  process  is  a  sharp  projection. 

A  tuberosity  is  a  large  rounded  one,  a  tubercle  is  a  small  one,  either  rounded  or 
pointed. 

A  crest  is  a  prominent  ridge. 

A  head  is  an  enlargement  at  the  end  of  a  bone,  in  part  articular. 

A  neck  is  a  constriction  below  a  head. 

A  condyle  is  a  rounded  articular  eminence,  generally  a  modification  of  a  cylinder. 

A  fossa  is  a  pit. 

A  glenoid  cavity  is  a  shallow  articular  depression. 

A  cotyloid  cavity  is  a  deep  one. 

A  sulcus  is  a  furrow. 

&  foramen  is  a  hole,  in  the  sense  of  a  perforation. 

A  sinus  is  the  cavity  of  a  hollow  bone,  equivalent  to  antrum.  It  is  used  also 
to  designate  certain  grooves  for  veins  in  the  cavity  of  the  cranium. 

In  addition  to  the  cartilage-covered  articular  surfaces  proper,  the  fresh  bones 
show  in  some  places  a  plate  of  cartilage  quite  like  one  for  a  joint;  such  plates  serve  to 
lessen  the  friction  of  a  tendon  playing  over  the  bone.  In  other  places  a  look  of  pecul- 
iar smoothness  is  conferred  by  the  presence  of  a  bursa,  although  cartilage  is  wanting. 

Sex  of  Bones. — Female  bones  are  characterized  in  general  by:  (a)  a  greater 
slenderness;  {b)  a  smaller  development  of  processes  and  ridges  for  muscular  attach- 
ment1; if)  and,  most  important  of  all,  the  small  size  of  the  articular  surfaces.  These 
guides  usually  suffice  to  determine  the  sex  of  the  chief  bones;  some,  especially  those 
of  the  pelvis,  possess  characteristic  sexual  differences  of  form. 

Age  of  Bones. — At  birth  the  long  bones  have  cartilaginous  ends  in  which, 
with  one  or  two  exceptions,  the  centres  of  ossification  have  not  yet  appeared.  Many 
bones  at  this  period  still  consist  of  several  pieces  which  ultimately  fuse.  The  shape 
and  proportions  are  in  some  cases  different  from  those  of  the  adult.  Sexual  differ- 
ences cannot  in  most  cases  be  determined.  During  the  first  years  new  centres  of 
ossification  appear,  distinct  pieces  unite,  and  the  proportions  change  from  the  type 
of  the  infant  to  that  of  the  child.  Towards  puberty  important  further  changes  in 
proportion  occur,  and  sexual  differences  develop. 

After  puberty the  bones  present  three  stages, — adolescence,  maturity,  and  senility. 
In  the  first  the  union  of  the  epiphyses  is  going  on  ;  after  this  has  taken  place  the 
line  of  separation  is  visible  for  a  time,  but  gradually  disappears.  Our  knowledge  of 
the  time  at  which  these  changes  occur  enables  us  to  determine  the  age  of  the  skel- 
eton. The  long  period  of  maturity  presents  little  that  allows  of  a  precise  estimate 
of  age.  The  separate  bones  of  the  vault  of  the  cranium  gradually  fuse  into  one. 
The  senile  skeleton  in  its  extreme  stage  is  very  striking.  There  is  a  general  atrophy 
of  the  bones  both  within  and  without,  those  of  the  face  becoming  in  parts  of  papery 
thinness  ;  not  only  the  cavities  within  the  cranial  bones  become  larger,  but  also  the 
spaces  within  the  cancellous  tissue  inside  the  bones,  due  to  the  partial  absorption  of 
the  spongy  substance.  The  only  bones,  however,  which  show  a  distinct  change  of 
form  are  the  jaws,  and  this  is  a  secondary  result  of  the  loss  of  the  teeth.  In  many 
cases,  however,  senile  absorption  and  atrophy  do  not  occur,  except,  perhaps,  in  the 
head  ;  it  may  be,  therefore,  absolutely  impossible  to  distinguish  a  long  bone  of  an 
old  subject  from  one  of  an  individual  in  early  maturity.  The  periods  at  which  the 
age  of  bones  is  most  often  a  matter  of  medico-legal  inquiry  are  at  the  time  of  birth 
and  in  childhood  and  youth.  The  dates  of  the  first  appearance  of  ossification  in 
the  various  bones  are  the  criteria  for  the  first.  These  are  to  be  used,  however,  with 
great  caution,  since  variation  is  considerable.  The  information  to  be  derived  from 
consideration  of  the  general  development  of  the  body  is  perhaps  of  equal  value. 
The  same  holds  good  for  childhood  and  adolescence.  The  particular  point  on  which 
the  writer  holds  strong  views,  based  on  his  own  observations,  differing  from  those 
generally  accepted,   is  as  to  the  time  of  union  of  the  epiphyses  at  the  end  of  ado- 

1  Dwight :  American  Journal  of  Anatomy,  Vol.  iv.,  1904. 


GENERAL   CONSIDERATION    OF   THE  JOINTS.  107 

lescence.  He  is  convinced,  as  his  statements  will  show,  that  this  union  occurs  earlier 
than  is  generally  taught. 

Relation  of  the  Bones  to  the  Figure. — While  it  may  be  said  that  power- 
ful muscles  leave  their  imprint  on  the  bones  in  strong,  rough  ridges,  yet  it  is  impos- 
sible to  give  a  trustworthy  description  of  the  figure  from  the  size  and  shape  of  the 
bones,  since  these  are  determined  chiefly  by  prenatal  influences.  Very  delicate, 
even  puny,  bodies  may  have  large  and  strong  bones,  and  great  muscular  develop- 
ment may  coexist  with  a  light  framework. 

Variations. — Besides  the  great  range  of  individual  variation,  without  departure 
from  the  usual  type,  bones  occasionally  show  greater  peculiarities.  These  may  occur 
through  either  excess  or  defect  of  ossification.  Structures  which  are  normally  car- 
tilaginous or  fibrous  may  become  replaced  by  bone,  and  abnormal  foramina  may 
occur  in  consequence,  or  to  accommodate  the  aberrant  course  of  blood-vessels  or 
nerves.  The  most  interesting  of  these  variations  are  such  as  present  an  arrangement 
which  is  normal  in  some  of  the  lower  animals.  Many  variations  may  be  plausibly 
accounted  for  as  reversions,  but  others  cannot  be  explained  in  this  way  according 
to  any  conceivable  scheme  of  descent.  By  speaking  of  these  variations  as  animal 
analogies  we  avoid  theories  and  keep  to  scientific  truth. 

Number  of  Bones. — The  usual  enumeration  of  the  bones  composing  the 
human  skeleton  is  misleading,  for  while  it  is  customary  in  some  parts,  as  the  head, 
to  count  each  bone,  in  others,  like  the  sacrum  and  the  hyoid,  only  the  ultimate 
condition,  after  union  of  the  component  segments,  is  considered.  In  other  cases, 
like  the  sternum,  there  may  be  grave  doubt  which  course  is  the  proper  one  to 
follow  ;  and  finally,  as  in  the  coccyx,  the  number  is  variable.  Bearing  these  impor- 
tant facts  in  mind,  it  may  be  stated  that  the  human  skeleton  in  middle  life  usually 
comprises,  as  conventionally  reckoned,  two  hundred  separate  bones,  excluding  the 
sesamoids  within  the  tendons  of  the  short  flexor  of  the  thumb  and  of  the  great  toe 
and  the  ear-ossicles,  but  including  the  patella  and  the  hyoid  bone.  Of  this  number, 
seventy-four  bones  belong  to  the  axial  and  one  hundred  and  twenty-six  to  the  appen- 
dicular skeleton. 

The  skeleton  is  advantageously  described  in  the  following  order  :  the  spine,  the 
thorax,  the  head,  the  shoulder-girdle  and  the  arm,  the  pelvic  girdle  and  the  leg. 
The  account  of  the  bones  of  each  region  is  succeeded  by  that  of  the  joints  and  the 
ligaments  holding  them  together,  followed  by  a  consideration  of  the  region  as  a 
whole  and  of  its  relation  to  the  surface.  The  applications  of  anatomical  details  of 
the  skeleton  to  the  requirements  of  medicine  and  surgery  are  pointed  out  in  appro- 
priate places. 

GENERAL   CONSIDERATION    OF  THE  JOINTS. 

A  joint  or  articulation  implies  the  union  of  two  or  more  bones.  Joints  may  be 
divided,  according  to  their  mobility,  into  three  great  classes  :  the  fixed  joint  {Syn- 
arthrosis), the  half-joint  {Amphiarthrosis) ,  and  the  TRUE  JOINT  (Diarthrosis) . 

Fixed  Joints. — These  allow  no  motion  in  the  mature  condition,  and  are  rep- 
resented by  two  subdivisions,  the  Suture  and  the  Synchondrosis. 

The  suture  is  the  direct  union  of  two  bones  which  at  first  may  be  separated  by 
membrane  or  by  fibrous  tissue,  but  which  eventually  become  firmly  united.  Several 
varieties  of  this  form  of  union  are  recognized  ;  thus  a  serrated  suture  is  one  in  which 
the  edges  are  interlocked,  as  the  teeth  of  two  saws  ;  conspicuous  examples  are  seen 
in  the  interparietal  and  the  parieto-occipital  junctures.  Frequently  one  bone  tends 
to  overlap  at  one  end  of  the  suture  and  to  be  overlapped  at  the  other.  A  squamous 
suture  is  one  in  which  a  scale-like  bone  very  much  overlaps  another,  as  in  the  relation 
between  the  temporal  and  the  parietal  bone.  An  ha?-?nonic  suture  is  one  in  which 
two  approximately  plane  surfaces  are  apposed,  as  in  the  case  of  the  vertical  plate  of 
the  palate  and  the  maxillary  bone.  The  term  grooved  suture  is  sometimes  employed 
to  designate  a  form  of  union  in  which  one  bone  is  received  within  the  grooved  sur- 
face of  another,  as  the  rostrum  of  the  sphenoid  and  the  vomer.  Wormian  bo?ies  are 
small,  irregular  ossifications  which  appear  as  bony  islands  in  the  course  of  a  suture. 
Familiar  examples  of  these  are  seen  in  the  line  of  the  parieto-occipital  suture. 


io8 


HUMAN   ANATOMY. 


Synchondrosis  is  the  union  of  two  bones  by  an  intervening  strip  of  cartilage, 
which  usually  ultimately  becomes  replaced  by  bone.  Such  is  the  union  between 
the  pieces  of  the  body  of  the  sternum  and  between  certain  bones  of  the  base  of  the 
skull.  The  term  is  also  applied  to  the  union  of  the  shaft  and  the  epiphyses  of  long 
bones. 

Half-Joints,  including  Symphysis  and  Syndesmosis.  From  the  stand-point  of 
development,  there  is  no  fundamental  difference  between  symphyses  and  the  true 
joints.  In  both  cases  a  small  cavity  appears  within  the  intervening  mesoblastic  tissue 
connecting  the  ends  of  the  embryonal  bones.  This  small  cavity,  in  the  case  of  the 
true  joints,  rapidly  increases,  and  later  is  lined  by  the  flattened  mesoblastic  cells 
investing  the  subsequently  differentiated  synovial  membrane.  When,  on  the  con- 
trary, the  bones  are  to  become  united  by  dense  fibrous  and  fibro-cartilaginous  tissue, 
as  in  the  case  of  a  symphysis,  the  interarticular  space  is  always  a  mere  cleft  sur- 
rounded by  the  interlacing  and  robust  bundles  of  the  dense  tissue  forming  the  union 
in  the  mature  joint. 

A  symphysis  implies  great  strength  and  very  limited  and  indefinite  motion, 
there  being  no  arrangement  of  surfaces  to  determine  its  nature.  The  chief  function 
of  this  form  of  union  seems  rather  to  be  to  break  shocks.  The  central  cavity  is  not 
always  found.  The  symphysis  pubis  (Fig.  361)  is  a  typical  half -joint.  Those  con- 
necting the  bodies  of  the  vertebrae  are  usually  so  classed,  but  it  is  not  certain  that 
they  quite  agree  either  in  structure  or  development  with  the  description.      A  transi- 


Fig.  134. 


Diagrams  of  various  forms  of  suture.     A,  serrated  ;  B,  squamous  ;  C,  harmonic  ;  D,  grooved. 

tional  form  leading  from  the  symphysis  to  the  true  joint  is  one  in  which  the  limited 
synovial  cavity,  instead  of  being  in  the  centre  of  a  mass  of  fibro-cartilage,  lies  between 
two  cartilaginous  surfaces,  somewhat  like  that  of  a  true  joint,  but  so  interlocked  and 
surrounded  by  short,  tense  fibres  as  to  preclude  more  than  very  slight  motion.  This 
arrangement  is  often  seen  in  the  articulation  between  the  sacrum  and  ilium,  some- 
times improperly  called  the  sacro-iliac  synchondrosis. 

Syndesmosis  is  to  be  included  among  the  half-joints.  It  is  the  binding 
together  of  bones  by  fibres,  either  in  bundles  or  as  a  membrane,  without  any  inter- 
vening cartilage  ;  an  example  of  this  arrangement  is  seen  in  the  union  effected  by 
the  interosseous  ligament  in  the  lower  tibio-fibular  articulation. 

True  Joints. — These  articulations  develop  in  a  similar  manner  to  the  half- 
joints,  except  that  the  opposed  ends  of  the  developing  bones  are  of  hyaline  carti- 
lage, fibro-cartilage  being  present  only  at  the  sides,  except  in  the  case  of  a  compound 
joint,  where  it  forms  the  intervening  plate.  The  tissue  at  the  sides  of  the  articular 
cleft  differentiates  into  two  layers, — the  inner,  which  is  the  synovial  membrane ;  consist- 
ing of  a  layer  of  cells  continuous  with  the  superficial  layer  of  the  cartilage-cells  and 
secreting  a  viscid  fluid,  the  synovia,  which  lubricates  the  joint ;  and  the  outer  part, 
which  becomes  a  fibrous  bag  called  the  capsular  ligament.  The  latter,  in  its  simplest 
form,  consists  of  only  enough  fibrous  tissue  to  support  the  synovial  membrane.  The 
capsular  ligament  is  strengthened  by  accessory  ligaments  developing  in  or  around  it, 
the  arrangement  of  which  depends  on  the  needs  of  the  joint.     During  development, 


STRUCTURE    OF   JOINTS.  109 

independent  of  the  influence  of  motility  or  of  muscular  action,  the  articular  ends  of 
the  bones  assume  definite  shapes  such  as  will  allow  the  motion  peculiar  to  that  joint, 
and  (barring  the  frequent  want  of  perfect  coaptation)  no  other.  The  common  char- 
acteristics of  true  joints  are  articular  surfaces  covered  by  hyaline  cartilage,  so 
shaped  as  to  determine  the  nature  of  the  movement,  enclosed  by  a  capsule  lined  with 
a  synovial  membrane.  The  articular  surfaces  are  not  necessarily  formed  wholly  of 
bone,  since  very  often  increased  concavity  is  secured  by  the  addition  of  a  lip  of  fibro- 
cartilage  to  the  margin  of  the  bone  ;  in  other  cases  ligaments  coated  with  carti- 
lage complete  a  socket  ;  or  again,  disks  of  fibro-cartilage  loosely  attached  to  the 
periphery  may  project  into,  a  joint  and  partially  subdivide  it,  following  one  bone  in 
certain  movements  and  the  other  in  others. 

Compound  joints  result  from  the  persistence  and  differentiation  of  a  portion  of 
the  tissue  uniting  the  ends  of  the  embryonal  bones,  into  a  partition  which,  in  the 
complete  compound  joint,  separates  the  two  synovial  cavities  developed,  one  on 
either  side  of  the  septum.  The  tissue  between  the  bones  becomes  a  fibro-cartilagi- 
nous  disk,1  which  partially  or  completely  subdivides  the  cavity.  In  such  a  joint, 
when  typical,  there  are  two  ends  of  bone  covered  with  articular  cartilage,  separated 


Fig.  135. 


Diagrams  illustrating  formation  of  joints.  A,  bones  are  united  by  young  connective  tissue;  B,  appearance  of 
joint-cavity;  C,  differentiation  of  joint-cavity  and  capsule;  D,  development  of  two  joint-cavities  separated  by 
fibrous  septum,  resulting  in  a  compound  joint. 

by  a  fibro-cartilaginous  disk  or  meniscus,  and  two  distinct  synovial  membranes.  The 
movements  are,  however,  still  determined  to  a  considerable  extent  by  the  shape  of 
the  bones,  so  that  these  articulations  may  be  classed  as  true  joints.  The  fibro- 
cartilaginous meniscus  may  be  replaced  by  a  row  of  bones  as  in  the  wrist. 

Structure  of  True  Joints. — The  opposed  ends  of  the  bones,  and  sometimes 
other  tissues,  are  coated  with  hyaline  articular  cartilage,  which  gives  a  greater 
smoothness  to  the  articulating  surfaces  than  is  found  on  the  macerated  bones. 
Though  following  in  the  main  the  bony  contours,  the  cartilage  does  not  do  so  accu- 
rately ;  details  are  found  on  the  cartilage  that  are  obscure  on  the  bones.  It  dimin- 
ishes the  force  of  shocks.  Although,  as  already  stated,  the  shape  of  the  articular  ends 
determines  the  nature  of  the  motion,  it  is  important  to  recognize  that,  as  in  the  case 
of  saddle-joints,  the  opposed  surfaces  are  not  so  accurately  in  apposition  that  irreg- 
ular movements  cannot  and  do  not  occur.  Failure  to  appreciate  this  fact  has  given 
rise  to  much  difficulty  in  accounting  for  motions  that  undoubtedly  take  place,  but 
which,  according  to  the  mathematical  conception  of  the  joint,  are  impossible. 
Further,  the  range  of  individual  variation  is  great  ;  just  as  a  man  may  have  a  long 
or  a  short  head,  so  any  of  the  articular  ends  of  his  bones  may  depart  considerably 
from  the  average  proportions.      It  is  even  possible  in  some  of  the  smaller  joints- that 


HUMAN   ANATOMY. 


the  articular  surface  of  a  certain  bone  may  be  plane,  convex,  or  concave  in  different 
persons. 

The  capsule. — Every  joint,  with  possibly  some  exceptions  in  the  carpus  and 
the  tarsus,  is  enclosed  by  a  capsule,1  or  capsular  ligament,  which  arises  from  the  peri- 
osteum near  the  borders  of  the  articular  cartilage  and  surrounds  the  joint.  This 
envelope  consists  of  a  membrane,  often  containing  fat  within  its  meshes,  composed 
of  two  layers,  the  inner  delicate  synovial  membrane  and  the  external  fibrous  layer. 
The  latter,  while  in  some  places  very  thin,  is  usually  strengthened  by  the  incorpora- 
tion of  fibrous  bands  which,  from  their  position,  are  known  as  lateral,  anterior,  or 
posterior  ligaments.  These  bands  are  of  strong,  non-elastic  fibrous  tissue  which 
under  ordinary  circumstances  do  not  admit  of  stretching.  The  strength  and 
security  of  the  joint  are  often  materially  increased  through  thickenings  of  fascia;  and 
expansion  of  tendons  which  blend  with  the  underlying  capsule.  The  capsule  must 
be  large  enough  to  allow  the  characteristic  movements  of  the  joint  ;  consequently, 
when  the  bone  is  moved  in  any  particular  direction  that  side  of  the  capsule  is  relaxed 
and  thrown  into  folds.  These  folds  are  drawn  out  of  the  way  either  by  small  special 
muscles  situated  beneath  those  causing  the  chief  movement  or  by  fibres  from  the 

deeper  surfaces  of  these  latter  muscles.  In 
the  joints  of  the  arches  of  the  vertebrae,  there 
being  no  muscles  inside  the  spinal  canal,  a  dif- 
ferent arrangement  exists  for  the  inner  side  of 
the  capsule,  elastic  tissue  there  taking  the 
place  of  muscle.  The  relation  of  the  insertion 
of  the  capsule  to  the  line  of  the  epiphysis  is 
important.  Although  this  point  is  fully  con- 
sidered in  the  description  of  the  individual 
joints,  it  may  be  here  stated  that,  as  a  rule,  in 
the  long  bones,  the  capsule  arises  very  near 
the  line  of  the  epiphysis. 

The  synovial  membrane  which  lines 
the  interior  of  the  capsule  and  other  portions 
of  the  joint,  except  the  surfaces  of  the  articular 
cartilages,  consists  of  a  delicate  connective- 
tissue  sheet,  containing  many  branched  and 
flattened  connective-tissue  cells.  The  latter, 
where  numerous,  as  is  the  case  except  at  points 
subjected  to  considerable  pressure,  are  ar- 
ranged on  the  free  surface  of  the  synovial  mem- 
brane as  a  more  or  less  continuous  layer,  often 
spoken  of  as  the  endothelium  of  the  synovial 
sac.  Since  in  many  places  the  layer  of  connective-tissue  elements  is  imperfect  and 
the  component  cells  retain  their  stellate  form,  the  cellular  investment  of  the  joint- 
cavity  is  at  best  endothelioid,  suggesting,  rather  than  constituting,  an  endothelium. 
The  synovial  membrane  is  in  certain  places  pushed  inward  by  accumulations  of  fat 
of  definite  shape  between  it  and  the  capsule.  It  is  also  prolonged,  as  the  synovial 
fringes, 2  into  any  space  that  might  otherwise  be  left  vacant  in  the  various  movements. 
They  are  alternately  drawn  in  or  thrust  out,  according  to  circumstances.  Some- 
times pieces  of  them,  or  of  fibro-cartilage,  become  detached  in  the  joint,  giving  rise 
to  much  trouble. 

The  cavity  which  is  found  when  a  joint  is  opened  on  the  cadaver,  with  the 
tissues  dead  and  relaxed,  easily  suggests  a  false  impression.  It  is  to  be  remembered 
that  the  synovial  fluid  normally  is  present  in  quantity  little  more  than  sufficient  to 
lubricate  the  joint,  and  that  in  life  all  the  parts  are  strongly  pressed  together  so  that 
no  true  cavity  exists.      This  is  well  shown  by  frozen  sections. 

Certain  so-called  intra- articular  ligaments,  as  the  ligamentum  teres  of  the  hip, 
or  the  crucial  ligaments  of  the  knee-joint,  are  found  in  the  adult,  roughly  speaking, 
inside  the  joint.  The  sketch  of  development  given  above  shows  that  they  cannot 
be  truly  within  the  articular  cavity.  In  fact,  either  they  wander  in  from  the  capsule, 
carrying1  with  them  a  reflection  of  synovial  membrane,  or  they  are  the  remnants  of 

1  Capsula  articutaris .     2  Plicae  synoviales. 


Capsule 

Synovial  membrane 

Articular  cartilage 

Joint-cavity 


Epiphyseal  bone. 


Diagram  showing  the  parts  of  a  typical  joint. 


BURS^E.  in 

the  capsules  separating  two  distinct  joints  which  have  broken  down  so  as  to  make  a 
common  articular  cavity.  Such  ligaments  retain  their  synovial  covering  and  really 
lie  without  the  joint-cavity. 

Vessels  and  Nerves. — Important  arterial  anastomoses  surround  all  the  larger 
joints  ;  from  the  larger  vessels  small  branches  pass  inward  to  the  ends  of  the  bones, 
to  the  periphery  of  the  articular  cartilages,  and  to  the  capsule.  The  margins  of  the 
cartilages  are  surrounded  by  vascular  loops  ;  the  articulating  surfaces  .are,  however, 
free  from  blood-vessels.  The  synovial  membrane  is  usually  well  supplied  with 
minute  branches,  a  rich  net-work  being  described  at  the  bases  of  the  synovial  fringes. 
The  veins  form  strong  plexuses. 

Lymphatics  are  found  well  developed  directly  beneath  the  inner  surface  of  the 
synovial  membrane  ;  while  it  is  certain  that  they  absorb  from  the  joint,  direct  open- 
ings into  the  articular  cavity  have  not  been  demonstrated. 

Nerves,  presumably  sensory  and  vasomotor,  end  in  the  tissues  around  the  syno- 
vial membrane.  In  addition  to  the  Pacinian  bodies,  which  are  sometimes  very 
numerous,  Krause  has  described  special  articular  end-bulbs  outside  the  synovial 
membrane  surrounding  the  finger-joints  in  man. 


Fig.  137. 


Free  surface  of 
articular  car- 
tilage 


Marrow-cavity 


Jnion  of  carti- 
age  and  syno- 
vial membrane 


Section  through  margin  of  joint,  showing  articular  cartilage  and  capsule.     X  135. 


Bursae '  are  sacs  filled  with  fluid  found  in  various  places  where  friction  occurs 
between  different  layers  or  structures.  They  are  sometimes  divided  into  synovial 
and  mucous  bursae.  These  varieties  are  distinct  in  typical  instances,  but,  since  the 
one  passes  insensibly  into  the  other,  it  is  doubtful  whether  this  subdivision  is  war- 
ranted. Some  bursae,  especially  those  around  the  tendons  of  the  fingers,  have  a 
true  synovial  lining  reflected  over  the  tendons,  and  are  surrounded  by  strong  fibrous 
sheaths  known  as  the  thecte  synoviales.2  Other  bursae  are  placed  as  capsules  around 
a  cartilage-coated  facet  over  which  a  tendon  plays.  Both  the  vaginal  and  capsular 
varieties  may  be  classed  as  synovial  bursae.  Representatives  of  the  mucous  bursae 
are  those  within  the  subcutaneous  tissue  where  the  skin  is  exposed  to  friction,  as  at 
the  elbow  and  the  knee.  These  bursae  seem  little  more  than  exaggerations  of  the 
spaces  between  layers  of  areolar  tissue.  The  same  may  be  said  of  some  of  those 
among  the  muscles.  The  mucous  bursat  are  provided  with  more  or  less  of  a  cellu- 
lar lining,  but  the  latter  is  less  perfect  than  in  the  synovial  class.  A  bursa  may  be 
simple  or  composed  of  several  cavities  communicating  more  or  less  freely.  They 
often  communicate  with  joints.  Their  number  is  uncertain.  Many,  perhaps  most, 
are   present  at  birth,   but  new  ones   may   appear  in  situations   exposed  in  certain 


ii2  HUMAN    ANATOMY. 

individuals  to  uncommon  pressure  or  friction,  and,  under  these  circumstances,  the 
ones  usually  present  may  be  enormously  enlarged. 

Modes  of  Fixation  in  Joints. — Ligaments,  muscles,  atmospheric  pressure, 
and  cohesion  are  the  agents  for  fixation. 

Ligaments. — A  capsular  ligament,  pure  and  simple,  has  little  retaining 
strength.  The  accessory  ligaments,  on  the  contrary,  have  great  influence.  Their 
arrangement  differs  with  the  nature  of  the  joint.  Thus,  a  ball-and-socket  joint  has 
thickenings  at  such  parts  of  the  capsule  as  the  particular  needs  of  that  joint  require. 
A  hinge-joint  implies  strong  lateral  ligaments  ;  a  rotary  joint,  some  kind  of  a  retain- 
ing-band  that  shall  not  arrest  motion.  Sometimes  certain  ligaments  are  tense,  or 
nearly  so,  in  every  position  of  the  joint,  as  the  lateral  ligaments  of  a  hinge-joint. 
Often  a  ligament  is  tense  only  when  a  joint  is  in  a  particular  position,  as  the  ilio- 
femoral ligament  of  the  hip  when  the  thigh  is  extended.  A  strong  ligament  like 
the  one  just  mentioned  is,  when  tense,  the  greatest  protection  against  displace- 
ment. 

Muscles. — The  action  of  the  muscles  is  of  great  importance  in  maintaining 
the  joints  in  position,  in  certain  instances  being  the  most  efficient  agency.  The  con- 
stant pull  of  the  muscles  keeps  the  more  movable  bone  closely  applied  to  the  more 
fixed  in  all  positions.  Muscles  which  are  nowhere  in  contact  with  the  joint  may 
exercise  this  function.  The  tendons  of  muscles  sometimes  act  as  ligaments,  which 
differ  from  the  ordinary  ligamentous  bands  in  that  they  may  be  made  tense  or 
relaxed  by  muscular  action.  Sometimes  they  are  intimately  connected  with  the 
capsule,  at  other  times  distinct  from  it.  Some  muscles,  whose  tendons  cross  several 
joints,  exercise,  by  their  tonicity,  an  influence  on  them  all.  Thus,  the  peroneus 
longus  is  essential  to  the  maintenance  of  the  transverse  arch  of  the  foot.  Certain 
muscles  passing  over  more  than  one  joint  exert  a  ligamentous  action  on  one  joint 
determined  by  the  position  of  the  other.  This,  however,  is  more  properly  dis- 
cussed in  connection  with  the  action  of  muscles. 

Atmospheric  Pressure. — Much  has  been  written  about  the  action  of  this 
agency  in  holding  joints  in  place.  The  atmosphere  exerts  a  certain  pressure  on  all 
bodies,  animate  or  inanimate,  and  thus  tends  to  compress  them.  The  joints,  as 
parts  of  the  body,  are  subject  to  this  general  influence.  It  is  by  no  means  very  effi- 
cacious. The  shoulder-joint  has  a  capsule  long  enough  to  allow  very  free  motion, 
and  consequently  too  long  to  hold  the  humerus  in  place.  This  is  done  chiefly  bv 
the  muscles.  When  these  are  paralyzed  the  arm  falls  out  of  place,  atmospheric 
pressure  being  inadequate  to  resist  the  weight.  The  most  important  action  of 
atmospheric  pressure  is  to  keep  the  soft  parts  closely  applied  to  the  bones. 

Cohesion  is  the  action  of  the  viscid  synovial  fluid  which  tends  to  hold  the 
surfaces  together.  It  is  very  feeble,  but  probably  has  an  appreciable  influence  in 
the  smaller  joints. 

Limitation  of  Motion. — The  shape  of  the  joint  determines  the  nature  of  the 
movement  ;  its  range  depends  in  part  on  other  factors,  such  as  the  tension  of  liga- 
ments or  of  the  tendons  of  muscles  and  the  resistance  of  the  soft  parts. 

Motion  in  True  Joints. — It  is  easy  to  conceive  that  an  upright  rod  on  the 

highest  point  of  rather  less  than  half  a  sphere  may 

Fig.  138.  slide  to  the  periphery  along  an  indefinite  number  of 

rotation^  *nc  lines.      This  is  angular  motion.      The  rod  on  reach- 

.-■-"""    T      ""-4^>  ing  the  periphery,  or  at  any  point  on  the  way,  may 

,.■•  N-/"°>         travel  round  in  a  circle  describing  the  surface  of  a 

c1pcum  ;  Ducno/v       ''•'%      cone.      This  is  circumduction.      Finally,  without  any 
/.„  OC/^^^^^X/^ "'  ^.  change  of  position,  the  rod  may  revolve  on  its  own 

C^-^y  i         \  ^^^3      axis.      This  is  rotation. 

■^Zrhzr- \^--~y^**^  Changes  of  Position  of  Parts  of  the  Body. 

_.  .„    .    ,.      .._      . , .  .     .      — Assuming  that  the  palms  are  looking:  forward,  an- 

Diagram  illustrating  different  kinds  of  .  .  &        ,        ..      ,  f  P  , 

motion.  gular  motion  01  a  limb,  or  of  a  part  of  one,  towards 

the  median  plane  of  the  body  is  called  adduction  ;  the 
opposite  movement,  abduction.  A  motion  bringing  the  distal  end  of  a  limb  bone 
nearer  to  the  head  is  called  flexion  ;  the  opposite  movement,  extension.  The  move- 
ments of  the  ankle  and  the  foot,  however,  present  a  difficulty,  although  the  above 


VARIETIES    OE   TRUE   JOINTS.  113 

nomenclature  is  generally  accepted,  since  the  digital  extensor  muscles  flex  and  the 
flexors  extend.  It  is  best  with  reference  to  the  ankle-joint  to  speak  of  plantar 
flexion  and  dorsal  flexion.  Pronation  in  the  arm  is  turning  the  front  of  a  limb 
downward  ;  supination,  the  converse.  Thus,  when  the  palm  rests  upon  a  table  the 
arm  is  pronated  ;  when  the  back  of  the  hand  rests  upon  the  same  support  the  arm 
is  supinated.  Reference  to  the  skeleton  during  these  movements  will  show  that  pro- 
nation is  associated  with  crossing  of  the  bones  of  the  forearm,  while  during  supina- 
tion they  are  parallel.  These  terms  should  not  be  applied  to  motions  of  the  leg. 
Rotation  is  inward  or  outward,  according  as  it  is  towards  or  away  from  the  median 
line  of  the  body. 

Varieties  of  True  Joints. — The  following  are  the  chief  kinds  of  true  joints, 
the  nature  of  the  motion  being  determined  by  the  articular  surfaces  : 

Arthrodia,1  a  glidi?ig  joint  permitting  merely  a  sliding  between  two  nearly 
plane  surfaces,  as  between  the  articular  processes  of  the  vertebrae. 

Enarthrosis,"  a  ball-and-socket  joint  permitting  angular  motion  in  any  direc- 
tion, circumduction  and  rotation.  The  shoulder-  and  hip-joints  are  conspicuous 
examples. 

Condylarthrosis,:1  an  egg-shaped  joint  permitting  angular  motions  more  freely 
on  the  long  axis  than  on  the  short  one,  circumduction  but  (theoretically,  at  least) 
no  rotation,  as  in  the  radio-carpal  articulations.  The  imaginary  axes  for  the  angular 
motions  lie  in  the  convex  bone. 

The  Saddle-Joint,*  is  a  modification  of  the  above,  the  end  of  one  bone  being 
convex  in  one  plane  and  concave  in  another,  at  right  angles  to  the  first,  while  the 
other  bone  is  the  converse  ;  thus  in  one  plane  one  bone  is  the  receiver  and  in  the 
other  the  received.  The  articulation  of  the  trapezium  with  the  first  metacarpel  bone 
is  an  example.  The  motions  in  such  joints  are  precisely  the  same  as  those  of 
the  preceding  form.  The  two  imaginary  axes  are,  however,  on  opposite  sides  of  the 
joint,  each  being  at  right  angles  to  the  convex  plane  of  its  own  bone.  It  is  clear 
that  if  the  reciprocal  curves  of  the  two  bones  of  a  saddle-joint  coincide,  and  that  if 
they  fit  closely,  rotation  is  out  of  the  question  ;  but,  in  point  of  fact,  that  is  not  the 
case,  for  there  is  no  very  accurate  agreement  of  the  surfaces,  and  the  contained 
curve  is  smaller  than  the  containing,   so  that  a  certain  amount  of  rotation  is  possible.5 

Ginglymus,6  a  hinge-joint  permitting  motion  only  on  a  single  axis  approxi- 
mately transverse  to  the  long  axis  of  the  bone,  consequently  the  moving  bone  keeps 
in  one  plane.  The  ankle-joint  is  an  example.  The  inclination  of  the  transverse 
axis  may  vary,  and  one  end  of  the  joint  be  larger  than  the  other.  If  the  course  of 
the  revolving  bone  is  that  of  a  spiral  around  the  transverse  cylinder  the  articulation 
constiutes  a  screw-joint,''  as  the  humero-ulnar  articulation. 

Trochoides,8  a  pivot-joint  permitting  motion  only  on  one  axis  coincident  with 
at  least  a  part  of  the  long  axis  of  the  bone, — namely,  rotation,  as  in  the  atlanto-axial 
articulation.  Should  a  part  of  the  bone  be  so  bent  as  to  lie  outside  of  the  axis,  as 
in  the  radius,  this  part  undoubtedly  changes  position  ;  nevertheless,  there  is  merely 
rotation,  for  the  change  of  position  is  accidental,  depending  on  the  shape  of  the 
bone,  not  on  the  nature  of  the  motion. 

Certain  complicated  joints  may  combine  several  of  the  above  forms. 
5Ren£du  Bois-Reymond.     Archiv  fur  Anat.  u.  Phys.,  Phys.  Abtheil.,  1S95. 

3  Articulatio  ellipsoidea.      i  Articulatio  sellaris.      G  Ginglymus.      7  Articulatio  cochlearis. 


THE  SPINAL  COLUMN. 

The  spinal  column  is  the  central  part  of  the  skeleton.  It  supports  the  head, 
bears  the  ribs,  thus  indirectly  supporting  the  arms,  and  encloses  the  spinal  cord.  It 
gives  origin  to  many  muscles,  some  passing  between  different  parts  of  the  spine, 
others  connecting  it  with  the  body.  These  purposes  demand  great  strength  and 
flexibility.  The  spine  is  composed  of  many  pieces  united  by  tough  fibro-cartilagi- 
nous  disks,  by  which  the  force  of  shocks  is  broken  and  the  great  range  of  move- 
ment is  distributed  among  many  joints.  It  is  convex  behind  in  the  regions  of  the 
thorax  and  pelvis,  so  as  to  enlarge  those  cavities,  and  has  forward  convexities  in  the 
neck  and  loins.  The  numerous  prominences  which  it  presents  serve  for  the  support 
of  the  ribs,  the  attachment  of  muscles,  and  the  interlocking  of  the  various  pieces. 
The  spinal  column  is  firmly  fixed  near  the  lower  end  between  the  bones  of  the  pelvis. 

The  bones  composing  this  column  are  called  vertebrce,  of  which  in  the  adult 
there  are  thirty-three  or  thirty-four  in  all.     They  are  divided  into  five  groups.     The 


Fig.  139. 


Spinous  process 


Transverse  proo 
Superior  articular  proce: 


Demi-facet  for  head  of  rib' 


Sixth  thoracic  vertebra  f 


first  seven  are  the  cervical ;  the  next  twelve,  which  bear  ribs,  are  the  thoracic ;  the 
next  five  are  the  lumbar,  making  twenty-four  above  the  pelvis.  These  are  known 
as  the  presacral  vertebrae.  The  remainder  are  in  the  adult  united  into  two  bones, 
the  first  five  forming  the  sacrum,  the  last  four  or  five  the  coccyx.  As  many  as 
thirty-eight  are  seen  in  the  young  embryo,  but  some  disappear  or  are  fused. 

With  the  exception  of  the  first  two,  the  atlas  and  the  axis,  which  require  a 
separate  description  (page  119),  the  vertebras  above  the  sacrum  present  the  following 
features,  which  are  common  to  all,  but  which  are  modified  in  the  different  regions  : 
(1)  a  body1  or  centrum  ;  (2)  a  pedicle11  springing  from  the  back  of  the  body  on  either 
side,  supporting  (3)  the  lamina,3  a  plate  which  meets  its  fellow  in  the  middle  line  to 
form  an  arch  bounding  the  spinal  or  vertebral  foramen*  for  the  spinal  cord.  Each 
vertebra  gives  origin  to  several  processes. — namely,  (4)  a  spinous  process, s  springing 
from  the  point  of  union  of  the  laminae  ;  (5)  a  transverse  process  on  each  side,  pro- 
jecting outward  from  the  junction  of  the  pedicle  and  lamina  ;   (6)  two  articulating 


1  Corpus.     -  Radh 

114 


i  vertebrae.     s  Arcus 


3  Processus  spinosus.0  Processus  transve 


THORACIC   VERTEBRAE. 


i'5 


Articular  facet 
on  transverse 
process 


Sixth  thoracic  vertebra  from  the  side. 


processes1  on  each  side,  one  above  and  one  below  the  lamina,  forming  true  joints 
with  the  opposed  processes  of  the  neighboring  vertebrse  ;  (7)  a  rib  or  costal  element, 
which  in  the  thoracic  region  is  a  separate  bone,  in  the  cervical  region  is  a  part  of  the 
vertebra,  and  in  the  lumbar 

region  mingles  with  the  trans-  FlG-  I4°' 

verse  process.  The  costal  ele- 
ment is  also  represented  in 
the  sacrum. 

Thoracic  Vertebrse. 
— A  vertebra  from  the  middle 
of  the  thoracic  region  is  de- 
scribed first  as  intermediate  in 
several  respects  to  the  others. 
The  body  is  but  a  little 
broader  transversely  than 
from  before  backward.  It  is 
a  little  deeper  behind  than  in 
front,  thereby  helping  to  form 
the  curve  of  the  spine.  The 
upper  and  lower  borders  pro- 
ject a  little  anteriorly.  The 
upper  and  lower  surfaces,  as 
in  all  the  vertebrae,  are  rough 
where  the  intervertebral  disks 
join  them.  The  posterior 
surface  is  concave  from  side 
to  side,  and  presents  in  the 
middle  one  or  two  foramina 
for  the  escape  of  the  veins.  At  the  back  of  the  side  of  the  body  there  is  half  an 
articular  facet  both  above  and  below,  which,  with  the  intervening  disk,  forms  an  oval, 
shallow  socket  for  the  head  of  the  rib  belonging  to  the  lower  vertebra. 

The  spinal  foramen,  en- 
closed by  the  arch,  is  circular. 

The  pedicles,  which  are  much 
deeper  than  thick,  arise  from  the 
upper  half  of  the  body.  The  supe- 
rior border  rises  gradually  to  the 
articular  process.  The  inferior  bor- 
der is  concave,  forming  the  top  of 
the  notch,'1  which,  when  the  succeed- 
ing vertebra  is  in  place,  forms  the 
top  of  the  intervertebral  forainen? 
which  is  wholly  behind  the  lower 
half  of  the  body. 

The  laminee  are  broad,  each 
reaching  to  the  level  of  those  of  the 
next  vertebra. 

The  spinous  process  is  long, 
and  points  strongly  downward,  over- 
lapping the  one  below.  It  has  a 
narrow  under  surface  which  is 
grooved,  and  two  lateral  ones  meet- 
ing above  in  a  ridge  continued  from 
the  laminae.  This  arrangement  of 
the  lamina?  and  spines  completely 
closes  the  cavity  of  the  spinal  canal. 
The  spinous  processes  are  slightly  enlarged  at  the  end  for  the  supraspinous  liga- 
ment and  muscles. 

The  transverse  processes  are  strong,  having  to  support  the  ribs.      1  hey  pro- 


Spinous  process 


Sixth  thoracic  vertebra  from  behind. 


n6 


HUMAN   ANATOMY. 


ject  outward  and  backward,  and  enlarge  at  the  tip,  which  anteriorly  presents  a  con- 
cave articular  surface  for  the  tubercle  of  the  rib,  and  is  rough  behind  for  muscles. 

The  articular  surfaces  are  in  two  pairs  above  and  below,  each  pair  facing  in 
opposite  directions,  so  that  the  lower  ones  of  one  vertebra  meet  the  upper  ones  of 


Fig.  142. 


Spinous  process 


Inferior  articular  process 

Superior  articular  process 

Transverse  foramen 
Transverse  process 


Posterior  limb  of  transverse 
process 


Posterior  tubercle 


Body 
Fourth  cervical  vertebra  fr> 


Costal  element 
Anterior  tubercle 

Anterior  limb  of  transverse  process 
m  above. 


the  next.  Each  presents  a  smooth,  roughly  oval  articular  surface.  The  superior 
ones  face  backward,  a  little  outward,  and  a  very  little  upward  ;  the  inferior,  con- 
versely, look  forward,  inward,  and  slightly  downward. 


Groove  for  spinal  nerve 


Fig.  143. 


Superior  articular  process 


Anterior  tubercle 
Posterior  tubercle 


1  vertebra  from  in  front. 


-A  typical  cervical  vertebra  is  much  smaller  than  the 


Cervical  Vertebrae 

thoracic. 

The  body  is  decidedly  longer  from  side  to  side  than  from  before  backward. 

The  upper  surface  is  raised  at  the  sides 
Fig.  144. 

Superior  articular  process  and  facet 


so  as  to  embrace  the  body  next  above, 
and  has  its  front  border  rounded  for  the 
latter  to  descend  over  it  ;  for  this  pur- 
pose the  lower  anterior  border  is  pro- 
longed downward.  The  height  of  the 
body  is  about  the  same  before  and  be- 
hind. 

The  spinal  foramen  is  triangular, 
with  the  greatest  diameter  transverse. 

The  pedicles  are  short  and  light, 
and  extend  backward  and  outward  from 
the  body.      The  notches  above  and  be- 
low them  are  about  equal. 
The  intervertebral  foramen  is  opposite  the  intervertebral  disk,  and  a  part 
of  the  bodies  of  two  vertebrae. 


Inferior  articular  pro- 
cess and  facet 

Intervertebral 
notch 


Groove  for  spinal 


Fourth  cervical  vertebra  from  the  side. 


LUMBAR    VERTEBRA. 


117 


The  laminae  are  smooth  and  do  not  quite  meet  those  of  the  next  vertebra, 
unless  the  head  be  bent  backward. 

The  spinous  process  projects  backward  and  a  little  downward.  It  is  short 
and  forked  at  the  end,  very  often  unevenly. 

The  transverse  processes  are  often  described  as  double.  The  posterior  limb, 
which  is  the  true  transverse  process,  projects  outward  and  somewhat  forward  from 
the  junction  of  the  pedicle  and  lamina,  and  ends  in  a  flattened,  nearly  vertical  pro- 
jection, the  posterior  transverse  tubercle.  The  anterior  limb,  a  vertical  plate  spring- 
ing from  the  side  of  the  body  and  extending  outward,  ends  in  the  anterior  h-ansverse 
tubercle.  This  limb  is  the  shorter  of  the  two  and  its  tubercle  the  larger.  The  limbs 
are  connected  by  a  concave  plate  or  bone,  slanting  slightly  outward,  which  forms 
the  floor  of  a  gutter '  in  which  the  spinal  nerve  lies,  and  which  represents  the  costal 
element.  A  round  hole,  the  transverse  foramen,  for  the  vertebral  artery  and  veins, 
lies  internal  to  this  plate  ;  the  artery  usually  does  not  pass  through  the  foramen  of 
the  seventh  vertebra.     Since  the  scalenus  anticus  muscle  springs  from  the  anterior 


Superior  articular  facet 
Mammillary  pro 


Third  lumbar  vertebra  from  above. 


tubercles  and  the  scalenus  medius  from  the  posterior  ones,  on  leaving  the  spine  the 
spinal  nerves  pass  between  these  muscles. 

The  articular  processes  are  placed  at  the  outer  ends  of  the  lamina?  ;  the 
upper  face  upward  and  backward,  the  lower  forward  and  downward. 

Lumbar  Vertebrae. — A  typical  lumbar  vertebra  is  very  much  larger  than  the 
others. 

The  body  is  broad  from  side  to  side,  the  upper  and  lower  borders  projecting 
especially  at  the  sides.  The  posterior  surface  is  slightly  concave  and  presents  two 
large  venous  openings. 

The  spinal  foramen  is  three-sided,  with  a  transverse  diameter  but  slightly 
exceeding  the  antero-posterior. 

The  pedicles  are  short  and  strong,  diverging  only  slightly.  They  are  very 
nearly  on  a  level  above  with  the  top  of  the  body,  so  that  there  is  a  small  notch  above 
and  a  large  one  below. 

The  laminae  are  broad  at  the  sides,  but  less  so  near  the  mid-line,  so  that  in  this 


n8 


HUMAN    ANATOMY. 


region  there  is  a  large  opening  into  the  spinal  canal.  A  considerable  part  of  the  arch 
is  lower  than  the  body. 

The  spinous  process  is  a  flat  projection  extending  nearly  straight  backward, 
with  two  lateral  surfaces  and  a  superior,  inferior,  and  posterior  border.  The  last  is 
rough  and  thickened  below,  with  occasionally  a  tendency  to  become  bifid. 

The  transverse  processes,  which  are  solely  for  muscular  attachments,  and 


Fig.  146. 


Superior  articular  process. 


Mammillary  process 
Transverse  process 


Accessory  process 
-Inferior  articular  process  and  facet 


Third  lumbar  vertebra  from  the  side. 


therefore   not  heavy,   project  outward   and  somewhat  backward.      They  are  thin, 
having  an  anterior  and  a  posterior  surface  and  a  blunt  end. 

The  articular  processes  are  large,  very  nearly  vertical,  and  curved.  The 
superior,  facing  somewhat  backward  but  chiefly  inward,  are  concave  and  embrace 
the  inferior  ones  of  the  vertebra  above,  which  are  convex,  and  face  in  the  opposite 
direction. 


Superior  articular  process  and  facet 


llary  process 


Accessory  process 


Inferior  articular  process 


Spinous  process         Lamina 
Third  lumbar  vertebra  from  behind  and  the  side. 


The  mammillary  processes  form  on  either  side  a  rounded  lateral  projection 
on  the  posterior  border  of  the  superior  articular  process.  Additional  tubercles,  the 
accessory  processes,  appear  as  inconspicuous  elevations  at  the  junction  of  the 
posterior  border  of  the  transverse  with  the  superior  articular  processes.  The  details 
and  the  morphological  significance  of  the  mammillary  and  the  accessory  processes 
are  discussed  later  (page  123). 


PECULIAR    VERTEBRyE. 


119 


The  chief  points  of  difference  between  typical  vertebrae  of  the  three  presacral 
groups  may  be  tabulated  as  follows  : 


Spinal  Foramen. 

Pedicles. 
Laminae. 


Transverse  Pro- 
cesses. 


Superior  Articu- 
lar Surfaces. 


Cervical. 

1.  Broad. 

2.  Upper  surface  with 
raised  sides  and 
rounded  anterior  bor- 
der. 

3.  No  facets. 


Lumbar. 


Diameters  nearly  equal;     Broad. 

concave  behind. 
Plane.  Plane. 


Costal  semifacets. 


Triangular,  with    great-     Nearly  circular, 
est     diameter     trans- 
verse. 


No  facets. 

Triangular,  with  diam- 
eters nearly  equal. 


Notches  above  and  be- 
low nearly  equal. 

Narrow,  with  spaces  be- 
tween. 


Double  foramen  at  root ; 
two  tubercles. 

Nearly  plane  ;   face  up- 
ward and  backward. 


Rising  from  top  of  body;  Small    notch     above, 

great  notch  below.  great  one  below. 

Broad;    no   spaces    be-  Extending  downward; 

tween.  large     spaces     be- 
tween. 

Strong,    with     articular  Slender, 
facet. 

Plane,  vertical ;    face  Concave,  vertical  ; 

nearly  backward.  face  chiefly  inward. 


PECULIAR   VERTEBRAE. 

Certain  vertebrae  differ  more  or  less  markedly  from  the  type  of  their  respective 
groups  ;  in  some  cases,  as  the  upper  two  cervical  vertebrae,  these  variations  result  in 
conspicuous  modifications  ;  in  others,  as  the  lower  thoracic,  the  peculiarities  are  less 
pronounced.     Although  the  most  noteworthy  differences  are  here  given,  the  reader 

Fig.  148. 

Posterior  tubercle 


Groove  for  vertebral  artery 
1.,.,,     iass-7=g^iP^V       bP'naI  '°ramen  V^-^^Superior  articular  facet 


Transverse  foramen 


Facet  for  odontoid  process  of 


Anterior  arch 


Anterior  tubercle 
The  atlas  from  above. 


is  referred  to  the  discussion  of  the  gradual  changes  which  occur  in  passing  from  one 
region  to  the  other  (page  122)  for  a  more  complete  account  of  the  modifications  to 
be  observed. 

The  first  and  second  cervical  vertebrae,  known  as  the  atlas  and  axis,  consti- 
tute a  special  apparatus  for  the  security  and  movements  of  the  head.      The  key  to 


HUMAN   ANATOMY. 


the  arrangement  is  that  the  part  which  in  the  ordinary  process  of  development 
should  become  the  body  of  the  atlas  is  instead  fused  with  the  body  of  the  axis. 

The  atlas,  having  no  body,  consists  of  two  lateral  masses,  connected  by  a  short 
anterior  arch  and  a  long  posterior  one.  The  lateral  masses  present  the  articular 
facets  on  their  lower  and  upper  surfaces.  The  inferior  look  downward  and  slightly 
inward,  and  are  very  slightly  concave  from  before  backward.  The  superior  facets 
are  oval  concavities  the  backs  of  which  are  strongly  raised  from  the  surface.  Their 
long  axis  runs  forward  and  inward,  the  outer  wall  being  decidedly  higher  than  the 
inner.  The  articular  facet  narrows  at  the  middle,  and  is  often  marked  by  a  trans- 
verse ridge  at  this  point  ;  rarely  it  is  divided  into  two  parts.  The  articular  surfaces 
of  the  two  sides  sometimes  very  nearly  correspond  with  parts  of  the  surface  of  a 
single  imaginary  sphere. 

Their  variation  in  all  respects  is  great.  Thus,  Macalister 1  finds  in  one  hundred 
bones  that  the  distance  between  the  front  ends  of  the  two  facets  varies  from  ten  to 
twenty  millimetres,  being  usually  from  fifteen  to  twenty  millimetres,  and  that  the 
hind  ends  are  from  thirty-two  to  fifty  millimetres  apart,  the  greater  number  being 
separated  from  thirty-five  to  forty  millimetres.      The  angle  formed  by  the  intersec- 

Fig.  149. 

Posterior  tubercle 


Posterior  arch 


Transverse  foramen 


Inferior  articular  facet 


Position  of  transverse  ligament  (dotted  lines) 


Facet  for  odontoid  process  Anterior  tubercle 

The  atlas  from  below. 


tion  of  the  prolonged  axes  of  the  articular  facets  ranges  from  thirty-two  to  sixty- 
three  degrees.  Each  lateral  mass  presents  a  rough  tubercle  on  the  inner  side  between 
which  passes  the  transverse  ligament  holding  the  odontoid  process  close  against  the 
anterior  arch.  The  anterior  arch  is  compressed  from  before  backward.  It  presents 
the  anterior  tubercle  in  front  in  the  median  line,  and  behind  has  a  slightly  concave 
articular  facet  for  the  odontoid  process.  The  posterior  arch  bounds  the  spinal  canal 
behind.  The  transverse  ligament,  confining  the  odontoid  process,  bounds  the  spinal 
canal  in  front,  and,  being  in  place,  the  transverse  diameter  of  the  canal  is  the  longer. 
The  place  of  the  spinous  process  is  taken  by  the  posterior  tubercle.  The  transverse 
processes  extend  farther  out  than  any  in  the  cervical  region.  Each  ends  in  a  single 
flattened  knob  with  a  surface  slanting  downward  and  forward.  Bifurcation  is  rare. 
The  transverse  foramen  is  at  its  base  ;  from  the  foramen  a  groove  for  the  vertebral 
artery  crosses  the  root  of  the  posterior  arch  and  winds  round  behind  the  raised 
border  of  the  articular  surface.  This  groove  is  occasionally  bridged  over  by  a  little 
arch  of  bone  extending  from  the  edge  of  the  articular  surface  either  to  the  trans- 
verse process  or  to  the  posterior  arch. 

Variations. — The  atlas  may  be  fused  with  the  occipital  bone  in  various  ways; 
this  may  occur  by  the  pathological   destruction   of  the  joint,  or  the  arch,   or  a 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxvii.,  1893. 


THE   AXIS. 


Superior 
articular 
facet 


Articular  facet  on  front 
dontoid  process 


part  of  it,  may  be  fused  with  the  skull  around  the  foramen  magnum.  Such  union 
may  be  partial  or  complete,  and  is  usually  associated  with  an  imperfect  development 
of  the  atlas,  especially  on  one  side.  There  is  reason  to  regard  such  cases  as  con- 
genital. The  transverse  process  and  the  paroccipital  process  of  the  occipital  bone 
may  be  connected  by  bone. 

The  axis '  differs  less  from  the  other  cervical  vertebrae  ;  seen  from  below  it  pre- 
sents no  essential  peculiarity.  The  body  is  very  long  even  without  the  odontoid 
process  (the  separated  body  of  the  atlas)  which  surmounts  it.  The  odontoid?  a 
cylindrical   process   lower  behind  than 

in  front,  ends  above  in  a  median  ridge,  " 

on  either  side  of  which  is  a  rough,  slant- 
ing surface  for  the  origin  of  the  check 
ligaments  connecting  it  with  the  skull. 
It  bears  an  oval  articular  facet  in  front, 
resting  against  one  on  the  atlas,  and  a 
smaller  facet  behind  at  a  lower  level 
which  forms  part  of  a  joint  with  the 
transverse  ligament.  The  lamina,  in- 
stead of  being  plates,  are  heavy  and 
prismatic,  each  with  a  rather  sharp 
upper  edge,  which,  meeting  its  fellow, 
forms  a  ridge  on  the  spine.  The  spinous 
process  is  heavy,  projecting  considerably 

beyond  the  third.      It  varies  greatly  in  The  axis  from  in  fro,lt. 

length    and    in    degree   of    bifurcation. 

The  transverse  process  is  small  ;  the  anterior  tubercle  is  a  mere  point  or  altogether 
wanting.  The  transverse  foramen  is  replaced  by  a  short  canal,  so  curved  that  its 
upper  opening  looks  almost  outward.  The  superior  articular  surfaces  are  approxi- 
mately circular  facets  on  the  upper  surface  of  the  body  instead  of  on  the  arch,  as 
are  all  below  ;  they  look  upward  and  a  little  outward.  Although  nearly  plane,  they 
present  a  very  slight  antero-posterior  convexity. 

The  seventh  cervical  vertebra,  called  vertebra  prominens  on  account  of  its 
long,  knobbed  spine,  rather  resembles  the  upper  thoracics.     The  transverse  foramen 

is  smaller  than  those  above  it, 
Fig.  151.  and  the  anterior  tubercle  of  the 

transverse  process  is  particu- 
larly small  and  near  the  body. 
The  first  thoracic  ver- 
tebra has  the  sides  of  the 
upper  surface  somewhat  raised 
at  the  roots  of  the  pedicles. 
It  has  a  complete  facet  for  the 
head  of  the  first  rib  and  a  half- 
facet  at  the  lower  border  of  the 
body.  Sometimes  the  former 
is  imperfect,  being  completed 
on  the  intervertebral  disk. 
The  facet  on  the  transverse 
process  is  smaller  and  less  con- 
cave than  the  ones  following  ; 
sometimes  it  is  even  convex. 
The  ninth  thoracic  vertebra  has  no  half-facet  below. 

The  tenth  thoracic  vertebra  has  a  nearly  complete  facet  above  and  none 
below. 

The  eleventh  thoracic  vertebra  has  a  complete  facet  on  the  body  and  none  on 
the  transverse  process,  which  is  small. 

The  twelfth  thoracic  vertebra  has  a  complete  facet  a  little  above  the  middle 
of  the  body.  The  transverse  process  is  broken  up  into  the  three  tubercles.  The 
lower  articular  facets  face  outward.      The  spine  is  of  the  lumbar  type. 


Odontoid  proce 


Articular  facet  for  transverse  ligament 


Spinous  process 


Inferior  articular 
process  and  facet 

The  axis  from  the  side. 


HUMAN   ANATOMY. 


The  fifth  lumbar  vertebra  is  much  higher  in  front  than  behind.  The  trans- 
verse process  is  broad  at  the  base,  springing  in  part  from  the  body  ;  the  spine  is 
relatively  small. 

DIMENSIONS    OF    VERTEBRA. 

(The  measurements  are  given  in  centimetres. ) 


Height      of 

Height       of 

Height       of 

Transverse 
Diameter. 
(Anderson.) 

Antero- 

Spread      of 

Vertebrae. 

Front      of 
Bodies. 

Front      of 
Bodies. 

Back       of 
Bodies. 

posterior 
Diameter. 

Transverse 
Processes. 

(Dwight.) 

(Anderson.1) 

(Anderson.) 

(Anderson.) 

(Dwight.) 

Twenty 

Thirty 

Thirty 

Fifty-three 

Twenty-eight 

Fourteen 

spines. 

spines. 

spines. 

spines. 

spines. 

spines. 

Cervical     .    . 

2 

!-9 

1-9 

1-5 

5-5 

" 

3 

1.2 

1.2 

i-9 

i-5 

5-4 

4 

1.2 

1.2 

2.1 

1-5 

5-4 

" 

5 

1.2 

1.2 

2-3 

1.6 

5-7 

" 

6 

I.I 

I.I 

2-5 

i-7 

5-9 

" 

7 

1-3 

1-3 

2.7 

1.8 

7.2 

Thoracic 

i 

1-5 

1.4 

1-5 

2.7 

i-7 

7.6 

" 

2 

1-7 

1.6 

i-7 

2.8 

i-7 

7-i 

" 

3 

i-7 

i-7 

i.8 

2.6 

1-9 

6-3 

(( 

4 

i-7 

i-7 

i-9 

2.6 

2.2 

6-3 

" 

5 

i-7 

i-7 

2.0 

•  2.5 

2.4 

6.4 

" 

6 

i.8 

i.8 

i-9 

2.7 

2.5 

6.4 

" 

7 

i.8 

i.8 

2.0 

2.8 

2.6 

6-3 

" 

8 

i.8 

i.S 

2.1 

3-° 

2.8 

6-3 

" 

9 

i-9 

i-9 

2.1 

3-i 

2.9 

6.2 

IO 

2.1 

2.1 

2.2 

3-4 

2.9 

5-3 

n 

2.1 

2.1 

2-4 

3-6 

2.9 

5-2 

" 

12 

2-3 

2-3 

2-5 

4.0 

3-° 

4-7 

Lumbar 

I 

2.4 

2.4 

2.6 

4.2 

2.9 

7-3 

" 

2 

2-5 

2-5 

2.7 

4-4 

3-i 

8.0 

3 

2-5 

2.6 

2.7 

4-7 

3-6 

9.0 

" 

4 

2-5 

2.6 

2.6 

4.8 

5-3 

8.5 

5 

2.6 

2.7 

2.2 

5-2 

3-6 

9-i 

GRADUAL  CHANGES  FROM  ONE  REGION  TO  ANOTHER. 

Bodies. — The  height  of  the  bodies  increases  as  we  descend  the  spine,  very 
gradually  in  each  region  but  rather  rapidly  at  the  junction  of  two  regions,  as  shown 
in  the  table.  The  first  two  lumbars,  like  those  above  them,  are  rather  deeper  behind 
than  in  front,  but  the  reverse  is  true  of  the  last  two,  and  especially  of  the  fifth,  in 
which  the  difference  is  considerable.  The  breadth  of  the  bodies  increases  to  the 
first  or  second  thoracic,  then  dwindles  to  the  fourth  or  fifth,  and  then  again  increases 
to  the  sacrum.  The  elevation  at  the  sides  of  the  upper  surfaces  of  the  bodies  of  the 
cervical  vertebra?  diminishes  in  the  lower  part  of  that  region  ;  in  the  seventh  it  is 
limited  to  near  the  root  of  the  pedicle.  The  same  condition  is  found  in  the  first 
thoracic  vertebra  and  to  a  slight  extent  in  the  next  two.  The  downward  prolonga- 
tion of  the  front  of  the  body  of  a  cervical  vertebra  is  slight  in  the  lower  part  of  the 
neck.  The  first  thoracic  has  an  entire  facet  for  the  head  of  the  first  rib  near  the  top 
of  the  body  and  a  part  of  one  at  the  lower  border  for  a  portion  of  the  head  of  the 
second.  As  a  rule,  in  the  thoracic  region  the  head  of  each  rib  rests  in  a  facet  on 
two  vertebrae  and  the  intervening  disk,  the  lower  vertebra  contributing  more  of  the 
joint  than  the  upper,  and  corresponding  with  the  rib  in  name.  Thus,  the  head 
of  the  fourth  rib  lies  between  the  third  and  fourth  thoracic  vertebrae,  and  its  tubercle 
rests  on  the  transverse  process  of  the  fourth.  Towards  the  lower  part  of  the  region 
the  heads  have  a  tendency  to  take  a  lower  relative  position  on  the  column  coinci- 
dently  with  the  increase  in  size  of  the  bodies.  The  head  of  the  tenth  rib  usually 
rests  wholly  on  the  body  of  the  tenth  vertebra  or  on  it  and  the  disk  above,  conse- 

1  Journal  of  Anatomy  and  Physiology,  vol.  xvii.,  1883.  Anderson  states  that  the  vertical 
diameters  of  the  front  and  back  of  the  cervical  vertebrae  are  generally  the  same  ;  hence,  prob- 
ably, he  thought  it  needless  to  give  the  posterior  measurements.  The  close  correspondence  of 
his  anterior  measurements  with  those  of  the  author  is  very  striking. 


REGIONAL   CHANGES.  123 

quently  the  ninth  vertebra  has  no  half-facet  below.  The  tenth  has  a  nearly  or  quite 
complete  facet  at  its  upper  border,  the  eleventh  has  a  complete  one  rather  below 
the  top  of  the  body,  and  the  twelfth  has  a  complete  facet  nearly  half-way  down. 
At  the  ninth  or  tenth  the  facet  begins  to  leave  the  body  and  to  travel  backward 
onto  the  root  of  the  .pedicle. 

When  the  body  is  seen  from  above  or  below  in  certain  parts  of  the  thoracic 
region  the  front  curve  is  flattened  on  the  left  by  the  pressure  of  the  aorta.  This  com- 
pression usually  is  first  seen  at  the  top  of  the  fifth  thoracic,  and  is  traceable  down- 
ward for  a  few  vertebrae,  sometimes  as  far  as  the  lumbar  region.  The  depression 
gradually  passes  from  the  side  to  the  front  as  it  descends  the  spine. 

The  Transverse  Processes. — As  shown  by  the  table,  the  spread  of  the 
transverse  processes  increases  greatly  at  the  junction  of  the  cervical  and  the  thoracic 
regions,  falls  rapidly  to  the  third  thoracic,  remains  stationary  to  the  tenth,  falls  to  the 
last  thoracic,  the  narrowest  point,  and  then  gains  at  once,  reaching  the  maximum  at 
the  third  lumbar.  The  anterior  tubercles  of  the  transverse  processes  of  the  cervical 
region  increase  to  the  sixth,  which  is  the  tubercle  of  Chassaignac,  who  taught  that 
the  carotid  artery  can  be  compressed  against  it,  the  force  being  directed  backward 
and  a  little  inward.  The  anterior  limb  of  the  transverse  process  of  the  seventh  ver- 
tebra is  very  short,  and  its  tubercle  is  usually  rudimentary.  It  is  distinctly  in  series 
with  the  slight  elevation  of  the  socket  for  the  head  of  the  first  rib  often  seen  on  the 
first  thoracic  vertebra.  The  piece  of  bone  between  the  tubercles,  forming  the  floor 
of  the  gutter  for  the  spinal  nerve,  is  much  longer  and  more  anteriorly  placed  in  the 
seventh  than  in  those  above  it.  It  is  this  piece  connecting  the  two  tubercles  that  is 
the  true  costal  element  in  the  neck.  The  so-called  anterior  limb  of  the  transverse 
process  with  the  tubercle  on  it  is  in  line,  not  with  the  ribs  but  with  the  anterior 
tubercle  called  the  processus  costarius.  The  articular  facet  on  the  transverse  process 
of  the  first  thoracic  is  shallow,  often  convex,  and  faces  a  little  downward.  That  of 
the  second,  at  which  point  the  processes  slant  more  backward,  is  concave  and  some- 
what overhung  above  ;  this  is  seen  in  the  two  or  three  following,  after  which  the 
facets  grow  smaller,  more  shallow,  and  look  upward  as  well  as  forward.  As  the 
eleventh  rib  has  but  a  rudimentary  tubercle  and  the  twelfth  none  at  all,  there  is  no 
facet  on  the  transverse  process  of  the  last  two  thoracic  vertebrae.  The  latter  process 
of  the  eleventh  is  small,  and  that  of  the  last  broken  up  into  three  tubercles,  (1)  the 
superior  or  mammillary,  rising  from  the  posterior  surface  ;  (2)  the  accessory  or  infe- 
rior, pointing  downward  ;  (3)  the  external,  a  knob,  the  smallest  of  the  three.  The 
latter  two  represent  the  transverse  process  of  the  upper  thoracic  vertebrae.  All  three 
tubercles  are  usually  to  be  recognized  on  the  eleventh  thoracic,  although  the  acces- 
sory tubercle  is  usually  not  seen  higher  up.  The  knobs  for  muscular  attachment  on 
the  backs  of  the  thoracic  transverse  processes  are  evidently  in  line  with  the  mammil- 
lary  tubercles,  rudiments  of  which  are  found  in  a  large  part  of  the  thoracic  region. 
In  the  lumbar  region  they  are  found  on  the  sid^  of  the  superior  articular  processes, 
growing  smaller  in  the  lower  vertebras,  and  being  lost  in  the  fifth. 

The  lumbar  transverse  processes  increase  in  length  to  the  third,  which  is  the 
longest,  unless  it  be  equalled  by  the  fifth.  That  of  the  fourth  is  peculiar  in  being 
shorter  and  lighter  than  its  neighbors.  It  usually  has  a  rather  triangular  outline, 
owing  to  the  lower  border  approaching  the  upper  near  the  tip,  and  also  arises  farther 
forward, — i.e. ,  nearer  the  side  of  the  pedicle  than  those  above  it.  The  fifth  is  much 
heavier  and  arises  from  the  side  of  the  body  as  well  as  from  the  pedicle,  so  that  its  ante- 
rior portion  is  evidently  in  series  with  the  costal  element  developed  in  the  sacrum, 
described  in  connection  with  that  bone.  The  process  which,  in  accordance  with  gen- 
eral usage,  has  been  called  the  lumbar  transverse  process,  is  clearly  in  direct  continua- 
tion with  the  line  of  the  ribs.  This  is  particularly  striking  in  certain  cases  in  which  it  is 
not  easv  to  determine  whether  there  is  a  thirteenth  rib,  or  whether  this  process  is  to 
be  considered  as  free  in  the  first  lumbar.  The  accessory  tubercle,  which  can  be 
made  out  in  the  lumbar  region,  and  is  particularly  large  in  the  lower  vertebrae,  is 
in  line  with  the  ends  of  the  transverse  processes  of  the  thorax.  Thus  the  so-called 
lumbar  transverse  process  represents  at  its  root  both  a  rib  and  the  accessory  and 
transverse  tubercles,  and  beyond  its  root  a  rib  only.  This  is  especially  marked 
in  the  broad  process  of  the  fifth  lumbar,  which  springs  from  the  side  of  the  body 


124 


HUMAN    ANATOMY. 


as  well  as  from  the  pedicle.  The  homologies  of  the  costal  elements  are  shown  in 
Fig.  158. 

The  Spinous  Processes. — These  are  short  and  bifid  in  the  third,  fourth,  and 
fifth  cervical  vertebrae  ;  longer  and  usually  not  forked  in  the  sixth  ;  and  longer,  larger, 
and  knobbed  in  the  seventh.  The  type  is  that  of  the  last  mentioned  in  the  upper 
thoracic,  only  the  spine  is  a  little  longer,  stronger,  and  more  slanting.  At  about  the 
fourth  a  sudden  change  occurs  :  the  process  becomes  longer,  sharper,  and  more 
descending.  At  about  the  tenth  it  shortens  again,  points  more  backward,  and 
approaches  the  lumbar  type,  which  is  generally  reached  in  the  last  thoracic.  The 
spine  of  the  last  lumbar  is  usually  much  smaller  than  those  above  it. 

The  Articular  Processes. — The  change  from  the  cervical  type  to  the  thoracic 
is  gradual,  but  that  from  the  thoracic  to  the  lumbar  occurs  suddenly  at  the  junction 
of  those  regions.  The  inferior  processes  of  the  last  thoracic  face  outward.  Not  infre- 
quently the  change  occurs  a  space  higher,  but  rarely  one  lower.  Occasionally  the 
facets  between  the  regions  face  in  an  intermediate  direction.  Sometimes  the  change 
is  normal  on  one  side  and  not  on  the  other. 


Fig.  152. 

Promontory 


Transverse  process 


Lines  of  union 
between  fused 
sacral  vertebra? 


Notch  for  fifth  sacral 


The  sacrum,  anterior  surface. 


THE   SACRUM. 
This  bone '  is  composed  of  five  fused  and  modified  vertebrae,  of  which  the  three 
upper  support  the  pelvis  laterally.      The  vertebrae  decrease  very  much  in  size  from 
above  downward,  the  lower  being  bent  strongly  forward.      The  first  vertebra  is  com- 
paratively but  little  changed  ;  the  last  consists  of  little  more  than  the  body.      The 


THE    SACRUM. 


125 


essential  modification,  besides  the  fusion,  is  the  occurrence  of  the  lateral  masses,1 
representing  transverse  processes  and  ribs,  which,  springing  from  the  bodies  and 
arches,  are  connected  with  the  innominate  bones  by  joints  and  ligaments.  The 
sacrum  has  an  upper  surface,  or  base,  a  lower,  or  apex,  and  a  front,  back,  and  two 
lateral  surfaces.  The  base  has  above  a  rough  space  representing  the  end  of  the 
body  of  a  vertebra  to  which  the  last  lumbar  disk  is  attached.  It  is  raised  a  little 
from  the  bone  and  forms  an  acute  projecting  angle  with  the  front  surface,  known  as 
the  promontory  of  the  sacrum,  an  important  landmark  in  midwifery.  Behind  the 
body  of  the  first  sacral  vertebra  is  the  triangular  orifice  of  the  sacral  canal,  the 


Fig.  153. 


Articular  process 


Sacral  canal 


The  sacrum,  poste 


Sacral  canal 
>r  surface. 


transverse  diameter  of  which  is  the  greater.  The  articular  process,  springing  from 
the  side  of  the  arch,  is  vertical,  the  concave  facet  facing  backward  and  inward.  The 
upper  surface  of  the  lateral  mass,  the  ala,  springs  from  the  side  of  the  body  and 
the  pedicle,  expanding  into  a  broad  area,  and  is  bounded  in  front  by  an  ill-marked, 
rounded  border  which  separates  it  from  the  anterior  surface  and  curves  forward  ; 
behind  by  a  shorter  border  curving  backward,  on  which  the  auricular  process  rests  ; 
and  outside  by  an  irregular  convex  border.  The  latter  may  often  be  subdivided 
into  two  parts  :  an  anterior,  running  pretty  nearly  forward  and  backward  and  cor- 
responding to  the  top  of  the  auricular  surface,  and  a  posterior,  running  backward 


1  Partes  laterales. 


126 


HUMAN   ANATOMY. 


Articular  process 


Rudimentary 
transv 
processes 


and  inward.      Thus  the  sacrum  is  broader  before  than  behind.      The  apex  is  nothing 
but  the  under  side  of  the  body  of  the  very  small  fifth  sacral  vertebra. 

The  anterior  surface  is  a  triangular  concavity  formed  by  the  bodies  and  lat- 
eral masses  of  the  five  sacral  vertebra;.  It  has  a  double  row  of  four  openings,  the 
anterior  sacral  foramina,  one  on  each  side  of  the  ridges,  representing  the  ossified 
disks  connecting  the  bodies  of  the  fused  sacral  vertebrae.  The  sacral  nerves,  like 
the  other  spinal  nerves,  divide  into  an  anterior  and  a  posterior  division  on  leaving 
the  spinal  canal  ;  in  the  case  of  the  sacral  nerves,  however,  this  takes  place  inside 
the  bone,  the  anterior  divisions  escaping  by  these  foramina.  The  bodies  and  the 
foramina  grow  smaller  from  above  downward,  and  the  latter  are  nearer  together.  A 
transverse  depression  across  the  body  of  the  third  vertebra  usually  marks  a  rather 

sudden    change    in    the 
Fig.  154.  curvature  of  the  anterior 

Transverse  process  surface.       The    irregular 

outline  of  thejateral  bor- 
ders may  be  divided  into 
two  parts  :  the  upper, 
rather  concave,  ends  be- 
low in  a  little  point  on  a 
level  with  the  third  verte- 
bral body,  and  represents 
the  extent  of  the  articu- 
lar surface.  Below  this 
the  border  slants  down- 
ward and  inward  until 
opposite  the  lower  part 
of  the  fifth  sacral  seg- 
ment, when  it  suddenly 
turns  inward,  forming  a 
notch  over  the  anterior 
division  of  the  fifth  sacral 
nerve,  which  emerges  be- 
tween it  and  the  coccyx. 
The  posterior  sur- 
face is  composed  of  the 
fused  lamina  and  their 
modifications.  The  up- 
per borders  of  the  first 
laminae  slant  downward, 
and  below  their  junction 
is  a  well-marked  spine} 
Below  this  the  laminae  of 
the  sacral  vertebrae  are 
fused  and  the  spines 
small.  The  laminae  of 
the  fifth  sacral  never  join, 
and  those  of  the  fourth 
frequently  do  not,  thus  leaving  the  lower  end  of  the  canal  uncovered.  The  laminae 
that  do  not  meet  end  in  tubercles  each  representing  one-half  of  a  spinous  process. 
The  lowest  two  project  downward  at  the  sides  of  the  open  canal,  and  are  called  the 
sacral  comua.  Four  posterior  sacral  foramina  for  the  exit  of  the  posterior  divisions 
of  the  nerves  appear  on  each  side  of  the  laminae.  Outside  of  these  are  some  irregu- 
lar tubercles  representing  the  transverse  processes^  and  internal  to  the  first  three 
foramina  are  tubercles  in  line  with  the  articular  processes} 

The  lateral  surface  begins  just  outside  of  the  transverse  tubercles.  It  is 
broad  above,  but  below  the  third  vertebra  is  merely  a  line.  The  upper  part  is 
divided  into  two  portions  :  the  front  one  is  the  auricular  S7crface,  from  a  slight 
resemblance  to  an  ear,  which  joins,  by  fibro-cartilage,  the  corresponding  surface  on 
the  ilium.      It  is  broader  above  than  below,  convex  in  front,  indented  behind,  with 

Crista  media.      -Cristac  lateralis.      ;  Cristac  articulares. 


Auricular 
(articular) 
surface 


Fourth  posterior  sacral  foramen 


Sacral  < 
The  sacrum,  lateral  v: 


THE   COCCYX. 


127 


slightly  raised  edges  and  a  rough,  irregular  surface.  The  auricular  surface  is  formed 
chiefly  by  the  lateral  mass  of  the  first  sacral  (vertebra  fulcraHs ,  as  having  the  most 
to  do  in  supporting  the  pelvis),  to  a  less  extent  by  that  of  the  second,  and  very  little 
by  that  of  the  third.  Behind  this  articular  portion  lies  the  rough  ligamentous  sur- 
face, which  slants  backward  and  inward,  and  affords  origin  for  the  posterior  sacro- 
iliac ligaments. 

Differences  depending  upon  Sex. — The  female  sacrum  is  relatively  broader 
than  the  male.  The  sacral  index,  or  the  ratio  of  the  breadth  to  the  length  ( '°°  *  bref"h  \, 
is  112  for  the  white  male  and  116  for  the  female.  Such  a  rule  is,  however,  not  abso- 
lute, there  being  many  doubtful  cases,  but  a  narrow  sacrum  is  almost  invariably 
male.  Another,  and  very  reliable,  guide,  especially  in  conjunction  with  the  first,  is 
the  curve.  There  are  contradictory  statements  among  authors,  but  the  truth  is,  as 
originally  shown  by  Ward,  that  the  male  sacrum  is  the  more  regularly  curved,  while 
the  anterior  surface  of  the  female  bone  runs  in  nearly  a  straight  line  from  the  prom- 
ontory to  the  middle  of  the  third  piece  and  then  suddenly  changes  its  direction. 

Variations. — The  sacrum  often  consists  of  six  vertebrae.  Such  a  one  may 
be  recognized  even  when  the  lower  part  is  wanting,  so  that  the  vertebrae  cannot  be 
counted.  If  a  line  across  the  front,  connecting  the  lowest  points  of  the  auricular 
surfaces,  passes  below  the  middle  of  the  third  sacral,  the  sacrum  is  of  six  pieces  ;  if 
above,  of  five. 1    Sacra  consisting  of  only  four  vertebrae  are  rare. 

THE    COCCYX. 

This  bone  is  composed  of  four  or  five z  flattened  plates  representing  vertebral 
bodies.  It  is  an  elongated  triangle  with  the  apex  below.  The  base,  joined  by  fibro- 
cartilage  to  the  apex  of  the  sacrum,  is  oblique,  the  posterior  border  being  higher 
than  the  front,  so  that  the  coccyx  slants  forward  from  the  sacrum.  The  anterior 
surface  of  the  coccyx  is,  moreover,  very  slightly  concave.  The  first  vertebra  consists 
of  a  thin  body,  about  twice  as  broad  as  long,  from  the  back  of  which  on  each  side  the 
rudiment  of  an  arch  extends  upward  as  a  straight  process,  the  coccygeal  cornu,  which 


Fig.  155. 


Surface  for 
Transverse  p 


Transverse  process 


Gluteus  maximus 


•Sphincter  < 


overlaps  the  back  of  the  body  of  the  last  sacral  vertebra  and  joins  the  sacral  cornu. 
A  short  lateral  projection  from  the  side  of  the  body  represents  the  transverse  process; 
perhaps  the  costal  element  also.  On  the  upper  border  of  this  process,  at  its  origin,  is 
a  notch,  which  usually  forms  a  foramen  with  the  sacrum  for  the  anterior  division  of 
the  fifth  sacral  nerve.  Very  faint  rudiments  of  these  two  pairs  of  processes  are 
sometimes  to  be  made  out  on  the  second  vertebra,  which  is  much  smaller  than  the 
first,  but  also  broad  and  flat.  The  succeeding  ones  are  much  smaller  and  ill-defined. 
Constrictions  on  the  surfaces  and  notches  on  the  edges  mark  the  outlines  of  the 

1  Bacarisse  :  Le  sacrum  suivant  le  sexe  et  suivant  les  races.     Th&se,  Paris,  1873. 

2  According:  to  Steinbach,  there  are  five  in  man  and  four  or  five  in  woman.     Die  Zahl  der 
Caudalwirbel  beim  Menschen.    Inaugural  Dissertation,  Berlin,  i8qg. 


128 


HUMAN   ANATOMY. 


original  pieces,  which  become  less  and  less  flat  and  more  and  more  rounded.  It  is 
rare  to  see  more  than  four  distinct  segments,  but  very  often  the  last  is  somewhat 
elongated  and  shows  signs  of  subdivision.  It  is  not  uncommon  for  the  first  piece 
to  remain  separate,  neither  fusing  with  the  sacrum  nor  the  next  coccygeal  plate. 

STRUCTURE    OF    THE   VERTEBRAE. 

The  shell  of  compact  bone  forming  the  surface  is  everywhere  very  thin.  The 
general  plan  of  the  internal  spongy  bone  is  one  of  vertical  plates  which  in  a  frontal 
section  (Fig.  156,  A)  are  bowed  somewhat  outward  from  the  middle  of  the  bone,  and 
of  transverse  plates  connecting  them  near  together  at  the  ends  and  farther  apart  in  the 


Fig.  156. 


middle  third  where  larger  spaces  occur.  The  strongest  plates  spring  from  the  pedi- 
cles and  diverge  through  the  bone,  joining,  probably,  for  the  most  part  the  hori- 
zontal system.  In  the  sacrum  the  same  general  plan  prevails,  but  in  addition  there 
are  series  of  plates,  mainly  horizontal,  in  the  lateral  parts  ;  those  from  the  first  sacral 
are  the  most  important. 

DEVELOPMENT  OF  THE  VERTEBRAE. 

Presacral  Vertebrae. — These  vertebrae  ossify  from  three  chief  centres  and 
at  least  five  accessory  ones.  The  median  one  of  the  three  chief  centres  forms  the 
greater  part  of  the  body  ;  while  the  other  two,  one  appearing  in  each  pedicle,  form 
the  postero-lateral  part  of  the  body,  the  arch,  and  the  greater  part  of  the  processes. 
The  oblique  ?ienro-central  sutures  separate  the  regions  of  these  centres.  The  lat- 
eral centres  of  the  upper  thoracic  and  the  cervical  vertebra;  appear  first.  It  is 
usually  taught  that  they  appear  in  the  sixth  or  seventh  week  of  fcetal  life,  but  Bade ' 
with  the  Rontgen  rays  found  no  sign  of  them  at  eight  weeks.  The  point  is  unset- 
tled. The  first  median  centres  to  appear  are  those  of  the  lower  thoracic  and  the 
upper  lumbar  vertebrae.  In  this  region  and  below  it  the  median  centres  precede  the 
lateral  ones  ;  in  the  upper  part  of  the  spine  the  growth  is  much  more  vigorous  in 
the  lateral  centres.  The  median  centres  of  the  cervical  vertebrae  appear  in  order 
from  below  upward.  The  upper  ones  (judging  from  Rontgen-ray  work  and  from 
transparent  foetuses)  sometimes  have  not  appeared  as  late  as  the  sixth  month, 
although  we  have  seen  them  towards  the  close  of  the  third. 

At  bi?'th  the  upper  and  lower  ends  of  the  bodies  are  still  cartilaginous,  but  the 
arches  are  well  advanced  in  ossification,  although  bone  does  not  cross  the  median 
line  until  some  months  later.  The  transverse  processes  of  the  thoracic  vertebrae  are 
farther  advanced  than  those  in  other  regions.  The  spines  are  still  cartilaginous. 
The  neuro-central  suture  is  lost  at  from  four  to  six  years,  disappearing  first  in  the 

1  Arch,  fur  Mikros.  Anat,  Bd.  lv,,  1899. 


DEVELOPMENT  OF  THE  VERTEBRAE. 


129 


lumbar  region.  The  tips  of  the  spinous  and  transverse  processes  develop  from  cen- 
tres which  appear  about  puberty  and  fuse  about  the  eighteenth  year.  A  thin  epi- 
physeal disk,  covering  the  upper  and  lower  surfaces  of  each  body,  grows  from  a  centre 
seen  about  the  seventeenth  year,  and  joins  by  the  twentieth,  the  line  of  union  per- 
sisting a  year  or  two  longer.  The  mammillary  processes  of  the  lumbar  region  arise 
from  separate  centres  ;  so  do  also  the  costal  elements  of  the  sixth  and  seventh  cer- 
vicals,  and  sometimes  that  of  the  first  lumbar.  In  cases  in  which  this  costal  element 
of  the  seventh  cervical  remains  free  there  is  a  cervical  rib  and  no  transverse  fora- 
men ;  exceptionally  in  these  cases  a  foramen  persists.  According  to  Leboucq,1  the 
development  of  the  anterior  limb  of  the  transverse  process  of  the  cervical  vertebra? 
is  more  complicated  than  is  usually  taught.  There  is  a  slight  outward  projection 
from  the  ventral  side  of  the  body  rep- 


Fig.  157. 


resenting  the  prominence  for  the  head 
of  the  rib  to  rest  upon  ;  this  grows  out- 
ward and  meets  a  growth  from  the 
transverse  process  that  grows  inward 
like  a  hook.  This  inward  growth  rep- 
resents what  we  commonly  call  the 
costal  element  of  a  cervical  vertebra, 
but  there  may  be  also  a  separate  ossi- 
fication representing  an  actual  rib, — 
namely,  a  small  piece  of  bone  on  the 
ventral  aspect  of  the  tip  of  the  trans- 
verse process  of  the  seventh  cervical 
vertebra.  When  a  separate  ossifica- 
tion occurs  in  this  region  in  the  fifth 
or  sixth  vertebra,  it  is  situated  still 
more  externally  than  in  the  seventh, 
and  forms  the  floor  of  the  gutter  be- 
tween the  anterior  and  the  posterior 
tubercles,  which  is  the  true  costal  ele- 
ment. It  is  probable  that  in  certain 
cases  of  cervical  ribs  accompanied  by 
a  transverse  foramen,  the  latter  is  en- 
closed by  the  hook-like  process  from 
the  transverse  process  meeting  the 
growth  from  the  body  of  the  vertebra, 
and  that  the  rib  coming  from  the 
separate  ossification  lies  anteriorly  to 
it  and  distinct  from  it.  At  birth  the 
lumbar  articular  processes  resemble 
the  thoracic.  The  type  changes  in 
early  childhood. 

The  Sacrum. — Each  sacral  ver- 
tebra has  the  three  primary  centres  of 
the  others,  the  median  ones  appearing  before  the  lateral  of  the  same  vertebra.  Proba- 
bly the  median  centres  of  the  first  three  appear  first  and  then  the  lateral  ones  of  the 
first  vertebra  ;  data,  however,  are  wanting  for  a  definite  statement.  The  time  of  the 
first  appearance  of  ossification  in  the  sacral  vertebra?  is  very  variable  ;  probably  the 
earliest  median  centres  appear  about  the  beginning  of  the  fourth  month  and  the 
lateral  ones  some  weeks  later.  In  a  skiagraph  of  a  fcetus  estimated  to  be  about 
three  and  a  half  months  old  the  median  centres  of  the  upper  three  vertebrae  and 
the  lateral  ones  of  the  first  are  visible.  This  is,  perhaps,  earlier  than  the  rule.  Little 
progress  in  ossification  of  the  last  two  sacrals  takes  place  before  birth.  The  lateral 
centres  join  the  median,  in  the  lower  vertebras,  during  the  second  year  ;  in  the  upper 
ones,  three  or  four  years  later.  In  the  upper  three  vertebrae  a  centre  appears  out- 
side the  anterior  sacral  foramen,  from  which  a  part  of  the  lateral  mass  is  developed. 

1  M^moires  couronn^s,  etc.,  Acad.  Royale  des  Sciences  de  Belgique,  tome  lv.,  1896. 

9 


Ossification  of  the  vertebrae.  A,  cervical  vertebra  at 
birth  ;  centres  for  body  (a ) ,  neural  arches  {b) ,  and  costal  ele- 
ment (c).  B,  dorsal  vertebra  at  two  years;  cartilaginous 
tips  of  transverse  {a)  and  spinous  (5)  processes;  d,  centre 
for  body.  C,  lumbar  vertebra  at  two  years ;  position  of  ad- 
ditional later  centres  for  various  processes  indicated  (a,  dt  c) ; 
d,  centre  for  body. 


13° 


HUMAN    ANATOMY. 


This  represents  a  costal  element  which  fuses  with  the  front  of  the  pedicle.  Those  of 
the  first  two  sacrals  appear  shortly  before  birth  (Bade).  The  line  of  union  can  still 
be  seen  at  seven  years  on  the  top  of  the  first  vertebra.     The  time  at  which  the  laminae 


Costal  element 


Illustrating  homology  of  costal  element  (c.  e.).   A,  sixth  cervical  vertebra;  B,  seventh  cervical;  C,  fifth  thoracic; 
Z>,  second  lumbar ;  E,  fifth  lumbar  ;  F,  sacrum  in  transverse  section. 

meet  in  the  middle  is  uncertain  ;  the  arch  of  the  first  vertebra  is  sometimes  complete 
at  seven,  those  below  it  being  still  open.  The  five  distinct  sacral  vertebras  which  are 
thus  formed  remain  separate  for  some  time,  the  bodies  being  separated  by  interver- 

Fig.  159. 


and  anterior  surfaces  of  young  sacrum 
of  about  five  years. 


Sacrum  and  coccyx  of  about  seventeen  years. 


tebral  disks.  A  thin  plate  appears  in  the  upper  and  lower  parts  of  these  disks  which 
fuses  with  the  bodies  before  the  latter  unite.  The  union  of  the  vertebrae  begins  below 
and  proceeds  upward  in  a  very  irregular  manner. 

Probably  union  generally  occurs  first  in  the  lateral  masses,  between  the  laminae 


VARIATIONS    OF    THE   VERTEBRA.  131 

sooner  than  between  the  bodies.  By  the  fifteenth  year  the  lower  three  vertebra  are 
generally  fused,  the  second  joining  them  from  eighteen  to  nineteen.  The  five  pieces 
are  united  by  the  twentieth  year.  In  some  cases  several  of  the  sutures  are  still  to  be 
seen,  but  all  may  have  disappeared.  The  union  of  the  bodies,  as  shown  by  sections, 
in  the  case  of  the  upper  ones,  may  not  be  complete  internally  till  a  much  later  period. 
Two  thin  epiphyses  appear  on  each  side  of  the  sacrum  about  the  eighteenth  year, 
one  for  the  auricular  sw-face  and  the  other  below  it.  The  lines  of  union  of  these 
plates  may  be  visible  after  twenty-one. 

The  Coccyx. — Our  data  concerning  the  ossification  of  the  coccyx  are  very  un- 
satisfactory. Each  segment  has  one  centre,  but  the  first  may  have  two,  one  on  each 
side,  and,  according  to  some,  secondary  centres  for  the  cornua.  Ossification  begins 
in  the  first  piece  at  about  birth,  and  successively  in  the  others,  from  above  down- 
ward, until  puberty.  The  lower  three  or  four  pieces  fuse  within  two  or  three  years 
after  birth,  and  join  the  first  at  perhaps  about  twenty ;  there  is,  however,  great 
diversity,  and  frequently  the  first  unites  with  the  sacrum  instead  of  with  the  others. 

The  Atlas. — The  atlas  is  almost 
wholly  formed  from  two  centres  which 
appear  in  the  seventh  week  of  fcetal  life 
in  the  root  of  the  posterior  arches  ;  from 
these  points  ossification  spreads  most 
rapidly  backward.  In  the  course  of  the 
first  year  a  centre  is  found  in  the  middle 
of  the  anterior  arch.  The  lateral  masses 
meet  behind  in  the  fourth  year  and  join 
the  median  anterior  nucleus  in  the  fifth. 
Sometimes   the   union   of   the  posterior 

arches  does  not  OCCUr.     The  anterior  nu-        Unique  case  of  absence  of  the  anterior  arch  of  the  atlas. 

cleus  may  be  absent,  and  the  front  arch 

may  show  a  median  suture  or  be  represented  by  ligament  or  cartilage.  In  one  in- 
stance the  anterior  arch  was  wholly  wanting,  the  lateral  masses  being  fastened  to  the 
odontoid  by  ligament1  (Fig.  161). 

The  Axis. — The  ossification  of  the  axis  begins  by  two  lateral  points  appearing 
by  the  eleventh  week.  The  median  one,  which  does  not  come  till  the  fifth  month, 
is  at  first  double,  but  the  two  points  speedily  fuse.  At  about  the  same  time  two 
nuclei  appear  side  by  side  in  the  odontoid  process,  which  join  together  before  birth, 
leaving  a  space  between  them  at  the  tip.  This  may  be  closed  by  the  extension  of 
ossification,  or  a  centre  may  appear  in  it  at  the  second  year,  which  fuses  by  the 
twelfth.  The  piece  thus  formed  has  been  held  to  represent  the  epiphyseal  plate  for 
the  top  of  the  atlas.  The  odontoid  process  joins  the  body  at  the  periphery,  the  union 
beginning  in  the  third  year  and  being  complete  a  year  or  two  later ;  a  piece  of  car- 
tilage in  the  middle  of  the  juncture  is  said  to  persist  under  the  odontoid  until  old 
age.  Very  rarely  the  odontoid  remains  distinct.  The  arches  join  the  body  in  the 
third  year,  and  usually  meet  behind  at  the  same  time ;  the  latter  union,  however, 
may  be  delayed. 

Variations  of  the  Vertebrae. — The  commonest  and  most  interesting  variations  are  those 
of  number.  These  are  very  frequent  in  the  coccyx,  since  there  are  originally  more  elements  than 
persist,  and  indeed  we  are  not  sure  even  of  the  normal  number  in  this  bone.  Numerical  varia- 
tions are  also  often  observed  in  the  sacral,  less  so  in  the  lumbar,  still  less  so  in  the  thoracic,  and 
extremely  rarely  in  the  cervical  region.  The  number  of  vertebras  above  the  sacrum  (twenty- 
four)  is  usually  unchanged,  but,  owing  to  differences  in  development  of  the  costal  element,  one 
region  is  not  rarely  increased  or  diminished  at  the  expense  of  the  next  one.  Thus  the  very  com- 
mon condition  of  six  lumbar  vertebrae  is  due  to  the  want  of  development  of  the  costal  element 
(the  rib)  of  the  last  thoracic,  and  implies  only  eleven  vertebrae  in  that  region.  Conversely,  thir- 
teen thoracics  imply  an  undue  development  of  the  costal  element  of  the  first  lumbar,  and  con- 
sequently only  four  lumbar  vertebrae.  Often  the  costal  element  of  the  last  cervical  is  free  and 
over-developed,  making  a  cervical  rib.  But  even  if  this  be  large  enough  to  reach  the  sternum, 
which  is  exceedingly  rare,  the  number  of  cervical  vertebrae  is  usually  considered  unchanged. 
Other  changes  are  due  to  variations  in  development  of  the  costal  element  in  the  last  lumbar 
and  the  first  sacral.     Transitional  forms  are  here  very  frequently  met  with.     The  last  lumbar 

1  Dwight :  Journal  of  Anatomy  and  Physiology,  vol.  xxi.,  1887. 


132  HUMAN    ANATOMY. 

may,  by  an  excessive  growth  of  these  elements,  become  sacralized,  articulating  more  or  less  per- 
fectly with  the  ilium,  and,  conversely,  the  first  sacral  may  have  almost  freed  itself  from  those 
below  it.  Thus  we  may  find  a  partially  sacralized  vertebra,  which  may  be  either  the  twenty-fifth 
or  the  twenty-fourth.  It  often  happens,  particularly  in  the  latter  case,  that  a  vertebra  appears  to 
be  a  first  sacral  on  superficial  examination,  which  is  found  to  have  little  or  nothing  to  do  in  form- 
ing the  articular  surface,  in  which  case  it  is  not  a  true  sacral,  for  the  first  sacral  is  the  fulcralis 
which  has  the  largest  surface  for  the  joint  with  the  ilium.  A  false  promontory  may  coexist  with 
the  normal  one.  This  is  probably  most  frequent  when  the  twenty-fourth  vertebra  is  partly 
sacralized.  Any  of  the  preceding  peculiarities  may  be  unilateral,  so  that  sometimes  a  vertebra 
may  seem  from  one  side  to  belong  surely  to  one  region,  and  equally,  surely  to  the  other  region 
when  seen  from  the  opposite  side. 

There  is,  however,  another  set  of  variations  in  which  the  number  of  presacral  vertebra?  is 
increased  or  diminished.  There  may  be,  for  instance,  one  thoracic  or  one  lumbar  vertebra  too 
many  or  too  few,  without  any  compensatory  change  in  the  next  region.  In  these  cases,  more- 
over, the  terminal  vertebrae  of  the  region  may  be  very  nearly  typical  ones,  and  sometimes  even 
the  size  of  the  vertebrae  will  be  modihed  so  as  to  give  the  region  its  approximate  relative  length. 
Similar  changes  may  be  found  in  the  neck,  but  they  are  exceedingly  rare. 

Variations  of  either  kind  are  likely  to  have  an  effect  on  the  column  as  a  whole  ;  thus,  ii 
there  be  a  large  cervical  rib  the  last  thoracic  rib  is  likely  to  be  small,  or  if  the  first  rib  is  rudi- 
mentary the  last  is  apt  to  be  large.  It  follows  that  the  thorax  seems  to  be  in  certain  cases 
moved  upward  or  downward  ;  this  change  may  occur  on  one  side  only. 

Rosenberg's  theory,  formerly  much  in  vogue,  is  that  there  are  opposite  tendencies  at  the 
two  ends  of  the  spine.  At  the  upper  there  is  a  tendency  for  the  cervical  region  to  encroach  on 
the  thoracic,  and  at  the  lower  for  each  of  the  regions  to  encroach  on  the  one  above  it.  Such 
changes  he  considers  progressive.  On  the  other  hand,  the  opposite  movement  by  which  the 
thorax  encroaches  on  the  neck  or  loins  is  considered  reversive.  Rosenberg  has  described  a 
spine  which  he  considers  archaic,  in  which  there  are  two  extra  presacral  vertebrae  and  fifteen 
pairs  of  ribs,  the  first  being  cervical.  There  are  two  spines  in  the  Warren  Museum  with  a  simi- 
lar number  of  presacrals  in  which  the  last  is  sacralized  on  one  side.  As  to  the  way  in  which 
anomalies  of  the  lower  part  of  the  spine  come  about,  Rosenberg1  thinks  he  has  shown  that  in 
the  course  of  development  the  sacrum  is  composed  of  vertebrae  placed  farther  back  than  the 
permanent  ones,  and  that  the  ilium  enters  into  connection  with  vertebrae  more  and  more  ante- 
rior. As  new  ones  join  it  above  former  ones  become  detached  from  it  below.  If  it  does  not 
make  the  usual  progress  the  spine  is  archaic,  having  too  many  presacrals  ;  if  it  goes  too  far  the 
spine  is  of  the  future.  Rosenberg's  theory  has  been  overthrown  by  Bardeen,2  who  has  shown 
that  the  original  position  of  the  ilium  is  opposite  the  superior  part  of  the  lumbar  region  and 
that  it  travels  tailwards.  Having  joined  a  vertebra  at  the  fifth  week,  it  never  leaves  it.  At  this 
early  time  the  thoracic  vertebra  are  differentiated.  The  author3  and  Fischel*  believe  that 
numerical  variation  is  the  result  of  an  error  in  segmentation. 

A  want  of  development  of  the  bodies,  which  may  be  only  half  the  normal  height,  is  found 
almost  exclusively  in  the  lumbar  region.  We  have  seen  (apparently  congenital)  fusion  of  the 
lumbar  bodies  while  all  the  arches  were  present,  but  three  of  them  crowded  together.  The 
separation  of  the  pedicles  of  the  fifth  lumbar  from  the  body  is  a  very  rare  anomaly  among 
whites,  but  not  among  American  aborigines. 

ARTICULATIONS    OF    THE   VERTEBRAL    COLUMN. 
The  ligaments  connecting  the  segments  of  the  spine  may  be  divided,  according 
to  the  parts  of  the  vertebra?  which  they  unite,  into  two  groups  : 
i.   Those  connecting  the  Bodies  of  the  Vertebrae  ; 
2.   Those  connecting  the  Laminae  and  the  Processes. 

LIGAMENTS  CONNECTING  THE  BODIES. 
Intervertebral  Disks5  (Figs.  162,  163). — These  form  a  series  of  fibro-carti- 
lages  interposed  between  the  bodies  of  the  vertebrae,  forming  about  one-fourth  of  the 
movable  part  of  the  spine  and  adding  greatly  to  its  strength.  They  are  developed, 
like  the  bodies,  around  the  notochord,  persisting  parts  of  this  structure  forming  a 
central  core  to  each  disk.  The  outer  part  of  the  disks  consists  of  oblique  layers  of 
fibres,  slanting  alternately  in  opposite  directions,  some  almost  horizontal,  which  hold 
the  vertebral  bodies  firmly  together  ;  the  centre  of  the  disks  is  occupied  by  a  space 
containing  fluid  in  the  meshes  of  a  yellowish  pulp.6  This  central  core  is  strongly 
compressed,  so  as  practically  to  be  a  resistant  ball  within  the  more  yielding  fibro- 
cartilaginous socket.  The  proportion  of  the  disks  to  the  vertebral  bodies  varies  in 
the  different  parts  of  the  spine.  They  are  absolutely  largest  in  the  lumbar  region, 
but  relatively  in  the  cervical.      For  many  reasons  it  is  difficult  to   reckon  the  per 

'Morph.  Jahrbuch,  Bd.  i.  and  xxvii.  4  Anatomische  Hefte,  No.  95,  1906. 

2  Anat.  Anzeiger,  Bd.  xxv.,  1904,  and  American  Journal  of  Anatomy,  vol.  iv.,  1905. 

3Dwight :  Memoirs  Boston  Society  of  Nat.  Hist.,  vol.  v.,  1901. 

5Fibrocartilagines  intervertebrales.     ''  Nucleus  pulposus. 


LIGAMENTS    OF    THE    SPINE. 


133 


Fig.  162. 

verse  ligament 


centage  very  accurately,  and  there  is  much  variation.  The  following  proportions 
are,  therefore,  only  approximate.  The  disks  form  in  the  cervical  region  forty  per 
cent.,  in  the  thoracic,  twenty  per  cent.,  and  in  the  lumbar,  thirty-three  per  cent,  of 
the  length  of  the  spine. 

Anterior  and  Posterior 
Common  Ligaments. — The 
bodies  are  connected  by  short 
fibres  surrounding  the  disks, 
and  by  long  bands  which  are 
only  partially  separable  from 
the  general  envelope.  The  an- 
terior common  ligament1  (Figs. 
163,  165)  begins  at  the  axis 
and  extends  to  the  sacrum.  It 
consists  of  shorter  and  longer 
fibres  blending  with  the  peri- 
osteum and  springing  from  the 
edges  of  the  vertebra?'  and  from 
the  disks,  to  end  at  similar 
points  on  the  next  vertebra,  or 
on  the  second,  third,  fourth,  or 
fifth.  The  borders  are  not 
sharply  defined.  The  posterior 
common  ligament'1  (  Fig.  164) 
is  a  much  more  distinct  struc- 
ture. It  arises  from  the  back 
of  the  body  of  the  axis,  re- 
ceiving fibres  from  the  occipito- 
axial  ligament,  and  runs  to  the 
sacrum.  It  also  is  attached 
to  the  disks  and  the  edges  of 
the  bodies,  but  possesses  a  dis- 
tinct margin,  which,  except  in 
the  neck,  expands  laterally 
into  a  series  of  points  at  the 
intervertebral  disks.  It  stands 
well  out  from  the  middle  of 
the  bodies,  bridging  over  the 
veins  of  the  larger  ones. 

LIGAMENTS  CONNECT- 
ING THE  LAMINAE  AND 
THE    PROCESSES. 

The  articular  processes 
(Fig.  165)  are  coated  with 
hyaline  articular  cartilage  and 
surrounded  by  loose  capsules, 
with  which,  especially  in  the 
thorax,  the  ligamenta  subflava 
are  inseparably  connected,  pre- 
venting by  their  tension  the 
occurrence  of  folds. 

The  ligamenta  subflava3  (Fig.  163)  are  elastic  membranes  of  considerable 
strength  connecting  the  laminae  from  the  axis  to  the  sacrum.  They  are  particularly 
developed  in  the  lumbar  region.  As  just  mentioned,  they  encroach  on  the  side  of 
the  capsules  towards  the  canal.  They  also  extend  a  short  distance  under  the  spinous 
processes. 

The  supraspinous  ligament  (  Figs.  162,  163)  extends  as  a  well-marked  cord 

1  Lig.  longitudinalc  anterius.     -  Lig,  longitudinalc  posterius.     3  Ligg.  flava. 


section  of  upper  half  of  spii 


134 


HUMAN    ANATOMY. 


along  the  tips  of  the  spines  from  the  last  cervical  to  the  sacrum.  The  interspinous 
ligaments  are  membranes  connecting  the  spinous  processes  between  the  tips  and 
the  laminae,  extending  from  the  ligamenta  subflava  to  the  supraspinous  ligament. 


Tenth  thoracic  vertebra 


Ligamentum  subflavum 


Intervertebral  foramen 


First  lumbar  vertebra 


Posterior  common  ligament 


Intervertebral  disk 


Anterior  common  ligament 


Supraspinous  ligament 


Fifth  lumbar  verteb: 


First  sacral  vertebra 


Fifth  lumbar  spine 


First  coccygeal  vertebr 


Median  section  of  lower  half  of  spine. 


The  ligamentum  nuchae  (Fig.  166)  represents  in  the  neck  a  modification  of 
the  two  last-mentioned  ligaments.      It  is  a  vertical  curtain  reaching  from  the  extern 


LIGAMENTS    OF    THE    SPINE. 


135 


Cut  surface  of 
pedicle 


nal  occipital  protuberance  to  the  spine  of  the  seventh  cervical,  separating  the 
muscles  of  the  two  sides.  The  free  border  is 
continuous  with  the  supraspinous  ligament,  but, 
instead  of  touching  the  cervical  spines,  it  lies 
in  the  superficial  layer  of  muscles,  and  is  rein- 
forced below  by  radiating  fibres  from  each  of  the 
spinous  processes  of  the  cervical  region.  It  is 
inseparably  blended  with  the  origin  of  the  trapezii 
and  with  the  fasciae  between  the  muscular  layers, 
especially  with  that  covering  the  semispinalis  and 
the  short  suboccipital  muscles.  In  the  region  of 
the  axis  it  is  a  thick  median  membrane  ;  in  the 
lower  cervical  region  it  is  of  little  importance. 
In  man  it  contains  but  a  small  proportion  of  elas- 
tic fibres,  in  marked  contrast  to  what  is  found 
in  many  quadrupeds  in  which  the  structure  con- 
sists principally  of  elastic  tissue,  since  in  these 
animals  the  ligamentum  nuchas  forms  an  important 
organ  for  the  support  of  the  head  at  the  end  of 
the  horizontal  vertebral  axis. 

The    intertransverse    ligaments    (Fig. 
162)  are  trifling  collections  of  fibres  between  the 
transverse  processes,   although   occasionally   distinct  round   cords   in   the  thoracic 
region. 

Fig.   165. 

Anterior  occipito-atlantal  ligament 


Mastoid  process 


Lateral  occipito-atlantal 
ligament 


Anterior  tubercle  of  atlas 


Posterior  surface  of  bodies  of  vertebrae 
shown  after  removal  of  arches  by  cutting 
through  the  pedicles. 


Atlanto-axial  ligament  and  joint 


Anterior  common  ligament- 


Anterior  ligaments  of  upper  end  of  spine. 


ARTICULATIONS    OF    THE    OCCIPITAL    BONE,    THE    ATLAS,    AND 

THE    AXIS. 

The  arrangement  here  differs  in  some  points  considerably  from  that  of  the  rest 
of  the  spine  in  order  to  provide  for  the  security  and  the  free  movement  of  the  head. 
The  ligaments  effecting  this  union  consist  of  three  groups  : 
1.   Those  connecting  the  Atlas  and  the  Axis,  including  the 

Anterior  Atlanto-Axial  ;  Transverse  ; 

Posterior  Atlanto-Axial  ;  Two  Capsular. 


J36 


HUMAN    ANATOMY. 


2.  Those  connecting  the  Occipital  Bone  and  the  Atlas,  including  the 

Anterior  Occipito-Atlantal  ;  Posterior  Occipito-Atlantal  ; 

Accessory  Occipito-Atlantal  ;  Two  Capsular. 

3.  Those  connecting  the  Occipital  Bone  and  the  Axis,  including  the 

Lateral  Odontoid  or  Check  ;  Middle  Odontoid  ; 

Occipito- Axial. 

The  important  peculiarities  are  the  odontoid  and  the  transverse  ligaments. 

The  odontoid,  or  check  ligaments1  (  Fig.  168),  are  two  strong,  symmetrical 

bundles  of  fibres  extending  from  the  slanting  surface  on  each  side  of  the  top  of  the 

odontoid  process  outward  and  a  little  upward  to  a  roughness  on  the  inner  side  of 

each  occipital  condyle.      Some  fibres  pass  directly  across  from  one  condyle  to  the 


Ligamentum  nuch 


Trapezius  muscl 


Ligamentum  nucha? 


Posterior  occipito-atlantal 
ligament 


Posterior  atlanto-axial 
ligament 


Ligaments  of  back  of  neck. 


other.  These  are  occasionally  collected  into  a  distinct  round,  glistening  bundle. 
The  space  above  the  odontoid  process,  between  it  and  the  basilar  process,  is  oc- 
cupied by  a  mass  of  dense  fibrous  tissue  reaching  to  the  anterior  occipito-atloid 
ligament,  in  the  midst  of  which  is  a  more  or  less  distinct  median  band  connecting 
these  parts,  the  middle  odontoid  ligament.2  A  sicpra-odontoid  bursa  may  be 
developed  in  this  tissue.3 

The  transverse  ligament'  (Figs.  167,  168)  of  the  atlas  is  a  strong  band 
passing  between  the  tubercles  on  the  inner  side  of  each  lateral  mass  of  the  atlas.  It 
does  not  run  straight,  but  curves  backward  around  the  odontoid,  from  which  it  is 
separated  by  a  bursa.  A  band  from  the  middle  of  the  transverse  ligament  passes 
upward  to  the  cerebral  side  of  the  basilar  process,  and  another  downward  to  the 
body  of  the  axis,  so  that  the  whole  structure  is  called  the  cruciform  ligament.-1 
3Trolard  :  Journ.  de  l'Anat.  et  de  la  Physiol.,  1897. 

1  Ligg.  alaria.     -  Lig.  apicis  dentis.     4  Lig.   transversum   atlantis.     5  Lig   cruciatum  atlantis. 


OCCIPITO-SPINAL    LIGAMENTS. 


137 


Another  bursa  lies  between  the  odontoid  and  the  anterior  arch  of  the  atlas.  The 
transverse  ligament  and  the  two  check  ligaments  are  in  series  with  the  interarticular 
ligaments  oi  the  heads  of  the  ribs. 

The  other  ligaments  of  this  region  are  in  the  main  simple  membranes  connect- 

Fig.  167. 


Upper  end  of  occipito-axial  ligament 


Lateral  odontoid  ligament 

Occipito-atlantal  joint 


Cruciform  ligament 


Atlanto-axial  joint 


Fig.  1 


Front  of 
foramen 
magnui 


Lateral  odontoid 
gament 


-Occipito-axial  ligament,  fused  with  dura, 
turned  down 

Back  of  occiput  and  arches  removed  ;  occipito-axial  ligament  cut  and  turned  down. 

ing  neighboring  parts.  The  anterior  occipito-atlantal  ligament '  (  Fig.  165  ) 
extends  between  the  front  of  the  foramen  magnum  and  the  anterior  arch  of  the 
atlas  ;  the  anterior  atlanto-axial  (Fig.  165)  is  in  serial  continuation  with  it.  A 
distinct  rounded,  raised  band,  the  accessory  occipito-atlantal,  passes  in  the 
median  line  from  the  under  side  of  the 
occiput  to  the  front  tubercle  of  the  atlas 
(Fig.  165),  and  thence  to  the  body  of  the 
axis,  where  it  joins  the  anterior  common 
ligament  of  the  spine. 

The  occipito-axial  ligament2  {appa- 
ratus ligamentosus)  (Fig.  167)  descends  in- 
side the  spinal  canal  from  the  basilar  process 
to  the  body  of  the  axis,  where  it  joins  the 
posterior  common  ligament  and  completely 
conceals  the  odontoid  process  and  its  special 
ligaments. 

The  posterior  occipito-atlantal3  and 
the  posterior  atlanto-axial  ligaments* 
lie  in  the  region  of  the  arches  (Fig.  166).  The 
former  extends  between  the  posterior  border 
of  the  foramen  magnum  and  the  arch  of  the 
atlas  ;  the  latter  between  the  arch  of  the 
atlas  and  that  of  the  axis.  These  are  in  series  with  the  ligamenta  subflava,  but  differ 
from  them  in  being  non-elastic.  In  the  former  of  these  membranes  there  is  an 
opening  just  behind  the  facets  on  the  atlas  for  the  condyles,  bridged  over  by  a  band, 
for  the  entrance  of  the  vertebral  artery. 

nbrana  atlantonccipit;ilis  posterior.     4  Membrana 


Posterior  surface  of  odontoid  process  shown  by 
oval  of  middle  of  transverse  ligament;  basilar 
ress  is  thrown  strongly  upward. 


138 


HUMAN    ANATOMY. 


Synovial  joints,  the  shapes  of  which  are  described  with  the  bones,  exist  be- 
tween the  occipital  bone  and  the  atlas  and  between  the  atlas  and  the  axis.  The 
capsule  of  the  upper  joint  is  very  thick,  especially  behind,  where  it  is  continuous 
with  the  posterior  occipito-atloid  ligament.  The  capsule  surrounding  the  articular 
surfaces  of  the  atlas  and  axis  is  strengthened  posteriorly  by  a  bundle  running  upward 
and  outward  from  the  axis. 

Fig.  169. 

posterior  tubercle  of  atlas 
Spinal  cord 


Posterior  bursa 


Vertebral  artery  cut  obliquely 


Apparatus  ligamento 


Section  of  odontoid  proce 
Transverse  section  of  spine  passing  through  atlas  and  odontoid  process 


Anterior  bursa  Transverse  ligament 
Anterior  tubercle  of  atlas 


THE   SPINE  AS   A  WHOLE. 

Anterior  Aspect  (Fig.  170). — The  bodies  enlarge,  in  the  main,  regularly 
from  above  downward.  This  progression  is  interrupted  only  by  a  slight  decrease 
from  the  first  to  the  fourth  thoracic.  In  the  cervical  region  the  origin  of  the  costal 
elements  from  the  sides  of  the  bodies  gives  the  latter  a  false  appearance  of  breadth. 
The  middle  of  the  thoracic  region  is  particularly  prominent  in  front,  owing  in  part 
to  the  aortic  depression  on  the  left.  A  slight  curve  to  the  right  in  this  region  is 
generally  seen  ;  it  is  probably  attributable  to  this  cause. 

Posterior  Aspect  (Fig.  170). — A  deep  gutter  extends  on  each  side  of  the 
spinous  processes,  bounded  externally  in  the  neck  and  loins  by  the  articular  pro- 
cesses and  in  the  back  by  the  transverse.  In  the  latter  region  the  spines  which  are 
subcutaneous  are  often  deflected  from  the  median  line,  and  may  be  arranged  in  zig- 
zag. The  laminae  completely  close  the  spinal  canal  in  the  convex  thoracic  and 
sacral  regions,  while  it  is  left  open  in  the  neck  and  loins,  except  during  extension  of 
the  former. 

Lateral  Aspect  (Fig.  171). — The  profile  view  shows  best  of  all  the  increase  in 
the  importance  of  the  bodies  from  above  downward,  and  coincidently  with  this  the 
gradual  moving  backward  of  the  intervertebral  foramina.  These  increase  greatly  in 
size  from  the  lower  part  of  the  thoracic  region. 

The  Curves. — The  curve  of  the  spine  is  necessarily  an  arbitrary  one,  since  it 
varies  not  only  in  individuals  and  according  to  age,  sex,  and  occupation,  but  also 
with  position  and  the  time  of  day,  being  longer  when  lying  than  standing,  and  after 
a  night's  rest  than  after  a  day's  work.  The  difference  occasioned  by  position  occurs 
especially  in  youth,  when  it  may  amount  to  half  an  inch  or  more.  It  is  of  little 
consequence  after  middle  age.  Bearing  these  variations  in  mind,  the  following  guide 
to  the  curve,  suggested  by  Humphry,  may  be  accepted  :  a  line  dropped  from  the 
middle  of  the  odontoid  process  passes  through  the  middle  of  the  body  of  the  second 
thoracic,  that  of  the  twelfth  thoracic,  and  the  anterior  inferior  angle  of  the  fifth 
lumbar.  Henle  divides  the  spine  into  four  quarters  ;  and  although  this  method  has 
the  defect  of  using  the  unreliable  pelvic  section,  it  very  often  proves  remarkably 
correct.  Thus,  if  we  continue  Humphry's  line  to  the  level  of  the  tip  of  the  coccyx, 
the  middle  point  is  opposite  the  eleventh  thoracic,  the  end  of  the  first  quarter  oppo- 
site the  lower  border  of  the  third  thoracic,  and  that  of  the  third  quarter  opposite 
the  lower  edge  of  the  fourth  lumbar. 

The  development  of  the  curves  can  hardly  be  said  to  have  begun  at  birth.      At 


THE   SPINE   AS   A   WHOLE. 
Fig.  170. 


139 


Coccyx 
Anterior  and  posterior  views  of  adult  spin 


140 


HUMAN    ANATOMY. 


Fig.  171. 


that  age  the  infant's  spine  presents  in  front 
one  general  concavity,  slightly  interrupted 
by  the  promontory  of  the  sacrum.  The  liga- 
mentous spine,  containing  little  bone,  is  ex- 
ceedingly flexible  in  any  direction  :  the  atlas 
can  be  made  to  touch  the  sacrum.  It  is 
more  accurate  to  say  that  the  general  axis  of 
the  spine  is  a  curved  one  than  that  any  per- 
manent or  fixed  curve  exists.  The  cervical 
curve  appears  as  the  infant  grows  strong 
enough  to  hold  up  its  head  ;  it  is  never, 
properly  speaking,  consolidated  (Syming- 
ton), since  it  is  always  obliterated  by  a 
change  in  the  position  of  the  head.  The 
lumbar  curve  appears  at  from  one  to  two 
years  when  the  child  begins  to  walk.  The 
mechanism  of  its  production  is  explained  as 
follows.  When  an  infant  lies  on  its  back  the 
thighs  are  flexed  and  fall  apart.  If  these  be 
held  together  and  pressed  forcibly  down,  the 
lumbar  region  will  spring  upward,  owing  to 
the  shortness  of  the  ilio-femoral  ligaments, 
which  bend  the  pelvis  and,  indirectly,  the 
spine.  The  psoas  muscles,  moreover,  act 
directly  on  the  spine.  When  the  child  first 
stands,  the  body  is  inclined  forward  ;  when 
the  muscles  of  the  back  straighten  it,  the 
lumbar  curve  is  produced  by  the  same  mech- 
anism, since  it  is  immaterial  whether  the  legs 
are  extended  on  the  trunk  or  the  trunk  on 
the  legs.  How  or  when  these  curves  be- 
come consolidated  is  very  difficult  to  deter- 
mine. The  influence  of  differences  in  thick- 
ness of  the  front  and  back  of  the  various 
bodies  and  disks  is  inappreciable  in  the  neck  ; 
in  the  lower  part  of  the  back  and  in  the  first, 
and  perhaps  the  second,  lumbar  vertebrae  the 
height  is  greater  behind.  In  the  loins  the 
fifth  vertebra  is  much  thicker  in  front  and, 
above  it,  the  fourth  and  third  in  a  less  degree. 
The  intervertebral  disks  are  also  much  thicker 
in  front.  How  soon  actual  difference  in 
the  diameters  of  the  vertebras  appears  is  un- 
certain. A  child  of  about  three  shows  little 
of  it,  except  in  the  last  lumbar,  and,  accord- 
ing to  Symington' s  plates,  there  is  not  much 
more  difference  at  five  or  even  thirteen  years. 
It  is  certain  that  throughout  the  period  of 
growth  the  curves  can  be  nearly  or  quite 
effaced.  The  restraining  influences  are  the 
gradually  developing  differences  in  the  verte- 
bras and  the  disks,  the  effect  of  the  sternum 
and  the  ribs  on  the  thoracic  region,  the  pull 
of  the  elastic  ligaments  of  the  arches,  and 
perhaps,  above  all,  muscular  tonicity.  In 
the  latter  part  of  middle  age  the  curves  of 
the  back  and  loins  become  consolidated  ; 
this  is,  however,  distinctly  a  degenerative 
process. 


LENGTH    OF    PRESACRAL    REGIONS.  141 

Dimensions  and  Proportions. — The  length  and  the  proportions  of  the  dif- 
ferent presacral  regions  (including  the  intervertebral  disks),  measured  along  the  an- 
terior surface  of  the  spine,  have,  in  fifty  males  and  twenty-three  female  bodies,  been 
found  by  us  as  stated  below.  We  give  for  comparison  Ravenel's1  and  Aeby's'2  propor- 
tions combined.  The  former  measured  eleven  and  the  latter  eight  spines  of  each  sex. 
Cunningham's3  proportions,  from  six  male  and  five  female  spines,  are  also  added. 
In  the  proportions,  one  hundred  represents  the  total  presacral  length  along  the  curves. 

ACTUAL   LENGTH   OF   PRESACRAL  REGIONS   OF  SPINE. 

Male.  Female. 

Centimetres.  (Inches.)  Centimetres.  (Inches.) 

Neck 13.3  (  5.25)  12.1  (  4.75) 

Back 28.7  (11-31)  26.5  (10.44) 

Loins 199  (  7-82)  1S.7  (  7-38) 

61.9  (24-38)  57-3  (22.57) 

PROPORTIONS   OF   PRESACRAL   REGIONS   OF  SPINE. 

Male.  Female. 

(Dwight.)     (R.  &A.)     (Cunningham.)  (Dwight.)         (R.  &  A.)  (Cunningham.) 

Neck    ....      21.5  21.7  21.8  21.2  21.7  21.6 

Back    ....      46.3  46.7  46.5  46.1  46.5  45.8 

Loins   ....      32.2  3i-4  •     3i-7  32-7  32.4  32-8 

100. o  99-8  100. o  100.0  100.6  100.2 

Thus,  while  it  is  true  that  the  lumbar  region  is  relatively  longer  in  woman,  the 
difference  is  trifling. 

ABSOLUTE    AND     RELATIVE     LENGTH    OF     PRESACRAL     REGIONS     DURING 

GROWTH. 


At  birth 

At  birth 

At  birth 

One  month 

One  month 

Three  months 

Six  months 

Six  months 

Ten  months 

One  year,  boy 

One  year,  boy 

One  year  and  one  month,  boy- 
One  and  a  half  years,  girl  .  . 
One  and  a  half  years,  boy     . 

Two  years,  boy 

Two  years,  boy 

Three  years,  girl 

Four  years,  girl 

Four  and  a  half  years,  boy   . 

Five  years,  boy 

Five  years,  boy 

Six  years,  boy 

Nine  years,  girl 

Eleven  years,  boy 

Thirteen  years,  girl     .... 

Fifteen  years,  boy 

Sixteen  years,  girl 

Sixteen  years,  girl 

Seventeen  years,  girl  .... 


Ravenel. 

Ravenel. 

Ravenel. 

Chipault.1 

Chipault. 

Ravenel. 

Aeby. 

Aeby. 

Dwight. 

Chipault. 

Chipault. 

Chipault. 

Chipault. 

Chipault. 

Ravenel. 

Aeby. 

Dwight. 

Aeby. 

Chipault. 

Symington.6 

Ravenel. 

Symington. 

Ravenel. 

Aeby. 

Symington. 

Dwight. 

Aeby. 

Aeby. 

Dwight. 


Absolute  Length. 
(In  Millimetres.) 


Neck.      Back.      Loins.     Total 


5° 
40 
40 
40 
42 
50 
52.5 

53-5 

61 

60 

69 

67 

62 

68 

70 

79-5 

78 

79-9 

81 


85 

91 

95 
120 
100 
107.5 
113 


93 
100 

95 


100 
i°3 
107 
125 
121 
129 
11S 
130 
132 
140 

153-5 

162 

162 

174 

170 

180 

175 

195 

218.7 

220 

265 

221.8 

229.5 

250 


103-3 
102.8 
104 

135 

106 

150 

153-5 

136 

183 

151 

152.5 

161 


193 
190 

185 

165 

166 

208 

215-5 

221.5 

263 

253 

281 

264 

261 

279 

300 

33i 

34i 

345-2 

357-8 

354 

395 

361 

430 

463.2 

45i 

568 

472.8 

4S9-5 

524 


Neck.      Back.      Loins 


25-9 
21 

21.6 
24.2 

25-3 

24 

24-3 

24.1 

23.2 

23-7 

24-5 

25.2 

23-7 

24-3 

23-3 

24 

22.9 

23.1 

22.6 

22.5 

20.3 

22.2 

19.8 

19.7 

21-5 
21. 1 
21. 1 
2I.9 
21-5 


48.2 
52.6 
5i-3 

48.4 
48.1 
48.1 

47-5 
48.6 

47-5 

47.8 

45-9 

44.8 

49-7 

47-4 

46.7 

46.4 

47-5 

46.9 

48.9 

48 

45-6 

48.5 

45-4 

47.2 

48.7 

46.6 

46.9 

46.9 

47-7 


25-9 

26.3 

27 

27.4 

26.6 

27.9 

27.8 

27-5 

29.2 

28.5 

29.6 

30 

26.6 

28.3 

30 

29.6 

29.6 

29.9 

28.5 

29.4 

34-2 

29-3 

34-9 

33-t 

29.1 

32.2 

31-9 

3i-i 

3°-7 


1  Zeitschrift  fur  Anat.  und  Entwicklng 
3  Cunningham  :  Memoirs,  18S6. 
5  The  Anatomy  of  the  Child. 


1S76. 


:  Arch,  fur  Anat.  und  Entwicklng.,  1879. 
Revue  d'Orthopedie,  1S95. 


i42  HUMAN   ANATOMY. 

It  appears  from  the  above  that  in  the  adult  the  neck  is  a  little  more  than  one- 
fifth  of  the  movable  part  of  the  spine  and  the  loins  a  little  less  than  one-third.  In 
the  young  embryo  these  proportions  are  reversed,  but  by  the  time  of  birth  these  two 
parts  are  nearly  equal. 

Movements  of  the  Head. — Those  between  the  occiput  and  atlas  are  almost 
wholly  limited  to  flexion  and  extension,  of  which  the  latter  is  much  the  greater. 
This  is  in  part  due  to  the  reception  of  the  posterior  pointed  extremities  of  the  articu- 
lar processes  of  the  atlas  into  the  inner  parts  of  the  posterior  condyloid  fossae.  The 
anterior  occipito-atlantal  ligament  and  the  odontoid  ligaments  are  tense  in  extreme 
extension.  Inflexion  the  tip  of  the  odontoid  is  very  close  to,  if  it  does  not  touch, 
the  basilar  process.  The  range  of  both  these  motions  is  much  increased  by  the 
participation  of  the  cervical  region.  There  may  be  a  little  lateral  motion  between 
the  adas  and  head,  and  there  is  some  slight  rotation.  The  great  variation  of  the 
shape  of  the  articular  facets  makes  it  clear  that  both  the  nature  and  extent  of  the 
motions  must  vary  considerably. 

The  joint  between  the  atlas  and  axis  is  devoted  almost  wholly  to  rotation.  The 
transverse  ligament  keeps  the  odontoid  in  place,  and  the  very  strong  odontoid  liga- 
ments check  rotation  alternately.  The  head  is  highest  when  directed  straight  forward, 
but  the  joints  are  in  more  perfect  adaptation  if  one  condyle  be  a  little  anterior  to  the 
other,  and  if  the  atlas  be  slightly  rotated  on  the  axis.  This  position,  though  entail- 
ing a  slight  loss  of  height,  is  the  one  naturally  chosen  as  that  of  greatest  stability. 

Movements  of  the  Spine. — The  very  extensive  range  of  motion  of  the 
whole  spine  is  the  sum  of  many  small  movements  occurring  at  the  intervertebral 
disks.  The  whole  column  is  a  flexible  rod,  but  this  conception  is  modified  by  the 
following  peculiarities  :  (i)  the  motion  is  not  equally  distributed,  owing  to  the  vary- 
ing distances  between  the  disks  and  the  differences  of  thickness  of  the  disks  them- 
selves ;  (2)  the  bodies,  which  form  the  essential  part  of  the  rod,  are  not  circular,  so 
that  motion  is  easier  in  one  direction  than  in  another  ;  (3)  the  rod  is  not  straight 
but  curved  ;  (4)  the  kind  of  motion  is  influenced  by  the  articular  processes,  and 
varies  in  the  different  regions.  Other  modifying  circumstances  exist,  but  these  suf- 
fice to  show  that,  while  certain  general  principles  may  be  laid  down,  an  accurate 
analysis  of  the  spinal  movements  is  absolutely  impossible. 

The  incompressible  semifluid  centre  of  each  disk  has  been  compared  to  a  ball 
on  which  the  rest  of  the  disk  plays.  This  would,  therefore,  be  a  universal  joint 
were  there  no  restraining  apparatus.  The  motions  are  flexion  and  extension, — 
i.e. ,  angular  movements  on  a  transverse  axis  ;  lateral  motion, — i.e. ,  the  same  on 
an  antero-posterior  axis,  and  rotation  on  a  vertical  axis.  It  is  unlikely  that  any 
single  one  of  these  motions  ever  occurs  without  some  mingling  of  another.  Flexion 
and  extension  are  greatest  in  the  neck  and  loins.  Extension  is  more  free  than 
flexion  in  the  neck,  where  it  is  limited  by  the  locking  of  the  laminae,  which,  when 
the  head  is  thrown  as  far  back  as  possible,  gives  great  rigidity  to  the  neck.  In  the 
loins  and  in  the  region  of  the  last  two  thoracic  vertebra;  flexion  is  the  more  exten- 
sive. Before  the  spine  is  consolidated,  slight  flexion  is  possible  throughout  the  back, 
but  extension  is  very  quickly  checked  by  the  locking  of  the  laminae  and  spines. 
Lateral  motion  is  greatest  in  the  neck,  considerable  in  the  back  and  least  in  the 
loins.  Such  motion  is  always  associated  with  rotation,  which  is  most  free  in  the 
neck,  considerable  in  the  back,  and  very  slight,  at  most,  in  the  loins.  It  is  to  be 
remembered  that  motions  both  in  the  antero-posterior  and  in  the  transverse  plane 
are  checked  by  the  tension  of  the  ligaments  on  the  side  of  the  body  of  the  vertebra 
opposite  to  the  direction  of  the  motion,  and  also  by  the  resistance  to  compression 
of  that  side  of  the  intervertebral  disk  towards  which  the  motion  occurs.  The  liga- 
menta  subflava,  being  elastic,  tend  continually  to  bring  the  bones  back  into  position 
from  the  innumerable  slight  displacements  to  which  they  are  subject.  That  this 
replacement  is  effected  by  a  purely  physical  property  of  the  tissue  instead  of  by 
muscular  action  implies  a  great  saving  of  energy.  The  amount  of  all  motions,  and 
of  rotation  in  particular,  decreases  throughout  life  and  varies  much  in  individuals. 
According  to  Keen,  the  rotary  motion  between  the  atlas  and  the  axis  amounts  to 
twenty-five  degrees,  that  in  the  rest  of  the  neck  to  forty-five  degrees,  and  that  of  the 
thoracic  and  lumbar  regions  to  about  thirty  degrees  on  each  side. 


PRACTICAL    CONSIDERATIONS  :    THE    SPINE.  143 


PRACTICAL   CONSIDERATIONS. 

While  the  number  of  vertebrae  in  the  neck  is  almost  invariable  in  man  (and 
indeed  in  all  the  mammalia  except  the  sloth  and  the  sea-cow),  the  length  of  the 
cervical  region  varies  greatly  in  individuals.  As  it  is  apparently  shortened  during 
full  inspiration  and  lengthened  during  full  expiration,  so  an  actual  change  in  its 
length  is  associated  with  the  types  of  thorax  that  correspond  to  these  conditions. 
The  long  neck  is  therefore  found  in  persons  with  chests  that  are  flat  above  the 
mammas,  with  wide  upper  intercostal  spaces  and  narrow  lower  ones,  and  with  lack  of 
prominence  of  the  sternum.  These  conditions  are  often  associated  with  phthisical 
tendencies.  The  short  neck  is  found  in  persons  with  chests  of  the  reverse  type. 
Its  theoretical  association  with  apoplectic  tendencies  is  very  doubtful. 

The  remaining  variations  both  in  the  length  and  in  the  shape  of  the  vertebral 
column  are  closely  connected  with  corresponding  variations  in  its  curves. 

The  normal  curves  of  the  spine  are  four  :  the  cervical,  thoracic,  lumbar,  and 
pelvic  (or  sacro-coccygeal).  The  cervical  and  lumbar  are  concave  backward,  the 
thoracic  and  pelvic  convex  backward  (Fig.  171).  These  curves  are  produced  and 
kept  up  partly  by  the  twenty-three  intervertebral  disks.  They  are  altered  by  disease. 
An  additional  curve  not  uncommon  in  absolutely  healthy  persons  consists  in  a  slight 
deflection  of  the  thoracic  spine  to  the  right  ;  this  asymmetry  is  usually  ascribed  to  the 
greater  use  of  the  right  arm,  but  it  is  due  to  the  position  of  the  heart  and  the  aorta. 

All  the  vertebral  bodies  are  composed  of  cancellous  tissue,  which  is  more  spongy 
in  direct  proportion  to  the  size  of  the  vertebrae,  and  therefore  is  least  so  in  the  neck 
and  most  spongy  in  the  lumbar  region.  This  corresponds  with  the  greater  succu- 
lence and  elasticity  of  the  lower  intervertebral  disks  and  aids  in  minimizing  the  effect 
of  jars  and  shocks  such  as  are  received  in  alighting  from  a  height  upon  the  feet,  the 
lower  portion  of  the  column  of  course  receiving  the  greater  weight.  If  in  such  falls 
the  calcaneum  or  tibia  is  broken,  the  spine  usually  escapes  injury.  If  the  lower 
extremity  remains  intact,  the  safety  of  the  spine  depends  largely  upon  the  elasticity 
given  by  its  curves  and  by  the  disks. 

The  fact  that  the  bodies  have  to  bear  the  chief  strain  of  such  shocks  and  of 
extreme  flexion  and  extension,  the  most  usual  forms  of  spinal  injury,  serves,  together 
with  their  comparative  vascularity,  to  make  them  the  seat  of  tuberculous  infection 
when  it  invades  the  spine.  Their  spongy  texture,  once  they  are  softened  by  inflam- 
mation, leads  to  their  ready  disintegration  under  the  superincumbent  weight.  In 
the  neck  and  in  the  loins  the  process  may  at  first  merely  cause  a  straightening  of  the 
column,  the  normal  curves  being  concave  backward.  In  the  thoracic  region — the 
most  common  situation — it  soon  produces  kyphosis,  an  exaggerated  backward  curve, 
the  sharp  projection  of  the  spinous  processes  of  the  affected  vertebrae  causing  it  to 
be  known  as  "angular  curvature."  The  abscesses  which  result  from  caries  of  the 
vertebrae  are  governed  as  to  their  position  and  course  by  the  fasciae  and  muscles 
that  surround  them.      They  will,  therefore,  be  described  later  (page  643). 

The  suspension  of  the  whole  body  from  the  chin  and  occiput  separates  the  indi- 
vidual vertebrae  so  that  they  are  held  together  mainly  by  their  ligaments.  This 
obviously  relieves  or  removes  the  pressure  of  the  superincumbent  weight  on  the 
bodies  of  diseased  vertebrae.  The  relief  of  pressure  in  cases  of  thoracic  caries  is 
continued  by  the  use  of  appliances  which  transfer  the  weight  of  the  head  and 
shoulders  to  the  pelvis.  The  simplest  of  these  is  the  plaster  jacket.  For  cervical 
caries,  the  weight  of  the  head  is  transferred  to  the  trunk  beneath  the  level  of  disease 
by  means  of  an  apparatus  extending  from  above  the  head  to  a  band  (of  leather  or 
plaster)  encircling  the  chest. 

In  cases  of  kyphosis  corrected  by  the  method  of  "forcible  straightening"  it 
is  obvious  that  a  gap  proportionate  to  the  amount  of  bone  which  has  previously 
been  destroyed  must  be  left  between  the  bodies  of  the  diseased  vertebrae.  The 
ultimate  integrity  of  the  spinal  column  will  depend  upon  the  extent  and  character 
of  the  ankylosis  which  takes  place  between  the  separated  vertebrae.  It  is  asserted 
(Calot)  that  such  consolidation  does  occur  between  the  bodies  in  moderately  severe 
cases,  and  between  the  laminae,  transverse  processes,  and  spines  in  the  more  serious 


144  HUMAN    ANATOMY. 

ones.  It  has  been  shown  (Wullstein)  that  injury  to  the  dura  and  cord  and  even 
fracture  of  the  arches  and  processes  are  possible  concomitants  of  forcible  rectifica- 
tion of  kyphosis. 

If  the  curve  forward  of  the  lumbar  spine  is  exaggerated,  constituting  lordosis, 
it  is  usually  compensatory,  and  is  acquired  in  an  effort  to  maintain  the  erect 
position,  as  in  cases  of  high  caries,  great  obesity,  pregnancy,  ascites,  abdominal 
tumors;  etc. 

Scoliosis  or  lateral  curvature  commonly  results  from  faulty  positions  in  young, 
undeveloped  persons  with  weak  muscles,  as  school-girls,  who  sit  or  stand  in  such  atti- 
tudes that  the  muscles  are  relieved  and  the  strain  is  borne  by  insensitive  structures, 
like  ligaments  and  fasciae.  This  results  in  a  deflection  of  one  part  of  the  column — 
generally  the  thoracic — to  one  side,  usually  the  right,  and  the  formation  of  a  compen- 
satory curve  below,  and  occasionally  of  one  above  also.  The  bodies  of  the  affected 
vertebrae  are  at  the  same  time  rotated,  partly  by  the  action  of  the  slips  of  the  longis- 
simus  dorsi  which  are  attached  to  the  ribs  near  the  angles  and  to  the  tips  of  the  trans- 
verse processes  (Fig.  520),  so  that  in  advanced  cases  the  tips  of  the  spinous  pro- 
cesses of  the  affected  segments  turn  towards  the  concavity  of  the  curves,  while  the 
transverse  processes  of  the  vertebrae  involved  tend  to  lie  in  an  antero-posterior  plane 
and  can  often  be  felt  projecting  backward. 

A  further  explanation  of  the  causes  of  the  rotation  may  be  found  in  the  behavior 
of  a  straight  flexible  rod  under  similar  conditions.  Torsion  results  from  any  motion 
in  which  all  particles  of  a  straight  flexible  rod  do  not  move  in  parallel  columns. 
Therefore,  if  it  be  bent  in  two  planes  at  the  same  time  torsion  must  inevitably  occur. 
The  vertebral  column  being  bent  in  the  antero-posterior  plane  by  a  series  of  gentle 
curves,  lateral  bending  must,  therefore,  inevitably  lead  to  torsion,  since  it  means 
bending  in  two  planes. 

A  little  consideration  of  the  relations  of  the  spine  to  the  ribs,  scapula,  and  pelvis 
will  show  that  lateral  flexion  and  rotation  cannot  take  place  without  causing  {a)  sep- 
aration of  the  ribs  on  the  convex  side;  (6)  change  in  the  costal  angles,  making 
the  ribs  more  horizontal  on  the  convex  and  more  oblique  on  the  opposite  side  ;  (c) 
undue  prominence  of  their  angles  on  the  convex  side,  the  scapula  being  carried  upon 
them  so  that  it  also  is  more  prominent  ;  (d)  diminution  of  the  ilio-costal  space  on 
the  concave  side  ;  (e)  elevation  of  the  shoulder  on  the  convex  side  ;  (_/")  flatten- 
ing of  the  chest  in  front  on  the  convex  and  undue  prominence  of  the  chest  on  the 
opposite  side  ;  (_£-)  projection  of  the  ilium  on  the  concave  side.  Lateral  curvature 
with  these  secondary  deformities  may  also  be  produced  by  unequal  length  of  the 
lower  limbs,  one-sided  muscular  atrophy,  hypertrophy,  or  spasm,  sacro-iliac  disease, 
empyema,  and  asymmetry  of  either  the  pelvis  or  the  head. 

The  latter  factor  is  especially  interesting  from  an  anatomical  stand-point.  From 
what  has  been  said  (page  142)  of  the  position  of  greatest  stability  of  the  joints  be- 
tween the  head  and  the  atlas  and  the  latter  and  the  axis,  it  is  evident  that  the  position 
of  greatest  ease  is  with  the  head  slightly  turned  to  one  side,  the  condyles  of  the 
occiput  not  being  in  their  best  contact  with  the  superior  articular  surfaces  of  the 
atlas  when  the  head  is  held  straight,  but  rather  when  the  head  is  slightly  twisted 
(Dvvight).  The  effects  of  this  are  far-reaching.  First,  there  is  an  instinctive  effort 
to  get  the  eyes  on  the  same  plane  in  looking  forward,  which  is  presumably  the 
primary  cause  of  the  asymmetry  of  the  face  that  is  usually  found.  It  is  also  easier 
to  support  the  weight  in  standing  chiefly  on  one  leg,  hence  the  other  side  of  the 
pelvis  is  allowed  to  fall  so  that  the  lumbar  region  slants  away  from  the  supporting  leg. 
This  must  be  corrected  by  a  lateral  motion  of  the  spine  above  it,  and  as  this  is  not 
pure  but  mixed  with  rotation,  there  occurs  a  twist  in  the  spine  ;  one  shoulder  is  higher 
than  the  other  as  well  as  farther  forward.  In  healthy  persons  such  positions,  if  not 
maintained  too  long,  do  little  harm  ;  but  there  is  likely  to  be  some  spinal  asymmetry 
in  all,  and  there  is  the  danger  that  it  may  become  pronounced  and  fixed  in  the  weak. 

Sprains  of  the  spine  are  most  common  in  the  cervical  and  lumbar  regions  :  in 
the  former  because  of  the  greater  mobility  of  the  articulation  with  the  cranium,  and 
in  both  because  of  their  own  mobility,  the  greatest  degree  of  bending  in  an  antero- 
posterior direction  being  possible  in  those  two  segments  of  the  spine.  The  thoracic 
and  pelvic  curves  are  primary,   form  part  of  the  walls  of  the  thorax  and  pelvis, 


PRACTICAL    CONSIDERATIONS  :    THE    SPINE.  145 

appear  early,  and  are  chiefly  due  to  the  shape  of  the  vertebral  bodies.  The  cervical 
and  lumbar  curves  are  secondary,  develop  after  birth,  and  depend  mainly  on  the 
shape  of  the  disks.  Greater  mobility  would  naturally  be  expected  under  the  latter 
circumstances.  The  close  articulation  between  the  separate  vertebras  throughout 
the  whole  column,  while  it  renders  a  slight  degree  of  sprain  not  uncommon,  tends 
at  the  same  time  to  diffuse  forces  applied  to  the  spine  and  to  concentrate  them  within 
certain  areas.  These  areas  are  the  points  at  which  fixed  and  movable  portions  of  the 
spine  join  each  other,  as  in  the  neighborhood  of  the  atlanto-axial,  the  cervico-- 
thoracic,  and  the  dorso-lumbar  regions. 

If  the  force  is  sufficient  to  cause  an  injury  of  greater  severity  than  a  sprain 
it  is  apt  to  be  a  dislocation  or  a  fracture  with  dislocation  at  one  or  other  of  these 
localities.  The  latter  accident  is  usually  caused  by  extreme  flexion  of  the  spine,  and 
of  the  three  points  mentioned  is  most  often  found  in  the  segment  including  the 
lower  two  thoracic  and  the  upper  one  or  two  lumbar  vertebrae.  This  is  due  to  the 
fact  that  (1)  this  segment  has  to  bear  almost  as  much  weight  as  the  lumbar  spine, 
and  yet  its  vertebras  are  smaller  and  weaker.  (2)  The  transverse  processes  are 
short,  while  the  longer  ones  below,  together  with  the  crest  of  the  ilium  and  the  ribs 
above,  give  a  powerful  leverage  to  the  muscles  that  move  the  region  in  question. 
(3)  It  is  the  region  at  which  the  most  concave  part  of  the  thoracico-lumbar  curve  is 
found,  making  the  "hollow  of  the  back"  and  corresponding  to  the  "waist"  where 
the  circumference  of  the  trunk  is  smallest.  (4)  Its  nearness  to  the  middle  of  the 
column  enables  a  greater  length  of  leverage  to  be  brought  to  bear  against  it  than 
against  any  other  part.  (5)  The  different  segments  of  the  spine  above  it  are  com- 
paratively fixed  (Humphry).  These  anatomical  facts  account  for  the  frequency 
and  severity  of  the  injury  known  as  "fracture-dislocation"  in  this  region  as  a  result 
of  extreme  flexion. 

A  view  of  the  vertebral  column  from  behind  (Fig.  170)  serves  well  to  illustrate 
some  of  these  points. 

Pure  dislocations  are  rare,  but  are  more  frequent  in  the  upper  than  in  the  lower 
part  of  the  spine,  because  the  bodies  of  the  cervical  vertebrae  are  small,  and  the 
interlocking  of  the  articular  processes  is  less  firm  than  it  is  lower  in  the  column. 
The  vertebra  most  commonly  dislocated  is  the  fifth  cervical,  which  might  be  expected 
from  the  fact  that  in  the  neck  flexion  and  extension  are  freest  between  the  third  and 
sixth  vertebrae.  The  dislocation  is  usually  anterior, — that  is,  the  articular  process 
of  one  vertebra  slips  forward  and  falls  down  on  the  pedicle  of  the  vertebra  below, 
resting  in  the  intervertebral  notch, — this  accident  being  rendered  easy  by  the  com- 
paratively horizontal  position  of  the  articular  processes  in  the  cervical  region.  Such 
dislocation  is  practically  impossible  in  the  thoracic  or  lumbar  region  without  fracture, 
while  fracture  is  comparatively  rare  in  the  cervical  region.  The  lumen  of  the  spinal 
canal  may  be  but  little,  if  at  all,  invaded. 

As  to  reduction,  experiments  show  (Walton)  that  no  moderate  amount  of  exten- 
sion in  a  direct  line  would  raise  the  displaced  articular  processes  in  the  least  degree. 
It  was,  however,  found  easy  to  unlock  these  processes  by  retro-lateral  flexion,  bend- 
ing the  head  towards  the  side  to  which  the  face  was  already  turned,  an  inappreciable 
amount  of  force  being  necessary.      Rotation  into  place  completed  the  reduction. 

All  pure  dislocations  are  really  subluxations,  as  without  extensive  fracture  of 
the  processes  and  great  laceration  of  ligaments  a  complete  separation  of  the  articu- 
lar surfaces  of  two  adjoining  vertebrae  is  practically  impossible. 

Pure  fracture,  not  the  result  of  a  gunshot  wound,  is  rare.  If  from  flexion,  the 
fracture  involves  the  body  ;  if  from  direct  violence,  usually  the  laminae.  These  facts 
require  no  explanation. 

Dislocations  and  fractures  of  the  upper  two  cervical  vertebrae  are  especially 
serious  on  account  of  the  proximity  of  the  medulla  and  of  their  position  above  the  roots 
of  the  phrenic  nerve  and  of  the  nerves  supplying  the  external  muscles  of  respiration. 
If  the  accident  is  from  overflexion,  it  may  be  a  dislocation  between  the  occiput  and 
the  atlas,  as  it  is  there  that  the  movements  of  flexion  and  extension  of  the  head  take 
place.  If  it  arises  from  extreme  rotation,  and  especially  if  there  is  rupture  of  the 
check  ligaments,  it  may  be  a  dislocation  of  the  atlas  from  the  axis,  as  it  is  there  that 
the  rotary  movements  of  the  head  occur.      "  A  dumb  person  expresses  'yes'  at  the 


i46  HUMAN   ANATOMY. 

occipito-atloid  joint  and  'no'  at  the  atlo-axoid"  (Owen).  Painless  nodding  and 
rotation  of  the  head  aid,  therefore,  in  the  exclusion  of  the  occipito-atlantal  and 
atlanto-axial  regions  in  obscure  cases  of  high  caries. 

The  axis  is  more  spongy  than  the  atlas,  and  is  weakest  about  one  centimetre 
below  the  neck  of  the  odontoid  process,  and  this  is  one  of  the  most  frequent  seats 
of  fracture. 

In  fracture-dislocations,  which  constitute  from  seventy  to  eighty  per  cent,  of  se- 
vere spinal  injuries,  the  thoracico-lumbar  region  suffers  most  commonly  for  the  reasons 
above  stated.  The  almost  vertical  direction  of  the  articular  processes  of  the  thoracic 
vertebrae  causes  them,  when  flexion  is  extreme,  as  when  a  weight  has  fallen  on  the 
back,  to  be  frequently  fractured,  which,  together  with  the  accompanying  crushing 
of  the  vertebral  body  and  rupture  of  the  supra-  and  interspinous  ligaments  and 
the  ligamenta  subflava,  permits  the  immediate  sliding  forward  of  the  vertebrae  above 
the  crushed  one  and  the  compression  of  the  cord — often  its  practical  severance — 
between  the  anterior  edge  of  the  posterior  arch  of  the  upper  vertebra  and  the  poste- 
rior edge  of  the  body  of  the  lower  one. 

(For  the  resulting  symptoms,  see  section  on  Nervous  System,  page  1053. )  It 
may  be  mentioned  here  that  the  spinal  nerves  do  not  arise  from  the  cord  opposite 
the  vertebrae  after  which  they  are  named.  Their  regions  of  origin  may  briefly  be 
stated  as  follows  : 

( 1 )  Occiput  to  sixth  cervical  spine,  — eight  cervical  nerves. 

(2)  Seventh  cervical  to  fourth  thoracic  spine, — upper  six  thoracic  nerves. 

(3)  Fifth  to  tenth  thoracic  spine, — lower  six  thoracic  nerves.     • 

(4)  Eleventh  and  twelfth  thoracic  spines, — five  lumbar  nerves. 

(5)  First  lumbar  spine, — five  sacral  nerves. 

Landmarks. — To  fix  the  limits  of  the  spine  in  the  living,  draw  a  horizontal 
line  from  the  anterior  nasal  spine  to  the  lower  edge  of  the  external  occipital  pro- 
tuberance and  another  backward  from  the  top  of  the  symphysis  pubis.  Seen  from 
the  side,  the  top  of  the  spine  is  in  a  line  connecting  the  front  of  the  lobe  of  each  ear, 
passing  behind  the  neck  of  the  lower  jaw.  Frozen  sections  show  that  the  front  of 
the  vertebral  bodies  is  much  nearer  the  centre  of  the  body  than  one  is  prepared  to 
expect.  A  vertical  transverse,  or  frontal,  plane  through  the  thorax  at  its  greatest 
breadth  strikes  the  angle  of  the  jaw,  the  front  of  the  cervical  convexity  of  the  spine, 
and  cuts  the  body  of  the  fourth  lumbar   (Langer). 

The  relations  of  the  spine  anteriorly  are  considered  with  the  parts  in  front  of  it. 
The  parts  felt  from  the  surface  are  the  spinous  processes  and  some  few  of  the  trans- 
verse ones.  The  line  of  the  spines  is  a  good  example  of  the  general  rule  that 
prominences  on  the  skeleton  lie  in  hollows  in  the  flesh  ;  a  deep  furrow  between  the 
muscular  masses  marks  their  position. 

Palpation  of  the  normal  spine  with  the  soft  parts  in  place  gives  the  following 
information.  The  spine  of  the  second  cervical  can  be  felt  by  deep  pressure  a  little 
below  the  occiput.  The  short  spines  of  the  succeeding  vertebrae  are  made  out  with 
great  difficulty.  The  fifth  is  longer  than  those  just  above  it.  The  sixth  is  much 
longer  and  nearly  as  long  as  that  of  the  seventh.  The  name  vertebra  prominens 
conferred  on  the  seventh  is  misleading,  for  the  spine  of  the  first  thoracic  is  the  most 
prominent  in  this  region.  The  third,  fourth,  and  fifth  cervical  spines  recede  from 
the  surface  by  reason  of  the  forward  curve  of  the  cervical  segment  and  on  account 
of  their  shortness.  This  permits  of  free  extension  of  the  head  and  neck.  The  liga- 
mentum  nuchas  also  prevents  them  from  being  felt  distinctly.  The  sixth  and  seventh 
cervical  and  first  thoracic  are  easily  felt.  The  remainder,  lying  in  the  groove  caused 
by  the  prominence  of  the  erector  spinas  muscles,  can  usually  be  palpated  without 
much  difficulty. 

The  relative  sizes  vary  so  much  that  it  is  not  safe  to  identify  any  spine  in  this 
way.  If  the  whole  series  from  the  second  cannot  be  counted,  it  is  best  to  start  from 
the  fourth  lumbar,  which  is  on  a  level  with  the  highest  points  of  the  ilia.  Vertebrae 
can  also  be  identified  from  the  lower  ribs  by  the  relations  of  the  heads  to  the  bodies. 
The  relations  of  the  spinous  processes  to  the  body  vary.  Thus,  in  the  cervical 
region  the  first  five  spines  pass  nearly  straight  backward.  The  sixth  and  seventh, 
like  the  upper  two  or  three  thoracic  spines,  descend  a  little,  so  that  the  tip  is  opposite 


LANDMARKS    OF    THE    SPINE. 
Fig.  172. 


147 


Anterior  boundary  of  foran 
magnum 


Superior  laryngeal  opening 
Cricoid  cartilage 

Thyroid  gland 

Upper  border  of  manubrium 

Left  innominate  vein 

Innominate  artery 

Ascending  portion  of  aortic  arch 

Upper  border  of  body  of  sternum 

Section  of  right  lung 

Right  auricular  appendage 


Lower  border  of  body  of  sternum 
Diaphragm 


Lower  end  of  ensiform  cartilagi 
Liver 


Stomach 
Pancreas 


Duodenu 
Transverse  col< 


Sigmoid  fle 


Bladd. 
Symphysis  pub 


Medulla 

Posterior  boundary  of  foramen 
magnum 

Odontoid  process  of  axis 


Division  of  trachea 
Right  pulmonary  artery 
Left  auricle 


End  of  abdominal  aorta 
Left  common  iliac  vein 


Coccyx 

Seminal  vesicles 
Prostate 


Median  section  of  the  body  of  a  man  aged  twenty-one  years.     {After  Braune.) 


148  HUMAN    ANATOMY. 

to  the  body  next  below  it.  With  the  fourth  or  fifth  thoracic  they  point  much  more 
strongly  downward,  so  as  to  be  opposite  the  disk  below  the  succeeding  body.  This 
continues  to  the  tenth,  where  they  are  opposite  the  body  below.  In  the  loins  the 
spines  have  a  considerable  posterior  surface,  which  is  opposite  the  disk  and  the 
upper  part  of  the  body  below  it.  The  tips  of  the  spines  are  not  always  in  a  straight 
line,  but  sometimes  describe  a  zigzag.  The  transverse  process  of  the  atlas  can  be 
felt  below  the  tip  of  the  mastoid  process,  moving  with  the  head  when  the  latter  is 
turned.  The  transverse  processes  below  this  are  felt  with  great  difficulty  through 
the  muscles  of  the  side  of  the  neck.  Those  of  the  back  and  loins  are  too  thicklv 
covered  to  be  felt.  The  laminae  are  also  thickly  covered  with  muscles,  so  that  the 
operation  of  laminectomy  necessarily  involves  a  deep  wound,  and  in  the  thoracic 
region  this  difficulty  is  increased  by  the  backward  projection  of  the  ribs. 

As  landmarks  the  spines  of  the  vertebrae,  on  account  of  their  accessibility,  have 
great  value.  These  spines  have  the  following  relations.  The  fourth  cervical  spine 
corresponds  to  (i)  the  opening  of  the  larynx;  (2)  the  bifurcation  of  the  carotid 
artery,  and  hence  the  point  of  origin  of  both  the  external  and  internal  carotid 
arteries.  The  sixth  cervical  indicates  the  level  of  the  carotid  tubercle  (transverse 
process  of  the  sixth  vertebra)  and  the  entrance  of  the  vertebral  artery  into  the  bony 
canal.  The  seventh  cervical  spine  is  a  guide  to  ( 1 )  the  lower  border  of  the  cricoid 
cartilage  ;  the  lower  opening  of  the  larynx  and  the  beginning  of  the  trachea  ;  (2) 
the  lower  end  of  the  pharynx  and  the  upper  opening  of  the  oesophagus  ;  (3)  the 
crossing  of  the  omo-hyoid  over  the  common  carotid  ;  (4)  the  level  of  the  apex  of 
the  lung  and  to  the  summit  of  the  arch  of  the  subclavian  artery.  The  fourth  thoi-acic 
spine  corresponds  to  the  level  at  which  the  aorta  reaches  the  spinal  column,  the 
trachea  bifurcates,  and  posteriorly  the  apex  of  the  lower  lobe  of  the  lung  is  found. 
It  is  on  the  same  level  as  the  root  of  the  spine  of  the  scapula.  The  seventh  thoracic 
lies  on  a  level  with  the  inferior  angle  of  the  scapula.  The  eighth  thoracic  indicates 
the  lower  level  of  the  heart  and  that  of  the  central  tendon  of  the  diaphragm  and  the 
level  at  which  the  inferior  vena  cava  passes  through  the  diaphragm.  The  ninth  tho- 
racic marks  the  level  at  which  the  upper  edge  of  the  spleen  is  found  in  health,  and  at 
which  also  the  oesophagus  pierces  the  diaphragm.  The  tenth  thoracic  corresponds 
to  the  lower  edge  of  the  lung,  the  spot  at  which  the  liver  comes  to  the  surface  poste- 
riorly. The  spines  of  the  third  to  the  ninth  thoracic  correspond  to  the  heads  of  the 
fourth  to  the  tenth  ribs  respectively.  The  eleventh  thoracic  is  a  guide  to  the  normal 
situation  of  the  lower  border  of  the  spleen  and  to  the  upper  part  of  the  kidney. 
The  twelfth  thoracic  marks  the  lower  limit  of  the  pleura,  the  passage  of  the  aorta 
through  the  diaphragm,  and  the  situation  of  the  pyloric  end  of  the  stomach,  and 
is  on  a  level  with  the  head  of  the  last  rib.  The  first  lumbar  spine  is  on  the  line  of 
the  renal  arteries  and  the  pelvis  of  the  kidney.  The  second  lumbar  spine  corre- 
sponds to  (1)  the  termination  of  the  duodenum  and  the  commencement  of  the 
jejunum  ;  (2)  the  opening  of  the  ductus  communis  choledochus  into  the  intestine  ; 
(3)  the  lower  border  of  the  kidney  ;  (4)  the  lower  border  of  the  pancreas  ;  (5)  the 
upper  end  of  the  root  of  the  mesentery  ;  (6)  the  point  of  origin  of  the  superior 
mesenteric  artery  ;  (7)  the  commencement  of  the  thoracic  duct  ;  (8)  the  commence- 
ment of  the  vena  porta  ;  (9)  the  termination  of  the  spinal  cord  and  the  origin 
of  the  cauda  equina  ;  ( 10)  the  upper  end  of  the  receptaculum  chyli.  The  third 
lumbar  corresponds  to  the  levei  of  the  umbilicus  and  the  origin  of  the  inferior 
mesenteric  artery  ;  the  fourth  lumbar  spine  marks  the  point  of  bifurcation  of  the 
abdominal  aorta  into  the  two  common  iliac  arteries,  and  lies  on  a  level  with  the 
highest  part  of  the  ilium  ;  and,  finally,  the  fifth  lumbar  spine  is  a  little  below  the 
beginning  of  the  inferior  vena  cava. 

Direct  cocainization  of  the  spinal  cord  has  recently  been  employed  in  surgery  in 
operations  on  the  lower  abdomen,  pelvis,  and  lower  extremities.  The  injection  into 
the  subarachnoid  space  surrounding  the  cord  is  made  through  the  space  between 
the  fourth  and  fifth  lumbar  vertebra?.  To  find  this  space,  draw  a  line  connecting 
the  highest  points  of  the  crest  of  the  ilium  posteriorly.  This  will  pass  through  the 
spine  of  the  fourth  lumbar  vertebra.  The  point  for  injection  is  one  centimetre  below 
and  one  centimetre  to  the  outer  side  of  the  point  at  which  the  transverse  line  crosses 
the  vertebral  spine  in  the  median  line. 


THE  THORAX. 


The  thorax  is  that  part  of  the  body-cavity  separated  by  the  diaphragm  from 
the  abdomen  below,  but  without  complete  separation  from  the  neck  above.  Its 
bony  walls  are  formed  behind  by  the  thoracic  vertebra?,  at  the  sides  by  the  ribs,  and 
in  front  by  their  continuations,  the  costal  cartilages,  and  the  sternum. 

Fig.  173. 


<2%-^|> 


The  bony  thorax,  anterior  view. 

THE    RIBS. 

The  ribs,  arranged  as  twelve  pairs,  are  flat  bars  of  bone,  curved  and  twisted, 
which  are  attached  behind  to  the  spine  and  continued  in  front  by  the  costal  cartilages  ; 
they  form  the  greater  part  of  the  bony  walls  of  the  thorax.      The  first  seven  pairs, 

149 


i5o  HUMAN    ANATOMY. 

exceptionally  eight,  reach  the  sternum  through  their  cartilages  ;  hence  they  are  called 
sternal  ribs,1  as  distinguished  from  the  remaining  five  pairs  of  asternal  ribs.2  Each 
cartilage  of  the  next  three  joins  that  of  the  rib  above  it.  The  last  two  pairs  have 
the  cartilages  ending  free,  and  are  termed  floating  ribs.  Their  complicated  curves 
are  best  understood  by  studying  them  in  place.  Each  rib  (with  certain  exceptions 
to  be  detailed  later)  has  an  articular  surface,  the  head,  at  the  posterior  end  ;  followed 
by  a  narrower  neck,  succeeded  by  an  articular  facet  on  the  tubercle  which  rests  on 
the  transverse  process  of  the  vertebra.  The  first  rib  has  an  upper  and  a  lower 
surface,  an  outer  and  an  inner  border  ;  the  second  faces  in  a  direction  intermediate 
to  this  and  the  following,  which  have  an  outer  and  an  inner  surface,  an  upper  and  a 
lower  border.  They  are  placed  obliquely,  the  front  end  being  lower  than  the  hind 
one.  The  outline  of  the  ribs  is  irregular,  so  that  their  declination  is  not  due  wholly 
to  their  position,  but  in  part  also  to  their  shape.  Thus,  one  in  the  middle  of  the 
series  slants  a  little  downward  as  far  as  the  tubercle,  then  declines  more  sharply 
to  a  roughness  near  the  tubercle  known  as  the  angle,  and  thence  more  gradually 
to  the  end.  The  main  curve  of  such  a  rib  is  backward,  outward,  and  downward 
as  far  as  the  angle,  which  marks  a  rather  sudden  change  of  direction,  the  course 
changing  to  one  forward,  slightly  outward,  and  downward,  until,  as  it  reaches  the 
front  of  the  chest,  it  runs  forward,  downward,  and  inward.  The  external  surface 
is  vertical  at  the  back  and  side  and  slants  slightly  upward  in  front.  Bearing  the 
declination  of  the  rib  in  mind,  it  is  evident  that  to  accomplish  this  the  rib  must  be 
twisted  on  itself,  otherwise  the  upper  edge  would  project  in  front. 

Fig.  174. 

Articular  facets  for  bodies  of  vertebrae  > 


Articular  facet 


Right  fifth  rib  from  behind. 

The  head3  is  an  enlargement  at  the  posterior  end  and  on  the  outer  surface,  i.e. , 
the  one  farthest  from  the  cavity  of  the  chest.  It  has  an  articular  surface  at  the 
end  facing  inward  and  backward,  divided  into  an  upper  and  a  lower  facet,  each  for 
the  body  of  a  vertebra,  by  a  transverse  ridge,  whence  a  ligament  passes  to  the  inter- 
vertebral disk.  The  lower  facet  is  the  larger,  and  is  generally  concave  ;  the  upper 
is  nearly  plane.      The  head  increases  in  size  to  the  ninth  rib  and  then  lessens. 

The  neck  *  is  compressed  from  before  backward,  smooth  in  front  and  rough  for 
ligaments  behind.  The  upper  aspect  has  a  sharp  border,  the  crest?  for  the  superior 
costo-transverse  ligament.  The  neck  grows  slightly  longer  in  descending  the  series 
to  the  same  level.  The  crest  on  the  top  of  the  neck  is  most  developed  in  the  sixth, 
seventh,  and  eighth  ribs. 

The  tubercle  6  is  an  elevation  beyond  the  neck  on  the  posterior  surface  of  the 
rib,  bearing  internally  a  round  articular  surface  facing  backward  and,  in  most  cases 
downward,  to  rest  on  the  transverse  process  ;  beyond  the  articular  facet  is  a  rough 
knob  for  the  external  costo-transverse  ligament. 

The  shaft '  is  smooth  inside,  the  surface  being  continuous  with  that  of  the  neck. 
The  subcostal  groove*  for  the  intercostal  vein  is  best  marked  in  the  middle  ribs,  begin- 
ning at  the  tubercle  and  running  forward,  growing  fainter,  along  three-quarters  ot 
the  rib,  just  under  cover  of  the  lower  border.      The  outer  surface  is  rather  irregular. 

The  angle  9  at  which  the  shaft  changes  its  direction  is  marked  by  a  rough  line 
on  the  posterior  surface,  some  distance  beyond  the  tubercle,  receiving  muscles  from 
the  system  of  the  erector  spina?.      The  angle,  which  is  not  found  in  the  first  rib,  is 

Gestae   verae.      -  Costac    spuriae.      3Capitulum.     4Collum.     5  Crista    colli.     "Tubcrculum.     '  Corpus    costac.     s  Sulcus 
costalis.     9  Angulus   costac. 


THE    RIBS. 


151 


very  near  (one  centimetre  beyond,)  the  tubercle  in  the  second  ;  it  gradually  recedes 
from  the  tubercle,  being  in  the  ninth  and  tenth  about  five  centimetres  distant.  The 
angle  is  a  little  nearer  in  the  eleventh,  and  is  wanting  in  the  last.  The  twist  is 
greatest  from  the  sixth  to  the  ninth  rib.      Several  of  the  upper  ribs  present  near 


Fig.  175. 


Right  fifth  rib:  A,  under  surface;  B,  postero-lateral  aspect. 


the  middle  a  rough  impression  for  a  point  of  the  serratus  magnus.  The  upper 
border  of  the  shaft  is  thick  and  rounded  behind,  but  thin  near  the  front.  The  lower 
border  is  sharp  where  it  overhangs  the  subcostal  groove ;  less  so  in  front.  The 
anterior  end  of  each  rib  is  cupped  to  receive  the  costal  cartilage. 


152 


HUMAN    ANATOMY. 


The  ribs  increase  in  length  from  the  first  to  the  seventh  or  eighth,  after  which 
they  decrease  to  the  last,  which  is  usually  the  shortest.  The  length  of  the  last  rib 
is,  however,  very  uncertain,  varying  from  one  centimetre  to  perhaps  fifteen  centime- 
tres or  more.  It  often  is  longer  than  the  first.  The  curve  is  comparatively 
regular  in  the  first  rib,  after  which  the  difference  between  the  two  ends  becomes 
more  marked,  the  curve  being  very  pronounced  behind  and  less  so  in  front.  '  The 
curve  is  much  less  throughout  in  the  lower  ribs  ;  in  fact,  it  decreases  continually. 
The  first  rib  is  the  broadest  of  all  at  the  anterior  end.  There  is  a  general,  but  not 
regular,  increase  from  the  second  to  the  seventh  rib,  and  a  subsequent  decrease. 
The  fourth  rib  is  relatively  broad,  the  fifth  narrow.1 

Exceptional  Ribs. — Certain  of  the  ribs — the  first,  second,  tenth,  eleventh, 
and  twelfth — present  peculiarities  which  claim  mention. 

Fig.  176. 


Articular 
facet  on  tu- 
bercle 


Angle 


-  Second  digitation  of  serratus  magma* 
-  Third  digitation  of  serratus  magnus 
First  and  second  ribs  of  right  side,  upper  surface. 

The  first  rib  is  flat,  not  twisted,  with  an  outer  and  an  inner  border.  The 
head  is  small  and  has  but  one  facet,  resting  as  it  does  on  the  first  thoracic  vertebra. 
The  neck  is  small  and  flat  like  the  body.  The  tubercle  is  very  prominent.  The 
scalene  tubercle  is  a  very  small  but,  from  its  relations,  important  elevation  on  the 
inner  margin  of  the  upper  surface,  at  about  the  middle,  for  the  insertion  of  the 
scalenus  anticus.  It  separates  two  grooves  crossing  the  bone  for  the  subclavian 
artery  and  vein.  The  posterior  one  for  the  artery  is  the  more  marked.  There  is  a 
rough  impression  behind  the  latter  near  the  outer  border  for  the  scalenus  medius. 
There  is  no  subcostal  groove. 

The  second  rib  is  intermediate  in  shape  between  the  first  and  the  rest.  The. 
roughness  for  the  serratus  magnus  is  very  marked  about  the  middle  of  the  shaft. 

1  Anderson  :  Journal  of  Anatomy  and  Physiology,  vol.  xviii.,  1884. 


EXCEPTIONAL    RIBS. 


153 


The  tenth  rib  has  usually  only  a  single  articular  facet  on  the  head  ;  it  may  or 
may  not  have  a  facet  on  the  tubercle. 

The  eleventh  rib  has  a  single  articular  facet  on  the  head  ;  the  tubercle  is  rudi- 
mentary and  non-articular  ;  the  angle  and  the  subcostal  groove  are  slightly  marked. 

The  twelfth  rib  has  also  a  single  articular  facet  on  the  head  ;  the  tubercle  is  at 
most  a  faint  roughness  ;  the  angle  and  the  subcostal  groove  are  wanting. 

Development. — The  first  centre  for  the  shaft  appears  in  the  ninth  week  of 
fcetal  life,  and  spreads  so  rapidly  that  by  the  end  of  the  fourth  month  the  perma- 
nent proportion  of  bone  has  been  formed.  At  an  uncertain  period,  probably  before 
puberty,  a  centre  appears  for  the  head  and  another,  except  in  the  last  two  or  three 
ribs,  for  the  tubercle  ;  these  unite  presumably  by  the  twentieth  year. 

Variations. — The  num- 
ber of  ribs  is  often  increased  or 
diminished  by  one,  generally  by 
a  change  at  the  end  of  a  re- 
gion, as  explained  in  varia- 
tions of  the  spine  (page  131). 
Cervical  ribs  occur  by  the  cos- 
tal element  of  the  seventh  cer- 
vical becoming  free.  In  the 
lowest  and  most  common  grade 
it  consists  of  a  head,  a  neck,  a 
tubercle,  and  a  rudimentary 
shaft  one  or  two  centimetres 
long,  ending  free.  In  the  next 
grade  it  is  longer,  and  its  end, 
perhaps  continued  in  cartilage, 
rests  on  the  first  rib.  Some- 
times it  fuses  with  the  first  rib, 
which  then  becomes  bicipital, 
as  is  normal  in  certain  whales. 
In  the  third  grade,  which  is 
very  uncommon,  it  resembles  a 
small  first  rib,  reaching  the  ster- 
num. A  cervical  rib  has  been 
seen  more  than  once  with  the 
transverse    foramen    persisting. 

The  explanation  of  this  condition  is  given  under  ossification  of  the  vertebrae.  When 
a  cervical  rib  reaches  the  sternum,  the  next  rib  is  usually  attached  to  the  side  of  the 
manubrium  by  a  broad  cartilage,  fusing  with  that  of  the  cervical  rib.  The  rib  of  the 
eighth  vertebra  has  been  seen  to  end  like  an  ordinary  second  rib.  It  is  also  very 
rare  to  have  only  twelve  pairs  of  ribs,  of  which  the  first  is  cervical.  There  may  be 
thirteen  ribs  by  the  addition  of  the  costal  element  of  the  first  lumbar.  This  may 
be  so  small  as  to  present  no  rib-like  feature,  or  it  may  resemble  an  ordinary  twelfth 
rib.  In  cases  of  an  extra  rib  from  this  source  the  twelfth  rib  is  usually  uncom- 
monly long.  Very  rarely  the  first  true  thoracic  rib  is  imperfect,  being  continued 
in  ligament  to  the  sternum,  joining  the  shaft  of  the  second  rib,  or  even  ending  free. 
A  bicipital  rib  may  occur  also  by  the  fusion  of  the  first  thoracic  with  the  second  be- 
yond the  tubercles.  The  resulting  plate  later  subdivides,  to  be  continued  by  two 
normal  costal  cartilages.  Ribs  sometimes  divide,  generally  near  the  front.  The 
parts  formed  by  such  cleavage  are  continued  by  costal  cartilages  which  usually  re- 
unite, so  that  a  foramen  is  formed  which  is  bounded  laterally  or  externally  by  bone, 
mesially  by  cartilage.  This  occurs  most  commonly  in  the  third  and  fourth  ribs,  espe- 
cially in  the  latter. 

THE   COSTAL   CARTILAGES. 

The  costal  cartilages '  continue  the  ribs,  the  first  seven  going  directly  to  the  ster- 
num, the  next  three  each  to  the  one  above  it,  and  the  last  two  ending  free.  They 
grow  longer  from  the  first  to  the  seventh,  sometimes  to  the  eighth.      The  last  two. 

1  Cartilagines  costalcs. 


Vertebral  ends  of  tenth,  ele 


154 


HUMAN    ANATOMY. 


cartilages  are  short  and  pointed.  There  is  occasionally  a  projection  downward 
from  the  fifth,  at  its  most  dependent  point,  which  articulates  with  the  sixth.  Usually 
there  is  a  similar  projection  on  the  latter  for  the  seventh.      The  eighth,  ninth,  and 


Post 
Surfaces  of  stern 


Anterior 
fied  ensiform  cartilage. 


tenth  cartilages  have  usually  their  chief  connection  with  the  one  above,  not  through 
their  ends,  but  through  similar  facets.  As  to  direction  :  the  first  cartilage  descends, 
.the  second  is  horizontal,  the  third  rises  very  slightly,  and  the  fourth  is  the  first  to  fall 
and  then  rise.      This  chanee  of  direction  occurs  in  each  to  the  ninth  or  tenth  carti- 


THE    STERNUM. 


155 


lage,  the  falling  portion  becoming  always  relatively  shorter  and  the  rising  longer. 
The  last  two  cartilages  continue  the  line  of  their  ribs,  having  no  rising  portion.  It 
is  not  uncommon  to  find  eight  cartilages  joining  the  sternum.  Tredgold  found  this 
condition   in  ten  per  cent,  of  white   men.      It  is  very 

much    more  frequent   in   negroes    and   in   other  dark  Fig.  179. 

races.1    It  is  said  to  occur  more  often  on  the  right  side. 


THE    STERNUM. 


i 


The  adult  sternum  consists  of  three  flat  median       cartiia; 
plates,  the  two  former  being  bone,  the  last  largely  car- 
tilage,— namely,   the  presternum   or  manubrium,   the 
mesosternum,  gladiolus,  or  body,  and  the  metastcrnum 
or  ensiform  cartilage. 

The  manubrium2  is  broad  in  mammals  having 
clavicles,  to  which  it  gives  support  at  the  upper  angles.  manubrium 

In  man  it  is  irregularly  quadrilateral,  with  the  angles 
cut  off,  broad  above,  narrower  below,  the  greatest 
breadth  equalling  or  exceeding  the  length.  It  is  con- 
cave behind,  but  in  front  it  is  convex  from  side  to  side 
and  slightly  concave  from  above  down.  The  upper 
border  is  concave  in  the  middle,  forming  the  bottom 
of  the  interclavicular  notch.7.  On  each  side  of  this,  in 
the  place  of  a  corner,  is  a  concavity  for  the  sternal  end 
of  the  clavicle.  This  depression  *  is  more  on  the  top 
than  on  the  side  of  the  sternum,  and  usually  encroaches 
more  on  the  back  of  the  bone.  It  is  concave  from 
within  outward  and  may,  or  may  not,  be  slightly  con- 
cave from  before  backward.  The  facet  is  coated  with 
articular  cartilage.  Just  below  the  joint,  the  side  of 
the  manubrium  projects  outward  to  meet  the  cartilage 
of  the  first  rib.  This  is  the  widest  part  of  the  first 
piece,  the  border  then  slanting  inward  to  the  lower 
angle,  which  also  is  cut  off  by  a  notch  for  the  second 
costal  cartilage,  which  is  received  between  it  and  the 
body.  The  lower  border,  separated  from  the  meso- 
sternum by  fibro-cartilage,  projects  a  little  forward  into 
a  transverse  ridge,  always  to  be  felt  in  life,  which  in- 
dicates the  level  of  the  second  costal  cartilage. 

The  oblong  body,  or  gladiolus,3  ossifying  origi- 
nally in  four  pieces,  one  above  another,  varies  con- 
siderably in  shape.  It  is  generally  slightly  concave 
behind  and  nearly  plane  in  front,  but  it  may  be  convex 
or  even  concave.  The  greatest  breadth  is  below  the 
middle,  whence  the  borders  slant  inward  to  the  lower 
end,  the  narrowest  part,  where  it  joins  the  ensiform 
cartilage.  The  sides  of  the  body  present  alternately 
smooth  concavities  opposite  the  spaces  between  the 
costal  cartilages  and  articular  facets  for  the  latter.  To 
understand  the  position  of  these  articular  facets,  we 
must  recall  the  composition  of  the  mesosternum  as 
consisting  of  four  pieces.  The  second  cartilage  reaches 
the  junction  of  the  manubrium  and  the  body  ;  the  third,  Right  side  of  sternum. 

that  of  the  first  and  second  pieces  of  the  body  ;  the 

fourth,  that  of  the  second  and  third  pieces  ;  the  fifth,  that  of  the  third  and  fourth 
pieces.      The  two  remaining  sternal  ribs  send  their  cartilages  to  this  fourth  piece  of 
the  body  ;  the  sixth  to  the  side,  and   the  seventh  to  the  lower  angle,  or  even  the 
1  Journal  of  Anatomy  and  Physiology,  vol.  xxxi,  1S97.     Lamb  :  Nature,  1S88. 

5  Manubrium  sterni.     s  Incisura  jueularis.     4  Incisura  clavicularis.     5  Corpus  stcrni. 


156 


HUMAN    ANATOMY. 


lower  edge.  The  first  and  second  pieces  of  the  body  are  about  equal  in  length  ;  the 
third  is  shorter,  and  the  fourth  still  more  so  ;  hence  the  fifth,  sixth,  and  seventh 
cartilages  end  very  close  together,  especially  the  two  last. 

The  ensiform  cartilage,1  or  xiphoid  process,  more  or  less  bony  in  middle 
life,  is  a  flat  plate  with  a  rounded  end,  not  rarely  bifid.  It  is  fastened  to  the  lower 
end  of  the  body  in  such  a  way  that  their  posterior  surfaces  are  continuous,  but  that 
the  ensiform,  being  thinner,  is  overlapped  by  the  ends  of  the  seventh  cartilages  ;  its 
front  is  therefore  at  a  deeper  level  than  that  of  the  body.  The  size  and  shape  of 
the  ensiform  cartilage  are  very  uncertain  ;  usually  the  tip  projects  somewhat  forward. 

Differences  due  to  Sex. — The  body  of  the  male  sternum  is  both  absolutely 
and  relatively  longer  than  that  of  the  female.  This  is  in  accordance  with  the  greater 
development  of  the  male  thorax.  The  following  table  gives  the  actual  size,  accord- 
ing to  the  writer2  and  to  Strauch.3 


DWIGHT. 

Men.  Women. 

Centimetres.         Centimetres. 

Manubrium 5.37  4.94 

Body 1 1.04  9.19 

Total 16.41  14.13 


Strauch. 
Men.  Women. 

Centimetres.  Centimetres. 

5.049  5.056 


II. 014 
16.063 


9-Q59 
14-115 


Fig.  180. 


Hyrtl  gave  a  rule  for  determining  the  sex,  that  the  manubrium  of  the  female 
exceeds  half  the  length  of  the  body,  while  the  latter  in  the  male  is  at  least  twice  as 
long  as  the  manubrium.  A  study  of  342  sterna,  of 
which  222  were  male  and  120  female,  confirmed  Hyrtl's 
law  for  the  mean  ;  since,  however,  approximately  forty 
per  cent,  of  the  cases  were  exceptions,  it  is  clearly 
worthless  to  determine  the  sex  in  any  given  case. 
Probably  the  law  would  be  correct  if  we  had  to  do 
only  with  well-formed  sterna,  but  the  body  varies 
greatly.  It  is  easy  to  recognize  a  typical  male  or 
female  sternum.  The  former  has  a  long,  regular  body, 
the  lower  pieces  of  which  are  well  developed,  sepa- 
rating the  lower  cartilages  of  the  true  ribs.  The  latter 
has  a  shorter  and  relatively  broader  body,  the  lower 
parts  of  which  are  poorly  developed,  so  that  the  carti- 
lages are  near  together,  and  the  seventh  ones  of  the  two 
sides  almost,  or  quite,  meet  below  the  body  in  front  of 
the  base  of  the  ensiform. 

Variations. — The  very  rare  cases  of  fissure  of 
the  sternum,  and  the  not  uncommon  ones  of  perfora- 
tion in  the  median  line,  represent  different  degrees  of 
arrest  of  development.  The  lower  half  of  the  sternum 
is  sometimes  imperfectly  developed.  We  have  de- 
scribed a  case  in  a  negress  in  which  there  was  but  little 
and  irregular  ossification  below  the  fourth  costal  carti- 
lage. A  very  rare  anomaly  is  that  of  the  manubrium 
being  prolonged  to  the  insertion  of  the  third  costal 
cartilages,  as  occurs  usually  in  the  gibbons  and  occa- 
sionally in  other  anthropoid  apes. 

The  suprasternal  bones,  very  rarely  seen  in  the 
adult,  are  a  pair  of  rounded  bones  compressed  later- 
ally, about  the  size  of  peas,  placed  on  the  top  of  the 
manubrium  at  the  posterior  border  just  internal  to  the  sterno-clavicular  joint.  They 
are  presumably  the  tops  of  the  lateral  cartilaginous  strips  forming  the  sternum,  in 
which  they  are  normally  lost.  They  are  regarded  as  representing  the  episternuni 
of  lower  vertebrates. 


Sternum,  showing  foramen  due  tc 
perfect  union  of  lateral  parts 


'Journal  of  Anatomy  and  Physiology,  vol.  xxiv.,  1890. 

1  Processus  xiphoideus. 


1  Inaug.  Disser.,  Dorpat,  18S1. 


DEVELOPMENT    OF    THE   STERNUM. 


157 


Fig.  181. 
B 


Development  and  Subsequent  Changes. — The  cartilaginous  bars  repre- 
senting the  ribs  in  the  early  embryo  end  in  front  in  a  strip  connecting  them  from  the 
first  to  the  ninth,  which  approaches  its  fellow  above  and  recedes  from  it  below. 
The  union  of  these  two  strips,  which  begins  above,  forms  the  future  sternum  as  far 
as  the  ensiform  cartilage.  Thus  at  this  early  stage  there  are  nine  sternal  ribs.  While 
the  mesosternum  is  forming  by  the  union  of  the  lower  part,  a  portion  of  the  ninth 
strip  separates  itself  from  the  rest  to  fuse  with  its  fellow  for  the  ensiform  cartilage, 
and  the  remainder  of  the  ninth  joins  the  eighth,  which,  as  a  rule,  itself  later  recedes 
from  the  sternum. 

The  original  cartilaginous  strips  having  fused,  points  of  ossification  first  appear 
in  the  manubrium  about  the  sixth  month  of  fcetal  life.  There  is  one  chief  one  and 
a  varying  number  of  small  ones  variously  disposed.  Sometimes  it  ossifies  in  a  larger 
upper  and  a  smaller  lower  piece.  In  the  latter  months,  before  birth,  several  points 
appear  in  the  mesosternum.  The  first  piece  generally  has  a  single  centre,  those  below 
two  in  pairs.  At  birth  one  usually  finds  ossification  begun  in  the  first  three  pieces 
of  the  body.  The  centre  for  the  last  piece  of  the  body  begins  to  ossify  at  a  very 
variable  time.  We  have  seen  bone  in  it  at  thirteen  days  and  have  found  none  at 
seven  years.  Perhaps  three  years  is  not  far  from  the  average.  The  centre,  or  cen- 
tres, for  this  last  piece  of  the  body  are  placed  in  its  upper  part.  Its  cartilage  is 
directly  continuous  with  that  of  the 
ensiform,  the  line  of  demarcation 
being  determined  by  the  difference 
in  thickness,  the  ensiform  being 
thinner  and  continuing  the  plane  of 
the  posterior  surface.  Thus,  the 
lower  part  of  the  last  piece  may 
continue  cartilaginous  for  a  con- 
siderable time.  A  centre  in  the 
ensiform  is  sometimes  seen  at  three, 
but  may  not  come  for  several  years 
later.  The  four  pieces  of  the  meso- 
sternum join  one  another  from  be- 
low upward,  the  union  being  com- 
pleted on  the  posterior  surface  first. 
The  process  is  extremely  variable. 
The  only  points  regarding  which  we 
are  certain  are  that  it  is  more  rapid 
than  is  usually  stated  and  that  the 
body  is  almost  always  in  one  piece 
at  twenty.  The  fourth  piece  of'  the  body  joins  the  third  at  about  eight,  the  third 
joins  the  second  at  about  fifteen,  and  the  second  unites  with  the  first  usually  at 
eighteen  or  nineteen.  We  once  saw  all  four  pieces  distinct  at  eighteen,  but  in 
one  or  two  instances  only  have  we  found  the  body  incomplete  after  twenty.  The 
amount  of  bone  in  the  ensiform  at  twenty  is  still  small.  The  adult  condition,  except 
that  the  ensiform  gradually  becomes  wholly  bone,  may  persist  to  extreme  old  age. 
The  ensiform  often  joins  the  body  after  middle  age,  rarely  before  thirty.  The 
union  of  the  manubrium  and  the  body  is  rare,  and  appears  to  be  the  result  of  a  con- 
stitutional tendency  rather  than  of  age,  as  in  our  observations  we  have  repeatedly 
found  it  under  fifty,  and  have  seen  all  three  pieces  united  at  twenty-five.  The 
different  pieces  are  more  apt  to  fuse  in  man  than  in  woman. 


^; 

\£ 

D 

C 

rs 

c 

^ 

c 

2 

c 

£ 

Da 


'tr- 


ie 


z> 


Ossification  of  the  sternu 
for  manubrium.     B,  at  birth 
ments  of  body.    C  at  about  ten  years 
inents  of  body;  e,  ensiform  cartilage. 


.  A,  at  sixth  Foetal  1 


onth  ;  c, centre 
b,  c,  dt  for  seg- 
1m;  b,  c,  d,seg- 


ARTICULATIONS    OF    THE    THORAX. 

The  joints  uniting  the  bones  taking  part  in  the  formation  of  the  bony  thorax 
constitute  two  general  groups,  the  Anterior  and  the  Posterior  Thoracic  Articula- 
tions. The  former  include  the  joints  between  the  pieces  of  the  sternum,  those  be- 
tween the  sternum  and  the  costal  cartilages,  and  those  between  the  costal  cartilages  ; 
the  latter,  or  the  costo-vertebral  articulations,  include  those  between  the  vertebra? 
and  the  ribs. 


158 


HUMAN    ANATOMY. 


THE    ANTERIOR    THORACIC  ARTICULATIONS. 

These  include  three  sets  : 

I.  The  Intersternal  Joints,  or  those  uniting  the  segments  of  the  sternum 


Sterno-clavicular  joint 


Anterior  intersternal 

ligament 
Chondro-sternal  ligament 


W  ,?v—  Costo-xiphoid  ligament 


— Interchondral  ligament 


The  sternum  and  costal  cartilages  from  before. 


2.  The  Costo-Sternal  Joints,  or   those  uniting  the  ribs  by  means  of  their 
cartilaginous  extensions  with  the  sternum  ; 

3.  The  Interchondral  Joints,  or  those  uniting  certain  of  the  costal  cartilages 
with  one  another. 


INTERSTITIAL    ARTICULATIONS. 


159 


THE    INTERSTERNAL   JOINTS. 

While  the  manubrium  and  the  four  pieces  of  the  body,  or  sternebrae,  are  still 
separate  ossifications  in  a  common  strip  of  cartilage,  the  structure  is  greatly  strength- 

Fig.  183. 


Chondro-sternal  joint 


-   ENSIFORM  CARTILAGE 


Interchondral  ligament 


Longitudinal  section  through  sternum  and  costal  cartilages. 


ened  by  the  thick  periosteum,  reinforced  by  the  radiating  bands  from  the  costal 
joints  and  longitudinal  fibres  before  and  behind.  When  the  body  has  become  one 
piece  it  is  separated  from  the  manubrium  by  the  persisting  cartilaginous  strip.      The 


160  HUMAN    ANATOMY. 

strengthening  bands  require  no  further  description.  A  cavity  is  often  found  in  the 
cartilage,  making  a  typical  half-joint.  At  what  time  it  appears  is  unknown.  Some- 
times it  is  so  developed  that  the  joint  is  practically  a  true  one,  with  articular  carti- 
lage ;  this  exceptional  arrangement  is  more  common  in  women  than  in  men,  being 
especially  adapted  to  the  female  type  of  respiration.  The  cartilage  persisting 
between  body  and  ensiform  is  strengthened  in  a  similar  manner.  A  cavity  rarely 
occurs  in  the  cartilage,  which,  on  the  contrary,  often  undergoes  ossification. 

THE   COSTO-STERNAL   JOINTS. 

The  first  costal  cartilage  joins  directly,  without  interruption,  the  lateral  expan- 
sion of  the  sternum  ;  the  following  costal  cartilages  articulate  at  the  points  already 
mentioned  by  synovial  joints.  Those  that  come  between  different  sternebrae — that 
is,  from  the  second  to  the  fifth — often  have  the  joint  subdivided  by  a  band  into-an 
upper  and  a  lower  half.  This  is  usual  in  the  joint  of  the  second  cartilage  ;  progres- 
sively rare  as  we  descend.  The  sixth  and  seventh  cartilages  frequently  have  no 
true  joint.1  Each  of  these  joints  is  enclosed  by  a  capsule,  the  front  and  back  fibres 
of  which  radiate  over  the  sternum. 

THE   INTERCHONDRAL  JOINTS. 

The  seventh,  eighth,  ninth,  and  tenth  costal  cartilages  have  each  an  articulation 
by  a  true  joint  on  the  projections  above  described  with  the  one  above  it.  There  is 
a  connection  between  the  fifth  and  sixth  cartilages  ;  usually  on  the  right,  very 
frequently  on  the  left.2  This  is,  as  a  rule,  also  a  true  joint,  but  the  cartilages  may 
be  merely  bound  together  by  bands  of  fibres.  The  joint  on  the  right  side  is  almost 
always  a  true  one.  The  ends  of  the  eighth,  ninth,  and  tenth  cartilages  are  joined 
by  fibrous  tissue  to  the  cartilage  above. 

The  costo-xiphoid  ligament  is  a  band  extending  from  either  side  of  the  base 
of  the  ensiform  to  the  lower  border  and,  perhaps,  the  front  of  the  seventh  cartilage 
near  its  end. 

THE   COSTO-VERTEBRAL   ARTICULATIONS. 

The  joints  between  the  ribs  and  the  spine  are  in  two  series  :  an  inner,  or 
Costo- Central,  between  the  heads  of  the  ribs  and  the  bodies  of  the  vertebrae;  an 
outer,  or  Costo- Transverse,  between  the  tubercles  and  the  transverse  processes. 

The  Costo-Central  Joints. — The  head  of  the  rib  is  received  in  a  hollow 
articular  fossa  formed  by  a  part  of  two  bodies  and  the  disk  between  them.  Although 
as  a  whole  concave,  it  may  in  a  typical  case  be  further  analyzed.  The  lower  half  of 
the  socket  is  convex  from  above  downward,  fitting  into  the  hollow  at  the  lower  part 
of  the  joint  of  the  rib  ;  the  upper  part  is  about  plane,  looking  downward  and  out- 
ward, with  the  upper  border  considerably  overhanging  the  joint.  These  two  facets 
have  each  a  synovial  capsule  and  are  separated  by  an  inlerarticular  ligament?  a 
band  running  from  the  ridge  on  the  head  of  the  rib  to  the  posterior  part  of  the  inter- 
vertebral disk.  In  the  foetus  before  term  it  extends  across  the  back  of  the  disk  to 
the  head  of  the  opposite  rib. 

The  front  of  the  capsules  is  strengthened  by  the  anterior  costo-vertebral  ligament,* 
which  is  a  series  of  radiating  fibres  from  the  head  to  both  vertebrae  and  the  interven- 
ing disk,  not  clearly  separable  into  three  bands.  These  stellate  ligaments  (Fig.  184) 
are  least  developed  in  the  upper  part  of  the  thorax.  The  strongest  collection  of 
fibres  is  to  the  lower  vertebra.  The  joint  of  the  first  and  last  two  ribs  is  not  sub- 
divided ;  that  of  the  tenth  is  uncertain.  Strong  fibres  pass  from  the  head  of  the 
first  rib  to  the  seventh  cervical  vertebra.  Few  or  no  fibres  from  the  last  rib  reach 
the  body  of  the  eleventh  thoracic.  The  lower  fibres  are  made  tense  when  the  rib  is 
raised  and  the  upper  when  it  is  depressed. 

The    Costo-Transverse   Joints. — The    articular  surfaces    of   the   tubercles, 

1  Musgrove :   Journal   of  Anatomy  and   Physiology,   vol.    xxvii.,    1893.     2  Fawcett :   Anat. 
Anzeiger,  Bd.  xv.     Bardeleben  :  ibid. 

:!Ug.  capituli  costac  intcrarticulare.     4  Lig.  capituli  costae  radiatum. 


COSTO-TRANSVERSE   ARTICULATIONS. 


161 


convex  vertically,  are  received  into  the  hollows  on  the  facets  of  the  transverse  pro- 
cesses. The  cavities  are  deepest  in  the  upper  part  of  the  thoracic  region,  but  the 
facet  on  the  hrst  transverse  process  is  nearly  plane.      In  the  lower  part  of  the  region 


Superior  costo-t 
verse  ligament 


Posterior  costo-tra 
verse  ligament 


Upper  part  of  stellate 
ligament 


Ligaments  uniting  ribs  with  spine,  from  before. 


these  cavities  are  smaller  and  less  concave,  allowing  freer  motion.  There  is  none 
for  the  twelfth  rib,  and  but  a  poor  one,  if  any,  for  the  eleventh.  There  are  three 
costo-transverse  ligaments :   the  posterior,   the  middle,  and  the  superior.     The  pos- 

Fig.  1S5. 


Middle  costo- 
transverse liga- 
ment 


Middle  costo-trans- 
ligament 


Costo-Vertebral 

joint 


Intervertebral  disk 


Transverse  section  through  intervertebral  disk  and  ribs. 


ierior1  are  strong  bands  running  outward  from  the  tips  of  the  transverse  processes 
to  the  rough  part  of  the  tubercle  beyond  the  joint.  The  middle 2  are  strong  short 
fibres  connecting  the  front  of  the  transverse  process  and  the  back  of  the  neck  of  the 

1  Llg.  costotransvci  saiium  postcrius.     -  Lig.  colli  costae. 


l62 


HUMAN    ANATOMY. 


rib  between  the  head  and  the  tubercle.  Those  for  the  last  two  ribs  are  small,  that 
for  the  twelfth  springing  from  the  accessory  tubercle.  The  superior  costo-U'ansverse 
ligaments '  are  thin  bands,  passing  downward  and  a  little  inward  from  the  under  side 
of  the  transverse  processes  to  the  crest  on  the  upper  edge  of  the  neck  of  the  rib 
below.  Those  of  the  first  and  last  two  ribs  are  of  little  account.  This  band  becomes 
tense  when  the  rib  is  depressed  and  carried  inward  ;  the  inner  fibres  are  tense  when 
the  rib  is  raised.  The  outer  fibres  fuse  with  the  front  surface  of  the  posterior  inter- 
costal aponeurosis.  Weaker  and  inconstant  bands  of  the  same  general  direction  are 
described  behind  these.  The  fibres  of  the  aponeurosis  are  particularly  strong 
between  the  last  two  ribs.  A  special  band  of  the  same  series  runs  from  the 
transverse  process  of  the  first  lumbar  upward  and  outward  to  the  last  rib.  The 
movements  of  the  ribs  are  described  with  those  of  the  thorax  (page  165). 


THE  THORAX   AS   A  WHOLE. 

The  thorax  is  a  cage  with  movable  walls  capable  of  expansion.  In  shape  it  is 
an  irregular  truncated  cone,  much  deeper  behind  than  in  front  and  broader  from  side 
to  side   than  from   before   backward.     The   thoracic  vertebrae  form   the  posterior 


Fig.  18 


VII  thoracic  rib 


Middle  costotransverse 
ligament 


Superior  costo-t 
ligament 


Ligamentum  subflav 


Intertransverse  ligament 


siivi 

Ligaments  uniting  ribs  with  spine,  from  behind. 


boundary  ;  the  sternum,  including  the  very  beginning  of  the  ensiform  cartilage,  the 
anterior.  The  inlet,  or  upper  boundary,  is  an  imaginary  plane  slanting  downward 
and  forward  from  the  top  of  the  first  thoracic  vertebra  to  that  of  the  sternum,  and 
bounded  laterally  by  the  inner  borders  of  the  first  rib.  The  inferior  boundary,  made 
by  the  diaphragm,  does  not  exist  in  the  skeleton.  Suffice  it  to  say  that  the  dome- 
like disposition  of  the  diaphragm  makes  the  abdomen  much  larger  and  the  thorax 
much  smaller  than  one  would  expect  from  the  skeleton  alone.  The  thorax  of  the 
living  presents  a  fairly  well-defined  posterior  surface,  while  the  lateral  ones  pass  in- 
sensibly into  the  anterior  ;  the  upper  part  is  hidden  by  the  shoulder-girdle  and  arm. 
The  line  of  the  angles  of  the  ribs  marks  the  limits  of  the  back  and  sides.  The  inside 
of  the  thorax  is  heart-shaped  in  horizontal  section.  The  spine  projects  into  it  behind, 
and  the  ribs  recede  from  this  on  either  side.  As  the  bodies  of  the  vertebras  are 
larger  in  the  lower  part,  the  projection  into  the  thorax  is  greater  ;  but  as  the  area  of 
the  section  is  much  larger,  the  effect  is  less  striking.      The  distance  from  front  to 

1  Lig.  costotransversarium  anterius: 


THE   THORAX    AS    A    WHOLE. 


i6- 


back  in  the  median  line  is  least  at  the  top.  It  increases  at  once,  owing  to  the  back- 
ward bend  of  the  spine  and  the  forward  slant  of  the  sternum,  reaching  the  maxi- 
mum at  about  the  middle  of  the  thorax.  It  decreases  slightly  below,  owing  to' the 
forward  sweep  of  the  spine,  but  the  position  of  the  lower  end  of  the  sternum  is  so 
uncertain  that  this  is  very  variable.  The.  breadth  of  the  thorax  increases  very 
rapidly,  reaching  nearly  the  maximum  where  the  third  rib  crosses  the  axillary  line. 
Below  this  it  increases  a  little,  being  greatest  where  the  fifth  rib  crosses  the  same 


Fig.  187. 


The  bony  thj 


line.  It  then  continues  very  nearly  the  same  with  some  slight  diminution  below. 
The  greatest  length  of  the  thoracic  framework  is  in  the  axillary  line,  the  lowest 
point  being  the  cartilage  of  the  tenth  or  eleventh  rib,  which  in  the  male  may  nearly 
reach  the  crest  of  the  ilium.  The  downward  slant  of  the  ribs  and  the  rise  of  most  of 
the  cartilages  make  the  study  of  horizontal  sections  at  first  very  confusing.  The 
relations  at  certain  levels  must  be  somewhat  conventional,  for  the  variations  are  very 
great,  depending  on  figure,  age,  health,  position,  and  the  stage  of  the  respiratory 
movements.      Two  levels  must  be  taken  as  standards,  subject  to  these  corrections. 


164 


HUMAN   ANATOMY. 


The  top  of  the  sternum  is  on  a  level  with  the  disk  between  the  second  and  third 
thoracic  vertebrae  ;  the  junction  of  manubrium  and  body  of  sternum  is  on  a  level 

Fig.  16 


Transverse  section  through  thorax  at  level  of 
third  thoracic  vertebra.     (Braune.) 


3Q 


S 


fe\ 


a 


Fig.  190. 

CO 


'P 

•0 


^VK 


0 

0' 


with  the  top  of  the  fifth  thoracic  vertebra.      Less  accurate,  but  still  useful,  is  a  third 

level  :   the  lower  end  of   the  body  of  the  sternum  is  opposite  the  ninth  thoracic 

vertebra.  Accompanying  diagrams, 
taken  from  Braune,  show  the  varia- 
tions of  size,  form,  and  relations  at 
different  levels  (Figs.   188  to  191). 

The  breadth  of  the  intercostal 
spaces  is  very  different  in  diverse 
parts.  Between  the  tubercles  and 
angles  it  is  pretty  nearly  the  same 
throughout,  butthe  last  two  spaces  are 
a  little  broader.  The  first  two  spaces 
are  much  the  broader  at  the  sides 
and  in  front.  They  are  broad  near 
the  sternum  as  far  down  as  the  fifth 
cartilage.  At  the  sides  the  ribs  are 
very  close  together,  from  the  fourth 
to  the  ninth  often  almost  in  contact. 
The  lowest  spaces  are  again  broader. 
The  Thorax  in  Infancy  and  Childhood. — At  birth  the  thorax  is  relatively 

insignificant.      The  sternum  is  small  and  undeveloped  in  the  lower  part.      The  ribs 

are  more  horizontal.      The  top  of 

the  sternum  is  opposite  the  body  Fig.  191. 

of  the  first  thoracic  vertebra.      In  7 

the  course  of  the  first  year  it  lies  JU»®  ^* 

opposite    the    upper   part    of    the 

second,    and    at    five    or    six    has 

reached  its  definite  level  opposite 

the  disk  between  the  second  and 

third  thoracic  vertebrae.     The  lower 

part  of  the  sternum  is  undeveloped, 

and  the  ribs  do  not  fall  so  low  at 

the  sides.      The  want  of  breadth  is 

very  striking,   while  in  the  adult, 

throughout    the    chest    below    the 

level  of  the  second  costal  cartilage, 

the  antero-posterior  diameter  is  to 

the  transverse  as   1    to   2 J^,  or  as 

1   to  3  ;   at  birth  it  is  as   2   to   3. 

We    have    found    it    at    probably 

three  years  as  1  to  2  ;  at  five  or  six  the  thorax  has  nearly  reached  its  permanent 

shape. 

Differences  due  to  Sex. — The  whole  structure  is  lighter  in  women,  but  the 


& 


'0 


^ 


V 
0- 


^ 


c^ 


¥^ 


/ 


Transverse  section  at  level  of  eleventh  vert  el 
(6,  7)  are  sections  of  costal  cartilages. 


a.     Shaded  areas 
(Braune.) 


MOVEMENTS  OF  THE  THORAX.  165 

chief  differences  in  the  proportions  appear  below  the  third  rib.  The  manubrium  is 
as  large,  relatively  to  the  height,  in  one  sex  as  the  other,  although  the  mesosternum 
in  women,  especially  its  lower  part,  is  less  developed  ;  hence  the  ends  of  the  car- 
tilages of  the  lower  sternal  ribs  are  crowded  together,  and  those  of  the  seventh  often 
meet  below  the  sternum,  in  front  of  the  ensiform,  thus  practically  lengthening  the 
body.  The  effect  of  this  is  that  the  relations  of  the  viscera  to  the  walls  are  not  so 
different  in  the  sexes  as  one  would  expect.1  The  floating  ribs  are  small  in  women 
and  do  not  approach  the  pelvis  so  closely  as  in  the  male.  The  antero-posterior 
diameter  of  the  female  chest  is  to  the  transverse  as  1  to  2^  (subject  to  variation), 
thus  more  resembling  the  proportions  of  the  child. 

THE  MOVEMENTS  OF  THE  THORAX. 

The  motions  permitted  by  the  following  joints  are  to  be  considered  separately, 
although  their  interdependence  is  to  be  remembered.  First,  the  joints  of  the  verte- 
bral ends  of  the  ribs,  the  costo-central  and  the  costo-transverse  being  taken  together  ; 
second,  those  between  the  manubrium  and  gladiolus  ;  third,  the  costo-sternal  and 
interchondral  joints  ;  fourth,  as  modifying  these,  flexion  and  extension  of  the  spine  ; 
and  fifth,  the  elasticity  of  the  ribs  and  cartilages. 

Motions  in  the  Costo-Vertebral  Joints. — These  vary  greatly  in  different 
parts  of  the  column.  The  first  rib  moves  as  a  hinge  on  a  fixed  axis  running  out- 
ward, backward,  and  a  little  upward  through  the  joint  on  the  body  of  the  verte- 
bra and  that  on  the  transverse  process.  If  this  axis  were  strictly  transverse,  the 
rising  of  the  front  of  the  rib  would  increase  only  the  antero-posterior  diameter  of  the 
thorax,  as  the  motion  occurs  in  a  plane  at  right  angles  to  the  axis.  Since,  however, 
the  axis  is  oblique,  a  plane  at  right  angles  to  it  extends  forward  and  outward,  and 
motion  in  it  thus  increases  also  the  transverse  diameter  of  the  chest.  The  shape  of 
the  first  rib  is  such  that  this  transverse  increase  amounts  to  little  or  nothing,  but  this 
principle  comes  into  play  with  the  longer  ribs.  The  joint  of  the  second  rib  is  prac- 
tically similar,  except  that  the  outer  end  of  the  axis  at  the  tubercle  is  farther  back, 
so  that  the  plane  of  motion  slants  more  outward  and  the  lateral  expansion  gained 
by  raising  the  second  rib  is  more  marked  independently  of  the  greater  length  of  that 
rib.  With  the  third  rib,  usually,  an  important  modification  begins  ;  the  outer  end 
of  the  axis  is  not  fixed,  for  the  tubercle  slides  on  the  transverse  process.  The 
changes  in  the  facets  on  the  transverse  processes  have  been  described  ;  it  appears 
that,  as  we  descend  the  spine,  they  are  so  placed  and  so  shaped  as  to  allow  this 
movement  more  and  more  freely.  Thus,  in  the  middle  of  the  thoracic  region  the 
outer  end  of  the  axis  of  rotation  is  so  movable  that  the  motion  is  to  be  decomposed 
into  two, — namely,  one  on  the  axis  already  described  through  the  head  and  the 
tubercle,  and  another  on  an  antero-posterior  axis  passing  through  the  head  of  the 
rib  and  the  joint  between  its  costal  cartilage  and  the  sternum.  At  the  eighth  rib  of 
the  dissected  spine  a  new  motion  appears,  which  becomes  much  more  extensive 
in  the  succeeding  ones.  The  ligaments  connecting  the  tubercle  and  neck  to  the 
transverse  process  are  less  tense,  and  it  is  possible  to  move  the  tubercle  a  little 
forward  from  its  socket  ;  in  the  lower  joints  the  rib  can  be  moved  upward,  down- 
ward, forward  and  backward,  and  circumducted.  These  motions  are  particu- 
larly free  at  the  last  two  thoracic  vertebrae.  Motion  backward  is  checked  by 
contact  with  the  transverse  process  ;  forward,  by  the  posterior  and  middle  costo- 
transverse ligaments  ;  upward  motion  of  the  last  two  ribs  by  the  particularly  strong 
bands  of  fascial  origin  described  with  the  ligaments  ;  downward  motion  by  the  in- 
tercostal structures.  An  important  deduction  from  this  is  that  the  last  ribs  can 
be  pulled  downward  and  backward,  so  as  to  fix  the  posterior  costal  origin  of  the 
diaphragm. 

Motions  in  the  Intersternal  Joints. — The  joint  between  the  manubrium 
and  the  body  of  the  sternum  admits  of  motion  on  a  transverse  axis,  which  is  free  in 
the  young,  but  much  restricted  or  abolished  in  the  old.  At  rest,  the  two  parts  form 
a  slight  angle  open  behind.      This  is  effaced  by  the  forward  motion  of  the  body  on 

1  Henke  :  Arch,  fur  Anat.  u.  Phys.,  Anat.  Abtheil,  1883. 


1 66  HUMAN    ANATOMY. 

the  manubrium,  but  in  no  case  is  an  entering  angle  formed  in  front.  A  slight  twisting 
may  also  occur  in  this  joint  in  the  young.  In  these  motions  the  second  costal 
cartilages  follow  the  manubrium.  The  motions  at  the  inconstant  joint  between  the 
sternal  body  and  the  ensiform  process  are  necessarily  indefinite  ;  they  appear  to 
consist  chiefly  of  a  drawing  in  of  the  ensiform. 

Motions  in  the  Costo-Sternal  and  the  Interchondral  Joints. — On  the 
dissected  preparation  the  second  cartilage  can  be  moved  up  and  down,  forward  and 
backward,  and  circumducted  ;  these  motions,  however,  are  very  slight.  In  the 
succeeding  joints  the  same  motions  are  more  and  more  free  as  we  descend.  The 
lower  cartilages  of  the  true  ribs  from  the  fifth  to  the  seventh,  or  to  the  eighth,  inclu- 
sive, should  the  latter  meet  the  sternum,  move  in  a  somewhat  similar  manner,  but 
nearly  as  in  one  piece.  The  motion  on  an  antero-posterior  axis  is  most  free.  The 
joints  between  the  costal  cartilages  are  very  lax,  and  the  surfaces  are  so  placed  that 
the  lower  one  slides  forward  on  the  upper.  The  advantage  of  these  joints  is  that 
the  lower  ribs  and  the  thorax  give  and  receive  support,  while  greater  freedom  of 
motion  is  possible  than  would  be  the  case  were  they  of  one  piece.  Flexion  and 
extension  of  the  spine  modify  these  motions.  The  more  the  spine  is  flexed  the  more 
the  upper  ribs  in  particular  are  depressed,  and  the  more  it  is  extended  the  more  they 
are  raised,  independently  of  any  motion  in  the  joints.  Thus,  when  the  chest  is 
fully  inflated  the  spine  is  always  strongly  extended. 

The  elasticity  of  the  ribs  and  cartilages,  particularly  of  the  latter,  exercises  an 
important,  but  indefinite,  influence  on  all  motions  which  does  not  admit  of  accurate 
analysis.  Even  the  ribs  (except  in  the  old)  are  not  rigid  bars,  and,  especially  in 
forced  inspiration,  there  is  a  pull  upon  them  increasing  their  convexity.  Moreover, 
the  walls  of  the  chest  adapt  themselves  to  the  surface  of  the  lungs  and  to  abnormal 
contents  of  the  thorax,  so  that  certain  conditions  are  marked  by  particular  forms  of 
thorax. 

It  follows  from  the  above  that  the  nature  of  the  respiratory  movements  cannot 
be  deduced  solely  from  the  movements  of  each  set  of  joints  considered  separately. 
The  soft  parts  connecting  them  alone  modify  greatly  the  freedom  of  motion.  Braune 
has  shown  that  the  motion  of  the  ribs  is  much  limited  by  the  sternum,  and  that  if 
the  gladiolus  be  divided  into  its  original  pieces  and  the  cartilage  above  it  cut  through, 
the  thorax  can  be  more  fully  inflated.  Beyond  question  in  forced  inspiration  the 
sternum  is  raised,  thus  increasing  the  antero-posterior  diameter  ;  since  the  ribs  at 
the  same  time  swing  upward  and  outward,  the  transverse  diameter  is  likewise 
increased. 

Surface  Anatomy. — The  sternum  is  always  to  be  felt  in  the  middle  line. 
The  suprasternal  notch  is  filled  up  to  a  large  extent  by  the  interclavicular  ligament. 
The  angle  between  the  manubrium  and  the  body  varies  considerably,  but  it  is  always 
easily  recognized  by  a  cross-ridge.  The  ensiform  cartilage  is  at  a  deeper  level  and 
overhung  on  each  side  by  the  costal  arch.  The  front  of  the  chest  on  each  side  is 
covered  by  the  pectoralis  major,  making  it  hard  to  feel  the  ribs,  except  at  the  borders 
of  the  sternum.  At  the  side  they  are  easily  felt  to  near  the  top  of  the  axilla,  where 
the  third  can  be  recognized. 

The  upper  ribs  are  concealed  by  thick  muscles,  especially  between  the  spine 
and  the  angles.  The  scapula  covers  them  from  the  second  to  the  seventh,  with 
considerable  variations.  The  first  rib  cannot  be  felt  except  where  its  cartilage 
joins  the  sternum.  To  count  the  ribs,  begin  with  the  second  at  the  junction  of  the 
manubrium  and  body  of  the  sternum.  There  is  no  possibility  of  error,  for  the  rare 
cases  of  the  manubrium  reaching  to  the  third  cartilage  may  be  disregarded  ;  feel  the 
third  and  fourth  cartilages  below  it,  and  then  carry  the  finger  downward  and  out- 
ward across  the  chest.  The  twelfth  rib  may  be  too  small  to  be  made  out.  It  is  not 
safe  to  begin  counting  from  below,  for  the  error  of  mistaking  the  eleventh  rib  for 
the  twelfth  has  led  to  opening  the  pleural  cavity  in  an  operation  in  the  lumbar 
region.  The  nipple  is  said  to  be  usually  over  the  fourth  intercostal  space  some  two 
centimetres  external  to  the  cartilage,  but  it  is  very  variable,  especially  in  women, 
and  should  never  be  used  as  a  starting-point  for  counting  the  ribs.  The  width 
of  the  intercostal  spaces  at  different  parts  is  of  obvious  importance,  but  has  been 
described  elsewhere  (page  164). 


PRACTICAL    CONSIDERATIONS  :    THE   THORAX.  167 


PRACTICAL    CONSIDERATIONS. 

The  bony  and  cartilaginous  thorax  is  made  up  of  the  ribs,  sternum,  costal  car- 
tilages, and  thoracic  vertebrae,  and  varies  in  shape  as  a  result  of  several  influences. 
The  slightly  larger  circumference  of  the  right  side  of  the  chest  as  compared  with 
the  left  side  is  probably  due  to  the  greater  use  of  the  right  upper  limb,  and  may 
be  accepted  as  physiological.  Increased  circumference  of  the  left  side,  therefore  (in 
a  right-handed  person),  should  indicate  careful  examination  of  the  spine  (for  lateral 
curvature)  and  of  the  thoracic  viscera. 

Vs\  pigeon-breast  the  sternum  protrudes  together  with  the  costal  cartilages,  while 
the  line  of  the  costo-chondral  junction  becomes  a  deep  groove.  The  sides  of  the 
chest  are  flattened,  and  a  transverse  section  would  be  almost  triangular  in  shape. 
There  are  three  modes  of  production  of  this  very  common  deformity  : 

1.  In  rickety  children  it  is  favored  by  the  softening  of  the  bones  and  cartilages, 
which  are  thus  of  diminished  resiliency,  the  actual  exciting  cause  being  often  some 
form  of  respiratory  obstruction, — e.g. ,  enlarged  pharyngeal  and  faucial  tonsils, 
bronchitis,  nasal  obstructions,  etc.  In  ordinary  breathing,  on  inspiration,  air  enters 
the  chest  freely  to  prevent  the  production  of  a  vacuum,  and  at  the  end  of  the  act 
the  external  atmospheric  pressure  is  balanced  by  the  pressure  within.  If  an  impedi- 
ment to  the  free  ingress  of  air  exists,  the  external  pressure  during  at  least  part  of 
the  act  is  in  excess,  and  in  young  children,  particularly  rickety  children,  this  is 
followed  by  the  bending  inward  along  the  weakest  part  of  the  thorax  (the  costo- 
chondral  line)  and  the  relative  projection  of  the  sternum. 

2.  The  lowest  five  costal  cartilages  form  an  especially  weak  portion  of  the  chest- 
wall.  They  are  the  most  distant  from  the  fulcrum  (the  spine)  on  which  the  ribs 
move  in  respiration,  and  hence  the  expansive  forces  act  with  the  greatest  disadvan- 
tage of  leverage  (Humphry).  At  the  same  time  the  diaphragm,  during  its  contrac- 
tion, tends  to  draw  them  inward.  If,  however,  its  central  arch  cannot  descend 
during  inspiration  on  account  of  an  engorged  liver,  enlarged  abdominal  lymphatics, 
persistent  flatulence,  etc.  (as  in  a  poorly  nourished  child),  it  becomes  the  fixed  point, 
and  the  lateral  walls  are  pulled  in  and  the  sternum  correspondingly  protruded. 

3.  Some  cases  of  "pigeon-breast"  are  seen  at  or  soon  after  birth  in  otherwise 
healthy  children.  It  is  probable  that  these  are  cases  of  arrest  of  development.  The 
so-called  "  keeled  chest  "  (in  which  the  antero-posterior  diameter  is  increased  at  the 
expense  of  the  transverse  diameter)  is  characteristic  of  the  quadrupedal  class  of 
mammals,  and  is  necessitated  by,  and  correlated  with,  the  backward  and  forward 
swing  of  the  anterior  limbs  in  walking.1  In  the  fcetus  the  antero-posterior  diameter 
is  relatively  greater  than  in  the  adult. 

Attention  has  already  been  called  (page  164)  to  the  varying  ratio  between  the 
antero-posterior  and  transverse  diameters  of  the  chest,  the  transverse  diameter  in 
the  adult  exceeding  the  anterior  in  the  proportion  of  2.5  to  1.  If  this  change  stops 
short  of  full  completion,  a  greater  or  less  degree  of  relative  prominence  of  the  ster- 
num results. 

The  "  bellows  chest"2  is  found  among  mammals  almost  exclusively  in  the  bats, 
the  anthropoid  apes,  and  man,  that  have  in  common  simply  the  disuse  of  the  anterior 
limbs  as  a  means  of  support.  In  them  the  chief  movements  of  these  limbs  tend  to 
pull  the  sternum  towards  the  vertebral  column.  The  exaggeration  of  this  type  results 
in  the  so-called  "flat  chest,"  which  is,  however,  within  proper  limits,  the  type  of 
vigor,  as  it  results  from  the  full  contraction  of  normal  muscles. 

Emphysema  produces  a  rotund  configuration  of  the  chest-walls,  affecting  chiefly 
the  upper  portion,  throwing  out  the  ribs,  effacing  the  intercostal  spaces,  and  making 
the  thorax  ' '  barrel-shaped. ' ' 

Old  age,  owing  to  an  increased  bowing  of  the  thoracic  spine  under  the  weight 
of  the  head  and  shoulders  and  to  a  slipping  forward  of  the  shoulder-girdle  with  its 
mass  of  muscles,  often  causes  a  depression  of  the  sternum  and  its  approximation  to 
the  spine, — a  common  form  of  flat  chest. 

1  Woods  Hutchinson  :  Journal  of  the  American  Medical  Association,  vol.  xxix.,  1897. 
»  Ibid. 


168  HUMAN   ANATOMY. 

The  pulmonary  capacity  is  but  roughly  indicated  by  the  circumference  of  the 
chest,  as  the  vertical  diameter  is  also  obviously  an  important  determining  factor. 
Chest  measurements,  to  be  of  value,  should  therefore  be  supplemented  by  investiga- 
tion into  the  amount  of  air  which  can  be  inhaled  and  exhaled.  The  resulting 
information  is  often  of  great  value  as  a  basis  for  prognosis  and  for  advice  as  to  exer- 
cise and  hygiene,  especially  in  persons  with  a  predisposition  to  pulmonary  disease. 

In  the  infant  the  thorax  is  relatively  smaller  than  in  the  adult.  In  the  female 
the  upper  portion  of  the  thorax  is  less  compressed  from  before  backward  and  is 
more  capacious  than  in  the  male.  The  upper  aperture  is  larger  and  the  range  of 
movement  between  the  upper  ribs  and  the  sternum  and  vertebrae  is  greater.  These 
circumstances  account  both  for  the  fulness  of  the  upper  portion  of  the  chest  in  the 
female  and  for  the  character  of  the  respiratory  movement,  which  is  known  as 
thoracic ;  while  that  of  the  male,  in  which  the  lower  ribs  and  abdominal  walls  move 
more  freely,  is  known  as  the  abdominal  type  of  respiration. 

The  sternum  may  be  entirely  wanting,  or  may  be  divided  into  two  portions  by 
a  fissure  down  the  middle,  the  result  of  developmental  failure,  which,  when  it  exposes 
the  thoracic  cavity  and  the  heart,  is  known  as  ectopia  cordis. 

Its  subcutaneous  position  makes  it  the  subject  of  slight  but  frequent  traumatisms, 
which  often  serve  to  localize  the  bone  lesions  of  syphilis,  tuberculosis,  and  other 
infections  ;  and  this  fact,  in  conjunction  with  its  cancellous  structure,  accounts  for 
the  frequency  with  which  it  is  the  seat  of  gummatous  periostitis  and  tuberculous 
caries.  There  are  sometimes  little  circular  defects  in  the  body  of  the  sternum, 
through  which  an  abscess  may  pass  from  the  mediastinum  outward,  or  infections  from 
without  may  find  their  way  within  the  thorax.  They  are  congenital  defects  due  to 
a  failure  of  the  two  halves  of  the  body  of  the  sternum  to  unite. 

The  seven  depressions  on  each  side  of  the  sternum  for  the  reception  of  the 
cartilages  of  the  seven  true  ribs  are  so  shaped  that  the  upper  and  anterior  edges  of 
each  notch  are  more  prominent  and  larger  than  the  lower  and  posterior  edges. 
This  accounts  for  the  rarity  of  luxation  forward  of  these  cartilages  and  their  ribs  by 
the  forces  which  so  constantly  pull  the  ribs  upward  and  forward,  as  the  action  of  the 
scaleni  and  intercostals  in  violent  inspiratory  efforts,  that  of  the  pectorals  in  swinging 
by  the  hands  or  on  parallel  bars,  etc. 

Backward  dislocation  at  the  chondro-sternal  junction  is  even  rarer  ;  but  this  is 
because,  owing  to  the  elastic  curves  of  the  ribs,  the  sternum  and  the  anterior 
extremities  of  the  ribs  move  backward  together  on  the  application  of  direct  force  to 
the  front  of  the  chest. 

As  it  is  thus  movable,  and  is  supported  on  the  ends  of  elastic  levers  or  springs, 
the  sternum  is  rarely  fractured.  When  the  fracture  is  the  result  of  indirect  violence, 
it  is  often  associated  with  injuries  to  the  spine,  as  the  extreme  extension  or  extreme 
flexion,  which  is  the  common  cause  of  a  sternal  fracture,  must  necessarily  put  a 
severe  strain  on  the  thoracic  spine. 

In  extension  the  sternum  is  fixed  between  the  sterno-mastoids  and  sterno- 
hyoids and  thyroids  above  and  the  recti  and  diaphragm  below.  In  flexion  the 
force  may  be  transmitted  through  the  chin.  In  either  case  the  most  common  seat 
of  fracture  is  at  or  about  on  a  line  with  the  second  costal  cartilage,  because  (a)  the 
bone  there  is  narrowest  (Fig.  173),  and  (6)  at  that  level  lies  the  junction  between 
the  manubrium  and  body.  As  the  various  portions  of  the  bone  are  not  united 
until  about  twenty  years  of  age,  fracture  is  almost  unknown  before  that  time. 
Moreover,  during  that  period  the  symphysis  between  the  manubrium  and  the  body 
is  so  shaped  that,  together  with  the  natural  curve  forward  of  the  bone,  it  increases 
the  elasticity  of  the  sternum  and  enables  it  to  resist  both  direct  violence  and  tensile 
strain. 

The  projection '  at  the  union  between  the  manubrium  and  body  (angulus 
Ludovici)  is  sometimes  exceptionally  prominent,  and  when  this  is  noticed  for  the 
first  time  after  an  accident  or  an'  illness,  may  give  rise  to  the  erroneous  diagnosis  of 
fracture  or  of  bone  disease.  This  angle  is  increased  in  phthisis,  owing  to  the  reces- 
sion of  the  manubrium  ;  it  is  increased  in  emphysema,  as  the  second  ribs  carry  for- 
ward the  lower  border  of  the  manubrium. 

The  greater  thickness  and  strength  of  the  layer  of  fibrous  tissue  that  covers 


PRACTICAL    CONSIDERATIONS  :    THE   THORAX.  169 

the  posterior  surface  of  the  sternum,  as  compared  with  that  on  the  anterior  surface, 
account  for  the  rarity  with  which  effusions  of  blood  or  collections  of  purulent  fluid 
find  their  way  to  the  anterior  mediastinum. 

The  ribs,  in  addition  to  the  already  described  classification  into  sternal, 
asternal,  and  floating,  are  sometimes  designated  as  tipper  and  lower.  It  may  be 
well  to  mention  that  the  term  "  upper"  includes  the  first  six  ribs,  which  have  convex 
lower  borders,  give  origin  to  the  pectoralis  major  (an  elevator  of  the  ribs),  and  move 
upward  in  inspiration  ;  while  the  term  "lower"  applies  to  the  last  six  ribs,  which 
have  concave  lower  borders,  give  origin  to  the  diaphragm  (a  depressor  of  the  ribs), 
and  move  downward  in  inspiration. 

The  obliquity  of  the  ribs  adds  greatly  to  their  range  of  movement  in  respiration. 
The  most  oblique  rib,  the  longest,  and  the  most  movable — the  seventh — is  a  part 
of  the  wall  of  that  portion  of  the  thorax  that  contains  the  largest  amount  of  pulmo- 
nary tissue.  The  most  fixed  and  most  nearly  horizontal  of  the  ribs  (and  the  shortest 
of  the  sternal  ribs) — the  first — is  a  part  of  the  wall  where  the  least  lung  tissue  is  to 
be  found.  The  ribs  below  the  eighth  have  less  and  less  relation  to  the  lungs,  and 
become  both  shorter  and  more  horizontal.  They  have  increased  mobility  as  regards 
their  anterior  ends,  but  lessened  rotation  on  a  line  drawn  between  their  two  extrem- 
ities, the  movement  most  important  in  respiration. 

These  facts  have  relation  to  the  distribution  of  acute  and  chronic  disease  in 
the  lungs  :  the  acute  affecting  particularly  the  area  of  greatest  movement  and  vas- 
cularity, the  bases  ;  the  chronic,  the  area  of  lessened  mobility  and  expansion,  the 
apices. 

The  involuntary  partial  immobilization  of  the  chest-wall  after  injury  and  in 
inflammatory  affections  of  the  pleura  is  of  some  diagnostic  value,  as  is  also  the 
permanent  restriction  of  its  movements  following  the  contraction  of  old  adhesions, 
as  after  a  pleurisy,  or  pleuro-pneumonia,  or  fibroid  phthisis. 

The  obliquity  of  the  ribs  serves  also  the  purpose  of  securing  the  necessary 
expansion  of  the  chest  with  the  least  possible  motion  in  the  joints  between  the  ribs 
and  the  spine  and  between  the  cartilages  and  the  sternum.  They  are  thus  but  little 
liable  to  strain,  and,  in  spite  of  their  unceasing  movement  during  life,  are  very  rarely 
the  seat  of  either  dislocation  or  disease. 

At  the  articulation  of  the  ribs  with  the  spine  the  provision  for  preventing  the 
ascent  of  the  ribs  during  the  action  of  the  inspiratory  muscles  (similar  to  that  at  the 
costo-sternal  junction)  is  seen  in  the  fact  that  the  articulating  surface  of  the  upper 
vertebra  entering  into  the  joint  stands  out  more  boldly  than  that  of  the  lower  one. 
The  participation  of  the  intervertebral  disks  in  the  costo-vertebral  articulation  gives 
greater  safety  to  those  joints  and  adds  to  the  elasticity  of  the  whole  thorax  by 
furnishing  a  resilient  buffer  which  takes  up  and  distributes  forces  directed  against 
the  chest-wall. 

Variation  in  the  development  of  the  costal  element  of  the  seventh  cervical 
vertebra  (page  129)  may  result  in  the  production  of  a  cervical  rib.  This,  growing 
beyond  its  ordinary  limits,  sometimes  reaches  half-way  to  the  sternum,  running 
parallel  to  the  first  rib,  with  which  its  anterior  end  is  sometimes  joined.  Occasion- 
ally a  process  grows  up  from  the  first  rib  to  meet  it.  This,  or  the  cervical  rib  itself, 
may  raise  the  subclavian  artery  and  give  rise  to  a  mistaken  diagnosis  of  aneurism, 
or  may  be  thought  to  indicate  chronic  (tuberculous  or  syphilitic)  infection  of  bone, 
and  lead  to  unnecessary  operation  or  treatment. 

As  a  result  of  rickets,  changes  often  take  place  at  the  chondro-costal  junctions, 
causing  beaded  ribs  when  a  few  bones  only  are  affected,  or  the  "rickety  rosary" 
when  the  enlargements  are  bilateral  and  numerous. 

The  ribs  most  frequently  broken  are  the  sixth,  seventh,  and  eighth  ;  the  first 
and  second  are  protected  by  the  clavicle  ;  the  lower  two  by  their  small  size  and  great 
mobility.  The  most  common  form  of  muscular  action  causing  fracture  is  coughing  ; 
sneezing  and  lifting  heavy  weights  have  had  the  same  effect.  The  lower  ribs  are 
most  frequently  broken  in  this  way.  When  the  first  rib  is  broken,  a  character- 
istic symptom  is  said  to  be  pain  behind  the  upper  part  of  the  sternum  on  lifting 
with  the  hand  on  the  injured  side.  This  may  be  due  to  the  fact  that  the  first 
thoracic  nerve  lies  for  about  two  inches  in  contact  with  the  under  surface  of  the  first 


170  HUMAN   ANATOMY. 

rib,  and  ends  at  or  near  the  region  mentioned,  pain  being  often  referred  to  the 
peripheral  ends  of  sensory  nerves. 

In  fractures  by  indirect  violence  (when  the  sternum  and  spine  are  forced 
together),  the  theoretical  point  of  fracture  would  be  at  or  about  the  summit  of  the 
arch  ;  but  practically  it  is  often  found  very  near  the  point  at  which  the  force  is  apt 
to  be  received, — -i.e. ,  an  inch  or  two  outside  of  the  sternal  extremity. 

Unless  the  force  has  been  great,  there  is  but  little  displacement  in  fracture  of  a 
rib,  owing  to  the  splinting  of  the  bone  between  the  two  sets  of  intercostal  muscles 
above  and  below  it.  Shortening  is  absent,  unless  an  extensive  crush  of  the  whole 
side  of  the  chest  has  occurred,  because  the  two  ends  of  the  bone  are  fixed,  and 
because  of  the  unbroken  bones  above  and  below  the  fractured  one.  The  complica- 
tions are  those  obviously  due  to  the  proximity  of  the  pleura  and  lung  on  the  inner 
surface  of  the  fracture,  the  common  results  of  wounds  of  those  structures  being 
various  degrees  of  haemothorax,  or  pneumothorax,  or  sometimes  (by  valvular  action) 
emphysema  of  the  cellular  tissue  of  the  trunk  (page  1865). 

Broken  ribs  always  unite  with  a  considerable  amount  of  ensheathing  or  pro- 
visional callus,  due  to  the  motion  which  to  some  degree  must  be  present  between 
the  fragments  during  the  process  of  union. 

Rupture  of  an  intercostal  artery  (unless  associated  with  a  wound  of  the  pleura) 
is  not  usually  a  serious  complication  ;  but  occasionally  it  is  necessary  to  arrest 
hemorrhage  from  this  vessel.  It  lies  between  the  inner  and  outer  intercostal  muscles 
in  the  groove  running  along  the  lower  part  of  the  inner  surface  of  each  rib.  The 
collateral  branch  runs  near  the  upper  surface  of  the  ribs.  Midway  between  the  ribs 
is,  therefore,  the  safest  place  to  introduce  a  trocar  or  to  make  an  incision  in  opening 
the  chest.  The  intercostal  spaces  are  wider  in  the  antero-lateral  parts  of  the  chest 
than  they  are  more  posteriorly,  especially  in  the  neighborhood  of  the  seventh  rib  ; 
they  are  narrowest  in  close  proximity  to  the  sternum  and  spine.  They  can  be 
widened  by  bending  the  body  to  the  opposite  side. 

For  paracentesis  of  the  thorax  the  centre  of  the  sixth  or  seventh  space  should  be 
selected  in  the  mid-axillary  line.  The  lower  spaces  are  in  too  close  proximity  to  the 
diaphragm,  especially  on  the  right  side.  More  anteriorly  it  is  also  in  danger  ;  farther 
posteriorly  the  intercostal  artery  (which  runs  more  horizontally  than  the  ribs) 
crosses  the  space  obliquely,  and  behind  the  angles  the  ribs  are  covered  by  the  thick 
muscles  of  the  back. 

The  ribs  are  frequently  subject  to  infectious  disease.  Syphilis  and  tubercu- 
losis often  produce  periostitis  or  caries,  and  they  are  more  often  the  seat  of  post- 
typhoidal  osteitis  than  any  other  bones  of  the  skeleton.  This  is  due  to  their 
subcutaneous  position  exposing  them  to  frequent  traumatisms  and  to  the  similar 
effects  produced  by  the  numerous  strains  through  muscular  action  in  coughing  and 
sneezing  and  in  lifting  or  straining. 

Pus  is  very  apt  to  travel  along  the  loose  connective  tissue  between  the  two  planes 
of  intercostal  muscles,  and  it  is  therefore  unusual  to  find  suppurative  disease  confined 
to  one  rib,  or  even  to  the  immediate  vicinity  of  its  point  of  origin. 

No  instance  of  traumatic  separation  of  the  epiphysis  of  either  the  head  or  the 
tuberosity  of  a  rib  has  been  recorded. 

The  internal  mammary  artery  runs  from  above  downward  beneath  the  cartilages 
about  half  an  inch  from  the  sternum. 

Landmarks. — The  oblique  elevations  formed  by  the  ribs  can  usually  be  seen 
extending  downward  from  the  axillary  region.  The  upper  ribs  are  covered  by  the 
great  pectoral,  but  beneath  its  lower  border  the  ribs  from  the  sixth  to  the  tenth 
can  often  be  seen.  The  lower  border  of  the  great  pectoral  follows  the  direction  of 
the  fifth  costal  cartilage. 

The  curved  arch  of  the  costal  cartilages  is  frequently  plainly  visible,  and  is 
accentuated  during  forced  expiration' and  when  a  superincumbent  weight  is  held  up 
by  the  trunk  and  arms.  In  short  persons  the  arch  is  commonly  flatter  than  in  tall 
ones. 

In  counting  the  ribs  it  is  well  to  begin  with  the  second,  which  is  easily  identified 
by  its  relation  to  the  ridge  between  the  manubrium  and  body  of  the  sternum. 

The  nipple  is  usually  over  the  fourth  intercostal  space,  somewhat  less  than  2.5 


PRACTICAL   CONSIDERATIONS  :    THE   THORAX.  171 

centimetres  (one  inch)  external  to  the  costo-chondral  junction,  or  about  ten  centi- 
metres (four  inches)  from  the  middle  line.  Its  position  is  variable,  and  is  much 
lower  in  fat  persons,  especially  females.  In  emphysema  the  nipple  may  remain 
stationary,  while  the  upper  ribs  ascend,  and  it  may  be  opposite  the  fifth,  sixth, 
seventh,  or  even  the  eighth  rib.  In  phthisis  with  a  shallow  depressed  chest  it  may 
be  opposite  the  fourth  rib.  A  line  drawn  horizontally  from  the  nipple  around  the 
chest  is  on  a  level  with  the  sixth  intercostal  space  at  the  mid-axillary  line. 

A  horizontal  line  around  the  trunk  on  the  level  of  the  angle  of  the  scapula  (the 
arms  hanging  down)  would  traverse  the  sternum  between  the  fourth  and  fifth  ribs, 
the  fifth  rib  at  the  nipple  line,  and  the  ninth  rib  at  the  vertebral  column  (Treves). 

The  sternum  is  subcutaneous  in  the  groove  between  the  pectoral  muscles. 
Near  the  upper  third  the  ridge  between  the  manubrium  and  body  may  be  seen  or 
felt.  It  is  on  a  level  with  the  second  costal  cartilage.  This  cartilage  projects  for- 
ward more  than  the  others.  As  the  origins  of  the  pectoral  muscles  diverge  the 
sternal  groove  becomes  broader.  It  ends  at  the  lower  portion  of  the  body  of  the 
sternum  in  a  slight  projection  usually  seen  and  easily  felt.  This  marks  the  upper 
limit  of  the  "  infrasternal  depression"  {epigastric  fossa,  scrobiculus  cordis*),  the 
floor  of  which  is  over  the  ensiform  process,  and  which  is  bounded  laterally  by  the 
seventh  costal  cartilages  and  inferiorly  by  the  upper  ends  of  the  recti  muscles.  In 
many  abdominal  diseases,  and  sometimes  after  laparotomies,  the  obliteration  of  this 
depression  (by  the  occurrence  of  tympany)  is  an  important  clinical  symptom. 

When  the  arm  is  raised,  the  highest  visible  digitation  of  the  serratus  corre- 
sponds to  the  fifth  rib  ;  the  largest  is  that  attached  to  the  sixth  rib. 

During  expiration  the  upper  end  of  the  sternum  is  on  a  level  with  the  second 
dorsal  intervertebral  disk  ;  the  line  between  the  manubrium  and  body  is  on  a  level 
with  the  fifth  thoracic  vertebra  ;  the  junction  of  the  sternal  body  and  the  ensiform 
process  is  opposite  the  lower  part  of  the  ninth  thoracic  vertebra. 

The  eleventh  and  twelfth  ribs  can  be  felt  as  blunt  bony  projections  directed 
downward  and  outward  just  outside  the  erector  spinae  muscles. 

(The  relations  of  the  various  thoracic  viscera  to  the  chest-wall  will  be  con- 
sidered in  connection  with  the  anatomy  of  the  former. ) 


THE  SKULL. 

The  head  consists  of  the  cranium  and  the  face.  The  former  is  the  brain-case  ; 
the  latter  is  chiefly  concerned  in  forming  the  jaws.  The  head  also  contains  the 
terminal  organs  of  four  special  senses.  That  of  hearing  is  entirely  inside  one  of  the 
cranial  bones,  while  the  organs  of  sight  and  of  smell  lie  in  cavities  formed  partly  by 
cranial  and  partly  by  facial  bones.  The  special  organ  of  taste,  a  part  of  the  surface 
of  the  tongue,  is  in  the  mouth,  bounded  wholly  by  facial  bones.  Thus,  while  the 
cranial  bones  have  a  share  in  forming  the  face,  no  facial  bone  has  any  part  in  forming 
the  brain-case.  The  latter  is  an  egg-shaped  cavity  which  communicates  by  a  large 
opening — the  foramen  magnum — with  the  spinal  canal,  through  which  the  spinal  cord 
passes  down  from  the  brain.  The  brain-case  has  many  smaller  openings  in  the  base, 
through  which  nerves  escape  both  to  the  face  and  to  a  large  part  of  the  body  and 
blood-vessels  pass  for  the  nutrition  of  the  brain  and  its  membranes  and  the  walls  of 
the  skull. 

As  the  bones  of  the  head  can  be  separated  in  a  young  subject,  it  is  customary 
to  describe  every  bone  by  itself.  It  is  too  often  forgotten  that  this  knowledge  is 
merely  a  means  to  an  end, — namely,  the  understanding  of  the  skull  as  a  whole.  In 
the  following  account  this  end  is  kept  constantly  in  view. 

THE   CRANIUM. 

The  cranial  cavity  is  formed  by  eight  bones  :  the  occipital,  the  sphenoid,  the 
two  temporals,  the  ethmoid,  'the.  frontal,  and  the  two  parietals.  The  cranium  consists 
of  the  vault  and  the  base.  The  vault  is  formed  by  the  parietals,  the  greater  part  of 
the  frontal,  and  a  part  of  the  sphenoid,  of  the  temporals,  and  of  the  occipital. 

The  base  of  the  cranium  is  divided  into  three  fossa?  extending  across  the  skull. 
The  posterior  fossa  is  the  lowest  ;  it  opens  by  the  foramen  magnum  into  the  spinal 
canal,  and  contains  the  cerebellum,  the  medulla,  and  the  pons.  The  middle  one  is 
narrow  at  the  centre  and  expands  laterally  into  the  temporal  regions.  The  anterior 
is  the  highest,  lying  above  the  orbits  and  the  nose.  The  anterior  fossa  transmits  the 
olfactory  nerves,  the  middle  the  optic,  the  posterior  the  auditory  and  the  glosso- 
pharyngeal, the  nerve  of  taste. 

THE   OCCIPITAL    BONE. 

The  occipital  bone1  is  divided  for  description  into  an  anterior  part,  the  basilar  ; 
two  lateral  ones,  the  condylar ;  and  a  posterior  one,  the  tabular  or  squamous  portion. 
These  correspond  to  the  basi-occipital ,  the  exoccipital,  and  the  supra-occipital  of 
comparative  anatomy.  They  all  develop  from  separate  centres  and  bound  the 
foramen  magnum,"1  a  nearly  circular  opening,  transmitting  the  spinal  cord  with  its 
enveloping  membranes.  The  spinal  accessory  nerves  and  the  vertebral  arteries 
ascend  within  the  latter  from  the  cavity  of  the  spine  to  that  of  the  cranium. 

The  basilar  portion  :i  bounding  the  foramen  magnum  in  front  is  originally  rough 
anteriorly,  but  shortly  after  puberty  it  coossifies  with  the  body  of  the  sphenoid.  Its 
superior  surface  is  smooth  and  concave  and  supports  the  medulla  oblongata.  Just 
internal  to  the  edges  is  a  very  shallow  groove  for  the  inferior  petrosal  sinus.  The 
inferior  surface  is  smooth  for  about  one  centimetre  in  front  of  the  foramen  magnum, 
and  rough  in  front  of  this  for  the  rectus  capitis  anticus  major  and  minor.  In  the  mid- 
dle line  at  the  junction  of  the  rough  and  smooth  surfaces  is  the  pharyngeal  tubercle,* 
Very  rarely  this  aspect  presents  a  depression,  the  pharyngeal  fossa.  Sometimes 
there  is  a  facet  near  the  edge  of  the  foramen  for  the  anterior  arch  of  the  atlas.  Also, 
there  may  be  a  tubercle  on  the  posterior  part  of  the  basilar  portion  against  which  the 
odontoid  process  may  rest,  called  the  third  condyle.      Laterally,  the  basilar  portion 

1  Os  occipitale.     -  Foramen  occipitale  magnum.     '!  Parsbasilaris.     4Tuberculum  pharyngeum. 
172 


THE    OCCIPITAL    BONE. 


173 


is  separated  by  a  suture,  the  petro-occipital,  containing  cartilage,  from  the  petrous 
portion  of  the  temporal. 

Each  condylar  portion  '  (exoccipital)  presents  on  the  inferior  surface  an  oval 
articular  swelling,  the  condyle,  which  rests  in  the  hollow  on  the  atlas.  They  are 
placed  on  each  side  of  the  front  half  of  the  foramen  magnum.  The  hind  ends  reach 
almost  precisely  to  the  middle  of  the  aperture,  and  anteriorly  they  extend  to  the  line 
of  the  anterior  border,  their  long  axes  converging  in  front.  The  articular  surface, 
which  is  convex  in  the  line  of  the  long  axis,  faces  downward  and  outward.  The  curve 
it  presents  varies  greatly.  In  some  cases  it  is  nearly  regular,  in  others  the  front  and 
back  halves  almost  meet  at  an  angle.  There  is  usually  a  constriction  of  the  articular 
surface  at  the  middle,  where  it  may  be  crossed  by  a  groove  or  a  ridge.  On  the  thick 
inner  border  of  each  condyle  is  a  tubercle  for  the  odontoid  ligament.  Behind  the 
condyle  is  a.  fossa,  into  which  usually  opens  the  inconstant  posterior  condyloid  fora- 
men,2 transmitting  a  vein.  In  front  of  the  base  of  the  condyle  at  its  outer  border  is 
the  constant  anterior  condyloid  foramen, s  the  termination  of  a  canal,  from  five  to  ten 
millimetres  long,  which  pierces  the  bone  above  the  condyle  and  transmits  the  hypo- 


Fig.  192. 


Highest  curved  line 
Superior  curved  line 


Inferior  curved  line 


dyloid  fora- 
Rect.  capit.  lateralis 


Jugular  process 

Jugular  notch 
Pharyngeal  tubercle 


dyloid  forame 
Red.  capit.  antit 
Superior  constrictor 
Red.  capit.  antic.  ma_ 


Occipital  bone,  external  surface,  from  below. 

glossal  nerve  and,  usually,  a  branch  from  the  ascending  pharyngeal  artery  and  vein 
or  veins;  Tt  is  sometimes  divided  into  two.  The  bone  projects  outward  from  the 
condyle  as  the  jugular  process,  *  which  is  enlarged  at  its  outer  end  where  it  coossifies 
with  the  petrous  portion  of  the  temporal.  This  enlargement,  moreover,  extends 
downward  as  the  paroccipital  process,  which  shows  its  greatest  development  in  odd- 
toed  ungulates.  In  man  it  is  usually  very  small,  but  it  may  be  large  and,  very  rarely, 
pin  the  atlas.  The  concave  front  of  the  jugular  process  and  the  bone  extending 
forward  on  its  inner  side  form  the  jugular  notch?  which  bounds  the  posterior  lacer- 
ated foramen G  behind  and  internally.  This  is  completed  by  the  temporal  bone.  A 
very  small  point,  the  anterior  jugular  process,  marks  the  front  of  the  foramen.  A 
little  behind  this  a  larger  though  very  delicate  spine,  the  intrajugular  process, 
reaches  across,  marking  off  a  small  anterior  part  of  the  jugular  foramen  for  the 
passage  of  the  ninth,  tenth,  and  eleventh  nerves  from  the  larger  one  behind  for  the 
lateral  sinus.  Sometimes  the  front  "of  the  jugular  process  is  a  smooth  surface 
bounded  below  by  a  ridge  to  which  is  attached  the  rectus  capitis  lateralis,  and  above 
by  a  short  border  marking  off  a  fossa  on  the  upper  surface  of  the  bone  ;  occasionally 

1  Pars  lateralis.     -Canalis  condyloideus.     3  Canalis  bypoglossi.     4  Processus  jugularis.     5  Incisura  jugularis.     °  Foramen 
ugulare. 


174 


HUMAN    ANATOMY. 


the  latter  ridge  is  wanting,  the  groove  of  the  lateral  sinus  curving  over  the  jugular 
process.  The  upper  surface  of  the  lateral  portion  of  the  process  shows  on  its  inner 
side  the  entrance  of  the  anterior  condyloid  foramen,  which  is  really  a  short  canal. 
Above  and  anterior  to  this  is  a  slight  swelling,  the  jugular  tubercle.  The  upper 
surface  of  the  jugular  process  is  marked  by  the  termination  of  the  groove  of  the 
lateral  sinus,  which  curves  round  an  upward  projection  of  the  process.  In  some 
cases,  as  just  mentioned,  the  groove  is  depressed  into  a  deep  hollow.  The  inner 
opening  of  the  posterior  condyloid  foramen,  when  present,  is  connected  with  the 
lateral  sinus. 

The  squamous  portion  '  forms  the  lower  and  back  part  of  the  skull.  Below  it 
contributes  the  posterior  boundary  of  the  foramen  magnum  and  joins  the  exoccipitals. 
The  lateral  borders  meet  above  at  a  sharp  angle.  These  borders  may  be  subdivided 
into  a  lower  part,  which  ascends  nearly  vertically  in  articulation  with  the  mastoid 
part  of  the  temporal,  and  into  a  higher  part,  very  serrated  and  joining  the  parietal. 
A  slight  angle  lies  on  either  side  at  the  junction  of  these  two  divisions. 

Fig.  193. 


Jugular  process- 
Jugular  notch 


Groove  for  lateral  sinus 
— Jugular  tubercle 


Occipital  bone,  internal  surface,  from  before. 

The  posterior  surface  is  marked  by  a  prominence,  somewhat  below  the 
middle,  the  external  occipital  protubei'ance ,2  to  which  is  attached  the  ligamentum 
nuchae.  This  tuberosity  varies  greatly  in  development.  From  it  the  superior  curved 
line%  extends  laterally  to  the  above-mentioned  angle.  To  this  line  are  attached  a 
series  of  muscles  which  form  the  contour  of  the  back  of  the  neck,  chiefly  the  trapezius 
and  part  of  the  sterno-cleido-mastoid.  A  short  and  varying  distance  above  the  supe- 
rior ridge  is  often  seen  the  so-called  highest  curved  line.*  It  is  usually  very  faint, 
and  may  curve  down  to  the  external  occipital  protuberance,  or  pass  above  it.  The 
epicranial  aponeurosis  and  part  of  the  occipitalis  spring  from  this  line.  The  surface 
of  the  bone  above  the  level  of  the  protuberance  is  smooth  ;  below  it  is  rather  rough 
and  irregular.  The  torus  occipitalis  transverstis  is  an  occasional  prominence  in- 
volving the  protuberance  and  extending  laterally  along  the  superior  curved  line. 
It  sometimes  involves  the  space  between  that  line  and  the  highest  one.  The  upper 
border  of  the  swelling  may  have  a  median  concavity.      In  the  mid-line  a  slight  ridge, 


-  Protuberantia  occipitalis  externa.     3Line 


1  nuchae  suprema. 


DEVELOPMENT    OF   THE    OCCIPITAL    BONE. 


175 


edian  fissure 


the  external  occipital  crest, x  runs  from  the  protuberance  to  the  foramen  magnum. 
Above  the  middle  of  this  crest  the  inferior  curved  line2  leaves  it  to  extend  outward  and 
downward  to  the  border  of  the  bone.  The  inner  part  of  this  line  is  rough,  the  outer 
indistinct.      Below  this  line  there  is  usually  a  depression  on  either  side  of  the  crest. 

The  internal  surface  of  the  squamous  portion  is  divided  into  four  depressions 
or  fosses  ;  the  upper  two  lodge  the  occipital  lobes  of  the  cerebrum  and  the  lower  two 
the  lateral  lobes  of  the  cerebellum.  Below  the  middle  is  the  internal  occipital  pro- 
tuberance* approximately  opposite  to  the  outer.  A  ridge  runs  from  the  apex  of  the 
bone  to  the  protuberance,  and  is  continued  as  the  internal  occipital  crest*  to  the 
foramen  magnum.  Very  often  the  second  part  of  this  ridge  divides  shortly  after  its 
origin,  so  as  to  enclose  a  depression,  the  vermian  fossa,  so  called  because  it  is  below 
the  middle  lobe,  or  vermis,  of  the  cerebellum.  A  ridge  runs  transversely  from  the 
protuberance  to  the  lateral  angle  of  the  bone.  The  superior  vertical  ridge  may  be 
grooved  for  the  superior  longitudinal  sinus  and  the  transverse  ridge  for  the  lateral 
sinus.  More  frequently  the  longitudinal  sinus  lies  to  one  side  of  the  vertical  ridge 
and  is  continued  into  one  of  the  lateral  ones,  much  larger  than  its  fellow,  and  usually 
the  right,   which  lies  above   the 

transverse  ridge,    and   shows   in  Fig.  194. 

the  bone  no  communication  with 
the  smaller,  which  lies  in  or  above 
the  other  ridge.  There  are  many 
variations  in  this  arrangement,  of 
which  the  rarest  is  a  symmetrical 
course  and  division  of  the  supe- 
rior groove.  A  single  or  a  bifur- 
cated groove  is  sometimes  found 
on  the  internal  crest. 

Development. — Four  cen- 
tres appearin  the  cartilage  around 
the  foramen  magnum  about  the 
eighth  week  of  fcetal  life :  one  for 
the  basilar,  one  for  each  exoccipi- 
tal,  and  one  (or  more  probably 
a  pair  that  speedily  fuse)  for  the 
lower  part  of  the  squamous  por- 
tion, the  supra-occipital.  A  week 
or  so  later  two  nuclei  appear  in 
the  membrane  above  the  latter, 
from  which  a  strip  of  bone  de- 
velops which  soon  joins  it.  From 
this  upper  ossification,  the  supe- 
rior occipital,  is  developed  all  the 
upper  part  of  the  squamous  por- 
tion, including  the  external  occipital  protuberance  and  the  superior  curved  line.0 
Occasionally  still  another  nucleus  appears  on  each  side,  anterior  and  external  to  the 
preceding,  which  probably  accounts  for  certain  separate  ossifications  often  found  in 
the  lambdoidal  suture.  The  squamous  part  shows  a  median  cleft  above,  which 
quickly  disappears,  two  lateral  ones  between  the  ossifications,  which  persist  till 
birth,  and  a  notch  at  the  posterior  border  of  the  foramen  magnum.  The  squa- 
mous portion  joins  the  exoccipitals  in  the  course  of  the  second  or  third  year.  The 
latter  begin  to  unite  with  the  basilar  a  year  or  so  later.  None  of  these  sutures,  es- 
pecially the  latter,  is  completely  closed  before  the  seventh  year,  or  even  later. 
The  front  parts  of  the  condyles  are  formed  from  the  basilar,  which  joins  the  ex- 
occipitals at  the  anterior  condyloid  foramina.  Separate  ossifications,  large  Wormian 
bones,6  are  found  in  the  suture  between  the  squamous  portion  and  the  parietals. 
Sometimes  there  is  a  large  median  triangular  one  which  is  interpreted  as  the  result 
of  a  want  of  union  of  the  usual  superior  centre  of  the  squamous  portion,  and  said  to 

"Consult  Stieda:  Anatomische  Hefte,  iv.,  1S92,  and  Debierre  :  Journ.  de  l'Anat.  et  de  la 
Phys.,  1S95. 

1  Lima  nuchae  mediana.     -h.  nuchae  inferior.     3Protub.  occip.  interna.    'Crista  occipitalis   interna.    'Ossa  suturarum. 


•-^Y^Fissure  be- 
tween upper 
and  lower 
portions 

occipital 


•ipital 
Occipital  bone  at  birth,  from  before. 


condyloid  foramen 


iy6 


HUMAN    ANATOMY. 


be  -the  homologue  of  the  interparietal  bone.  This  interpretation  is  inconsistent  with 
the  history  of  ossification.  Kerkring  has  described  an  occasional  triangular  minute 
piece  of  bone  which  appears  during  the  fifth  month  in  the  notch  at  the  back  of  the 
foramen  magnum,  and  is  fused  before  birth.  We  have  specimens  which  imply  that 
it  is,  or  may  be,  originally  double.  Improved  methods  of  investigation  will  prob- 
ably show  that  this  bone  is  not  uncommon.  The  cerebral  side  of  the  basilar  is 
fused  with  the  sphenoid  by  seventeen  ;  the  lower  side  unites  later,  probably  before 
twenty. 

THE   TEMPORAL    BONE. 

The  plan  of  the  organ  of  hearing  must  be  known  to  understand  the  temporal 

bone.1     The  external  ear,  besides  the  auricle,  consists  of  a  cartilaginous  and  bony 

tube,  the  external  auditory  meatus,'1,  leading  to  the  membrane  of  the  tympanum  which 

closes  it.      The  middle  ear,  the  cavity  of  the  tympanum,  is  a  space  internal  to  the 

Fig.  195. 

squamous  portion 


Supramastoid  crest 

Occipitalis 

Spina  suprameatum 


Auricularis  posterior- 


~~*-~  _-  '--   ~^y\  Zygoma 


Masseter 
Anterior  root  of  zygoma 
oid  fossa 

APEX  OF  PETROUS  PORTION 
Glaserian  fissure 


Trachelo-mastoid 
MASTOID  PORTION- 
Tympan 


-mastoid  fissure 

Mastoid  process 
External  auditory  meatus' 

TYMPANIC    PORTION     / 
Vaginal  process 

Right  temporal  bone,  external  aspect. 

membrane,  opening  through  the  Eustachian  tube  into  the  throat,  and  communicating 
behind  with  cavities  in  the  bone.  It  is  lined  with  mucous  membrane  and  is  crossed 
by  a  chain  of  small  bones,  the  ear  ossicles,  the  embryological  importance  of  which  is 
explained  elsewhere.  The  internal  ear  is  a  complicated  system  of  cavities  in  the 
substance  of  the  bone  containing  the  organ  of  hearing  connected  with  the  brain  by 
the  auditory  nerve,  which  leaves  the  bone  through  a  canal,  the  internal  auditory 
meatus. 

Development  shows  that  the  bone  consists  of  the  following  three  parts.  (1)  The 
petro-mastoid,  the  petrous  part  of  which  is  first  found  surrounding  the  special 
apparatus  of  the  organ  of  hearing,  constituting  the  internal  ear,  while  the  mastoid 
process  is  a  much  later  outgrowth.  (2)  The  tympanic  portion,  which  at  birth  is  a 
ring,  incomplete  above,  encloses  the  membrane  of  the  tympanum  as  a  frame  holds 
a  glass.  This  ring  grows  out  later  into  a  cylinder,  still  open  above,  which  forms  the 
external  auditory  meatus.     Not  all  its  growth,   however,   is  outward,  since  a  part 

1  Os  temporale.     -  Meatus  acusticus  externus. 


THE   TEMPORAL    BONE. 


177 


expands  forward  and  deeper  than  the  original  ring,  making  the  front  part  of  the 
tympanic  plate,  bounding  the  cavity  of  the  tympanum  and  the  Eustachian  tube 
externally.  The  tympanic  cavity,  or  the  middle  ear,  lies  between  the  petro-mastoid 
and  the  tympanic  portion,  the  roof  and  floor  being  developed  from  the  former. 
(3)  The  squamous  portion  is  external  and  above.  It  forms  a  part  of  the  side  of  the 
skull,  the  roof  of  the  external  meatus  where  the  tympanic  portion  is  deficient,  the 
articulating  surface  for  the  jaw,  and  a  part  of  the  mastoid  process.  There  is  also  the 
long,  slender  styloid  process,  which  is  a  part  of  the  hyoid  bar  of  the  second  visceral 
arch  of  the  embryo.  It  begins  as  an  ossification  of  a  distinct  piece  of  cartilage,  but 
joins  the  petro-mastoid.      The  following  description  is  that  of  the  adult  bone. 

The  Squamous  Portion.1 — Most  of  this  is  a  thin  vertical  layer  forming  part 
of  the  wall  of  the  skull,  joined  below  by  a  horizontal  one  which  forms  a  small  part  of 
the  base  of  the  skull,  the  articulating  surface  for  the  jaw,  and  the  roof  of  the  external 

Fig.  196. 

Eminentia  articularis 


Eustachian  tube 


Glenoid  fossa. 

Postglenoid  tubercle 

Fissure  of  Glaser 

Tympanic  plate 


External  auditory  meatus 


Semicircular  canal 
Facial  canal 


Groove  for  lateral  sinus 
Horizontal  section  through  right  temporal  bone,  seen  from  below. 

auditory  meatus.  The  edge  of  the  vertical  part  is  convex  except  below.  The  upper 
and  posterior  borders  overlap  the  parietal  bone  by  a  broad  bevelled  surface.  The 
anterior  border  joins  the  great  wing  of  the  sphenoid,  overlapping  above  and  over- 
lapped below,  where  it  passes  into  the  horizontal  part.  The  posterior  angle  of  the 
vertical  portion  sends  downward  the  postauditory  process,  from  which  the  upper  part 
of  the  mastoid,  including  some  of  the  mastoid  cells,  is  developed.  The  squamo- 
mastoid  suture,  separating  this  from  the  mastoid  portion,  is  usually  lost  in  the  second 
year.  When  it  persists,  it  shows  that  the  anterior  portion  of  the  mastoid  down  to 
the  lower  border  of  the  external  meatus,  or  even  lower,  is  formed  from  the  squamosal. 
Its  surface  is  smoother  than  that  of  the  mastoid  proper.  A  small,  particularly 
smooth,  but  inconstant  patch  situated  on  the  level  of  the  upper  part  of  the  meatus, 
one  centimetre  or  more  behind  it,  marks  the  position  of  the  antrum.  The  thick- 
ness of  the  bone  at  this  place,  which  is   that  of  note-paper  in  the  infant  reaches 


i7S 


HUMAN   ANATOMY. 


six  millimetres  in  the  adult.  A  small,  sharp  prominence,  the  spina  suprameatum,  is 
found  just  behind  the  upper  part  of  the  meatus.  It  is  an  important  landmark  in  the 
surgery  of  the  region.  Just  posterior  to  it  is  usually  a  minute  venous  foramen. 
The  inner  side  of  the  squamous  portion,  besides  the  large  bevelled  articular  surface, 
presents  a  smooth  one,  forming  part  of  the  wall  and  floor  of  the  cranial  cavity.  This 
is  separated  from  the  petrous  portion  by  the  petro-sqnamous  suture,  which  is  closed 
early.  Two  grooves  for  branches  of  the  middle  meningeal  artery  diverge  from  its 
lower  border,  one  running  upward  and  the  other  backward.  The  front  of  the  hori- 
zontal part  forming  the  floor  is  rough  and  thick,  joining  the  great  wing  of  the 
sphenoid.  The  zygomatic  process^  projects  forward  from  the  outer  surface  of  the 
squamosal  to  complete  the  zygomatic  arch  with  the  malar,  which  it  joins  by  a 
serrated  end.  The  free  part  has  an  external  and  an  internal  surface,  a  rounded  bor- 
der below  and  a  sharp  edge  above.  The  latter,  which  receives  the  insertion  of  the 
temporal  fascia,  can  be  followed  back  to  the  origin  of  the  process.  The  zygoma 
has  two  roots.     The  posterior  root   passes   directly  backward  above  the  auditory 


Fig.  197. 
squamous  portion 


Zygo 
Groove  for  meningeal  artery 


PETROUS  PORTION 


Groove  for  lateral  sinus 
MASTOID  PORTION 


Styloid  process 


Aquasductus  cochlear 
Right  temporal  bone,  internal  aspect. 

meatus,  crosses  the  squamous  portion  above  the  postauditory  process,  and,  curving 
slightly  upward,  is  lost  at  the  notch  between  the  squamous  and  mastoid  portions. 
Its  hind  part  is  the  szipramastoid  crest,  which  joins  the  inferior  temporal  ridge  on 
the  parietal.  The  anterior  root  bends  sharply  inward.  It  is  grooved  above  for  the 
passage  of  the  fibres  of  the  temporal  muscle.  Its  lower  surface  forms  a  semi-cylin- 
drical transverse  elevation,  the  eminentia  artictdaris,2  the  front  part  of  the  articular 
cavity  of  the  lower  jaw.  Near  its  outer  end  is  a  tubercle  for  the  external  lateral 
ligament.  Just  in  front  of  the  auditory  meatus,  on  the  under  side  of  the  bone,  is 
the  smaller  postglenoid  tubercle,  sometimes  described  as  a  third  root.  The  glenoid 
fossa*  is  a  deep  hollow  on  the  under  side  of  the  squamous  portion,  with  its  greatest 
diameter  nearly  transverse,  but  passing  somewhat  forward  and  outward,  bounded 
externally  by  the  posterior  root  of  the  zygoma  ;  behind,  by  the  fissure  of  Glaser,i 
which  separates  it  from  the  tympanic  portion  ;  and  extends  forward  and  inward  to 
meet  the  inner  end  of  the  eminentia  articularis.  Both  glenoid  fossa  and  articular 
eminence  are  covered  with  cartilage.      The  bone  separating  the  glenoid  fossa  from 

1  Processus  zygomaticus.     2Tubercutum  articulare.     3  Fossa  maudibularis.     '  Fissura  petrotympanica. 


THE    TEMPORAL    BONE. 


179 


the  interior  of  the  cranium   is  very  thin.      Behind  the  glenoid  fossa  the  horizontal 
part  of  the  squamosal  forms  the  roof  of  the  external  auditory  meatus. 

The  Tympanic  Portion.'— The  tympanic  portion  of  the  temporal  bone 
appears  as  a  trumpet-shaped  layer  of  bone,  forming  all  but  the  roof  of  the  external 
auditory  meatus.  Its  edge  is  thin  in  front,  thick  below,  and  very  thin  behind,  where 
it  curls  up  before  the  mastoid  to  meet  the  postauricular  process  of  the  squamosal. 
It  is  separated  from  the  mastoid  by  the  minute  lympano- mastoid  fissure.  The  ante- 
rior part  of  the  tympanic  portion,  called  the  tympanic  plate,  runs  obliquely  forward, 
concealing  the  petrosal.  It  is  separated  from  the  glenoid  fossa  and  from  the  thick 
anterior  edge  of  the  squamosal  by  the  fissure  of  Glaser,  which  opens  into  the  tym- 
panic cavity.  The  outer  end  of  the  fissure  is  closed  ;  the  inner  part  is  double,  since 
a  thin  piece  of  the  petrous,  the  tegmen  tympani,  bends  down  between  the  squamous 
and  tympanic  portions.  The  lower  edge  of  the  tympanic  plate  ends  free.  A  part 
covering  the  base  of  the  styloid  process  is  the  vaginal  process,'2  which  sometimes 

splits  to  enclose  it.  „ 

F  Fig.  iq8. 


SQUAMOUS   PORTION 


Zygoma 


Articular  eminence 

Glenoid  fossa' 

Tegmen  tympani 

Glaserian  fissure 

TYMPANIC  PORTION 

Styloid  process' 

Stylo-mastoid  foramen 

Mastoid  process' 


Eustachian  tube 


Aquaeductus  cochleae 
PETRO-MASTOID  PORTION 
Jugular  fossa 


Joining  occipital 


Digastric  groov' 


Occipital  groove 
Right  temporal  bone  from  below. 

The  Petro-Mastoid  Portion.3  -This  part  of  the  temporal  bone  may  for 
convenience  of  description  be  subdivided  into  the  mastoid  and  the  petrous.  The 
mastoid  subdivision  forms  a  part  of  the  wall  of  the  skull  behind  the  tympanic. 
It  is  prolonged  downward  into  a  nipple-shaped  process,  the  outside  of  which  is  rough 
and  slightly  prominent.  On  its  lower  surface,  under  cover  of  the  apex,  is  the 
digastric  groovei  for  the  origin  of  the  posterior  belly  of  the  digastric  muscle.  Just 
internal  to  this,  at  the  very  edge  of  the  bone,  is  the  much  smaller  occipital  groove 
for  the  occipital  artery.  The  ridge  between  the  two  may  be  developed  into  a  para- 
mastoid process.  The  greater  part  of  the  internal  surface  is  occupied  by  a  broad  and 
deep  greove,'  running  obliquely  downward,  forward,  and  inward  for  the  lateral  sinus 
on  its  way  to  the  jugular  foramen.  The  direction  of  this  groove  is  very  uncertain. 
Sometimes  it  descends  gradually  ;  at  others  it  turns  far  forward  and  descends  nearly 
vertically.  In  the  latter  case  it  approaches  closer  than  otherwise  to  the  outer  wall 
of  the  skull,  but  the  distance  in  all  cases  is  very  variable  (Figs.  199,  200).  It 
may  be  only  a  few  millimetres.  As  it  descends  it  reaches  the  inner  side  of  the 
antrum  and  the  mastoid  cells.      It  is  separated  from  the  antrum  by  a  plate  some  six 

1  Pars  tympanica.    °  Vagina  processus  styloldeus.    3  Pars  petrosa  et  mastoidca.    Mncisura  raastoidca.    5  Sulcus  sigmoidcus. 


HUMAN    ANATOMY. 


millimetres  thick  in  early  childhood,  and  from  the  antrum  or  upper  mastoid  cells  by 
a  very  thin  one  in  adult  life.1  Behind  the  groove  a  small,  smooth  surface  forms  a 
part  of  the  cerebellar  fossa. 

Fig.  199. 
A  B 


Tympanic  cavity 


Tympanic  cavity 
Jugular  fossa 


Groove  for  lateral  sinus 


Groove  for  lateral 


Mastoid  canal 

Horizontal  sections  through  a  right  temporal  bone  with  slight  development  of  the  mastoid  cells.    A,  just  above  the 
floor'of  the  external  auditory  meatus;  B,  near  the  roof  of  the  same  canal. 

Fig.  200. 


■Groove  for 
lateral 
sinus 


A  small  canal,  the  mastoid  foramen,'1  transmitting  a  vein,  runs  from  the  sinus  to 
the  outside  of  the  bone,  which  it  sometimes  reaches  as  far  back  as  the  suture  between 
1  Clarke  :  Journal  of  Anatomy  and  Physiology,  vol.  xxvii,  1893. 

-  Foramen  mastoidcum. 


THE   TEMPORAL    BONE. 


-Area  cribrosa 
superior 

-Cut  wall  of  in- 
ternal meatus 

-Area  cribrosa 
media 

-Foramen  singu- 


uditory  meatus.     X  5- 


the  temporal  and  the  occipital.  The  interior  of  the  mastoid  process  contains  spaces, 
the  mastoid  cells,  to  be  described  later.  The  size  and  shape  of  the  mastoid  process 
are  very  variable.  The  rough  upper  border  of  the  mastoid  subdivision  forms  an 
entering  angle  with  the  squamosal,  into  which  fits  a  sharp  point  from  the  lower  bor- 
der of   the  parietal,  which  rests  on 

it    above.       Behind  and  below   the  Fig.  201. 

mastoid  joins  the  occipital  bone.  -»,, 

The  petrous  subdivision   is  .    \ 

an  elongated  pyramid  running  for-  --■        _^~^ 

ward   and    inward,    presenting  four  .  __!_JR;J8%lfe 

surfaces  (besides  the  base   covered 

by  the  mastoid),  four  borders,  and  gj| 

an  apex.    The  surfaces  are  the  supe-        "o^mis1  u  aflffl 

rior,  posterior,  inferior,  and  anterior.      Tractusspi—  '-'—  -lilt S 
The  superior  surface  slants        ralis  lillf* 

forward  and  downward  in  the  floor  'v 

of  the  middle  cerebral  fossa.  It  has 
the  following  features.  Above  the 
apex  there  is  a  depression '  for  the 

Gasserian    ganglion.      Just   external  Bottom  of  right  in 

to  this  the  bone  is  excessively  thin 

and  often  deficient,  so  as  to  leave  the  end  of  the  carotid  canal  uncovered.  Behind 
the  middle  of  the  pyramid  is  an  elevation,  nearly  at  right  angles  to  its  long  axis, 
caused  by  the  superior  semicircular  canal.  External  to  this  the  surface  is  made  of  a 
very  thin  plate  of  bone,  the  legmen  tympani,  which,  extending  outward  from  the 
petrous,  forms  the  roof  of  the  tympanum  and  of  its  continuation,  the  Eustachian 
tube.  Externally,  this  plate  bends  down  into  the  Glaserian  fissure,  so  that  its  edge 
may  appear  between  the  squamosal  and  tympanic  portions  (Fig.  198).    At  the  inner 

border  of  the  tegmen  tympani  near 
Fig.  202.  its  front  is  a  groove  leading  to  a  little 

rent  in  the  bone,  the  hiatus  Fallopii, 2 
through  which  passes  the  great  su- 
perficial petrosal  nerve.  A  minute 
opening,  more  external,  transmits 
the  smaller  superficial  petrosal  nerve. 
In  youth  the  outer  side  of  the  teg- 
men is  bounded  by  the  petro-squa- 
mous  suture. 

The  posterior  surface  forms 
a  part  of  the  posterior  cranial  fossa. 
The  chief  feature  is  the  internal 
auditory  meatus?  a  nearly  round 
canal  with  a  slight  groove  leading 
to  it  from  the  front.  Its  shorter 
posterior  wall  is  about  five  milli- 
metres long.  The  canal  is  closed  by 
a  plate  of  bone,  the  lamina  cribrosa 
(Fig.  201),  which  is  divided  by  the 
falciform  crest  into  a  smaller  fossa 
above  and  a  larger  one  below.  The 
former  has  an  opening  by  which  the 
facial  nerve  enters  its  canal,  the 
aqueduct  of  Fallopius.  Branches  of 
the  auditory  nerve  pass  through  minute  openings  in  both  fossae.  About  one  centi- 
metre behind  the  meatus  is  a  little  cleft,  the  aqu/zductus  vestibuli,i  entering  the  bone 
obliquely  from  below.  Higher  and  nearer  to  the  meatus  is  a  minute  depression,  the 
remnant  of  the  floccular  fossa,'  which  is  large  in  some  animals  and  in  the  infant.  It 
receives  a  fold  of  the  dura. 

The  inferior  surface  of  the  petrous  presents  in  front  a  large  rough  surface  for 

>  facialis.     3  Meatus  acusticus  interims.     4  Apertura  externa  aquaeductus  vcstibull. 


Petro-squamous  suture 


Internal  audi- 
tory meatus 
Internal  ear. 


Styloid  process 


HUMAN    ANATOMY. 


the  origin  of  the  levator  palati  and  tensor  tympani  muscles.  External  to  the  back 
of  this  is  the  round  orifice  of  the  carotid  canal1  ;  back  of  this,  and  more  internal,  is 
the  jugular  fossa.  This  presents  two  extreme  types,  entirely  different,  with  inter- 
mediate forms.  It  may  be  a  large  thimble-shaped  hollow,  the  edge  of  which  bounds 
the  venous  part  of  the  jugular  foramen  internally,  forming  a  large  reservoir  for  the 
blood  of  the  lateral  sinus  as  it  leaves  the  skull.  On  the  other  hand,  it  may  be  a 
small  flat  surface.  A  minute,  but  very  constant,  foramen  in  the  ridge  between  it  and 
the  carotid  canal  transmits  the  tympanic  branch  of  the  glosso-pharyngeal  nerve.  A 
minute  foramen,  usually  found  in  the  jugular  fossa,  transmits  the  auricular  branch  of 
the  vagus.  The  aquceductus  cochlea  ends  at  a  small  triangular  opening 2  in  front  of  the 
jugular  fossa,  close  to  the  inner  edge.  Behind  the  fossa  is  a  small  surface  where  the 
temporal  bone  is  united  to  the  occipital,  first  by  cartilage  and  then  by  bone.  The 
stylo-mastoid  foramen,  the  orifice  of  the  facial  canal  for  the  facial  nerve,  is  near 
the  outer  edge  of  this  surface.  The  stylo-mastoid  branch  of  the  posterior  auricular 
artery  enters  it. 

Fig.  203. 


SQUAMOUS  PORTION 


Hiatus  Fallopii 
Depression  for  Gasserian  g 
Eustachian  tube 

Carotid  canal 
APEX  OF  PETROUS 
Carotid  canal  (lower  end) 


Styloid  process 


Right  temporal  bone  from  before. 


The  anterior  surface  of  the  petrous  is  nearly  all  hidden  by  the  tympanic 
plate.  It  forms  the  inner  wall  of  the  cavity  of  the  tympanum  and  of  the  bony  part  of 
the  Eustachian  tube,  which  leaves  the  bone  in  the  entering  angle  between  this  surface 
of  the  petrous  and  the  tympanic.  The  features  of  this  surface  are  treated_  in  the 
section  on  the  ear.  The  processus  cockleariformis*  attached  like  a  shelf  to  this  outer 
wall,  divides  the  canal  for  the  tensor  tympani  muscle  from  the  Eustachian  tube 
below  it.  The  front  of  this  plate  can  be  seen  at  the  entering  angle,  where  the  bony 
tube  ends.  The  small  portion  of  the  outer  surface  of  the  petrous  which  is  visible 
,  is  in  front  of  this  point,  and  rests  against  the  inner  edge  of  the  great  wing  of  the 
sphenoid. 

The  superior  internal  border  of  the  petrous  is  a  prominent  ridge  in  the  base 
of  the  skull,  separating  the  middle  and  the  posterior  fossse.  The  tentorium  is 
attached  to  it.  The  superior  petrosal  sinus  runs  along  it  in  a  shallow  groove  within 
the  attached  border  of  the  tentorium.  Near  the  front  a  groove  by  which  the  fifth 
nerve  reaches  the  Gasserian  ganglion  crosses  this  border. 

The  inferior  internal  border  articulates  anteriorly  with  the  basilar  process  of 

1  Canalis  caroticus.     2  Apertura  externa  aquacductus  cochleae.     3  Septum  canalis  musculotubal. 


THE   TEMPORAL    BONE. 


183 


the  occipital  bone,  and  is  separated  posteriorly  from  the  occipital  by  the  jugular 
foramen.  A  little  spine  on  the  edge  of  the  thimble-shaped  fossa,  or  on  the  plane 
surface  that  may  take  its  place,  the  intrajugular  process,  joins  the  corresponding 
process  of  the  occipital  either  directly  or  by  ligament,  so  as  to  divide  the  foramen 
into  two  parts,  the  posterior  for  the  vein,  the  anterior  for  nerves.  In  front  of  the 
foramen  a  small  groove  on  the  cerebral  edge  of  this  border  marks  the  position  of  the 
inferior  petrosal  sinus. 

The  superior  and  the  inferior  external  borders  are  concealed  by  the  other 
elements  of  the  temporal,  except  near  the  front,  where  they  bound  the  surface  which 
touches  the  sphenoid. 

The  apex  of  the  petrous  is  mostly  occupied  by  the  opening  of  the  carotid  canal. 

The  styloid  process  is  a  part  of  the  hyoid  bar  (from  the  second  branchial 
arch),  which  joins  the  temporal  under  cover  of  the  vaginal  process.  It  is  thick  at  its 
origin,  but  presently  becomes  thinner  and  ends  in  a  sharp  point.  It  is  usually  about 
an  inch  long,  but  varies  greatly.  It  runs  downward,  forward,  and  inward,  and  is  con- 
tinued as  the  stylo-hyoid  ligament  to  the  lesser  horn  of  the  hyoid.  Three  muscles, 
the  stylo-glossus,  stylo-hyoid,  and  stylo-pharyngeus,  diverge  from  it  to  the  tongue, 
the  hyoid  bone,  and  the  pharynx.  An  ill-defined  process  of  the  cervical  fascia,  the 
stylo- maxillary  ligament,  passes  from  it  to  the  back  of  the  ramus  of  the  lower  jaw. 


CAVITIES   AND   PASSAGES   WITHIN   THE  TEMPORAL   BONE. 

The  Cavity  of  the  Tympanum.1 — The  tympanic  cavity  is  a  narrow  cleft 
about  five  millimetres  broad  at  the  top,  narrowing  to  a  mere  line  below.  It  measures 
about  fifteen  millimetres 

vertically  and  from  be-  Fig.  204. 

fore  backward.  It  is 
bounded  internally  by 
the  petrous  ;  above  by 
a  projection  from  it,  the 
tegmen  tympani ;  below 
by  the  jugular  fossa,  or, 
if  this  be  very  small,  by 
the  bone  external  to  it  ; 
externally  by  the  tym- 
panic portion  of  the 
bone  and  the  membrane, 
except  at  the  top,  where 
the  squamosal  is  ex- 
ternal to  it.  The  part 
above  the  level  of  the 
membrane  is  the  supra- 
tympanic  space,  the  attic, 
or  the  epitympanum. 
This  is  separated  from 
the  cranial  cavity  by  a 
very  thin  plate,  which 
is  sometimes  imperfect.  In  front,  the  cavity  of  the  tympanum  narrows  to  the  Eusta- 
chian tube.  It  opens  behind  through  the  antrum,  which  serves  as  a  vestibule,  into 
the  mastoid  cells.  The  antrum  is  a  cavity  of  irregular  size  and  shape,  compressed 
somewhat  from  side  to  side,  with  an  antero-posterior  diameter  of  from  ten  to  fifteen 
millimetres,  situated  behind  the  epitympanum  in  the  backward  projection  of  the 
squamosal,  which  forms  the  superficial  part  of  what  appears  to  be  the  mastoid,  and 
contains  some  of  the  so-called  mastoid  cells.  The  communication  with  the  tympanum 
is  a  narrow  one,  and  a  certain  number  of  cells  open  into  the  latter  independently. 

The  antrum  and  the  cells  nearest  it  are  lined  with  mucous  membrane  continued 
from  the  middle  ear.      The  inside  of  the  mastoid  varies  greatly.      Sometimes  it  con- 

1  The  detailed  description  of  this  space  is  given  in  connection  with  the  ear. 


Sagittal  section  through  right  temporal  bone,  seen  from  outer 


184  HUMAN    ANATOMY. 

tains  large  pneumatic  cavities,  sometimes  diploe  instead  of  air-cells,  and,  again,  it 
may  be  almost  solid  ;  the  latter  condition  is,  however,  probably  always  pathological. 
According  to  Zuckerkandl's '  investigations  of  250  temporal  bones,  the  mastoid  is 
entirely  pneumatic  in  36.  S  per  cent,  and  wholly  diploetic  in  20  per  cent.  The  re- 
maining 43.2  per  cent,  were  mixed,  the  diploe  being  at  the  point  of  the  mastoid  and 
the  cells  above.  Neither  size  nor  shape  indicates  its  internal  structure.  The  relation 
of  the  cells  to  the  lateral  sinus  has  been  already  mentioned. 

The  Facial  Canal. — The  course  of  the  canal2  for  the  facial  nerve  is  important. 
It  runs  outward  from  the  superior  fossa  of  the  internal  auditory  meatus  for  some 
three  millimetres,  until  joined  by  the  canal  from  the  hiatus  Fallopii.  It  then  makes 
a  sharp  turn  (the  genu)  backward,  passing  internal  to  the  attic  of  the  tvmpanum  just 
below  the  external  semicircular  canal,  which  almost  always  projects  a  little  farther 
outward.  It  then  curves  backward  to  descend  to  the  stylo-mastoid  foramen,  passing 
just  above  the  fenestra  ovalis.  The  descending  portion  is  rarely  strictly  vertical. 
Below  the  genu  the  facial  canal  may  make  a  bend  either  outward  or  inward,  but  its- 
general  line  of  descent  usually  inclines  outward,  sometimes  very  strongly.  Rarely 
the  descent  is  tortuous.  The  lower  part  may  incline  forward.  The  genu  is  opposite 
a  point  on  the  surface  above  the  external  meatus,  and  the  subsequent  course  of  the 
canal  can  be  indicated  in  general  by  a  line  following  the  posterior  border  of  the 
auditory  opening.  An  instrument  introduced  straight  into  the  front  of  the  mastoid 
will  pass  behind  the  facial  canal.3  The  diameter  of  the  latter  is  about  one  and  one- 
half  millimetres.  Just  before  its  lower  end  a  very  minute  canal,  transmitting  the 
chorda  tympani  nerve,  runs  upward  and  forward  from  it  to  the  cavity  of  the  tympa- 
num. From  the  front  of  the  cavity  this  nerve  escapes  by  the  minute  canal  of  Huguier, 
which  opens  near  the  inner  end  of  the  fissure  of  Glaser,  passing  between  the  tym- 
panic plate  and  the  tegmen  tympani.  The  facial  canal  has  several  other  minute 
openings.  There  are  also  minute  canals  for  Jacobsori  s  nerve  from  the  glosso- 
pharyngeal, leading  to  the  tympanum,  and  for  Arnold' s  branch  of  the  vagus,  which 
enters  the  jugular  fossa  and  leaves  by  the  fissure  between  the  mastoid  and  tympanic 
portions. 

The  carotid  canal '  is  close  to  the  front  of  the  tympanum  and  just  before  the 
cochlea  of  the  internal  ear.  The  internal  auditory  meatus  is  almost  behind  the  canal, 
and  the  Eustachian  tube  lies  to  the  outer  side  of  its  horizontal  portion. 

The  temporal  bone  is  porous  in  structure,  except  about  the  internal  ear,  where 
it  is  very  dense.  A  transverse  section,  either  vertical  or  horizontal,  through  the 
external  and  internal  meatus  (the  middle  and  internal  ears)  shows  how  nearly  the 
entire  bone  is  pierced  (Fig.  202).  The  carotid  canal  and  the  jugular  fossa,  when 
deep,  are  further  sources  of  weakness.  The  fossa  sometimes  opens  into  the  middle 
ear  by  a  small  rent. 

Articulations. — The  temporal  bone  joins  the  occipital  by  the  petro-mastoid 
portion.  These  two  bones  form  the  entire  posterior  fossa  of  the  skull,  except  at  the 
extreme  front,  in  the  middle,  where  it  extends  along  the  back  of  the  sphenoid, 
and  at  the  side,  where  a  small  portion  of  the  lateral  sinus  is  made  by  the  posterior 
inferior  angle  of  the  parietal.  This  latter  bone  articulates  with  the  squamous  and 
the  top  of  the  mastoid.  The  great  wing  of  the  sphenoid  fits  into  the  angle  between 
the  squamous  and  petrous  portions,  articulating  at  the  side  of  the  skull  with  the  front 
of  the  foramen.  These  two  bones — the  sphenoid  and  the  temporal — form  the  entire 
middle  fossa.  The  malar  bone  joins  the  zygoma,  completing  the  arch.  The  lower 
jaw  articulates  with  the  glenoid  fossa  by  a  true  joint. 

Development. — The  squamous  portion  is  ossified  in  membrane  from  one 
centre,  appearing  near  the  end  of  the  second  month  of  foetal  life.  In  the  course  of 
the  third  month  a  centre  appears  in  the  lower  part  of  the  future  tympanic  ring. 
The  ossification  of  the  petro-mastoid  portioti  comes  from  several  nuclei,  the  number 
of  which  probably  varies.  The  process  begins  towards  the  end  of  the  fifth  month 
about  the  membranous  labyrinth.  The  opisthotic  nucleus  lies  at  the  inner  side  of 
the  tympanic  cavity  and  spreads  to  the  lower  part  of  the  bone.  The  prob tic  is  near 
the    superior   semicircular    canal.      The    epiotic,    arising   near    the    posterior   canal, 

1  Monatsschrift  fur  Ohrenheilkunde,  Bd.  xiii,  1879. 

3  Joyce  :  Journal  of  Anatomy  and  Physiology,  vol.  xxxiv.,  1900. 

2  Canalis  facialis.     4  Canalls  i 


DEVELOPMENT  OF  THE  TEMPORAL  BONE. 


f 


\ 


Tympanic  ring    Malleus 


Temporal  bo 


Tegmen  tympani  i 
Glaserian  fissur 
of  tympanum 

at  about  birth,  outer  aspect. 


Petro-squamous  suture 


spreads  into  the  mastoid  portion.      This  one  is  sometimes  double.      There  is  also  a 

separate  nucleus  for  the  tegmen,  but  this  is  not  constant.      When  present,  it  seems 

to  be  the  last  to  fuse  with  the  others, 

which  become  one  by  the  end  of  the  Fig.  205. 

sixth  month.    The  carotid  artery  passes  Squamous  portion 

at  first  along  the  base  of  the  skull  in  a 

groove  which  is  made  into  a  canal  by 

the  opisthotic.     The  separated  petrous 

portion,    when   ossification    has    made 

some  progress,   shows  a  very  promi- 
nent superior  semicircular  canal,  and  a 

deep  cavity  under  it,  extending  back- 
ward from  the  inner  surface.      This  is 

the  floccular  fossa,  which,  however,  is 

completely  hidden  by  the  dura.      The 

mastoid  process  becomes  fairly  distinct 

in  the  course  of  the  second  year.      It 

develops    greatly   about    the    time    of 

puberty,  when  it  becomes  pneumatic. 

This  may  occur  much  earlier.      J.   J. 

Clarke  has  seen  it  wholly  pneumatic  several  times  before  the  tenth  year  ;  once  at 

three  and  a  half.1     The  squamosal  joins  the  petrous  in  the  course  of  the  first  year. 

At  birth  the  tympanic  por- 
Fig.  206.  tion  consists  solely  of  the  im- 

perfect ring  open  above.  This 
enlarges  trumpet-like  from  the 
edges,  the  front  one  forming 
the  tympanic  plate.  The 
growth  is  of  unequal  rapidity, 
so  that  the  lower  part  is  left 
behind,  presenting  a  deep 
notch  the  outer  edges  of 
which  meet  by  the  end  of  the 
second  year,  leaving  a  foramen 
below,  which  usually  closes 
two  or  three  years  later,  but 
exceptionally  persists.  The 
tympanic  plate  fuses  almost  at 
once  with  the  petrous,  but  the 

Glaserian  fissure  remains  ;  the  groove  showing  the  line  of  union  of  the  tympanic  and 

mastoid  processes  generally  disappears  in  the  second  year,  but  occasionally  persists 

through  life.    Kircher2  found  it  present  on 

both  sides  in  five  per  cent,  of  300  skulls. 

The  styloid  process  consists  of  two  parts. 

The  first  joins  the  petrous  at  about  birth. 

The  second,  which  represents  all  but  the 

base,  is  an  ossification  of  the  stylo-hyoid 

ligament,  and  does  not  join  till  puberty 

or  later.       In   very  earlv  fcetal   life   the 

chief  vein  returning  the  blood  from  the 

brain  passes  through  the  membrane  that 

is  to  become  the  squamosal.     This  open- 
ing— the   foramen  jugulare   spurium — ■ 

is  later  of  less  importance,  and  is  finally 

closed.     In  the  skull,  at  birth,  a  pin-hole 

representing  it  may  be  found  at  the  postglenoid  tubercle. 

later. 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxvii. 

2  Archiv  fiir  Ohrenheilkunde,  Bd.  xiv.,  1879. 


Carotid  canal 


Temporal  bone  at  about  birth,  f: 


Posterior  semicir- 
cular canal 
Floccular  fossa 


Internal  auditory  canal 
ibove  and  within. 


Fig.  207. 

Malleus 

External  -= 
auditory     * 
meatus     JS 

Tympanic  ring 
Tympanic  portion  of  temporal  bone  in  the  second  yt 


It  is  sometimes  seen 


1893. 


i86 


HUMAN  ANATOMY. 


THE  SPHENOID  BONE. 
In  the  adult  this  bone '  consists  of  a  cubical  body,  from  the  sides  of  which  arise 
the  great  wi?igs,  from  its  front  the  lesser  wings,  and  from  below  the  pterygoid  pro- 
cesses. Both  development  and  comparative  anatomy  show  that  these  parts  represent 
several  bones.  The  body  consists  of  two  parts,  a  posterior  and  an  anterior.  The 
posterior,  the  basisphenoid,  is  the  centre  of  the  middle  fossa  of  the  base  of  the  skull  ; 
from  its  sides  spread  the  great  wings,  or  alisphenoids.  These  with  the  temporal 
bones  complete  the  middle  fossa.  The  anterior  part,  the  presphenoid,  inseparably 
connected  with  the  basisphenoid,  is  in  both  the  middle  and  the  anterior  fossae.  The 
lesser  wings,  the  orbito-sphenoids ,  spread  out  from  the  presphenoid  and  cover  the 
apices  of  the  orbits.  The  pterygoid  processes  consist  each  of  two  plates,  the  inner  of 
which  represents  a  separate  bone  of  the  face,  the  outer  being  an  expansion  from  the 
alisphenoid.  Two  bones  called  the  cornua  sphenoidalia,  or  sphenoidal  turbinates,  of 
independent  origin,  ultimately  form  a  part  of  the  body  of  the  sphenoid. 


Fig.  208. 

Sphenoidal  turbinate 


Hamular  process 


Pterygoid  notch 


Internal  pterygoid  plate 
The  sphenoid  bone  from  before. 


The  Body. — It  is  necessary  to  describe  the  basisphenoid  and  the  presphenoid 
together,  since  they  form  the  roughly  cubical  body.  The  superior  surface  con- 
tains the  deep  pituitary  fossa,2  or  sella  turcica,  in  which  hangs  the  pituitary  body 
from  the  brain.  Behind  it  is  the  dorsum  sellce,  a  raised  plate  continuous  with  the 
surface  of  the  basilar  process  of  the  occipital  and  which  completes  the  posterior  fossa. 
Its  outer  angles  are  knobs  pointing  both  forward  and  backward,  the  posterior  cli?wid 
processes,  to  which  the  tentorium  is  fastened.  Beneath  these,  on  either  side  of  the 
dorsum,  is  a  groove  for  the  sixth  nerve.  In  front  of  the  sella  is  the  olivary  eminence3 
(of  the  presphenoid),  which  is  usually  an  oval  swelling,  though  it  may  be  plane  or 
concave.  At  its  sides  grooves,  often  very  poorly  marked,  lead  to  the  optic  foramina. 
The  posterior  edge  of  this  eminence  is  sometimes  grooved  for  a  vein  and  sometimes 
sharp.  Its  lateral  ends  may  become  tubercles,  the  middle  clinoid  processes.  The 
olivary  eminence  is  in  most  cases  bounded  in  front  by  a  transverse  elevation  con- 
necting the  lesser  wings,  of  which,  indeed,  it  is  a  part,  forming,  when  present,  the 
separation  of  the  anterior  and  middle  fossae.  The  front  border  presents  in  the 
median  line  a  triangular  point,  the  ethmoidal  spine. 

At  each  lateral  surface  of  the  body  is  the  carotid  groove •*  for  the  internal 
carotid  artery.     It  is  well  marked  only  at  the  posterior  edge,  where  the  artery  enters 

1  Os  sphenoidale.     2  Fossa  uypophyseos.     3Tuberculum  sellae.     4  Sulcus  caroticus. 


THE   SPHENOID    BONE. 


187 


it  from  the  apex  of  the  petrosal.  It  is  here  bounded  internally  by  a  little  tubercle, 
the  petrosal  process,  at  the  base  of  the  dorsum,  and  externally  by  a  very  delicate 
plate,  the  lingula,  which  sometimes  projects  considerably  ;  these  two  processes 
touch  either  side  of  the  end  of  the  carotid  canal  in  the  petrous.  The  rest  of  the 
side  of  the  body  is  hollowed  for  the  cavernous  sinus,  in  which  the  carotid  artery  runs. 
It  is  covered  below  by  the  origin  of  the  great  wing.  The  posterior  surface  of  the 
body  is  rough  up  to  puberty  for  the  cartilage  that  binds  it  to  the  basilar  process  of 
the  occipital  ;  later  these  parts  coossify,  and  thereafter  the  posterior  surface  is  made 
artificially  by  the  saw.  The  anterior  surface  presents  in  the  middle  a  sharp  ridge, 
the  sphenoidal  crest, v  to  join  the  vertical  plate  of  the  ethmoid.  Just  at  the  sides  of  this 
the  bone  is  smooth  and  aids  in  forming  the  wall  of  the  nasal  fossa.  In  each  lateral 
half  is  an  opening,  the  sphenoidal  foramen,'1  into  the  cavity  of  the  bone.  The 
inferior  surface  presents  in  the  middle  a  longitudinal  swelling,  thick  behind, 
narrow  and  sharp  in  front,  the  rostrum,  fitting  into  the  vomer  and  usually  joining 
the  lower  edge  of  the  crest  without  interruption.  It  may  stop  short  of  it.  On  either 
side  of  the  rostrum  there  is  a  smooth  triangular  surface  made  of  delicate  plate,  which 
extends  up  onto  the  front,  forming  the  smooth  surface  beside  the  crest,  and  bound- 

Fig.  209. 

Posterior  clinoid  process  Optic  foramen 


Foramen  rotundum 


Carotid  groov 
Scaphoid  fossa 

Pterygoid  fossa 


External  pterygoid  plate 


The  sphenoid  bone  f 


ing  a  large  part  of  the  hole  into  the  antrum.  These  are  the  bones  of  Berti7i,  or 
sphenoidal  spongy  bones,  of  which  more  is  to  be  said  under  Development  (page  191). 

The  body  of  the  sphenoid  is  hollow,  enclosing  two  cavities,  the  sphenoidal 
sinuses,  separated  by  a  septum,  which  runs  obliquely  backward  from  the  crest,  so 
that  one  sinus  is  usually  much  larger  than  the  other.  These  sinuses  have  irregular 
ridges  partially  subdividing  them.  They  are  lined  by  mucous  membrane  and  open 
into  the  nasal  cavity  by  the  sphenoidal  foramina.  The  opening  is  reduced  when  the 
ethmoid  is  in  place. 

The  great  wings  3  have  each  a  cerebral  or  superior  surface  forming  a  large  part 
of  the  middle  fossa,  an  external  surface  looking  outward  into  the  temporal  and 
downward  into  the  zygomatic  fossa,  and  an  orbital  surface  forming  most  of  the  outer 
wall  of  that  cavity.  The  superior  surface  is  smooth  and  concave  ;  springing  from 
the  side  of  the  basisphenoid,  it  spreads  upward  and  outward  and  also  backward  to 
fill  the  gap  between  the  petrous  and  squamosal  parts  of  the  temporal.  By  the  side 
of  the  body  there  is  a  short  canal  running  forward  to  open  on  the  front  of  the  bone 
into  the  spheno-maxillary  fossa  ;  this  is  the  foramen  rotundum  for  the  superior  max- 
illary division  of  the  fifth  nerve.      A  little  further  back  and  more  internal  is  a  pin- 

1  Crista  sphenoidalis.     2Apertura  sinus  sphenoldalia.     3Alae  magnae. 


iSS  HUMAN    ANATOMY. 

hole,  the  foramen  of  Vesalius,  for  a  minute  vein.  Farther  back  and  outward  near 
the  angle  is  the  foramen  ovale,  transmitting  the  mandibular  division  of  the  fifth 
cranial  nerve  to  the  base  of  the  skull,  and  admitting  the  small  meningeal  branch 
of  the  internal  maxillary  artery.  Just  beyond  this,  in  the  extreme  angle,  so  as  some- 
times to  be  completed  by  the  temporal,  is  the  foramen  spinosum,  admitting  the 
middle  meningeal  artery  to  supply  the  bone  and  the  dura.  The  external  surface 
is  divided  into  a  larger,  superior,  vertical  part,  looking  towards  the  temporal  fossa, 
and  one  looking  into  the  zygomatic  fossa.  These  are  separated  by  the  infratem- 
poral crest,  which  near  the  front  points  downward  as  a  strong  prominence,  the  infra- 
temporal spine.  The  inferior  surface  contains  the  foramen  ovale  and  the  foramen 
spinosum.  Just  behind  the  latter,  at  the  posterior  angle,  is  the  spine  of  the  sphenoid, 
pointing  downward,  grooved  at  the  inner  side  by  the  chorda  tympani  nerve.  The 
external  surface  has  an  anterior  border  where  it  meets  the  orbital  surface,  which 
joins  the  malar.  The  superior  border  slants  upward,  overlapping  the  frontal  and 
parietal  bones.  The  posterior  border  is  about  vertical  as  far  down  as  the  infra- 
temporal crest,  and  bevelled,  especially  above,  to  be  overlapped  by  the  squamous 
part  of  the  temporal.  The  lower  part  of  this  border  runs  backward  and  somewhat 
overlaps  the  squamosal.     The  posterior  border  of  this  surface,  from  the  spine  to  the 


Articulates  with  frontal 


Fig.  210. 

Ethmoidal  crest 

Olivary 

Optic  forame 


Foramen  rotun- 


Foramen  ovale 
Foramen  spinosum 


Dorsum  sellae 
The  sphenoid  bone  from  above 


body,  is  slightly  rough  for  the  petrous,  making  with  it  a  groove  on  the  under  side 
for  the  cartilaginous  Eustachian  tube.  The  smooth  orbital  surface,  facing  inward 
and  forward,  is  quadrilateral,  broader  in  front  than  behind.  Almost  the  whole  of  it  is 
in  the  outer  wall  of  the  orbit,  of  which  it  forms  the  greater  part  ;  but  a  small  portion, 
narrow  behind  and  expanding  in  front,  looks  into  the  spheno-maxillary  fissure,  which- 
bounds  this  surface  below.  It  joins  the  malar  in  front.  On  the  top  of  the  bone 
there  is  a  rough  triangular  region  in  the  angle  formed  by  the  meeting  of  the  external 
and  orbital  surfaces,  on  which  the  frontal  bone  rests.  This  is  above  the  front  half 
of  the  orbital  plate.  The  remainder  of  the  upper  and  the  whole  of  the  posterior 
border  of  the  latter  bound  the  sphenoidal fissure.*  This  cleft  is  an  elongated  aper- 
ture, directed  obliquely  outward  and  upward  between  the  great  and  lesser  wings  of 
the  sphenoid,  completed  externally  by  the  frontal.  It  opens  anteriorly  into  the 
orbit  and  transmits  the  third,  the  fourth,  the  ophthalmic  division  of  the  fifth  and 
sixth  cranial  nerves,  and  the  ophthalmic  veins.  There  is  a  small  projection  near  the 
middle  of  the  hind  border  for  a  ligament  crossing  the  fissure  and  for  the  outer  head 
of  the  external  rectus. 

The  lesser  wings,2  forming  the  back  part  of  the  anterior  fossa  and  of  the  roof 
of  the  orbit,  arise  by  two  roots.  The  superior  is  a  plate  covering  the  presphenoid  ; 
the  inferior  is  a  strong  process  from  the  side  of  the  body.      With  the  latter  they 


1  Fissura  orbitalis  superior.     -  Alae  parvae. 


THE  SPHENOID  BONE. 


enclose  a  canal,  commonly  called  the  optic  for -amen,1  for  the  optic  nerve,  which  is 
accompanied  by  the  ophthalmic  artery.  The  length  of  the  canal  measured  along 
the  inferior  root  is  about  five  millimetres.  The  length  of  the  roof  is  greater,  per- 
haps nearly  twice  as  much,  but  it  is  variable  from  the  uncertain  development  of 
that  part  of  the  bone  ;  definite  dimensions  are,  therefore,  wanting.  The  vertical 
diameter,  some  five  millimetres,  of  the  opening  into  the  orbit  is  a  little  greater  than 
the  transverse.  The  small  wing  over- 
hangs the  front  of  the  middle  fossa  pIG.  2n. 
bounding  the  sphenoidal  fissure  above, 
and  ends  laterally  in  a  sharp  point.  The 
anterior  ciinoid process  is  a  sharp  pro- 
jection backward  above  the  inferior 
root  and  towards  the  posterior  ciinoid. 
Sometimes  it  reaches  the  latter  ;  some- 
times it  is  connected  by  a  spur  with  the 
middle  ciinoid  process,  then  bridging  the 
carotid  groove  and  making  a  ca?'otico- 
clinoid  foramen  (Fig.  211).  The  an- 
terior border  of  the  lesser  wings  is 
rough  at  its  inner  part  and  smooth  at 
the  outer,  where  it  joins  the  posterior 
edge  of  the  horizontal  plate  of  the  frontal.  The  posterior  border  is  smooth,  form- 
ing most  of  the  boundary  of  the  anterior  and  middle  cranial  fossae. 

The  pterygoid  processes2  are  downward  projections  which,  articulating  with 
the  palate  bone,  form  the  back  of  the  framework  of  the  upper  jaw.  Each  consists  of 
two  plates,  an  inner  and  an  outer,  united  in  front,  diverging  behind  to  form  the 
pterygoid  fossa,  and  separating  below  on  either  side  of  the  pterygoid  notch.  The 
inner  springs  from  the  body,  the  outer  from  the  great  wing.  The  inner  pterygoid 
plate3  is  the  longer.  It  is  nearly  vertical,  ending  in  the  slender  hamular  process^ 
which  points  outward,  bounding  a  deep  little  notch  through  which  the  tendon  of  the 
tensor  palati  plays.      At  the  inner  side  of  its  origin  the  internal  plate  presents  a 

scale-like  curved  projection,  the  vaginal 


)id  bone,  showing  abnormal  development  of 
aoid  processes,  especially  on  the  left  side.  Re- 
half. 


Fig.  212. 


Sphenomaxillary  fossa 


process,  above  which  is  an  anteroposte- 
rior groove  below  the  body  of  the  sphe- 
noid, in  which  the  lateral  expansion  of 
the  base  of  the  vomer  is  received.  Just 
external  to  the  vaginal  process  is  an- 
other small  groove,  the  pterygo-palathie, 
which  the  palate  bone  converts  into  a 
canal  leading  back  from  the  spheno- 
maxillary fossa.  The  outer  pterygoid 
plate5  is  broader  and  flares  outward. 
The  anterior  surface  of  the  root  is  nearly 
smooth,  forming  the  back  wall  of  the 
spheno-maxillary  fossa.  It  has  the 
openings  of  two  canals  :  the  upper  and 
outer  is  that  of  the  foramen  rotundum  ; 
the  lower  and  inner,  which  is  smaller,  is 
the  Vidian  canal,  transmitting  the  nerve 
and  vessels  of  that  name.  There  is  a  vertical  ridge  between  the  two,  and  a  slight 
groove  below  the  latter,  forming  with  the  palate  bone  the  beginning  of  the  poste- 
rior palatine  canal  which  runs  from  the  spheno-maxillary  fossa  through  the  hard 
palate,  transmitting  a  descending  palatine  nerve  and  vessels.  The  lower  anterior 
edges  of  both  plates  are  rough  to  articulate  with  that  bone.  The  outer  surface  of 
the  external  plate  is  irregular  for  the  origin  of  the  external  pterygoid  muscle.  The 
inner  wall  of  the  inner  plate  is  smooth.  It  bounds  laterally  the  back  of  the  nasal 
cavity.  The  posterior  borders  of  both  plates  are  sharp,  excepting  that  the  inner  is 
formed  by  the  union  of  two  lines  which  enclose  the  scaphoid  fossa  where  the  tensor 
palati  arises.      Rather  less  than  half  way  down  the  internal  plate  presents  a  promi- 

1  Foramen  opticum.    -  Processus  pterygoidei.     J  Lamina  mcdialis  proc.  pteryg.     *  Hamulus  pterygoidei.    ''  Lamina  laterally 
proc.  pteryg. 


Portion  of  sphenoid  bone,  showing  the  foramen  pterygo- 
spinosum. 


190 


HUMAN    ANATOMY. 


Presphenoid   |        Ext.  pterygoid  plate 
Int.  pterygoid  plate 


Sphenoid  bone  at  about  birth,  £ 


nence  bounding  a  groove  below,  which  supports  the  Eustachian  tube.  The  posterior 
border  of  the  outer  plate  is  irregularly  scalloped.  Near  the  top  a  transverse  ridge 
crosses  its  inner  surface  ;  if  well  marked,  this  forms  the  top  of  the  pterygoid  fossa. 
It  may  be  barely  discernible  (Waldeyer1).  Just  above  the  scaphoid  fossa  is  the 
hind  end  of  the  Vidian  canal  opening  into  the  middle  lacerated  foramen  opposite  the 
apex  of  the  petrous.  The  development  of  the  pterygoid  plates  varies  greatly.  The 
upper  part  of  the  outer  may  be  prolonged  to  the  spine  of  the  sphenoid,  just  outside 
of  the  foramen  ovale,  with  a  perforation  at  this  point,  so  that  some  of  the  branches 
of  the  third  division  of  the  fifth  cranial  nerve  may  pass  on  either  side  of  it.  This 
occurs  by  the  ossification  of  a  band  of  fibrous  tissue,  connecting  the  back  of  the 

plate  with  the  spine,   and  thus 
Fig.  213.  forming  the  foramen  pterygo- 

Sphenoidai  spinosuni  of  Civinini  (Fig.  212). 

This  is  always  behind  the  fora- 
men ovale,  or  internal  to  it. 
Just  outside  of  the  foramen  is 
found,  very  rarely,  a  little  canal 
on  the  under  side  of  the  great 
wing,  transmitting  a  branch  of 
the  mandibular  division  of  the 
fifth  nerve,  the  porus  crotaphit- 
ico-buccinatorius  of  Hyrtl. 

Articulations. — Much 
has  been  already  said  incident- 
ally on  this  point  in  the  fore- 
going description.  The  sphenoid  bone  joins  the  occipital  behind.  The  great  wings 
send  the  spine  into  the  entering  angle  between  the  squamous  and  petrous  portions 
of  the  temporal.  These  two  bones — the  sphenoid  and  the  temporal — form  the 
entire  middle  fossa  of  the  skull.  The  middle  lacerated  foramen  is  just  behind  the 
carotid  groove  at  the  side  of  the  body  and  in  front  of  the  end  of  the  petrous.  At 
the  side  of  the  skull  the  great  wings  join  the  squamous  behind,  the  parietal  and  the 
frontal  above,  and  the  malar  in  front.  The  ethmoid  covers  the  front  of  the  body  of 
the  sphenoid,  its  vertical  plate  joining  the  crest.  The  vomer  covers  the  rostrum 
below.  The  palate  bone  fills 
up  the  pterygoid  notch,  com- 
pleting the  fossa,  and  by  its 
sphenoidal  process  touches 
the  edge  of  the  body.  The 
frontal  bone  joins  the  lesser 
wings. 

Developmen  t . — The 
presphenoid  and  basisphenoid 
each  ossify  from  a  pair  of 
nuclei,  those  of  the  former 
appearing  at  the  end  of  the 
second  month  of  fcetal  life  and 
the  latter  a  little  later.  At 
about  the  eighth  week  a  nu- 
cleus is  to  be  seen  in  each  of 

the  greater  wings  near  the  body  and  extends  outward,  involving  also  the  external 
pterygoid  plate.  The  internal  pterygoid  plate  has  a  nucleus  of  its  own,  which 
is  present  in  the  fourth  month  and  joins  the  outer  a  month  later.  Two  little  gran- 
ules appear  in  the  fourth  month  for  the  lingula  and  a  neighboring  piece  of  the 
bone.  The  orbito- sphenoids  have  each  two  centres,— one  on  either  side  of  the  optic 
foramen.  It  would  seem  that  the  inner  may  in  some  cases  take  the  place  of  those  for 
the  presphenoid.  In  any  case  the  presphenoid  and  the  lesser  wings  unite  before  birth. 
In  the  seventh  or  eighth  month  the  presphenoid  and  basisphenoid  unite,  but  at  birth 
they  are  still  separated  by  cartilage  on  their  lower  surface.  At  birth  the  bone  con- 
1  Sitzungsber.  Acad.  Wissen.,  Berlin,  1893. 


Fig.  214. 

Presphenoid 


sphenoidale 

11  wing  (orbito-sphenoid) 
Foramen  rotundum 
Great  wing 
(alisphenoid) 


Basisphenoid      Lingula     Foramen  ova 
Sphenoid  bone  at  about  birth,  seen  from  behii 


THE   ETHMOID   BONE. 


191 


sists  of  the  basisphenoid,  the  presphenoid,  and  the  lesser  wings  in  one  piece,  and  a 
lateral  one  on  each  side, — namely,  the  greater  wing  and  the  pterygoids.  The  dorsum 
sella?  has  a  separate  epiphysis  which  appears  after  birth.  In  the  first  year  the  lesser 
wings  spread  across  the  top  of  the  presphenoid,  joining  the  jugum  sphenoidale,  so 
that  it  does  not  show  in  the  anterior  fossa.  The  external  pterygoid  plate  is  an  out- 
growth of  the  great  wing. 

The  cornua  sp/ienoidalia,  bones  of  Berlin,  or  sphenoidal  turbinate  bones,  are  two 
thin  plates  which  appear  before  birth  at  the  front  of  the  presphenoid.  They  cover 
both  the  front  and  its  inferior  surface  at  the  sides  of  the  rostrum.  At  five  years  they 
are  still  free,  but  have  approached  their  permanent  shape  of  hollow  cones.  The 
hollowing  out  of  the  body  of  the  sphenoid  now  begins,  and  at  the  same  time  the 
upper  part  of  these  bones  is  absorbed,  so  that  the  foramina  become  notches.  These 
bones  are  ultimately  joined  to  the  sphenoid,  the  ethmoid,  and  the  palate.  Though 
usually  reckoned  as  parts  of  the  sphenoid,  there  is  reason  to  believe  that  they 
are  generally  fused  earlier  with  the  ethmoid.  The  basisphenoid  begins  to  coossify 
with  the  occipital  at  about  the  fifteenth  year.     The  process  is  first  completed  above. 

THE    ETHMOID    BONE. 

The  ethmoid '  consists  of  a  median  plate  forming  a  part  of  the  nasal  septum,  of 
the  cribiform  plate  joining  it  at  the  top  on  either  side  and  forming  the  roof  of  the 
nasal  cavity,  and  of  two  lateral  masses  attached  to  the  lateral  border  of  each  cribriform 
plate,  and  touching  the  vertical  plate  very  slightly  just  below  its  junction  with  the 
front  of  the  cribriform  plate.  These  lateral  masses  are  roughly  cubical,  interposed 
between  the  cavities  of  the  nose 

and  of  the  orbit.     They  consist  of  Fig.  215. 

a  series  of  delicate  plates  forming 
the  walls  of  air-spaces  or  cells, 
which  are  mostly  completed  by 
neighboring  bones. 

The  vertical  or  median 
plate  2  projects  near  the  front  into 
the  cranial  cavity  as  the  crista 
galli,  thicker  in  front  than  behind, 
with  an  oblique  upper  border  run- 
ning sinuously  downward  and 
backward.  Its  greatest  elevation 
is  about  one  centimetre.  The 
front  part  is  occasionally  hollow, 
forming  a  part  of  the  frontal  sinus. 
It  gives  attachment  to  the  falx 
cerebri,  a  fold  of  dura  separating 
the  hemispheres  of  the  brain.  A 
little  plate,  ala,"  facing  downward 

and  forward,  arises  from  the  front  on  either  side,  articulating  with  the  frontal.  Just 
before  the  crista  galli  is  a  pin-hole,  the  foramen  c<zcum,  usually  formed  by  both 
ethmoid  and  frontal,  but  which  may  be  in  either.  It  is  said  to  transmit  a  vein  in 
early  life,  but  is  closed  later.  The  part  of  the  vertical  plate  below  the  horizontal  one 
is  five-sided.  The  upper  border  runs  along  the  base  of  the  skull  ;  one  in  front  of 
it  slants  downward  and  forward  under  the  nasal  spine  of  the  frontal,  sometimes 
reaching  the  nasal  bones  ;  another  descends  nearly  vertically  along  the  crest  of  the 
sphenoid.  Of  the  two  inferior  borders,  the  posterior  runs  downward  and  forward 
along  the  greater  part  of  the  vomer,  while  the  anterior,  running  downward  and 
backward  to  meet  it,  is  free  in  the  skeleton,  but  in  life  is  attached  to  the  triangular 
cartilage  which  forms  a  large  part  of  the  septum.  The  sides,  covered  with  mucous 
membrane,  are  smooth  except  at  the  upper  part,  where  there  are  vertical  grooves 
for  the  olfactory  nerves.      This  plate  usually  slants  to  one  side. 

The  horizontal  or  cribriform  plate  '  forms  the  floor  of  a  narrow  groove  on 
either  side  of  the  crista  galli  and,  farther  back,  in  the  middle  of  the  anterior  fossa  of 


Mid.  turbinate 


Uncinate  process 
•id  bone,  outer  aspect  from  the  right  side 


Os  ethmoidals     -  Lamina  perpendicula 


PriR'L'ssiis  alaris. 


192 


HUMAN   ANATOMY. 


the  skull.  The  greatest  breadth  of  the  groove  is  about  five  millimetres.  It  nar- 
rows in  front  to  a  point,  and  thus  allows  the  lateral  masses  to  touch  the  median 
plate.  It  supports  the  olfactory  lobe  of  the  brain,  and  is  perforated  by  holes  for  the 
passage  of  the  olfactory  nerves.  These  are  arranged  rather  vaguely  in  three  rows. 
There  are  many  in  front  and  few  behind.  Many  of  the  larger  ones,  which  are  near 
the  septum  or  at  the  outer  side,  are  small  perforated  pits.  At  the  front  a  lo?igi- 
tudinal  fissure,  close  to  the  crista  galli,  transmits  the  nasal  branch  of  the  fifth  nerve. 
The  lateral  masses '  are  two  collections  of  bony  plates  imperfectly  bounding 
cavities.  They  are  roughly  six-sided,  the  greatest  diameter  being  antero-posterior. 
The  outer  surface  presents  a  vaguely  quadrilateral  plate,  the  os planum?  forming 
a  large  part  of  the  inner  wall  of  the  orbit.  In  its  upper  border  are  two  notches, 
which  become  the  anterior  and  posterior  ethmoidal  forami?ia  when  the  frontal  bone 
is  in  place.  The  former  transmits  the  nasal  branch  of  the  fifth  nerve  from  the  orbit 
to  the  cranial  cavity.  The  os  planum  is  bounded 
behind  by  the  body  of  the  sphenoid  ;  below  by  the 
palate  bone  and  superior  maxilla,  the  former  of  which 
usually,  and  the  latter  always,  complete  some  eth- 
moidal cells  which  appear  along  the  lower  border. 
There  is  a  large  mass  of  open  cells  in  front  of  the 
os  planum.  Those  nearest  to  it  are  completed  by 
the  lachrymal  and  the  more  anterior  ones  by  the 


'  perpendicular  plate  of  eth 


been  removed. 


nasal  process  of  the  superior  maxilla.  Posteriorly,  the  lateral  mass  rests  against  the 
body  of  the  sphenoid,  the  posterior  cells  being  separated  from  those  of  the  sphenoid 
by  the  cornua  sphenoidalia.  The  open  cells  on  the  upper  surface  of  the  lateral  mass 
are  closed  by  the  imperfect  cells  on  the  under  side  of  the  horizontal  plate  of  the 
frontal  beside  the  ethmoidal  notch.  The  few  cells  that  open  anteriorly  are  contin- 
uous with  the  lateral  ones,  and  are  closed  by  the  nasal  process  of  the  upper  jaw. 
The  numerous  spaces  within  the  ethmoid  are,  for  the  most  part,  completed  by  the 
neighboring  bones,  after  which  they  are  named.  There  are  some  beneath  the  os 
planum,  however,  entirely  within  the  ethmoid.  The  ethmoidal  cells%  are  divided  into 
anterior  and  posterior,  of  which  the  former  open  into  the  nose  below  the  middle 
turbinate  bone  and  the  latter  above  it.  The  size  and  shape  of  the  ethmodial  cells 
are  very   irregular  ;    sometimes   the  middle  turbinate  is  hollowed  into  one,  some- 


1  Labyrinthus  ethmoidals 


'Cellulae  ethmoidal 


THE    ETHMOID    BONE. 


193 


Fig.  217. 


Crista  galli 


Orbital 
plate 


i.i  hi  me  In  mi  abo 


times  they  swell  out  into  the  cavities  of  other  bones,  notably  into  the  frontal  sinus. 
The  internal  surface  of  the  lateral  mass,  forming  the  outer  wall  of  the  nasal 
cavity,  cannot  be  seen  on  the  entire  bone.  It  is  best  studied  on  the  bisected 
skull  ;  but  to  study  the  whole  bone,  further  cutting  is  necessary,  since  this  sur- 
face is  made  of  a  series  of  con- 
voluted plates,  some  of  which 
conceal  others.  At  least  two  of 
these — the  superior  and  the  mid- 
dle turbinate  bones ' — are  evident. 
They  are  curled  with  their  con- 
vexities towards  the  median 
plane,  so  as  to  overhang  two 
antero-posterior  passages,  the 
superior  and  the  middle  meatus 
of  the  nasal  fossa.  According 
to  Zuckerkandl,  there  are  three 
ethmoidal  turbinate  bones  in 
more  than  eighty  per  cent.,  and 
sometimes  four.  When  only 
two  are  seen,  it  is  owing  either 
to  the  absence  of  the  second 
or  to  its  slight  development,  so 
that  it  is  hidden  by  the  upper. 
It  is  certain  that  only  two  are 
evident  in  most  cases,  and  v/e 
shall  follow  the  usual  method  of 
so  describing  the  bone.2  The 
inferior  ethmoidal  (middle)  tur- 
binate is  much  the  larger,  very  prominent,  and  joins  the  ascending  process  of  the 
superior  maxilla  at  the  crista  ethmoidalis  or  superior  turbinate  crest.  Its  general 
course  is  backward  and  downward,  to  end  in  a  point  at  the  posterior  border  of  the 

bone.  The  free  edge  is  so  much 
curled  under  as  to  be  hidden. 
The  superior  turbinate  is  much 
smaller,  occupying  the  postero- 
superior  angle.  It  appears  to 
separate  from  the  turbinate  below 
it  at  about  the  middle  of  this  sur- 
face. The  superior  meatus,  which 
it  overhangs,  is  therefore  small. 
As  above  implied,  an  additional 
ethmoidal  turbinate  may  appear 
from  beneath  it,  and  still  another 
small  one  may  very  exceptionally 
be  found  above  it  at  the  extreme 
upper  posterior  angle.  At  the 
point  at  which  the  middle  turbi- 
nate bone  joins  the  nasal  process 
of  the  maxilla  there  is  often  a 
slight  elevation,  the  agger  ?iasi, 
which  is  supposed  to  be  the  an- 
terior end  of  another  turbinate  which  passes  under  the  preceding.  When  the  mid- 
dle turbinate  is  removed,  a  curved  projecting  plate,  the  uncinate  process*  is  seen 
on  the  lateral  mass,  curving  downward  and  backward.  It  is  some  two  or  three 
millimetres  broad  and,  extending  beneath  the  rest  of  the  bone,  joins  the  inferior 
turbinate.      The  uncinate  process,  together  with  the  agger,  is  held  to  represent  the 

2  There  are  practically  three  turbinate  bones,  the  upper  two  of  which  are  parts  of  the 
ethmoid  and  the  lowest  a  separate  bone.  These  are  called  superior,  middle,  and  inferior ; 
hence  we  speak  of  the  inferior  ethmoidal  turbinate  as  the  middle  one. 

1  Concha  nasalis  superior  ct  media.     3  Processus  uncinatus. 

13 


Fig.  218. 


Alar  process 
of  crista  galli 


Posterior  ethmoidal 


Sup.  meatus 


194 


HUMAN    ANATOMY. 


Probe  in  infundibulum 


Sup.  turbinate 


Uncinate  process 


The  ethmoid  bone,  inner  aspect  from  left  side,  part  of  the  i 
having  been  removed. 


,iddle  turbinate 


7iaso-turbinal  bone  of  many  mammals.  Behind  this  is  a  globular  swelling,  the  bulla,1 
formed  by  a  plate  springing  from  the  os  planum,  covering  cells,  which  also  is  held 
to  represent  a  turbinate.  Between  the  uncinate  process  and  the  bulla  is  a  deep 
groove,  the  infundibulum,'1  curving  downward  and  backward,  the  opening  into  which 
from  the  nasal  fossa  is  known  as  the  hiatus  semilunaris.      The  upper  end  of  the 

infundibulum  opens  into 
Fig.  219.  the  frontal  sinus  in  about 

half  the  cases,  3  ending 
blindly  in  the  others  ;  it 
is  bounded  externally  to 
a  varying  extent  by  the 
lachrymal.  A  number 
of  anterior  ethmoidal 
cells  generally  open  into 
this  portion.  The  lower 
end  of  the  infundibu- 
lum has  an  opening  on 
its  outer  side  into  the 
antrum. 

Articulations. — 
These  have  already  been 
described  incidentally. 
Briefly  recapitulated, 
however,  the  articula- 
tions of  the  ethmoid  are 
with  the  frontal,  the 
sphenoid,  the  palatals,  the  vomer,  the  inferior  turbinates,  the  lachrymals,  and  the 
nasals. 

Development. — The  ethmoid  is  very  small  at  first  and  backward  in  its 
development.  About  the  middle  of  foetal  life  ossification  appears  in  the  os  planum 
and  the  middle  turbinate  bone.  A  centre  (two,  according  to  Poirier)  for  the  vertical 
plate  occurs  in  the  first  year,  from  which  ossification  extends  into  the  crista  galli. 
The  cribriform  ossifies  chiefly  (perhaps  wholly)  from  the  lateral  masses.  The  date 
of  the  union  of  the  three  pieces  is  rather  uncertain  ;  it  takes  place,  probably,  at 
about  the  sixth,  year.  The  cells  appear  first  as  depressions  during  foetal  life. 
According  to  the  more  generally  accepted  view,  their  growth  is  by  absorption  of 
bone.  It  is  hard  to  believe  that  this  is  not,  at  least,  a  factor  ;  Poirier,  however, 
holds  that  they  are  due  to  the  course  of  ossification. 

THE    FRONTAL    BONE. 

This  bone,*  which  forms  the  front  of  the  vault  of  the  skull,  most  of  the  floor  of 
its  anterior  fossa,  and  bounds  the  greater  part  of  the  orbits  and  the  ethmoidal  cells 
above,  is  developed  into  two  symmetrical  halves  which  unite  in  the  second  year.  It 
is  convenient  to  divide  the  bone  thus  formed  into  a  vertical  and  a  horizontal  portion, 
although  this  division  rests  on  no  scientific  basis. 

The  vertical  portion,5  convex  anteriorly,  presents  on  either  side,  below  its 
middle,  the  frontal  eminence?  which  represents  the  chief  centre  of  ossification  f 
either  half.  Very  prominent  in  infancy,  it  diminishes  during  growth,  and  is  hardly 
to  be  made  out  in  most  adult  skulls.  The  lower  border  of  the  vertical  portion  grows 
downward  in  front  between  the  orbits.  At  the  sides  of  this  projection  are  the 
internal  angular  processes  of  the  orbits.  In  the  middle-line  a  faint  zigzag  line  marks 
the  remnant  of  the  i?iterfrontal  suture.  Above  this  is  a  smooth,  rather  prominent 
surface,  called  the  glabella,  external  to  which  are  the  superciliary  ridges?  or  emi- 
nences, which  extend  outward,  somewhat  above  the  inner  ends  of  the  orbits.  The 
development  of  these  varies  greatly.  On  either  side  of  the  nasal  projection  is  the 
orbital  arch,  extending  outward  from  the  internal  angular  process.  At  about  the 
3H.  A.  Lothrop  :  Annals  of  Surgery,  vol.  xxviii.,  1898. 


'Infundibulum     ethmoidule. 


5  Squama    frontalis.      6  Tuber    frontale 


THE    FRONTAL    BONE. 


195 


inner  third  of  the  arch  is  the  supraorbital  notch 1  for  the  nerve  and  the  artery  of  the 
same  name.  The  outer  edge  of  the  notch  is  more  prominent  than  the  inner.  Very 
often  this  is  replaced  by  a  foramen,  which  may  be  four  or  five  millimetres  above  the 
edge  of  the  bone.  The  arch  ends  externally  in  the  external  angular  process?  which 
joins  the  malar  and  is  very  prominent.  From  it  springs  the  temporal  crest?  which, 
curving  upward  and  backward,  separates  the  anterior  surface  of  the  bone  from 
the  lateral  one,  which  is  a  part  of  the  temporal  fossa.  This  crest  generally,  before 
leaving  the  bone,  divides  into  two  lines,  of  which  one  is  much  more  distinct  than  the 
other.  The  vertical  part  of  the  bone  has  a  slight  point  above  in  the  middle  and  a 
very  jagged  posterior  border  interlocking  with  the  parietal.  The  latter  is  slightly 
overlapped  above  and  overlaps  below.  The  bevelled,  though  jagged,  articular  sur- 
face broadens  below  to  meet  a  triangular  rough  space  on  the  inferior  surface.  At  the 
lower  lateral  edge  the  bone  is  covered  by  the  top  of  the  great  wing  of  the  sphenoid. 

Fig.  220. 


xternal  angular 
process 
/  ^ft^SSfy^  WWi^SfSlff'  1Ilt-  an£-  process  ~'*0yf/ 

Supra-orbital  foramen 

Corrugator  supercilii 

Orbicularis  palpebrarum 

Nasal  spine 
The  frontal  bone  from  before. 

The  horizontal  portjon  *  shows  in  the  middle  of  its  lower  aspect  a  rough  surface 
extending  onto  the  front,  called  the  nasal  process,  which  articulates  anteriorly  with 
the  nasal  bones  and  laterally  with  the  ascending  processes  of  the  upper  jaw*'  "In  the 
middle  projects  a  thin  plate,  the  nasal  spine,  behind  and  between  the  nasal  bones. 
On  either  side  of  this  there  is  often  found  a  small  smooth  surface  forming  a  small 
part  of  the  roof  of  the  nasal  cavity.  Behind  this  lies  the  median  ethmoidal  notch?  on 
either  side  of  which  is  an  irregular  space  reaching  to  the  inner  edge  of  the  orbit, 
made  of  imperfect  cells,  completing  the  ethmoidal  ones.  In  front  of  these  a  cavity 
extends  directly  up,  hollowing  out  the  bone  into  the  frontal  sinus,  which  may  extend 
outward  and  backward  over  the  orbits.  A  partition  separates  the  sinuses  of  the  two 
sides,  which  are  rarely  symmetrical.  The  sinus  opens  into  the  middle  meatus  either 
directly,  under  the  front  of  the  middle  turbinate,  or  through  the  infundibulum. 
When  the  ethmoid  is  in  place,  the  cribriform  plate  and  the  crista  galli  fill  up  the 
ethmoidal  notch  ;  the  ethmoidal  cells  are  then  closed,  and  the  ethmoidal  foramina 

1  Inclsura  supraorbitals.     -  Processus  zygoniaticus.     -1  Linea  temporalis.     4  Pars  orbitalis.     &  Incisura  ethmoidals. 


ig6 


HUMAN    ANATOMY. 


and  canals  are  formed.  External  to  this  lies  the  orbital  plate,  the  front  of  which  is 
overhung  by  the  supraorbital  arch.  It  is  slightly  concave  from  side  to  side,  just 
under  cover  of  the  external  angle  is  an  ill-marked  depression '  for  the  lachrymal  gland. 
Near  the  internal  angular  process  there  may  be  a  small  fossa  2  for  the  cartilaginous 
pulley  for  the  superior  oblique  muscle.  More  frequently  there  is  a  minute  tubercle. 
The  inner  border  of  the  orbital  surface  runs  nearly  straight  backward.  Its  sharp 
edge  articulates  from  before  backward  with  the  ascending  process  of  the  maxilla, 
the  lachrymal,  and  the  ethmoid.  The  outer  edge  runs  obliquely  inward.  External 
to  it,  behind  the  angular  process  which  joins  the  malar,  is  a  rough  triangular  surface 
articulating  with  the  great  wing  of  the  sphenoid.  The  posterior  border  of  the  orbital 
plate  is  short  and  serrated  to  join  the  small  wings  of  the  sphenoid. 

The  internal  surface  of  the  frontal  presents  the  frotital  crest  below  in  the 


Groove  for  longitudinal 


External  angular  process 


Supra-orbital  fora: 

Frontal  sin 


Nasal  spine 
Nasal  process 
The  frontal  bone  from  behind. 


median  line.  It  is  a  slight  ridge,  to  which  the  falx  is  attached.  A  narrow  gj-oove 
runs  along  it,  starting  at  the  foramen  ctzcum,  a  hole  either  in  this  bone  or  between 
it  and  the  ethmoid.  This  groove  is  for  the  superior  longitudinal  sinus.  After  a 
short  distance  the  crest  disappears,  but  the  groove  broadens  and  extends  to  the  top 
of  the  bone.  There  are  a  few  grooves  for  branches  of  the  middle  meningeal  artery 
at  the  side  and  some  small  Pacchionian  depressions.3  Below,  on  either  side  of  the 
notch,  are  the  orbital  plates,  which  slant  strongly  downward  and  inward,  so  as  to 
leave  the  ethmoid  in  a  deep  gutter.  Their  upper  surfaces  are  very  irregular  with 
so  called  digital  ivipressio7is  for  the  opposed  cerebral  convolutions.  It  is  now  evident 
how  the  frontal,  the  ethmoid,  and  the  lesser  wings  of  the  sphenoid  form  the  anterior 
fossa  of  the  skull. 

3  See  Parietal  Bone  (page  198). 


1  Fossa  glandulae  1 


lis.     -  Fovea  trochlear!* 


THE    PARIETAL    BONE. 


197 


Articulations. — The  frontal  articulates  with  the  nasal,  superior  maxillary, 
lachrymal,  malar,  ethmoid,  sphenoid,  and  parietal  bones. 

Development  and  Changes. — The  only  important  centres  are  the  two  sym- 
metrical ones  appearing  in  the  membrane  at  the  frontal  eminences  towards  the  end 
of  the  second  month  of  foetal  life.  There  is  a  separate  point  for  the  nasal  spine 
and  one  near  each  angular  process  of  the  orbit.  These  smaller  ones  are  fused  in  the 
seventh  month  of  foetal  life.  There  is  a  centre  for  the  posterior  angle  (Gegenbaur), 
which  also  unites  before  birth.  The  median  {metopic)  suture  usually  closes  towards 
the  end  of  the  second  year,  and  a  year  or  two  later  is  hardly  to  be  recognized,  except 
by  the  rudiment  at  the  lower  end.  Occasionally  the  suture  persists  ;  in  that  case  it 
remains  in  extreme  old  age  after  the  others  have  vanished.  Not  very  rarely  in 
the  fcetus  or  infant  a  dilatation  of  the  fissure,  metopic  fontanelle,  is  found  near  the 
upper  part  of  its  lower  third.  There  are  a  few  cases  of  traces  of  this  in  the  adult.1 
The  frontal  sinuses  appear  about  the  seventh  year  and  increase  up  to  adult  life. 
Later  they  are  said  to  grow  again,  since  in  the  latter  part  of  life  the  inner  table  of 
the  skull  follows  the  shrinking  brain.  As  their  size  is  dependent  chiefly  on  the 
behavior  of  the  inner  table,  we  can  infer  little  about  it  from  the  shape  of  the  fore- 
head, unless  the  superciliary  eminences  are  very  prominent. 

THE    PARIETAL    BONE. 
The  two  parietal  bones  2  complete  the  vault  of  the  skull.     Each  is  a  thin  quadri- 
lateral bone  with  an  inner  and  an  outer  table  separated  by  diploe.      Near  the  middle 

Fig.  222. 

;aWxesvnthopPos,.f 


Parietal  foramen 


Post.  sup.  angle    ^,  \] 


Ant.  sup.  angle 


Posterior  inferior 


Anterior  inferior  angle 


Mastoid 
Right  parietal  bone,  outer  s 


on  the  convex  external  surface  is  the  parte tal  eminence?  where  ossification  begins. 

It  is  very  prominent  in  childhood,  but,  as  a  rule,  is  not  very  evident  in  the  adult. 

Crossing  this  surface  below  the  middle  are  two  nerved  lines*  continuous  with  those 

1Schwalbe  :  Zeitschrift  fiir  Morph.  und  Anthrop.,  Bd.  iii.,  1901. 

20ssa  parietalia.     3Tuber  parietale.     4  Linac  temporales 


HUMAN    ANATOMY. 


into  which  the  temporal  crest  of  the  frontal  divides.  The  superior  crosses  the  bone, 
ending  at  its  posterior  border.  The  inferior  turns  down  towards  the  posterior 
part  so  as  to  reach  the  lower  border  to  become  continuous  with  the  supramastoid 
crest  of  the  temporal.  In  the  middle  of  their  course  the  lines  are  about  two  centi- 
metres apart.  The  space  between  them  is  a  little  smoother  than  the  surface  above 
and  below.  It  is  uncommon  to  be  able  to  trace  both  lines  throughout.  The  inferior 
is  usually  the  better  marked.  Sometimes  a  part  of  each  is  suppressed.  The  identity 
of  a  single  line  is  shown  by  its  termination.  Near  the  upper  posterior  angle  is  a 
minute  pin-hole,  the  parietal  foramen?  which  transmits  a  vein.  This  foramen  is  very 
often  wanting,  and,  when  visible,  may  be  closed.  In  very  rare  cases  it  is  a  large 
hole,  which  may  even  admit  a  finger.  It  is  occasionally  double.  The  internal 
surface  is  smooth  and  glistening,  as  is  the  case  throughout  the  inside  of  the  cranium. 
It  is  marked  by  tree-like  grooves  for  the  branches  of  the  middle  meningeal  artery. 

Fig.  223. 


Groove  for  longitudi- 


Post.  sup.  angle 


Ant.  sup.  angli 


Right  parietal  bone, 


One  of  these  starts  close  to  the  anterior  lower  angle,  being  at  first  very  deep  and 
sometimes  a  canal  for  a  short  distance.  Its  situation  is  exceedingly  constant.  One 
or  two  other  branches  appear  in  the  posterior  half  of  the  lower  border.  The  superior 
longitudinal  sinus  rests  in  a  groove 2  completed  by  both  bones  along  the  upper  border. 
This  groove  is  rarely  symmetrical,  being  generally  largest  on  the  right.  At  the 
posterior  inferior  angle  there  is  a  small  surface  completing  the  groove :!  of  the  lateral 
sinus  at  the  point  at  which  it  turns  from  the  occipital  into  the  temporal  bone.  Pacchi- 
onian depressions  are  small  pits  of  varying  size  and  number,  found  in  the  upper  part 
of  the  inner  surface,  and  most  commonly  near  the  groove  for  the  longitudinal  sinus, 
which  contain  the  Pacchionian  bodies  of  the  arachnoid.  The  largest  might  receive 
the  tip  of  the  little  finger. 

The  anterior,  superior,  and  posterior  borders  are  all  jagged.  The  anterior 
border  meets  the  frontal,  overlapping  it  below,  overlapped  above.  The  superior 
border  meets  that  of  its  fellow.      The  serrations  are  most  developed  in  the  middle, 

1  Foramen  parietale.     -  Sulcus  sagittate.     ■'  Sulcus  transversus. 


THE   SUPERIOR   MAXILLA.  199 

the  end  of  the  suture  behind  the  parietal  foramina  being  nearly  straight.  The  pos- 
terior border  interlocks  with  the  squamous  portion  of  the  occipital  by  a  very  irregular 
line  of  suture.  The  inferior  border,  concave  in  the  middle,  is  bevelled  on  its  outer 
surface,  except  behind.  It  is  covered  anteriorly  by  the  top  of  the  great  wing  of  the 
sphenoid,  and  along  the  concavity  by  the  squamous  part  of  the  temporal.  The  pos- 
terior portion  presents  a  point  at  the  back  of  the  concavity  which  fits  into  an  angle 
between  the  squamous  and  mastoid  parts  of  the  temporal.  Behind  this  it  is  thick 
and  jagged  for  the  top  of  the  mastoid  portion.  The  anteiior  superior  corner  is  about 
a  right  angle.  The  inferior  one  is  somewhat  drawn  out.  The  superior  posterior 
corner  is  rounded.      The  inferior  is  cut  off. 

Parietal  impressions  is  the  term  applied  to  depressions  which  are  observed 
very  exceptionally  on  the  outer  surface  of  the  parietal  bones  above  the  parietal  emi- 
nences and  near  the  upper  border.  They  are  usually  large, — i.e. ,  some  seven  centi- 
metres long  by  five  or  six  centimetres  broad.  Some  sections  have  shown  that  they 
involve  only  the  outer  surface  of  the  bone.  A  thinning  above  the  sagittal  suture 
has  also  been  observed,  and  even  one  over  the  lambdoidal  suture.  These  latter  are 
generally  considered  atrophic  changes  occurring  in  old  age.  The  same  explanation 
is  offered  for  the  parietal  impressions  proper,  and  very  possibly  with  justice  ;  still,  the 
case  is  reported  by  Shepherd '  of  an  old  woman  who  remembered  having  them  all 
her  life,  and  who  declared  that  her  father  had  them  likewise.  This  would  point  to 
their  being  occasionally  both  congenital  and  hereditary.  The  late  Professor  Sir 
George  Humphry  2  observed  them  in  the  orang-outang. 

Articulations. — Each  parietal  articulates  with  its  mate,  the  occipital,  temporal, 
sphenoid,  and  frontal  bones. 

Development. — A  single  centre  appears  in  the  membrane  at  the  end  of  the 
second  fcetal  month.  According  to  Toldt  (Lotos,  1882),  this  is  double,  consisting 
of  an  upper  and  a  lower  part,  which  soon  fuse.  The  centre  becomes  very  prominent, 
and  bone-rays  extend  from  it,  making  the  bone  very  rough  till  after  birth.  The 
fontanelles  at  the  four  corners  of  the  bone  are  discussed  in  describing  the  skull  as 
a  whole  (page  231).  The  radiating  lines  of  bone  leave  an  interval  near  the  back  of 
the  upper  border  of  the  bone,  called  the  sagittal  fontane//e,  which  closes  during  the 
latter  part  of  fcetal  life.  According  to  Broca,  this  can  be  seen  at  birth  once  in  four 
times.  The  parietal  foramen  is  left  as  this  fissure  closes.  Its  occasional  great  size 
is  accounted  for  by  irregularities  in  the  process.  Very  rarely  a  suture  divides  the 
parietal  into  an  upper  and  a  lower  portion. 


THE   FACE. 

The  face  consists  of  the  orbits,  the  nose,  and  the  Jaws.  Portions  of  the  sphe- 
noid and  the  ethmoid  form  a  considerable  part  of  it,  as  has  been  described.  The 
facial  bones  are  two  superior  maxillcs,.  two  malar,  two  nasal,  two  lachrymal,  two 
palate,  two  inferior  turbinates,  the  vomer,  the  inferior  maxilla,  and  the  hyoid. 
The  future  nasal  septum,  extending  in  the  median  plane  from  the  base  of  the  skull 
to  the  upper  jaw,  is  very  early  developed  in  cartilage.  Ossification  progresses  from 
superficial  centres  on  either  side.  These  form  the  vertical  plate  of  the  ethmoid  and 
the  vomer  ;  but  a  considerable  part,  the  triangular  cartilage,  remains  cartilaginous. 

THE  SUPERIOR  MAXILLA. 
The  superior  maxilla "'  is  a  very  irregular  bone,  which  with  its  fellow  forms  the 
front  of  the  upper  part  of  the  face,  the  floor  of  the  orbit,  much  of  the  outer  wall  and 
floor  of  the  nasal  cavity,  much  of  the  hard  palate,  and  supports  all  the  upper  teeth. 
It  has  a  body,  and  malar,  nasal,  alveolar,  and  palatal  processes.  The  general  shape 
of  the  body4  is  that  of  a  four-sided  pyramid  ;  the  base  looking  towards  the  nasal 
cavity,  one  surface  forming  the  floor  of  the  orbit  and  the  other  two  the  front  and 
back  of  the  bone.   These  three  surfaces  meet  at  the  apex,  which  is  the  malar  process." 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxvii.,  1893. 

2  Ibid,  vol.  viii.,  1874. 

3  Maxilla.      4Corpus  maxillae.     5  Processus  zygoraaticas. 


HUMAN    ANATOMY. 


This  is  a  rough  triangular  surface  articulating  with  the  malar,  often  perforated,  and 
sending  downward  a  smooth  ridge  separating  the  anterior  and  posterior  surfaces  ; 
the  former  is  in  the  front  of  the  face,  the  latter  in  the  zygomatic  fossa.  The  lower 
border  of  both  is  the  alveolar  process?  which  is  simply  a  curved  row  of  tooth 
sockets  made  of  very  light  plates  of  bone,  which  are  absorbed  after  the  loss  of  the 
teeth.  The  palatal  process  2  joins  the  inner  side  of  the  body  like  a  shelf  and  supports 
the  anterior  part  of  the  alveolar  process.  The  nasal  process 3  rises  from  the  anterior 
inner  part  to  meet  the  frontal  bone.  In  certain  parts  of  the  description  it  is  con- 
venient to  disregard  these  subdivisions.  The  anterior  surface  of  the  bone  forms 
the  lower  and  outer  boundary  of  the  nasal  opening,  which  is  finished  above  by  the 
nasal  bone.  On  the  entire  skull  this  aperture  resembles  an  ace  of  hearts  inverted. 
The  lower  boundary  of  the  opening  is  slightly  raised  and  smooth.  On  the  side  it  is 
sharp.  The  pointed  anterior  nasal  spine  projects  forward  where  the  two  bones  meet 
below  the  opening.4  There  is  a  slight  depression — the  incisor  or  myrtiform  fossa — 
over  'the  lateral  incisor  tooth.  External  to  this  is  a  ridge  caused  by  the  socket  of  the 
canine  tooth.      Farther  outward  is  a  well-marked  hollow,  the  canine  fossa.      Above 


Fig.  224. 


Lachrymal  groove 
Lachrymal. notch 
Orbital  surface 


Infra-orbital  groove 


Posterior  dental  canal 


Zygomatic  surface 
Masseter 


Buccinator' 


Depres.  ales  nasi 
Alveolar  process 


Right  supe 


llary  bone,  outer  surface. 


this,  about  five  millimetres  below  the  edge  of  the  orbit,  is  the  infra-orbital  foramen, 
transmitting  the  nerve  and  artery  of  the  same  name.  This  surface  is  bounded  above 
and  externally  by  the  malar  process. 

The  zygomatic  surface  is  in  the  main  convex,  except  for  a  smooth  concavity 
behind  the  malar  process.  The  lower  posterior  portion,  the  tuberosity?  is  rough, 
and  presents  at  its  upper  part  two  or  three  minute  posterior  dejital  foramina*  by 
which  those  nerves  enter  canals  in  the  bone.  The  smooth  superior  or  orbital 
surface,  slanting  a  little  downward  and  outward,  is  triangular.  The  posterior 
border  is  free,  forming  the  lower  limit  of  the  spheno-maxillary  fissure,  and  running 
obliquely  forward  to  the  malar  process.  The  anterior  border  passes  outward  and 
backward  to  the  same.  The  inner  border  is  in  the  main  antero-posterior.  The 
hind  end  slants  outward,  articulating  with  the  little  triangular  orbital  surface  of  the 
palatal.  Anterior  to  this,  the  border  joins  the  os  planum  of  the  ethmoid  ;  and  anterior 
to  the  latter,  at  the  base  of  the  nasal  process,  lies  a  semicircular  indentation,  the  lachry- 
mal notch?  the  posterior  border  of  which  touches  the  lachrymal  bone.  The  deep  infra- 
orbital groove*  runs  more  than  half  across  the  orbital  surface  from  behind,  and  then 
*  For  a  more  detailed  account,  see  the  section  on  the  Nasal  Cavity. 


1  Foramina    alveola 


THE    SUPERIOR    MAXILLA.  201 

becomes  a  canal,  opening  at  the  corresponding  foramen  in  front.  Occasionally  a 
suture  marks  the  course  of  the  canal.  The  internal  wall  of  the  body  presents 
on  the  separate  bone  a  very  large  opening  into  the  antrum,  or  maxillary  sinus, 
which  is  much  reduced  when  the  other  bones  are  in  place.  In  front  of  this  opening 
the  wall  is  smooth  and  concave,  forming  a  part  of  the  lachrymal  groove.  Near  the 
level  of  the  top  of  the  body  there  is  the  rough  horizontal  inferior  turbinate  crest  for 
articulation  with  that  bone.  The  wall  at  the  back  of  this  surface  has  a  vertical 
groove,  which,  when  the  palate  bone  is  in  place,  forms  part  of  the  posterior  palatine 
canal,  opening  near  the  back  of  the  hard  palate  and  transmitting  the  descending 
palatine  artery  and  the  anterior  palatine  nerve. 

The  malar  and  the  alveolar  processes  have  been  incidentally  described.  The 
nasal  or  asce?iding  process  rises  at  the  inner  side  of  the  orbit.  It  is  thin  below,  with 
an  outer  surface  towards  the  face  and  an  inner  towards  the  nose.  The  top  is  thick 
and  rough,  joining  the  frontal.  The  lachrymal  groove1  for  the  tear-sac  and  the  nasal 
duct  begins  on  its  outer  surface  and  passes  down  behind  it,  making  a  deep  notch  at 
the  front  of  the  orbital  plate.  The  lower  part  of  the  process  extends  down  as  far  as 
the  inferior  turbinate  crest,  forming,  with  the  lachrymal,  the  inner  side  of  the  groove. 
The  point  of  junction  of  the  front  border  of  the  groove  with  the  orbital  plate  is 
usually  marked  by  the  lachrymal  tubercle.  The  inner  side  shows  above  at  the  pos- 
terior border  some  cellular  spaces  completing  the  anterior  ethmoidal  cells,  bounded 
below  by  a  ridge,  the  crista  ethmoidalis,  which  articulates  with  the  front  of  the  middle 
turbinate  bone.  Below  it  the  bone  is  concave,  forming  part  of  the  vestibule  of  the 
•nose  ;  above  it  is  plane  and  marked  with  vascular  grooves. 

The  palatal  process  projects  inward  from  the  anterior  two-thirds  of  the  body 
and  joins  the  alveolar  process  in  front.  It  is  very  smooth  above,  the  mucous  mem- 
brane being  lightly  attached  to  it.  It  is  slightly  concave  from  side  to  side,  and  has 
a  raised  edge  in  front.  It  is  also  raised  along  the  median  line  to  form  the  nasal  crest'1 
with  its  fellow.  The  front  of  this  ridge,  called  the  incisor  crest,  suddenly  rises  to  a 
higher  level  and  juts  out  below  the  nose  as  the  anterior  nasal  spine.  The  vomer 
rests  on  the  ridge,  except  at  the  front,  where  its  place  is  taken  by  the  triangular 
cartilage.  The  under  surface  of  the  palatal  process,  horizontal  behind,  slants  down- 
ward in  front  to  the  incisor  teeth.  It  is  rough  for  the  firm  support  of  the  mucous 
membrane.  The  median  surface  of  the  palate  is  rough  to  join  with  its  fellow.  A 
little  behind  the  incisors  it  shows  a  groove  in  the  lower  part,  which  becomes  a  canal 
in  the  upper,  and  opens  into  the  floor  of  the  nasal  fossa  of  either  side.  Thus  there 
are  two  canals  above  and  one  below,  like  a  Y  placed  transversely.  These  are  the 
canals  of  Stenson,  which  transmit  an  artery  connecting  the  vessels  of  the  nose  and 
mouth.  Their  common  orifice  is  called  the  anterior  palatine  canal}  Into  this  open 
two  minute  canals,  the  left  anterior  to  the  right,  made  by  the  junction  of  the  bones. 
These  are  the  canals  of  Scarpa,  and  transmit  the  naso-palatine  nerves.  They  are 
by  no  means  always  to  be  found.  The  canals  of  Stenson  represent  the  anterior 
palatine  canal  of  lower  animals,  which  in  them  is  generally  double  throughout.  In 
man  the  whole  opening  is  usually  closed  by  mucous  membrane.  The  back  of  the 
palate  process  joins  the  horizontal  plate  of  the  palate  bone,  which  completes  the 
palate  behind. 

The  antrum  or  maxillary  sinus4  is  a  large  cavity  within  the  body,  the  shape 
of  which  it  follows  in  the  main,  although  with  many  variations  of  size.  The  large 
opening  on  its  inner  wall  is  much  diminished  when  the  palate,  the  ethmoid,  and  the 
inferior  turbinate  are  in  place.  It  lies  near  the  anterior  end  of  the  lateral  wall  of  the 
middle  nasal  meatus,  covered  by  the  middle  turbinate.  A  small  part  of  the  roof  of 
the  antrum  is  often  formed  by  the  palate  bone,  and  sometimes  the  cavity  extends  into 
the  malar.  The  inner  and  most  of  the  posterior  and  outer  walls  are  generally  very 
thin,  as  is  also  the  roof,  except  around  the  infra-orbital  canal,  which  projects  into  the 
antrum.  The  development  outward  towards  the  malar  bone  varies  much,  as  does 
the  downward  and  forward  growth  towards  the  alveolar  process.  The  lower  border 
of  the  antrum  is  usually  a  trifle  below  the  level  of  the  floor  of  the  nares.  According 
to  C.  Reschreiter,0  this  is  a  male  characteristic.  Be  that  as  it  may,  it  certainly  is  in 
5Zur  Morphologie  des  Sinus  Maxillaris,  Stuttgart,  1S7S. 

1  Sulcus  lacrlmalis.     -  Crista  nasalis.     3  Forar 


202  HUMAN   ANATOMY. 

accord  with  the  larger  size  of  the  sinuses  in  man.  The  internal  surface  is  largely 
smooth.  Bony  ridges  springing  from  various  parts  tend  to  subdivide  the  cavity. 
They  sometimes  form  little  pockets  above  the  teeth.  According  to  Gruber,1  it 
may  in  rare  cases  be  completely  subdivided  into  a  smaller  posterior  chamber  and  a 
larger  front  one,  both  of  which  open  into  the  nasal  cavity.  The  lowest  part  of  the 
antrum  is  indented  by  the  roots  of  the  molars  and  of  the  second  bicuspid,  at  least 
very  frequently.  The  first  and  second  molars  always  indent  it,  but  the  bicuspid  and 
the  wisdom-tooth  may  not.      (For  further  details,  see  Teeth,  page  1556.) 

Articulations. — All  the  bones  of  the  face,  except  the  lower  jaw  and  the  hyoid, 
touch  the  superior  maxilla.  It  has  been  described  as  the  key  to  the  architecture 
of  the  face.  The  palate  bone  both  completes  the  palate  and  lies  between  this  bone 
and  the  pterygoids,  closing  the  posterior  part  of  the  opening  into  the  antrum.  The 
malar,  joining  the  process  of  that  name,  makes  the  prominence  of  the  cheek  and 
helps  to  bound  the  orbit.  The  nasals  complete  the  anterior  nasal  aperture.  The 
lachrymals  and  ethmoid  touch  the  inner  side  of  the  orbital  plate,  and  the  ethmoid 
the  inner  surface  of  the  nasal  process.      The  frontal  rests  on  the  nasal  process,  the 

Fig.  235. 


Ethmoidal  crest 
Middle  meat 

Inferior  turbinate  crest 
Inferior  meat 

Incisor  crest  —-^=*<^M—~^]&\>x\\::<'  '    J  '    '  '     J^& Posterior  palatine  canal 

'   '•'■  -  -^=%^>  .^sUgtM Nas,l 

Palatal  process 

Anterior  palatine  canal' 
Alveolar  proces: 


llary  bone,  inner  surface. 


inferior  turbinate  rests  on  the  inner  surface  of  the  maxilla,  and  the  vomer  on  the  crest 
made  by  the  union  of  the  palate  processes. 

Development  and  Changes. — There  are  certainly  four  chief  centres,  all  of 
which  appear  at  about  the  end  of  the  sixth  week  of  fcetal  life.  Three  of  them  fuse 
very  rapidly.  There  is  one  on  either  side  of  the  infra-orbital  groove,  a  malar  and 
an  orbito-faciai ',  and  below  and  internally  a  palatine.  The  fourth,  the  iiitermaxillary, 
stays  distinct  longer.  It  comprises  the  front  of  the  palate  as  far  back  as  the  anterior 
palatine  canal,  and  represents  a  very  constant  separate  ossification  in  vertebrates, 
the  premaxilla,  in  front  of  the  maxilla,  except  in  certain  mammals  in  which  it  is 
between  them.  It  bears  the  incisor  teeth,  and  at  the  third  fcetal  month  fuses  with 
the  maxilla.  As  the  intermaxillary  grows,  the  suture  in  the  roof  of  the  mouth  per- 
sists for  a  time.  It  is  very  plain  at  birth  and  often  for  a  year  or  two  later.  Some- 
times it  is  seen  in  the  adult.  At  first  the  posterior  suture  is  very  close  to  the 
incisors,  but  as  it  grows  the  intermaxillary  forms  a  large  part  of  the  palate.  If 
detached,  it  is  seen  notched  behind,  so  as  to  form  the  inner  wall  of  the  upper  part  of 


1  Virchow's  Archiv,  Bd.  lxiii. 


THE    SUPERIOR    MAXILLA.  203 

Stenson's  canal.  The  suture  is  rarely  seen  above  and  never  in  front,  being  concealed 
by  the  plate  forming  the  front  of  the  bone.  Albrecht '  asserts  that  each  intermaxil- 
lary is  double.  In  support  of  this  is  the  fact  that  in  cleft  palate  the  fissure  does 
not  always  come  between  the  incisor  teeth  and  the  canine,  but  an  incisor  may  be 
found  on  its  outer  side.  In  reply  to  this  it  has  been  pointed  out  that  three  incisors 
on  each  side  occasionally  occur,  and  that,  as  anomalies  are  likely  to  be  found  in 
groups,  this  is  merely  an  irregular  arrangement.  Moreover,  in  cases  in  which  the 
cleft  has  but  one  incisor  on  each  side  of  it,  it  is  well  argued  that  the  original  position 
of  the  tooth-sacs  has  no  certain  relation  to  the  bones  (Th.  Kolliker2).  In  sup- 
port of  Albrecht  is  the  occasional  presence  of  a  line  subdividing  the  lower  surface 
of  the  premaxilla  ;  but,  on  the  other  hand,  it  is  not  certain  that  this  is  really  a 
suture,  and  there  seems  no  evidence  that  the  premaxilla  has  two  centres  of  ossifi- 
cation. While  there  is  much  that  is  plausible  in  Albrecht' s  views,  they  cannot  be 
considered  as  established. 

Sir  William  Turner3  thus  concludes  an  excellent  discussion  of  the  question  : 
"  What  is  yet  wanted,  however,  to  give  completeness  to  the  evidence  of  the  division 
of  the  intermaxillary  bone  into  an  inner  and  an  outer  part  is  the  discovery  that  the 
intermaxillary  bone  normally  rises  from  two  distinct  centres  of  ossification,  one  for 
the  inner,  the  other  for  the  outer  part.     Of  this  we  have  at  present  no  evidence. 


Fig.  227. 

Lachrymal  groove 


Inferior  surface  of  upper  jaw  at  about  birth. 


Ant.  palatine  canal  Palatal  process 

Mesial  surface  of  upper  jaw  at  about  birth. 


But,  in  connection  with  this  matter,  we  ought  not  to  forget  that  it  is  quite  recently 
that  the  embryological  evidence  of  the  origin  of  the  intermaxillary  part  of  the  human 
upper  jaw  from  a  centre  distinct  from  that  of  the  superior  maxilla  has  been  completed. 
And  yet  for  nearly  a  century,  on  such  minor  evidence  as  was  advanced  by  Goethe, 
— viz.,  the  suture  on  the  hard  palate  extending  through  to  the  nasal  surface, — 
anatomists  have  believed  and  taught  that  the  human  upper  jaw  represented  both  the 
superior  and  intermaxillary  bones  in  any  other  mammal.  Where  a  question  in 
human  embryology  hinges  upon  an  examination  of  parts  in  a  very  early  stage  of 
development,  we  often  have  to  wait  for  many  years  before  an  appropriate  specimen 
falls  into  the  hands  of  a  competent  observer." 

The  upper  and  lower  sides  of  the  bone  are  at  first  very  near  together.  The 
tooth-sacs  are  directly  below  the  orbit.  In  the  latter  part  of  foetal  life  the  antrum 
appears  as  a  slight  pouch  growing  in  from  the  nasal  side.  As  the  bone  grows,  the 
antrum  remains  for  some  time  on  the  inner  side  of  the  infra-orbital  canal.  The  outer 
part  of  the  bone,  especially  towards  the  malar,  is  filled  with  diploe,  which  subse- 
quently is  absorbed  as  the  sinus  extends  outward.  By  the  end  of  the  second  year 
the  cavity  has  extended  above  the  first  permanent  molar  ;  by  the  twelfth  or  thirteenth 
year,  when  the  second  molar  has  appeared,  the  antrum  approaches,  though  it  has 
not  yet  reached,  its  definite  shape.  During  the  first  dentition  it  is  separated  by  the 
uncut  teeth  from  the  front  of  the  bone. 


1  Sur  les  quatres  os  intermaxillaires,  Soc.  d'Antropol.  de  Bruxelles,  1S83.     Die  morpho- 
logische  Bedeutung  der  Kiefer-,  Lippen-,  und  Gesichtsspalten,  Langenbeck's  Archiv,  Bd.  xxi. 

2  Ueber  das  Os  intermaxillare  des  Menschen.     Nova  Acta  der  Leopold.  Carol.  Akad.  der 
Naturforschen,  Bd.  xliii.,  1882. 

3  Journal  of  Anatomy  and  Physiology,  vol.  xix.,  1895. 


204 


HUMAN    ANATOMY. 


After  the  loss  of  the  teeth  from  old  age  or  otherwise  the  alveolar  process  is 
absorbed.      Senile  atrophy  is  particularly  marked  in  this  bone. 


<  irbital  surface 


Fig.  22S. 

Orbital  process 


THE    PALATE    BONE. 
This1  consists  of  a  horizontal  and  a  vertical  plate  and  three  processes,  the  py- 
ramidal, the  orbital,  and  the  sphenoidal.     The  horizontal  plate2  is  quadrilateral.     It 

completes  with  its  fellow  the  hard 
palate,  filling  the  space  left  vacant  be- 
tween the  back  parts  of  the  superior 
maxillae.  Its  superior  surface  is 
smooth  like  the  rest  of  the  floor  of 
the  nares,  and  the  lower  rough,  but 
less  so  than  that  of  the  superior  max- 
illa. The  anterior  border  fits  the  back 
of  the  palatal  process  of  the  maxilla  ; 
the  inner  border  is  rough  to  meet  its 
fellow,  and  raised  into  a  nasal  crest 
meeting  the  back  of  the  lower  edge 
of  the  vomer.  This  is  prolonged 
behind  to  form  with  the  other  the 
posterior  nasal  spine.  The  posterior 
border  is  smooth  and  concave  from 
side  to  side.  The  outer  border  joins 
the  vertical  plate.3  This  is  very 
thin,  with  an  outer  and  an  inner  sur- 
face. It  is  surmounted  by  two  processes,  between  which  is  a  deep  notch  which 
forms  three-quarters  or  more  of  the  spheno-palatine  foramen^  when  the  bone  is  in 
position,  so  that  both  processes  touch  the  body  of  the  sphenoid.  The  outer  surface 
presents  near  the  top  a  smooth  vertical  surface  forming  part  of  the  pterygo-maxillary 

Fig.  229. 

For  ethmoid  Orbital  process 


HORIZONTAL  PLATE 
For  int.  pterygoid  plate 

Right  palate  bone  from  beh 


Spheno-maxillary  fossa 
Spheno-palatine  notch 


VERTICAL  PLATE 


For  ext.  pteryg. 

plate 
Pterygoid  fossa 


TUBEROSITY 


Sup.  turbinate  crest 
Sphenoidal  process 
Middle  nasal 
meatus 

Inf.  turbinate  crest 


Inferior  meatus 
Tuberosity 


Nasal  crest 
Inner  aspect  of  right  palate  bone  in  place. 


Part  of  inferior  turbinate  removed. 


fissure.  This  narrows  below  into  a  groove  which  makes  the  posterior  palatine 
canal  when  applied  to  the  corresponding  groove  in  the  maxilla.  In  front  of  this 
the  surface  is  at  first  rough  where  it  rests  against  that  bone,  and  more  anteriorly 
smooth  where  it  closes  the  lower  part  of  the  opening  of  the  antrum  by  an  irregular 

1  Os  palatinum.     -  Pars  horizontalis.     ^Pars  perpendicularis.     4  Foramen  spucnupalatinum. 


THE  PALATE  BONE.  205 

prolongation.  The  inner  surface,  looking  towards  the  nasal  cavity,  is  free  and 
smooth.  It  is  crossed  below  the  middle  by  a  ridge,  the  inferior  turbinate  crest1  for 
the  posterior  attachment  of  the  inferior  turbinate  bone.  Nearly  on  a  level  with  the 
base  of  the  notch  is  another  ridge  faintly  marked  behind  it ;  this  is  the  superior 
turbinate  crest 2  for  the  middle  turbinate  bone  of  the  ethmoid.  A  small  part  of  the 
top  of  the  vertical  plate  looks  into  the  superior  meatus.  The  pyramidal  process, 
or  tuberosity,  is  the  only  solid  part  of  the  bone.  It  projects  backward  and  some- 
what outward  from  the  lower  part  of  the  vertical  plate.  A  smooth,  hollowed, 
triangular  surface  fits  into  the  space  left  between  the  pterygoid  plates,  completing 
the  floor  of  the  pterygoid  fossa  ;  on  one  side  of  this  is  a  groove  for  the  front  of  the 
internal  pterygoid  plate  and  on  the  other  a  rough  surface  for  that  of  the  outer. 
Thus,  through  the  palate  bone,  the  pterygoids  support  the  back  of  the  upper  jaw. 
The  outer  side  of  the  process  rests  against  the  tuberosity  of  the  maxilla  in  front  of 
the  tip  of  the  external  pterygoid  plate.  The  orbital  process,  is  the  anterior  of  the 
two  processes  above  the  vertical  plate,  the  larger  and  higher,  so  called  because  it 
forms  a  small  part  of  the  floor  of  the  orbit  near  its  apex  on  the  inner  side.  This 
little  surface,  on  the  outer  side  of  the  process,  is  triangular,  one  edge  articulating 
with  the  upper  jaw  and  one  with  the  os  planum,  the  hind  edge  being  free.  Another 
smooth  surface  looks  outward  and  backward  towards  the  spheno-maxillary  fossa. 
It  is  separated  from  the  preceding  surface 

by  an  angle.      Three  other  surfaces  rest  Fig.  230. 

against  other  bones.      An  anteroinferior  SV^/°rbital  surface 

one  joins  the  maxilla,  sometimes  helping 
to  close  the  antrum  ;  an  anterior  one 
touches  the  ethmoid,  bounding  part  of  a 
cell  ;  and  a  small  one,  just  at  the  top  of 
the  notch,  touches  the  sphenoidal  spongy 
bone.  The  posterior  or  sphenoidal 
process  has  a  narrow  upper  surface, 
which,  joining  the  sphenoidal  spongy 
bone  near  the  base  of  the  internal  ptery- 
goid plate,  completes  the  pterygopalatine 
ca?ial.  This  surface  reaches  the  edge  of 
the  vomer.  The  internal  surface,  slant- 
ing a  little  downward,  is  free,  looking  into 
the  nasal  fossa.      The  outer  surface  is  di-  Right  palate  bone,  outer  aspect, 

vided  by  a  vertical  ridge  into  an  anterior 

part,  free  and  smooth,  looking  into  the  spheno-maxillary  fossa,  and  a  scale-like  pos- 
terior portion  which  rests  against  the  external  pterygoid  plate. 

The  Spheno-Maxillary  Fossa. — When  the  palate  bone  is  applied  to  the 
sphenoid  and  the  maxilla,  the  spheno-palatine  foramen  forms  a  window  between  the 
nasal  chamber  and  a  little  hollow,  the  spheno-maxillary  fossa,  just  below  and  behind 
the  apex  of  the  orbit.  The  posterior  wall  of  this  space,  formed  by  the  smooth  sur- 
face of  the  sphenoid  above  the  pterygoid  plates,  is  pierced  by  the  foramen  rolundum 
and  the  Vidian  canal.    Below,  it  narrows  funnel-like  into  the  posterior  palatine  canal. 

Articulations. — The  palate  bone  articulates  with  its  fellow,  the  superior  max- 
illary, sphenoid,  ethmoid,  vomer,  and  inferior  turbinate  bones. 

Development. — Ossification  begins  from  a  single  centre  appearing  in  mem- 
brane near  the  end  of  the  second  fcetal  month  at  about  the  junction  of  the  vertical 
and  horizontal  plates.  It  is  very  delicate  throughout  fcetal  life,  but  the  posterior 
free  edge  of  the  palate  is  very  early  much  denser.  Originally  the  horizontal  plate  is 
larger  than  the  vertical  one  ;  at  birth  they  are  about  equal. 

THE  VOMER. 

The  vomer11  is  a  thin,  irregularly  quadrilateral  plate,  forming  the  back  and  lower 
part  of  the  nasal  septum.      The  superior  border  expands  laterally  into  two  wings,  or 
altz,  which  articulate  with  the  under  surface  of  the  body  of  the  sphenoid,  and  enclose 
a  medium  groove  for  the  rostrum.      Laterally,  the  wings  fit  under  the  vaginal  prO- 
^rista  turbiDalis.     -  Crista  ethmoidals.     :i  Vomer. 


2o6 


HUMAN    ANATOMY. 


cesses  of  the  sphenoid.      The  posterior  border  is  free.      Thick  above,  just  under  the 
alae,   it  soon  narrows  and  runs  downward  and  forward.       The  inferior  border  fits 


Naso-palatine  groove 


Vomer  in  place,  from  left  side. 


Fig.  232. 


between  the  nasal  crests  of  the  palatals  and  maxilla;,  and  anteriorly  changes  its  direc- 
tion so  as  to  rise  over  the  higher  incisor  crests  as  far  as  the  anterior  palatine  canal. 
The  anterior  border  is  the  longest.  Its 
upper  part  articulates  with  the  back  of 
the  vertical  plate  of  the  ethmoid,  the 
lower  part  with  the  triangular  cartilage  of 
the  nasal  septum.  The  latter  is  received 
into  a  groove  which  may  extend  behind 
the  vertical  plate.  The  sides  of  the  vomer 
are  covered  with  mucous  membrane. 
They  present  a  few  irregularities,  the 
most  important  of  which  is  a  groove  on 
either  side,  nearer  the  front  than  the 
back,  for  the  naso-palatine  nerve  ;  and, 
just  anterior  to  this,  a  thickening  which  is  normally  insignificant, 
but  occasionally  is  developed  to  one  side  or  the  other,  forming  a 
spur  which  may  nearly  close  the  passage. 

Articulations. — The  vomer  articulates  with  the  sphenoid, 
ethmoid,  palate,  and  superior  maxillary  bones  and  the  median 
triangular  cartilage. 

Development. — It  is  to  be  remembered  that,  although  the 
vomer  becomes  through  ossification  one  of  the  separate  bones  of 
the  face,  at  an  early  period  it  is  but  a  portion  of  the  septal  car- 
tilage without  any  hint  of  demarcation.  A  single  centre  appears 
before  the  close  of  the  second  fcetal  month  in  the  membrane  at  the  under  border 
of  the  cartilage,  which  then  forms  the  septum.  This  grows  upward  on  either  side 
of  the  cartilage  until  the  bone  is  complete.  The  young  bone  shows  very  clearly 
its  formation  in  two  plates  ;  but  in  the  adult  this  appears  only  in  the  groove  between 
the  wings  and  in  the  lower  part  of  the  front  border,  which  still  receives  the  triangular 
cartilage. 


THE    LACHRYMAL    BONE. 


207 


THE    LACHRYMAL    BONE. 

The  lachrymal  bone '  is  an  exceedingly  thin  osseous  plate,  filling  the  vacancy  in 
the  inner  wall  of  the  orbit  between  the  orbital  plate  of  the  ethmoid  and  the  ascending 
process  of  the  superior  maxilla.  It  is  quadrilateral,  the  long  diameter  being  vertical, 
and  presents  an  outer  surface  directed  towards  the  orbit  and  an  inner  surface  towards 
the  nasal  fossa.  The  latter  rests,  in  part,  against  the  turbinate  process  of  the  eth- 
moid, which  more  or  less  overlaps  it.    It  closes  the  infundibulum  and  several  anterior 


Orbital  surface 


Lachrymal  crest 


Nasal  process  of  sup.  max 
Lachrymal  groove 


Hamular  process 


Right  lachrymal  bone  in  place,  outer  aspect. 


Fig.  235. 


ethmoidal  cells.  The  lower  and  anterior  portion  of  this  surface  forms  a  part  of  the 
wall  of  the  middle  nasal  meatus.  The  outer  surface  is  subdivided  by  a  vertical  ridge,2 
marking  off  a  smaller  anterior  part,  which  forms  the  lachrymal groove /8  and,  joining 
the  corresponding  groove  of  the  superior  maxillary,  complete  the  lachrymal  canal. 
The  posterior  part  of  the  orbital  surface  is  plane.  The  hamular 
process*  is  a  small  tongue  of  bone  curving  forward  from  the  lower 
part  of  the  dividing  ridge  to  form  the  posterior  border  of  the 
canal  at  the  floor  of  the  orbit.  The  descending  process  is  a 
downward  prolongation  of  the  grooved  portion,  forming  part  of 
the  wall  of  the  canal,  and  meeting  the  lachrymal  process  of  the 
inferior  turbinate.  The  bone  also  articulates  with  the  frontal  by 
its  upper  surface,  and  with  the  front  of  the  os  planum  by  its  pos- 
terior border. 

Articulations. — The  lachrymal   articulates  with   the  eth- 
moid, frontal,  superior  maxillary,  and  inferior  turbinate  bones. 

Development. — Ossification  is  from  a  single  centre  said 
to  appear  in  the  eighth  foetal  week,  although  the  variations  imply 
extra  ones.  Macalister5  enumerates  six  separate  ossicles  which 
may  occur  about  the  bone.  It  varies  greatly  in  size  ;  it  may  be  wanting,  though 
rarely,  and  sometimes  is  very  large.  A  considerable  development  of  the  hamular 
portion,  which  may  be  separate,  represents  the  condition  of  prosimians  and  platyrhine 
apes.6     It  may  be  subdivided  or  perforated.' 

5  Proc.  Royal  Society,  1884. 

6  Gegenbaur  :  Morph.  Jahrbuch,  Bd.  vii. 

7  Le  Double  :  Essai  sur  la  Morphogenie  et  les  Variations  du  Lacrymal,  1900  ;  and  Zabel : 
Varietaten  und  Vollstandiges  Fehlen  des  Tranenbeins  beim  Menschen,  Anat.  Hefte.  Bd.  xv., 
Heft  1,  1900. 


Right  lachrymal  bone, 
inner  aspect.  Upper 
part  completes  anterior 
ethmoidal  cells,  lower 
looks  into  middle  nasal 
meatus. 


208 


HUMAN    ANATOMY. 


THE  INFERIOR  TURBINATE  BONE. 
This  is  an  elongated  curved  bone '  placed  in  the  lateral  wall  of  the  nasal  cavity 
below  the  superior  and  middle  turbinates,  which  are  parts  of  the  ethmoid.    The  inner 

convex  surface  is  pitted  and  grooved  by  the 
cavernous  tissue  beneath  the  mucous  membrane. 
This  condition  is  continued  round  the  free  lower 
border  a  little  way  up  the  outer  side.      The  rest 


Right  inferior  turbinate  bone  in  place,  inner  aspect. 


Fig 


of  the  outer  surface,   overhanging  the  inferior  nasal  meatus,  is  nearly  smooth.      The 

ends  of  the  bone  are  pointed.     They  are  connected  below  by  the  regular  curve  of 

the  inferior  border.  The  upper  border  is 
thin  and  irregular.  It  articulates  in  front 
with  the  inferior  turbinate  crest  of  the  max- 
illa. Behind  this  rises  the  lachrymal  process* 
— the  highest — to  meet  the  lachrymal  bone. 
Posterior  to  this  the  maxillary  process*  bends 
outward  and  downward.  It  does  not,  how- 
ever, usually  hook  over  the  upper  edge  of 
the  plate  bounding  the  entrance  of  the  an- 
trum, but  meets  it  edge  to  edge,  consider- 
ably   reducing    the    opening.       Still    farther 

back  is  the  ethmoidal  process*  meeting  the  uncinate  process  ;  and,  finally,  the  border 

rests  on  the  inferior  turbinate  ridge  of  the  palate  bone. 

Articulations. — The  inferior  turbinate  articulates  with  the  superior  maxillary, 

ethmoid,  palate,  and  lachrymal  bones. 

Development. — Ossification    proceeds   from    a    single  center  which  appears 

about  the  middle  of  fcetal  life. 


Right  inferior  turbinate  bone,  outer  aspect 


-  Proc,  lacriraalis. 


1  Proc.  ethraoidalis. 


THE  NASAL  AND  MALAR  BONE. 


209 


Rieht  nasal  bo 


THE  NASAL  BONE. 

The  two  nasal  bones1  bound  the  anterior  nasal  opening  above.  Each  one  is  a 
four-sided  plate  with  an  outer  and  an  inner  surface.  The  upper  end  is  thick  and 
jagged,  articulating  with  the  frontal  above  and  also  behind.  The  anterior  border, 
which  articulates  with  its  fellow,  is  thick  above  and  thin  below.  When  the  two 
bones  are  in  place,  the  united  upper  portions  of  these  borders  form  posteriorly  the 
nasal  crest,  which  articulates 

with  the  nasal  spine  of  the  Fig.  23S. 

frontal,  and  sometimes  with 
the  vertical  plate  of  the  eth- 
moid below  it.  The  pos- 
terior border  joins  the  as- 
cending process  of  the 
maxilla.  The  thin  lower 
border,  slanting  downward 
and  outward,  has  one  or 
two  indentations.  The  outer 
surface  is  broader  below 
than  above.  It  is  depressed 
in  the  upper  third,  and  has 
there  a  forame?i  for  a  vein. 
The  extreme  upper  part  of 
the  inner  surface  is  rough 
to  join  the  frontal.  Below 
this  it  is  smooth  where  it 
forms  the  front  of  the  nasal 
chamber  ;  the  lower  part  of  the  inner  surface  sometimes  seems  hollowed  out.  A 
vertical  groove  for  the  nasal  nerve  ends  near  the  notch  in  the  lower  border. 

Articulations. — The  nasal  bone  articulates  with  the  frontal,  ethmoid,  superior 
maxilla,  and  the  opposite  nasal. 

Development. — Ossification  spreads  from  a  centre  appearing  about  the  eighth 
week  of  foetal  life.  At  first  the  bone  is  broad  and  short.  Occasionally  a  little 
Wormian  bone  is  found  in  the  median  line  between  the  nasals  and  the  frontal.  The 
two  bones  sometimes  coossify,  after  the  fashion  of  apes.  Either  a  vertical  or  a  trans- 
verse suture  may  be  found. 

THE  MALAR  BONE. 
This  bone2  forms  the  prominence  of  the  cheek,  the  outer  border  of  the  orbit, 
most  of  the  wall  separating  the  orbit  from  the  temporal  fossa,  and  completes  the 
zygomatic  arch.  For  simplicity  of  description  it  is  best  to  consider  it  a  diamond- 
shaped  bone,  with  an  outer  and  an  inner  surface,  four  angles,  four  borders,  and  one 
important  process,  the  orbital,  which  is  neither  an  angle  nor  a  border.  The  outer 
surface  presents  a  slight  prominence,  the  tuberosity?  a  little  below  the  middle.  The 
surface  is  nearly  smooth,  except  that  near  the  lower  border  there  is  often  a  certain 
roughness  extending  onto  the  zygomatic  process  for  the  origin  of  the  masseter  muscle. 
The  greater  part  of  the  inner  surface  is  smooth,  looking  towards  the  temporal  and 
zygomatic  fossae ;  but  a  rough  space  under  the  front  angle  joins  the  malar  process  of 
the  maxilla.  It  sometimes  helps  to  close  the  antrum,  in  which  case  a  part  of  it  is 
smooth,  being  lined  with  mucous  membrane.  The  superior  angle,  ox  frontal  process,*' 
joins  by  a  rough  surface  the  external  angular  process  of  the  frontal.  The  posterior 
angle,  or  zygomatic  process?  more  prominent  below  than  above,  joins  the  zygomatic 
process  of  the  temporal,  passing  below  it.  The  anterior  and  the  inferior  angles 
have  no  special  names.  The  postero-superior,  or  temporal  border,  is  at  first  vertical, 
becoming  horizontal  towards  the  hind  end.  Near  the  beginning  there  is  a  posterior 
projection,  the  marginal  process,  which  varies  considerably.  The  postero-inferior, 
or  masseteric  border,  slightly  irregular,  is  free,  forming  the  lower  edge  of  the  front  of 
the  zygoma.      The  antero-inferior,  or  maxillary  border,  is  slightly  concave.     It  articu- 

1  Ossa  nasalla.     -  Os  zygomaticum.     tuberositas  malaris.     4  Processus  frontospuenoidalis.     :>  Processus  temporalis. 


210  HUMAN   ANATOMY. 

lates  with  the  front  of  the  malar  process  of  the  maxilla,  bounding  externally  the 
rough  surface  of  the  inner  side  of  the  malar.  The  antero-superior,  or  orbital  border, 
is  smooth  and  concave,  forming  the  external  and  most  of  the  inferior  boundary  of 
the  orbit.  The  orbital  plate,  or  process,  which  forms  the  front  of  the  outer  wall  of 
the  orbit,  projects  inward  from  this  border,  joining  the  bone  at  nearly  a  right  angle. 


Tuberosity 
lar  bone,  outer  aspect. 


Temporal  canal 


It  is  narrow  in  front  and  broad  behind,  where  its  anterior  surface  looks  towards  the 
orbit  and  its  posterior  towards  the  temporal  fossa.  Its  projecting  edge  is  jagged 
throughout,  and  in  front  meets  the  superior  maxilla.  Behind  that  it  joins  the  outer 
border  of  the  great  wing  of  the  sphenoid,  and  above  articulates  with  the  frontal.  Be- 
tween the  part  meeting  the  maxilla  and  that  meeting  the  great  wing  there  is  usually  a 

short,  smooth  surface  bound- 
Fig.  240.  ing  the   end   of    the   spheno- 

,  Frontal  process  maxillary    fissure,    which    lies 

between  these  bones  in  the 
lower  outer  angle  of  the  orbit. 
Two  foramina  on  the  orbital 
surface  lead  to  minute  canals. 
The  lower,  the  malar,1  opens 
on  the  outer  surface  of  the 
bone ;  the  upper,  the  tem- 
poral,2 opens  on  the  back  of 
the  orbital  process.  They 
transmit  branches  from  the 
superior  maxillary  division  of 
the  fifth  nerve.  They  vary- 
greatly. 

In   all  mammals  the  pri- 
mary function  of  the  malar  is 
to  unite  the  maxilla  and  the 
temporal    bone.        Its    union 
Only  in  primates  does  it  join  the  sphe- 


Orbital  process 


Maxillary  surface 


Right  malar  bone,  inner  aspect 


with  the  frontal  is  a  further  development 

noid  and  separate  the  orbit  from  the  temporal  fossa 

Articulations. — The  malar  bone  articulates  with  the  frontal,  superior  maxillary, 
temporal,  and  sphenoid  bones. 

Development  and  Variations. — There  are  three  centres  of  ossification — an 


1  Foramen  zygomaticofacial 


zygooiaticotemporale. 


THE   INFERIOR   MAXILLA. 


anterior,  a  posterior,  and  an  inferior — appearing  towards  the  end  of  the  second  fcetal 
month.  They  fuse  in  the  course  of  the  third.  Sometimes,  but  very  rarely  in  the 
white  races,  the  bone  is  divided  by  a  fissure — as  in  some  apes — into  an  upper  and  a 
lower  part.  This  is  said  to  be  relatively  common  (seven  per  cent.)  in  the  Japanese. 
A  division  into  three  has  been  seen.  The  roughness  for  the  masseter  sometimes 
gives  a  deceptive  appearance  of  a  separate  piece  to  this  portion.  On  the  other  hand, 
an  occasional  slight  horizontal  cleft  in  the  zygomatic  process  is  probably  a  remnant 
of  a  division. 

THE   INFERIOR   MAXILLA. 

The  inferior  maxilla,1  mandible,  or  lower  jaw  develops  in  two  symmetrical 
halves,  which  soon  fuse.  The  bone,  as  a  whole,  consists  of  a  central  part — the  body 
— forming  the  chin  and  supporting  the  teeth,  and  two  rami  projecting  upward  from 
the  back  on  either  side  and  articulating  with  the  glenoid  fossa  of  the  temporal. 

The  body  is  convex  in  front  and  concave  behind.  The  line  of  junction  of  the 
original  halves  is  the  symphysis,  marked  by  a  slight  line.  There  is  a  forward  pro- 
jection of  the  lower  border  of  the  chin  which  is  a  human  characteristic.      A  short 

Fig.  241. 

Coronoid  process 
External  pterygoid 
CONDYLE 


.Incisor  fossa 
Levator  menti 


External  oblique  lin 

Platysma 
iferior  maxillary  bone,  outer  aspect. 


Mental  foramen 
Depressor  anguli  oris 


distance  from  the  median  line  at  the  lower  border  is  the  mental  tubercle'1,  bounding 
this  projection  laterally.  The  alveolar  process,  above  the  body,  is  of  the  same  nature 
as  that  of  the  upper  jaw.  A  slight  depression,  the  incisor  fossa,  is  found  below  the 
teeth  of  that  name  on  the  front  of  the  bone.  The  mental  foramen  for  the  terminal 
branches  of  the  inferior  dental  nerve  and  artery  is  rather  below  the  middle  of  the 
bone  under  the  second  bicuspid,  sometimes  just  before  it.  The  external  oblique 
li?ie,3  starting  from  the  mental  tubercle,  passes  below  the  mental  foramen  into  the 
front  edge  of  the  ramus.  Sometimes  it  seems  to  spring  from  the  lower  border  under 
the  molar  teeth,  and  sometimes  both  these  origins  may  be  present  at  once.  On  the 
lower  border  of  the  bone,  rather  to  its  inner  side,  there  is  a  rough  oval  behind  each 
mental  tubercle  for  the  anterior  belly  of  the  digastric  muscle.  The  inner  side  of  the 
body  is  in  the  main  smooth.  The  stiperiot  and  inferior  genial  tubercles*  are  two 
pairs  of  small,  sharp  spines  near  the  lower  part  of  the  inner  side  of  the  symphysis  for 
the  genio-glossi  and  genio-hyoid  muscles  respectively.  The  internal  oblique  line 
begins  at  first  very  indistinctly  near  the  genial  tubercles,  and  is  lost  on  the  inner 
side  of  the  ramus.      It  is  particularly  prominent  under  the  molars,  and  gives  attach- 


M:uidilnil;i.      -  I  ulnicuhiin  iticntalc. 


HUMAN   ANATOMY. 


ment  to  the  mylo-hyoid,  which  forms  the  muscular  partition  separating  the  oral 
cavity  from  the  superficial  region  under  the  chin.  There  is  a  faint  hollow,  the  sub- 
lingual fossa,  above  it,  below  the  incisors,  for  the  sublingual  gland  lying  beneath  the 
mucous  membrane,  and  a  deeper  one,  the  submaxillary  fossa,  for  the  submaxillary 
gland  below  the  line  near  the  junction  of  the  body  and  ramus. 

The  ramus,  which  joins  the  body  at  an  angle  of  from  110°  to  120°  in  the 
adult,  is  a  four-sided  plate  with  an  outer  and  an  inner  surface.  The  point  of  union 
of  the  posterior  and  inferior  borders  is  called  the  a?igle,  and  is  generally  turned  out- 
ward with  a  lip,  which  helps  to  form  the  under  part  of  the  masseteric  fossa,  on  its 
outer  side,  for  that  muscle.  When  well  marked,  it  represents  the  fossa  which  is  so 
striking  in  the  carnivora  and  some  other  orders.  The  fossa  is  not  always  present, 
the  muscle  being  then  inserted  into  a  roughness.  At  the  front  of  this  space  the 
lower  border  of  the  bone  is  often  grooved  by  the  facial  artery  crossing  it.  A  projec- 
tion, known  as  the  lemurine  process,  may  extend  from  the  angle  either  backward  or 
downward,  but  is  not  often  large.  The  lower  border  of  the  ramus,  where  it  joins 
the  body,  often  presents  a  concavity,  which  is  sometimes  very  marked,  giving  a 
peculiar  outline  ;  it  is  named  the  antegonium  by  Harrison  Allen.     There  is  a  rough- 


Fig.  242. 


Coronoid  process 


Sigmoid  notch 


Fossa  for  sublin- 
gual gland 
Sup. genial  tuber. 
(genio-glossus) 
Inf.  genial  tuber. 
{genio-hyoid) 


Mylo-hyoid 
groove 


Digastric  Mylo-hyoid 


Submaxillary  gland 
xillary  bone,  inner  aspect. 


ness  on  the  inner  side  of  the  ramus  at  the  angle  for  the  internal  pterygoid.  About 
on  a  line  with  the  free  edge  of  the  alveolar  process  is  the  lowest  point  of  the  inferior 
dental  foramen,1  an  opening  into  the  inferior  dental  canal  for  the  nerve  and  artery  to 
the  teeth  ;  the  foramen  is  guarded  in  front  by  a  sharp  point,  the  lingtcla.  A  faint 
groove  is  continued  from  this  opening  below  the  internal  oblique  line  for  the  mylo- 
hyoid vessels  and  nerve.  The  front  border  of  the  ramus  is  thick  below  and  narrow 
above,  where  it  becomes  the  coronoid  process,'1  pointing  upward  and  outward,  into 
which  the  temporal  muscle  is  inserted.  The  outer  border  of  the  thick  part  is  made 
by  the  external  oblique  line,  which  is  continued  into  the  thin  edge  above  ;  the  inner 
border  is  continued  from  the  inner  edge  of  the  alveolar  process,  or  sometimes  from 
the  internal  oblique  line.  It  ends  on  the  inner  surface  of  the  coronoid  process. 
The  posterior  border  of  the  ramus  slants  upward,  backward,  and  a  little  outward. 
It  is  rough  at  the  angle  and  smooth  above,  where  it  widens  to  form  the  back  of  the 
head  or  condyle}  This  presents  an  articular  surface  convex  from  before  backward 
and  higher  at  the  middle  than  at  the  ends.  The  longest  diameter  is  not  quite  trans- 
verse, for  the  axes,  if  prolonged,  would  meet  near  the  front  of  the  foramen  magnum. 
There  is  a  pretty  distinct  tubercle  at  the  outer  and  inner  ends.      The  condyle  has 

1  Foramen  mandibulars     -  Processus  coronoideus.     3  Capituluin  mandibulac. 


THE  INFERIOR  MAXILLA. 


'13 


the  appearance  of  being  set  rather  on  the  front  of  the  neck, '  which  is  merely  a 
constriction  below  the  head  ;  the  articular  surface,  however,  extends  at  least  as  far 
down  behind  as  in  front.  There  is  a  depression  for  a  part  of  the  insertion  of  the 
external  pterygoid  on  the  front  of  the  neck  internal  to  the  sigmoid  notch,2  which 
is  the  deep  depression  separating  the  coronoid  process  from  the  condyle.  The 
dental  canaP  sweeps  downward  and  forward  with  a  slight  curve,   and   then  runs 


Fig.  243. 


Fig.  244. 

Alveolar  process         Coronoid  process 


Condyle 


Section  through  body  of  lower 
jaw,  anterior  surface. 


Symphysis  Dental  canal 

Right  inferior  maxilla  at  about  birth,  inner  aspect. 


Fig.  245. 


horizontally  nearer  the  lower  than  the  upper  border  of  the  body  of  the  jaw.4  It 
lies  at  first  against  the  inner  wall,  but  soon  is  nearer  the  outer.  This  relation 
then  varies,  but  towards  the  anterior  end  of  its  course  it  is  against  the  inner  wall. 
It  divides  under  the  second  bicuspid  into  the  mental  canal,  some  five  millimetres 
long,  running  to  the  mental  foramen,  and  into  the  incisive  canal,  much  smaller,  for 
the  vessels  and  nerves  of  the  front  teeth,  which, 
after  dividing,  is  lost  in  the  cancellated  tissue  under 
the  lateral  incisor. 

Structure. — The  jaw  is  of  very  tough  bone, 
especially  at  the  symphysis,  where  it  is  almost  solid. 
On  section  the  body  shows  very  thick  walls  below, 
before,  and  behind.  The  alveolar  processes,  on  the 
contrary,  are  made  of  very  light  plates  that  are  ab- 
sorbed rapidly  after  the  loss  of  the  teeth. 

Development  and  Growth. — The  two  halves 
of  the  inferior  maxilla  are  formed  separately,  each 
from  six  centres.  They  are  at  first  connected  by 
ligament.  Even  before  birth  the  union  seems  very 
close,  but  they  become  coossified  only  in  the  course 
of  the  first  year.  The  centres  appear  from  the  sixth 
to  the  eighth  week  of  fcetal  life  in  the  membrane  of 
Meckel's  cartilage,  except  as  otherwise  mentioned. 
They  fuse  during  the   third    month.       The   centres 

are  :  (1)  the  dentary,  which  is  a  line  of  ossific  deposit  forming  the  lower  border 
and  the  front  of  the  alveolar  process  ;  (2)  one  in  the  distal  end  of  Meckel's  carti- 
lage, for  the  region  of  the  symphysis  ;  (3)  one  for  the  coronoid  ;  (4)  one  appearing 
in  cartilage,  not  that  of  Meckel,  for  the  condyle  and  top  of  the  ramus  ;  (5)  one  for 
the  angle  ;  (6)  the  splenial,  for  the  inner  alveolar  plate,  extending  back  to  include 
the  lingula.  This  one  appears  some  three  weeks  later  than  the  others.  Still 
another  minute  one  is  said  to  help  to  form  the  mental  foramen  (Rambaud  et 
Renault).  All  these,  except  that  for  the  condyle,  which  unites  at  fifteen,  fuse 
shortly  after  their  appearance.  The  mandible,  being  at  first  nothing  but  a  hollow 
bar  to  hold  tooth-sacs,  is  very  shallow.  The  ramus  is  small,  the  head  bent  back- 
ward and  the  angle  very  large.  At  birth  it  is  about  1400.  With  the  loss  of  teeth, 
from  whatever  cause,  the  alveolar  process  atrophies.  In  old  age  the  bone  is  very 
small  and  of  light  structure,  and  the  angle  enlarges  considerably,  so  as  to  mimic 
the  infantile  form. 

4Fawcett  :  Journal  of  Anatomy  and  Physiology,  vol.  xxix.,  1S95. 

1  Collun]  mandibular     =  lncisura  mandibular.     "'  Canalis  mandibular. 


Alveolar 
process 


Right  half  of  lower  jaw  at  about  birth, 


2I4 


HUMAN  ANATOMY. 


Intra-articular 
artilag< 


Fig.  246. 

Zygoma,  cut  surface 


External  pterygoid 


The  temporo-mandibular  ail 
opened. 


THE  TEMPORO-MANDIBULAR  ARTICULATION. 
This  is  a  compound  joint,  the  elements  of  which  are  the  socket,  the  condyle,  and 
the  meniscus,  an  intra-articular  disk  of  fibro-cartilage,  dividing  the  cavity  into  an 
upper  and  a  lower  part,  both  being  enclosed  by  one  capsular  membrane.     The  socket 

includes  the  glenoid  fossa  and  the  articular 
eminence  of  the  temporal  bone.  The  articu- 
lar coating  of  the  socket,  which  is  continued 
onto  the  front  of  the  articular  eminence,  is 
not  true  cartilage  (Langer),  though  resem- 
bling it  to  the  naked  eye.  The  socket  is 
bounded  behind  by  the  fissure  of  Glaser. 
The  tympanic  plate  behind  it  is  covered  by 
areolar  tissue  and  a  part  of  the  parotid  gland, 
which  extend  to  the  back  of  the  head  of  the 
jaw  and  make  the  socket  much  narrower  and 
deeper  than  it  seems  on  the  dry  bone.  The 
intra-articular  fibro-cartilage1  is  oblong  trans- 
versely with  rounded  angles.  It  rests  more 
on  the  front  of  the  condyle  than  on  the  top. 
It  is  concave  both  above  and  below,  being 
moulded  on  the  eminentia  articularis  and  on 
the  condyle.  It  may  be  merely  one  millimetre 
thick  in  the  middle,  and  is  said  to  be  some- 
times perforated.  The  thick  posterior  border 
fits  into  the  highest  part  of  the  socket.  The 
capsule,  lax  and  weak,  is  attached  to  the  borders  of  the  articular  surfaces  and  to  the 
edges  of  the  intra-articular  fibro-cartilage.  The  external  lateral  ligament"1  is  a  com- 
paratively strong  collection  of  fibres,  strengthening  the  capsule  externally.  The 
fibres  run  downward  and  back- 
ward from  the  tubercle  on  the 
zygoma,  at  the  outer  end  of  the 
articular  eminence,  to  the  outer 
side  of  the  neck  as  far  as  the 
hind  border.  The  effect  of  this 
insertion  is  to  place  the  trans- 
verse axis  of  rotation  of  the  jaw, 
not  in  the  head  of  the  mandible, 
but  in  the  neck.  The  capsule 
receives  at  the  front  and  inner 
side  two  bands  of  fibrous  tissue 
continuous  with  the  dura  mater, 
which  passes  through  the  fora- 
men ovale  around  the  third  di- 
vision of  the  fifth  nerve.3  The 
spkeno-mandibular  ligame?it,  * 
formerly  improperly  called  the 
internal  lateral,  is  a  weak  fibrous 
structure  originally  developed 
around  a  part  of  Meckel's  car- 
tilage. It  runs  from  the  spine 
of  the  sphenoid  to  the  lingula 
without  connection  with  the 
joint.       The    capsule   is  far   too 

loose  to  hold  the  jaw  firmly  in  place,  hence  it  is  supplemented  by  the  powerful 

muscles  of  mastication.      One  of  these,  the  external  pterygoid,  is  inserted  into  both 

the  head  of  the  lower  jaw  and  the  meniscus,  which  it  draws  forward,  being  incorpo- 

3Fawcett  :  Journal  of  Anatomy  and  Physiology,  vol.  xxvii.,  1893. 

1  Discus  articularis.     2  Lig.  temporomandibulare.        Lig.  sphcnomanditmlare. 


Fig.  247. 

External  lateral  ligament 


Styloid  proces: 


The  temporo-mandibular  articulation,  outer  aspect. 


THE   ARTICULATION    OF   THE    MANDIBLE. 


215 


Fig.  248. 


Capsule 


rated  with  the  front  of  the  capsule.  The  stylo-maxillary  ligament  is  a  bundle  of 
fibres  of  the  cervical  fascia  running  from  the  styloid  process  to  the  angle  of  the  jaw. 
Movements. — These  occur  on  both  sides  of  the  meniscus,  which  slides  for- 
ward and  backward  on  the  articular  eminence.  They  may  be  divided  into  those 
of  opening  and  closing  the  mouth  and  of  grinding  the  teeth.  In  the  former, 
as  the  mouth  begins  to  open,  the  meniscus  and 
the  head  of  the  jaw  move  forward,  the  condyle 
at  the  same  time  advancing  on  the  former  as 
the  lower  jaw  turns  on  a  transverse  axis  pass- 
ing through  the  neck  in  both  halves  of  the  jaw. 
This  continues  as  the  mouth  opens  wider,  the 
meniscus  descending  onto  the  articular  eminence, 
and  probably,  when  the  movement  is  extreme, 
rising  a  little  on  the  other  side.  This  has  been 
graphically  demonstrated  on  the  living  by  an 
apparatus  bearing  luminous  points  at  the  sym- 
physis, the  condyle,  and  the  angle  of  the  jaw, 
which  were  photographed  as  the  mouth  opened 
to  various  widths.1  It  was  shown  that  the  for- 
ward movement  of  the  meniscus  occurs  even  in 
a  very  slight  opening  of  the  mouth.  The  angle 
of  the  jaw  moves  forward  at  the  very  beginning 
of  the  act,  but  soon  passes  backward.  The 
point  on  it  describes  some  very  complex  curves. 
Grinding  movements,  in  which  the  mouth  is  not 
opened,  must  occur  chiefly  between  the  skull  and 
the  meniscus  ;  just  what  occurs  below  the  latter 
is  uncertain.  The  lower  jaw  can  be  thrust  for- 
ward evenly,  as  the  meniscus  of  each  side  de- 
scends onto  the  articular  eminence  ;  but  in  ordinary  motions  it  seems  to  advance 
on  one  side  and  perhaps  to  recede  on  the  other.  Spee 2  has  shown  that  the  opposed 
crowns  of  the  molars  (and  apparently  of  the  premolars  also)  fall  on  the  arc  of  a  cir- 
cle that  touches  the  front  of  the  condyle,  drawn,  when  projected  on  a  plane,  from  a 
centre  on  the  crest  of  the  lachrymal  bone.  This  allows  the  teeth  of  the  lower  jaw  to 
slide  on  those  of  the  upper,  which  the  joint  would  not  allow  were  the  line  between 

the  teeth  a  straight  one.  To  this  may  be  added 
that  the  inferior  incisors  rest  against  the  lingual 
surfaces  of  the  superior,  and  that  the  tendency 
of  the  edges  of  the  former  to  make  a  transverse 
arch,  increased  by  the  wearing  away  of  the  outer 
corners  of  the  lower  lateral  incisors,  implies  an 
alternate  rising  and  falling  of  either  side  of  the 
jaw  in  grinding  movements  with  the  mouth  closed, 
though  the  axis,  in  the  main  antero-posterior,  can- 
not be  a  fixed  one.  It  must  be  remembered  in 
this  connection  and  in  the  mechanics  of  the  jaw 
throughout  that  the  range  of  variations  is  great, 
and  that  there  is  frequently  a  want  of  symmetry 
in  the  joints.  This  want  of  precise  working  is  in- 
creased by  the  laxity  of  the  ligaments  and  the  num- 
ber of  muscles  acting  on  various  parts  of  the  jaw. 
Development. — The  tympanic  portion  of 
the  temporal  being  at  birth  nothing  but  the  ring, 
it  is  evident  that  the  joint  belongs  solely  to  the  squamous  portion,  and  is  always 
bounded  by  the  fissure  of  Glaser.  At  this  age  the  glenoid  fossa  is  nearly  flat  and 
the  eminentia  articularis  but  slightly  raised.  Even  after  birth  the  joint  below  the 
meniscus  is  very  slight,  so  that  but  little  motion  can  occur  in  it,  while  the  meniscus 

1  Luce  :  Boston  Medical  and  Surgical  Journal,  July  4,  1889. 
s  Arch,  fur  Anat.  und  Phys.,  Anat.  Abtheil.,  1890. 


2l6 


HUMAN    ANATOMY. 


itself  can  play  freely  on  the  flat  glenoid.      The  socket  gradually  deepens,  and  as- 
sumes something  like  its  definite  shape  apparently  in  the  course  of  the  third  year. 

THE  HYOID  BONE. 
This  is  a  U-shaped  bone  l  not  in  contact  with  any  other,  situated  below  the  jaw 
and  above  the  larynx,  with  which  its  physiological  relation  is  intimate.  It  gives 
origin  to  a  large  part  of  the  muscular  fibres  forming  the  tongue.  It  consists  of  a 
central  body,  elongated  transversely,  and  of  a  pair  of  greater  and  lesser  horns:  The 
convex  anterior  surface  of  the  body  looks  forward  and  upward  ;  the  posterior  surface, 
which  is  deeply  hollowed,  faces  in  the  opposite  direction.  The  front  surface  is  divided 
by  a  median  and  a  transverse  ridge  into  four  spaces,  of  which  the  upper  are  the 
larger.      The  greater  cornua  extend  with  a  curve  backward  and  a  little  upward. 

They  are  broadest  at  their  front,  and 
Fig.  250.  as  they  pass  backward  are  somewhat 

twisted,    so    that    the    upper   surface 
comes  to  look  outward.    Each  ends  in  a 
small  knob.     They  are  connected  with 
itcornu     the  body  sometimes  by  fibro-cartilage, 
occasionally  by  a  synovial  joint.     The 
lesser  cornua,  slender  processes  some 
five  millimetres  long,  are  the  bony  ter- 
minations of  the  stylo-hyoid  ligaments. 
There  is  usually  a  synovial  joint  be- 
ll comu     tween  them  and  the  body,  which  they 
join  at  the  ends  of  the  upper  border. 
They  may  be  connected  by  ligament, 
and  are  not  very  rarely  wanting,  which 
simply  means  that  ossification  has  not 
occurred   at   the   lower   ends   of    the 
stylo-hyoid    ligaments.       The  outline 
of  the  body  and  greater  horns  is  easily  felt  from  the  surface,  and  the  whole  bone 
can  be  grasped  and  moved  from  side  to  side. 

Development. — As  embryology  shows,  the  basihyoid,  or  body,  is  connected 
with  the  second  visceral  arch  through  the  stylo-hyoid  ligaments,  the  lower  ends  of 
which  become  the  lesser  horns,  or  cerato-hyoids,  and  with  the  third  arch  by  the 
greater  horns,  the  thyro-hyoids.  The  bone  ossifies  in  cartilage,  two  nuclei  appearing 
(according  to  Sutton)  in  the  fourth  fcetal  month,  one  on  each  side  of  the  median 
line,  and  speedily  fusing.  A  nucleus  appears  in  each  greater  horn  in  the  fifth  month. 
Statements  as  to  the  time  of  appearance  of  ossification  in  the  lesser  horns  vary  from 
a  few  months  after  birth  to  the  end  of  adolescence.  The  latter  is  probably  nearer 
the  truth.  The  greater  horns  rarely  coossify  with  the  body  before  forty-five,  but 
after  that  age  not  infrequently.  Indeed,  in  old  age  they  are  generally  joined.  The 
lesser  horns  are  rarely  consolidated  before  advanced  age. 


The  hyoid  bone  from  in  front. 


THE   SKULL  AS   A  WHOLE. 

In  connection  with  the  description  of  the  skull  as  a  whole,  which  is  not  intended 
to  recapitulate  the  points  already  mentioned,  but  to  discuss  the  general  features, 
especially  those  resulting  from  the  apposition  of  the  distinct  parts,  let  it  be  remem- 
bered that  the  skull  is  an  egg-shaped  structure,  and  that  the  face  is  placed  under  its 
anterior  and  middle  fossse. 

The  Cranial  Sutures. — There  are  three  antero-posterior  sutures,  a  median 
and  a  lateral  one  on  each  side,  and  two  transverse  ones.  The  median  antero- 
posterior suture  is  the  sagittal ; 2  it  lies  between  the  parietal  bones,  and  is  jagged, 
except  at  the  posterior  part,  which  is  usually  straight.  Occasionally  the  metopic 
suture*  persists  between  the  original  halves  of  the  frontal  bone.  It  is  rarely  in  direct 
continuation  with  the  sagittal.  The  coronal  suture*  crosses  the  top  of  the  head,  sep- 
arating the  frontal  from  the  parietals.      It  ends  at  the  top  of\the  great  wing  of  the 

1  Os  byoideum.     -  Sutura  sagittalis.     3  S.  frontalis.     4  S.  coronalis.  ^ 


THE    SKULL    AS    A    WHOLE. 


217 


sphenoid  below.  Its  termination  is  at  a  vague  region  where  several  sutures  approach 
one  another,  called  the  ptcrion.  In  the  lower  races  occasionally,  but  rarely  in  the 
higher,  the  lower  end  of  the  coronal  is  continuous  with  the  suture  between  the  squa- 
mosal and  the  great  wing,  in  which  case  two  sutures  cross  each  other  at  right  angles, 
and  the  pterion  is  a  definite  point,  an  ape-like  feature.  If  the  lower  corner  of  the 
parietal  bone  is  carried  downward,  and  the  suture  between  the  great  wing  and  the 
lower  border  of  the  frontal  falls  considerably,  the  general  plan  is  that  of  an  H,  the 
cross-piece  being  the  suture  between  the  parietal  and  the  sphenoid  ;  but  the  H  is 
not  often  very  clear.      A  separate  bone,  the  epiptcric,  is  occasionally  found  in  this 

Fig.  251. 


Supra-orbital  foramen 


Exter.  angular  process 


Lesser  wing  of  spl: 

Optic  foramen 
Great  wing  of  sphen 

Lachrymal  ^r<" 


Malar 
Superior  maxillary. 


Infra-orbital  fora 

Middle  turbinate 

Nasal  septum 

Inferior  turbinate 

Anterior  nasal  spine 

Styloid  process 


'orrugator  supercilit 


■Orbicular 
palpebrc 


Tendo  ocu 
Orbicular 
palpebr 
■Levator  labii  superioris 

alceque  nasi 
•Levator  labii  superioris 

Zygomaticus  major 
Zygomaticus  minor 
■Masseter 

evator  anguli  oris 
Compressor  nan's 
or  ata1  nasi 
Buccinator 


Mental  foramen 


Depressor  labii  inferioris 
Depressor  atiguli  oris 
Platy 


The  skull  from  in  front. 


region.  (See  under  Growth  and  Age  of  the  Skull.)  The  lambdoidal  suturex  starts 
from  the  top  of  the  mastoid  on  each  side  to  run  upward  and  backward  to  a  point 
separating  the  occipital  from  the  parietals,  the  interlocking  teeth  being  very  long. 
What  is  practically  a  continuation  of  this  suture  runs  downward  between  the  oc- 
cipital and  the  mastoid.  Wormian  bones  are  often  found,  and  sometimes  in  great 
numbers,  in  the  lambdoidal  suture.  Sometimes  there  is  a  very  large  triangular  one 
occupying  the  place  of  the  upper  part  of  the  occipital.  Such  a  one  may  be  sub- 
divided. We  incline  to' consider  it  a  Wormian  bone  rather  than  a  representative  of 
the  interparietal 


2l8 


HUMAN    ANATOMY. 


The  lateral  antero-posterior  suture  begins  at  the  root  of  the  nose  and  runs 
through  the  orbit  to  the  side  of  the  head,  ending  at  the  lambdoidal.  Its  various 
parts  are  named  from  the  adjacent  bones.  Thus,  it  begins  with  the  fronto-nasal,  to 
continue  between  the  frontal  and  the  following  bones  :  the  superior  maxilla,  the 
lachrymal,  the  os  planum  of  the  ethmoid,  the  body,  the  lesser  and  greater  wings  of 
the  sphenoid,  the  malar,  and  in  the  temporal  fossa  the  great  wing  of  the  sphenoid 
again.  Then  behind  the  coronal  it  runs  between  the  parietal  above  and  the  sphenoid 
and  temporal  below. 


Fig.  252. 


Inferior  temporal  line 


Coronal  suture 


Sup.  temporal  line 


The  skull  from  the  side. 


THE  EXTERIOR  OF  THE  CRANIUM. 

Superior  Aspect.1 — This  is  oval  and  broader  behind  than  in  front,  showing 
the  coronal,  sagittal,  and  the  top  of  the  lambdoidal  sature.  On  either  side  is  the 
parietal  eminence,  and  in  front  the  smaller  frontal  ones.  The  superior,  and  perhaps 
a  little  of  the  inferior,  curved  lines  appear  laterally.      It  is  rarely  quite  symmetrical. 

Posterior  Aspect.2 — This  is  circular  in  outline,  or  sometimes  five-sided,  having 
an  inferior,  two  lateral  (nearly  vertical),  and  two  oblique  superior  borders.  Below 
the  middle  is  the  external  occipital  protuberance ;  which  is  beneath  the  most  posterior 
point  of  the  skull. 

Lateral  Aspect.3 — This  shows  nothing  of  the  face  that  has  not  been  mentioned. 
The  zygomatic  arch  is  prominent,  bridging  over  a  deep  hollow.  The  part  of  the 
hollow  above  the  arch  is  the  temporal  fossa,  deepest  in  front,  and  nearly  filled  by  the 
temporal  muscle.  The  inner  wall  is  formed  by  the  squamosal  and  the  great  wing  of 
the  sphenoid  ;  the  front  one  chiefly  by  the  orbital  plate  of  the  malar.  The  infra- 
temporal crest  on  the  great  wing  separates  the  temporal  fossa  from  the  zygomatic  fossa 
below.      (The  latter  fossa  is  described  with  the  face,  page  227.)     The  two  tanpoi-al 

1  Norma  verticalis.     -  Norma  occipitalis.     3  Norma  lateralis. 


THE  EXTERIOR  OF  THE  CRANIUM. 


219 


lines  are  to  be  seen  in  whole  or  in  part.  The  inferior  always  ends  in  the  supra- 
mastoid  ridge.      The  mastoid  process  varies  much  in  development. 

Anterior  Aspect.1 — The  cranial  portion  of  the  skull  is  seen  only  above  the 
orbits  and  the  root  of  the  nose.  Much  of  its  lower  part  is  occupied  by  the  frontal 
sinuses. 

Inferior  Aspect.2 — (The  lower  jaw  is  supposed  to  be  removed.)  This  aspect 
may  be  divided  into  three  regions  by  two  cross-lines,  one  being  at  the  roots  of 
the  pterygoid  plates  and  one  at  the  front  edge  of  the  foramen  magnum.  Passing 
from  behind  forward,  near  the  posterior  surface,  are  seen  the  external  occipital  pro- 

Fig.  253. 

Anterior  palatii 


Posterior  palatine  canal 


Posterior  nares 


Foramen  ovaie 
Eminentia 

articularis 
Middle  lacerated 

foramen 

spino- 


Glenoid  fossa 
Fissure  of  Glaser 


Parietal  bone> 


Posterior  condyloid  foramen 


Superior  curved  lii 
jaw  removed. 

tuberance  and  the  superior  and  inferior  curved  lines.  In  front  of  the  latter  the 
occipital  bone  is  convex  to  the  outer  side  of  the  foramen  magnum.  A  line  con- 
necting the  backs  of  the  condyles  halves  the  foramen  magnum.  The  mastoid  pro- 
cesses appear  laterally.  Internal  to  them  are  the  digastric  grooves,  and  just  internal 
to  these  the  occipital  grooves,  nearly  or  quite  in  the  suture.  Between  the  mastoid 
and  styloid  processes  is  the  stylo-mastoid  foramen.  The  region  between  the  two 
above-mentioned  lines  includes  the  guttural  fossa  in  the  middle  for  the  pharynx  ; 
on  each  side  of  this  are  openings  for  great  vessels  and  nerves,  and,  externally,  the 
joint  of  the  jaw.      The  basilar  process  in  front  of  the  foramen  magnum  forms  the 


220  HUMAN   ANATOMY. 

roof  of  the  pharynx.  On  either  side  of  it  is  a  rent  separating  it  from  the  temporal 
bone.  The  back  of  this  rent  is  the  jugular  forame?i ;  then  comes  thefssure  proper  ; 
and,  at  the  apex  of  the  petrous  portion,  the  middle  lacerated  foramen,  which  in  life  is 
filled  with  cartilage,  as  is  also  the  fissure.  Outside,  in  the  petrous  bone,  is  the 
carotid  opening,  internal  to  the  tympanic  plate,  which  is  separated  by  the  fissure  of 
Glaser  from  the  glenoid  fossa.  The  outer  border  of  the  petrous  forms  a  gutter 
with  the  great  wing  of  the  sphenoid  for  the  cartilaginous  part  of  the  Eustachian 
tube.  Just  outside  of  this  is  the  foramen  spinosum,  often  in  the  suture  between 
the  sphenoid  and  temporal,  and  before  it  the  foramen  ovale.  In  the  front  part  of  the 
base  outside  of  the  pterygoid  is  that  part  of  the  great  wing  which  looks  downward, 
overhanging  the  zygomatic  fossa. 

THE   INTERIOR   OF   THE   CRANIUM. 

The  vault1  of  the  cranium  has  the  groove  for  the  superior  longitudinal  sinus 
in  the  middle,  with  Pacchionian  depressions  on  each  side  of  it.  The  grooves  for  the 
middle  meningeal  artery  cover  the  parietal  region.  The  base  of  the  cranium  is 
divided  into  three  fossa?, — the  anterior,  the  middle,  and  the  posterior.  ■ 

The  anterior  fossa2  is  bounded  behind  by  the  line  in  front  of  the  olivary  emi- 
nence and  by  the  edge  of  the  lesser  wings  of  the  sphenoid.  It  has  a  deep  hollow 
over  the  nasal  cavity,  the  floor  of  the  depression  being  the  cribriform  plate  of  the 
ethmoid.  In  the  median  line  are  the  crista  galli  and  the  foramen  caecum.  The 
lateral  part  of  the  anterior  fossa  slants  downward,  inward,  and  backward,  and  is  quite 
smooth  in  the  middle  behind  the  hollow. 

The  middle  fossa  3  is  limited  in  the  centre  to  the  sella  turcica,  but  expands  at 
the  sides.  It  is  separated  from  the  posterior  fossa  by  the  dorsum  settee  and  the 
superior  border  of  the  petrous.  The  middle  fossa  has  the  olivary  eminence  and  the 
optic  foramina  in  front  of  the  sella  turcica,  at  each  side  of  which  is  the  g?roove  for  the 
internal  carotid  artery  and  the  cavernous  sinus.  The  clinoid  processes  tend  to  meet 
above  its  sides,  and  sometimes  do  so,  especially  when  the  middle  clinoid  is  developed. 
On  the  anterior  border  of  the  fossa,  near  the  middle,  is  the  sphenoidal  fissure  opening 
into  the  orbit.  Just  behind  its  inner  end  is  the  foramen  rotundum  ;  farther  back  and 
outward  are  the  foramen  ovale  and  foramen  spinosum,  from  which  latter  start  the 
grooves  of  the  middle  meningeal  artery  ;  more  internal  lies  the  middle  lacerated 
foramen.  The  depression  for  the  Gasserian  ganglion  is  seen  at  the  apex  of  the 
anterior  surface  of  the  petrous  portion  of  the  temporal  bone  ;  the  ganglion  is  very 
conveniently  placed  for  its  ophthalmic,  superior  maxillary,  and  mandibular  branches 
to  reach  the  sphenoidal  fissure,  the  foramen  rotundum,  and  the  foramen  ovale  re- 
spectively. 

The  posterior  fossa4  is  much  the  larger.  In  the  middle  is  the.  foramen  mag- 
num, with  the  basilar  groove  before  it.  The  impression  for  the  superior  petrosal 
si?ius  is  at  the  top  of  the  petrous.  The  i?iferior  petrosal  simis  lies  on  the  suture 
between  the  petrous  bone  and  basilar  process.  The  internal  auditory  meatus,  the 
jugular  foramen,  and  the  anterior  condyloid  foramen  are  very  nearly  in  a  vertical 
line.  The  impressions  for  the  lateral  sinuses  run  outward  from  the  internal  occipital 
protuberance  until  they  suddenly  turn  downward,  making  a  deep  groove  in  the  tem- 
poral bone.  The  course  of  the  second  portion  of  the  sinus  is  straight  downward 
and  inward,  the  highest  point  of  the  sinus  corresponding  with  the  supramastoid  crest 
above  the  middle  of  the  mastoid  process.  This  point  is  sometimes  so  near  to  the 
surface  that  the  bone  is  translucent.  In  its  descent  the  sinus  may  for  a  time  keep 
near  the  surface,  or  leave  it  at  once.  There  is  much  variation  in  many  respects  ; 
sometimes  the  downward  turn  of  the  sinus  is  less  sharp.  The  claim  that  anything 
can  be  predicated  of  this  from  the  shape  of  the  head  is  extremely  uncertain.  Just 
before  reaching  the  jugular  foramen  the  sinus  once  more  changes  its  direction, 
running  forward  and  upward. 

THE   ARCHITECTURE   OF   THE   CRANIUM. 
The  curved  vault  of  the  skull  is  well  adapted  to  break  shocks,  but  the  base 
is  much  weaker  ;  not  only  is  the  bone  thin  in  many  places,  but  it  is  interrupted  by 


THE   ARCHITECTURE   OF   THE   CRANIUM.  221 

many  openings.  The  whole  of  the  anterior  fossa  is  very  thin  ;  so  is  the  sella  turcica, 
being  just  over  the  sphenoidal  sinus.  A  chain  of  openings  crosses  the  middle  fossa 
on  either  side.  The  temporal  bone  is  practically  crossed  by  the  external  and  internal 
meatuses  and  the  middle  ear,  besides  containing  other  cavities.  Thus  the  petrous 
is  brittle,  although  the  bone  is  very  dense.  A  rim  of  comparatively  firm  bone 
extends  around  two-thirds  of  the  skull,  starting  on  each  side  from  the  occipital 
protuberance,  which  may  be  even  two  centimetres  in  thickness,  along  the  line  of  the 
lateral  sinus  to  the  supramastoid  ridge  ;  it  follows  the  line  of  origin  of  the  zygoma, 


Ethmoidal  spine 


Fig.  254. 

Foramen  caecum 
Crista  efalli  ~.       ,  ,    . 

Frontal  sinus 


Cribriform  plate 


Optic  foramen 

Sella  turcica 


Torcular  Herophili 


Base  of  skull  from  abovt 


and  ends  in  the  infratemporal  crest  on  the  great  wing  of  the  sphenoid.  A 
median  ridge  strengthens  the  skull  in  both  the  frontal  and  occipital  regions. 
The  average  thickness  of  the  vault  is  about  four  millimetres.  It  is  thick  through- 
out the  frontal  region  and  at  the  parietal  eminences,  a  thin  area  lying  behind  and 
below  the  latter.  The  Pacchionian  depressions  may  almost  perforate  the  skull.  It 
is  very  thin  in  the  squamous  part  of  the  temporal  ;  less  so  in  the  superior  occipital 
fossae. 

If  the  base  of  a  skull  be  held  to  the  light  and  examined  from  within,   the 


222  HUMAN   ANATOMY. 

translucency  of  the  following  parts  will  be  very  evident  :  the  roofs  of  the  orbits,  one 
or  two  uncertain  points  in  the  great  wing  of  the  sphenoid,  one  in  the  lower  part  of 
the  squamous  portion  just  outside  of  the  petro-squamous  suture  corresponding  to 
the  glenoid  fossa,  the  beginning  of  the  basilar  process,  a  varying  portion  of  the 
descending  part  of  the  groove  for  the  lateral  sinus,  and  nearly  the  whole  of  the  floor 
of  the  cerebellar  fossa.  A  little  rim  of  firm  bone  surrounds  the  foramen  magnum 
except  in  front. 

THE    FACE. 

This  consists  essentially  of  the  framework  of  the  jaws  and  of  the  orbital  and 
nasal  cavities,  as  well  as  of  certain  accessory  regions,  the  zygomatic  and  spheno- 
maxillary fossa.  Apart  from  features  in  the  bones  already  described,  the  front 
view  shows  the  outline  of  the  orbits,  of  the  nasal  opening,  of  the  prominence  of  the 
cheek,  and  of  a  vacant  space  left  between  the  upper  jaw  and  the  ramus  of  the  lower. 
The  foramina  for  the  escape  of  the  terminal  branches  of  the  three  divisions  of  the 
fifth  nerve  are  very  nearly  in  a  vertical  line,  only  the  mental  forameyi  is  usually  a 
little  lateral.  The  side  view  shows  the  zygomatic  fossa  below  the  arch  and  within 
the  ramus. 

The  Orbit. — Although  the  base  is  quadrilateral,  the  orbital  cavity  is  conical 
rather  than  pyramidal,  since  its  section  a  little  behind  the  base  is  almost  circular. 
The  upper  margin  of  the  entrance  is  formed  by  the  frontal  bone,  which  slants  down- 
ward to  the  very  prominent  external  angular  process,  which  affords  great  protection 
to  the  eye.  The  suture  with  the  malar  can  easily  be  felt  in  life, owing  to  the  greater 
projection  of  the  upper  bone.  The  outer  border  and  the  inner  half  of  the  lower  are 
made  by  the  malar,  which  has  a  sharp  orbital  edge  throughout.  This  is  continued 
by  an  ascending  sharp  edge  of  the  superior  maxillary  into  the  front  border  of  the 
lachrymal  canal,  at  the  top  of  which  it  becomes  indistinct.  This  is  to  be  considered 
the  i?iner  boundary  ;  but  there  is  difficulty  in  accurately  determining  this  border,  for 
if  the  upper  border  be  followed  down  at  the  inner  side,  it  will  be  seen  to  run  to  the 
posterior  edge  of  the  lachrymal  groove  made  by  the  ridge  in  the  lachrymal  bone.  In 
some  skulls  this  is  much  the  more  evident  border.  The  upper  part  of  the  inner  border 
is  the  only  one  that  cannot  easily  be  felt  in  life.  The  roof  of  the  orbit  is  arched  from 
side  to  side  and  from  before  backward.  It  is  overhung  by  the  border,  especially  at 
the  outer  angle,  where  it  lodges  the  lachrymal  gland.  The  inner  wall,  composed  of 
part  of  the  ascending  process  of  the  maxilla,  the  lachrymal,  the  os  planum  of  the  eth- 
moid, and  part  of  the  body  of  the  sphenoid,  is  nearly  vertical  in  front,  but  farther 
back  slants  inward.  The  inner  wall  is  frequently  quite  convex  in  the  middle  ;  if  this 
condition  is  marked,  it  is  probably  pathological.  There  is  an  approach  to  an  angle 
between  this  surface  and  the  upper.  The  two  ethmoidal  foramina  are  found  above 
the  os  planum.  The  inner  wall  curves  gradually  into  the  inferior  surface,  formed 
by  the  maxilla,  and  presenting  the  infra-orbital  groove  and  canal.  The  outer  wall 
slants  strongly  inward,  its  lower  border  being  internal  to  the  upper.  It  is  formed 
by  the  malar  bone  in  front  and  the  great  wing  of  the  sphenoid  behind.  The  back 
part  of  the  upper  angle  of  the  outer  wall  is  occupied  by  the  spkenoidal  fissure,  which 
opens  into  the  middle  fossa  of  the  skull,  and  the  lower  angle  by  the  spheno-maxillary 
fissure,  separating  the  wing  of  the  sphenoid  from  the  maxilla  ;  the  outer  end  of  this 
fissure,  closed  by  the  malar  bone,  opens  into  the  zygomatic  fossa.  The  optic  fora- 
men is  at  the  posterior  point  of  junction  of  the  roof  and  the  inner  wall.  The  apex 
of  the  orbit  is  at  the  inner  end  of  the  sphenoidal  fissure. 

The  axes  of  the  orbits,  if  prolonged,  cross  each  other  at  the  back  of  the  sella 
turcica  at  an  angle  of  from  420  to  440.  The  orbital  axis  is,  therefore,  very  differ- 
ent from  the  visual  axis,  which  is  antero-posterior.  The  former,  moreover,  runs 
downward  from  the  apex  to  the  base,  making  an  angle  of  from  150  to  200  with  the 
horizontal  plane. 

The  dimensions  of  the  adult  orbit  vary  with  different  observers  and,  no  doubt, 
in  different  localities.  The  depth  is  from  forty  to  forty-five  millimetres,  the  breadth 
at  the  base  is  about  forty  millimetres,  and  the  height  about  thirty-five  millimetres 
in  males.      In  females  the  dimensions  are  rather  less. 

The  roof  is  thin  and  separates  the  orbit  from  the  cranial  cavity,   except  in 


THE   NASAL    CAVITY. 


223 


front,  at  the  inner  side,  where  the  frontal  sinus  intervenes.  This  sinus  extends 
downward,  mesially,  almost  to  the  top  of  the  lachrymal  groove.  The  inner  and 
lower  walls,  separating  the  orbit  from  the  nasal  cavity  and  the  antrum  respectively, 
are  very  thin  and  offer  little  resistance  to  a  tumor  or  a  foreign  body.  The  great 
wing  of  the  sphenoid  in  the  outer  wall  is  thick,  except  just  at  the  edge  of  the 
sphenoidal  fissure  ;  it  separates  the  orbit  from  the  middle  cranial  fossa.  The  outer 
wall  just  behind  the  anterior  border  is  thin,  where  it  cuts  off  union  with  the 
temporal  fossa. 

The  Nasal  Cavity. — The  nasal  cavity  of  each  side  has  an  anterior  and  a  pos- 
terior opening,  a  roof,  a  floor,  an  outer  wall,  and  an  inner,  the  septum,  which,  when 

Fig.  255. 


Floor  of  nasal  fossae 
Front  section  of  skull  through  pi; 


Inferior  meatus 


.the  cartilage  is  present,  completely  separates  it  from  its  fellow.  The  anterior 
common  opening  of  the  two  cavities  is  shaped  like  an  inverted  ace  of  hearts, 
bounded  above  by  the  border  of  the  nasal  bones  and  elsewhere  by  the  superior 
maxillee.  In  the  middle  of  the  floor  of  the  opening  is  the  ante7ior  nasal  spine, 
resembling  closely  the  bow  of  a  boat.  The  anterior  edge  where  the  two  bones  meet 
is  the  cutwater,  and  above  is  a  triangular  surface,  the  deck,  bounded  by  a  sharp 
line,  which  runs  outward,  forming  the  lower  border  of  the  opening.  In  the  adult 
this  line  is  usually  continuous  with  the  lateral  border  of  the  opening,  but  in  infants' 
skulls  the  line  passes  from  the  side  onto  the  anterior  surface  of  the  maxillary  bone. 
Another  line  a  little  behind  this,  starting  inside  the  nose  at  the  front  of  the  inferior 
turbinate  crest,  runs  close  to  the  line  from  the  spine.     Though  these  lines  are  usually 


224 


HUMAN   ANATOMY. 


fused  in  the  adult,  forming  a  rather  dull  inferior  border  continuous  with  the  lateral 
sharp  one,  they  may  remain  distinct  and  enclose  a  well-marked  fossa  on  the  face  just 
below  the  nasal  opening  ;  this  is  the  fossa  prcsnasalis,  rarely  seen  in  other  than  low 
races.  Variations  in  the  arrangement  of  these  lines  may  occur,  and  according  to 
Zuckerkandl,'-  the  line  from  the  border  of  the  nose  may  not  always  form  the  anterior 
border  of  the  fossa.  The  combined  nasal  openings,  though  in  the  main  triangular, 
may  be  roughly  quadrilateral.  More  or  less  asymmetry  is  the  rule.  The  nasal  bones 
and  the  nasal  spine  may  point  sideways,  but  not  necessarily  to  the  same  side.  The 
spine  points  to  the  side  on  which  the  opening  is  the  wider  ;  the  broader  aperture 
usually  does  not  descend  so  low  as  the  narrower  one.  The  tip  of  the  nose  is  more 
often  turned  to  the  right.  In  life  the  shape  of  the  nose  depends  quite  as  much  on 
the  soft  parts  as  on  the  bones. 

The  posterior  openings  of  the  nares,  the  choance,  are  remarkably  symmet- 
rical ;  bounded  above  by  the  wings  of  the  vomer,  which  conceal  the  body  of  the 
sphenoid,  on  the  sides  by  the  internal  pterygoid  plates,  internally  by  the  vomer, 
and  below  by  the  horizontal  plate  of  the  palate,  each  is  much  higher  than  broad. 
The  index  of  the  choanse,  showing  the  proportion  of  the  breadth  to  the  height 
(I0°  heio'ht'  *  )'  *s  ^°  f°r  men  anc^  ^4  f°r  women>  showing  relatively  lower  openings  in 
the  latter  (Escat).      Measuring  the  combined  breadth  from  one  pterygoid  process 

to  the  other  at  the  hard  palate  on 
Fig.  256.  ten  adult  skulls  irrespective  of  sex, 

Piobein  infundibuium  we  found  the  average  breadth  27.7 

centimetres  and  the  average  height 
28.4  centimetres.  The  extremes 
were  24  and  31  centimetres  for  the 
breadth  and  25  and  31  for  the 
height.2  The  inclination  of  the 
posterior  border  of  the  vomer  is  in 
a  general  direct  ratio  to  the  degree 
of  prognathism,3  or  the  forward 
projection  of  the  face. 

Each  nasal  chamber  (Figs. 
255,  256)  is  very  narrow,  and 
much  higher  in  the  middle  than 
at  either  orifice.  The  front  part, 
the  vestibule,  extends  under  the 
bridge  of  the  nose.  The  roof  is 
extremely  narrow  except  at  the 
posterior  end.  It  is  composed  of 
the  nasal  bones,  thin  below,  thick 
;  of  a  small  part  of  the  frontal,  a  thin  plate  separating  it  from  the  frontal 
sinus  ;  the  very  thin  cribriform  plate,  easily  broken  ;  the  vertical  anterior  surface 
of  the  sphenoid,  pierced  by  an  opening  into  the  sinus  ;  and,  finally,  the  wing  of  the 
vomer.  The  floor  is  a  smooth  gutter,  formed  by  the  palatal  processes  of  the  maxilla 
and  palate  bones.  The  lower  border  of  the  anterior  nasal  opening  is  higher  than 
the  floor,  so  that  an  instrument  has  to  be  tilted  over  it. 

The  anterior  palatine  canal  opens  through  the  floor  near  the  front  on  either 
side  of  the  septum.  The  floor,  except  at  the  posterior  part,  is  of  strong  bone,  and 
is  smooth  all  over.  The  median  wall  is  derived  from  a  plate  of  cartilage,  developed 
at  a  very  early  period,  from  which  the  vertical  plate  of  the  ethmoid  and  the  vomer 
are  also  formed.  A  large  quadrilateral  space  is  left  vacant  in  the  macerated  skeleton, 
which  in  life  is  filled  by  the  unossified  portion  of  the  original  plate,  known  as  the 
triangular  cartilage.  Apparently  the  process  of  ossification  is  excessive  along  the 
line  of  union  between  the  ethmoid  and  the  vomer,  since  the  adult  septum  is  usually 
bent  to  one  side  in  its  anterior  two-thirds,  thus  making  one  nasal  cavity  much  smaller 


Portion  of  anterior  section  of  preceding  skull,  seen  from  be- 
hind. The  arrows  occupy  the  opening  from  the  antrum  into  the 
hiatus  semilunaris. 


abo\ 


Normale  und  pathologische  Anatomie  der  Nasenhohle,  2te  Auflage,  Vienna,  1803. 
1  The  development  of  the  nasal  cavity  is  described  with  that  of  the  head. 
1  Escat :  Cavit6  Naso-Pharyngiene,  Paris,  1894. 


THE    NASAL   CAVITY. 


225 


than  the  other.  A  ridge  is  often  found  at  or  near  the  junction  of  these  two  bones 
on  the  prominent  side,  thereby  still  further  reducing  the  smaller  cavity.  This  ridge 
may  be  developed  into  a  shelf,  called  a  spur,  which  may  even  touch  the  opposite 
wall.  The  outer  wall  is  the  most  instructive,  as  giving  the  most  light  on  the  con- 
struction of  the  region.  In  front  is  the  smooth-walled  vestibule,  formed  by  the 
inner  side  of  the  nasal  and  the  ascending  process  of  the  maxilla,  extending  upward 
under  the  frontal  sinus.  The  swelling  known  as  the  agger  may  be  found  near  the 
top  of  its  outer  wall.  The  inferior  turbinate  is  much  the  largest,  reaching  forward 
almost  to  the  opening  in  the  bone.  The  large  inferior  meatus  which  it  overhangs 
is  higher  in  front  than  behind.  The  middle  turbinate,  over  the  middle  meatus,  does 
not  extend  nearly  so  far  forward.  The  little  superior  turbinate  with  the  limited 
stiperior  meatus  below  it  is  still   farther  back,    reaching  only  half-way  along  the 


Fig.  257. 

Sphenoethmoidal 


Extension  of  sphenoidal  sit 
Pituitary  fossa 

enoidal  sinus 


Frontal  sinus 


turbinate 
Middle  meatus 

Inf.  turbinate 


Anterior 
palatine  canal 


Hamular  process 


Palatal  plate  of  sup.  maxilla 
Inner  aspect  of  outer  wall  of  right  nasal  fossa. 


middle  turbinate.  The  three  turbinates  end  behind  very  nearly  in  a  vertical  line, 
the  middle  sometimes  projecting  farthest.  The  lines  of  attachment  of  the  turbinates 
all  slant  downward  and  backward,  but  the  inclination  of  the  middle  one  is  greatest. 
The  variations  in  number  of  the  turbinates  and  the  structures  concealed  by  the 
middle  one  have  been  described  with  the  ethmoid.  The  spheno-ethmoidal  recess  is  a 
lateral  expansion  of  the  cavity  behind  the  superior  turbinate  and  the  front  of  the 
body  of  the  sphenoid.  The  posterior  portion  of  the  outer  wall  of  the  nasal  chamber, 
formed  by  the  palate  bone  and  the  internal  pterygoid  plate,  is  smooth.  The  outer 
wall  slants  inward,  so  that  the  roof  of  the  nasal  cavity  is  narrower  than  the  floor, 
and  has  the  following  openings :  in  the  superior  meatus  that  of  the  posterior  ethmoidal 
cells  ;  farther  back  is  the  spheno-palatine  foramen  communicating  with  the  spheno- 
maxillary fossa.  The  middle  meatus  receives  the  opening  of  the  frontal  sinus  either 
directly   under  the  front  of  the  middle   turbinate  or  through   the  infundibuhan. 


226 


HUMAN   ANATOMY. 


These  arrangements  are  about  equally  common.  It  receives  also  the  openings  of 
the  anterior  ethmoidal  cells,  the  aperture  of  the  a?itrum  into  the  infundibulum,  and 
a  larger  opening  from  the  antrum  behind  the  infundibulum.  The  lachrymal  canal 
opens  into  the  inferior  meatus  under  the  fore  part  of  the  turbinate.  External  to  the 
outer  wall  are  the  orbit,  the  antrum,  and  farther  back  the  spheno-maxillary  fossa 
with  the  posterior  palatine  canal  below  it. 

The  Accessory  Pneumatic  Cavities. — These  include  the  frontal  sinuses, 
the  maxillary  antra,  the  ethmoidal  cells,  and  the  sphenoidal  sinuses.  They  have 
already  been  described  with  the  separate  bones,  but  may  be  here  further  briefly  con- 
sidered in  their  mutual  relations  to  the  nasal  fossae  and  the  skull.  All  of  these  spaces 
open  into  the  nasal  chambers  above  the  inferior  meatus, — the  sphenoidal  cells  into 
the  roof,  the  posterior  ethmoidal  cells  into  the  superior  meatus,  the  anterior  eth- 
moidals, the  antra,  and  the  frontal  sinuses  into  the  middle  meatus. 


Fig.  258. 

Infratemporal  crest      Spheno-maxillary  fissure 
Spheno-palatine  foramen 
Glenoid  fossa 


Mastoid  proceM 
External  auditory  meatus 

Styloid  process      Zygoma       / 
Inner  wall  of  zygomatic  fossa  (external  ptery-     , 
goid  plate) 

Spheno-maxillary  fossa  seen  through  pterygo- 
maxillary  fise,"'D 


Posterior  dental  canal 
Hamular  process 


Lateral  view  of  skull  with  zygomatic  arch  removed. 


The  sphenoidal  sinuses  (Fig.  257)  are  almost  invariably  unequal,  the  sep- 
tum being  much  to  one  side.  The  large  openings  in  the  front  of  the  body  of  the 
sphenoid  are  much  reduced  when  the  cornua  sphenoidalia  are  in  place.  The  open- 
ings of  the  posterior  ethmoidal  cells  are  small  and  irregular.  The  anterior 
cells  make  a  part  of  the  floor  of  the  frontal  sinuses.  They  open  either  into  the 
infundibulum  or  under  the  middle  turbinate. 

The  frontal  sinuses  (Figs.  255,  257),  when  exposed  from  the  front,  have 
a  vaguely  triangular  outline.  One  side  is  against  the  septum,  separating  it  from 
its  fellow,  which  is  rarely  symmetrical.  The  upper  border  runs  from  the  top  of 
this  downward  and  outward.  The  lower  border  bends  downward  at  the  inner  end, 
where  the  cavity  runs  down  to  the  nose  at  the  inner  angle  of  the  orbit.  The  inner 
part  extends  back  for  a  varying  distance  over  the  orbit.  In  about  half  the  cases 
the  cavity  opens  directly  into  the  middle  meatus;  in  the  rest  it  opens  into  the  top  of 


THE   SPHENO-MAXILLARY    FOSSA. 


227 


the  canal  in  the  ethmoid,  known  as  the  infundibulum.  In  the  former  cases  one  of 
the  cells  of  the  ethmoid  is  particularly  liable  to  make  a  projection — the  frontal  bulla 
— into  the  floor  of  the  sinus. 

The  antrum  (Fig.  255)  is  a  four-sided  pyramid  with  an  irregular  base  towards 
the  nasal  cavity  (Merkel).  The  apex  is  at  the  malar.  In  addition  to  the  base, 
an  orbital,  an  anterior,  and  a  posterior  surface  are  recognized.  Owing  to  the 
irregularity  of  the  base  there  is  a  groove  instead  of  an  angle  below,  above  the 
alveolar  process.  (This  relation  is  described  with  the  upper  jaw.)  The  large  in- 
ternal aperture  in  the  superior  maxilla  is  divided  into  two  when  the  other  bones  are 
in  place.  Both  are  near  the  top  ;  the  anterior  opens  into  the  infundibulum,  the  pos- 
terior into  the  middle  meatus.  Partial  septa  project  into  the  antral  cavity.  An 
important  projection  is  that  of  the  infra-orbital  canal. 

The  zygomatic  fossa  (Fig.  258)  is  the  space  internal  to  the  lower  jaw,  sepa- 
rated from  the  temporal  fossa  by  an  imaginary  plane  at  the  level  of  the  upper 
border  of  the  zygoma.      It  is  open  below  and  behind.      The  front  wall  is  made  by 

Fig.  259. 


Orbital  surface  of  great 
wing  of  sphe: 
Frontal  process  of  malar-4f 


Cut  surface  of  zygoma. 


Optic  foramen 
Sphenoidal  fissure 
Sphenoidal  sinus 
Foramen  rotundum 
Vidian  canal 


Posterior  wall  of  spheno- 
"liary  fossa 


1  of  right  half  of  skull,  showing  posterior  wall  of  spheno-maxillary  fossa 
and  part  of  malar  have  been  removed. 


Hamular  process  of  internal  pterygoid  plate 
Zygomatic  surface  of  external  pterygoid  plate 

uperior  maxilla,  ethmoid, 


the  maxilla,  what  little  roof  there  is  by  that  part  of  the  great  wing  of  the  sphenoid 
internal  to  the  infratemporal  crest,  and  the  inner  wall  by  the  external  pterygoid 
plate.  It  has  two  important  fissures, — the  spheno-maxillary,  horizontal,  admitting 
to  the  orbit,  between  the  sphenoid  and  maxilla  ;  the  other,  the  pterygo-maxil- 
lary,  vertical,  between  the  maxillary  bone  and  the  front  of  the  united  pterygoid 
plates. 

The  spheno-maxillary  fossa  (Fig.  259)  is  a  small  cavity  below  and  behind 
the  apex  of  the  orbit  at  the  point  of  junction  of  the  spheno-maxillary  and  the 
pterygo-maxillary  fissures.  The  posterior  wall  is  formed  by  the  sphenoid  above  the 
roots  of  the  pterygoid  plates.  The  transverse  and  antero-posterior  diameters  of  the 
fossa  are  about  fifteen  millimetres.  It  contains  the  spheno-palatine  or  Meckel's 
ganglion.  The  foramen  rotundum  opens  into  it  behind,  transmitting  the  superior 
maxillary  division  of  the  trifacial  nerve.  More  internal  and  lower  on  the  posterior 
wall  is  the  orifice  of  the  ■  Vidian  canal,  transmitting  the  great  superficial  and  deep 
petrosal  nerves  and  accompanying  blood-vessels.      Still  nearer  the  median  line  is 


228  HUMAN    ANATOMY. 

the  minute  pterygopalatine  cajial,  formed  by  the  palate  and  sphenoid  bones.  The 
spheno-palatine  forame?i  opens  through  the  inner  wall  into  the  nasal  cavity.  The 
fossa  opens  below  into  the  posterior  palatine  canal. 

The  Roof  of  the  Mouth. — This  comprises  the  liard  palate  and  the  inner 
aspect  of  the  alveolar  process.  The  proportions,  as  stated  elsewhere  (page  229), 
vary  ;  as  a  rule,  the  broad  palate  is  less  vaulted  than  the  narrow  one.  The  oral 
roof  presents  the  orifices  of  three  canals, — the  anterior^  and  the  two  posterior 
palatine.  The  first  is  situated  in  the  mid-line  in  front,  the  others  at  the  outer 
posterior  angles.  The  palatine  grooves  for  the  anterior  palatine  nerves  and  accom- 
panying blood-vessels  extend  forward  from  the  posterior  palatine  foramina.  Be- 
hind, but  close  to,  the  latter  are  the  orifices  of  the  accessory  palatine  canals. 
The  inner  side  of  the  alveolar  process  is  rough  except  opposite  the  second  and 
third  molar  teeth,  and  the  same  is  true  of  that  part  of  the  palate  made  by  the  superior 
maxillae.  An  occasional  swelling,  the  torus  palatinus,  is  in  the  mid-line  at  the 
junction  of  the  superior  maxillae.  Internal  to  the  first  molar  is  a  ridge  with  the 
groove  outside  of  it  at  the  lateral  border  of  the  maxilla.  The  line  separating  the 
superior  maxilla?  from  the  horizontal  plates  of  the  palate  bones  has  a  forward  curve 
in  the  middle  in  nearly  three-quarters  of  the  cases.  It  is  about  straight  in  some 
twenty  per  cent,  and  curved  backward  in  the  rest.  The  fissures  are  not  always 
symmetrical.2 

The  Architecture  of  the  Face. — With  the  exception  of  the  lower  jaw,  the 
structure  of  the  face  is  extremely  light.  It  is  subject  to  no  strain  save  through  that 
bone,  and  to  some  extent  through  the  action  of  the  tongue  on  the  palate  ;  it  has, 
however,  to  be  protected  against  occasional  violence.  There  are  certain  strong  and 
strengthening  regions.  The  hard  palate  is  strong  throughout,  except  at  the  hind 
part,  and  especially  strong  back  of  the  incisors.  Some  strength  is  gained  by  a 
thickening  just  outside  of  the  nasal  opening  above  the  canine  teeth,  running  up 
into  the  ridge  in  front  of  the  lachrymal  groove.  The  root  of  the  nose  is  also  very 
thick.  The  face  is  considerably  strengthened  through  the  malar  bone  and  its  con- 
nections, especially  with  the  robust  external  angular  process.  A  little  support  is 
probably  given  to  the  back  of  the  jaw  through  the  pterygoids. 


ANTHROPOLOGY   OF  THE  SKULL. 

There  are  certain  terms  and  measurements  which  should  be  known,  especially  as  some  of 
them  come  into  practical  use  in  the  surgery  of  the  skull. 

Points  on  the  Surface  of  the  Skull. — (See  also  Fig.  265,  page  241.) 

Alveolar  point,  the  lowest  point  in  the  mid-line  of  the  upper  alveolar  process. 

Asterion,  the  lower  end  of  the  lambdoidai  suture  ;  three  sutures  diverge  from  it  like  rays. 

Auricular  point,  the  centre  of  the  external  auditory  meatus. 

Basion,  the  anterior  point  of  the  margin  of  the  foramen  magnum. 

Bregma,  the  anterior  end  of  the  sagittal  suture. 

Dacryon,  the  point  of  contact  of  the  frontal,  maxillary,  and  lachrymal  bones. 

Glabella,  the  region  above  the  nose  between  the  superciliary  eminences. 

Glenoid  point,  the  centre  of  the  glenoid  fossa. 

Gonion,  the  outer  side  of  the  angle  of  the  lower  jaw. 

Inion,  the  external  occipital  protuberance. 

Lambda,  the  posterior  end  of  the  sagittal  suture. 

Malar  point,  the  most  prominent  point  of  that  bone.  . 

Mental  point,  the  most  anterior  point  of  the  symphysis  of  the  lower  jaw. 

Nasion,  the  point  of  contact  of  the  frontal  bone  with  both  nasals. 

Obelion,  the  sagittal  suture  in  the  region  of  the  parietal  foramina. 

Occipital  point,  the  most  posterior  point  in  the  mid-line.     (It  is  above  the  protuberance.) 

Ophryon,  the  point  of  intersection  of  the  median  line  with  a  line  connecting  the  tops  of  the 
orbits. 

Opisthion,  the  posterior  point  of  the  margin  of  the  foramen  magnum. 

Pterion,  the  region  where  the  frontal,  the  great  wing  of  the  sphenoid,  the  parietal,  and 
the  temporal  bones  almost  meet.  (As,  in  fact,  they  very  rarely  do  meet,  the  term  is  a  vague 
one. ) 

1  For  the  description  of  this  canal,  see  under  Superior  Maxilla  (page  201). 

2  Stieda  :  Arch,  fur  Anthropol.,  1S93. 


ANTHROPOLOGY    OF   THE    SKULL.  229 

Stephanion,  the  region  where  the  curved  lines  on  the  temporal  bone  cross  the  coronal 
suture. 

Subnasal point,  in  the  median  line  at  the  root  of  the  anterior  nasal  spine. 

Indices. — The  cephalic  index  is  the  ratio  of  the  breadth  to  the  length  of  the  skull 
/woX_tmadth\  Thg  iengtn  ;s  taj^en  from the  glabella  to  the  occipital  point,  and  the  breadth  is 
the  greatest  transverse  diameter  above  the  supramastoid  ridge.  A  high  index  means  a  short 
skull  ;  a  low  index,  a  long  one.  A  skull  with  an  index  above  80  is  brachycephalic ;  from  75  to 
So,  mesaticephalic  ;  below  75,  dolichocephalic. 

The  index  of  height  is  the  ratio  of  the  line  from  basion  to  bregma  to  the  length 
/ioox  height  \  j^  sj.ujj  wjtn  an  jncjex  above  y5  ;s  hypsicephalic ;  from  70  to  75,  orthocephalic  ; 
below  70,  platycephalic. 

The  facial  index  is  the  ratio  of  the  length  to  the  breadth  of  the  face  ( I0°broa"t'|f  )  •  The 
length  is  from  the  nasion  to  the  mental  point,  and  the  breadth  is  the  greatest  at  the  zygomatic 
arches.  A  high  index  means  a  long  face.  A  head  with  a  facial  index  above  90  is  leptoprosopic  ; 
one  with  a  lower  one,  chamtzprosopic.  In  the  absence  of  the  lower  jaw  the  index  of  the  upper 
face  may  be  taken,  which  is  almost  equally  valuable.  The  only  difference  is  that  the  length  is 
taken  from  the  nasion  to  the  alveolar  point,  and  that  an  index  above  50  is  leptoprosopic,  and  one 
below  it  chamaprosopic. 

The  nasal  index  is  the  ratio  of  the  length  of  the  nose  to  the  breadth  ( '"breadth^" )'     ^e 

length  is  measured  in  a  straight  line  from  the  fronto-nasal  suture  to  the  anterior  nasal  spine. 

A  skull  is  leptorhine  when  the  index  is  below  4S  ;  when  from  4S  to  53,  mesorhine ;  and  when 

above  53,  platyrhine. 

The  orbital  index  is  the  ratio  of  the  height  of  the  base  to  the  breadth,  thus  ( ^r-1 — ^—  ). 

°  V      breadth      / 

The  breadth  is  a  horizontal  from  the  outer  border  to  the  point  of  contact  of  the  frontal  with  the 

maxilla  and  lachrymal.     A  large  index  means  a  high  orbit.     An  orbit  with  an  index  below  84  is 

microseme ;  with  one  from  84  to  89,  mesoseme ;  with  one  above  89,  megaseme.    An  index  of  70 

is  low  for  a  Caucasian,  and  one  of  106  very  high.    The  average  for  English  skulls  is  said  to  be  88. 

The  index  depends  considerably  on  the  extent  to  which  the  upper  border  overhangs. 

The  palatal  index  is  the  ratio  of  the  breadth  to  the  length.  The  former  is  taken  from  the 
socket  of  the  second  molar  of  one  side  to  that  of  the  other  ;  the  latter  is  from  the  alveolar 
process  in  the  middle  line  to  the  posterior  nasal  spine  ( I0°  ^  ^ — )  ■ 

Prognathism  denotes  the  forward  projection  of  the  face.  This  was  formerly  expressed  by 
what  is  known  as  Camper* s  facial  angle,  which  was  measured  on  the  arc  between  two  lines 
meeting  at  the  nasal  spine,  one  starting  from  the  auricular  point,  the  other  from  the  most  promi- 
nent part  of  the  forehead  in  the  middle  line  (avoiding  the  projecting  nose).  This  has  fallen  into 
disuse  owing  to  inherent  defects,  and  perhaps  in  part  to  the  discordant  directions  given  for 
drawing  the  lines.  Flower' ' s  gnathic  index  is  the  ratio  of  the  line  from  the  basion  to  the 
alveolar  point  to  the  line  from  the  basion  to  the  nasion  (I0°  bag^^°^l  "j-  A  skull  is 
orthognathous  with  an  index  below  98  ;  mesognathous  with  one  from  98  to  103  ;  prognathous 
with  one  above  103. 

Shape  of  the  Skull. — Extreme  forms  occur  in  Caucasians.  The  long,  narrow  skull,  with 
often  a  slight  prominence  along  the  sagittal  suture,  the  scaphoid  form,  is  due  to  the  early  closure 
of  the  sagittal  suture,  and  the  short,  round  skull  to  that  of  the  transverse  ones.  In  support  of  this 
theory  is  the  fact  that  the  metopic  or  median  frontal  suture  is  never  found  in  narrow,  but  only  in 
broad  skulls.  The  high,  sugar-loaf,  acrocephalic  skull  shows  obliteration  of  all  three  sutures  on 
the  top  of  the  vault.  The  great  backward  occipital  projection  sometimes  seen  is  usually  asso- 
ciated with  many  Wormian  bones  in  the  lambdoidal  suture. 

The  long  type  of  skull  is  naturally  associated  with  the  long,  narrow  face,  and  the  round 
head  with  thebroad  face  ;  but  the  connection  is  not  absolute.  The  two  types  of  face  deserve  a 
short  consideration.  The  narrow  face  has  the  high  orbit,  the  narrow  nose,  with  the  aperture 
pointed  above,  and  a  long,  narrow  palate.  The  outline  of  the  range  of  teeth  in  one  jaw  to  a  great 
extent  determines  that  of  the  other  ;  but,  in  addition  to  the  smaller  curve,  the  lower  jaw  in  this 
form  is  rather  delicate,  is  particularly  likely  to  show  the  constriction  in  front  of  the  masseter, 
and  has  a  more  obtuse  angle.  The  short  and  broad  face  has  wide,  low  orbits,  a  broad  and 
almost  quadrilateral  opening  of  the  nose,  and  a  wide  pair  of  jaws,  the  lower  with  an  approxi- 
mately square  angle.  If,  as  is  most  probably  the  case,  the  head  is  orthognathous,  the  edges  of 
the  teeth  tend  to  form  part  of  an  antero-posterior  curve,  which  is  particularly  marked  in  the 
region  of  the  molars.  It  is  to  be  noted,  however,  that  some,  or  any,  of  these  features  may  be 
found  in  a  face  of  the  opposite  type. 

Dimensions  of  the  Skull. — The  actual  length  of  the  various  diameters  is  of  much  less 
importance  than  their  relations  to  one  another  in  the  science  of  craniology ;  they  may,  however, 
be  important  in  medico-legal  questions.  With  the  exception  of  the  height,  they  vary  within 
wide  limits,  even  among  Caucasians.  In  the  following  table  the  means  of  both  sexes  are  from 
Broca  : 

Males.  Females. 

Mean.                                                                                      Millimetres.  Millii 

Length 1S2  174 

Breadth 145  135 

Height 132  125 


23o  HUMAN   ANATOMY. 

Cranial  Capacity. — This  may  vary  in  all  races  from  iooo  to  1S00  cubic  centimetres. 
Welcker  gives  the  following  means  and  extremes  for  white  races  : ' 


aximum. 

Minimum. 
Cu.  cm. 

I790 
I550 

1220 
I090 

Males 1450 

Females 1300 

A  skull  with  a  capacity  exceeding  1450  cubic  centimetres  is  megacephalic  ;  one  with  a 
capacity  from  1350  to  1450,  mesocephalic  ;  one  below  1350,  microcephalic. 

Manouvrier  has  devised  a  formula  for  calculating  the  weight  of  the  brain  from  the  cranial 
capacity,  as  follows  :  weight  in  grammes  is  to  capacity  in  cubic  centimetres  as  1  to  0.87. 

Asymmetry. — The  whole  head  is  almost  always  asymmetrical.  The  left  side  of  the 
cranium,  as  shown  by  hatters'  models,  is  larger,  especially  in  the  frontal  region.  The  right 
side  of  the  head  is  usually  the  higher.  The  cause  of  this  is  probably  to  be  found  in  habitual 
position.  The  spine  is  not  held  symmetrically,  but  the  atlas  inclines  to  the  left ;  the  head,  when 
held  most  firmly,  does  not  rest  evenly  on  both  condyles,  but  on  one,  usually  the  left.  The 
position  of  the  head,  thus  taken,  is  not  enough  to  compensate  for  the  obliquity  of  the  base ;  but 
certain  changes  take  place  in  the  relations  of  the  component  parts.     Thus  a  face  which  seems 

Fig.  260. 


Anterior  fontanelle 


The  skull  at  birth,  from  before. 

tolerably  symmetrical  when  resting  on  the  left  condyle  only  becomes  quite  uneven  if  placed 
upon  both.  The  right  orbit  is  usually  the  higher,  the  right  side  of  the  jaw  is  the  stronger,  and 
its  teeth  are  set  in  a  smaller  curve.  The  tip  of  the  nose  turns  to  the  right.  Moreover,  the  face 
lacks  symmetry  in  another  direction  :  the  right  upper  jaw  and  the  malar  bone  are  more  promi- 
nent than  the  left.  More  striking  differences,  depending  on  these,  are  seen  during  life,  which 
are  ascribed  to  the  effect  of  gravity  on  soft  parts  habitually  held  unevenly,  the  right  side  being 
the  higher.  The  right  eye  is  the  higher  and,  apparently,  the  larger,  the  lids  being  farther  apart ; 
while  the  cleft  is  narrow  on  the  left  and  the  eye  nearer  the  nose.  The  left  nostril  is  the  larger  ; 
the  left  fold  of  the  cheek  is  less  marked.  In  a  certain  proportion  of  persons  all  these  peculiarities 
are  reversed,  and  some  of  them  may  be  transposed  without  the  others. 

Growth  and  Age  of  the  Skull. — By  the  sixth  month  of  fcetal  life  the  skull,  though  smaller,  is 
in  much  the  same  condition  as  at  birth,  except  that  then  the  occipital  region  is  relatively  larger. 
The  most  striking  points  are  the  insignificance  of  the  face  and  the  flatness  of  the  inferior  surface. 
In  the  cranium  the  frontal  region  is  relatively  small.  The  vault,  which  is  developed  in  mem- 
brane, presents  marked  prominences  at  the  parietal  and  frontal  eminences,  and  a  smaller  one  at 

1  Extreme  cases  occasionally  pass  these  limits.  There  is  in  the  Warren  Museum  the  skull 
of  a  Highlander  with  a  capacity  of  1990  cubic  centimetres,  and  one  of  a  tall  man,  presumably  an 
American,  who  could  read  and  write,  though  his  intelligence  was  defective,  with  a  capacity  of 
1225  cubic  centimetres.  Turner  has  noted  the  skull  of  a  female  Australian  of  930  cubic  centi- 
metres' capacity. 


GROWTH    OF   THE   SKULL. 


231 


the  external  occipital  protuberance,  from  which  radiating  lines  in  the  bone  mark  the  process  of 
development.  The  bones  of  the  vault  are  exceedingly  thin.  Each  is  separate,  the  external 
periosteum  and  the  dura  uniting  at  the  edges,  thus  limiting  the  spread  of  an  effusion  under  the 
former  to  one  bone. 

Six  places  where  there  are  considerable  membranous  intervals  between  the  developing 
bones  are  called  fontanelles.  They  are  situated  at  the  four  angles  of  the  parietal  bones,  so  that 
two  are  median  and  two  are  on  either  side.  The  median  ones,  by  far  the  most  prominent,  are 
the  anterior  and  posterior  fontanelles.  The  anterior  fontane lie,  an  important  landmark  in  mid- 
wifery, is  a  diamond-shaped  space  between  the  rounded  angles  of  the  parietals  and  frontals,  some 
thirty-five  millimetres  long  by  twenty-five  millimetres  broad.  This  one  continues  to  grow  after 
birth,  and  is  not  closed  till  some  time  in  the  first  half  of  the  second  yeaf,  or  even  later.  The 
posterior  fontanelle  is  situated  at  the  apex  of  the  squamous  portion  of  the  occipital,  extending 
between  the  parietals.  At  an  early  stage,  owing  to  the  median  fissure  in  the  occipital,  it  is 
diamond-shaped,  but  later  it  is  triangular.  The  space  is  more  or  less  filled  up  in  the  last  two 
months  before  birth,  but  it  may  not  be  truly  closed  for  a  month  or  two  after.  The  anterior 
lateral  fontanelle  is  a  small  unimportant  space  at  the  lower  anterior  angle  of  the  parietal,  above 
the  great  wing  of  the  sphenoid,  and  extending  around  it.  It  usually  closes  at  from  two  to  three 
months  after  birth.  The  part  between  the  sphenoid  and  squamosal  is  likely  to  persist  the 
longest.     According  to  Sutton,1  in  early  fcetal  life  the  orbito-sphenoid  bone  reaches  the  lateral 

Fig.  261. 


Posterior  lateral  fontanelle 


The  skull  at  birth,  lateral  aspect. 

wall  of  the  skull  at  this  point,  and  a  piece  of  cartilage  belonging  to  it  is  found  in  this  fontanelle. 
It  becomes  bone  in  the  course  of  the  first  year,  and  may  unite  with  either  sphenoid,  temporal, 
frontal,  or  parietal,  or  persist  as  the  epipteric  bone.  It  most  often  joins  the  parietal.  The  pos- 
terior lateral  fontanelle,  under  the  corresponding  angle  of  the  parietal,  extends  down  between 
the  temporal  and  the  occipital.  It  is  larger  than  the  preceding,  and  may  be  very  distinct  for  a 
month  or  more  after  birth.  Its  complete  closure  is  said  never  to  occur  before  the  twelfth  month, 
and,  perhaps,  usually  not  till  the  second  year.2  The  sagittal  fontanelle  (see  Ossification  of 
Parietal )  may  be  present  at  the  seventh  month  of  fcetal  life,  or  later.  The  oblique  fissure  at  the 
line  of  junction  of  the  two  parts  of  the  squamous  portion  of  the  occipital  persists  till  after  birth, 
and  must  not  be  mistaken  for  an  effect  of  violence. 

The  mastoid  process  does  not  exist  at  birth.  The  tympanic  bone  is  a  mere  frame  for  the 
ear-drum.  The  base  of  the  cranium  is  very  flat.  The  condyles  are  barely  prominent,  and  the 
basilar  process  rises  but  slightly. 

In  the  first  year  the  outer  surface  of  the  bones  of  the  vault  becomes  smooth.  The  bones  gain 
in  thickness,  and  in  the  second  vear  the  diploe  appears.  At  the  same  time  the  jagged  points 
develop  in  the  sutures,  and  at  the  end  of  that  year  the  metopic  suture  between  the  frontals 
closes. 


1  Journal  of  Anatomy  and  Physiology,  vol.  xviii.,  1884. 

2  Adachi :  Ueber  die  Seitenfontanellen,  Zeitschrift  fur  Morph.  und  Anthrop.,  Bd.  ii.,  Heft  2. 


232 


HUMAN   ANATOMY. 


The  face,  while  helping  to  form  the  orbit  and  nasal  cavities,  is  essentially  for  the  jaws,  and 
the  jaws  for  the  teeth.  The  greatest  change  in  the  head  after  birth  is  the  downward  growth  of 
the  face.  According  to  Froriep,  in  the  infant  the  face  is  to  the  cranium  as  i  to  S  ;  at  two  years 
as  i  to  6  ;  at  five,  as  i  to  4  ;  at  ten,  as  1  to  3  ;  in  the  grown  woman  as  1  to  2.5  ;  in  the  man 
as  1  to  2.  On  contrasting  the  front  view  in  the  infant  and  adult,  counting  as  "face"  all  below 
a  line  at  the  top  of  the  orbits  and  as  "  cranium"  all  above  it,  it  will  be  seen  that  in  the  infant 
the  cranium  forms  about  one-half  and  in  the  adult  much  less.  The  lower  border  of  the  nasal 
opening  is  at  birth  but  very  little  below  the  orbit.  A  line  connecting  the  lowest  points  of  the 
malar  bones  passes  at  this  age  midway  between  the  nasal  opening  and  the  border  of  the  alveolar 
process.  At  birth  the  nasal  aperture  is  relatively  broad  ;  its  lower  border  is  not  sharply  marked 
off  from  the  face.  A  line  from  the  nasal  spine  runs  outward  to  end  inside  the  cavity,  and  the 
crest  from  the  outer  border  is  still  rudimentary,  ending  shortly  on  the  front  of  the  face,  so  that 
at  the  outer  angle  there  is  no  distinct  separation  between  face  and  nasal  cavity.1  The  nasal 
cavity  is  shallow,  the  posterior  nares  very  small.  The  vomer  slants  strongly  forward.  The 
lower  jaw  is  small  and  the  angle  of  the  ramus  very  obtuse.  The  alveolar  processes  are  rudi- 
mentary.    The  breadth  of  the  skull  at  its  widest  equals  or  exceeds  the  combined  height  of  the 

Fig.  262. 


Posterior  fontanelle 


Interparietal  suture 


Anterior  fontanell 


The  skull  at  birth,  from  above 


cranium  and  face  in  the  infant ;  in  the  adult  it  is  but  three-quarters  of  it.     The  breadth  of  the 
face  is  to  its  height  as  10  to  4  at  birth,  and  about  as  9  to  S  in  the  adult. 

Merkel  divides  the  growth  of  the  head  into  two  periods,  with  an  intervening  one  of  rest. 
The  first  ends  with  the  seventh  year,  and  is  followed  by  inactivity  till  puberty,  when  the  second 
period  begins.  The  fi rst pe riod rmay  be  subdivided  into  three  stages.  In  the  first  stage,  reach- 
ing to  the  end  of  the  first  year,  the  growth  is  general,  but  the  face  gains  on  the  cranium.  At  six 
months  the  basilar  process  rises  more  sharply,  which,  with  the  downward  growth  of  the  face,  has 
an  important  effect  on  the  shape  of  the  naso-pharynx.  The  lower  part  of  the  nasal  cavity  gains 
particularly.  The  posterior  opening  doubles  its  size  in  the  first  six  months,  to  remain  stationary 
till  the  end  of  the  second  year.  In  the  second  stage,  to  the  end  of  the  fifth  year,  the  vault  grows 
more  than  the  base,  assuming  a  more  rounded  and  finished  appearance.  The  face  still  gains 
relatively,  but  grows  more  in  breadth  than  in  height.  In  the  third  stage,  corresponding  roughiy 
to  the  seventh  year,  the  base  grows  more  and  the  vault  less.  The  face  lengthens  considerably, 
the  growth  in  the  nasal  chambers  being  chiefly  in  the  lower  part.  The  head,  though  small,  has 
lost  the  infantile  aspect.  The  foramen  magnum  and  the  petrous  portion  of  the  temporal  have 
reached  their  full  size,  and  the  orbit  very  nearly.  The  parietal  and  frontal  eminences  are  still 
very  prominent.      The  mastoid  is  rudimentary.     This  condition  lasts  till  puberty,  when  the 

1  Macalister  :  Journal  of  Anatomy  and  Physiology,  vol.  xxxii.,  1898. 


GROWTH   OF   THE   SKULL.  233 

second  period  begins.  This  is  marked  by  growth  in  all  directions,  the  gradual  rounding  off  of 
the  eminences  of  the  vault,  the  progress  of  the  mastoid,  the  strengthening  of  ridges,  the  greater 
curving  of  the  zygomatic  arches,  and  the  increase  of  the  face.  This  last  is  due  chiefly  to  the 
advance  of  the  nose,  the  gain  of  the  superciliary  eminences,  and  the  increase  of  the  lower  jaw. 
The  rise  of  the  basilar  process  increases  and  the  occipital  condyles  stand  out  more  from  the  bases 
at  the  front  edges.  These  processes  are  nearly  finished  in  the  female  by  nineteen  and  in  the 
male  one  or  two  years  later,  though,  especially  in  the  latter,  they  require  several  years  more  for 
their  absolute  completion.  The  thickness  of  the  vault  is  very  nearly  reached  by  puberty.  At 
seven  the  frontal  sinus  is  only  as  large  as  a  pea.  Its  development  is  not  completed  before  the 
twentieth  year.     There  is  no  means  of  knowing  whether  or  not  it  then  entirely  ceases. 

The  orbit  bears  nearly  the  same  proportion  to  the  cranium  at  all  ages  ;  but  at  birth  it  equals 
about  one-half  of  the  height  of  the  face,  and  in  the  adult  rather  less  than  one-third.  At  birth  the 
axis  of  the  orbit  is  horizontal.  While  sometimes  the  transverse  diameter  of  the  base  of  the  orbit 
is  much  the  larger,  this  does  not  seem  to  be  always  so.  As  the  face  grows  the  vertical  diameter 
increases  rapidly,  so  that,  according  to  Merkel,  at  five  the  base  lacks  only  two  or  three  millimetres 
of  the  adult  height,  which  it  gains  in  the  next  two  years.  The  full  breadth  is  probably  not 
attained  before  puberty. 

The  changes  in  the  nasal  cavity  are  important  as  an  essential  element  in  the  growth  of  the 
face.  At  birth  the  line  of  the  hard  palate,  if  prolonged  back,  would  strike  near  the  junction  of 
the  basilar  process  and  sphenoid  ;  at  three  it  strikes  near  the  middle  of  the  basilar  ;  at  six,  the 
front  edge  of  the  foramen  magnum,  which  is  nearly  or  quite  the  condition  of  the  adult.  The 
measurements  of  the  vertical  diameter  of  the  choanae  are  important  from  their  significance  with 
regard  to  both  the  nose  and  the  pharynx.  At  birth  the  height  is  from  five  to  six  millimetres 
(seven  millimetres  is  exceptional)  and  the  breadth  of  each  opening  very  little  greater.  At  from 
six  months  to  a  year  both  diameters  have  doubled,  their  proportions  remaining  unchanged. 
There  is  little  change  before  the  end  of  the  second  year,  when  the  height  increases  more  rapidly. 
Thus  they  change  from  circular  to  oblong  openings.  It  is  not  till  after  puberty  that  the  height 
exceeds  the  distance  between  the  internal  pterygoid  plates. 

HEIGHT  OF  POSTERIOR  NARES. 

Authority.  Age. 

Disse 4 

Disse 5 

Escat 5 

Escat 8 

Dwight 7  or  8 

Dwight 7  or  8 

Dwight 10  female 

Dwight 11 

Dwight 14  female 

Escat 14 

Dwight 15 

Dwight \t>yz 

Dwight 17 

Dwight 18 

Dwight 19 

Escat 15  to  iS 

The  Closure  of  the  Sutures. — The  occipital  bone  unites  with  the  basisphenoid  at  the 
cerebral  aspect  about  seventeen  and  on  the  outside  of  the  skull  some  three  years  later.  The 
lower  end  of  the  suture  between  the  occipital  and  the  mastoid  process  is  one  of  the  first  to  close. 
We  have  seen  it  lost  in  a  skull  of  fourteen,  of  which  the  other  bones  were  almost  falling  apart. 
No  doubt  this  was  exceptionally  early.  The  closure  of  the  great  sutures  of  the  vault x  ( to  which 
the  term  is  usually  applied)  begins  on  the  inside  of  the  skull,  probably  before  thirty,  at  the  lower 
ends  of  the  coronal  and  at  the  back  of  the  sagittal,  and  spreads  irregularly.  The  process  is 
generally  far  advanced  before  it  appears  on  the  outside.  The  closure  of  the  sutures  on  one  side 
of  the  head  does  not  necessarily  follow  the  same  course  on  the  other.  It  has  usually  begun  on 
the  outside  by  forty,  although  the  sutures  are  still  distinct.  They  probably  are  nearly  or  quite 
obliterated  ori  the  inside  by  fifty-five.  The  apex  of  the  lambdoidal  suture  is  one  of  the  last 
points  to  persist  internally.  It  is  impossible  to  state  with  accuracy  the  time  at  which  the 
sutures  disappear  on  the  outside,  as  this  may  never  occur,  and  the  process  throughout  is  utterly 
irregular.  All  may  be  gone  very  early  or  all  may  be  distinct  at  an  advanced  age.  When  the 
metopic  suture  fails  to  close  in  early  childhood  it  is  one  of  the  very  last  to  disappear.  It  is 
unsafe  from  the  sutures  alone  to  draw  any  conclusions  as  to  the  age  of  a  skull. 
The  weight  of  the  skull  in  both  sexes  is  greatest  from  twenty  to  forty-five.2 
The  changes  in  old  age  are  essentially  atrophic.  The  most  striking  is  the  absorption  of 
the  alveolar  processes  ;  this,  however,  may  occur  prematurely  from  the  loss  of  teeth.  The 
angle  of  the  lower  jaw  becomes  much  more  obtuse.     The  thin  parts  of  the  face  and  of  the  base 

1  Dwight  :  The  Closure  of  the  Cranial  Sutures  as  a  Sign  of  Age,  Boston  Medical  and  Sur- 
gical Journal,  1S90.     Parsons  :  Anthrop.  Institute  G.  Brit,  and  Ireland,  vol.  xxx,  1905. 

2  Gurriere  and  Massetti :  Rivista  speriment.  di  Freniatria  e  de  Med.  legale,  1S95. 


Sex. 

Millimetres. 

male 

16 

emale 

II 

15 
18 

male 

23 

female 

23 

female 

19 

male 

29 

male 

24 

cases) 

25 

234 


HUMAN   ANATOMY. 


of  the  skull  become  still  thinner  and  may  be  quite  absorbed.  The  thinning  of  the  vault  is  less 
marked.  Occasionally,  in  extreme  age,  symmetrical  depressions  appear  in  the  upper  parts  of 
the  parietals  behind  the  vertex.  In  the  latter  part  of  life  the  frontal  sinuses  enlarge,  as  the  inner 
table  follows  the  shrinking  brain.  In  some  rare  cases  the  skull  grows  heavier  in  old  age,  owing 
to  an  increase  in  thickness  of  the  inner  table. 

Differences  due  to  Sex. — There  is  no  marked  sexual  difference  in  skulls  up  to  puberty. 
These  characteristics  appear  during  the  last  stage  of  growth.  They  may  be  summed  up  by 
saying  that  the  female  skull  differs  less  than  the  male  from  that  of  childhood.  The  parietal  and 
frontal  eminences  are  more  prominent ;  the  superciliary  prominences  and  glabella  less  marked  ; 
the  zygomata,  mastoid,  occipital  protuberance,  and  muscular  ridges  less  developed.  The  whole 
structure  is  lighter.  The  face  is  smaller  in  proportion  to  the  cranium,  owing  to  the  lighter 
jaws.  The  lower  jaw  alone  is  also  relatively  lighter  to  the  cranium.1  The  frontal  and  occipital 
regions  are  less  developed  than  the  parietal.  Two  points  are  of  especial  value, — namely,  in  the 
female  skull  the  change  of  direction  from  the  forehead  to  the  top  of  the  head  is  more  sudden, 
suggesting  a  definite  angle,  while  in  man  the  passage  is  imperceptible  ;  and,  secondly,  in  man  a 
wedge-shaped  growth  above  the  front  of  the  condyle  is  more  developed,  so  as  to  throw  the  face 
higher  up.  There  is  no  trouble  in  recognizing  a  typical  skull  of  either  sex  ;  but  in  many  cases 
the  decision  is  difficult,  and  sometimes  impossible. 

Surface  Anatomy.  —It  is  convenient  for  many  reasons  to  settle  on  what  shall 
be  called  the  normal  level  of  the  skull.  This  should  be  parallel  with  the  axis  of  the 
eye  when  looking  at  the  horizon.  It  is  expressed  by  a  plane  passing  through  the 
points  above  the  middle  of  each  external  auditory  meatus  and  the  lowest  points  of 
the  anterior  border  of  each  orbit.  A  simple  method  is  to  regard  the  upper  border 
of  the  zygoma  as  horizontal,  but  this  is  not  sufficiently  accurate  with  skulls  of  low 
races.  The  following  parts  are  easily  explored  by  the  finger  :  the  whole  of  the  vault 
as  far  as  the  superior  occipital  line,  the  occipital  protuberance  behind,  and  the  supe- 
rior temporal  ridges  at  the  sides.  Often  the  bregma  and  sometimes  the  chief  sutures 
can  be  made  out.  The  possibility  of  parietal  depressions  is  to  be  remembered  in  cases 
of  injury  ;  also  that  they  may  be  expected  to  be  symmetrical. 

The  superciliary  eminences  and  the  upper  borders  of  the  orbits  are  easily 
explored.  The  prominence  of  the  former  is  likely  to  imply  a  large  frontal  sinus  ; 
but  the  converse  is  not  true,  for,  especially  in  the  latter  part  of  life,  there  may  be  a 
large  sinus  with  no  external  indication.  The  sinus  always  extends  downward  to  the 
inner  side  of  the  orbit,  but  its  expansion  outward  and  backward  is  very  uncertain. 
The  external  angular  process  protects  the  outer  side  of  the  eye,  and  one  or  both 
temporal  ridges  can  be  followed  from  it.  The  suture  between  the  process  and  the 
malar  is  easily  felt  through  the  skin.  A  line  connecting  the  most  prominent  points 
of  the  zygomatic  arches  indicates  the  depth  of  the  orbits. 

The  zygoma  is  easily  followed  backward  to  the  auricle.  By  pressing  the  latter 
forward,  the  supramastoid  crest  can  be  made  out.  Just  below  this  is  the  spina  supra- 
meatum,  close  to  the  cartilaginous  meatus.  The  outside  of  the  mastoid  is  easily 
explored.  The  course  of  the  lateral  sinus  is  in  a  curved  line  with  the  convexity 
upward  from  the  external  occipital  protuberance  to  the  upper  part  of  the  mastoid, 
only  the  lower  part  of  the  sinus  touching  a  straight  line  between  those  points. 
According  to  Birmingham,  the  descending  part  follows  roughly  the  line  of  the 
attachment  of  the  ear.  There  is,  however,  great  variation  in  its  course  as  to  the 
sharpness  of  its  descent  and  its  relation  to  the  surface  of  the  mastoid.  It  may 
be  exceedingly  close,  or  in  no  particular  relation  to  it  (Figs.  199,  200,  and  de- 
scription of  the  temporal  bone,  page  179).  The  antrum  leading  to  the  mastoid 
cells  is  just  back  of  the  upper  part  of  the  meatus,  often  under  a  small,  smooth 
surface. 

The  antrum  of  Highmore  in  the  superior  maxilla  extends  upward  to  the  floor 
of  the  orbit,  outward  into  the  malar  prominence,  downward  to  just  above  the  line  of 
reflection  of  the  mucous  membrane  from  the  lips  to  the  alveolar  process,  and  inward 
to  the  line  of  attachment  of  the  ala  of  the  nose,  which  is  above  the  canine  eminence 
and  marks  the  separation  of  the  antrum  from  the  nasal  cavity. 

The  variations  of  the  upper  end  of  the  infundibulum  are  of  interest.  In  the 
cases  (about  one-half)  in  which  it  drains  the  frontal  sinus  it  is  easy  for  fluid  from  the 
latter  to  run  through  the  infundibulum  both  into  the  nasal  cavity  through  the  hiatus 
semilunaris  and    into   the  antrum   through    the  opening  in  its  outer  side.      If   the 

1  Gurriere  and  Masset'ri  :  Rivista  speriment.  di  Freniatria  e  de  Med.  legale,  1895. 


PRACTICAL   CONSIDERATIONS:    THE   SKULL.  235 

infundibulum  ends  blindly,  there  is  less  likelihood  of  inflammation  spreading  from 
the  frontal  sinus  to  the  antrum.  The  nasal  bones  and  their  junction  with  the  nasal 
cartilages  are  easily  recognized.  The  ramus  and  body  of  the  lower  jaw  are  to  be 
examined  from  the  outside.  The  head  and  coronoid  process  are  felt  more  easily  if 
the  mouth  be  opened. 

PRACTICAL   CONSIDERATIONS. 

The  Cranium. — In  the  development  of  the  cranium,  provision  is  made  for  its 
continuous  enlargement,  so  that  it  may  accommodate  the  rapidly  growing  brain. 
Accordingly,  the  first  rudiment  is  a  membranous  capsule,  at  the  base  of  which  carti- 
lage is  soon  formed,  giving  support  to  the  overlying  portions.  Then  several  centres 
of  ossification  appear  in  various  portions  of  the  membrane  and  grow  quickly,  so  as 
to  protect  the  cerebral  mass,  the  membrane  remaining  between  these  centres  still 
permitting  the  growth  and  expansion  of  the  contents.  Finally,  the  separate  bones 
become  united,  first  at  their  edges,  then  at  their  angles,  to  make  the  complete 
unyielding  bony  cranium. 

Arrest  of  these  processes  at  various  stages  produces  the  equally  various  forms 
of  malformation,  only  a  few  of  which  need  be  mentioned  here.  It  is  to  be  observed 
that,  as  a  rule,  they  affect  that  part  of  the  cranium  that  is  of  membranous  origin,  the 
base  (developed  from  cartilage)  being  much  more  rarely  involved.  Turner  (quoted 
by  Allen)  states  that  this  is  because  the  areas  of  the  different  bones  are  less  precisely 
defined,  and  because  the  process  of  ossification  is  more  liable  to  disturbance  in  mem- 
brane than  in  cartilage. 

In  some  cases  the  whole  calvaria  may  be  lacking  and  represented  only  by  a 
membrane.  Fissures  extending  from  the  margins  of  the  bones  towards  the  centres 
may  exist,  especially  in  the  frontal  and  parietal  bones,  and  may  be  mistaken  for 
fractures.  Other  irregular  gaps  filled  with  membrane  may  be  found,  and  are  gen- 
erally situated  at  or  near  the  natural  foramina  for  vessels.  The  ossification  of  the 
bones  may  be  so  incomplete  as  to  constitute  what  is  called  aplasia  cranii  co7igenita, 
a  condition  in  infants  due,  usually,  to  maternal  cachexia,  and  characterized  by  the 
absence  of  bone  either  in  localized  patches  or  at  points  scattered  over  the  entire 
calvaria. 

The  non-closure  of  the  sutures,  or  defective  development,  may  be  followed  by 
protrusion  of  the  dura  mater,  either  with  or  without  part  of  the  brain,  constituting  a 
meningocele  if  the  protrusion  consists  only  of  the  membranes  and  cerebro-spinal 
fluid  ;  an  encephalocele  if  it  contains  brain  ;  or  a  hydrencephalocele  if  the  contained 
brain  is  distended  by  an  excess  of  ventricular  fluid. 

These  protrusions,  in  the  order  of  frequency,  occur  (<z)  in  the  occipital  region  ; 
(<£)  at  the  fronto-nasal  junction  ;  (c)  in  the  course  of  the  sagittal,  lambdoidal,  and 
other  sutures  ;  (d)  at  the  anterior  or  lateral  fontanelles,  and  at  the  base  of  the  cranium, 
entering  the  orbit,  nose,  or  mouth  through  normal  or  abnormal  openings. 

In  hydrocephalus  there  are  practically  always  atrophy  and  thinning  of  the 
cranium.  ' '  The  deformities  of  hydrocephalus  are  largely  determined  by  the  con- 
dition of  the  sutures  at  the  time  of  the  occurrence  of  the  disease.  Fixation  at  the 
line  of  the  sagittal  suture  causes  bulging  at  the  forehead  and  the  occiput.  Fixation 
at  both  the  lambdoidal  and  the  sagittal  sutures  causes  vertical  bulging  at  the  line  of 
the  coronal  suture  and  enormous  increase  of  the  ascending  portion  of  the  frontal 
bone.  Should  the  intracranial  pressure  announce  itself  prior  to  the  closure  of  any 
of  the  sutures  of  the  vertex,  the  several  bones  composing  it  become  widely  separated 
and  the  fontanelles  enormously  increased  in  size"  (Allen). 

In  microcephalus  there  is  diminution  in  the  size  of  the  cranium  and  of  its  cavity, 
due  to  premature  ossification  of  the  sutures.  The  subjects  of  microcephalus  are 
usually  idiotic.  The  operation  of  "linear  craniotomy,"  by  which  a  strip  of  bone  is 
excised  on  either  side  of  the  median  line  of  the  cranium,  was  intended  to  permit  of 
the  expansion  of  the  brain  in  such  cases.  It  has  not  established  itself  in  surgical 
favor.  The  arrested  growth  of  the  skull  is  thought  to  be  due  to  the  arrested 
development  of  the  brain,  and  not  vice  versa.  The  skulls  of  idiots,  even  when  not 
markedly  microcephalic,  approximate  in  many  ways  to  those  of  the  lower  animals, 


236  HUMAN    ANATOMY. 

and  form  a  distinct  type  characterized  by  the  proportionate  largeness  of  the  facial 
bones,  the  contraction  of  the  brain-case,  especially  in  front  and  above,  the  upward 
slant  of  the  occipital  bone  between  the  foramen  magnum  and  the  occipital  crest,  the 
projection  backward  of  the  frontal  bone  between  the  parietals  at  the  situation  of  the 
anterior  fontanelle,  and  by  many  minor  peculiarities. 

In  spite  of  these,  however,  they  are  easily  referred  to  the  human  species  by  the 
descent  of  the  cranial  cavity  below  the  level  of  the  glenoid  fossa,  the  number  of  the 
nasal  bones,  the  shape  of  the  jaws,  the  number  and  direction  of  the  teeth,  etc. 

Cretinism  is  said  to  be  associated  with  initial  deformities  of  the  base  pertaining 
to  errors  of  development  and  trophic  changes  in  the  bones  arising  from  cartilage, 
especially  the  basilar  process  of  the  occipital  and  the  body  of  the  sphenoid. 
Accessory  to  these  deviations,  and  in  a  measure  dependent  upon  them,  are  the 
modified  facial  proportions  and  dental  irregularity  of  cretins. 

The  Wormian  bones,  ' '  detached  centres  of  ossification  in  the  marginal  area  of 
growing  membrane  bones,  which  they  aid  in  occupying  intervening  spaces  among 
the  bones  themselves,"  have  been  depressed  in  injuries  of  the  skull,  and  have 
resembled  fragments  of  bone  pressing  against  the  meninges.  The  edge  of  such  a 
bone  has  been  mistaken  for  a  line  of  fracture.  The  most  frequent  cause  of  the 
formation  of  Wormian  bones  is  the  stretching  of  the  membranous  envelope  of  the 
cranial  cavity  which  occurs  in  hydrocephalus,  assistance  in  the  completion  of  the 
cranial  cavity  being  supplied  by  Wormian  bones,  which  may  form  in  numbers,  espe- 
cially along  the  sagittal,  lambdoidal,  and  squamous  sutures. 

The  fact  that  in  development  the  cranial  bones  touch  first  and  unite  first  at  the 
points  nearest  their  centres  of  ossification  explains  the  formation  and  situation  of  the 
fontanelles.  The  four  sides  of  each  parietal  bone,  for  example,  become  united  to  the 
four  surrounding  bones  earlier  in  the  middle  than  at  the  four  angles.  At  the  latter, 
therefore,  there  remain  spaces  covered  with  membrane. 

The  anterior  fonta?ielle,  at  the  junction  with  the  frontal  of  the  antero-superior 
angles  of  the  parietal,  is  the  largest,  and  is  not  closed  for  from  one  to  two  years  after 
birth.  In  rickets  its  closure  is  much  retarded.  Its  condition,  as  to  fulness  or  the 
reverse,  gives  a  valuable  indication  in  many  of  the  diseases  of  children.  In  a  state 
of  health,  the  opening,  while  still  membranous,  is  level  with  the  cranial  bones  or  is 
very  slightly  depressed.  Systemic  exhaustion,  malnutrition,  diseases  associated 
with  depletion  of  the  vascular  system,  gastric  catarrh,  chronic  diarrhcea,  and  maras- 
mus, or  simple  atrophy,  all  produce  a  marked  depression  of  the  fontanelle,  which  in 
the  great  majority  of  cases  indicates  feeding  and  stimulation. 

A  bruit  de  souffle  of  greater  or  less  intensity,  and  synchronous  with  the  pulse,  is 
often  heard  over  the  anterior  fontanelle,  and  was  at  one  time  thought  to  be  charac- 
teristic of  rickets  and  of  hydrocephalus,  but  has  little  diagnostic  significance. 

The  thickness  of  the  skull  varies  in  individuals,  in  the  various  portions  of  the 
skull,  and  often  even  in  the  two  halves  of  the  same  skull. 

Humphry  observes  that,  as  he  has  often  found  the  skull  to  be  thick  in  idiots, 
and  the  several  bones  to  be  thickest  when  the  skull  is  small, — i.e.,  when  the  brain  is 
small, — ' '  the  term  '  thick-headed, '  as  a  synonym  for  '  stupid, '  derives  some  confirma- 
tion from  anatomy. ' '  Anderson  says,  however,  that  the  weight  of  the  brain  does 
not  seem  to  have  any  relation  to  the  thickness  of  the  skull,  although  this  does  not 
affect  the  truth  of  the  statement  that  as  the  brain  diminishes  with  age  the  skull  is  apt 
to  thicken,  the  addition  of  bone  taking  place  on  the  interior  and  giving  rise  to  the 
irregular  surface  with  close  dural  adhesions  often  met  with  in  operations  upon  the 
cranium  in  old  persons. 

The  middle  cerebral  fossa,  the  centre  of  the  squamous  portion  of  the  temporal, 
and  the  middle  of  the  inferior  occipital  fossae  are  the  thinnest  parts  of  the  skull, 
varying  from  1.75  millimetres  to  .85  of  a  millimetre,  and  in  exceptional  skulls  meas- 
uring only  .  2  millimetre  in  thickness.  This  has  an  important  bearing  on  the  location 
of  fractures  (page  239).  At  the  parietal  eminence,  the  posterior  superior  angle  of 
the  parietal,  the  superior  angle  of  the  occipital,  and  especially  at  the  frontal  eminences 
and  the  occipital  protuberance  areas  of  thickening  are  found  ;  at  the  latter  point  the 
skull  may  measure  fifteen  millimetres  in  thickness  (Anderson).  The  average  thick- 
ness of  the  remaining  parts  of  the  calvaria  is  from  five  to  7.5  millimetres. 


PRACTICAL   CONSIDERATIONS:    THE   SKULL.  237 

In  trephining  these  general  facts  should  be  remembered,  as  should  the  occa- 
sional want  of  parallelism  between  the  inner  and  outer  tables. 

The  shape  of  the  skull  is  influenced  by  race  and  by  disease.  The  racial  pecu- 
liarities have  sometimes  a  medico-legal  significance,  but  cannot  be  described  here. 
(See  also  page  229.)      Pathological  asymmetry  is  caused  in  many  ways. 

In  rickets  the  head  is  enlarged,  and  this  enlargement  seems  greater  than  it 
really  is  on  account  of  the  retarded  growth  of  the  facial  bones..  All  the  fontanelles 
are  larger  than  usual  and  close  later.  The  anterior  fontanelle  is  sometimes  patent 
at  the  end  of  the  third  or  fourth  year. 

In  craniotabes  the  rhachitic  softening  of  the  bones  favors  absorption  under 
pressure.  Consequently  the  regions  most  affected  by  the  thinning  of  the  bones  are 
the  occipital  and  the  posterior  half  of  the  parietal,  which  are  between  two  forces, — 
the  expanding  and  growing  brain  within  and  the  supporting  surface,  as  the  pillow, 
without.      Various  peculiar  shapes  may  result. 

The  changes  in  hydrocephalic  and  microcephalic  skulls  have  already  been 
described. 

Syphilis  in  the  young  affects  especially  the  fronto-parietal  region,  producing 
thickening  or  nodes  of  those  bones  in  the  vicinity  of  the  anterior  fontanelle.  This 
site  is  probably  determined  by  the  vascularity  accompanying  growth,  as  this  is  the 
last  portion  of  the  cranium  to  become  bony.  Such  nodes  are,  therefore,  analogous 
to  the  rings  or  collars  that  form  in  the  long  bones  of  syphilitic  children  near  the 
epiphyses  ;  the  immobility  of  the  cranial  bones,  however,  causes  the  exudate  to 
harden  rather  than  to  take  on  inflammatory  action.  The  bulging  of  the  forehead  in 
some  hereditary  syphilitics  is  due  to  the  catarrh  of  the  frontal  sinuses  which  often 
accompanies  the  Schneiderian  catarrh,  that  produces  first  the  so-called  "snuffles" 
and  later  caries  of  the  nasal  bones,  with  the  characteristic  flattening  of  the  nose. 

In  adults  syphilis  of  the  cranium  usually  causes  necrosis,  spreading  from  the 
external  to  the  internal  table.  Necrosis  from  whatever  cause  is  more  apt  to  affect 
the  external  table,  which  is  more  exposed  to  injury  and  less  richly  supplied  with 
blood. 

The  calvaria  is  far  more  frequently  attacked  by  disease  than  the  base,  doubt- 
less from  its  greater  liability  to  traumatism. 

The  bones  of  the  cranium  are  supplied  with  blood  by  arteries  entering  from  the 
pericranium  on  one  side  and  from  the  dura  mater  on  the  other.  The  dural  supply 
is  the  larger  ;  hence  the  foramina  on  the  inside  of  the  cranium  are  larger  and  more 
numerous  than  those  on  the  exterior,  and  hence  also  traumatic  detachment  of  the 
pericranium  over  considerable  areas  may  not  result  in  necrosis.  When  detached 
from  disease,  the  latter  (as  in  syphilis),  even  when  originating  externally,  is  apt  to 
spread  along  the  vessels,  and  thus  cause  necrosis  by  finally  affecting  the  dural  supply. 

The  meningeal  blood-vessels  running  on  the  exterior  surface  of  the  dura — the 
remnant  of  the  primitive  membranous  cranium  (Humphry) — and  sending  branches 
to  the  cranium  are  not  very  strong,  and  consequently  do  not  offer  much  resistance 
to  the  separation  of  the  dura  from  the  skull  ;  neither  do  their  branches  furnish  a 
very  large  quantity  of  blood,  surgically  considered.  It  follows  that  a  traumatic 
separation  of  the  dura  is  not  in  itself  a  lesion  followed  by  serious  consequences, 
unless  the  separation  takes  place  at  or  about  the  situation  of  the  main  trunks. 
Hence,  when  an  extradural  clot  is  suspected  to  be  the  cause  of  grave  symptoms,  it 
is  usually  sought  for  first  over  the  anterior  inferior  angle  of  the  parietal  bone, — i.e. , 
about  three  centimetres  (approximately  one  inch  and  a  quarter)  behind  the  external 
angular  process  on  a  level  with  the  upper  border  of  the  orbit.  This  will  make 
accessible  the  region  of  the  main  trunk  and  the  anterior  branch  of  the  middle 
meningeal.  This  latter  branch  at  this  point  runs  through  a  bony  canal  on  the  inner 
surface  of  the  cranium,  and  is  therefore  frequently  torn  when  fracture  occurs  in  this 
region.  An  opening  on  the  same  level,  but  just  below  the  parietal  eminence,  will 
permit  the  posterior  branch  to  be  reached. 

The  venous  channels  (emissary  veins)  connecting  the  sinuses  within  and  the 
superficial  veins  without  the  cranium  sometimes  convey  infective  disease,  such  as 
erysipelas  or  cellulitis  of  the  scalp,  and  thus  bring  about  a  septic  meningitis  or  sinus 
thrombosis. 


238 


HUMAN   ANATOMY. 


The  time-honored  custom  of  blistering  or  leeching  behind  the  ear  in  intra- 
cranial inflammations  rests  on  the  fact  that  the  largest  emissary  vein  is  the  mastoid, 
traversing  the  mastoid  foramen  and  connecting  the  lateral  sinus  with  an  occipital 
vein  or  with  the  posterior  auricular.  (For  further  discussion  of  these  channels  of 
communication,  see  the  section  on  the  Venous  System. ) 

While  the  spinal  dura  mater  has  no  intimate  connection  with  the  inner  surfaces 
of  the  vertebrae  (being  separated  from  the  arches  by  adipose  tissue  and  from  the 
bodies  by  the  posterior  ligament),  the  dura  mater  of  the  cranium  becomes  closely 
attached  to  the  bones,  especially  at  the  base,  where  it  adheres  tightly  to  the  many 
ridges  and  prominences  and  to  the  edges  of  the  foramina  which  transmit  the  nerves 
and  vessels.  To  the  sides  and  summit  of  the  skull  the  dura  is  less  closely  attached  ; 
hence  in  fractures  at  the  base  the  dura  is  generally  torn,  and  the  risk  both  of 
serious  hemorrhage  and  of  infection  is  thereby  increased,  while  in  fracture  of  the 
calvaria  it  much  oftener  escapes. 

Fractures  of  the  Cranium. — That  fractures  in  this  region  are  not  vastly 
more  frequent  is  due  to  various  factors  ;  among  them  are  the  rounded  shape  of  the 

calvaria,  causing  blows  to  glance  off  ;  the 
division  of  the  separate  bones  into  inner  and 
outer  tables,  with  the  comparatively  spongy 
diploe  intervening;  and  the  curved  thicken- 
ings which,  like  buttresses,  strengthen  the 
skull  externally,  and  extend  on  each  side 
through  the  supra-orbital  ridge  and  the 
upper  border  of  the  temporal  fossa  to  the 
mastoid  process  and  thence  to  the  occipital 
tuberosity.  From  this  latter  point  on  the 
inner  surface  other  ridges,  like  the  groining 
of  a  roof,  run  forward  in  the  median  line  to  the  frontal  bone,  downward  to  the  foramen 
magnum,  and  laterally,  on  either  side  of  the  groove  for  the  lateral  sinus,  extend  to 
the  mastoid.  In  very  young  persons  the  dome  of  the  skull  is  made  up  of  three  dis- 
tinct arches  composed  of  the  occipital,  the  frontal,  and  the  parietal  bones.  In  child- 
hood the  centre  (the  most  prominent  portion)  of  each  of  these  bones  is,  on  account 
of  early  ossification,  thicker  than  the  rest,  while  the  edges  are  connected  by  mem- 
brane and  are  comparatively  movable.  These  mechanical  conditions,  together  with 
the  elasticity  of  the  individual  bones  in  young  persons,  make  fractures  of  the  skull  in 
them  comparatively  rare. 

In  the  adult  the  membranous  layer  between  the  sutures  becomes  thinner  or  disap- 
pears and  the  bones  denser  and  less  elastic  ;  they  are,  therefore,  more  easily  fractured. 
The  two  tables  may  be  broken  separately,  although  this  is  rare.  In  almost  all 
cases  in  which  fracture  is  complete  the  inner  table  suffers  more  than  the  outer. 
This  is  because  (a)  it  is  more  brittle  ;  (3)  the  fibres  on  the  side  of  greatest  strain 
suffer  most  (as  in  "green-stick"  fracture)  ;  (c)  the  material  carried  inward  from 
without  is  greater  at  the  level  of  the  inner  table  than  at  the  point  of  application  of 
the  external  force. 

Agnew  explains  this  diagrammatically  as  follows  : 


Section  of  frontal  bone,  natural  size,  showing  rela- 
tion of  external  and  internal  tables  of  compact  bone  to 
intervening  diploe. 


AB  represents  a  section  of  the  arch  of  the  skull.  CD  and  EF  represent  the  lines 
of  a  vertical  force  applied  about  G.  The  effect  is  to  flatten  the  curve  so  that  it  is 
as  HI,  while  at  the  same  time  the  vertical  lines  diverge  (JK  and  LM)  and  the  particles 
of  bone  in  the  external  table  tend  to  be  forced  together  at  N  and  separated  or  burst 
apart  at  O. 


PRACTICAL    CONSIDERATIONS  :    THE    SKULL 


239 


Force  applied  to  the  vertex  would  tend  to  drive  apart  the  lower  borders  of  the 
parietal  bones,  but  the  bases  of  the  great  arch  formed  by  these  bones  are  overlapped 
by  the  squamous  portions  of  the  temporal,  and  thus  this  outward  thrust  is  prevented. 
If  the  force  be  applied  to  the  frontal  bone,  as  it  overlaps  the  parietals  at  the  middle 
of  the  coronal  suture,  it  is  transmitted  to  them  and  is  resisted  by  the  same  mechanism. 
The  occipital  bone  and  the  bones  at  the  sides  of  the  skull  (beneath  the  level  of  the 
ridges  that  have  been  described)  break  more  easily,  as  they  are  thinner,  the  diploe 
is  less  developed,  and  the  two  tables  are  more  closely  united  (Humphry);  but 
from  their  situation  they  are  less  exposed  to  injury,  and  are  protected  by  a  thicker 
covering  of  soft  parts. 

Fractures  of  the  base  are  usually  due  to  indirect  violence.  They  may  result 
from  foreign  bodies  thrust  through  the  nose,  orbit,  or  pharynx  ;  or  from  a  blow 
upon  the  nose  acting  through  the  bony  septum  to  produce  fracture  of  the  cribriform 
plate  of  the  ethmoid  ;  or  through  a  blow  or  fall  upon  the  point  of  the  chin,  driving 
the   condyles  of  the  inferior  maxilla  into 

the  cranium.    As  a  rule,  however,  the  force  Fig.  264. 

traverses  the  vault  or,  more  rarely,  the 
spinal  column  (as  in  falls  upon  the  feet  or 
buttocks). 

Fractures  of  the  base  are  very  frequent 
for  several  reasons.  The  large  expanse  of 
bone  forming  the  vault  is  contracted  at  the 
base  into  three  comparatively  narrow  por- 
tions, which  descend  in  successively  lower 
planes  from  before  backward,  but  which 
all  have  relatively  thin  floors,  on  which  the 
force  received  at  a  distant  portion  of  the  cra- 
nium is  ultimately  expended.  This  impact 
reaches  the  base  by  the  shortest  route,  so 
that  a  blow  of  sufficient  violence  upon  the 
frontal  bone  will  fracture  the  orbital  plates  in 
the  anterior  cerebral  fossa;  upon  the  vertex, 
the  petrous  portion  of  the  temporal  and 
the  floor  of  the  middle  fossa  ;  and  upon 
the  occiput,  the  floor  of  the  posterior  or 
cerebellar  fossa.  Furthermore,  the  base 
is  provided  with  a  series  of  well-marked 
ridges    which    aid   in  the    transmission  of 

force  and  which  fade  away  into  the  vault.  Base  of  skull  from  above,  showing  linesof  fractures. 

The  anterior  ridges  are  gathered  into 
the  lesser  wing  of  the  sphenoid  and  end  at  the  sides  of.  the  anterior  clinoid  process. 

The  middle  group,  collected  into  the  petrous  portion  of  the  temporal  bone, 
passes  to  the  centre  of  the  base  of  the  skull  and  terminates  at  the  foramen  lacerum 
medium. 

The  ridges  of  the  posterior  group,  meeting  at  the  torcular  Herophili,  continue 
to  the  foramen  magnum,  at  the  posterior  limit  of  which  they  divide  and  pass  for- 
ward to  meet  again  in  the  basilar  process,  and  end  in  the  posterior  clinoid  process. 
The  region  of  the  sella  turcica  is  therefore  the  centre  of  resistance  to  the  transmis^ 
sion  of  forces  from  the  vault  to  the  base.  This  is  well  surrounded  by  fluid,  and  the 
vibrations  which  are  concentrated  here  may  thus  become  lost  in  the  fluid  without 
injuring  the  brain-substance. 

The  region  of  the  middle  fossa  suffers,  however,  most  frequently  because  :  1.  It 
is  connected  (by  the  fronto-sphenoidal  and  petro-occipital  sutures)  with  both  the 
other  fossa;,  and  hence  often  participates  in  their  injuries.  2.  It  is  intrinsically  one 
of  the  weakest  parts  of  the  skull,  on  account  of  the  presence  of  the  foramina  lacera, 
the  carotid  grooves,  the  hollows  for  the  pituitary  body,  the  depression  for  the  sphe- 
noidal sinus,  the  petro-sphenoidal  suture,  and  the  thin  walls  of  the  tympanum,  of 
the  external  auditory  canal,  and  of  the  temporal  fossa.  Moreover,  just  in  front  of 
this  region  the  descending   pterygoid    processes  and   the  lower  jaw  reinforce  the 


240  HUMAN    ANATOMY. 

cranium  proper,  while  behind  it  are  the  thickening  of  the  basilar  process  and  the 
posterior  clinoid  plate  (Humphry)  (Fig.  254). 

The  differential  symptoms  of  fracture  through  the  floors  of  these  fossae  are 
determined  by  their  anatomical  relations.      They  are  as  follows  : 

1.  Anterior  Cerebral  Fossa. — (a)  Epistaxis  when  the  Schneiderian  membrane 
and  the  dura  and  arachnoid  are  torn.  It  should  not  be  forgotten  that  the  blood  may 
come  from  the  mucous  membrane  alone.  (<£)  Loss  of  smell  from  injury  to  the 
olfactory  bulbs  resting  on  the  cribriform  plate,      (c)   Subconjunctival  ecchymosis. 

The  blood  is  usually  derived  from  the  meningeal  vessels  over  the  orbital  plates, 
but  in  bad  cases  may  come  from  the  ophthalmic  artery,  ophthalmic  vein,  or  cavern- 
ous sinus.  If  the  body  of  the  sphenoid  is  fractured,  the  blood  may  find  its  way 
through  the  sphenoidal  sinuses  into  the  pharynx  and  stomach,  and  then  be  vomited, 
giving  rise  to  a  mistaken  diagnosis  of  gastric  injury. 

2.  Middle  Cerebral  Fossa. — («)  Hemorrhage  from  the  ear.  This  may  be 
merely  from  a  torn  tympanic  membrane,  (b)  Escape  of  cerebro-spinal  fluid  from 
the  ear.  This  indicates  that  the  petrous  portion  of  the  temporal  is  broken,  the  dura 
mater  and  the  arachnoid  torn,  and  the  membrana  tympani  ruptured.  If  the  latter 
escapes  injury,  the  fluid  may  trickle  into  the  throat  through  the  Eustachian  tube. 
(c)  In  rare  and  very  severe  cases  the  lateral  sinus  has  been  opened  or  the  internal 
carotid  torn,      (d)  There  may  be  deafness  or  facial  paralysis,  or  both. 

3.  Posterior  or  Cerebellar  Fossa. — (a)  Hemorrhage  into  the  pharynx  if  the 
basilar  process  is  involved  and  the  pharyngeal  mucous  membrane  torn,  (b)  Ecchy- 
mosis at  the  nape  of  the  neck  and  about  the  mastoid. 

Of  course  the  characteristic  symptoms  of  any  two  or  even  of  all  three  of  these 
injuries  may  be  commingled  if  the  fracture  is  extensive  enough. 

Just  as  fractures  would  be  more  frequent  were  it  not  for  the  mechanism  that  has 
been  described,  so  concussion  or  laceration  of  the  by'ain  would  occur  far  oftener 
were  it  not  for  certain  factors,  among  which  are  the  different  strata  of  varying 
density  intervening  between  the  brain  and  the  outer  surface  of  the  scalp.  The  soft 
diploe  and  the  dense  inner  "vitreous"  table  both  tend  to  diminish  shock  to  the 
brain,  the  former  by  arresting  vibrations  and  the  latter  by  lateralizing  them.  The 
eminences  on  the  inner  surface  of  the  skull  project  into  the  spaces  between  the  great 
divisions  of  the  brain,  where,  in  places,  there  is  more  subarachnoid  fluid  than  else- 
where ;  such  elevations  are  intimately  connected  at  their  edges  and  terminal  points 
with  the  strong  expansions  of  the  dura  mater, — the  falx  and  the  tentorium, — which 
still  further  take  up  and  distribute  the  final  vibrations.  "  Thus  there  is  every  facility 
for  causing  jarring  impulses  to  deviate  from  the  direct  line  and  take  a  circumferential 
route,  in  which  they  are  gradually  weakened  and  rendered  harmless"  (Humphry). 

The  conditions  tending  to  minimize  the  effects  of  violence  inflicted  upon  the 
skull  are  thus  summarized  by  Jacobson  :  "  ( 1 )  The  density  and  mobility  of  the 
scalp.  (2)  The  dome-like  shape  of  the  skull.  This,  like  an  egg-shell,  is  calculated 
to  bear  hard  blows  and  also  to  allow  them  to  glide  off.  (3)  Before  middle  life  the 
number  of  bones  tends  to  break  up  the  force  of  a  blow.  (4)  The  sutures  interrupt 
the  transmission  of  violence.  (5)  The  internal  membrane  (remains  of  fcetal  peri- 
osteum) acts  in  early  life  as  a  linear  buffer.  (6)  The  elasticity  of  the  outer  table. 
(7)  The  overlapping  of  some  bones, — e.g. ,  the  parietal  by  the  squamous  ;  and  the 
alternate  bevelling  of  adjacent  bones, — e.g. ,  at  the  coronal  suture.  (8)  The  pres- 
ence of  ribs  or  groins, — e.g. ,  (a)  from  the  crista  galli  to  the  internal  occipital  pro- 
tuberance ;  ($)  from  the  root  of  the  nose  to  the  zygoma  ;  (c)  the  temporal  ridge 
from  orbit  to  mastoid  ;  (d)  from  mastoid  to  mastoid  ;  (e)  from  the  external  occipital 
protuberance  to  the  foramen  magnum.  (9)  Buttresses, — e.g.,,  malar  and  zygomatic 
processes,  and  the  greater  wing  of  the  sphenoid.  (10)  The  mobility  of  the  head 
upon  the  spine." 

Landmarks. — The  prominence  of  the  occiput,  of  the  parietal  region,  or  of  the 
frontal  eminence  indicates  in  a  general  way  the  development  of  the  corresponding 
portions  of  the  brain. 

The  terms  used  to  designate  particular  points  on  the  skull  have  already  been 
described  (page  228);  additional  attention  may  here  be  paid  to  those  of  especial 
importance  as  landmarks. 


PRACTICAL    CONSIDERATIONS  :    THE    SKULL. 


241 


The  inion  or  external  occipital  protuberance,  which  approximately  corresponds 
to  the  point  of  convergence  of  five  sinuses  (the  superior  longitudinal,  the  two  lateral, 
the  straight,  and  the  occipital),  is  easily  felt  in  the  mid-line  behind.  The  superior 
curved  lines  which  run  outward  from  this  point  indicate  the  muscular  origin  of  the 
occipito-frontalis,  and  hence  are  often  the  lower  limit  of  effusions  beneath  the 
aponeurosis.  These  ridges  indicate  approximately  the  course  of  the  lateral  sinuses, 
which  are  on  a  line  drawn  from  the  inion  to  the  superior  border  of  the  mastoid 
apophysis, — i.e. ,  to  a  point  about  2.5  centimetres,  or  one  inch,  behind  the  external 
auditory  meatus. 

The  asterion  or  junction  of  the  squamous  and  lambdoid  sutures  is  12.5  milli- 
metres, or  half  an  inch,  above  and  18.5  millimetres,  or  three-quarters  of  an  inch, 
behind  the  upper  level  of  the  posterior  border  of  the  mastoid.  A  line  from  the 
asterion  to  the  inion  is  therefore  also  the  line  of  the  lateral  sinus. 

The  lambda,  the  junction  of  the  lambdoid  and  sagittal  sutures,  lies  in  the  median 
line  posteriorly  about  seventy  millimetres,  or  two  and  three-quarters  inches,  above 
the  inion.      In  early  life  the  posterior  fontanelle  is  found  at  that  point. 


Fig.  265. 

Bregma   Biauricular  line 

-A. 


{i|/ — Occipital  point 


Mental  point 


Gonion 
Lateral  aspect  of  the  skull,  showing  the  various  points.     (See  also  description  on  page  22S.) 


The  bregma,  the  junction  of  the  coronal  and  sagittal  sutures  (and  in  childhood 
of  the  frontal  suture),  marks  the  position  of  the  anterior  fontanelle,  and  is  found  a 
little  anterior  to  the  centre  of  the  shortest  line  that  can  be  drawn  over  the  vertex 
between  the  two  external  auditory  meatuses. 

The  pterion  is  the  point  of  junction  of  the  temporal,  sphenoid,  frontal,  and 
parietal  bones.  It  is  from  thirty  to  thirty-eight  millimetres,  or  one  and  a  quarter 
to  one  and  a  half  inches,  above  the  zygoma,  and  the  same  distance  behind  the 
external  angular  process  of  the  frontal.  It  represents  the  position  of  the  trunk  and 
of  the  large  anterior  branch  of  the  middle  meningeal  artery. 

The  zygoma  can  easily  be  traced  from  its  anterior  to  its  posterior  extremity. 

The  temporal  ridges  can  often  be  felt  as  two  curved  lines,  the  upper  one  mark- 
ing the  attachment  of  the  temporal  fascia  and  the  lower  one  that  of  the  muscle. 
They  indicate  the  upper  boundary  of  the  temporal  fossa,  and  often  limit  the  spread 
of  effusions  or  the  growth  of  tumors. 


242  HUMAN   ANATOMY. 

The  course  of  the  longitudinal  sinus  is  indicated  by  a  line  drawn  from  the 
nasion  (the  junction  of  the  nasal  and  frontal  bones)  to  the  inion. 

The  lateral  sinus  is  irregular  in  its  course  (page  234).  According  to  Macewen, 
it  may  be  fairly  indicated  by  the  two  following  lines  :  ' '  The  first  from  the  asterion  to 
the  superior  margin  of  the  external  osseous  meatus,  of  which  line  the  posterior  two- 
thirds  correspond  to  the  upper  part  of  the  sigmoid  groove,  which  is  also  the  more 
superficial.  The  second  line  from  the  parieto-squamo-mastoid  junction  to  the  tip  of 
the  mastoid  process  corresponds  in  its  upper  two-thirds  to  the  vertical  part  of  the 
sigmoid  groove.  The  knee  of  the  sigmoid — its  most  anterior  convexity — is  variable 
in  its  position,  but  is  generally  on  a  level  with  the  upper  part  of  the  external  osseous 
meatus.  The  sigmoid  groove  is  situated  at  a  variable  distance  from  the  external 
auditory  meatus,  the  tympanum,  and  the  exterior  of  the  skull.  The  distance 
between  the  external  osseous  meatus  and  the  sigmoid  groove  varies  from  one  or  two 
to  thirteen  millimetres." 

The  frequency  with  which  infective  thrombosis  of  the  lateral  sinuses  occurs  as 
a  complication  of  middle  ear  disease  renders  the  topographical  anatomy  of  these 
sinuses  and  the  associated  region  of  the  skull  of  great  practical  importance. 

The  suprameatal  triangle  is  formed  by  the  posterior  root  of  the  zygoma  running 
somewhat  horizontally  above,  the  portion  of  the  descending  plate  of  the  squamous 
which  forms  the  arch  of  the  osseous  part  of  the  external  auditory  meatus  below,  and 
a  base  line  uniting  the  two,  dropped  from  the  former  on  a  level  with  the  posterior 
border  of  the  external  auditory  meatus.  At  this  point  there  is  usually  a  depression 
in  the  bone,  though  occasionally  there  is  a  slight  prominence  as  if  the  antrum  had 
bulged  at  that  point.  The  apex  of  this  triangular  depressed  area  points  forward 
(Macewen).      The  mastoid  antrum  may  be  reached  through  this  triangle. 

(The  relations  of  this  antrum,  the  facial  canal,  and  the  lateral  sinus  to  one 
another,  to  the  temporo-sphenoidal  lobe,  and  to  the  surface  of  the  skull  will  be 
considered  in  connection  with  the  general  subject  of  Cranio- Cerebral  Topography, 
page  1 214.) 

The  size  and  extent  of  the  frontal  sinuses  vary,  as  described  on  page  234. 
The  communication  of  these  sinuses  with  the  nose  accounts  for  the  frontal  headache 
in  ozaena,  and  the  fact  that  a  patient  with  a  compound  fracture  opening  up  the 
sinuses  can  blow  out  a  flame  held  close  by.  The  frontal  sinuses  may  be  occu- 
pied by  bony  or  other  tumors  ;  emphysema  may  result  from  fracture  of  the  sinus 
wall  ;  insects  may  gain  access  to  these  cavities  and  give  rise  to  infection  or  to 
epistaxis  ;  infective  inflammations  of  the  nose  and  naso-pharynx  may  involve  the 
sinuses. 

The  sphenoidal  sinuses  are  less  important  surgically,  but  these  points  should  be 
■  remembered  :  ( 1 )  fracture  through  them  may  lead  to  bleeding  from  the  nose,  which 
is  thus  brought  into  communication  with  the  middle  fossa  ;  (2)  the  communication 
of  their  mucous  membrane  with  that  of  the  nose  may  explain  the  inveteracy  of  cer- 
tain cases  of  ozaena  ;  (3)  here  and  in  the  frontal  sinuses  very  dense  exostoses  are 
sometimes  formed  (Jacobson). 

The  Face. — The  nasal  bones  are  so  joined  together  as  to  form  a  strong  arch 
resting  upon  the  nasal  processes  of  the  superior  maxillary  bones.  They  are  sel- 
dom dislocated,  because  this  line  of  union  is  one  in  which  there  is  an  alternation 
in  the  bevelling  of  the  sutures  (similar  to  that  between  the  frontal  and  parietal 
bones).  Thus  the  lower  portion  of  the  nasal  bones  overlaps  the  maxillary,  while 
nearer  the  root  of  the  nose  the  latter  is  external.  The  line  between  the  bones 
and  the  nasal  cartilages  can  easily  be  felt.  The  skin  is  very  tightly  attached  to 
the  cartilages. 

The  upper  or  frontal  portion  of  these  bones  is  very  strong,  and  will  resist  a 
great  degree  of  force  without  fracture.  The  lower  portion  is  most  frequently  broken, 
usually  within  a  half-inch  of  the  lower  margin. 

The  resulting  deformity  is  usually  lateral,  but  if  the  perpendicular  plate  of  the 
ethmoid  is  broken  the  nose  will  be  depressed.  The  thinness  and  close  application 
of  the  mucous  membrane  to  the  bones  render  these  fractures  almost  invariably  com- 
pound. Emphysema  of  the  cellular  tissue  of  the  face  and  forehead  may  follow  such 
an  injury.     The  vascularity  of  the  bones  leads  to  very  rapid  union,  and  it  is  therefore 


PRACTICAL   CONSIDERATIONS  :    THE   FACE.  243 

important  to  secure  early  reposition  of  the  fragments.  The  relation  of  the  perpen- 
dicular plate  of  the  ethmoid  through  the  crista  galli  to  the  olfactory  bulbs  and  the 
base  of  the  brain  should  be  remembered  in  severe  injuries  to  the  bones  of  the  nose. 
By  reason  of  this  relation  suspension  or  destruction  of  the  sense  of  smell  has  re- 
sulted ;  and  even  septic  meningitis  and  death  have  followed  accidents  in  which  the 
prominent  early  symptom  was  fracture  of  the  nasal  bones. 

The  malar  bones,  binding  together  the  maxillae  and  the  cranium,  are  very  strong, 
and  seldom  broken  unless  by  severe  force  directly  applied. 

Fracture  of  the  body  is  apt  to  run  into  the  orbit,  producing  a  subconjunctival 
ecchymosis  near  the  outer  canthus,  and  there  may  also  be  a  loss  of  sensation  in  some 
of  the  teeth,  the  gums,  the  ala  of  the  nose,  and  a  part  of  the  cheek,  on  account  of 
injury  to,  or  pressure  upon,  the  infra-orbital  branch  of  the  fifth  nerve. 

The  zygomatic  process  is  most  subject  to  fracture  ;  that  part  of  the  arch  which 
is  on  the  temporal  side  of  the  suture  is  much  weaker  and  most  apt  to  give  way. 
The  deformity  may  usually  easily  be  recognized  by  touch.  The  fragments  are 
always  driven  inward,  and  sometimes  become  entangled  in  the  fibres  of  the  tem- 
poral muscles.  The  attachment  of  the  strong  temporal  fascia  to  the  upper  edge  of 
the  zygoma,  and  of  the  masseter  muscles  to  its  lower  edge,  prevents  displacement 
upward  or  downward. 

The  superior  maxilla,  on  account  of  its  very  various  and  complicated  relations 
(being  associated  with  nine  other  bones),  has  considerable  surgical  importance.  Its 
position  in  the  same  vertical  plane  as  the  forehead  (instead  of  in  advance  of  it,  as  in 
the  lower  animals)  indicates  the  limitation  of  its  function  to  mastication,  the  need  for 
its  use  in  prehension  having  disappeared.  Many  of  its  diseases  (infections,  tumors, 
etc. )  originate  in  the  teeth  or  teeth-sockets,  and  may  be  avoided  by  early  atten- 
tion to  these  structures.  Others  arise  by  reason  of  the  contiguity  of  the  maxillary 
antrum  to  the  inferior  turbinated  bone,  the  mucous  membrane  of  which  is  often  the 
subject  of  chronic  catarrh. 

Injuries  of  the  superior  maxilla  causing  fracture  must,  as  a  rule,  be  direct  and 
of  considerable  violence.  The  line  of  fracture  may  involve  the  antrum,  the  nose 
through  the  nasal  process,  the  orbit  through  the  orbital  process,  or  the  mouth 
through  the  alveolar  or  palatine  process.  It  may  also  run  into  the  zygomatic  or  the 
spheno-maxillary  fossa.  The  force  may  be  transmitted  from  the  malar  bone,  or  from 
the  lower  jaw  through  the  teeth. 

The  maxilla  is  very  vascular,  and  hence  recovery  from  even  serious  or  crushing 
injuries  is  apt  to  be  rapid  and  thorough.  Like  the  nasal  bones,  it  has  attached  to 
it  no  muscles  that  can  cause  or  perpetuate  deformity,  and  therefore,  unless  it  is 
comminuted,  its  fragments  will  retain  their  position  when  once  replaced. 

It  is  frequently  affected  by  "phosphorus  necrosis,"  the  osteitis  causing  the  ne- 
crosis being  probably  due  to  the  direct  toxic  action  of  the  phosphorus  fumes  gaining 
access  through  carious  teeth.      This  theory  is  not  undisputed. 

Tumors  involving  the  alveolar  border  show  first  in  the  mouth.  Tumors  of  the 
body  usually  occupy  the  antrum  (maxillary  sinus).  They  are  apt  to  grow  in  every 
direction  except  towards  the  malar  bone,  where  they  meet  with  the  greatest  resist- 
ance. They  accordingly,  produce  prominence  of  the  eye  from  pushing  upward  the 
floor  of  the  orbit,  bulging  of  the  cheek  from  pushing  outward  the  thin  anterior  wall, 
and  depression  of  the  roof  of  the  mouth  from  pressure  upon  the  palatal  plate.  After 
the  anterior  the  most  yielding  wall  of  the  antrum  is  the  orbital. 

Abscess  of  the  antrum  gives  rise  to  the  same  symptoms  when  it  attains  a  large 
size. 

The  relations  of  the  molar  teeth  to  the  floor  of  the  antrum  and  of  the  infra- 
orbital nerve  to  its  roof  account  for  the  toothache  and  facial  neuralgia  that  so  often 
accompany  antral  disease.  It  is  said  to  be  a  fact  that  cystic  distention  does  not 
involve  the  lachrymal  duct,  while  solid  tumors  may  cause  overflowing  of  the  tears 
(Warren-Heath). 

The  chief  deformity  associated  with  the  superior  maxilla  is  cleft  palate,  which 
results  from  a  failure  of  the  palatal  plates  to  unite  in  the  median  line.  The  cleft 
in  the  hard  palate  is  always  median,  but  when  it  reaches  the  alveolus  it  follows  the 
line  of  the  suture  between  the  premaxillary  bone  (os  incisivum)  and  the  superior 


244  HUMAN   ANATOMY. 

maxilla,  ending,  therefore,  opposite  the  space  between  the  lateral  incisor  and  the 
canine.  In  single  harelip,  which  is  often  associated  with  cleft  palate,  and  due  to 
faulty  union  of  the  fronto-nasal  and  maxillary  processes  (page  60 ),  the  gap  is  found 
at  the  same  point,  never  in  the  middle  line.  Sometimes  the  premaxillary  bone, 
which  carries  the  two  upper  central  incisors,  is  left  attached  to  the  nose.  This  con- 
dition is  usually  associated  with  double  harelip.  Cleft  palate  may  involve  only  the 
soft  palate  and  not  the  hard,  but  the  reverse  is  almost  never  true. 

Occasionally  the  identity  of  the  premaxilla  is  established  pathologically. 
Instances  of  exfoliation  of  this  bone  carrying  the  two  incisor  teeth  have  been 
recorded,  not  only  in  children  but  even  in  adults. 

Excision  of  the  superior  maxilla  involves  (the  bone  having  been  exposed  by  a 
suitable  incision  through  the  soft  parts)  the  disjunction  of  (a)  its  connection  with 
the  malar  bone  ;  (J>)  its  nasal  process  from  the  nasal,  lachrymal,  and  frontal  bones  ; 
(t)  its  orbital  plate  from  the  ethmoid,  malar,  lachrymal,  and  palate  bones  ;  (d)  its 
posterior  connection  with  the  pterygoid  processes  and  palate  bone  ;  and  (e)  its 
articulation  with  its  fellow  through  the  palatal  plates  and  its  connection  with  the  soft 
palate. 

These  indications  are  met,  as  a  rule,  by  sawing  through  the  malar  bone  just 
beyond  its  articulation  with  the  maxilla  (so  that  advantage  may  be  taken  of  the 
proximity  of  the  spheno-maxillary  fissure),  dividing  the  nasal  process  a  little  below 
the  junction  with  the  nasal  bones,  sawing  through  the  hard  palate  (from  the  nose 
downward)  at  or  beyond  the  median  line,  dividing  the  orbital  plate  with  a  fine 
chisel  (or  leaving  it  to  be  brought  away  at  the  last  step),  and,  finally,  wrenching 
the  bone  away  from  its  attachment  to  the  pterygoid  processes  (and  the  orbit)  by 
means  of  a  pair  of  lion-forceps.  The  hinder  wall,  in  contact  with  the  palate  bone, 
is  very  thin,  and  may  give  way  and  remain  behind  at  this  stage.  This  is  most  likely 
to  happen  when  it  is  most  undesirable, — i.e. ,  when  the  operation  is  performed  for 
malignant  disease. 

The  inferior  maxilla,  the  only  bone  of  the  skull  which  is  movable  upon  the 
others,  is  especially  dense,  so  that  it  may  be  strong  enough  to  withstand  the  very 
considerable  force  which  its  muscles  exert  upon  it  in  mastication.  It  is,  therefore, 
not  easily  divided  in  operations.  The  alveolar  processes  are  thicker  and  stronger 
than  those  of  the  upper  jaw,  and  more  force  is,  therefore,  usually  required  to  extract 
a  tooth  ;  hence  damage  to  the  bone  through  rough  or  unskilful  effort  at  extraction 
is  more  frequent  in  the  lower  than  in  the  upper  jaw.  The  last  molar,  or  wisdom 
tooth,  is  often  a  cause  of  trouble,  owing  to  the  limited  space  it  occupies  near  the 
angle  between  the  ramus  and  the  body  of  the  jaw.  The  smaller  that  angle  the 
greater  the  difficulty  in  cutting  this  tooth,  which  may  be  compelled  to  carry  before 
it  a  portion  of  the  gum  closely  applied  to  the  base  of  the  coronoid  process,  causing 
inflammation  or  ulceration,  or,  through  irritation  of  the  sensory  branches  of  the  fifth 
nerve,  may  even  produce  trismus,  since  the  motor  supply  of  the  muscles  of  mastica- 
tion is  derived  from  the  same  nerve-trunk.  It  is  thus  much  oftener  the  source  of 
trouble  in  the  white  races  than  in  negroes,  in  whom  the  angle  between  the  ascending 
and  horizontal  portions  of  the  bone  is  more  obtuse. 

Congenital  deformities  of  the  lower  jaw  are  very  rare..  When  they  do  occur, 
as  in  a  case  reported  by  Humphry,  they  show  that  the  jaw  consists  essentially  of  two 
portions,  the  alveolus  and  the  remainder  of  the  jaw.  In  that  case  the  jaw  in  adult 
life  preserved  the  proportions  of  infancy  so  far  as  the  body  was  concerned,  but  the 
teeth  and  alveolus  had  attained  normal  dimensions.  The  division,  as  Allen  has 
emphasized,  is  an  important  one  to  remember  for  the  following  reasons  :  the  alveolus 
is  developed  with  the  teeth  ;  it  is  an  outgrowth  from  the  jaw  for  a  specific  temporary 
purpose.  John  Hunter  declared  that  the  "alveolar  processes  of  both  jaws  should 
rather  be  considered  as  belonging  to  the  teeth  than  as  parts  of  the  jaws."  Hence 
all  diseases  of  the  alveolus  are  to  be  considered  as  dental  in  their  significance. 
Epulis,  or  fibroma  of  the  gums,  is  essentially  an  alveolar  disease.  A  tooth  in  any 
portion  of  the  jaw  other  than  the  alveolus  is  a  foreign  body.  If  it  is  lodged  beneath 
the  alveolus,  it  may  give  rise  to  chronic  abscess,  or  may,  through  long-continued 
irritation,  cause  one  of  the  various  forms  of  odontomata.  Cystic  disease  about  the 
angle  of  the  jaw  is  often  excited  by  a  misplaced  third  molar. 


PRACTICAL    CONSIDERATIONS  :    THE    FACE.  245 

The  inferior  maxilla  has  no  epiphysis,  and,  as  might  therefore  be  expected,  the 
ends  of  the  bone  at  and  near  the  articular  surfaces  are  usually  exempt  from  disease, 
in  marked  contrast  to  the  long  bones,  in  which  those  regions  especially  suffer. 

The  inferior  maxilla  is  not  a  very  vascular  bone  ;  the  mucous  membrane  of  the 
gum  is  in  close  contact  with  it  ;  it  occupies  a  peculiarly  exposed  position,  and  is 
subject  to  frequent  minor  traumatisms  ;  it  is  readily  infected  through  carious  teeth 
or  tooth-sockets.  Such  a  tooth  or  an  open  socket  communicates  directly  with  the 
cancellous  tissue  of  the  bone,  thus  probably  permitting  in  the  lower,  as  in  the  upper 
jaw  the  direct  contact  of  the  toxic  agent  in  phosphorus  necrosis.  Similar  conditions 
are  found  in  no  other  bones  of  the  skeleton. 

As  a  result  of  the  conditions  just  enumerated,  osteitis  and  necrosis  are  common, 
are  associated  with  much  pain,  and  are  often  very  slow  in  their  progress. 

The  excessive  pain,  dysphagia,  dribbling  of  saliva,  and  occasional  aphasia  and 
marked  nervous  symptoms  are  thought  to  be  due  to  reflex  irritation  associated 
with  compression  of  the  inferior  dental  nerve  in  the  dental  canal  by  the  products 
of  inflammation.  Such  irritation  of  a  cranial  nerve  confined  within  a  bony  canal  is 
rare,  and  associates  the  above  symptoms  with  those  occasioned  by  pressure  from 
similar  causes  on  the  other  branches  of  the  fifth  pair  and  on  the  seventh. 

Fracture  of  the  lower  jaw  may  occur  at  any  point.  The  whole  bone  is  to  a  great 
extent  protected  from  fracture  by  its  horse- 
shoe shape,  which  gives  it  some  of  the  ^IG' 
properties  of  a  spring,  by  its  density  of  struc- 
ture, by  its  great  mobility,  and  by  the  buffer- 
like interarticular  cartilages  that  protect  its 
attached  extremities  (Treves). 

The  neck  of  the  condyloid  process  and 
the  coronoid  process  are  so  deeply  situated 
and  so  sheltered  in  the  temporal  fossa  by 
the  zygomatic  arches  that  they  are  seldom 
broken. 

The    ramus    is    protected    (though    to    a  Mandible,  showing  lines of  fractun 

less  extent)  by  the  masseter  externally  and 

the  internal  pterygoid  internally,  and  is  not  often  fractured.      The  angle  and  the 

symphysis  are  thickened,  and  thus  resist  fracture. 

About  three  centimetres  (approximately  one  and  a  quarter  inches)  laterally  to 
the  symphysis  the  bone  is  weakened  by  the  presence  of  the  mental  foramen  and  the 
large  socket  for  the  canine  tooth.  It  is  most  often  broken  there  or  thereabouts 
either  by  direct  or  by  indirect  violence.  Most  fractures  of  the  body  of  the  bone 
are  compound  on  account  of  the  firm  adhesion  of  the  gum,  which  is  usually  torn  ; 
hence  necrosis  and  non-union  following  infection  from  the  mouth-fluids  are  not  un- 
common results.  (For  the  displacement  accompanying  this  fracture  see  section 
on  Muscles,  page  493. )  The  deformity,  in  so  far  as  it  is  produced  by  anatomical 
forces,  is  apt  to  consist  of  depression  of  the  anterior  and  larger  fragment  by  the 
digastric,  the  genio-hyo-glossus,  and  the  genio-hyoid,  and  elevation  of  the  posterior 
and  smaller  fragment  by  the  temporal,  the  masseter,  and  the  internal  pterygoid. 

The  dental  nerve,  while  escaping  injury  at  the  time  of  the  accident,  may  later 
be  compressed  by  callus,  and,  if  irritated,  may,  by  reason  of  its  anatomical  associa- 
tions with  the  regions  in  front  of  the  pinna  or  in  the  external  auditory  meatus,  give 
rise  to  "  faceache"  or  to  "earache."  If  paralyzed,  and  the  patient  puts  a  cup  to 
his  lips,  he  feels  with  his  lower  lip  only  half  of  it  ;  in  paralysis  of  the  fifth  nerve  itself 
it  seems  to  him  exactly  as  though  it  were  broken  (Owen). 

The  capsule  of  the  temporo-maxillary  joint  is  thinnest  anteriorly  and  strongest 
externally  ;  hence  suppuration  is  most  likely  to  extend  in  a  forward  direction. 
The  strong  external  lateral  ligament  arising  from  the  lower  edge  of  the  zygoma  and 
running  backward  and  downward  seems  to  prevent  the  condyle  being  pressed  back- 
ward against  the  bony  meatus  and  the  middle  ear  (Fig.  247).  As  Treves  observes, 
if  it  were  not  for  this  provision,  blows  upon  the  chin  would  be  far  more  dangerous 
than  they  are. 

In  spite  of  its  great  mobility  and  its  frequent  use,  the  joint  is  rarely  the  subject 


246  HUMAN    ANATOMY. 

of  acute  disease,  the  intra-articular  cartilage  being  so  arranged  (page  214)  that  it 
acts  as  an  elastic  buffer  presenting  one  surface  upon  which  the  hinge-like,  and 
another  upon  which  the  sliding,  movement  of  the  jaw  may  take  place.  Suppurative 
disease  of  the  middle  ear  may  extend  to  the  joint  (Barker). 

Rheumatoid  arthritis  is  perhaps  the  most  common  disease  of  the  joint,  and  may 
be  localized  there  in  subjects  otherwise  predisposed  by  the  frequent  exposure  of  the 
joint  to  cold  and  wet. 

The  so-called  "subluxation,"  sometimes,  perhaps,  depending  upon  relaxation 
of  the  ligaments,  is  more  probably  in  the  majority  of  cases  due  to  rheumatic  or  gouty 
changes  in  the  joint. 

Dislocation  of  the  jaw  (discussed  in  connection  with  the  action  of  the  associ- 
ated muscles,  page  493)  occurs  only  when  the  mouth  is  widely  open,  as  in  yawning, 
so  that  the  condyle  passes  beyond  its  proper  limits,  over  the  summit  of  the  ridge, 
and  is  lodged  in  front.  ' '  When  the  mouth  is  widely  opened  the  condyles,  together 
with  the  interarticular  fibro-cartilage,  glide  forward.  The  fibro-cartilage  extends 
as  far  as  the  anterior  edge  of  the  eminentia  articularis,  which  is  coated  with  cartilage 
to  receive  it.  The  condyle  never  reaches  quite  so  far  as  the  summit  of  that  emi- 
nence. All  parts  of  the  capsule  save  the  anterior  are  rendered  tense.  The  coronoid 
process  is  much  depressed.  Now,  if  the  external  pterygoid  muscle  (the  muscle 
mainly  answerable  for  the  luxation)  contract  vigorously,  the  condyle  is  soon  drawn 
over  the  eminence  into  the  zygomatic  fossa,  the  interarticular  cartilage  remaining 
behind.  On  reaching  its  new  position  it  is  immediately  drawn  up  by  the  temporal, 
internal  pterygoid,  and  masseter  muscles,  and  is  thereby  more  or  less  fixed.  A 
specimen  in  the  Mus€e  Dupuytren  shows  that  the  fixity  of  the  luxated  jaw  may 
sometimes  depend  upon  the  catching  of  the  apex  of  the  coronoid  process  against 
the  malar  bone' '  (Treves). 

Excision  of  the  inferior  maxilla,  since  it  is  concerned  chiefly  with  the  soft  parts, 
will  be  considered  in  connection  with  the  Muscles  (page  493). 

Landmarks. — The  supra-orbital  ridges  mark  the  boundary  between  the  face 
and  the  cranium.  The  supra-orbital  notch  can  be  felt  at  the  junction  of  the  inner 
and  middle  thirds  of  the  supra-orbital  margin.  A  line  from  that  point  to  the 
interval  between  the  two  bicuspid  teeth  in  both  jaws  crosses  the  infra-orbital  and 
the  mental  foramina  (Holden). 

The  attachment  of  the  nasal  cartilages  to  the  superior  maxilla;  and  to  the  nasal 
bones  can  easily  be  felt.  The  connective  tissue  between  the  skin  and  the  cartilages 
is  very  scanty.  This  is  a  source  of  difficulty  in  some  of  the  plastic  operations  on  the 
nose,  and  is  also  a  cause  of  the  severe  pain  felt  in  cellulitis  and  in  furuncles  of  that 
region.  The  great  vascularity  of  the  part  and  the  fact  that  ' '  the  edge  of  the  nostril 
is  a  free  border  and  the  circulation  therefore  is  terminal"  (Treves)  favor  congestion 
and  engorgement,  while  the  close  connection  of  the  "skin  and  cartilage  resists  the 
swelling  ;  hence  the  nerve-pressure  and  the  excessive  pain. 

The  malar  prominence,  the  concavity  of  the  superior  maxilla  representing  the 
anterior  wall  of  the  antrum,  its  malar  process,  corresponding  to  the  apex  of  that 
cavity,  the  incisor  fossa,  and  the  canine  fossa  can  easily  be  recognized  either  through 
the  cheek  or,  more  readily,  through  the  gums  with  a  finger  in  the  mouth. 

The  zygoma  can  be  both  seen  and  felt,  the  lower  border  more  distinctly  than 
the  upper  on  account  of  the  attachment  to  the  latter  of  the  dense  temporal  fascia. 
Wasting  diseases  cause  an  apparent  increase  in  the  prominence  of  the  zygoma. 

The  condyle  of  the  inferior  maxilla  can  be  outlined  and  its  motions  observed 
(Fig.  246)  just  in  advance  of  the  ear. 

A  line  drawn  from  the  angle  to  the  condyle  indicates  the  posterior  border  of 
the  ramus.  In  making  incisions  in  this  region  for  inflammatory  or  suppurative 
conditions  this  line  is  to  be  remembered.  Posterior  to  it  important  blood-vessels 
may  be  injured  ;  anterior  to  it  deep  punctures  may  be  made  with  safety,  the  only 
structure  of  consequence  endangered  being  branches  of  the  facial  nerve. 

From  the  angle  of  the  jaw  forward  the  outline  of  the  inferior  maxilla  can  be 
seen  and  felt  both  externally  and  within  the  mouth.  The  alignment  of  the  teeth  is 
usually  disturbed  in  fracture,  and  is  often  the  most  easily  recognized  symptom. 
With  a  finger  between  the  cheek  and  the  teeth,  the  anterior  border  of  the  coronoid 


PRACTICAL    CONSIDERATIONS  :    THE    FACE. 


247 


process  may  readily  be  defined.  In  dislocation  this  is  unnaturally  prominent.  Be- 
tween its  base  and  the  last  molar  tooth  there  is  often  a  space  through  which  liquid  food 
or  other  fluids  can  be  conveyed  by  a  tube  to  the  pharynx  in  cases  in  which  fracture- 
dressing,  or  trismus,  or  ankylosis  renders  the  lower  jaw  immovable.  Along  the  lower 
border  externally,  just  in  advance  of  the  anterior  edge  of  the  masseter,  the  groove 
for  the  facial  artery  may  be  felt,  and  in  the  middle  line  the  ridge  which  indicates  the 
thickening  at  the  symphysis. 

On  the  inner  surface  of  the  jaw  may  be  recognized  the  genial  tubercles,  some- 
times in  two  distinct  pairs,  indicating 
the  attachments  of  the  genio-hyo- 
glossi  and  genio-hyoidei.  The  sub- 
lingual fossa?  may  be  located,  and  just 
external  to  them,  and  at  their  lower 
border,  the  faint  beginning  of  the 
mylo-hyoid  ridge,  which  runs  upward 
and  backward,  becoming  more  evident 
opposite  the  last  two  molars. 

Above  this  line  the  bone  is  cov- 
ered by  the  mucous  membrane  of  the 
mouth  ;  hence  diseases  of  this  portion 
find  their  expression  in  the  oral  cavity, 
while  those  of  the  lower  portion  of  the 
bone  are  more  apt  to  involve  the  soft  parts  and  glands  of  the  neck  (Fig.  267). 
The  fossae  for  the  submaxillary  glands  cannot  be  felt  through  the  mouth,  but,  as  they 
lie  below  the  ridge,  while  the  sublingual  fossae  lie  above  it,  the  well-known  clinical 
relations  of  the  former  glands  to  the  neck  and  of  the  latter  to  the  mouth  are  explained. 

The  familiar  change  in  the  shape  of  the  lower  jaw  in  edentulous  old  persons  is 
due  to  absorption  of  the  alveolar  process. 

(Most  of  the  landmarks  of  the  face  are  of  more  importance  in  relation  to  the 
soft  parts,  the  nerves,  and  the  contents  of  the  cavities  of  the  orbit,  nose,  and  mouth 
than  in  connection  with  the  bones  themselves.  They  will,  therefore,  be  further  con- 
sidered in  those  connections.) 


Inner  surface  of  lower  jaw,  showing  various 


THE  UPPER   EXTREMITY. 

The  Shoulder-Girdle. — This  consists  of  the  clavicle  and  scapula.  The  latter 
is  far  the  most  important  morphologically,  representing,  as  it  does,  both  the  scapula 
and  the  coracoid  of  the  lower  classes  of  vertebrates  ;  while  the  clavicle  is  inconstant 
in  mammals,  and  seems  to  be  no  part  of  the  primitive  shoulder-girdle.  The  scapula 
bears  the  socket  for  the  humerus.  It  has  no  bony  attachment  to  the  trunk  save 
through  the  clavicle,  which,  interposed  between  it  and  the  sternum,  is  connected 
with  both  by  joints. 

THE   SCAPULA. 

Physiologically,  the  essentia]  part  of  the  scapula  is  the  socket  for  the  shoulder  ; 
a  part  of  this  is  made  by  the  coracoid  element,  which  in  man  is  an  insignificant  pro- 
cess of  the  shoulder-blade.  The  secondary  functions  of  the  bone  are  to  give  origin 
to  some  muscles  and  to  afford  leverage  to  others  for  their  action  on  the  arm.  In 
most  mammals  the  scapula  may  be  considered  a  rod  running  upward  from  the  joint, 
from  which  three  plates  expand,  one  towards  the  head,  one  towards  the  tail,  and  one 
outward.  In  man  the  second  of  these  plates  points  downward  and  is  excessively 
developed.  It  is  more  convenient  in  man  to  speak  of  one  main  plate,  the  body  of  the 
scapula,  with  the  spine  springing  from  the  dorsal  surface. 

The  body  is  triangular,  with  two  surfaces, — a  ventral  one  towards  the  ribs  and 
a  free  dorsal  one, — three  borders,  and  three  angles. 

The  posterior  or  vertebral  border,1  sometimes  called  the  base,  is  the  longest. 
It  is  nearly  vertical  from  the  lower  angle  to  a  triangular  space  on  the  dorsum,  oppo- 
site the  origin  of  the  spine,  above  this  it,  as  a  rule,  slants  forward,  but  at  a  very 
varying  angle.  The  upper  border  2  slants  downward  and  forward  to  the  supra- 
scapular notch3  at  the  base  of  the  coracoid  process.  This  notch,  transmitting  the 
suprascapular  nerve,  is  sometimes  imperceptible,  but  usually  is  well  marked  and 
sometimes  very  deep.  It  is  bridged  by  a  ligament,  which  may  be  replaced  by  bone, 
transforming  the  notch  into  a  foramen.  The  anterior  or  axillary  border4  is  the 
only  thick  one.  Just  below  the  glenoid  cavity  it  begins  as  a  triangular  roughness 
for  the  long  head  of  the  triceps.  This  is  continued  as  a  line  which  ends  on  the 
dorsal  surface  near  the  lower  angle,  a  littie  above  an  unnamed  process  curving  for- 
ward and  inward  from  which  a  part  of  the  teres  major  arises.  This  is  the  analogue 
of  a  process  much  developed  in  some  small  monkeys.  It  is  sometimes  very  large, 
the  increase  of  size  being  in  no  relation  to  that  of  the  bone  nor  of  the  muscle. 
Above  this  on  the  anterior  border  there  is  a  deep  groove  for  a  part  of  the  sub- 
scapularis  muscle  just  internal  to  the  anterior  edge  proper.  Below  the  process  the 
border  runs  downward  and  backward  to  the  inferior  angle.3  This  angle  is  some- 
times very  sharp,  sometimes  quite  the  reverse.  The  same,  in  a  less  degree,  may 
be  said  of  the  upper  angle,6  usually  sharp,  sometimes  squarely  truncated.  The 
anterior  angle  ~  is  the  glenoid  cavity.  This,  with  the  base  of  the  coracoid  process, 
is  called  the  head  of  the  scapula,  the  neck  being  a  constricted  region  behind  it, 
reaching  to  the  suprascapular  notch.  The  glenoid  cavity8  is  an  oval,  slightly 
hollowed,  cartilage-covered  surface  expanding  from  a  narrower  base.  The  long  axis 
is  vertical  and  the  broad  end  below.  There  is  often  an  indentation  at  the  upper 
part  of  the  inner  margin.  The  edge  is  a  little  raised  where  it  bears  the  gle?ioid 
ligament,  which  deepens  the  cavity  for  the  reception  of  the  head  of  the  humerus. 
The  top  of  the  edge  forms  the  supf;aglenoid  tubercle,  whence  starts  the  long  head  of 
the  biceps. 

The  coracoid  process  springs  from  the  top  of  the  head  just  behind  the  glenoid 
cavity  and  a  little  to  the  inner  side.  The  first  part,  or  root,  which  is  compressed 
from  side  to  side,  rises  inclining  somewhat  inward.  The  second,  the  free  projecting 
portion,  irregularly  cylindrical,  runs  forward,  rather  outward  and  downward,  to  end 
in  a  knob  near  the  inner  side  of  the  shoulder-joint.      The  upper  and  inner  surface  is 

1  Margo  vertebralis.    -  M.  superior.    3  Incisura  scapulae.    4  M.  axillaris.    5  Angulu9  inferior.    GA.  medialis.     7  A.  lateralis. 


THE  SCAPULA. 


249 


rough  and  convex,  the  under  and  outer  smooth  and  concave.  A  rounded  promi- 
nence, the  conoid  tubercle,  for  the  conoid  ligament,  is  situated  on  the  top  of  the  first 
part  and  rather  to  the  inner  side,  just  above  the  angle  formed  by  the  two  parts.  A 
ridge  from  behind  this,  running  outward  and  forward,  separates  the  two  parts  dis- 
tinctly. The  trapezoid  ridge  for  the  trapezoid  ligament  runs  forward  from  the  conoid 
tubercle  along  the  inner  side.      The  outer  side  of  the  upper  aspect  has  a  ridge  for 


Fig.  268. 

acromion  process 


CORACOID  PROCESS 


Root  of  spin 


Long  head  of  tricep. 


POSTERIOR  SURFACE      1 


INFERIOR  ANGLE 

Right  scapula  from  before. 

the  coraco-acromial  ligament.  The  short  head  of  the  biceps  and  the  coraco- 
brachialis  arise  from  a  roughness  at  the  tip  of  the  process,  and  the  pectoralis  minor 
from  one  at  its  inner  side. 

The  anterior  surface,  or  venter,1  is  concave,  forming  the  subscapular  fossa, 
the  deepest  hollow  being  along  the  origin  of  the  spine.  At  the  very  top  the  bone 
often  takes  a  turn  outward.  The  serratus  magnus  is  attached  to  rough  surfaces 
inside  the  upper  and  lower  angles  and  to  a  narrow  line  connecting  them  just  beside 

1  Facies  costalis. 


250 


HUMAN    ANATOMY. 


the  vertebral  border.  These  surfaces  are  separated  from  the  rest  of  the  fossa  by 
well-marked  lines,  which,  with  some  four  ridges  running  forward  and  upward  from  the 
spinal  border,  give  origin  to  tendinous  septa  from  which  the  subscapularis  springs. 
This  muscle  arises  also  from  the  deep  groove  inside  the  axillary  border. 

The  posterior  surface,1  or  dorsum,  is  divided  by  the  spine  into  a  supraspinous 
and  an  infraspinous  fossa.  The  former  gives  origin  to  the  supraspinatus.  Near  the 
back  it  is  often  strengthened  by  a  vertical  swelling.  The  infraspinous  fossa  is  chiefly 
occupied  by  the  infraspinatus,  but  two  other  areas  are  marked  off  by  two  lines  :  one, 
running  forward  and  upward,  separates  the  dorsal  side  of  the  lower  angle  and  of  the 
unnamed  process  on  the  axillary  border  ;  from  this  space  springs  the  teres  major. 
The  second  line  leaves  the  axillary  border  near  the  glenoid  cavity  and,  diverging 
slightly,  strikes  the  former  line  near  the  front,  bounding  a  narrow  region  for  the 
teres  minor,  which  is  crossed  high  up  by  a  groove  for  the  dorsal  scapular  artery. 

Fig.  269. 

Anterior  tubercle        acromion 
Coraco-acromial  ligament 


Short  head  of  biceps 

)  PROCESS 


Long  head  of  bleep 


Suprascapular  notch 


Metacromial  tubercle 


Upper  part  of  vertebral  border 


The  spine  2  is  a  triangular  plate  arising  from  a  small  triangular  surface  at  the  pos- 
terior border,  running  outward  and  somewhat  upward.  Its  attached  border  stops  at 
the  neck  before  reaching  the  glenoid  cavity.  The  spine  forms  an  acute  angle  with 
the  floor  of  the  supraspinous  fossa,  and  an  obtuse  one  with  that  of  the  infraspinous. 
Its  front  border  is  rounded  and  curves  forward,  and  forms  the  posterior  boundary 
of  the  great  scapular  notch  connecting  the  supra-  and  infraspinous  fossae.  The  free 
border  is  narrow  beyond  the  triangular  area,  but  soon  broadens,  presenting  an  upper 
and  a  lower  lip.  The  descending  fibres  of  the  trapezius  are  inserted  into  the  whole 
length  of  the  former,  and  of  its  continuation  into  the  acromion.  The  lower  lip  often 
begins  with  a  tubercle  for  the  ascending  and  horizontal  fibres,  a  little  beyond  which 
it  narrows  again.  It  gives  origin  to  the  deltoid  muscle,  which  also  is  continued 
along  the  acromion. 

The  acromion3  is  a  broad,  flat  expansion  overhanging  the  shoulder-joint  and 
articulating  with  the  clavicle  by  an  elongated  facet  slanting  slightly  upward.      A 

1  Facies  dorsalis.     -  Spina  scapulae. 


THE    SCAPULA. 


251 


short  preclavicular  border  in  front  of  this,  receiving  the  outer  end  of  the  coraco- 
acromial  ligament,  runs  forward  and  outward  to  the  anterior  tubercle.  From  this 
the  outer  border  runs  backward  to  the  mctacromial  tubercle,  whence  the  posterior 
border  runs  into  the  hind  edge  of  the  spine.  The  outer  border  has  three  or  four 
irregularities  above  for  the  tendinous  septa  of  the  deltoid,  and  is  smooth  at  its  lower 
edge  for  the  same  muscle.  The  lower  lip  of  the  spine  runs  directly  into  the  hind 
border  of  the  acromion,  but  often  splits  so  as  to  enclose  a  narrow  space  continued  into 
the  back  of  the  process,  from  which  the  deltoid  springs.  The  acromion  varies  much 
in  shape  ;   according  to  this  description  it  is  quadrate  ;    often,   however,   the  pre- 

FlG.    27CTV 


Levator  anguli  scapula:' 
Supraspinatu 
Trapezi 

A 


Coraco-acromial  ligament 

process     Biceps  and  coraco- 
brachialis 


al  origin  of  latissii 
Right  scapula  from  behind. 


clavicular  edge  is  rudimentary,  so  that  it  is  three-sided  ;  or  the  metacromial  tubercle 
is  at  the  apex  of  a  very  obtuse  angle,  so  that  it  is  curved  and  narrow.  There  are 
also  intermediate  forms.1  The  inclination  of  the  acromion  to  the  horizon  is  on  an 
average  not  far  from  450,  with  a  variation  of  probably  150  either  way.  This  may  or 
may  not  depend  on  a  corresponding  variation  of  slant  in  the  spine. 


All  the  details  determining  the  outline  of  the  scapula  vary  greatly.  The  hind  border  may 
be  convex,  or  the  infraspinous  portion  concave.  The  bone  lying  with  the  dorsum  up  should 
rest  on  the  coracoid  and  the  upper  and  lower  angles,  with  the  vertebral  edge  rising  from  the 
table  ;  but  this  may  be  almost  straight,  or  even  bend  the  other  way  so  as  to  change  the  usual 
points  of  support.   'The  length  from  the  upper  to  the  lower  angle  ranges  from  13.2  centimetres 

1  Macalister :  Journal  of  Anatomy  and  Physiology,  vol.  xxvii.,  1S93. 


252 


HUMAN    ANATOMY. 


or  less  up  to  20.1  centimetres.  The  scapular  index  is  the  ratio  of  the  breadth,  measured  along 
the  base  of  the  spine,  to  the  length  ( '°°  '^en  ^ — )•  It  ranges  from  55  to  82.  The  following 
means  have  been  given  for  Caucasians  :  Broca,  65.9  ;  Flower  and  Garson,  65.2  ;  Dwight,  63.5. 
A  high  index  means  a  broad  scapula,  which  is  one  of  a  low  type.  The  infraspinous  index  is 
the  ratio  of  the  breadth  to  the  length  of  the  infraspinous  fossa,  measured  from  the  lower  angle 
to  the  starting-point  of  the  spine  (.  "'"  .  "''",  '  ,  )•  This  ranges  from  72.3  to  100.2,  with  a 
mean  of  about  87.  Although  high  indices  imply  a  broad  scapula,  this  method  is  of  small  value, 
as  very  diverse  shapes  may  have  similar  indices.  It  is  not  possible  to  predicate  anything  of  the 
figure  during  life  from  the  shape  of  this  bone.  The  most  that  can  be  said  is  that  a  long  arm 
requires  the  leverage  furnished  by  a  long  scapula. 

Differences  due  to  Sex. — The  chief  point  is  the  size.  From  the  study  of 
eighty-four  male  and  thirty-nine  female  bones  it  appears  that  of  123  bones,  twenty- 
six  measure  less  than  fifteen  centimetres  in  length,  of  which  only  three  were  male  ; 
also  that  seventy-six  measure  sixteen  centimetres  or  more,  of  which  only  five  were 


Serratus  magnus 


Rid.^t's  lor  tendi- 
attach- 
ments 


Process  for  teres  major 


Serratus  magnus 


Right  scapula  from  before. 


female.  There  was  no  single  instance  of  a  bone  measuring  less  than  fourteen  centi- 
metres being  male,  nor  of  one  measuring  seventeen  centimetres  being  female.  In 
doubtful  cases  the  glenoid  cavity  is  very  valuable.  In  woman  it  is  not  only  smaller, 
but  relatively  narrower.  Very  few  male  sockets  are  less  than  3.6  centimetres  in 
length,  and  very  few  female  as  long.      The  typical  female  scapula  is  very  delicate  ; 


PRACTICAL    CONSIDERATIONS  :    THE    SCAPULA. 


253 


the  lower  angle  is  sharp,  the  process  on  the  front  border  small  ;  the  hind  border 
straight  up  to  the  spine,  then  slanting  forward  in  another  straight  line  ;  the  upper 
border  descends  sharply  ;  the  coracoid  is  slight,  with  the  end  compressed  instead  of 
knobbed  ;  the  acromion  is  curved  and  narrow.  An  expert  should  be  reasonably 
sure  of  the  sex  four  times  in  five.  Doubtful  bones  are  almost  always  male  ;  so  are 
those  of  peculiar  shape,  with  the  exception  of  concave  vertebral  borders.  The 
scapular  index  has  no  sexual  significance.1 

Structure. — The  strong  parts  are  seen  when  the  bone  is  held  to  the  light. 
The  head,  neck,  coracoid,  acromion,  and  most  of  the  spine  are  strong.  So  also 
are  the  front  border,  the  lower  angle,  and,  to  a  less  extent,  the  hind  border,  which 
is  strongest  above  the  spine.  Most  of  the  body  is  very  thin.  A  section  through 
the  socket,  along  the  origin  of  the  spine,  shows  the  bony  plates  so  disposed  as  to 
resist  pressure  in  that  line. 

Development. — There  is  one  chief  centre  for  the  scapula  proper  and  one  for 
the  coracoid,  besides  an  indefinite  number  of  accessory  ones.  The  first  appears 
about  the  eighth  week  (Rambaud  et  Renault)  at  the  neck,  and  forms  nearly  the 

Fig.   272. 


Ossification  of  scapula.  A ,  at  eighth  fcetal  month  ;  B,  towards  end  of  first  year ;  C,  from  fourteen  to  fifteen  years  ; 
Z>,  from  seventeen  to  eighteen  years  ;  E,  about  twenty  years,  a,  chief  centre ;  b,  for  coracoid  process ;  c,  for  acro- 
mion ;  d,  for  inferior  angle  ;  e,  additional  for  acromion  ;  /,  for  vertebral  border. 

whole  bone,  including  the  spine  and  the  root  of  the  acromion  and  the  dorsal  part  of 
the  root  of  the  coracoid.  The  coracoid  centre  appears  in  the  first  year  ;  it  forms 
also  the  top  of  the  glenoid  cavity,  and  fuses  with  the  first  at  fourteen  or  fifteen, 
beginning  to  unite  at  the  ventral  surface.  At  the  earlier  age  the  acromion  is  carti- 
lage beyond  a  line  drawn  from  the  back  of  the  clavicular  facet  to  the  front  of  the 
metacromion.  At  about  fifteen  many  little  nuclei  appear  in  the  acromion.  The 
anterior  tubercle  is  formed  from  a  single  nucleus  ;  the  others  coalesce  into  two 
groups, — one  in  the  centre,  the  other  at  the  outer  margin.  At  about  eighteen  the 
latter  joins  the  body  and  the  other  two  fuse.  A  year  later  the  mass  so  formed  also 
joins  the  body.  Sometimes  this  remains  connected  by  fibro-cartilage  ;  very  rarely 
several  pieces  persist.  A  scale-like  epiphysis  appears  at  the  conoid  tubercle  of  the 
coracoid  about  fifteen,  and  soon  fuses.  About  seventeen  or  eighteen  a  nucleus 
appears  in  the  strip  of  cartilage  along  the  posterior  border  and  one  at  the  lower 
angle.  Both  are  generally  fused  by  twenty,  but  the  lower  is  one  of  the  last  to  fuse 
in  the  skeleton,  and  the  line  of  union  may  remain  for  years. 


PRACTICAL    CONSIDERATIONS. 

The  scapula  is  rarely  absent  and  rarely  malformed.  The  outer  part  of  the 
acromion  may  exist  as  a  distinct  bone,  as  may,  but  less  frequently,  the  coracoid. 
Many  cases  of  so-called  fracture  of  the  acromion  and  others  of  supposed  traumatic 
separation  of  the  acromial  epiphysis  are  probably  cases  of  persistent  epiphysis.  The 
centre  for  the  inferior  angle  sometimes  remains  distinct,  being  united  to  the  body 

1  Dwight :  The  Range  and  Significance  of  Variation  in  the  Human  Skeleton,  Proc.  Mass. 
Med.  Soc,  1804. 


254  HUMAN    ANATOMY. 

by  a  synchondrosis.  The  possibility  of  its  detachment  by  excessive  action  of  the 
latissimus  dorsi  has  been  mentioned,  but  no  case  of  traumatic  separation  has  been 
recorded. 

Fracture  is  rare,  in  spite  of  the  thinness  of  much  of  the  bone,  because  of  its 
mobility,  the  adaptation  of  its  curves  to  the  underlying  thoracic  surface,  the  elasticity 
and  compressibility  of  that  surface,    the  thickness  of  the  muscles  that  cover  the 
scapula  and  of  those  that  lie  beneath  it,  the  fragility  of  the  clavicle  (which  by  frac- 
turing often  saves  the  scapula),  and  the  great  range  of 
Fig.  273.  movement  and  corresponding  weakness  of  the  shoulder- 

joint,  which,  in  like  manner,  by  undergoing  luxation, 
prevents  the  force  of  the  traumatism  from  reaching  the 
scapula. 

Fracture  of  the  body  and  of  the  inferior  angle  from 
indirect  violence  has  been  reported  in  a  few  cases.  The 
arms  were  fixed,  and  strong  traction  was  being  exer- 
cised in  more  than  one  case.  It  seems  probable  that 
the  bone  breaks  between  the  opposing  forces  of  the 
rhomboids  and  trapezius  on  the  one  hand,  and  the 
teres  muscles,  the  subscapularis,  and  the  infraspinatus 
on  the  other. 

The  most  common  fracture  is  that  of  the  body, 
usually  running  transversely  or  obliquely  through  the 
subspinous  fossa.  The  attachments  of  the  subscapu- 
laris beneath  and  of  the  infraspinatus  above  usually 
prevent  any  marked  displacement.  There  is  pain  on 
;  of  fracture  of  the  scapula.  lifting  the  arm  to  a  horizontal  position,  because,  in  order 
that  the  deltoid  may  be  able  to  do  this,  the  acromion 
must  become  a  fixed  point,  and  that  necessitates  the  contraction  of  the  rhomboids 
and  other  muscles  whose  function  it  is,  aided  by  the  leverage  afforded  by  the  pro- 
longation of  the  scapula  downward,  to  fix  the  blade  of  the  scapula  when  the  deltoid 
is  in  action. 

Superficial  ecchymosis  is  rare  on  account  of  the  dense  infraspinous  fascia  which 
prevents  the  effused  blood  from  reaching  the  surface. 

Fracture  of  the  acromion  is  attended  with  slight  flattening  of  the  tip  of  the 
shoulder,  the  weight  of  the  arm,  acting  through  the  deltoid,  dragging  the  frag- 
ment downward.  There  may  be  the  usual  symptoms  of  preternatural  mobility, 
crepitus,  etc. 

Fracture  of  the  coracoid  is  rare.  Before  the  age  of  seventeen  it  may  be  an 
epiphyseal  separation.  Displacement  is  not  common,  as  the  downward  pull  of  the 
pectoralis  minor,  short  head  of  the  biceps,  and  coraco-brachialis  (page  590)  is 
effectually  resisted  by  the  coraco-acromial  and  coraco-clavicular  ligaments.  Crepitus 
and  preternatural  mobility  may  possibly  be  recognized  by  sinking  the  fingers  into 
the  interval  between  the  deltoid  and  pectoral  muscles.  The  coracoid  will  be  found 
just  beneath  the  inner  deltoid  margin. 

Fractures  of  the  neck  of  the  scapula  include,  in  surgical  language,  those  which 
begin  at  the  suprascapular  notch  and  run  to  the  axillary  border  of  the  bone  detach- 
ing the  glenoid  cavity  and  the  coracoid  process.  There  is  no  instance  of  fracture  of 
the  anatomical  neck, — the  constricted  part  supporting  the  glenoid  cavity.  The 
fragment,  with  the  arm,  will  drop  downward,  away  from  the  acromion.  This  puts 
the  deltoid  on  the  stretch  and  causes  flattening  of  the  shoulder.  There  will  be  a 
depression  beneath  the  edge  of  the  acromion.  The  arm  will  be  increased  in  length. 
These  symptoms  (which  will  occur  only  if  the  coraco-acromial  and  coraco-clavicular 
ligaments  are  torn)  are  also  found  in  subglenoid  luxation  of  the  humerus  (page  583)  ; 
but  in  the  fracture,  the  presence  of  crepitus,  the  downward  displacement  of  the 
coracoid,  the  ready  disappearance  of  the  deformity  on  pushing  the  head  of  the 
humerus  upward,  its  prompt  reappearance  when  the  arm  is  allowed  to  hang' by  the 
side,  and  the  ease  with  which  the  hand  may  be  placed  on  the  opposite  shoulder 
serve  clearly  to  denote  the  character  of  the  accident. 

Excision  of  the  scapula  itself  is  not  uncommonly  indicated  on  account  of  malig- 


PRACTICAL   CONSIDERATIONS  :     THE   SCAPULA.  255 

nant  neoplasm,  subperiosteal  and  central  sarcomata  especially.  The  main  danger 
of  the  operation  is  hemorrhage.  The  subclavian  should,  therefore,  be  controlled. 
The  dorsalis  scapula;,  crossing  the  axillary  border  of  the  scapula  at  a  point  on  a  level 
with  the  centre  of  the  vertical  axis  of  the  deltoid  (Treves),  and  the  subscapular  run- 
ning along  the  lower  border  of  the  subscapularis  muscle  to  reach  the  inferior  angle, 
are  the  largest  vessels  that  require  division,  but  the  suprascapular,  posterior 
scapular,  and  branches  of  the  acromio-thoracic  artery  will  also  be  cut. 

Infectious  diseases  giving  rise  to  caries  and  necrosis  and  to  suppuration  are 
rare.  When  they  affect  the  supraspinous  region  the  pus  is  directed  forward  by  the 
fascia  covering  the  supraspinatus,  which  encloses  that  muscle  in  an  osseo-fibrous 
compartment.  In  the  infraspinous  region  the  still  denser  infraspinous  fascia  con- 
ducts the  pus  in  the  same  direction  ;  hence  abscesses  originating  in  scapular  dis- 
ease are  likely  to  point  near  the  axilla  and  in  the  neighborhood  of  the  insertions  of 
the  scapular. muscles  into  the  humerus.  On  the  under  surface  of  the  scapula,  between 
the  ridges  which  give  origin  to  the  tendinous  fibres  that  intersect  the  subscapularis 
muscle,  the  periosteum  is  loose  and  easily  separated.  Suppuration  following  caries 
of  this  aspect  of  the  bone  may,  therefore,  cause  extensive  detachment  of  the  perios- 
teum, and  it  has  been  found  necessary  to  trephine  the  thin  portion  of  the  blade  of 
the  scapula  to  give  vent  to  such  a  purulent  collection. 

Landmarks. — The  greatest  breadth  of  the  scapula  is  in  aline  from  the  glenoid 
margin  to  the  vertebral  border  ;  the  greatest  length  in  a  line  from  the  superior  to 
the  inferior  angle. 

The  general  outlines  of  the  scapula  can  easily  be  felt.  The  bony  points  most 
readily  recognized  by  touch  are  the  acromion,  the  coracoid,  the  spine,  the  vertebral 
edge,  and  the  inferior  angle. 

The  edge  of  the  acromion  is  an  important  landmark.  Measurement  from  it  to 
the  suprasternal  notch  is  the  easiest  way  of  determining  shortening  in  fracture  of  the 
clavicle.  If  this  measurement  is  less  than  on  the  sound  side,  and  the  clavicle  itself 
is  unchanged  in  length,  it  indicates  a  dislocation  of  the  acromial  end  of  the  latter. 

Undue  prominence  of  the  edge  of  the  acromion  is  seen  in  luxation  of  the 
humerus  (page  582)  and  in  fracture  of  the  neck  of  the  scapula.  In  these  conditions 
the  fingers  may  be  pressed  beneath  the  acromion,  as  they  can  in  old  cases  of  deltoid 
paresis  or  paralysis  with  atrophy  of  that  muscle,  when  the  weight  of  the  arm  drags 
the  humerus  downward  and  increases  the  space  between  the  greater  tuberosity  and 
the  acromial  edge. 

The  coracoid  process  may  be  felt  through  the  inner  deltoid  fibres,  below  the 
inner  portion  of  the  outer  third  of  the  clavicle,  by  thrusting  the  fingers  into  the 
space  between  the  pectoral  and  deltoid.  In  fracture  it  may  be  depressed,  as  it  is  in 
fracture  of  the  scapular  neck.  The  axillary  artery  can  be  felt  just  to  the  inner  side 
of  the  coracoid  as  it  passes  over  the  second  rib. 

The  spine  is  least  prominent  in  muscular  and  most  conspicuous  in  feeble  and 
emaciated  persons.  This  is  also  true  of  the  inferior  angle,  which  in  weak,  and 
especially  in  phthisical,  subjects  is  not  held  tightly  to  the  chest,  but  projects  in  a 
wing-like  manner  (scapulae  alatae).  This  is  partly  due  to  general  muscular  weak- 
ness, in  which  the  latissimus  dorsi  and  serratus  magnus  participate,  and  partly  to 
the  shape  of  the  thorax  and  the  direction  of  the  clavicles.  The  flatter  and  shallower 
the  chest  the  more  oblique  in  direction  and  the  lower  are  the  collar-bones,  carrying 
with  them  downward  and  forward  the  upper  and  anterior  portions  of  the  scapulae, 
and  by  that  much  tending  to  make  the  lower  and  posterior  portions  more  promi- 
nent. 

The  length  of  the  arm  is  usually  measured  from  the  junction  of  the  spine  of  the 
scapula  and  the  acromion — the  acromial  angle — to  the  external  condyle  of  the 
humerus. 

The  vertebral  edge  of  the  scapula  lies  just  at  the  side  of  the  spinal  gutter. 
When  the  arm  hangs  at  the  side  of  the  body,  this  edge  is  parallel  with  the  line 
of  the  spinous  processes.  It  can  be  made  prominent  (for  palpation)  by  carrying 
the  hand  of  the  patient  over  the  opposite  shoulder.  The  superior  angle  is  made 
accessible  by  the  same  position.  The  axillary  border  of  the  scapula  and  the  inferior 
angle  are  best  examined  with  the  elbow  flexed  and  the  forearm  carried  behind  the 


256 


HUMAN    ANATOMY. 


back.  With  the  arm  at  the  side,  the  superior  angle  is  about  on  the  level  of  the 
upper  edge  of  the  second  rib  ;  the  inferior  angle  is  opposite  the  seventh  intercostal 
space  (and  hence  is  a  guide  in  selecting  a  space  for  the  various  operations  for  em- 
pyema, page  1867);  the  inner  end  of  the  spine  is  opposite  the  spinous  process  of  the 
third  dorsal  vertebra. 

With  the  shoulders  drawn  forcibly  backward,  the  vertebral  borders  of  the  scapulae 
can  be  made  almost  to  touch  at  the  level  of  the  spines,  and  are  not  more  than  from 
two  to  three  inches  apart  at  the  angles.  With  the  hands  clasped  on  the  vertex,  the 
inferior  angles  are  from  sixteen  to  seventeen  inches  apart.  By  crossing  the  arms  on 
the  front  of  the  chest,  and  leaning  forward,  the  scapulae  are  also  widely  separated, 
and  this  position  is  therefore  selected  for  auscultation  and  percussion. 

The  mobility  of  the  scapula  lessens  the  functional  disability  in  ankylosis  of  the 
shoulder-joint. 

LIGAMENTS   OF  THE   SCAPULA. 

Two  ligaments — the  transverse  and  the  coraco-acromial — pass  from  one  part  of  the 
scapula  to  another. 

The  transverse  or  suprascapular  ligament1  (Fig.  289)  is  a  little  band  on  the 
upper  border,  just  behind  the  root  of  the  coracoid,  making  a  bridge  over  the  supra- 
scapular notch,  under  which  the  suprascapular  nerve  passes.  It  may  be  replaced  by 
bone. 

The  coraco-acromial  ligament2  (Fig.  274)  is  a  triangular  structure,  broad 
at  its  base,  along  the  outer  border  of  the  coracoid  process,  and  narrowing  to  its 
insertion  into  the  inner  side  of  the  end  of  the  acromion  just  in  front  of  the  acromio- 
clavicular joint.  The  borders  are  strong,  converging  bands  with  a  weak  space 
between,   the  front  one  being  the  stronger  and  overlapping  the  other  when  they 


Fig.  274. 

Acromioclavicular  joint 


Capsule  of  shoulder-joint 
Humerus 


Ligaments  about  the  right  shoulder  from  above. 


meet.  The  course  of  the  fibres  in  the  weaker  part  is  variable  ;  sometimes  they 
diverge  from  near  the  front  of  the  coracoid  to  the  posterior  band,  sometimes  they 
are  in  the  main  parallel  with  the  latter,  sometimes  a  band  passes  from  this  membrane 
to  the  front  of  the  clavicle.  The  weak  portion  of  this  ligament  is  pierced  by  the 
pectoralis  minor,  when,  as  often  happens,  this  muscle  is  inserted  into  the  capsule  of 
the  shoulder  or  the  upper  end  of  the  humerus.  This  ligament  is  really  part  of  the 
apparatus  of  the  shoulder-joint,  forming  a  roof  over  the  capsule,  from  which  it  is 
separated  by  a  bursa.     Before  dissection  the  hind  border  of  the  ligament  is  not  very 

1  Lig.  transversura  scapulae  superius.     '-  Lig.  coracoacromiale. 


THE    CLAVICLE. 


257 


distinct,  since  the  bursa  appears  to  connect  it  with  the  capsule  below  and  a  thin 
fascia  with  the  clavicle  above. 

The  spino-glenoid  ligament1  is  an  occasional  little  band  at  the  great  scapular 
notch,  running  from  the  anterior  border  of  the  spine  to  the  posterior  edge  of  the 
glenoid  cavity,  crossing  the  suprascapular  vessels  and  nerve. 

THE   CLAVICLE. 

The  function  of  the  clavicle,2  or  collar-bone,  which  extends  from  the  top  of  the 
sternum  to  the  acromion,  is  to  give  support  to  the  shoulder-joint  in  the  wide  and 
varied  movements  of  the  arm.  It  is  found  in  mammals  that  climb,  fly,  dig,  or  swim 
with  movements  requiring  an  outward  and  backward  sweep  of  the  arm.  It  is 
absent  in  those  that  use  the  fore-limb  simply  for  progression  with  movements  nearly 
restricted  to  one  plane.      It  is  present,  but  imperfectly  developed,  in  some  carnivora 


ACROMIAL   END 


Right  clavicle,  superior  and  posterior  surfaces. 


STERNAL  END 
Pectoralis  major 


whose  arms  serve,  in  part,  for  prehension.      In  man  it  has  a  doubly  curved  shaft,  a 
thick  inner  end,  and  a  flattened  outer  one. 

The  shaft  is  convex  in  front  through  the  two  inner  thirds  and  concave  in  the 
outer  one.  The  former  portion  has  a  superior,  an  inferior,  an  anterior,  and  a  pos- 
terior surface  ;  but  in  the  outer  third  the  two  latter  surfaces  narrow  into  borders. 
The  superior  surface  is  smooth,  except  for  a  slight  unevenness  at  the  inner  end, 


Aiinmial  facet 


Fig.  276. 


Pectoralis  major 


Sterno-hyoid 


Trapezoid  ridge 


Conoid  tubercle 

Right  clavicle,  anterior  and  inferior  surfaces. 


giving  origin  to  the  clavicular  head  of  the  sterno-cleido-mastoid.  The  inferior  sur- 
face has  near  the  inner  end  an  oval  roughness,  which  may  or  may  not  be  raised, 
for  the  rhomboid  ligament  from  the  cartilage  of  the  first  rib.  Beyond  this  is  a  longi- 
tudinal groove,  more  marked  near  the  outer  end,  for  the  insertion  of  the  subclavius 
muscle.  Outside  of  the  middle,  near  the  hind  border  (sometimes  on  the  hind  surface), 
is  the  nutrient  foramen,  directed  outward.  The  anterior  surface  narrows  continu- 
ally from  within  outward.      The  inner  two-thirds  are  rough  for  the  pectoralis  major  ; 

1  Lig.  transversum  scapulae  infcrius.     -  Claviculo. 

17 


258  HUMAN   ANATOMY. 

external  to  this  the  rough  concave  edge  gives  origin  to  the  deltoid.  The  beginning 
of  this  is  often  marked  by  a  minute  tubercle,  which,  when  exceptionally  large,  is 
the  deltoid  tubercle.  The  posterior  surface  is  smooth,  and  narrows  gradually  till 
it  reaches  the  outer  end,  the  beginning  of  which  is  marked  by  a  tubercle  on  the 
under  surface. 

The  borders  are  very  ill  marked.  The  sharpest  is  that  separating  the  anterior 
from  the  inferior  surface.  That  between  the  anterior  and  superior  ones  is  fairly  well 
marked  near  the  inner  end  ;  but  it  soon  grows  indistinct,  so  that  often  at  the  middle 
of  the  bone  the  front  surface  seems  to  twist  into  the  upper,  and  the  anterior  inferior 
border  becomes  the  front  border  of  the  outer  end.  Of  the  posterior  borders,  the 
upper,  though  rounded,  is  distinct  along  the  middle  of  the  bone  ;  the  lower  is  very 
vague,  but  usually  is  well  defined  in  the  outer  part  ;  when  it  is  not,  the  posterior 
surface  seems  to  twist  into  the  lower. 

The  inner  or  sternal  extremity '  is  club-shaped,  drawn  out  downward  and 
somewhat  backward.  Its  inner  surface,  coated  with  articular  cartilage,  is  of  very 
variable  shape.  It  is  approximately  oval,  with  the  long  axis  slanting  downward  and 
backward,  and  is  rough  and  generally  concave,  but  not  always  so.  The  front  edge 
of  the  inner  surface  forms  an  acute  angle  with  the  anterior  border  of  the  bone,  and 
the  hind  one  an  obtuse  angle. 

The  outer  or  acromial  extremity  -  is  flattened  above  and  below  and  curved 

forward.      At  the  very  front  of  this  end  is 

Fig.  277.  an  articular  surface  joining  the  scapula.      It 

A  is  oval,  with  the  long  axis  horizontal,  and 

usually  faces  downward  as  well  as  outward. 

There  is  generally  behind  this  a  rough  space 

for  ligament  at  the  end,   which   gradually 

slants  into  the  hind  border.      The   conoid 

tubercle 3  is  at  the  posterior  border  of  the 

lower  surface  of  the  outer  extremity  just  at 

its  junction  with  the  shaft.      The  trapezoid 

ridge  extends  from  it  forward  and  outward 

tre0/slfic^rtn00^clavicInrf/'«tbJ,rt!;i;nmC^tCrn"     across   the  bone.      Its    anterior  portion  is 

tre;  o,  c,  cartilaginous  ends,     .0,  at  about  eighteen  .  1       •  i 

years ;  d,  sterna!  epiphysis.  often  broad.      This  tubercle  and  ridge  are 

for  the  insertion  of  ligaments  of  correspond- 
ing names,  passing  upward  from  the  base  of  the  coracoid.  Between  the  ridge  and 
the  end  of  the  bone  there  is  a  smooth  space,  sometimes  almost  a  groove,  which  lies 
above  the  supraspinatus  muscle  as  it  crosses  the  shoulder-joint.  The  clavicle  varies 
greatly  in  length,  thickness,  amount  of  curve,  and  in  the  outline  of  the  ends.  Some- 
times the  outer  end  is  but  little  broader  than  the  shaft.  A  very  rare  form  is  one  in 
which  the  inner  part  of  the  shaft  is  flat  and  but  slightly  thicker  than  the  outer. 

Differences  due  to  Sex. — The  male  bone  is  longer,  stronger,  more  curved, 
and  with  larger  articular  facets.  Apart  from  sex,  a  strong  bone  is  generally  more 
curved. 

Development. — -The  centre  for  this  bone,  evident  in  the  sixth  week,  precedes 
all  others.  It  is  remarkable  as  developing  in  indifferent  tissue  before  any  hint  of  the 
bone  is  to  be  seen.  A  little  later  a  cartilaginous  outline  appears,  which  is  shortly 
involved  in  the  ossifying  process.  At  about  seventeen  a  centre  is  formed  in  the 
epiphysis  at  the  sternal  end,  and  joins  the  shaft  a  year  or  so  later. 

Surface  Anatomy. — In  life  the  anterior  surface  and  edge,  as  well  as  the 
superior  surface,  are  easily  felt  through  the  skin.  The  joint  with  the  acromion  is  dis- 
tinct, the  clavicle  being  higher  than  the  scapula.  The  position  of  the  bone  is  nearly 
horizontal,  but  in  strong  men  the  outer  end  is  often  the  higher.  The  bone  is  highly 
elastic,  owing  to  its  curves. 

PRACTICAL   CONSIDERATIONS. 
The  chief  function  of  the  clavicle  is  to  steady  the  shoulder  and  keep  the  upper 
arm  at  such  a  distance  from  the  trunk  that  the  muscles  running  from  the  latter  to 
the  humerus  may  give  it  lateral  motion.      Therefore,  in  animals,  in  which  no  such 

1  Extremitas  stemalis.     -  Extremitas  acromialis.     •'' Tuberositas  c 


PRACTICAL   CONSIDERATIONS  :   THE   CLAVICLE.  259 

movement  exists,  and  the  fore-limbs  are  used  only  in  progression,  no  clavicle,  or  a 
mere  rudiment  of  it,  is  present. 

Congenital  absence  of  both  clavicles  is  rare.  In  several  reported  cases  the 
shoulders  could  be  brought  together  in  front  of  the  body.  The  congenital  absence 
of  both  acromial  ends  is  not  so  uncommon.  Theoretically,  one  would  expect,  as  a 
result  of  absence  of  the  clavicle,  a  weakened  upper  extremity,  some  lateral  curvature 
of  the  spine,  interference  with  the  upper  chest  (from  the  weight  of  the  arm  and 
scapula),  and  hence  diminished  lung  capacity  with  the  secondary  ill  effects  upon 
growth,  nutrition,  etc. 

Such  consequences  were  predicated  (Maunder)  as  a  result  of  arrest  of  growth 
from  epiphyseal  separation,  but  neither  in  those  cases,  in  non-union  after  fracture, 
nor  in  congenital  absence  have  they  been  noted.  On  the  contrary,  in  the  four 
cases  of  symmetrical  absence  of  the  acromial  end  recorded  by  Gegenbaur  the  func- 
tional disability  was  slight,  the  motions  of  the  scapula  being  unimpaired. 

The  whole  bone  becomes  ossified  very  early,  beginning  before  any  other  long 
bone  of  the  skeleton.  Its  one  epiphysis,  at  the  sternal  end,  is,  on  the  contrary,  the 
last  of  the  epiphyses  of  the  long  bones  to  ossify,  appearing  about  the  seventeenth  or 
eighteenth  year  and,  according  to  Poland,  joining  the  diapbysis  from  the  twenty- 
second  to  the  twenty-fifth  year.      Dwight  places  the  time  of  union  somewhat  earlier. 

Separation  of  this  epiphysis  is  among  the  rarest  of  epiphyseal  detachments. 
But  five  cases  have  been  recorded.  Two  of  them  were  from  muscular  action,  the 
pectoralis  major  and  the  clavicular  fibres  of  the  deltoid  being  apparently  the  agencies 
that  carried  the  sternal  end  of  the  diaphysis  forward. 

The  age  of  the  patient  (from  seventeen  to  twenty-five),  the  shape  of  the  flattened 
diaphyseal  end  (unlike  the  pointed  end  of  a  fractured  bone),  and  the  integrity  of  the 
shape  of  the  suprasternal  notch  aid  in  distinguishing  this  accident  from  a  forward 
dislocation  or  a  fracture  on  the  inner  side  of  the  costo-clavicular  ligament. 

Fracture  of  the  clavicle  is  more  common  than  that  of  any  other  bone,  except  possi- 
bly the  radius  ;  it  is,  likewise,  the  most  frequent  seat  of  incomplete  (  "  greenstick"  ) 
fracture.  About  one-half  of  all  clavicular  fractures  occur  during  early  childhood. 
This  frequency  is  due  (1)  to  the  early  ossification  of  the  bone,  so  that  it  is  relatively 
more  brittle  than  are  the  other  bones  ;  (2)  to  the  lack  of  close  attachment  between 
the  periosteum  and  the  bone  ;  (3)  to  the  unusual  thickness  of  the  periosteum  (prob- 
ably associated  with  the  early  ossification),  which  tends  to  prevent  complete  fracture  ; 
and  (4)  to  the  common  occurrence  of  falls  and  minor  accidents  among  children. 

The  amount  of  disability  is  often  surprisingly  slight,  and  the  diagnosis,  unless 
confirmed  by  skiagraphic  testimony,  may  have  to  be  made  on  the  basis  of  very  trifling 
deformity  with  localized  tenderness  and  swelling. 

Muscular  action  may  produce  fracture  through  the  violent  contraction  of  the 
pectoralis  major  or  of  the  clavicular  portion  of  the  deltoid. 

Indirect  violence  (received  through  falls  on  the  hand,  elbow,  or  shoulder)  is 
the  common  cause.  The  frequency  with  which  such  falls  occur,  and  the  uniformity 
with  which  the  force  is  transmitted  to  a  slender  bone  containing  but  little  cancellous 
tissue,  and  held  firmly  at  either  end  by  strong  ligamentous  attachments,  sufficiently 
explain  the  common  occurrence  of  clavicular  fracture. 

The  break  usually  occurs  about  the  junction  of  the  middle  and  outer  thirds, 
because :  ( 1 )  the  outer  end  (like  the  inner)  is  firmly  held  by  the  ligamentous  connec- 
tions, the  middle  of  the  bone  being  the  most  movable  ;  (2)  at  the  outer  end  of  the 
middle  third  the  bone  is  smaller,  and  therefore  weaker  ;  (3)  at  this  point  the  sternal 
curve  (convex  forward)  and  the  acromial  curve  (concave  forward)  meet,  and  force 
applied  to  the  extremity  of  the  bone  is  there  expended. 

Fracture  of  the  clavicle  is  rarely  compound,  because,  although  the  bone  is  sub- 
cutaneous, the  skin  is  very  freely  movable  over  it,  and  because  the  usual  displace- 
ment carries  the  sharp  end  of  the  outer  fragment  backward  and  the  sharp  end  of 
the  inner  fragment  upward  (Fig.  278). 

The  anatomical  causes  of  the  common  form  of  displacement  will  be  considered 
in  connection  with  the  muscles  concerned  (page  579). 

The  relations  of  the  clavicle  to  great  vessels  and  nerve-trunks  would  seem  to 
render  frequent  complications  probable,  but  as  a  matter  of  fact  the  latter  occur  with 


260 


HUMAN   ANATOMY. 


Fig.  27S. 


Lines  of  fracture  of  the  clavicl 


nd  acromion  process. 


comparative  rarity  :  ( 1 )  because  of  the  elastic  curves  of  the  bone,  which  enable 
it  to  escape  fracture  in  many  cases  of  direct  violence  ;  (2)  because  of  the  inter- 
position of  the  subclavius  muscle  between  the  bone  and  the  nervous  and  vascular 
trunks  ;  (3)  because  of  the  situation  of  the  common  fracture,  the  inner  end  of 
the  outer  fragment  (the  portion  most  likely  to  inflict  injury)  being  both  above  and 
external  to  the  region  of  danger.      Still,  cases  of  wound  of  the  subclavian  vessels, 

internal  jugular  vein,  and  of  pressure  pa- 
ralysis of  the  upper  extremity  have  been 
reported  as  complications  of  fracture  of 
the  clavicle. 

The  supraclavicular  nerves  (branches 
of  the  third  and  fourth  cervical)  pass  in 
front  of  the  bone,  and  may  be  involved  in 
the  callus,  giving  rise  to  severe  and  per- 
sistent pain. 

In  resectioji  or  excision  of  the  clavi- 
cle, either  for  disease  or  as  a  step  in  the 
performance  of  an  interscapulo-thoracic 
amputation,  the  protection  afforded  the 
vessels  by  the  subclavius  muscle  should 
be  remembered.  Superficially,  the  cephalic  vein  and  the  supraclavicular  nerves  may 
have  to  be  divided. 

Disease  of  the  clavicle  is  not  uncommon  as  a  result  of  the  various  infections, — 
syphilitic,  tuberculous,  typhoidal,  etc.  The  bone  is  also  the  subject  of  new  growths, 
especially  of  sarcomata.  The  anatomical  relations  already  alluded  to  are  those  chiefly 
involved  in  these  cases. 

Swelling  and  oedema  of  the  arm  may  result  from  pressure  on  the  subclavian 
vein  in  the  angle  between  the  clavicle  and  the  rib  ;  gangrene,  from  pressure  upon 
the  artery  ;  pain  or  paralysis,  from  pressure  upon  the  brachial  plexus  at  the  outer 
part  of  the  costo-clavicular  space.  It  is  probable  that,  in  view  of  the  subcutaneous 
position  of  the  clavicle  and  its  consequent  exposure  to  slight  traumatisms,  osteitis  of 
one  form  or  another  would  be  more  frequent  if  it  were  not  for  its  great  elasticity, 
which  probably  limits  the  effect  of  minor  blows  to  the  superficies  of  the  bone.  Ac- 
cordingly, syphilitic  subperiosteal  nodes  are  fairly  common,  while  tuberculosis  and 
septic  and  post-typhoidal  osteitis  are  relatively  rare. 

Landmarks. — The  clavicle  is  subcutaneous  through  its  entire  length.  When 
at  rest  the  bone  is  about  on  the  same  level  as  the  spine  of  the  scapula.  In  inspira- 
tion it  moves  forward  an  inch. 

The  inner  end  of  the  bone  is  its  largest  portion,  and  its  projection  in  front  of 
and  above  the  clavicular  notch  on  the  sternum  should  not  be  erroneously  regarded 
as  evidence  of  disease  or  injury.  The  deltoid  tubercle  at  its  outer  third  is  sometimes 
unusually  prominent,  and  should  not  then  be  mistaken  for  an  exostosis. 

The  curves  of  the  bone  may  easily  be  traced  from  end  to  end.  The  normal 
curves  may  be  increased  in  greenstick  fracture  without  any  positive  angularity  being 
produced  ;  but  in  this  case  careful  measurement  will  show  that  the  distance  between 
the  two  ends  of  the  bone  is  slightly  lessened  as  compared  with  the  uninjured  side. 
It  should  not  be  forgotten,  however,  that  the  curves  are  apt  to  be  increased  in  mus- 
cular persons,  and  that  for  the  same  reason  the  right  clavicle  is  sometimes  more 
curved,  thicker,  and  a  little  shorter  than  the  left. 

In  general  terms  it  may  be  said  that  the  inner  third  of  the  bone  is  in  relation 
below  to  the  first  rib,  which  it  crosses  obliquely  ;  the  middle  third  to  the  axillary 
vessels  and  the  brachial  plexus  (and  below  them  to  the  first  intercostal  space);  and 
the  outer  third  to  the  coracoid  process  and  the  acromio-clavicular  joint  (Fig.  274). 
In  the  male,  and  in  robust,  vigorous  persons  generally,  the  clavicles  are  on  a  high 
plane  and  pass  almost  horizontally  outward,  giving  the  "square-shouldered"  appear- 
ance usually  associated  with  ideas  of  muscular  strength  and  decreasing  the  apparent 
length  of  the  neck.  In  the  strong  male  the  outer  end  may  even  be  higher  than  the 
inner. 

In  narrow-chested  and  in  consumptive  persons  the  clavicles  are  depressed  and 


THE   STERNO-CLAVICULAR    ARTICULATION. 


261 


incline  downward,  and  hence  the  sloping  narrow  shoulders  and  long  necks  so  often 
seen  in  feeble  or  in  phthisical  individuals. 

In  very  fat  persons,  in  those  suffering  from  organic  heart  disease  attended  with 
dyspncea,  and  in  emphysematous  subjects  the  clavicles  are  raised  and  the  neck 
thereby  apparently  shortened. 

THE   STERNO-CLAVICULAR    ARTICULATION. 

This  is  the  only  joint  between  the  trunk  and  the  upper  extremity.      The  socket 

on  the  upper  angle  of  the  manubrium  is  coated  with  cartilage  which  often  extends 

a  little  onto  the  first  costal   cartilage.     This  very  shallow  socket  is  made  rather 

more  secure  by  the  forward  inclination  of  the  manubrium  and  also  by  being  rather 

Fig.  279. 


m 

First  costal  cartilage 


First  costal  cartilage 


Stemo-clavicular  articulations  from  before  ;  clavicles  horizontal. 

more  on  the  back  than  on  the  front  of  that  bone,  so  that  to  some  extent  it  over- 
laps the  front  of  the  clavicle.  The  very  irregular  end  of  the  clavicle  is  coated  with 
cartilage,  which,  however,  gives  it  no  regular  nor  constant  shape.  As  a  rule,  it 
is  concave  from  before  backward,  but  there  is  often  a  swelling  at  the  posterior 
lower  angle. 

The  interarticular  fibro-cartilage '  (Fig.  280),  a  disk  subdividing  the  joint 
into  two,  is  the  chief  factor  in  maintaining  the  great  security  of  the  joint.      It  is  a 

Fig.  280. 


XV   ,1 


ml ill  lli'1/ 


Right  sterno-clavicular  joint  opened.     Left  clavicle  raised  to  show  rhomboid  ligament.     Front  view. 

rounded  disk,  thinnest  in  the  middle  and  generally  thickest  at  the  upper  border, 
which  is  attached  to  the  upper  edge  of  the  inner  end  of  the  clavicle,  while  the  lower 
border  is  attached  to  the  first  costal  cartilage  at  the  outer  border  of  the  joint.  In 
the  main  it  faces  upward  and  outward,  so  that  the  clavicle  rests  upon  it.  It  is  said 
to  be  sometimes  perforated. 


262  HUMAN    ANATOMY. 

The  capsule  (Fig.  280)  surrounds  the  joint,  being  attached  to  the  borders  of 
the  articular  surfaces  and  also  to  the  borders  of  the  interarticular  disk.  It  is 
strengthened  before  and  behind  by  bands  running  upward  and  outward  from  the  ster- 
num, of  which  the  posterior  are  the  stronger,  and  sends  some  deep  fibres  to  the  disk. 
These  bands  strengthening  the  capsule  are  sometimes  described  as  the  anterior  and 
posterior  stemo- clavicular  ligaments.      There  are  two  distinct  synovial  cavities. 

The  interclavicular  ligament  (Fig.  279)  is  a  fairly  well-defined  band  run- 
ning from  the  top  of  one  clavicle  across  to  the  other.  It  is  closely  connected  with  the 
top  of  the  joint  and  loosely  with  the  top  of  the  sternum,  towards  which  it  sinks  with 
a  slight  curve.      This  does  much  towards  filling  up  the  deep  interclavicular  notch. 

The  costo-clavicular '  or  rhomboid  ligament  (Fig.  280)  arises  from  the 
costal  cartilage  just  outside  of  the  joint,  with  which  it  is  loosely  connected,  and  runs 
upward  and  outward  to  the  rough  rhomboid  impression  on  the  under  side  of  the 
clavicle.      It  is  a  layer  of  strong,  short  fibres. 

THE   SCAPULO-CLAVICULAR    ARTICULATION. 

The  Acromio-Clavicular  Articulation. — This  joint  includes  a  capsular 
ligament  (Fig.  274)  and  occasionally  an  intra-articular  fibro-cartilage.  The  elongated 
facet  on  each  bone  is  covered  with  articular  cartilage,  that  of  the  clavicle  usually 
overlapping  the  other. 

The  capsule  is  weak,  except  above  and  behind,  where  there  are  strong  bands 
extending  outward  from  the  clavicle.      Of  these  the  posterior  are  the  longer. 

The  fibro-cartilage,  when  present,  is  wedge-shaped,  attached  by  the  base  to 
the  superior  part  of  the  capsule,  the  thin  edge  reaching,  perhaps,  half-way  through 
the  cavity  of  the  joint.  Sometimes  it  divides  the  joint  into  two.  There  may  be 
merely  a  thick  pad  of  fibrous  tissue  attached  to  the  outer  end  of  the  clavicle  with 
only  a  very  rudimentary  joint. 

The  coraco-clavicular  ligament  is  an  important  ligamentous  apparatus 
divided  into  an  outer  part,  the  trapezoid,  and  an  inner,  the  conoid  (Fig.  289).  These 
are  continuous  behind,  but  diverge  in  front.  The  trapezoid  ligament2  is  a  four- 
sided  layer  of  parallel  fibres,  springing  from  the  trapezoid  ridge  and  the  top  of  the 
first  part  of  the  coracoid,  to  run  outward  to  the  trapezoid  ridge  on  the  under  side  of 
the  clavicle.  The  line  of  attachment  to  the  clavicle  is  usually  the  longer,  and,  as  this 
runs  forward  and  outward,  the  anterior  fibres  are  almost  horizontal.  The  conoid 
ligament,3  or  inner  part,  is  less  strong.  It  arises  from  the  posterior  border  of  the 
conoid  tubercle  at  the  root  of  the  acromion,  and  runs  to  the  tubercle  of  the  same 
name  at  the  back  of  the  under  side  of  the  clavicle.  Both  these  tubercles  being 
prominences  of  some  size,  this  ligament  is  not  a  cord,  as  might  be  inferred,  but 
another  layer  continuous  with  the  trapezoid  behind.  The  inner  fibres  incline  inward 
as  they  ascend.  The  general  direction  is  upward  and  perhaps  a  little  backward,  but 
this  changes  with  the  position  of  the  bones.  There  may  be  a  synovial  bursa  in  the 
open  angle  seen  from  the  front  between  these  two  parts  of  the  ligament. 

Movements  of  the  Clavicle  and  Scapula. — The  compound  joint  at  the 
inner  end  of  the  clavicle  is  practically  a  universal  one.  The  clavicle  can  be  raised, 
depressed,  carried  forward  or  backward,  circumducted,  and  slightly  rotated.  The 
outer  and  lower  end  of  the  disk  being  attached  to  the  corresponding  border  of  the 
facet,  it  follows  that  the  clavicle  lies  upon  it.  When  the  shoulder  is  raised  or 
depressed  the  motion  is  almost  wholly  between  the  clavicle  and  the  disk,  though  the 
latter  slides  a  little,  and  in  marked  falling  of  the  shoulder  the  top  of  the  disk  starts 
to  come  out  of  the  socket,  but  is  restrained  by  the  top  of  the  capsule.  Forward  and 
backward  motions  occur  chiefly  between  the  disk  and  the  sternum,  but  there  is  some 
displacement  of  the  former.  Circumduction,  therefore,  involves  both  parts  of  the 
joint  ;  rotation  is  chiefly  in  the  inner  one. 

It  is  remarkable  that  a  joint  at  which  there  is  so  much  strain,  owing  to  leverage, 
should  be  so  strong  with  such  apparently  imperfect  bony  arrangements  for  retention. 
Part  of  the  safety  is  due  to  the  subdivision  of  the  joint  and  a  great  deal  to  the  assist- 
ance of  muscles.  At  both  ends  of  the  clavicle,  as  Morris  has  pointed  out,  the  great 
muscles  are  so  placed  that  by  their  contraction  they  draw  the  bones  together. 

1  Lie.  costoclavicularc.     2  Llg.  trapezoldeum.     3  Lig.  conoideum. 


MOVEMENTS   OF   THE   CLAVICLE   AND    SCAPULA.  263 

The  obvious  advantage  of  a  joint  between  the  clavicle  and  the  acromion,  apart 
from  breaking  shocks  and  making  the  shoulder-girdle  much  more  elastic,  is  that  it 
allows  the  angle  between  the  bones  to  change  with  the  position  of  the  arm,  and  thus 
the  direction  of  the  glenoid  cavity  may  be  modified  so  as  to  give  the  best  support  to 
the  arm  in  different  positions.  The  motion  at  the  outer  end  of  the  clavicle  is  con- 
siderable, but  indefinite.  The  overlapping  clavicle  can  advance  a  little  laterally 
onto  the  acromion,  except  in  the  cases  in  which  the  plane  of  the  joint  is  vertical. 
There  is  also  motion  on  an  approximately  vertical  axis  when  the  shoulder  is  thrown 
forward  and  the  outer  end  of  the  clavicle  advances,  the  angle  between  the  back  of 
the  clavicle  and  the  spine  of  the  scapula  being  diminished.  When  the  clavicle  can 
advance  no  farther,  the  tension  of  the  trapezoid  ligament  checks  the  progress  of  the 
coracoid.  In  the  withdrawal  of  the  shoulder  the  reverse  occurs,  the  movement 
being  finally  checked  by  the  conoid.  In  up-and-down  movements  of  the  shoulder 
the  motion  is  on  an  approximately  antero-posterior  axis.  When  it  rises  the  base  of 
the  coracoid  comes  into  direct  contact  with  the  clavicle  and  the  rhomboid  ligament 
is  strained  ;  when  it  falls  the  clavicle  rests  on  the  first  rib  and  the  conoid  is  put  on 
the  stretch,  as  are  also  the  interclavicular  ligament  and  the  top  of  the  capsule  of  the 
sternal  end.  Probably  the  freest  movement  is  when  the  arm  is  raised  vertically,  in 
which  case  the  lower  angle  of  the  scapula  swings  strongly  forward  so  as  to  direct  the 
glenoid  cavity  more  nearly  upward.  The  clavicle  rises  from  the  sternal  end,  and 
perhaps  slightly  rotates.  Possibly  the  lower  end  of  the  scapula  is  withdrawn  slightly 
from  the  chest.  Apart  from  the  movements  of  the  arm  the  scapula  may  change  its 
position  considerably.  It  may  rotate  on  either  the  end  of  the  acromion  (as  in  rais- 
ing the  arm)  or  on  the  superior  angle,  the  lower  angle  being  the  most  movable 
point.  When  it  is  carried  far  forward  a  larger  portion  of  the  posterior  surface  of 
the  lungs  can  be  examined.  The  scapulae  may  also  be  raised  or  brought  nearer 
together. 

Surface  Anatomy  of  the  Shoulder-Girdle. — The  general  shape  of  the 
clavicle  is  easily  made  out  by  pressing  on  its  front  and  superior  surfaces  with  the 
muscles  relaxed.  The  degree  of  backward  projection  of  the  inner  end  can  be  deter- 
mined. It  is  placed  horizontally  in  woman  ;  in  man  the  outer  end  is  slightly  raised. 
The  joint  with  the  acromion  is  easily  felt  from  above,  the  clavicle  being  the  higher. 
The  outline  of  the  acromion,  which  slopes  somewhat  downward,  is  easily  felt.  It 
forms  the  point  of  the  shoulder-girdle,  but  not  of  the  shoulder,  as  the  humerus 
always  projects  beyond  it  externally.  A  plane  vertical  surface  placed  against  the 
outside  of  the  shoulder  cannot  touch  the  acromion  if  the  head  of  the  humerus  is  in 
place.  The  possibility  that  the  outer  epiphysis  of  the  acromion  may  not  unite  by 
bone  is  to  be  remembered.  The  finger  can  be  carried  from  the  acromion  along  the 
spine  to  its  triangular  origin.  The  tip  of  the  coracoid  is  to  be  felt  by  manipulation 
in  the  infraclavicular  fossa  at  the  inner  side  of  the  humerus.  The  posterior  border 
of  the  scapula  is  always  to  be  felt  ;  in  thin  persons  its  outline  can  be  traced  and  the 
shape  of  the  inferior  angle  approximately  recognized. 

PRACTICAL   CONSIDERATIONS. 

The  Sterno-Clavicular  Articulation. — The  interposition  of  an  elastic  buffer 
in  the  shape  of  the  interarticular  fibro-cartilage,  united  to  both  the  bones  by  very 
strong  ligamentous  fibres,  and  completely  bisecting  the  joint  (Fig.  280),  in  fact, 
converting  it  into  two  separate  joints,  prevents  the  clavicle  from  transmitting  to  the 
sternum  the  full  force  of  blows  and  falls  received  upon  the  hand  or  shoulder,  and 
allows  of  the  varied,  though  limited,  movements  of  the  articulation. 

Dislocation  is  rare.  The  ligaments  are  stronger  than  the  clavicle,  which  is 
therefore  usually  broken  by  any  force  sufficient  to  threaten  the  integrity  of  the  joint. 
The  curves  of  the  clavicle,  the  mobility  of  the  scapula,  and  the  play  of  the  acromio- 
clavicular joint  all  tend  to  diffuse  forces  that  might  otherwise  have  been  expended 
on  this  articulation,  which  is  furthermore  strengthened  by  the  tendinous  origins 
of  the  sterno-cleido-mastoid  and  of  the  pectoralis  major. 

The  most  common  form  of  dislocation  is  the  forward  one,  the  anterior  sterno- 
clavicular  ligament    being   the   weaker   and    thinner.       Backward    luxation    is    re- 


264  HUMAN   ANATOMY. 

sisted  by  the  more  powerful  posterior  ligament  and  by  the  rhomboid.  Upward 
displacement — the  least  frequent — is  resisted  by  the  interarticular  cartilage,  which  is 
strongly  inserted  below  into  the  cartilage  of  the  first  rib  and  the  sternum,  and  above 
into  the  clavicle  itself,  by  the  rhomboid  and  interclavicular  ligaments  and  by  both 
the  anterior  and  posterior  ligaments  ;  hence  the  rarity  of  this  luxation. 

In  many  displacements  of  the  sternal  end  of  the  clavicle  the  shoulder  is  carried 
downward  or  backward  until  the  clavicle  is  in  contact  with  the  strong  first  rib,  which 
then  acts  as  a  fulcrum,  the  sternal  end  of  the  bone  continuing  its  upward  or  forward 
motion  until  the  resisting  ligaments  are  torn  and  the  luxation  is  produced. 

In  backward  dislocation  by  indirect  violence  the  force  has  usually  pushed  the 
shoulder  forward  and  inward,  as  when  the  patient  has  been  caught  between  two  cars 
or  between  a  wall  and  a  wagon. 

In  this  dislocation  the  sternal  end  may  press  upon  the  trachea,  the  internal 
jugular,  or  the  beginning  of  the  innominate  vein,  and  may  therefore,  if  the  faulty 
position  has  become  permanent,  require  excision. 

Disease  of  the  sterno-clavicular  joint  is  not  very  common,  considering  its  super- 
ficial position  and  its  constant  motion.  This  is  probably  due  to  the  fact  that  the 
motion  is  slight  and  that  strains  and  injury  to  the  synovial  membranes  are  prevented 
by  the  strong  and  elastic  interarticular  cartilage  and  by  the  strength  of  the  ligaments. 
Suppuration  usually  shows  itself  in  front  (as  the  anterior  ligament  is  the  thinnest), 
but  may  perforate  by  ulceration  the  posterior  ligament  and  find  its  way  to  the  medi- 
astinum. With  the  arm  at  the  side  the  articulation  becomes  V-shaped,  the  clavicle 
touching  the  joint  surface  only  at  its  lowest  angle.  With  the  arm  elevated,  the  two 
joint  surfaces  are  brought  into  closer  relation,  and  the  shape  of  the  joint  viewed  from 
the  front  becomes  linear  ;  hence  raising  of  the  arm  is  uniformly  productive  of  pain 
in  disease  of  the  joint. 

Ankylosis  is  rare,  probably  owing  to  the  separation  of  the  diseased  joint  surfaces 
by  the  thick,  resistant  fibro-cartilage. 

The  Acromio-Clavicular  Articulation. — This  is  one  of  the  shallowest  of 
the  articulations,  the  clavicle  being  merely  superimposed,  as  it  were,  upon  the  upper 
edge  of  the  acromion.  The  powerful  ligaments  which  bind  the  clavicle  to  the  cora- 
coid  (the  conoid  and  trapezoid),  although  they  have  no  direct  relation  to  the  joint, 
are  the  most  important  factors  in  preserving  its  integrity  when  force  is  applied  to  the 
point  of  the  shoulder. 

The  movements  of  the  joint  are  around  two  axes,  an  antero-posterior  and  a 
vertical  one,  so  that  the  relations  of  the  glenoid  cavity  to  the  humerus  may  remain 
relatively  unchanged  when  the  arm  is  elevated  or  is  advanced.  The  scapula  must 
obviously  move  backward  or  forward  on  the  side  of  the  chest  in  a  curve  established 
by  the  curve  of  the  ribs.  It  does  this  on  a  radius  represented  by  the  clavicle,  the 
centre  of  the  rotation  being  at  the  sterno-clavicular  joint.  The  acromio-clavicular 
joint  enables  this  motion  to  take  place,  while  at  the  same  time  the  glenoid  cavity 
continues  to  point  obliquely  forward.  If  it  were  not  for  this,  the  act  of  pushing 
or  striking  with  the  arm  advanced,  or  of  falling  upon  the  hand  with  the  arm  in 
a  like  position,  would  bring  the  head  of  the  humerus  against  the  capsule  of  the  joint 
instead  of  against  the  glenoid  cavity,  and  would  thus  increase  the  frequency  of 
luxation.  Conversely,  "rigidity  of  this  little  joint  may  be  a  cause  of  insecurity  in 
the  articulation  of  the  shoulder  and  of  weakness  in  certain  movements  of  the  limb" 
(Treves). 

Dislocation  is  rare.  The  dislocation  of  the  acromial  end  of  the  clavicle  upward 
(described  by  some  surgical  writers,  for  the  sake  of  uniformity,  as  dislocation  of  the 
scapula  downward)  is  much  the  more  frequent.  The  capsular  ligament  is  torn  or 
stretched,  even  in  the  incomplete  forms.  In  the  complete  variety  the  coraco- 
clavicular  ligaments  must  be  torn  or  ruptured,  but  their  great  strength,  increased  in 
effectiveness  by  their  distance  from  the  joint,  renders  this  accident  uncommon. 

Dislocation  of  the  clavicle  beneath  the  acromion — between  it  and  the  coracoid 
process — and  dislocation  of  the  clavicle  beneath  the  coracoid  are  extremely  rare 
accidents.  It  is  not  certain  that  the  latter  has  ever  occurred.  Both  obviously 
require  for  their  production  extensive  laceration  of  all  of  the  ligaments  binding 
together  the  scapula  and  the  outer  portion  of  the  clavicle. 


THE    HUMERUS.  265 

THE    HUMERUS. 

The  bone  of  the  arm  consists  of  a  shaft  and  two  enlarged  extremities. 

The  upper  extremity  includes  a  globular  articular  head  and  two  hcberosilies 
for  muscular  insertions.  The  head1  looks  upward,  inward,  and  backward.  It  is 
not  truly  a  part  of  a  sphere,  for  the  curve  in  the  horizontal  plane  is  bolder  than  that 
in  the  vertical.  The  vertical  diameter  between  the  edges  of  the  articular  surface  is 
longer  than  the  transverse.  It  is  surrounded  by  a  slight  groove  for  the  attachment 
of  the  capsular  ligament  at  what  is  called  the  anatotnical  neck. 2  The  surgical  neck 3  is 
just  below  the  whole  upper  extremity.  The  tuberosities  are  separated  in  front  by  a 
deep  furrow,  the  bicipital  groove^  through  which  runs  the  tendon  of  the  long  head 
of  the  biceps.  The  greater  tuberosity5  is  a  rough  enlargement  placed  externally. 
Its  highest  point  is  at  the  front,  just  by  the  groove.  A  superior  surface  of  this 
tuberosity  begins  here  and,  passing  downward  and  backward  beside  the  head, 
broadens  as  it  goes.  It  bears  three  smooth  facets  for  the  insertion  of  the  supra- 
spinatus,  the  infraspinatus,  and  the  teres  minor,  in  this  order  ;  the  first  being  highest 
and  most  in  front,  the  last  and  lowest  most  behind.  The  lesser  tuberosity,6  much 
smaller,  is  on  the  front  of  the  bone.  It  bears  a  prominent  angle,  sometimes  an 
actual  crest  running  downward  and  inward  for  the  subscapularis.  The  upper  aspect 
of  the  process,  which  looks  also  inward,  is  smooth  for  a  bursa  beneath  the  tendon. 

The  shaft  is  roughly  cylindrical  above  and  prismatic  below.  It  is  convenient 
to  divide  it  by  three  borders  into  three  surfaces.  The  a?iterior  border  starts  from 
the  greater  tuberosity  as  the  outer  lip  of  the  bicipital  groove,  which,  growing 
shallower,  can  be  traced  through  the  first  quarter  of  the  shaft.  This  outer  lip 
becomes  thicker  and  more  prominent  for  some  two  inches  below  the  surgical  neck 
to  receive  the  insertion  of  the  pectoralis  major.  Below  this  it  is  joined  by  the  lower 
end  of  the  deltoid  eminence,  after  which,  smooth  and  rounded,  it  grows  fainter,  but 
may  be  traced  downward  to  a  ridge  separating  the  capitellum  from  the  trochlea, 
where  it  ends.  The  internal  border  starts  at  the  .inner  side  of  the  neck,  often  so 
near  the  inner  lip  of  the  bicipital  groove  as  to  be  confounded  with  it,  and  runs 
straight  down  to  the  very  tip  of  the  internal  condyle.  It  is  at  best  very  faint  in  the 
first  quarter,  and  often  barely  visible  ;  but  it  is  distinct  in  the  middle  and  prominent 
in  the  last  third,  where  it  is  known  as  the  internal  supracondylar  ridge.  The 
external  border  begins  at  the  back  of  the  greater  tuberosity  and  runs  to  the  outer 
condyle,  the  lower  part  being  the  external  supracondylar  ridge,  which  has  a  forward 
curve.  A  great  exaggeration  of  this  ridge  has  been  seen  in  the  negro.  The  internal 
surface  bears  the  inner  lip  of  the  bicipital  groove,  which,  starting  from  the  lesser 
tuberosity,  is  often  very  faint  ;  it  receives  the  tendon  of  the  teres  major.  The 
bicipital  groove  soon  becomes  shallow,  and  is  lost  after  two  or  three  inches.  The 
nutrient  foramen,  running  downward  into  the  bone,  is  rather  below  the  middle  of 
this  surface,  sometimes  being  almost  in  the  internal  border.  The  external  surface 
is  convex  in  the  upper  half  and  concave  in  the  lower.  Its  second  quarter  is  occupied 
by  a  long,  rough  elevation,  the  deltoid  eminence,1  slanting  downward  and  forward 
against  the  interior  border  for  the  insertion  of  the  deltoid  muscle.  The  posterior 
surface  is  twisted,  facing  somewhat  inward  above  and  backward  below.  The  upper 
plane  portion  gives  origin  to  the  outer  head  of  the  triceps,  and  the  lower,  convex 
except  below,  to  the  inner  head.  A  broad  spiral  groove  beginning  on  the  external 
surface  behind  the  deltoid  eminence,  in  front  of  the  outer  border,  twists  forward  and 
downward.  This  is  generally  improperly  called  the  musculo-spiral  groove*  The 
groove  truly  deserving  that  name,  containing  the  musculo-spiral  nerve  and  the  supe- 
rior profunda  artery,  occupies  the  lower  and  posterior  part  of  the  greater  groove, 
from  which  it  usually  is  not  to  be  distinguished  throughout,  though  both  grooves 
may  be  distinct.  The  musculo-spiral  groove  is  some  five  millimetres  broad,  and, 
when  well  developed,  begins  on  the  posterior  surface,  separating  the  areas  for  the 
outer  and  inner  heads  of  the  triceps  muscle,  and  interrupts  the  external  border, 
behind  which  the  broad  spiral  groove  never  passes.  A  second  nutrient  foramen, 
also  running  downward  and  sometimes  the  larger  of  the  two,  may  occur  in  the 
groove.  The  shaft  takes  a  forward  bend  just  at  its  termination,  so  that  most  of  the 
lower  end  lies  in  front  of  the  continuation  of  the  axis  of  the  shaft. 

3  C.   chirurgicum.      ''Sulcus  iutertubercularis.     6  Tubercalam   majus.     6Tub. 


266 


HUMAN      ANATOMY. 
Fig.  28  i. 


Pectoralis  major 
Latissimus  dorsi 
Teres  major 


Coraco-brachiahs 


B  r  ackio-radia  lis 


Tendon  common 
to  exten.  carp, 
rad.  brev.,  ex- 
ten,  communis 
digit  orum,  ex- 
ten,  min.  digiti, 
exten.  carpi  ul- 


Tendon  common 
to  pronator  ra- 
dii teres,  flex, 
carpi  radialis, 
palmaris  lon- 
gus,  flex,  sub- 
lim.  dig.,  flex, 
carpi  ulnaris 


Lesser  tuberosity 


Bicipital  groove 
Internal  bicipital  ridge 


External  bicipital  or  pecto- 
ral ridge 


Brackialis  anticus  External 

border 


•Pronator  radii 


)  Anterior  border 


ternal  supracondylar  ridge 


Right  h 


Capitellum  Trochlea 

from  before.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


THE   HUMERUS, 

Fig.  282. 


267 


^  Greater  tuber- 
osity 


Surgical  neck 


\~m 


..Spiral  groove 


..Musculo-spiral 
groove 


Inner  head  of — 


External  head  of 
triceps 


Deltoid 
Brachialis  anticu 

Brachio-radialis 


U 


-Olecranon  fossa 
"External  condyle 
Groove  for  ulnar 

Right  humerus  from  behind.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


HUMAN    ANATOMY. 


Fig.  283. 


*\«N?w 


The   lower    extremity    is    broad  from  side  to  side,  with  an  articular  surface 

below,  and  two  lateral  projections,  the  condyles.  The  inner  co?idyle,1  much  the 
larger,  is  sharp  and  prominent,  giving  rise  with  a  part 
of  the  supracondylar  ridge  to  the  flexor  pronator  mus- 
cles. It  is  faintly  grooved  behind  by  the  ulnar  nerve, 
and  the  lower  part  of  the  front  often  presents  a  smooth 
surface.  The  outer  condyle 2  is  a  slightly  raised  knob. 
The  articular  surface,  most  of  which  is  at  a  lower  level 
than  the  condyles,  consists  of  two  parts, — an  inner 
pulley-like  surface,  the  trochlea,  for  the  ulna,  and  an 
outer  convexity,  the  capitellum,  for  the  radius. 

The  trochlea3  is  bounded  internally  by  a  sharp 
border,  forming  about  three-quarters  of  a  circle,  and 
projecting  below  the  rest  of  the  bone  as  well  as  before 
and  behind  it.  It  is  bounded  externally  by  a  ridge, 
which  is  prominent  behind  where  the  trochlea  forms 
the  whole  of  the  articular  surface,  but  is  faint  in  front 
where  it  separates  the  trochlea  from  the  capitellum. 
Above  the  joint  this  ridge  is  continuous  with  the  an- 
terior border  of  the  shaft. 

The  trochlea  is  convex  from  before  backward.  A 
section  through  the  middle  forms  almost  a  complete 
circle,  being  broken  only  above,  where  a  thin  plate  con- 
nects it  with  the  shaft.  It  is  concavo-convex  from  side 
to  side,  the  convexity  being  greatest  at  the  inner  bor- 
der. There  is  a  depression  above  the  trochlea  both 
before  and  behind  ;  the  former,  the  coronoid  fossa,  is 
small  and  receives  the  coronoid  process  of  the  ulna  in 
flexion  ;  the  posterior  depression,  triangular  and  much 
the  larger,  is  the  olecranon  fossa,  receiving  that  process 
in  extension.  The  bone  separating  these  fossae — the 
plate  just  alluded  to — is  so  thin  as  to  be  translucent. 
It  may  be  perforated  by  the  supratrochlear  foramen, 
most  frequently  found  in  savage  tribes.  The  joint  be- 
tween the  humerus  and  ulna  is  commonly  called  a 
hinge-joint,  but  there  are  serious  modifications.  First, 
the  axis  of  the  trochlea  is  not  at  right  angles  to  that  of 
the  shaft,  but  slants  downward  and  inward  ;  next,  the 
borders  of  the  trochlea  are  not  at  right  angles  to  its 
axis,  but  are  so  placed  as  to  transform  it  into  a  spiral 
or  screw-joint  ;  finally,  these  borders  are  not  parallel  to 
each  other,  but  the  inner  slants  downward  and  inward 
so  that  the  transverse  diameter  of  the  joint  is  greater 
below  than  at  the  top,  either  before  or  behind. 

The  capitellum,4  on  which  the  concave  head  of 
the  radius  plays,  is  situated  on  the  front  of  the  outer 
part  of  the  lower  end.  It  is  not  far  from  being  a  por- 
tion of  a  sphere,  since  it  is  convex  and  nearly  equally 
so  in  all  directions,  but  the  arc  from  above  downward 
is  the  longest.  A  groove  runs  between  it  and  the  outer 
ridge  of  the  trochlea  ;  the  outer  border  is  straight ;  the 
posterior  runs  from  it  obliquely  backward  and  inward. 
The  capitellum  is  placed  so  much  to  the  front  as  to  be 
nearly  or  quite  invisible  from  behind  ;  hence  the  articu- 
lar surface  is  much  more  extensive  on  the  front  than 

the  back.      The  radial  fossa,  a  small  depression  above  the  capitellum,  receives  the 

edge  of  the  head  of  the  radius  in  extreme  flexion. 

The  supracondylar  process  is  a  small   bony  spur   occurring    in    probably  two 

or  three  per  cent.,  which  arises  from  the  front  of  the  bone  a  little  anterior  to  the 

1  Epicondylus  medialis.     -  Epicondylus  lateralis.    3  Trochlea.    4Capituluni. 


Longitudinal  section  of  humerus, 
showing  relation  of  compact  and 
spongy  bone. 


THE    HUMERUS. 


269 


internal  supracondylar  ridge.  It  is  usually  connected  by  a  fibrous  band  to  the  tip 
of  the  inner  condyle,  thus  representing  the  supracondylar  foramen  found  very 
generally  among  mammals.  The  median  nerve  and  generally  either  the  brachial  or 
the  ulnar  artery  pass  through  it.  The  process,  without  any  completing  ligament, 
has  been  seen  hooking  over  the  nerve  alone.      We  have  once  seen  a  bony  foramen. 

The  so-called  torsion  of  the  humerus  is  a  very  complicated  problem  arising  from  the 
theory  of  the  changes  necessary  to  account  for  the  adult  condition  of  the  humerus  and  femur, 
assuming  them  to  have  been  originally  symmetrical.  The  practical  point  is  that  the  horizontal 
axis  subdividing  the  articular  surface  of  the  head  of  the  humerus,  imagined  on  the  same  plane 
as  the  transverse  axis  of  the  elbow,  forms  an  angle  with  the  latter.  This  angle  varies  consider- 
ably ;  according  to  Gegenbaur,  it  is  120  for  the  adult  European.  In  the  lower  races  it  is  greater, 
and  still  greater  in  the  lower  animals.  (This  is  what  Continental  anatomists  call  the  supple- 
mental angle,  as  they  assume  that  the  twisting  has  approached  180°,  and  that  thus  the  true 
angle  is  168°.  We  give  this  as  the  simplest. )  The  angle  is  greater  in  the  fcetus.  Gegenbaur 
gives  it  as  59°  at  from  three  to  four  months,  and  as  340  at  from  three  to  nine  months,  after  birth. 
This  change  probably  occurs  in  the  epiphyses.  It  is  certain  that  the  shaft  of  the  developing 
humerus  does  not  actually  twist,  for  the  borders  are  straight,  as  are  all  the  long  nerves  with  the 
single  exception  of  the  musculo-spiral.     No  spiral  fibres  have  been  found  in  the  bone. 

Structure. — The  walls  of  the  shaft  are  of  compact  bone  enclosing  a  cavity.  At 
the  upper  end  the  head  is  made  of  round-meshed  tissue  of  considerable  density  ;  the 
greater  tuberosity  is  of  lighter  structure  ;  both  are  enclosed  by  thin  bone.  The  line 
of  union  of  the  upper  epiphysis  is  seen  on  section  after  it  has  disappeared  from  the 
surface.  Transverse  sections  at  the  lower  end  show  a  system  of  strong  plates  passing 
obliquely  from  the  front  to  the  back  above  the  inner  condyle. 

Differences  due  to  Sex. — The  chief  guides  are  the  greater  delicacy  of  the 
female  bone,  and  especially  the  smaller  size  of  the  head.  It  is  generally  thought 
that  the  female  humerus  presents  a  sharper  angle  between  the  axis  of  the  shaft  and 
the  transverse  axis  of  the  trochlea  than  does  the  male,  but  Berteaux's  '  measurements 
make  the  difference  too  slight  to  be  significant, — 790  for  man  and  78°  for  woman. 

Development. — The  primary  centre  for  the  shaft  appears  towards  the  end  of 
the  second  fcetal  month,  and  before  birth  bone  has  reached  to  the  extremities,  which 
are  formed  by  the  union  of  several  centres.  There  are  two  or  three  for  the  upper, 
a  chief   one  for  the  head  coming   soon  after  birth  and  sometimes   earlier.       It  is 

Fig.  2S4. 


Ossification  of  humerus.  .4,  just  before  birth;  B,  in  the  first  year;  Cat  three  years;  C,  sections  of  ends  of 
preceding;  JD,  at  five  years;  E,  at  about  thirteen  years;  E',  sections  of  ends  of  preceding;  E,  at  about  sixteen  ;  F\ 
sections  of  ends  of  preceding,  a,  centre  for  shaft ;  *,  for  head  ;  c,  for  capitellum  and  part  of  trochlea  ;  d,  for  greater 
tuberosity  ;  e,  for  head  and  tuberosities  in  transverse  section  ;  /,  for  internal  condyle  ;  g,  for  inner  part  of  trochlea. 

present  at  birth  in  22.5  per  cent,  of  foetuses  weighing  seven  pounds  and  over  (Spen- 
cer2). It  is  almost  always  present  by  the  end  of  the  third  month  after  birth.  In 
the  third  year  ossification  begins  in  the  greater  tuberosity,  and  another  point  may 
appear  somewhat  later  in  the  lesser  one.      At  five  all  the  centres  for  this  end  have 


Le  Humerus  et  le  Femur,  Paris,  1S91. 
1  Journal  of  Anatomy  and  Physiology,  vol. 


1S91. 


270 


HUMAN    ANATOMY. 


become  one,  making  a  cap  for  the  top  of  the  shaft,  which  latter  extends  into  the 
head.  The  largest  centre  for  the  lower  end  is  that  for  the  capitellum,  which  is  seen 
by  the  end  of  the  first  half-year.  It  forms  also  a  part  of  the  outer  side  of  the 
trochlea.  A  centre  for  the  tip  of  the  inner  condyle  is  evident  by  the  fifth  year.  One 
or  more  minute  points  of  ossification  for  the  trochlea  appear  in  the  tenth  year,  and 
one  for  the  tip  of  the  external  condyle  in  the  fourteenth.  Although  all  these 
epiphyses  are  originally  in  the  same  strip  of  cartilage,  they  do  not  unite  into  one 
piece  of  bone.  The  capitellum  is  joined  by  the  ossification  for  the  trochlea,  and  joins 
the  shaft  at  from  fourteen  to  fifteen.  We  are  not  sure  whether  the  insignificant  centre 
for  the  outer  condyle,  which  fuses  at  about  the  same  time,  joins  the  epiphysis  or  the 
shaft.  Rambaud  and  Renault  seem  to  believe  the  latter.  The  centre  for  the  internal 
condyle  remains  separate  after  the  rest  are  fused  and  joins  the  shaft  at  about  eighteen. 
The  upper  end  joins  at  about  nineteen,  the  line  of  union  being  lost  at  twenty  or 
twenty-one.      It  is  usually  lost  earlier  in  the  female. 

Surface  Anatomy. — The  external  and  internal  condyles  are  the  only  points 
that  are  truly  subcutaneous.  The  outer  is  easily  recognized  under  normal  conditions, 
but  is  quickly  obscured  by  swelling.  The  internal  is  so  prominent  that  it  can  always 
be  recognized,  unless  the  joint  has  been  utterly  broken  to  pieces.  The  fact  that  the 
inner  condyle  joins  the  shaft  after  the  rest  of  the  lower  end  exposes  it  to  the  danger  of 
being  broken  off  before  the  union  has  occurred,  or  while  it  is  still  weak.  The  upper 
end  of  the  humerus  is  everywhere  covered  by  muscle,  but  much  of  its  outline  can  be 
explored.  The  amount  of  its  forward  projection  varies  much  ;  but  it  always  projects 
outward  beyond  the  acromion.  The  lesser  tuberosity  and  the  bicipital  groove  can 
be  recognized  on  rotating  the  bone,  but  indistinctly.  The  groove  is  filled  by  the 
tendon  and  still  further  obscured  by  the  capsule  and  muscles.  The  surgical  neck  is 
best  felt  in  the  axilla,  whence,  the  arm  being  extended,  the  head  can  be  examined, 
though  imperfectly. 

PRACTICAL   CONSIDERATIONS. 

The  humerus  occasionally  fails  to  develop,  either  alone  or  together  with  the 
other  bones  of  the  extremity.      The  bone  of  one  arm  may  be  shorter  and  thicker 
than  the    normal    bone.       Lengthening   beyond    normal 
limits  is  much  rarer. 

The  shallowness  of  the  glenoid  cavity  obviates  the 
necessity  for  projecting  the  head  of  the  bone  from  the 
shaft,  as  in  the  femur  ;  the  "neck"  is,  therefore,  merely 
a  very  narrow  and  superficially  shallow  constriction  of  an 
inward  prolongation  of  the  shaft  between  the  tuberosities 
below  and  the  joint  surface  above.  Both  its  shortness 
and  its  shallowness  render  it  far  less  liable  to  fracture  than 
the  femoral  neck.  When,  in  old  age,  absorption  and 
fatty  degeneration  of  the  cancellous  tissue  have  occurred, 
fracture  does  take  place,  as  a  result  usually  of  falls  upon 
the  shoulder.  It  is  often  accompanied  by  impaction,  the 
head  being  driven  into  the  broad  surface  of  cancellated 
tissue  on  the  upper  end  of  the  lower  fragment  (Fig.  285). 
This  results  in  a  lessening  of  the  bulk  of  the  upper  end, 
or  subacromial  portion,  of  the  humerus,  and  thus  in  a 
little  flattening  of  the  deltoid  and  a  little  increased  promi- 
nence of  the  acromion.  If  impaction  does  not  occur, 
and  the  capsule  of  the  joint  is  completely  torn  through  its 
entire  circumference,  necrosis  of  the  upper  fragment 
must  follow.  Usually,  through  untorn  periosteum  and 
through  portions  of  capsule  reflected  from  the  inner  side 
of  the  shaft  below  the  anatomical  neck  to  the  edge  of 
the  articular  cartilage  on  the  head,  the  blood-supply  is 
maintained  so  that  necrosis  is  prevented  and  union  results. 
There  is  no  direct  blood-supply  to  the  head  of  the  humerus  corresponding  to  that 
received  by  the  femoral  head  through  the  ligamentum  teres.       The  displacement 


Fracture  of  anatomical  neck  of 
humerus,  showing  impaction. 


PRACTICAL    CONSIDERATIONS  :    THE    HUMERUS. 


271 


is  apt  to  be  slight,  the  muscles  inserted  into  the  bicipital  groove  and  acting  on 
the  lower  fragment  being  antagonized  by  those  inserted  into  the  greater  tuberosity. 
That  tuberosity  may  be  torn  off  as  a  rare  accident.  The  displacement — theoreti- 
cally— will  depend  upon  the  action  of  the  muscles  inserted  into  that  portion  of  the 
bone  (page  590). 

The  large  upper  epiphysis  of  the  humerus  (made  up  of  centres  for  the  head  and 
the  tuberosities  which  begin  to  coalesce  about  the  sixth  year)  is  fully  formed  by  the 
age  of  puberty.  It  includes  then  the  two  tuberosities,  the  upper  fourth  of  the  bicipi- 
tal groove,  all  of  the  head,  the  anatomical  neck,  and  a  little  of  the  shaft  just  below  it. 
A  line  nearly  horizontal  and  crossing  the  bone  beneath  the  great  tuberosity,  and 
therefore  considerably  below  the  anatomical  neck,  represents  the  epiphyseal  line  at 
the  twentieth  year,  when  the  epiphysis  and  shaft  become  united.  It  is  within  a  half 
inch  of  the  so-called  surgical  neck  (Fig.  286). 

The  lower  surface  of  the  epiphysis  is  concave  and  the  upper  surface  of  the 
diaphysis  convex  or  conical  (Fig.  287). 


Fig.  287. 


Fig.  286. 


A ,  on  surface ; 


Upper  end  of  h 
01   epiphysis 
diaphysis. 


The  traumatic  separation  of  this  epiphysis  is  a  not  infrequent  accident  of  child- 
hood and  adolescence.  It  is  commonly  caused  by  forcible  traction  of  the  arm 
upward  and  outward.  In  such  cases  three  anatomical  factors  probably  enter  into 
the  production  of  the  lesion.  ( 1 )  The  partial  fixation  of  the  epiphysis  by  the  sub- 
scapularis,  supra-  and  infraspinatus,  and  the  upper  fibres  of  the  teres  minor.  Even 
on  the  dead  subject,  rotation  outward  with  abduction  will  most  readily  produce  the 
disjunction.  (2)  The  ease  with  which  the  periosteum,  strongly  attached  to  the 
epiphysis  but  very  loosely  to  the  diaphysis,  may  be  separated  from  the  latter.  This 
is  illustrated  by  the  fact  that  in  cases  of  detachment  the  teres  minor,  though  inserted 
below  the  epiphyseal  line,  is  apt  to  retain  its  connection  with  the  periosteum  covering 
the  epiphysis.  (3)  The  powerful  muscles  resisting  abduction  and  inserted  into  the 
diaphysis  just  below  the  epiphyseal  line. 

There  may  be  only  separation  with  little  or  no  displacement  ;  but  if  displace- 
ment occurs,  the  muscles  just  alluded  to  (the  latissimus,  pectoral,  and  teres)  tend  to 


272  HUMAN   ANATOMY. 

draw  the  diaphyseal  fragment  strongly  towards  the  chest-wall,  so  that  its  upper  end 
may  be  found  beneath  the  coracoid  process.  The  shape  of  the  opposing  surfaces  of 
the  epiphysis  and  diaphysis  lessens  both  the  frequency  and  the  amount  of  the  dis- 
placement. The  two  surfaces  usually  remain  in  contact  at  some  point:  (ij  on 
account  of  that  shape  ;  (2)  because  the  humerus  on  the  epiphyseal  line  is  broader 
than  at  any  other  part  of  its  upper  end. 

The  deformity  will  be  recurred  to  in  connection  with  that  of  the  conditions 
which  it  most  closely  resembles, — fracture  of  the  surgical  neck  and  dislocation  of 
the  humerus, — which  (on  account  of  the  importance  of  muscular  action  in  their 
production  and  in  their  treatment)  will  be  considered  after  the  muscles  have  been 
described. 

It  might  be  expected  that,  as  the  chief  growth  of  the  humerus  takes  place  from 
its  upper  epiphysis,  arrest  of  growth  and  development  should  be  a  usual  sequel. 
The  upper  epiphysis  from  the  tenth  year  to  adult  life  will,  according  to  Vogt,  add 
from  seven  to  ten  centimetres  to  the  length  of  the  humerus,  the  lower  epiphysis 
during  the  same  time  adding  but  one-fifth  as  much.  The  activity  of  the  upper 
epiphysis  is  shown  by  the  frequency  of  conical  stump  after  amputation  through  the 
upper  end  of  the  humerus.1  Despite  these  facts,  in  comparatively  few  cases  of- 
disjunction  is  atrophy  or  arrest  of  growth  reported  as  a  result.  It  has  been  sup- 
posed, too,  that  necrosis  of  the  epiphysis  should  follow  this  injury  on  account  of 
deficient  blood-supply  to  the  head  ;  but,  through  the  tuberosities,  through  the 
connection  of  the  reflected  capsule  to  the  articular  cartilage,  and  through  portions 
of  untorn  periosteum,  the  blood-supply  is  ample.  Firm  bony  union  is  therefore 
the  usual  result  in  well-treated  cases.  This  is  favored  by  the  fact,  already  alluded 
to,  that  the  opposing  surfaces  are  nearly  always  in  contact  at  some  point. 

The  portion  of  the  shaft  just  beneath  the  head  and  tuberosities  is  known  as  the 
' '  surgical  neck' '  because  it  is  so  often  the  seat  of  fracture. 

It  contains,  as  will  be  seen  on  examining  a  longitudinal  section  of  the  humerus 
(Fig.  283),  a  considerable  quantity  of  cancellous  tissue,  the  absorption  of  which  in 
old  persons  leaves  the  bone  weak  at  that  point.  The  factors  already  described  as 
favoring  epiphyseal  separation  are  operative  in  this  case  (page  271). 

The  upper  curve  of  the  bone,  beginning  on  this  level,  ends  inferiorly  at  about 
the  lower  margin  of  the  deltoid  tubercle.  Its  convexity  is  forward  and  outward. 
The  lower  curve  is  concave  forward.  Both  curves  may  be  markedly  increased 
in  rickets.  The  middle  of  the  bone  is  not  only  the  point  of  union  of  these  curves, 
but  is  also  the  smallest  and  hardest  and  least  elastic  portion  of  the  shaft  ;  hence 
it  is  most  frequently  broken,  though  fractures  of  the  shaft  at  various  levels  below 
and  above  this  point  are  not  uncommon.  The  deltoid  tubercle,  when  unusually 
developed,  should  not  be  taken  for  an  exostosis.  The  region  is,  however,  a  fre- 
quent seat  of  bony  outgrowths  on  account  of  the  insertion  and  origin,  respectively, 
of  the  coraco-brachialis  and  deltoid,  and  the  brachialis  anticus  and  internal  head  of 
the  triceps. 

The  close  attachment  of  the  periosteum  to  the  shaft  which  is  thus  necessi- 
tated favors  the  development  of  osteo-periostitis,  and  thus  of  osteophytes  as  a 
consequence  of  repeated  muscular  strains.  Other  favorite  seats  of  exostoses  are  near 
the  insertion  of  the  pectoralis  major,  the  latissimus  dorsi,  and  the  third  head  of 
the  triceps. 

Tumors  of  a  more  serious  variety,  especially  the  sarcomata,  attack  the  hu- 
merus. The  central  sarcomata  are  found  in  the  upper  extremity  chiefly  at  the 
upper  end  of  the  humerus  and  at  the  lower  ends  of  the  radius  and  ulna.  It  may 
be  interesting  to  note  that  those  are  the  extremities  towards  which  the  respective 
nutrient  arteries  are  not  directed,  and  therefore,  in  accordance  with  the  general 
rule,  the  extremities  at  which  bony  union  of  the  epiphyses  and  diaphyses  takes 
.  place  latest. 

The  close  attachment  of  the  periosteum  at  the  middle  of  the  shaft  has  been  said 
to  account  for  the  fact  that  non-union  after  fracture  occurs  in  this  region  more  fre- 
quently than  in  the  shaft  of  any  other  long  bone  of  the  skeleton.     This  has  also  been 
attributed  to  interference  with  the  nutrient  artery  (which  enters  the  bone  near  its 
1  Owen,  Lejars,  and  others,  quoted  by  Poland. 


PRACTICAL    CONSIDERATIONS:    THE    HUMERUS. 


273 


Fig.  288. 


middle)  and  to  imperfect  immobilization  of  the  humerus,  the  elbow  being  fixed  by- 
splints,  any  motion  of  the  hand  or  forearm  under  those  circumstances  being  trans- 
formed into  motion  of  the  upper  end  of  the  lower  fragment.  These  may  be  factors, 
but  the  chief  reason  for  non-union  is  the  entanglement  of  muscular  and  tendinous 
fibres  of  the  brachialis  anticus  and  of  the  triceps  between  the  bony  fragments  (page 
59o). 

Descending  the  shaft  it  is  not  difficult  to  see  why  a  fracture  just  above  the  con- 
dyles ("at  the  base  of  the  condyles,"  "supracondylar")  should  often  be  met  with. 
The  olecranon  fossa,  the  coronoid  fossa,  the  shallower  fossa  for  the  radius  just  above 
the  external  condyle,  all  contribute  to  weaken  the  bone  at  this  point.  Moreover,  in 
falls  upon  the  elbow  (the  common  cause  of  this  fracture)  the  tip  of  the  olecranon  is 
frequently  driven  directly  into  its  fossa  and  against  the  very  thin  lamina  at  its  base, 
starting  a  fracture  which  extends  laterally  through  the  supracondylar  and  supra- 
trochlear ridges  to  the  border  of  the  bone.  If  this  transverse 
line  of  fracture  is  associated  with  one  running  perpendicularly 
into  the  joint,  it  constitutes  the  so-called  "  T-fracture"  ("  inter- 
condylar' ' )  ;  it  is  produced  in  the  same  manner,  but  usually 
by  a  greater  degree  of  force. 

In  the  so-called  "extension"  and  "flexion"  fractures  in 
this  region  the  same  mechanism  is  probably  present,  though  it 
is  easy  to  imagine  the  same  result  (if  the  capsule  and  ligaments 
of  the  elbow-joint  remain  intact)  without  the  agency  of  the 
olecranon. 

It  should  be  noted  that  the  external  supracondylar  ridge, 
the  strongest  and  most  prominent,  springs  from  the  external 
condyle,  ascends  in  the  line  of  the  shaft,  and  terminates  in  the 
head,  so  that  it  is  well  adapted  to  receive  and  distribute  force 
applied  through  the  radius,  as  in  falls  on  the  hand,  or  in  pushing 
or  striking  strongly.  The  external  is  smaller  than  the  internal 
condyle  because  the  extensors  and  supinators  arising  from  it  are 
less  powerful  muscles  than  the  flexors  and  pronators  connected 
with  the  former.  This  makes  it  less  prominent;  but  in  spite  of 
these  protective  conditions  it  is  at  least  as  frequently  broken,  es- 
pecially from  indirect  violence,  because  of  its  direct  connection 
with  the  hand  through  the  radius  and  capitellum.  On  account 
of  the  dense  triceps  fascia  covering  it,  and  its  connection  with  the 
ligaments  of  the  elbow-joint,  the  displacement  is  slight.  The 
line  of  fracture  usually  passes  through  the  radial  fossa  and  enters 
the  joint  through  the  depression  between  the  capitellum  and 
the  trochlear  ridge. 

The  internal  condyle  is  more  often  broken  by  direct  violence, 
or  by  the  wedge-like  action  of  the  olecranon  starting  a  fracture 
which  runs  through  the  thin  bone  of  the  olecranon  and  coronoid 
fossae,  and  through  the  trochlear  depression.  The  displacement 
is  usually  upward,  is  the  result  of  the  force  causing  the  break, 
and  is  but  little  influenced  by  anatomical  factors.    The  brachialis 

anticus  may  elevate  the  fragment,  but  the  ulna  remains  attached  and  prevents  much 
displacement. 

Either  epicondyle  may  be  broken.  The  line  of  the  lower  epiphysis  runs 
obliquely  across  the  bone  from  just  above  the  external  epicondyle  to  a  point  just 
below  the  internal  epicondyle.  In  infancy  both  epicondyles  (as  well  as  the 
trochlea  and  capitellum)  enter  into  the  epiphysis  ;  but  at  the  thirteenth  year  the 
internal  epicondyle  is  quite  distinct,  and  the  trochlea,  capitellum,  and  external 
epicondyle  are  welded  into  the  lower  epiphysis  proper,  which  by  the  fourteenth 
to  the  fifteenth  year  (Dwight),  sixteenth  year  (Treves  and  Stimson),  seventeenth 
year  (Poland),  is  firmly  united  to  the  diaphysis.  After  the  thirteenth  year,  there- 
fore, separation  of  the  epiphysis  will  probably  leave  the  internal  epicondyle  attached 
to  the  diaphysis.  "The  point  of  junction  of  the  trochlear  and  capitellar  portions 
of  the  lower  epiphysis  at  the  middle  of  the  trochlear  groove  at  the  sixteenth  year 

18 


Lines  of  fractures  of 
the  humerus,  a,  through 
anatomical  neck ;  6, 
through  tuberosities ;  c, 
through  surgical  neck  ;  rf, 
through  shaft;  e,  T-frac- 
ture involving  condyles. 


274  HUMAN   ANATOMY. 

is  the  narrowest  portion  of  the  bone,  and  much  more  likely  to  be  broken  across, 
detaching  one  or  other  portion  of  bone  rather  than  the  whole  epiphysis  separating 
at  this  age"  (Poland). 

As  the  synovial  membrane  is  attached  on  the  inner  side  about  five  millimetres 
(three-sixteenths  of  an  inch)  below  the  internal  epicondyle,  fracture  of  the  latter 
does  not  necessarily  extend  into  the  joint-cavity.  On  the  outer  side  it  is  attached 
up  to  the  level  of  the  external  epicondyle,  so  that  the  joint  is  likely  to  be  involved 
in  traumatic  separation  of  that  process. 

As  the  capsule  of  the  joint  is  attached  at  a  higher  level  than  the  epiphysis  in 
front,  behind,  and  laterally,  the  displacement  in  epiphyseal  separations  is  within  the 
capsule,  and  therefore  likely  to  be  limited.  The  close  relationship  of  the  synovial 
membrane  gives  rise,  however,  to  extensive  effusion,  which  affects  both  diagnosis 
and  treatment. 

The  union  to  the  diaphysis  at  about  the  fifteenth  year  leaves  the  further  growth 
of  the  bone  dependent  upon  the  upper  epiphysis  (page  272)  ;  hence  injuries  involving 
the  epiphysis,  or  excision  of  the  elbow  in  which  the  epiphyseal  limits  are  overstepped, 
will  not  be  followed  by  arrest  of  growth  if  the  patient  is  more  than  fifteen  years  of 
age. 

Epiphysitis,  on  account  of  the  synovial  and  capsular  relations  above  described, 
is  apt  to  involve  the  elbow-joint,  and  to  result  in  considerable  stiffness. 

The  anatomical  deformity  and  diagnosis  of  epiphyseal  separation  will  be  con- 
sidered in  connection  with  the  subjects  of  supracondylar  fracture  and  luxation  of  the 
elbow  (page  590). 

About  two  inches  above  the  inner  condyle  there  is  often  found  (one  per  cent, 
of  recent  skeletons,  Turner)  a  hook-like  process  projecting  downward  and  converted 
into  a  foramen  by  a  ligamentous  band.  When  it  is  present  the  median  nerve 
usually  passes  through  it,  which  demonstrates  that  "  it  is  the  homologue  and  rudi- 
ment of  the  supracondyloid  foramen  of  the  lower  animals"  (Darwin).  The  process 
can  sometimes  be  recognized  by  the  sense  of  touch.  The  intercondylar  foramen, 
which  is  occasionally  present  in  man,  occurs,  but  not  constantly,  in  various  anthro- 
poid apes,  and,  though  it  weakens  the  bone  somewhat,  is  chiefly  interesting  because 
it  is  found  in  much  greater  frequency  in  skeletons  of  ancient  times,  and  thus  illus- 
trates Darwin's  assertion  that  "ancient  races  more  frequently  present  structures, 
which  resemble  those  of  the  lower  animals  than  do  modern." 


THE   SHOULDER-JOINT. 

The  ligaments  of  this  articulation  are  : 

Capsular ;  Glenoid 

Accessory  ligaments  : 

Coraco-Humeral  ;     Gleno-Humeral. 

This  is  a  very  simple  instance  of  the  ball-and-socket  joint,  the  only  irregularity 
being  the  position  of  the  humeral  head  somewhat  on  one  side  instead  of  at  the  top 
of  the  bone,  so  that  the  axis  of  rotation  does  not  correspond  with  the  axis  of  the 
shaft. 

The  shallow  socket  of  the  glenoid  cavity,  lined  with  articular  cartilage,  is 
deepened  by  the  glenoid  ligament1  (Figs.  290,  292),  a  fibro-cartilaginous  band 
attached  by  its  base  to  the  border  of  the  cavity  and  ending  in  a  sharp  edge.  It  is 
thus  triangular  on  section  (Fig.  291),  the  breadth  of  the  base  being  five  millimetres 
and  the  height  at  its  greatest  about  one  centimetre.  This  ligament  is  composed 
chiefly  of  fibres  running  around  the  socket.  It  is  directly  continuous  with  the  fibres 
of  the  long  head  of  the  biceps  from  the  insertion  of  the  latter  into  the  top  of  the 
socket. 

The  capsular  ligament2  (Fig.  289)  is  so  lax  that  in  the  dissected  joint  the 
head  of  the  humerus  falls  away  from  the  socket.  In  life  it  is  kept  in  place  chiefly 
by  the  tonicity  of  the  surrounding  muscles.  The  course  of  the  fibres  is  in  the  main 
longitudinal,  but  they  are  indistinct.      The  capsule  arises  above  from  the  edge  of  the 

^Labruni  gleaoidale.     "Capsula  articularis. 


THE   SHOULDER-JOINT. 


275 


glenoid  cavity  and  the  bone  just  around  it,  from  the  outer  surface  of  the  glenoid 
ligament  as  far  as  its  edge,  excepting  at  the  top,  where  it  does  not  encroach  on  the 
ligament,  and  at  the  inner  side,  where  its  origin  is  uncertain.      It  may  arise  there  as 


Trapezoid  ligament 
Clavicle 


Capsule 


Conoid  ligament 


Suprascapular  ligament 


Right  shoulder-joint  from  before. 

described,  but  very  often  it  arises  at  some  distance  from  the  border  of  the  joint  from 
the  anterior  surface  of  the  scapula.  In  exceptional  cases  this  distance  may  be  half 
an  inch,  perhaps  more.      The  inferior  attachment  of  the  capsular  ligament  is  to  the 

Fig.  290. 

Acromioclavicular  joint 


Glenoid  ligament 


Spine  of  scapula 


Right  shoulder-joint,  capsule  opened  and  h 


groove  round  the  head,  close  to  the  latter  above  and  externally,  but  a  little  way 
from  it  below  and  internally.       This  applies  to  the  attachment  as  seen  from  within 


276 


HUMAN    ANATOMY. 


the  opened  joint  ;  on  the  outside,  the  fibres  can  be  traced  for  a  considerable  distance 
from  the  joint  before  they  are  lost  in  the  periosteum.  Fibres  going  to  the  tuberosi- 
ties blend  with  the  tendons  of  insertion  of  the  muscles  of  the  scapular  group,  the 
supra-  and  infraspinati,  the  teres  minor,  and  the  subscapularis,  which  materially 
strengthen  the  capsule.      The  latter  is  thinnest  behind. 

Certain  accessory  ligaments  strengthen  the  capsule.  The  most  important  is 
the  coraco-hwtieral  (Fig.  289),  which,  arising  from  the  outer  edge  of  the  horizontal 
portion  of  the  coracoid  where  a  bursa  separates  it  from  the  capsule,  soon  fuses  with 
the  latter  and  runs,  without  very  distinct  borders,  to  both  tuberosities,  crossing  the 
bicipital  groove.  A  few  transverse  fibres  (the  transverse  humeral  ligame?it)  bridge 
in  the  bicipital  groove  below  the  capsule  proper.  Three  gleno-humeral  bands  (Fig. 
290)   are  described  on  the  inside  of  the  capsule,  of  which  the  most  important  is  the 


Tendon  of  subscapularis  and  capsule 


Fig.  291. 

Lesser  tuberosity 


Tendon  of  biceps  in  bicipital  groove 


Glenoid  ligament 


Glenoid  ligament 


Greater  tuberosity 


Subdeltoid  bursa 


Tendon  of  infraspinatus 
id  capsule 


Horizontal  frozen  section  through  the  right  shoulder-joint  from  above. 


superior.  This  band  springs  from  near  the  top  of  the  inner  border  of  the  glenoid 
cavity  and  is  inserted  into  the  lesser  tuberosity.  In  a  part  of  its  course  it  makes  a 
prominent  fold  of  the  synovial  membrane  along  the  inner  border  of  the  tendon  of 
the  long  head  of  the  biceps.  This  ligament  has  been  described  as  a  deep  part  of  the 
coraco-humeral.  The  middle  ligament  is  ill-defined.  The  inferior,  running  from 
the  lower  end  of  the  glenoid  socket  to  the  inner  side  of  the  neck  of  the  humerus, 
may  be  seen  both  from  without  and  within  the  capsule.  It  is  made  tense  when  the 
arm  is  abducted,  and  materially  strengthens  the  joint.  The  capsule  usually  presents 
an  opening  on  the  inner  side  in  the  upper  part,  by  which  the  bursa  below  the  tendon 
of  the  subscapularis  communicates  with  the  joint.      The  cases  in  which  the  capsule 


THE    SHOULDER-JOINT. 


277 


arises  internally  at  quite  a  distance  from  the  glenoid  cavity  are  probably  due  to  a 
very  free  opening  into  a  large  bursa.  The  tendon  of  the  long  head  of  the  biceps 
lies  within  the  capsule  from  its  origin  at  the  top  of  the  glenoid  till  it  leaves  the  cap- 
sule in  the  bicipital  groove.  The  tendon  does  not  lie  free  within  the  joint,  but  is 
covered  by  a  reflection  of  the  synovial  membrane  as  it  lies  curved  over  the  head  of 
the  humerus.  On  the  young  fcetus  it  is  attached  to  the  inside  of  the  capsule  by  a 
synovial  fold.  The  synovial  membrane  of  this  joint  is  remarkably  free  from  synovial 
fringes. 

The  bursae  about  the  joint  are  numerous.  The  largest  is  the  subacromial  or 
subdeltoid  bursa  (Figs.  291,  292),  situated  between  the  top  of  the  capsule,  the 
coraco-acromial  ligament,  and  the  acromion,  and  extending  downward  under  the 
deltoid.      The  subcoracoid  bursa  separates  that  process  and  the  beginning  of   the 

Fig.  292. 


Subdeltoid  bur: 


Deltoid  muscle 


Frontal  frozen  section  through  the  right  shoulder-joint. 


coraco-humeral  ligament  from  the  capsule.  Other  bursae  are  often  found  between 
the  capsule  and  the  muscles  inserted  into  the  tuberosities  ;  that  under  the  subscapu- 
lars is  constant.  Of  the  others,  the  one  most  frequently  found  is  under  the  infra- 
spinatus ;  it  also  may  open  into  the  joint. 

Movements. — When  the  arm  is  hanging  close  to  the  side  adduction  is  almost 
wanting,  since,  apart  from  the  interference  of  the  body,  the  humerus  is  arrested 
at  once  by  the  lower  border  of  the  glenoid  cavity.  Backward  movement  is  not 
free,  for  the  arm  soon  impinges  on  the  overhanging  acromion.  Abductio?!  has  a 
range  of  some  900  before  the  tenseness  of  the  lower  part  of  the  capsule  stops   it. 


278  HUMAN   ANATOMY. 

(Unless  the  arm  is  raised  somewhat  forward,  it  is  stopped  still  sooner  by  the 
acromion. )  Forward  movement  is  about  equal  to  abduction,  and  is  checked 
in  the  same  way.  When  the  arm  is  at  a  right  angle  with  the  body,  the  range  of 
motion  in  a  horizontal  plane  is  about  90°.  The  degree  of  rotatioti  in  the  shoulder 
is  very  variable.  It  is  greatest  when  the  arm  is  partially  abducted,  when  in  a  dis- 
sected joint  it  may  approximate  1350.  When  raised  to  a  right  angle  it  is  about 
900,  and  in  the  hanging  arm,  if  not  closely  adducted,  nearly  the  same.  Circum- 
duction is  free. 

Probably  none  of  the  important  joints  is  so  dependent  on  others  as  that  of  the 
shoulder.  The  scapula  takes  part  in  practically  all  the  movements,  not  waiting  till 
the  range  of  movement  at  the  shoulder  is  exhausted,  but  sharing  in  it  from  the  start. 
The  acromion  and  coraco-acromial  ligament  make  an  extra  socket  under  certain  cir- 
cumstances, as  when  the  body  is  supported  by  the  arms,  the  subacromial  bursa  act- 
ing as  a  synovial  membrane.  The  long  head  of  the  biceps  is  a  great  assistance  to 
the  stability  of  the  joint,  the  muscle  pulling  the  bones  firmly  together  and  making 
them  rigid  under  circumstances  of  strain.  It  has  the  further  advantage  over  a  liga- 
ment that  its  tension  can  vary  without  change  of  position. 

PRACTICAL    CONSIDERATIONS. 

The  extremely  wide  range  of  motion  of  the  humerus  upon  the  scapula  in  the 
human  species  is  associated,  for  mechanical  reasons,  with  many  anatomical  conditions 
of  interest  to  the  surgeon.  The  most  important  of  these  conditions  in  relation  to 
displacement  are:  (1)  The  shallowness  of  the  glenoid  cavity.  (2)  The  relatively 
large  size  of  the  humeral  head,  only  one-third  of  which  is  in  contact  with  the  glenoid 
surface  when  the  arm  is  by  the  side  of  the  body.  (3)  The  thinness  and  the  great 
laxity  of  the  capsule,  which,  if  fully  distended,  would  accommodate  a  bulk  twice  as 
large  as  the  head  of  the  humerus.  This  laxity  (to  permit  of  free  elevation  of  the 
arm)  is  greater  at  the  inferior  portion  of  the  joint.  The  primary  office  of  the  cap- 
sular ligament  in  this  joint  is  not  to  maintain  apposition,  but  to  limit  movement. 
(4)  The  maintenance  of  the  contact  between  the  articular  surfaces  by  muscular 
action,  aided  by  atmospheric  pressure,  and  not  by  the  ligamentous  or  capsular  at- 
tachments. (5)  The  length  of  the  humerus,  affording  a  very  long  leverage  ;  and 
the  exposed  position  of  the  shoulder. 

All  these  circumstances  favor  dislocation,  and  render  this  joint  more  frequently 
the  subject  of  that  accident  than  any  other  joint  in  the  body.  The  usual  position  in 
which  luxation  occurs  is  that  of  abduction  and  advancement  of  the  arm,  as  in  falls 
on  the  hand. 

It  is  to  be  noted  that  this  attitude  brings  the  most  prominent  part  of  the  lower 
edge  of  the  head  of  the  bone  against  the  thinnest  and  weakest  part  of  the  capsule. 
Moreover,  the  greatest  diameter  of  the  head  of  the  humerus  is  involved,  adding  to 
the  pressure  against  the  capsule  (Fig.  293).  As  such  accidents  happen  suddenly, 
the  muscles  are  usually  taken  off  their  guard,  and  hence  that  source  of  protection  to 
the  joint  is  lacking. 

As  opposed  to  these  factors,  and  as  tending  to  prevent  displacement,  should  be 
mentioned  :  (1)  The  exceptional  relation  of  the  biceps  tendon  to  the  joint,  strength- 
ening the  capsule  at  its  upper  portion,  preventing  the  humerus  from  being  too 
strongly  pressed  against  the  acromion  by  the  powerful  deltoid  and  the  other 
elevators  of  the  arm  ;  steadying  the  head  of  the  bone  through  its  connection  in  the 
bicipital  groove,  in  which  way  "  it  serves  the  purpose  of  a  ligament,  with  the  advan- 
tage of  being  available  in  all  positions  of  the  joint,  and  without  restricting  the  range 
of  movement  in  any  direction"  (Humphry).  (2)  The  arrangement  of  the  glenoid 
cup,  the  inner  and  lower  edges  of  which  are  more  prominent  than  the  outer  and 
upper,  resisting  somewhat  the  tendency  of  the  powerful  axillary  muscles,  and  of 
blows  on  the  shoulder,  to  displace  the  humerus  inward,  and  of  falls  with  the  arm  in 
abduction,  to  displace  it  downward.  (3)  The  glenoid  ligament  deepening  the 
articular  cavity,  and  aided  in  this  by  the  insertions  of  the  long  head  of  the  biceps 
above  and  the  scapular  head  of  the  triceps  below.  (4)  The  resistance  offered  by 
the  strong  coraco-acromial  ligament  to  any  upward  displacement.      If  it  were  not  for 


PRACTICAL    CONSIDERATIONS  :    THE    SHOULDER-JOINT.      279 

these  provisions,  luxations  of  the  shoulder  would  be  even  more  frequent  than 
they  are. 

The  head  of  the  bone  may  leave  the  joint-cavity  at  other  points  than  the  in- 
ferior. If  the  force  is  so  applied  as  to  drive  the  head  of  the  bone  against  the  cap- 
sule at  the  anterior  portion,  a  direct  subcoracoid  luxation  may  result  ;  if  against  the 
posterior  portion,  a  subspinous.  The  latter  is  very  rare,  and  the  former  is  also  rare 
as  a  primary  luxation. 

The  further  mechanism  of  luxations,  their  deformities  and  anatomical  diagnosis, 
will  be  considered  after  the  muscles,  which  are  such  important  factors  in  producing 
and  modifying  them,  have  been  described  (page  582). 

Disease  of  the  shoulder-joint  may  be  of  any  variety.  In  spite  of  the  frequent 
strains  to  which  the  joint  is  subjected  and  its  wide  range  of  movement,  the  diseases 
produced  by  traumatism  are  not  exceptionally  frequent.  This  is  probably  because 
of  (1)  its  ample  covering  of  muscles  protecting  it  from  the  effects  of  cold  and  damp. 
(2)  The  mobility  of  the  scapular  segment  of  the  shoulder-girdle  lessening  greatly 
the  effect  of  traumatisms.  (3)  The  laxity  of  its  capsular  and  synovial  elements, 
which,  though  it  favors  luxation,  permits  a  moderate  effusion  to  occur  without  harm- 
ful tension.  (4)  The  influence  of  the  weight  of  the  upper  extremity  in  the  usual 
position  of  the  body  in  resisting  by  gravity  the  destructive  pressure  of  joint  surfaces 
against  each  other,  caused  by  muscular  spasm  after  injury  or  during  disease.     (5)  The 


Spine  of  scapula 


Fig.  293. 

Supraspinatus 

Reflection  of  capsule 


Infraspinatus        Head  of  scapula        Teres  minor 

Section  through  right  shoulder-joint  with  arm  in  abduction. 

ease  with  which  the  joint  may  be  immobilized  without  irksome  confinement  of  the 
patient. 

These  circumstances,  especially  the  latter,  account  also  for  the  facts  that  tuber- 
culous disease  of  the  joint  and  epiphysitis  involving  the  joint  are  not  so  common  as 
in  other  joints,  and  that  the  results  are  exceptionally  good,  operative  interference 
being  required  with  comparative  rarity. 

Synovial  distention  causes  a  uniform  rounded  swelling  of  the  shoulder,  but  it 
can  best  be  recognized  by  the  touch  in  the  bicipital  groove,  where  one  synovial 
diverticulum  runs,  and  in  the  axilla,  where  part  of  the  capsule  is  exposed  beyond 
the  margin  of  the  subscapular  muscle.  The  diverticula  beneath  the  tendons  of  that 
muscle  and  (more  rarely)  of  the  infraspinatus  are  usually  involved,  pain  when  the 
arm  is  rotated  being  a  resultant  symptom. 

The  subdeltoid  bursa  does  not  usually  communicate  with  the  joint.  It  may 
be  the  subject  of  independent  disease.  When  it  is  inflamed  the  position  of  ease 
will  be  one  which  relaxes  the  deltoid  (abduction  of  the  arm),  and  rotation  or 
pressure  upward  will  be  painless.  In  disease  of  the  subacromial  bursa,  abduc- 
tion and   upward   pressure  are  painful   because   the   sac   is   then    pinched   between 


28o  HUMAN    ANATOMY. 

the  head  of  the  bone  and  the  under  surface  of  the  acromion  and  coraco-acromial 
ligament. 

When  suppuration  occurs,  pus  may  find  its  way  out  from  the  joint,  (i)  By 
following  the  bicipital  tendon  and  opening  on  the  arm  below  the  anterior  border  of 
the  axilla.  (2)  By  following  the  subscapular  tendon,  getting  between  that  muscle 
and  the  body  of  the  scapula,  and  opening  beneath  and  behind  the  axilla.  (3)  By 
penetrating  the  capsule  beneath  the  deltoid,  when  the  dense  deltoid  and  infraspinous 
fascia  prevent  it  from  going  backward  and  direct  it  to  the  anterior  aspect  of  the 
arm.  Treves  mentions  a  case  in  which  it  followed  the  course  of  the  musculo-spiral 
nerve  and  appeared  on  the  outer  side  of  the  elbow. 

Landmarks. — The  edge  of  the  acromion  and  the  tip  of  the  coracoid  can 
readily  be  felt,  though  the  coraco-acromial  ligament  completing  the  important  arch 
above  the  joint  is  beneath  the  deltoid,  and  therefore  cannot  be  so  distinctly  pal- 
pated, but  can  usually  be  recognized  by  touch.  An  incision  through  the  centre 
of  this  ligament  would  open  the  shoulder-joint  where  the  bicipital  tendon  enters 
its  groove.  The  head  of  the  bone,  when  pressed  upward  against  this  arch,  com- 
municates motion  to  the  outer  fragment  in  cases  of  fractured  clavicle,  and  this  is 
often  the  easiest  way  in  that  lesion  of  eliciting  crepitus  and  preternatural  mobility. 
In  cases  of  paresis  or  paralysis  of  the  deltoid,  the  resultant  atrophy  may  leave  the 
whole  arch  palpable,  or  even  visible,  in  some  instances  the  bone  dropping  from  one 
to  several  inches. 

The  lower  margin  of  the  glenoid  cup  and  the  head  of  the  humerus  may  be  felt 
in  the  axilla  when  the  arm  is  abducted  (Fig.  293). 

The  greater  tuberosity  may  be  felt  through  the  deltoid,  directly  beneath  the 
acromion,  the  arm  hanging  at  the  side.  It  faces  in  the  direction  of  the  external 
condyle.  Together  with  the  lesser  tuberosity  it  produces  the  normal  roundness  of 
the  deltoid. 

The  head  of  the  bone  cannot  be  felt  externally.  It  faces  in  the  general  direction 
of  the  internal  condyle.  Two-thirds  of  it,  when  the  arm  is  by  the  side,  is  in  front 
of  a  vertical  line  drawn  from  the  anterior  border  of  the  acromion  process.  It  is  also 
altogether  external  to  the  coracoid  process. 

The  lesser  tuberosity  faces  forward.  Between  it  and  the  greater  tuberosity, 
when  the  arm  is  hanging  loosely  and  is  supine,  the  lower  part  of  the  bicipital  groove 
may  be  felt  in  thin  subjects.  This  also  faces  directly  forward,  and  is  on  a  line  drawn 
through  the  middle  of  the  biceps  and  its  lower  tendon. 

The  upper  part  of  the  humeral  shaft  cannot  be  felt.  The  circumflex  nerve  winds 
around  it  a  little  above  the  middle  of  the  deltoid.  The  deltoid  tubercle  may  be 
recognized  at  the  middle  of  the  arm.  From  there  downward  the  bone  is  more 
superficial  externally,  and  the  outer  supracondylar  ridge  may  be  traced  down  to  the 
condyle.  The  less  prominent  internal  ridge  can  be  felt  only  for  a  short  distance 
above  the  elbow. 

The  middle  of  the  humerus,  indicated  by  the  insertion  of  the  deltoid  on  the 
outer  side,  is  also  on  a  level  with  that  of  the  coraco-brachialis  on  the  inner  and  with 
the  upper  portion  of  the  brachialis  anticus  on  the  anterior  surface,  with  the  origin 
of  the  nutrient  and  inferior  profunda  arteries,  with  the  exit  through  the  deep  fascia 
of  the  nerve  of  Wrisberg  and  the  entrance  of  the  basilic  vein,  with  the  passage  of 
the  median  nerve  across  the  brachial  artery,  and  with  the  departure  of  the  ulnar 
nerve  from  its  proximity  to  the  vessel.  Posteriorly,  the  middle  of  the  bone  is  covered 
by  the  triceps. 

Just  below  the  middle  the  musculo-spiral  nerve  and  the  superior  profunda  wind 
around  in  the  groove  below  the  deltoid  insertion,  and  the  inner  head  of  the  triceps 
arises  from  the  bone. 

At  the  junction  of  the  middle  and  lower  thirds  the  brachial  artery  from  the 
inner  side  and  the  musculo-spiral  nerve  from  the  outer  side  tend  to  approach  the 
front  of  the  bone. 

The  landmarks  at  the  lower  extremity  will  be  considered  in  relation  to  the 
elbow-joint  and  the  bones  of  the  forearm. 

The  surface  anatomy  and  the  relations  of  the  soft  parts  to  the  humerus  will  be 
recurred  to  after  those  structures  have  been  described. 


THE    ULNA.  281 

THE   FOREARM. 

The  skeleton  of  the  forearm  consists  of  two  bones, — an  inner,  the  ulna,-a.nd  an 
outer,  the  radius.  The  former  is  large  above  and  small  below  ;  the  latter,  the  con- 
verse. The  ulna  plays  around  the  trochlea  in  flexion  and  extension,  carrying  the 
radius  with  it.  The  radius  plays  on  the  ulna  in  pronation  and  supination,  carrying 
with  it  the  hand.  These  bones  are  connected  by  an  interosseous  membrane,  which 
gives  origin  to  muscles,  adds  to  the  security  of  the  framework,  and  yet  implies  a 
great  saving  in  weight. 

•      THE    ULNA. 

The  ulna  consists  of  a  shaft  and  two  extremities. 

The  upper  extremity  is  devoted  to  the  joint  with  the  humerus,  and  laterally 
to  that  with  the  head  of  the  radius.  The  former  articular  surface  is  the  greater  sig- 
moid cavity  hollowed  out  of  the  continuous  surfaces  of  the  olecranon  process  behind 
and  above  and  the  coronoid  process  in  front.  The  olecranon,1  a  cubical  piece  of 
bone  projecting  upward  in  continuation  with  the  shaft,  presents  this  articular  surface 
in  front  (to  be  described  later),  and  a  superior,  a  posterior,  and  two  lateral  surfaces. 
The  superior  surface  is  pointed  in  front,  with  the  ooint  or  beak  external  to  the 
middle.  A  slight  groove  just  back  of  the  edge  serves  for  the  attachment  of  the 
capsular  ligament.  Behind  this  are  two  parts  of  different  texture,  the  posterior  of 
which  is  for  the  insertion  of  the  triceps.  The  posterior  surface  is  triangular,  bounded 
above  by  the  irregular  edge  of  the  top,  and  laterally  by  two  lines  which  meet  below 
to  make  the  posterior  border  of  the  shaft.  It  is  subcutaneous,  and  is  covered  by  a 
bursa  (Fig.  294).  The  outer  surface  is  bounded  in  front  by  the  sharp  edge  of  the 
sigmoid  cavity,  along  which  is  the  groove  for  the  capsule.  Behind  this  is  a  hollow 
for  the  anconeus.  The  inner  surface  has  in  front  the  inner  border  of  the  sigmoid, 
less  sharp  than  the  outer,  the  capsular  groove,  and  farther  back  a  rough  elevation. 
The  coronoid  process2  rises  from  the  anterior  surface  of  the  front  of  the  shaft.  It 
has  an  upper,  articular  surface,  an  anterior,  and  two  lateral  ones.  The  front  surface 
rises  to  a  point  nearer  the  outer  side.  The  capsular  groove  runs  along  the  border  ; 
and  below  this,  bounded  by  two  lines  meeting  below,  is  a  rough  region  for  the 
brachialis  anticus.  Within  the  angle  formed  by  the  meeting  of  these  two  lines  is  a 
rough  rounded  space,  the  tuberosity  of  the  ulna,  from  the  edge  of  which  arises  the 
oblique  ligament.  The  brachialis  anticus  is  inserted  into  the  lower  part  of  this  sur- 
face and  the  tuberosity.  The  inner  surface  is  bounded  above  by  the  sharp  project- 
ing border  of  the  sigmoid  cavity,  at  the  edge  of  which  is  a  rough  prominence  from 
which  certain  fibres  of  the  flexor  sublimis  digitorum  take  origin.  The  outer  surface 
presents  the  lesser  sigmoid  cavity. 

The  greater  sigmoid  cavity 3  occupies  the  anterior  surface  of  the  olecranon  and 
the  superior  one  of  the  coronoid  process.  There  is  a  constriction  in  the  middle  of 
both  borders,  but  deeper  in  the  outer,  where  the  two  processes  meet,  and  the  articu- 
lar surface  on  the  dry  bone  seems  often  to  be  interrupted  in  a  line  between  them. 
The  sigmoid  cavity,  concave  from  above  downward,  is  broader  in  the  upper  half  than 
the  lower.  It  is  surrounded,  except  where  it  is  joined  by  the  lesser  sigmoid  cavity, 
by  an  ill-marked  groove  for  the  capsular  ligament.  The  articular  surface  is  subdivided 
by  a  rounded  ridge,  running  from  the  point  of  the  olecranon  to  that  of  the  coronoid, 
into  a  larger  inner  and  a  smaller  outer  portion.  The  course  of  this  ridge  is  generally 
somewhat  inward  as  well  as  downward.  This  and  the  cross-line  divide  the  articular 
surface  into  four  spaces.  Of  the  upper,  the  inner  is  concave  and  the  outer  convex 
from  side  to  side.  Of  the  lower,  the  inner  is  concave  in  the  same  direction  and  the 
curve  of  the  outer  is  uncertain  ;  probably,  as  a  rule,  slightly  concave,  it  may  be 
plane  or  a  little  convex. 

The  lesser  sigmoid  cavity,4  for  the  head  of  the  radius,  is  a  concavity  on  the 
outer  side  of  the  coronoid  process,  separated  from  the  greater  by  a  ridge,  which 
does  not  interrupt  the  cartilage  coating  both.  It  generally  is  an  oblong  quadrilateral 
area  forming  about  one-sixth  of  the  circumference  of  a  cylinder,  with  parallel  borders  ; 

-  Processus  coronoideus.     ^Incisure!  semilunaris.     4  Incisura  radialis. 


282 


HUMAN    ANATOMY 


Fig.  294. 


Fig.  295. 


Flex,  subli 
digit  or 


Aponeurosis  of 
ext.  carpi  ulnar \ 
flex,  profundus 
dio'itorum  and 
flex,  carpi  ulna 


Posterior  border 


Upper  end  of  right  ulna,  posterior  aspect. 


Brackialis  anticus  - 
Supinator  brevis  - 


■^'][_Ftex.  sublim.  dig. 
(coronoid  head) 
~%^l'  /     Pronat.  radii  t ere: 
( lesser  head) 
Flex.  long,  pollici: 
(accessory  head) 


Tip  of  olecranon 


Tuberosity 


WMsx  Slu*a/\.  <W4iO 


Anterior  border 


Nutrient  canal 
Interosseous  border — , 


-  Pronator  quadratus 


Styloid  process 
Right  ulna,  inner  aspect.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


THE   ULNA. 
Fig.  296. 

Olecranon  tip  • 

Greater  sigmoid  cavity    (/uUaAA  tx^o^a-^y  ■HWr-  tkj 


283 


Coronoid 
process 


[luAioJL  WTUJ| 


Supinator  ridge 


,'jljfflt Interosseous  border 

ih-k\'\  —Vertical  ridge 


!  i 


Ext.  ossis  met.  pother's 


Ext.  carpi  ulnaris— 


Ext.  long,  pollicis 


Ext.  indicts 


Groove  for  ext 
carp,  ulnar. 

Styloid  process 


Right  ulna,  outer  aspect.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


284 


HUMAN    ANATOMY. 


Fig.  297. 


V' ■••.'.'  ■  &? 


but  sometimes  the  front  border  is  short  and  the  inferior  runs  obliquely  backward, 
making  it  almost  triangular. 

The  shaft,1  which  presents  three  borders  and  three  surfaces,  steadily  diminishes 
from  above  downward.  In  the  upper  part  the  bone  curves  slightly  backward  and 
outward  {i.e.,  towards  the  radius),  then  inward  through  the  greater  part  of  its 
extent,  till  at  the  lower  quarter  it  again  bends  outward  and,  at  the  same  time,  for- 
ward. The  posterior  border2  is  formed  by  the  union  of  the  two  lines  bounding  the 
subcutaneous  surface  at  the  back  of  the  olecranon.  Following 
the  curves  just  described,  it  runs  to  the  back  of  the  styloid 
process,  being  very  distinct  in  the  first  two-thirds,  where  it  gives 
origin  to  the  aponeurosis  of  the  flexor  carpi  ulnaris.  The  anterior 
border?  springing  from  the  junction  of  the  front  and  inner  sides 
of  the  coronoid,  runs  down  to  end  just  above  the  front  of  the 
styloid  process.  Its  last  quarter,  which  is  rough  to  give  origin  to 
the  pronator  quadratus,  has  a  backward  slant.  The  outer  or  in- 
terosseous border^  is  very  sharp  in  the  middle  two-fourths  of  the 
shaft,  where  it  gives  origin  to  that  membrane.  It  begins  above 
by  the  union  of  two  lines,  which,  starting  from  the  front  and 
back  of  the  lesser  sigmoid  cavity,  bound  a  triangular  depression. 
The  posterior  of  these  lines,  sharp  and  rai=ed,  is  the  supinator 
ridge.  The  depression  which  gives  origin  to  the  supinator  brevis 
receives  the  bicipital  tuberosity  of  the  radius  in  pronation.  The 
border  becomes  indistinct  below  and  is  lost  as  it  approaches  the 
head  of  the  ulna.  The  aiiterior  surface  is  usually  concave  through- 
out, though  the  upper  part  may  be  convex.  In  the  third  quarter 
a  line  often  appears  which  slants  downward  into  the  front  border, 
giving  origin  to  the  upper  fibres  of  the  pronator  quadratus. 
Below  this  line,  when  present,  there  is  a  depression  occupied  by 
that  muscle.  Above  this  arises  the  flexor  profundus  digitorum. 
The  nutrient  foramen  running  upward  is  a  little  above  the  mid- 
dle. The  inner  surface,  concave  at  the  side  of  the  upper  ex- 
tremity and  convex  below,  gives  further  origin  in  its  upper  two- 
thirds  to  the  last-named  muscle.  The  posterior  surface  has 
several  features  which  are  to  be  recognized  only  on  a  well-marked 
bone,  and  are  very  variable.  The  oblique  line  starts  from  the 
supinator  ridge,  or  from  the  hind  edge  of  the  lesser  sigmoid  cav- 
ity, and  runs  downward  to  the  posterior  border  at  the  end  of 
the  first  third.  It  gives  origin  to  a  part  of  the  supinator  brevis, 
and  helps  to  mark  off  a  three-sided  depression  running  onto 
the  olecranon  for  the  anconeus.  It  is  sometimes  the  apparent 
continuation  of  the  supinator  ridge,  as  in  Fig.  296.  The  region 
below  this  is  subdivided  by  a  vertical  ridge  of  uncertain  beginning 
and  end.  Sometimes  it  springs  from  the  interosseous  border, 
and  it  is  usually  lost  below  in  the  hind  one.  The  extensor  carpi 
ulnaris  springs  from  the  surface  internal  to  it,  which  is  some- 
times a  deep  gutter.  External  to  the  vertical  ridge  are  areas 
for  the  extensor  ossis  metacarpi  pollicis,  extensor  longus  pol- 
licis,  and  extensor  indicis  from  above  downward  in  the  order 
named. 

The  lower  extremity  of  the  ulna  consists  of  the  head  and 
the  styloid  process.  The  head  5  is  a  rounded  enlargement  pro- 
jecting forward  and  outward,  presenting  an  articular  surface  on 
the  outer  side,  which  passes  onto  the  front  and  the  back,  making 
at  least  two-thirds  of  a  circle,  around  which  the  radius  swings.  A  ridge  marks 
the  upper  border  of  this  surface,  which  overhangs  the  lower.  The  latter  is  rounded, 
so  that  the  lateral  articular  surface  continues  without  real  interruption  into  the 
inferior,  which  is.  separated  from  the  wrist-joint  by  the  triangular  fibro-cartilage. 
The  under  side  of  the  articular  surface  is  somewhat  kidney-shaped,  the  concavity 
looking  towards  the  styloid  process,  from  which  it  is  separated  by  a  groove  for  the 

1  Corpus  ulnae.     -  Margo  dorsalis.     3Margo  volaris.     4  Crista  interossea.     "Capitulum. 


PRACTICAL    CONSIDERATIONS  :    THE    ULNA. 


285 


attachment  of  the  fibro-cartilage.  The  styloid  process  is  a  short,  slender  process 
running  down  from  what  may  be  called  the  posterior  internal  angle  of  the  lower 
end.  There  is  a  distinct  groove  between  the  styloid  process  and  the  head  on  the 
posterior  aspect,  and  sometimes  a  faint  one  in  front,  transmitting  respectively  the 
tendons  of  the  extensor  and  the  flexor  carpi  ulnaris. 

Structure. — There  is  much  solid  bone  in  the  shaft,  and  altogether  the  ulna  is 
a  strong-walled  bone.  Many  plates  near  together  from  the  anterior  surface  pass 
upward  under  the  coronoid  process  to  the  middle  of  the  greater  sigmoid  notch. 
The  best-marked  system  of  plates  in  the  coronoid  is  in  the  main  parallel  to  these. 
The  greater  sigmoid  notch  is  bounded  by  compact  substance.  Sagittal  sections 
show  plates  radiating  from  it,  some  of  which  form  arches  near  the  top  of  the 
olecranon  with  others  from  the  posterior  surface.  The  head  is  composed  of  spongy 
tissue  within  thin  walls. 

Development. — The  centre  for  the  shaft  appears  in  the  eighth  week,  from 
which  practically  all  the  bone  except  the  lower  end  is  developed.      At  about  five, 

Fig.  298. 


Ossification  of  ulna.    A,  at  birth  ;  B,  at  five  years  ;  C,  at  ten  years  ;  D,  at  about  sixteen  years,    c,  centre  for 
shaft ;  d,  c,  cartilaginous  epiphyses  ;  d,  centre  for  lower  epiphysis  ;  e ,  for  upper  epiphysis. 

one  appears  for  the  head  and  styloid  process  ;  and  at  about  ten,  one  for  the  top  of 
the  olecranon.    This  fuses  at  about  sixteen  ;  the  lower  end  joins  the  shaft  at  eighteen. 


PRACTICAL   CONSIDERATIONS. 

The  ulna  may  be  absent,  or  may  be  more  or  less  defective  in  size  or  shape. 
Such  deformities  are  not  common.  Fracture  of  the  olecranon  at  its  junction  with 
the  shaft,  where  it  is  narrowed,  is  frequent.  The  degree  of  displacement  is  largely 
determined,  as  in  the  parallel  case  of  the  patella,  by  the  amount  of  laceration  of  the 
enveloping  fibrous  structure  (Fig.  585).  If  this  is  great,  the  triceps  strongly  elevates 
the  fractured  process.  Occasionally  the  mere  tip  of  the  olecranon,  or  even  a  thin 
portion  of  the  superficies  only,  may  be  separated  either  by  muscular  action  or  by 
direct  violence. 

The  epiphyseal  line  is  above  the  constriction  that  marks  the  union  of  the  olec- 
ranon with  the  shaft.  The  epiphysis  is  small  and  includes  the  upper  part  of  the 
olecranon  with  the  insertion  of  the  triceps,  a  part  only  of  the  attachment  of  the  pos- 
terior ligament,  and  a  very  small  portion  of  the  posterior  triangular  subcutaneous 
surface.  The  epiphyseal  line  runs  from  the  upper  part  of  the  sigmoid  cavity  in 
front  downward  and  backward.  The  epiphysis  enters  but  little  into  the  elbow-joint  ; 
it  is  largely  within  the  limits  of  strong  periosteal  and  tendinous  and  ligamentous 
expansions,  is  of  small  size,  and  before  the  fourteenth   or   fifteenth   year  is   on   a 


286 


HUMAN   ANATOMY. 


Fig. 


plane  anterior  to  the  epicondyles.      For  these  anatomical  reasons,  neither  muscular 
action  (triceps)  nor  falls  on  the  elbow  are  so  productive  of  separation  of  this  epiph- 
ysis in  children  as  of  fracture  of  the  olecranon  in  adults.      It  is,  in  fact,  one  of  the 
rarest  of  epiphyseal  disjunctions.      The  symptoms  are  very 
similar  to  those  of  fractured  olecranon. 

The  coronoid  process  is  rarely  broken  except  in  cases 
of  dislocation  of  the  forearm  backward  from  falls  upon  the 
hand.  The  mechanism  is  obvious.  The  force  is  applied 
through  the  medium  of  the  oblique  fibres  of  the  interosseous 
membrane.  The  line  of  fracture  is  nearer  the  tip  than  the 
base  of  the  process.  The  insertion  of  the  brachialis  anticus 
tendon  in  the  latter  region  prevents  much  displacement  of 
the  fragment,  and  the  attachment  of  the  capsule  of  the 
joint  to  its  edge  insures  a  sufficient  vascular  supply  for  pur- 
poses of  repair.  Great  proneness  to  recurrence  after  re- 
duction in  a  case  of  backward  dislocation  of  the  forearm 
should  lead  to  a  suspicion  of  the  existence  of  this  fracture. 

Fracture  of  the  shaft  of  the  ulna  alone  may  occur  at 
any  point,  and  is  usually  the  result  of  direct  violence,  as 
when  the  arm  is  raised  to  protect  the  head  from  a  blow, 
or  in  a  fall  upon  the  ulnar  side  of  the  forearm.  In  the  lat- 
ter case,  when  the  ulnar  fracture  is  in  the  upper  third,  it 
is  not  infrequently  associated  with  forward  dislocation  of 
the  head  of  the  radius  (Fig.  300). 

The  subcutaneous  position  of  the  ulna  renders  fracture 
frequently  compound.  This  accounts  for  the  greater  fre- 
quency of  non-union  in  this  bone  as  compared  with  the 
radius.  In  fracture  at  the  lower  third  the  lower  fragment 
is  drawn  towards  the  radius  by  the  pronator  quadratus. 
•?oid  Fractures  associated  with  those  of  the  radial  shaft  will 

be  considered  in  relation   to   the  effect  of  muscular   action 
upon  them  (page  604). 
The  lower  epiphysis  of  the  ulna  comprises  the  articular  surfaces  on  the  radial 
and  inferior  aspects  and  the  styloid  process.      It  is  concave  superiorly  to  fit  the 
rounded  lower  end  of  the  diaphysis.      The  level  of  the  epiphyseal  line  is  about  one- 
sixteenth  of  an  inch  above  the  level  of  that  of  the  radius.     This  epiphysis  is  strongly 


Lines  of  fract 
noid,  olecranon, 
processes  of  ulna. 


Fig.  300. 


Fracture  of  upper  third  of  ul 


held  to  the  lower  epiphysis  of  the  radius  by  the  inferior  radio-ulnar  ligaments  and 
also  by  the  triangular  fibro- cartilage  extending  from  the  root  of  the  styloid  process 
to  the  concave  margin  of  the  radius.  For  that  reason,  and  because  of  its  indirect 
relation   to  the   hand,  the   uncomplicated  separation  of  this  epiphysis   is   of    great 


THE    RADIUS. 


287 


rarity.  Even  in  cases  of  separation  of  the  lower  epiphysis  of  the  radius,  or  of 
Colles's  fracture,  the  strain  reaches  the  tip  of  the  ulnar  styloid  through  the  internal 
lateral  ligament  and  produces  fracture  of  that  process,  or  of  the  ulnar  diaphysis  at 
its  smallest  point  (about  three-quarters  of  an  inch  above  the  lower  end),  rather  than 
separation  of  the  epiphysis. 

As  the  growth  of  the  ulna  depends  almost  exclusively  upon  the  lower  epiphy- 
sis, injuries  stopping  short  of  recognizable  disjunction  have  been  followed  in  a 
number  of  cases  by  failure  of  development,  resulting  in  lateral  displacement  (adduc- 
tion) of  the  hand. 

Landmarks. — The  olecranon  can  always  easily  be  felt  at  the  back  of  the 
elbow.  It  is  somewhat  nearer  the  internal  than  the  external  condyle.  With  the 
forearm  at  right  angles  to  the  arm,  the  tip  of  the  olecranon  and  the  two  condyles 

Fig.  301. 


position  of  condyles  and  ol 


1  extension  ;  B. 


are  on  the  same  plane  as  the  back  of  the  upper  arm.  In  extreme  extension  it  is 
about  one-sixteenth  of  an  inch  or  less  above  a  straight  transverse  line  joining  the 
two  condyles  ;  in  full  flexion  it  is  anterior  to  them.  In  front  the  tip  of  the  coronoid 
process  can  be  felt  with  difficulty  in  non-muscular  subjects.  The  shaft  is  subcutaneous 
through  its  entire  length.  The  styloid  process  is  a  half-inch  nearer  the  forearm  than 
the  styloid  process  of  the  radius.  It  is  most  distinct  in  full  supination,  and  is  found 
at  the  inner  and  posterior  aspect  of  the  wrist.  In  full  pronation  the  head  of  the  ulna 
becomes  prominent  posteriorly. 

THE    RADIUS. 
The  radius  includes  a  shaft  and  two  extremities. 

The  upper  extremity  consists  of  a  head  and  neck.     The  head '  is  a  circular 
enlargement  with  a  shallow  depression  on  top  to  articulate  with  the  capitellum,  and 

^apitulum. 


z88 


HUMAN    ANATOMY. 


Fig.   302. 


Bursal  surface. 
Jicipital  surfa 


M 


-Supinator  brevis 


III 

„iiv4 — Interosseous  border 

Blip 


Biceps  tendon- 
Supinator  br 


Flex,  sublimis. 
digit  or  um 


Flex.  long,  pollicis- 


Pronator  quadratus 


Brachial  ad  nil  is 


Ext.  ossis  met  Pollicis 


Ext.  brevis  pollicis 


in 

■ill 

wMwk 

5%SjWJ^^S^%ulnar  surface  \MyV^.< 


Styloid  process 


Semilunar  surface 


scaphoid  surface 
Right  radius,  inner  aspect.     The  outline  figure  shows  the  < 


;  of  muscular  attachment. 


THE    RADIUS.  289 

a  smooth  margin  to  turn  in  the  socket  formed  by  the  lesser  sigmoid  cavity  and  the 
orbicular  ligament,  which  completes  it.  The  term  "circular"  is  not  used  with 
mathematical  precision,  for  slight  variations  from  it  are  the  rule.  The  most  common 
one  is  an  increase  of  the  antero-posterior  diameter.  The  depression  on  top  is  not 
symmetrical,  for  there  is  almost  invariably  a  greater  thickness  of  the  rim  in  front, 
extending  more  to  the  inner  than  to  the  outer  side.  The  smooth  margin  has  a 
downward  projection  internally.  The  plane  of  the  upper  surface  is  not  always  at 
right  angles  to  the  axis  of  the  neck,  but  often  looks  a  little  outward.  The  neck  is 
a  smooth  constricted  portion  some  two  centimetres  in  length  and  approximately 
cylindrical. 

The  shaft1  immediately  bends  outward  below  the  neck,  and  has  a  slight  forward 
curve  at  the  lower  end,  where  it  broadens  considerably.  The  bicipital  tuberosity 2  is 
a  large  prominence  at  the  inner  and  front  aspect  of  the  shaft,  just  below  the  neck. 
Its  posterior  border,  which  is  rough  and  projecting,  slants  forward  and  receives  the 
biceps  tendon.  In  front  of  this  the  tuberosity  is  smooth  for  a  bursa,  lying  beneath 
the  tendon,  which,  in  pronation,  is  rolled  around  it.  The  shaft  is  described  as  having 
three  surfaces  separated  by  three  borders  ;  there  is  convenience  in  retaining  the 
plan,  although  only  one  border  is  always  distinct  and  one  is  almost  imaginary. 
The  distinct  border  is  the  internal  or  interosseous?  which,  starting  from  the  bicipital 
tuberosity,  soon  becomes  sharp  for  the  interosseous  membrane,  and  runs  to  the 
lower  quarter  of  the  bone,  where  it. divides  into  two  descending  lines  to  the  front 
and  back  of  the  articular  facet  on  the  inner  side  of  the  lower  end.  The  anterior 
border  *  which  is  generally  distinct  above,  starts  from  the  front  of  the  tuberosity  and 
runs  downward  and  outward  to  about  the  middle  of  the  bone.  This  part  is  known 
as  the  oblique  line  of  the  radius,  which  gives  origin  to  a  part  of  the  flexor  sublimis 
digitorum,  and  separates  the  insertion  of  the  supinator  brevis  from  the  origin  of  the 
flexor  longus  pollicis.  The  border  is  thence  poorly  marked  till,  slanting  forward  to 
the  beginning  of  the  lower  fourth,  it  becomes  a  distinct  ridge  running  to  the  front  of 
the  styloid  process  and  receives  the  insertion  of  the  pronator  quadratus.  It  broadens 
at  the  end  into  a  triangular  tubercle  for  the  insertion  of  the  brachio-radialis.  The 
posterior  border  is  important  only  as  helping  to  define  the  posterior  and  outer  sur- 
faces ;  it  is  usually  to  be  seen  in  the  middle  third  of  the  bone,  and  has  neither  a 
definite  beginning  nor  end.  The  anterior  surface,  limited  above  by  the  oblique  line, 
is  slightly  concave,  and  gives  origin  to  the  flexor  longus  pollicis  as  far  down  as  the 
•last  quarter,  which  is  slightly  hollowed  for  the  pronator  quadratus  and  sometimes 
separated  from  the  upper  part  by  an  oblique  ridge.  The  nutrient  foramen  is  seen 
above  the  middle,  running  upward.  The  outer  surface,  which  is  convex,  presents 
about  the  middle  a  rougk?iess  for  the  insertion  of  the  pronator  radii  teres.  The 
posterior  surface  has  a  concavity  in  the  middle  third,  internal  to  the  posterior  border, 
and  is  convex  both  above  and  below. 

The  lower  extremity  bends  slightly  forward,  ending  in  front  in  a  prominent 
ridge  to  which  the  capsule  is  attached.  The  outer  side  is  prolonged  downward  as 
the  styloid  process,  ending  in  a  blunt  point.  It  usually  shows  grooves  for  the  tendons 
of  the  extensors  of  the  metacarpal  bone  and  first  phalanx  of  the  thumb,  wuich  pass 
over  it.  The  external  lateral  ligament  of  the  wrist  arises  from  it.  The  posterior 
surface  has  a  groove  at  its  edge  for  the  capsule,  and  above  this  is  furrowed  for  the 
passage  of  certain  tendons.  Next  to  the  styloid  process  is  a  broad  depression, 
sometimes  faintly  divided  into  two,  for  the  extensores  carpi  radialis  longior  et 
brevior  ;  internal  to  this  is  a  marked  ridge,  the  tubercle,  slanting  downward  and 
outward,  with  a  narrow,  deep  gutter  beyond  it  for  the  tendon  of  the  long  extensor 
of  the  thumb.  A  very  slight  border  separates  this  internally  from  a  broad,  shallow 
groove  for  the  tendons  of  the  extensor  communis  and  that  of  the  index-finger.  At 
the  extreme  limit  of  the  posterior  surface  is  sometimes  a  minute  furrow  for  a  part 
of  the  tendon  of  the  extensor  of  the  little  finger,  which  passes  over  the  radio-ulnar 
joint.  The  inner  side  of  the  lower  end  is  occupied  by  a  concave  articular  area,  the 
sigmoid  cavity 5  of  the  radius,  which  receives  the  head  of  the  ulna  and  much  resembles 
the  lesser  sigmoid  cavity  of  that  bone.  The  lower  surface  is  articular  for  the  scaph- 
oid and  semilunar  bones  of  the  wrist.  It  is  in  the  main  triangular,  the  base  being 
the  inner  side.      It  is  overhung  both  before  and  behind,  and  is  continued  onto  the 

Corpus.     2  Tuberositas  radii.      '  Crista  interossea.     4  Margo  volaris.     ''  Incisura  ulnaris. 

19 


2QO 


HUMAN    ANATOMY. 


Fig.  303. 


Supinator  brevis(       1         ,  Biceps 

1  '•?/ 


Pronator  radii  teres- 


■  Flex,  sublimit 
digitorum. 


'Flex,  lotig.  pollicis 


-Pronator  quadratus 


Bra  ch  io-radia  lis- 


-Nutrient  foramen 


Interosseous  border 


Anterior  border. MWH. 


Sigmoid 
cavity  for 


Groove  for  ext.^ 

os.  met. 
Groove  for  ext* 
brevispol. 

Semilunar  surface- 
Scaphoid  surface 
Styloid  process 
Right  radius  from  before.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


THE    RADIUS. 


291 


Fig.  304. 


Posterior  border. 


Interosseous  border - 


Bicep: 


Ext.  ossis  met.  potlicis- 


Ext.  brevis  pollicis- 


Supinator  brevis 


—Pronator  radii  tere, 


Sigmoid  cavity 


J  Ext.  oss.  met.  poll. 
■  {Ext.  brev.poll. 
-Ext.  carp.  rad.  long,  et  brev. 

Ext.  com.  ditr.  and  ^xaffi^    f~,   .   ., 

ext.  indicts  I  ^—Styloid  process 

Ext.  long-,  poll. 
Right  radius  from  behind.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


292 


HUMAN    ANATOMY. 


inner  side  of  the  styloid.  A  faint  ridge  from  before  backward,  beginning  at  a  slight 
notch,  marks  off  an  inner  square  surface  for  the  semilunar  and  an  outer  triangular 
one  for  the  scaphoid.  The  surface  looks  slightly  forward,  thus  causing  the  forward 
rising  of  the  hand  from  the  forearm. 

In  man  the  ulna  is  evidently  the  more  important  bone  at  the  elbow  and  the 
radius  at  the  wrist.  In  mammals  below  primates  they  are  often  more  or  less  fused 
and  the  upper  end  of  the  radius  relatively  larger  than  in  man.  It  often  occupies 
the  front  of  the  elbow-joint,  being  anterior  instead  of  external  to  the  upper  end  of 
the  ulna. 

Structure. — The  radius,  like  the  ulna,  is  thick-walled  through  the  greater 
part  of  the  shaft.       The  tuberosity  is  composed  internally  chiefly  of    longitudinal 


Fig.  305. 


Styloid  process: 

Ext.  oss.  met.  pott.  ) 
Ext.  brev.  pott.         J 


Ext.  carp.  rad.  long. 
Ext.  carp.  rad.  br 


Ext.  communis  dig. 
Ext.  long,  pollicis  and  ext. 
Tubercle 
"  end  of  right  radius. 


Fig.  306  A. 


:m 


;    : 


Fig.  306  B. 


Longitudinal  sect 


i% 


">v 


showing  arrangement  of  trabecula 


lower  end  of  bone. 


plates.  A  frontal  section  of  the  lower  end  of  the  radius  shows  the  walls  splitting 
up  into  longitudinal  plates,  which  run  to  the  lower  end,  connected  by  a  system  of 
lisrhter  transverse  ones. 


PRACTICAL    CONSIDERATIONS  :    THE    RADIUS. 


293 


Development. — The  centre  for  the  shaft  appears  at  the  end  of  the  second 
month,  and  forms  the  whole  bone,  except  the  lower  end  and  the  head.  The  nucleus 
for  the  former  appears  at  the  end  of  the  second  year  and  that  for  the  head  at  the 

Fig.  307. 


«3U 


Ossification  of  radius.    A,  at  birth  ;  i?,  at  two  years  ;  C,  at  five  years ;  D,  between  eighteen  and  nineteen  years. 
a,  centre  for  shaft ;  b,  for  lower  epiphysis  ;  c,  for  upper  epiphysis. 

end  of  the  fifth.  The  latter  unites  at  about  fifteen,  the  lower  at  eighteen  or  nineteen. 
A  scale-like  epiphysis  for  the  bicipital  tuberosity  is  said  to  appear  towards  eighteen 
and  to  fuse  very  promptly. 


PRACTICAL   CONSIDERATIONS. 

The  radius  may  be  absent  or  more  or  less  defective,  and  in  either  case  there  is 
apt  to  be  corresponding  absence  or  deficiency  in  the  hand  (Humphry). 

As  might  be  expected,  injuries  of  the  upper  end  in  the  adult  are  extremely 
rare.  Except  at  one  point  (just  below  the  external  condyle  posteriorly),  the  head 
is  far  from  the  surface  and  deeply  buried  beneath  the  thick  supinators  and  the  long 
and  short  radial  extensors  of  the  carpus.  Even  at  that  point,  more  prominent  bony 
processes — the  external  condyle  and  the  olecranon — receive  the  brunt  of  the  injury 
in  cases  of  falls  or  blows. 

The  upper  epiphysis  does  not  become  fully  ossified  until  the  fifteenth  year,  and 
is  united  to  the  diaphysis  at  the  beginning  of  the  sixteenth  year.  It  is,  therefore, 
among  the  last  of  the  epiphyses  of  the  long  bones  to  ossify  and  the  first  to  join  its 
diaphysis.  The  violence  which  separates  it  from  the  shaft  is  often  direct.  In  cases 
of  indirect  violence  the  force  is  applied  usually  as  a  combined  pull  and  twist  on  the 
forearm  of  a  very  young  child.  As  the  epiphysis  is  altogether  intra-articular  (the 
synovial  membrane  lining  the  whole  inner  surface  of  the  orbicular  ligament),  swelling 
is  early  and  marked.  As  there  is  direct  communication  with  the  larger  synovial 
cavities  of  the  elbow,  the  whole  joint  will  participate  in  the  effusion. 

Although  no  ligaments  or  tendons  are  attached  to  the  epiphysis,  the  orbicular 
ligament  hugs  it  closely  and  holds  it  in  place.  If  any  displacement  occurs,  the 
upper  part  of  the  diaphysis  may  go  either  forward  or  backward.  On  movements  of 
pronation  and  supination,  the  epiphysis  can  be  felt  immovable  just  below  the  external 
condyle. 

An  injury  known  as  "elbow-sprain,"  or  "pulled  elbow,"  and  described  as  a 
"subluxation  of  the  orbicular  ligament"  and  as  a  "subluxation  of  the  head  of  the 
radius,"  should  be  mentioned  here  because,  although  it  has  been  known  for  more 
than  two  hundred  years,  has  well-defined  and  constant  symptoms,   occurs  in  one 


294 


HUMAN   ANATOMY. 


per  cent,  of  all  surgical  cases  in  children  under  six  years  of  age,  and  is  believed  to 
depend  on  a  distinct  anatomical  lesion,  the  exact  nature  of  that  lesion  is  still  un- 
known. It  is  usually  caused  by  traction  on  the  forearm.  The  most  plausible  of 
many  theories  are  :  ( I )  that  it  is  due  to  the  head  of  the  radius  slipping  out  from 
beneath  the  orbicular  ligament,  which  is  pinched  between  it  and  the  capitellum  (Fig. 
311)  ;  and  (2)  that  it  is  a  partial  epiphyseal  separation.  The  differential  diagnosis  is 
said  to  depend  chiefly  on  the  facts  that  in  the  ' '  subluxation' '  the  head  of  the  radius 
will  rotate  with  the  shaft,  and  that  all  the  symptoms  disappear  rapidly  after  forced 
supination  has  removed  the  functional  disability.  There  seems  nothing  absolutely 
inconsistent  with  these  symptoms  in  the  view  that  a  slight  epiphyseal  separation  has 
occurred,  the  upper  end  of  the  diaphysis  being  displaced  forward,  but  carrying  with 
it  the  radial  head.  This  theory  is  strongly  favored  by  the  fact  that  very  few  cases 
have  occurred  in  children  over  five  years  of  age.  Ossification  of  the  radial  head 
begins  towards  the  end  of  the  fifth  year.  It  should  be  remembered  that  the  epiphy- 
sis includes  only  the  upper  part  of  the  head,  the  lower  portion  and  the  neck  being 
ossified  from  the  shaft.  The  upper  end  of  the  diaphysis  is  therefore  approximately 
of  the  same  size  and  shape  as  the  head,  and  may  easily  have  been  mistaken  for  it  in 

many  of    the  cases.      The  problem  pre- 
Fig.  308.  sented  is  so   purely   an   anatomical    one 

that,  in  spite  of  the  prevalent  differences 
of  opinion,  it  seems  proper  to  make  this 
brief  presentation  of  it. 

Fractures  of  the  head  are  uncom- 
mon. Fractures  between  the  head  and 
the  lower  end  will  be  considered  in  refer- 
ence to  the  effect  of  muscular  action  upon 
them  (page  604). 

In  the  neighborhood  of  the  tubercle 
the  thickness  of  the  bone,  the  ridges  that 
run  up  towards  the  head  and  down 
towards  the  outer  edge,  and  the  ample 
covering  of  muscles  render  fracture  com- 
paratively uncommon.  A  little  lower  the 
union  of  the  two  secondary  curves  near 
the  point  of  greatest  curvature  in  the 
primary  curve  of  the  whole  shaft  renders 
the  bone  more  vulnerable.  Still  lower 
the  effects  of  indirect  violence  through 
falls  upon  the  hand,  the  union  near  the 
lower  end  of  the  compact  tissue  of  the 
shaft  with  the  cancellous  tissue  of  the 
expanded  lower  extremity,  the  compara- 
tively superficial  position  of  the  bone, 
and  the  projection  of  the  anterior  articular  lip,  into  which  the  anterior  carpo-radial 
ligament  is  inserted,  all  very  markedly  favor  fracture. 

Accordingly,  we  find  that,  on  account  of  these  anatomical  conditions,  of  one 
hundred  fractures  of  the  radius,  approximately,  three  will  be  in  the  upper  third, 
six  in  the  middle  third,  and  ninety-one  in  the  lower  third,  the  large  majority  of 
these  latter  being  within  from  2.5  to  5  centimetres  (one  to  two  inches)  of  the  wrist- 
joint. 

Fractures  of  the  lower  end  of  the  radius  are  almost  always  produced  by  a 
cross-breaking  strain  caused  by  falls  on  the  hand,  and  exerted  through  the  strong 
anterior  common  ligament.  The  broad  attachment  of  this  ligament  to  almost  the  whole 
anterior  lip  of  the  radius  brings  the  strain  equally  on  the  bone  through  its  entire  width. 
The  fracture  is,  therefore,  usually  irregularly  transverse.  In  addition  to  the  force 
transmitted  by  means  of  the  ligament,  there  is  an  approximately  vertical  force,  due 
to  the  weight  of  the  body,  which  thrusts  the  sharp  lower  end  of  the  shaft  into  the 
lower  fragment,  made  up  chiefly  of  spongy  tissue,  with  merely  a  thin  shell  of  com- 
pact tissue  holding  it  together.      This  vertical  force  transmitted  through  the  forearm 


Lines  of  fracture  of  ] 
(Colles's  fracture). 


ick  and  of  lower  end  of  radir. 
A,  dorsal ;  B,  lateral  aspect. 


PRACTICAL    CONSIDERATIONS  :    THE    RADIUS. 


295 


and   hand  not  only  thus  impales  the  lower  fragment  on  the  upper,   but  necessarily 
carries  the  former  to  a  higher  level.      In  addition,  the  ulno-carpal  fasciculus  of  the 
common  ligament  drags  on  the  lower  end  of  the  ulna,  and  either  causes  fracture  of 
the  styloid  process,  into  the  side  and  base  of  which  it  is  attached,  or  causes  the  lower 
end  of  the  ulna  to  project  unduly  on  the  antero-internal  aspect  of  the  wrist.      The 
stripping  up  of  the  periosteum,  the  laceration  of  the  tendon  sheaths  that  are  so  closely 
applied  to  the  bone, — especially  the  flexor  tendons  by  the  jagged  edge  of  the  upper 
fragment, — and    the    consequent  effusion    are  the  chief 
remaining  anatomical  factors  in  producing  the  character- 
istic deformity  of  this  most  common  of  all  fractures.    The  „ 
lower   fragment   is   found   on   the  dorsum  of  the  wrist. 
The  lower  end  of  the  upper  fragment  is  found  anteriorly 
beneath  the  pronator  quadratus  or  under  the  flexor  ten- 
dons (Fig.  586).      The  styloid  process  of  the  radius  is  on 
a  higher  level  than  that  of  the  ulna  ;  in  dislocation  of  the 
wrist  this  is  not  the  case.     The  hand  is  carried  towards 
the  radial  side  (Fig.  309). 

In  cases  with  but  very  trifling  displacement  it  is 
still  possible  to  recognize  the  absence  of  the  projection 
of  the  anterior  articular  lip  of  the  bone  on  the  front  of 
the  wrist,  and  some  slight  elevation  of  the  dorsum. 
The  angle  between  the  axis  of  the  forearm  and  the 
ground  is  said  (Chiene)  to  determine  whether  in  such 
a  fall  the  line  of  force  passes  upward  in  front  of  the  axis 
of  the  forearm  and  the  radius  is  broken,  or  extends  up 
the  forearm  itself,  resulting  in  a  sprain  of  the  wrist  or  a 
dislocation  of  the  bones  of  the  forearm  backward  at  the 
elbow.  The  forward  sloping  of  the  carpal  surface  of  the 
radius  causes  the  posterior  edge  of  the  bone  to  receive 
the  greater  part  of  the  force  ;  hence  the  lower  fragment 
is  rotated  backward  on  a  transverse  axis,  and  hence  the 
disappearance  of  the  prominence  of  the  anterior  articular 
lip.  The  carpal  surface  of  the  radius  also  slopes  down- 
ward and  outward  ;  hence  the  radial  edge  of  the  lower 
fragment  receives  (through  the  ball  of  the  thumb)  a 
greater  part  of  the  shock  than  the  ulnar  edge,  which  is, 
moreover,  firmly  attached  by  the  triangular  ligament. 
This  favors  the  upward  displacement  of  the  radial  styloid 
and  the  radial  displacement  of  the  hand.  There  are 
almost  always  some  crushing  and  distortion  of  the  lower 
spongy  fragment,  even  when  it  is  not  materially  displaced. 

Anterior  displacement  of  this  fragment  may  occur 
when  the  force  is  applied  in  the  reverse  direction, — i.e. , 
with  the  hand  in  forced  palmar  flexion.  The  infre- 
quency  of  falls  on  the  back  of  the  hand  explains  the 
rarity  of  this,  accident,  but  the  greater  weakness  of  the 
posterior  ligament  and  the  absence  of  any  projecting 
articular  lip  to  increase  the  leverage  exerted  through 
the    ligament    also    contribute    to    make    the    accident    .^^'^d  carteTt^Lrdsufe 

Uncommon.  radial  side. 

The  later  results  of  these  fractures  are  much  influ- 
enced by  the  close  proximity  of  the  flexor  and  extensor 

tendons  to  the  region  of  injury,  as,  even  when  the  sheaths  escape  laceration  origi- 
nally, they  are  liable  to  become  adherent  during  the  process  of  repair. 

The  lower  epiphysis  of  the  radius  is  osseous  about  the  end  of  the  tenth  year 
and  is  united  to  the  shaft  in  the  nineteenth  or  twentieth  year.  The  epiphyseal  line  is 
almost  transverse  (Fig.  310),  and  extends  from  about  nineteen  millimetres  (three- 
fourths  of  an  inch)  above  the  apex  of  the  styloid  process  to  six  millimetres  (one- 
fourth  of  an  inch)  above  the  lower  edge  of  the  sigmoid  cavity.      The  epiphysis  is 


296  HUMAN    ANATOMY. 

thinnest  in  the  centre  (five  millimetres),  the  line  at  that  point  crossing  the  bone 
about  three  millimetres  below  the  tip  of  the  prominent  middle  thecal  tubercle. 

The  need  for  an  accurate  conception  of  this  epiphysis  is  emphasized  by  the 
facts:  (i)  that  it  is  more  often  separated  than  any  other  in  the  body,  with  the 
possible  exception  of  the  lower  epiphysis  of  the  femur  ;  (2)  that  its  line  has  more 
than  once  been  figured  and  described  as  a  line  of  fracture  on  the  basis  of  skia- 
graphs. 

The  cause  of  separation  is  almost  always  a  fall  on  the  pronated  hand.  The 
carpal  bones  are  carried  against  the  posterior  border  of  the  radial  epiphysis,  the  pro- 
nator quadratus  and  other  muscles  fix  the  lower  ends  of  the  diaphyses  of  the  radius 
and  ulna,  and  the  epiphysis  is  forced  backward.  The  anterior  carpal  ligament  and 
the  tendons  on  the  palmar  surface  of  the  wrist  are  put  on  the  stretch  and  aid  in  the 
displacement.  The  supinator  longus  is  directly  attached  to  the  epiphysis  and  aids  in 
maintaining  the  deformity. 

The  synovial  membrane  of  the  wrist-joint  does  not  reach  the  level  of  the  epi- 
physeal line  of  either  the  radius  or  the  ulna.  That  joint  is,  therefore,  not  frequently 
involved. 

The  thinness  of  the  centre  of  the  epiphysis  would  lead  to  the  expectation  that 
fracture  would  often  complicate  the  separation.      This   is  not  the  case,    however. 
Poland  says  that  the  epiphysis  is  more  solid  than  the  lower 
Fig.  310.  end  of  the  bone  of  the  adult  (which  has,  of  course,   become 

cancellous  in  structure),  and  that  it  thus  escapes  the  fracture, 
comminution,  and  impaction  which  are  so  frequent  in  later 
life. 

The  radius  is  often  the  subject  of  rickets,  and  of  both 
syphilitic  and  tuberculous  epiphysitis,  especially  at  its  lower 
end,  on  account  of  the  exceptional  frequency  of  falls  upon 
the  hand  and  strains  of  the  epiphyseal  joint. 

Subperiosteal  sarcomata  are  rare.  Central  sarcomata 
almost  invariably  attack  the  lower  end  of  the  bone  (page 
366). 

Landmarks. — The  head  of  the  bone  may  be  felt  at  the 
bottom  of  the  dimple  or  depression  just  below  the  external 
condyle  and  to  the  outer  side  of  the  olecranon.  It  lies  be- 
tween the  outer  border  of  the  anconeus  and  the  muscular 
swell  of  the  supinator  longus  and  radial  extensors  of  the  car- 
pus. It  is  covered  by  the  external  lateral  and  orbicular  liga- 
ments. It  can  readily  be  felt  to  move  when  the  forearm  is 
Lower  end  of  left  radius,     pronated  and  supinated.     Its  presence  in  that  position  demon- 

showing     epiphyseal    line,       r  r  f  r 

dorsal  aspect.  strates  that  dislocation  of  the  radius  or  of  both  bones  of  the 

forearm  backward — the  common  dislocation  at  the  elbow — 
has  not  occurred.  Its  free  rotation  negatives  the  existence  of  a  non-impacted 
fracture  of  the  radius. 

The  upper  edge  of  the  head  lies  immediately  below  the  elbow-joint.  In  full 
supination  the  tubercle  can  be  indistinctly  felt  a  little  below  the  lower  edge  of  the 
head.  The  upper  half  of  the  radial  shaft  cannot  be  felt,  as  it  lies  beneath  the  bellies 
of  the  extensors  and  the  supinator  brevis.  The  lower  half  is  almost  subcutaneous 
and  can  readily  be  palpated  through  or  between  the  tendons  and  muscles.  The 
expanded  lower  extremity  is  partly  subcutaneous  (at  the  base  of  the  styloid  exter- 
nally) and  is  readily  felt.  The  styloid  itself,  the  prominent  tubercle  at  the  radial 
side  of  the  groove  for  the  extensor  longus  pollicis  (middle  thecal  tubercle),  and 
the  sharp  tubercle  at  the  base  of  the  styloid  can  easily  be  recognized.  The  latter 
is  the  inferior  termination  of  the  pronator  crest  of  the  diaphysis,  marks  the  ex- 
ternal termination  of  the  epiphyseal  line,  and  is  on  a  level  with  the  lower  and  outer 
part  of  the  pronator  quadratus  muscle.  The  posterior  end  of  the  middle  thecal 
tubercle  is  three  millimetres  above  the  epiphyseal  line  on  the  posterior  aspect  of  the 
bone. 

The  styloid  process  of  the  radius  is  lower — i.  e. ,  nearer  the  hand — than  the  styloid 
process  of  the  ulna. 


RADIO-ULNAR   ARTICULATIONS. 


297 


JOINTS   AND   LIGAMENTS    BETWEEN    RADIUS  AND   ULNA. 

These  include, — 

1.  Superior  Radio-Ulnar  Articulation  : 

Orbicular  Ligament  ;  Capsular  Ligament. 

2.  Inferior  Radio-Ulnar  Articulation  : 

Triangular  Cartilage  ;         Capsular  Ligament. 

3.  Ligaments  uniting  the  Shafts  : 

Interosseous  Membrane  ;  Oblique  Ligament. 

The  superior  radio-ulnar  joint1  (Figs.  311,- 312)  is  between  the  circum- 
ference of  the  head  of  the  radius  and  the  lesser  sigmoid  cavity  of  the  ulna  extended 
into  a  circle  by  the  orbicular  ligament.      The  articular  ends  of  the  bones  are  coated 

Fig.  311. 


External  condyli 


Internal  condyle 


Tuberosity  of  radius 


Superior  radio-ulnar  articulation,  anterior  aspect.    The  capsule  of  the  elb 


with  cartilage  requiring  no  particular  description.  The  orbicular  ligament'-  (Fig. 
311)  surrounds  the  head  of  the  radius,  springing  from  the  two  ends  of  the  lesser  sig- 
moid cavity  and  from  the  lines  running  down  from  them.  This  band  embraces  the 
head  tightly,  but  is  separated  from  it  by  the  cavity  of  the  joint,  and  is  lined  with 


HUMAN   ANATOMY. 


synovial  membrane.  It  narrows  below  so  as  to  fold  under  the  projecting  head,  and 
is  attached,  chiefly  through  fibres  from  the  lower  border  of  the  lesser  sigmoid  cavity, 
to  the  inner  side  of  the  neck.  It  is  connected  above  with  the  capsular  ligament 
of  the  elbow-joint.  That  the  fibres  to  the  neck  limit  rotation  is  easily  shown  by 
dividing  all  bands  connecting  the  bones,  excepting  the  orbicular  ligament  :  for  were 
it  not  so,  the  radius  could  then  be  turned  continuously,  which  is  not  the  case.  It  is 
doubtful,  however,  whether  these  fibres  become  tense  by  any  movement  which  can 
occur  in  the  undissected  joint.  .  • 

The  inferior  radio-ulnar  joint1  is,  when  seen  from  the  front,  an  L-shaped 
cavity,  the  vertical  part  being  between  the  head  of  the  ulna  and  the  hollow  on 
the  radius,  and  the  horizontal  limb  between  the  ulna  and  the  triangular  cartilage,2 
which  is  attached  by  its  base  to  the  border  between  the  inner  and  lower  ends  of 
the  radius  in  such  a  manner  that  its  distal  surface  is  in  the  same  plane  as  the 
lower  end  of  the  radius.  The  apex  of  the  cartilage  is  attached  by  a  ligament  some 
three  millimetres  long  to  the  groove  between  the  head  and  the  styloid  process  of  the 
ulna  and  to  the  inner  surface  and  anterior  edge  of  the  latter.  Strong  bands, 
inseparable  from  the  ligaments  of  the  wrist,  run  along  its  border  to  the  front  and 
back  of   the  articular  surface  of   the  radius.      The  fibro-cartilage  is  very  flexible 

Fig.  312. 

Front  of  capsule  Median  nerve  Radial  nerve 

/ 


Coronoid  process 


Inner  side  of  greater 
sigmoid  cavity 


Horizontal  section  through  right  elbow-joint  i 


Orbicular  ligament 


of  humerus  has  been  removed. 


and  adapts  itself  to  the  surfaces  of  the  lower  end  of  the  ulna  and  of  the  first  row  of 
the  carpus.  Its  inner  end,  however,  is  not  as  broad  as  the  lower  end  of  the  ulna. 
It  is  in  some  cases  perforated.  The  membrana  sacciformis  is  the  synovial  mem- 
brane of  this  joint,  lining  the  capsule  between  the  ulna  and  the  triangular  cartilage, 
between  the  ulna  and  radius,  and  extending  a  little  above  the  level  of  the  top  of  the 
apposed  articular  surfaces  of  these  bones.  The  capsule  enveloping  it  is  delicate, 
but  strengthened  in  front  and  behind  by  ill-marked  bands  passing  between  the 
bones  ;  these  are  sometimes  described  as  distinct  anterior  and  postei'ior  ligaments. 
The  connection  between  the  lower  ends  of  the  bones  is  much  strengthened  by  the 
pronator  quadratus. 

The  ligaments  between  the  shafts  are  the  interosseous  membrane  and  the 
oblique  ligament.  The  interosseous  membrane3  (Fig.  315),  composed  of  fibres 
running  downward  and  inward,  closes,  except  above,  the  opening  between  the  bones. 
Beginning  from  one  to  two  centimetres  below  the  tubercle  of  the  radius  on  the 
anterior  surface  of  the  interosseous  ridge,  and  lower  from  the  sharp  edge,  it  connects 
the  two  ridges  as  far  as  the  lower  joint,  following  the  posterior  division  of  the  inter- 
osseous ridge  of  the  radius.  The  upper  fibres  are  nearly  transverse.  Some  long 
fibres,    particularly  on  the   posterior  surface,  run   from  ulna  to  radius.      There  are 


1  Artie,  radioulna 


:  Membrana  intcrossca  intcrbrachii. 


THE    FOREARM    AS    A    WHOLE. 


299 


several  small  openings  for  the  passage  of  vessels  and  nerves.  Pressure  transmitted 
upward  from  the  hand  through  the  radius  would  tend  to  stretch  the  greater  number 
of  the  fibres,  and  thus  distribute  the  strain  through  both  bones.      While  the  radius 


Fig.  313. 


Capsule  of  wrist-joint 


Styloid  process  of 


ferior  radio-uln 


Ligament  of  triangular  cartilage 


Triangular  cartilage  Styloid  process  of  ulna 

nd  of  right  radius  in  supination. 


can  hardly  be  enough  displaced  to  bring  this  about,  it  is  conceivable  that  the  bones 
might  bend  sufficiently  to  make  this  action  effective. 

The  oblique  ligament1  (Fig.  311),  an  inconstant  little  band,  runs  downward 
and  outward,  partly  closing  the  space  above  the  membrane,  from  the  tubercle  of  the 


Ligament  of  triangular  cartilage. 
Styloid  process  of  ul 


radio-ulnar  joint 


Styloid  process  of  radius 


Triangular  cartilage 

Lower  end  of  right  radii 


Capsule  of  wrist-joint 
pronation. 


ulna  to  the  beginning  of  the  oblique  line  of  the  radius.      It  has  been  plausibly  sug- 
gested that  it  represents  a  part  of  the  flexor  longus  pollicis  muscle. 


THE   FOREARM  AS  A  WHOLE,  AND  ITS   INTRINSIC   MOVEMENTS. 

The  two  bones  and  the  ligaments  form  an  apparatus  capable  of  being  moved  as 
a  whole  on  either  the  arm  or  the  hand,  and  of  greatly  changing  its  own  shape  by 
the  movements  of  the  radius  on  the  ulna.  As  these  latter  are  theoretically  inde- 
pendent of  the  position  of  the  forearm  with  regard  to  the  arm,' it  is  best  to  consider 
them  here. 

The  movement  of  the  radius  is  a  very  simple  one  of  rotation  on  an  axis  coincid- 
ing with  that  of  the  neck  of  the  bone,  and  then,  owing  to  the  outward  bend  of  the 
shaft,  passing  down  between  the  bones  and  finally  through  the  head  of  the  ulna. 
The  amount  of  rotation  probably  rarely  exceeds  1600.  Rotation  is  limited  chiefly  by 
the  anterior  and  posterior  radio-ulnar  ligaments,  the  former  being  very  tense  at  the 
end  of  supination  and  the  latter  at  the  end  of  pronation.  The  oblique  ligament 
limits  forced  supination.  As  above  stated,  it  is  unlikely  that  the  fibres  of  the 
orbicular  ligament  to  the  radius  become  tense  during  life.  The  fact  that  the  lower 
end  of  the  radius  swings  round  the  ulna  in  no  way  changes  the  character  of  the 
movement.  If  the  radius  were  throughout  in  continuation  of  the  axis  of  the  neck, 
and  the  ulna  enlarged  below  to  support  it,  rotation  on  the  axis  of  the  neck  would 
not  change  the  position  of  the  bone.  The  departure  of  the  greater  part  of  the  radius 
from  that  line  necessitates  the  swinging  round  of  the  lower  end,  but  does  not  affect 
the  nature  of  the  movement. 

The  changes  of  relative  position  of  the  bones  during  rotation  are  very  important. 
It  must  be  remembered  that  when  the  ulna  is  held  so  that  the  front  of  the  middle  of 
the  shaft  is  horizontal,  the  head  of  the  radius  is  in  a  plane  above  that  of  the  main 

1  Chorda  obliqua. 


300 


HUMAN   ANATOMY. 


axis  of  the  ulna.  When  the  radius  is  brought  into  semipronation  (so  that  the 
thumb  will  point  upward)  the  bones  are  most  nearly  parallel  and  at  the  greatest 
possible  distance  from  each  other,  and  the  membrane  is  approximately  tense  (Fig. 
315).  The  forearm  is  broadest  at  about  the  middle.  The  membrane  is  at  the 
bottom  of  a  moderate  hollow  seen  from  either  the  front  or  the  back.  In  extreme 
supination  the  anterior  hollow  is  effaced  and  the  posterior  deepened.  The  radius 
approaches  the  ulna,  especially  above  the  middle.  In  extreme  pronation  the  front 
hollow  is  much  deepened  and  the  hind  one  lost.  The  bones  are  much  nearer 
together  than  in  any  other  position.  The  radius  crosses  the  ulna,  and  is  above  and 
internal  to  it  at  the  wrist. 

Should  the  capsule  be  opened  from  below  without  disturbing  the  triangular  car- 
tilage in  a  specimen  from  which  the  hand  has  been  disarticulated,  in  supination  the 
front  of  the  under  side  of  the  head  of  the  ulna  will  be  exposed  ;  in  forced  pronation 

Fig.  315. 


Interosseous  membrane, 


Oblique  ligament 


Interosseous  membrane 


almost  the  whole  under  end  will  appear  (Figs.  313,  314).  As  the  radius  passes 
behind  the  head,  the  ligament  of  the  triangular  cartilage  is  relaxed  and  the  band 
at  the  back  of  the  joint  is  made  tense.  This  ligament  becomes  tense  before  com- 
plete supination  and  is  somewhat  relaxed  when  supination  is  extreme. 

The  motion  above  described  is  the  only  one  between  the  radius  and  ulna  ; 
nevertheless,  in  certain  movements  of  twisting  the  hand  and  arm  the  ulna  plays  a 
part  to  be  considered  later  (page  304). 

Surface  Anatomy  of  the  Radius  and  Ulna. — The  position  of  both  bones 
can  be  felt  in  a  body  that  is  not  very  muscular,  though  comparatively  little  of  them 
is  subcutaneous.  The  triangular  space  of  the  back  of  the  olecranon,  and  the  pos- 
terior border  of  the  ulna  starting  from  it  and  running  to  the  styloid  process,  can  all 
be  traced  with  the  finger.  When  the  arm  is  straight,  the  top  of  the  olecranon  is  a 
little  above  the  level  of  the  internal  condyle  and  behind  it  ;  when  the  arm  is  bent  at 
a  right  angle,  the  top  of  the  olecranon  is  in  the  same  vertical  plane  as  the  back  of 


THE    ELBOW-JOINT. 


30 1 


the  humerus  ;  and  when  it  is  strongly  flexed,  the  top  of  the  olecranon  corresponds 
to  the  vertical  plane  of  the  internal  condyle.  The  head  of  the  radius  and  the  furrow 
above  it  opening  into  the  joint  are  easily  felt  at  the  outside  and  behind.  In  the  lower 
third  of  the  forearm  the  bones  can  easily  be  felt.  The  ulna  here  is  posterior  and 
best  felt  at  the  back.  In  supination  the  styloid  process  is  distinct.  It  is  hidden  by 
the  soft  parts  in  pronation,  and  the  head  is  exposed.  The  forward  sweep  of  the 
lower  end  of  the  radius  is  evident.  The  inferior  expansion  can  be  felt  both  before 
and  behind  ;  the  styloid  process  is  examined  best  from  the  outer  side.  It  extends 
nearly  one  centimetre  lower  than  that  of  the  ulna.  The  inequalities  on  the  back  can 
be  felt  vaguely  ;  the  most  evident  is  the  ridge  bounding  the  groove  for  the  long 
extensor  of  the  thumb. 

THE   ELBOW   JOINT.1 

This  is  a  considerably  modified  hinge-joint,  the  axis  of  rotation  being  oblique  to 
the  long  axis  of  both  the  humerus  and  the  ulna,  and  the  course  of  the  latter  at  the 
joint  being  also  a  spiral  one.  It  is  to  be  understood  that  the  radius  follows  the  ulna, 
which  is  the  directing  bone  of  the  forearm  in  the  motions  of  the  elbow. 

The  Articular  Surfaces. — These  have  been  described  with  the  bones  ;  it 
remains  only  to  give  here  a  summary.  The  motions  between  the  forearm  and  the 
humerus  depend  essentially  on  the  trochlea  and  on  the  surfaces  of  the  greater  sigmoid 
cavity.      This  is  a  modified  hinge-joint.      As  has  been  shown,  the  transverse  axis  of 

Fig.  316. 


Brachials  antuu: 


Capsule 


Subcutaneous  bursa  -' 


Coronoid  process 


Sagittal  section  of  right  elbow-joint  through  the  trochlea. 


the  trochlea  is  not  at  right  angles  to  the  shaft,  and  it  may  be  added  that  the  same  is 
true  of  the  sigmoid  cavity  and  the  axis  of  the  ulna.  The  effect  of  this  will  be  noticed 
later.  Again,  as  already  pointed  out,  the  trochlea  is  not  only  oblique,  but  is  so 
shaped  that  the  ulna  in  turning  on  it  describes  a  spiral  line.  It  has  also  been  shown 
that  the  trochlea  is  not  equally  broad  throughout,  and  that  there  are  curious  differ- 
ences of  curve  in  the  sigmoid  cavity.  Finally,  the  lateral  ligaments  are  not  quite 
tense,  especially  when  the  joint  is  half  flexed.  It  follows  from  these  facts  that  the 
motion  is  a  very  complicated  one,  and  that  a  certain  lateral  motion  of  the  ulna  on 

1  Articulatio  cubiti. 


302 


HUMAN   ANATOMY. 


the  humerus  is  possible.      The  head  of  the  radius  plays  on  the  capitellum,  but  it 
follows  the  ulna. 

The  capsular  ligament '  surrounding  the  joint  is  very  weak  behind,  stronger 
in  front,  and  very  strong  at  the  sides,  which  last-named  parts  are  usually  called  the 
lateral  ligaments.  The  anterior  fibres  arise  from  the  humerus  above  the  coronoid 
and  radial  fossae,  and  from  the  front  of  the  bases  of  both  condyles.  Behind,  they 
arise  from  about  the  middle  of  the  olecranon  fossa,  which  is  only  partly  within  the 
capsule.  Transverse  fibres  bridge  it,  passing  between  the  highest  points  of  the 
borders  of  the  trochlea.  Below  this  the  posterior  fibres  arise  beyond  these  borders, 
so  that  the  trochlea  is  included  in  the  joint.  At  the  sides  the  fibres  forming  the 
so-called  lateral  ligaments  radiate  from  points  below  the  tips  of  the  condyles.  A 
little  of  the  external  and  a  large  part  of  the  internal  condyle  are  not  enclosed.     The 

Fig.  317. 


Band  strengthening  front  of 
capsule 


Fibres  of  orbicular  ligament 
Thin  part  of  capsule 


Bursa  for  tendon  of  biceps 


Internal  condyle  of  humerus 


Cut  tendon  of  biceps 
Oblique  ligament 


Capsule  of  right  elbow-joint  from  before. 


capsule  is  inserted  below,  posteriorly,  into  the  little  groove  described  with  the  bone 
at  the  border  of  the  olecranon.  The  radiating  fibres  from  the  external  condyle  are 
inserted  into  the  surface  of  the  orbicular  ligament,  behind,  outside,  and  in  front. 
They  are  covered  by  tendinous  fibres  of  the  muscles  from  the  condyle,  which  are 
almost  inseparable  from  them,  and  which  greatly  strengthen  the  joint.  The  fibres 
radiating  from  the  tip  of  the  inner  condyle,  or  the  internal  lateral  ligament,'1'  are  in 
two  layers.  The  posterior,  the  deeper,  is  attached  to  the  side  of  the  olecranon  ; 
the  anterior  is  a  strong  band  passing  to  the  side  of  the  coronoid  process,  which  sends 
fibres  backward,  overlapping  the  deeper  layer.  The  anterior  fibres  go  to  the 
orbicular  ligament  and  to  the  coronoid  process  near  its  edge.  The  front  part  of  the 
capsule  is  strengthened  by  delicate  oblique  fibres  from  the  front  of  the  internal  con- 
dyle, passing  downward  and  outward.  Masses  of  fat,  incorporated  in  the  capsule 
both  before  and  behind,  project  into  the  joint,  carrying  the  synovial  membrane  before 

1  Capsula  articularis.     2Lig.  collaterale  ulnare 


THE    ELBOW-JOINT. 


303 


them.  There  is  a  thick  pad  of  fat,  which,  when  large,  may  bear  well-marked 
synovial  folds  at  the  notch  on  the  inner  side  of  the  ulna  where  the  olecranon  joins 
the  coronoid. 

Movements. — These  are  of  two  orders  :  that  of  flexion  and  extension,  and 
those  which  occur  in  twisting  the  forearm.  For  practical  purposes  the  former  may 
be  reduced  to  those  of  the  ulna,  which  the  radius  is  forced  to  follow.  The  move- 
ments of  the  ulna  are  not  far  from  turning  on  an  oblique  axis,  which  cuts  the  long 
axis  of  the  humerus  at  an  angle  of  approximately  8o°  externally.  When  the  forearm 
is  fully  extended,  it  therefore  forms  externally  an  obtuse  angle  with  the  humerus. 
Were  the  long  axis  of  the  ulna  perpendicular  to  the  axis  of  the  joint,  the  forearm  in 
flexion  would  cross  the  humerus,  as  indeed  is  often  erroneously  stated  ;  in  fact, 
however,  the  long  axis  of  the  ulna  also  forms  an  angle  of  about  80°  with  the  axis  of 
the  joint,  and,  as  these  angles  equal  each  other,  in  flexion  the  forearm  is  parallel 
with  the  humerus.  A  simple  demonstration  of  this  is  gained  by  cutting  out  a  copy 
of  Fig.  320.1    On  folding  it  at  the  line  of  the  joint  {a  6)  the  two  parts  will  lie  one  on 

Fig.  318. 


Olecranon  fossa 


Internal  condyle 


Posterior  part  of  capsule 


■ External  part  of  capsule  con- 

fr\         cealing  orbicular  ligament 


the  other.  If  then  another  model  be  made  with  the  axis  of  the  lower  piece  at  right 
angles  to  the  joint,  it  will  show  that  the  lower  piece  crosses  the  upper-.  When 
extension  is  complete,  the  tip  of  the  olecranon  can  go  no  farther  into  the  fossa  on 
the  back  of  the  humerus,  and  the  front  of  the  capsule  is  tense.  In  complete  flexion 
of  the  dissected  arm,  the  tip  of  the  coronoid  is  in  contact  with  the  humerus  in  front  ; 
but  in  life  the  motion  may  be  checked  by  the  soft  parts  before  it  has  reached  its 
limit.  Morris  has  shown  that  there  is  much  variation  in  the  range  of  movement, 
depending  on  differences  in  the  upper  end  of  the  ulna.  The  lateral  ligaments  of  a 
theoretically  perfect  hinge-joint  should  always  be  tense  ;  in  the  elbow  they  are  not 
quite  tense  in  semiflexion.  Moreover,  the  imaginary  axis  does  not  remain  fixed 
throughout  the  motion. 

Motions  of  the  Forearm  on  the  Humerus  in  twisting  the  Hand. — 
The  articulation  between  the  concave  head  of  the  radius  and  the  convex  capitelkim 
of  the  humerus  is  practically  a  ball-and-socket  joint  ;  the  radius  may  glide  on  the 
humerus,  following  the  ulna,  or  it  may  rotate  on  a  fixed  axis,  as  described  above. 
It  is  easily  shown,  however,  that  the  swinging  of  the  lower  end  of  the  radius  round 

1  Potter  :  Journal  of  Anatomy  and  Physiology,  vol.  xxix.,  1S95. 


3°4 


HUMAN    ANATOMY. 


a  motionless  ulna  is  not  what  actually  occurs  in  life.  Let  the  reader  grasp  lightly 
his  right  wrist  with  his  left  thumb  and  forefinger,  so  that  they  nearly  meet  at  the 
styloid  process  of  the  radius,  and,  pressing  the  right  elbow  to  the  side  for  steadiness, 

Fig.  319. 


Interosseous  memb 


Superficial  layer  of 
inter,  lat.  ligament 


Deeper  layer  of  internal 
lateral  ligament 


Right  elbow-joint, 


Fig. 


320. 


pronate  the  right  arm.  The  lower  end  of  the  radius  will  occupy  the  place  at  the 
base  of  the  left  thumb  previously  occupied  by  the  ulna,  which  will  have  travelled 
outward  along  the  left  forefinger.  It  is  very  doubtful  whether  in  this  experiment  all 
motion  at  the  shoulder  is  eliminated  ;  nevertheless,  the  ulna  undoubtedly  changes  its 
place,  and  with  equal  certainty  it  does  not  "  rotate."  To  prove  this,  let  the  arm  of 
a  subject  be  held  in  a  vice  above  the  elbow,  which  should  be 
semiflexed,  and,  the  forearm  being  supine,  let  a  long  pin 
pointing  outward  be  fixed  into  the  outer  side  of  the  radius 
above  the  wrist,  and  another  pointing  inward  into  a  corre- 
sponding point  of  the  ulna.  On  pronating  the  hand,  the  pin 
in  the  radius  will  describe  a  large  curve  and  that  in  the  ulna 
will  make  no  evident  movement.  On  close  inspection,  aided 
by  placing  some  object  close  to  the  head  of  the  pin  in  the 
ulna,  it  will  appear  that,  though  the  bone  has  not  rotated, 
the  pin-head  has  changed  its  place  :  it  has  moved  down- 
ward and  outward.  If  the  hand  be  now  disarticulated,  and 
two  pins  bearing  brushes  dipped  in  paint  be  placed  in  the 
end  of  the  head  of  the  ulna  and  in  the  lower  surface  of  the 
radius,  pointing  downward  so  as  to  continue  the  line  of  the 
shafts  of  these  bones,  on  twisting  the  forearm,  each  of  these 
brushes  will  describe  a  curve  on  a  sheet  of  paper  held  against 
them  ;  that  in  the  radius  making  a  large  curve  upward  and 
inward,  and  the  ulnar  pin  a  small  one  downward  and  out- 
ward. The  relative  size  of  these  curves  may  be  varied 
greatly  by  the  operator.  What  has  occurred  is  this  :  besides 
the  rotation  of  the  radius,  there  has  been  a  lateral  movement  between  the  ulna  and 
humerus  combined  with  a  slight  extension.  This  movement  is  less  when  the  arm  is 
nearly  straight  than  when  flexed,  for  in  the  latter  position  the  lateral  parts  of  the 


Diagram  showing  the 
equal  angles  of  the  long 
axes  of  the  bones  with  the 
axis  of  the  joint. 


PRACTICAL    CONSIDERATIONS  :     THE    ELBOW-JOINT.  305 

capsule  are  least  tense.  It  is  probably  assisted  by  a  want  of  perfect  adaptation 
between  the  articular  surfaces.  These  experiments  on  the  dead  body  do  not  quite 
fulfil  the  conditions  of  the  living,  because  we  have  no  evidence  that  then  the  muscles 
can  produce  quite  the  same  movement  ;  moreover,  Cathcart  has  shown  that  in  anky- 
losis of  the  shoulder-joint  this  motion  is  greatly  impaired,  thus  proving  that  in  life  a 
small  amount  of  motion  at  that  joint  is  an  essential  part  of  free  twisting  of  the  hand. 
Experiments  by  Hultkrantz  on  the  living  subject  tend  to  show  that  the  slight  motion 
of  the  ulna  is  in  the  opposite  direction  to  that  described.  There  is  probably  much 
individual  variation.1 

PRACTICAL   CONSIDERATIONS. 

The  Elbow-Joint. — This  joint  is  dependent  for  its  strength  more  upon  the 
shape  of  the  bones  that  enter  into  it  than  upon  the  ligaments  or  muscles.  As  the 
elbow  ceased  to  be  useful  for  support,  but  became  of  the  utmost  importance  for 
prehension,  the  radius  became  movable  instead  of  fixed,  and  the  strength  of  the  joint 
came  to  depend  in  much  larger  proportion  upon  the  ulna. 

Force  applied  in  the  line  of  the  long  axis  of  the  limb,  as  in  hanging  by  the 
hands  (the  weight  being  transferred  from  the  wrist  and  the  radius  to  the  ulna  and 
the  elbow,  largely  by  means  of  the  triangular  and  orbicular  ligaments,  with  very 
slight  help  from  the  oblique  ligament),  is  resisted  in  the  order  of  effectiveness  (a) 
by  the  hook  of  the  olecranon  over  the  trochlea  ;  (b)  by  the  lateral  ligaments  ;  (c) 
by  the  biceps,  triceps,  and  brachialis  anticus,  aided  by  the  flexors,  extensors,  prona- 
tors, and  supinators.  The  lower  part  of  the  lesser  sigmoid  cavity  of  the  ulna  under- 
hangs  the  inner  edge  of  the  radial  head,  and  aids  in  preventing  the  radius  from  being 
drawn  away  from  the  ulna. 

Force  applied  in  the  same  line,  but  in  the  opposite  direction,  as  in  falls  upon 
the  hands  (the  thrust  being  transferred  from  the  radius  to  the  ulna  by  means  of 
the  oblique  fibres  of  the  interosseous  membrane),  is  resisted  almost  exclusively  by 
the  coronoid  process,  aided  perhaps  by  the  surface  of  contact  between  the  radial 
head  and  the  capitellum,  which  is  diminished  in  full  extension. 

As  the  dislocation  usually  occurs  with  the  forearm  hyperextended,  the  lateral 
ligaments,  particularly  the  inner  one,  are  often  stretched  and  torn  ;  the  brachialis 
anticus  is  drawn  tightly  over  the  humerus  and  is  sometimes  ruptured.  The  coronoid 
process  is  not  infrequently  broken. 

Antero-posterior  dislocations  are  the  most  frequent,  because  of  («)  the  lesser 
antero-posterior  diameter  of  the  joint  as  compared  with  the  lateral  diameter  ;  (b)  the 
varying  efficiency  of  the  hold  of  the  ulnar  processes — the  coronoid  and  olecranon — 
on  the  humerus  in  different  positions  of  the  elbow  ;  («:)  the  weakness  of  the  anterior 
and  posterior  ligaments,  and  the  absence  of  effective  muscular  support. 

Backward  dislocation  of  both  bones  is  far  more  frequent  than  forward,  be- 
cause :  (1)  The  capsular  ligament  is  weakest  posteriorly.  (2)  The  coronoid,  which 
resists  backward  displacement,  is  smaller,  less  curved,  and  received  in  a  shallower 
fossa  than  the  olecranon,  which  prevents  luxation  forward.  (3)  It  is  in  its  r^ation  of 
least  effectiveness  when  the  joint  is  in  full  extension.  (4)  Falls  upon  the  hand  with 
the  forearm  extended  greatly  outnumber  all  other  causes  of  dislocation  of  the  elbow. 
(5)  In  full  extension  the  already  slight  surface  of  contact  between  the  radius  and 
humerus  is  diminished  and  the  posterior  articular  edge  of  the  radial  head  projects 
behind  the  capitellum.  (6)  The  ulna  and  radius  are  apt  to  be  dislocated  together 
rather  than  separately  because  of  the  strong  ligaments  which  hold  them  to  each 
other — the  triangular  ligaments  below,  the  interosseous  membrane,  and  the  orbicular 
and  oblique  ligaments  above — and  because  of  the  absence  of  any  such  intimate 
connection  of  either  bone  with  the  humerus. 

It  is  this  ligamentous  connection  with  the  ulna  which  enables  the  radius,  in  spite 
of  the  shallowness  of  the  articular  cup  upon  its  head,  to  resist  the  powerful  forward 
pull  of  the  biceps. 

1  Heiberg  :  Ueber  die  Drehung  der  Hand,  1S84,  contains  an  exhaustive  bibliography. 
Heiberg  :  Journal  of  Anatomy  and  Physiology,  vol.  xix.,  1SS5.  Cathcart:  ibid.  Dwight:  ibid. 
Hultkrantz  :  Das  Ellenbogen  Gelenk  und  seine  Mechanik,  Jena,  1897,  contains  the  later 
bibliography. 


3o6  HUMAN    ANATOMY. 

Lateral  dislocations  of  the  separate  bones  are  infrequent  for  the  same  reason  ; 
of  both  bones  because  of  the  great  relative  width  of  the  joint,  its  irregular  undulating 
transverse  outline,  the  prominences  of  the  border  of  the  trochlea  and  of  the  capi- 
tellum,  the  strength  of  the  lateral  ligaments,  and  the  presence  of  the  flexor  and 
extensor  muscular  masses  arising  from  the  condyles. 

Inward  dislocation  is  the  rarest  on  account  of  the  greater  projection  of  the  inner 
border  of  the  trochlea. 

When  either  bone  is  dislocated  sepa?-ately,  it  is  most  apt  to  be  the  radius,  and 
in  the  fonvard  direction  on  account  of  the  slightness  of  its  humeral  connection,  its 
mobility,  its  direct  relation  with  the  hand  and  wrist,  and  the  effect  of  muscular  action 
(biceps)  upon  its  upper  extremity.  The  orbicular  ligament  offers  the  chief,  if  not 
the  only  resistance  to  this  forward  pull  of  the  biceps.  Therefore,  if  this  is  torn, 
recurrence  of  the  luxation  is  common,  unless  the  arm  is  kept  in  the  acutely  flexed 
position.  When  the  ulna  is  dislocated  alone,  it  is  almost  always  backward  for 
reasons  already  mentioned. 

In  the  common  backward  dislocation  of  both  bones,  the  tip  of  the  coronoid  may 
rest  upon  the  posterior  surface  of  the  trochlea,  or  may  ascend  to  the  level  of  the 
olecranon  fossa,  which,  however,  it  is  prevented  from  actually  entering  by  the  pres- 
ence of  the  soft  parts  and  by  the  tension  of  the  structures  on  the  front  of  the  joint. 
The  most  easily  recognized  symptom  of  this  displacement  is  the  change  in  the  rela- 
tion of  the  tips  of  the  condyles  and  the  olecranon,  the  latter  occupying  a  much  higher 
position  in  extension,  or  lying  much  more  posteriorly  in  flexion  (page  287,  Fig. 
301).  In  making  this  measurement  it  is  important  to  be  sure  that  the  line  uniting 
the  tips  of  the  condyles,  and  in  full  extension  in  the  normal  arm,  crossing  the  olec- 
ranon about  one-sixteenth  of  an  inch  below  its  tip,  is  a  straight  line  at  right  angles 
to  the  long  axis  of  the  humerus.  Any  upward  or  downward  curve  given  to  this  line 
destroys  its  diagnostic  significance. 

The  large  majority  of  cases  of  dislocation  of  the  elbow  occur  in  young  males, 
usually  below  the  age  of  twenty.  Kronlein  has  called  attention  to  the  fact  that  at 
this  age  fractures  of  the  clavicle  are  also  common  and  luxation  of  the  shoulder  is 
rarely  met  with,  while  after  twenty  both  clavicular  fracture  and  elbow  dislocation 
are  comparatively  rare  and  shoulder  dislocation  is  common.  He  concludes  that  in 
childhood  fracture  of  the  clavicle  is  the  equivalent  of  dislocation  of  the  shoulder  by 
direct  violence,  and  dislocation  of  the  elbow  is  the  equivalent  of  the  shoulder  dis- 
location from  indirect  violence. 

The  anatomical  explanation  may  be  that  the  disproportion  between  the  head  of 
the  humerus  and  the  glenoid  cavity  (page  278)  is  less  marked  in  childhood,  the 
articular  surfaces  are  therefore  not  so  easily  separated,  and  force  applied  to  the  point 
of  the  shoulder  is  more  apt  to  reach  and  be  expended  upon  the  clavicle. 

As  to  the  elbow,  the  shallowness  in  children  of  the  fossae  which  receive  the 
processes  and  a  corresponding  want  of  prominence  in  the  latter,  together  with  the 
ease  with  which  the  elbow-joint  in  childhood  may  be  hyperextended  (which  is  not 
the  case  in  adult  life),  are  possible  explanations  of  the  frequency  of  this  dislocation 
in  young  persons. 

Congenital  dislocations  occur.  In  some  instances  they  have  been  associated 
with  deficiency  of  the  capitellum,  and  have  then  been  accompanied  by  such  elonga- 
tion of  the  radial  neck  as  to  place  the  head  of  that  bone  on  a  level  with  the  tip  of  the 
olecranon. 

This  affords  an  illustration  of  the  general  law,  which  may  be  mentioned  here, 
that  the  rate  of  growth  of  epiphyses  is  inversely  as  the  pressure  upon  them.  Other 
examples  are  to  be  seen  in  the  overgrowth  of  the  cranial  bones  in  hydrocephalus, 
when  their  edges  are  separated  by  the  pressure  of  the  ventricular  fluid  ;  in  the  pro- 
jection of  the  vomer  and  intermaxillary  bones  beyond  the  level  of  the  alveolar  arch 
in  some  cases  of  cleft  palate  ;  in  the  bony  outgrowths  that  fill  up  the  glenoid  cavity 
or  the  acetabulum  in  unreduced  luxations  of  the  humerus  or  femur  ;  and  in  many 
other  similar  conditions. 

Disease  of  the  elbow-joint  is  most  often  tuberculous,  but  may  be  of  any  variety. 
In  spite  of  the  constant  exposure  of  the  joint  to  traumatism,  it  is  not  attacked  by 
disease  with  exceptional  frequency.      This  is  probably  partly  due  to  the  firm  inter- 


PRACTICAL   CONSIDERATIONS:   THE   ELBOW-JOINT.  307 

locking  of  its  bony  constituents,  preserving  its  ginglymoid  character  and  preventing 
the  injurious  effect  of  side  strains,  partly  to  the  similar  protective  effect  of  its  strong 
lateral  ligaments,  and  somewhat  to  the  laxity  of  its  capsule,  permitting  of  moderate 
distention  without  undue  tension.  It  is  easily  and  often  spontaneously  immobilized 
in  the  early  stages  of  disease  ;  it  then  bears  no  weight  and  is  but  little  exposed  to 
harmful  increase  of  intra-articular  pressure  from  muscular  spasm  ;  and  finally,  as  its 
fixation  does  not,  as  in  the  joints  of  the  lower  extremity,  interfere  greatly  with 
moderate  out-door  exercise,  the  general  resistant  power  is  not  so  easily  lowered. 
Swelling  first  shows  itself  posteriorly  on  either  side  of  the  olecranon  process,  and 
extends  to  the  fossa  over  the  head  of  the  radius.  In  these  directions  the  capsule  is 
thinnest  and  most  lax  and  the  synovial  cavity  is  nearest  the  skin.  As  distention 
continues  there  may  be  a  bulging  beneath  the  anconeus  to  the  outer  side  of  the 
olecranon,  or  on  the  front  of  the  elbow  beneath  the  brachialis  anticus  and  extending 
towards  the  outer  side,  as  it  is  limited  internally  by  the  thickening  of  the  capsule 
constituting  the  internal  lateral  ligament. 

Pus  is  apt  to  follow  the  same  lines  of  least  resistance,  and  discharge  upon  the 
back  of  the  arm  on  either  side  of  the  triceps,  but  especially  on  the  outer  side  on 
account  of  the  attachment  of  the  dense  intermuscular  fascia  above  the  internal  con- 
dyle ;  over  the  head  of  the  radius  beneath  the  external  condyle  ;  or  in  front  to  the 
outer  side  of  the  tendon  of  the  biceps,  a  position  determined  by  the  resistance  of  the 
bicipital  aponeurosis  on  the  inner  side. 

The  radio-ulnar  joint,  which  is  part  of  the  articulation,  is  often  involved,  affecting 
the  motions  of  pronation  and  supination. 

The  upper  radial  epiphysis  and  most  of  the  lower  humeral  epiphysis  are  within 
the  limits  of  the  capsule,  and  may  either  be  the  starting-point  of  joint  disease  or 
become  secondarily  involved. 

The  position  of  semiflexion  which  gives  the  greatest  ease,  and  is  therefore 
voluntarily  assumed,  is  that  which  affords  most  room  for  synovial  distention  and 
relaxes  the  muscles  most  immediately  in  relation  with  the  joint.  Distention  of 
the  joint  is  easily  distinguished  from  disease  of  the  neighboring  bursse.  The 
bursa  over  the  olecranon,  when  enlarged,  constitutes  a  single  rounded  superficial 
prominence  ;  that  beneath  the  triceps  tendon,  while  it  causes  swelling  on  either 
side  of  that  structure,  does  not  extend  to  or  obliterate  the  fossa  over  the  head 
of  the  radius,  nor  does  it  cause  a  '"puffiness  between  the  inner  condyle  and  the 
olecranon  process  when  the  arm  is  bent  at  a  right  angle"  (Barwell).  The  bursa? 
beneath  the  brachialis  anticus  and  between  the  tubercle  of  the  radius  and  the  biceps 
tendon,  if  enlarged,  cause  a  vague  fulness  over  those  regions,  but  none  of  the  charac- 
teristic appearances  of  synovitis.  Chronic  enlargement  of  the  latter  bursa,  in  a  case 
of  Agnew,  caused  pressure  paralysis  of  the  muscles  supplied  by  the  median  and 
posterior  interosseous  nerves. 

The  obliquity  of  the  line  of  the  elbow-joint  (page  268)  should  be  remembered 
in  the  treatment  of  fractures  involving  the  articulation.  In  obscure  injuries  about 
the  joint  the  position  of  acute  flexion,  with  the  hand  upon  the  front  of  the  chest,  is 
the  one  least  likely  to  be  followed  by  serious  ankylosis,  as  in  that  position  the  full 
functional  value  of  this  obliquity  is  more  apt  to  be  preserved  than  when  the  forearm 
is  at  a  right  angle.  The  position  is  also  the  one  in  which  it  is  easiest  to  retain  in 
place  many  fractures  in  the  region  of  the  elbow.  Especially  in  fractures  of  the  lower 
end  of  the  humerus,  if  the  fragments  are  at  once  replaced,  the  coronoid  process  in 
front  and  the  muscular  and  tendinous  structures  behind  hold  them  firmly  and  prevent 
recurrence  of  deformity.  If  the  fracture  is  intercondylar,  or  T-shaped,  the  acutely 
flexed  position  not  only  holds  the  condyles  in  position,  but  tends  to  prevent  by 
pressure  the  involvement  of  the  joint  line  by  callus,  which  later  would  prove 
obstructive.  If  either  the  coronoid  or  olecranon  fossa,  or  both,  be  involved,  it  is 
more  important  to  prevent  the  filling  up  of  the  former  than  of  the  latter,  as  full  flexion 
is  of  far  greater  functional  importance  than  full  extension.  If  the  condyles — espe- 
cially the  inner — be  split  off,  the  position  relaxes  the  muscles  that  cause  displacement. 
It  is  also,  of  course,  the  most  useful  position  of  the  limb  in  case  ankylosis  does  occur. 

In  excision  of  the  elbow-joint  the  following  anatomical  points  should  be  remem- 
bered :   (1)  The  lines  of  the  various  epiphyses.     (2)  The  position  of  the  ulnar  nerve 


3o8  HUMAN    ANATOMY. 

in  the  groove  between  the  internal  condyle  and  olecranon.  (3)  The  close  relation 
of  the  posterior  interosseous  nerve  to  the  head  of  the  radius.  (4)  The  post-operative 
value  (in  extending  the  forearm)  of  the  outer  aponeurotic  expansion  of  the  triceps 
and  of  the  anconeus  muscle.     These  should  be  carefully  protected  from  injury. 

Landmarks. — The  following  points  may  be  mentioned  in  addition  to  those 
which  may  be  found  under  the  Humerus,  Radius,  and  Ulna  : 

A  line  from  one  condyle  to  the  other  will  be  at  right  angles  with  the  humeral 
axis,  but  will  be  oblique  in  relation  to  the  axis  of  the  forearm. 

The  line  of  the  radio-humeral  articulation  is  horizontal.  The  line  of  the  humero- 
ulnar  articulation  is  oblique  downward  and  inward  ;  the  tip  of  the  internal  condyle 
is  therefore  from  a  quarter  to  a  half  inch  farther  above  the  articular  line  than  is  the 
tip  of  the  external  condyle.  The  internal  condyle  points  backward  rather  than 
inward. 

The  length  of  the  articulation  line  is  about  two-thirds  of  the  length  of  a  line 
joining  the  tips  of  the  condyles.  In  semiflexion  the  external  condyle  is  easily  seen  ; 
in  acute  flexion  it  disappears,  and  the  rounded  capitellum  of  the  humerus,  with  the 
outer  edge  of  the  triceps  stretched  over  it,  can  be  seen  and  felt. 

The  Inferior  Radio-Ulnar  Joint. — This  articulation  has  been  dislocated  in 
a  few  instances,  in  most  of  which,  the  cause  having  been  extreme  pronation  of  the 
wrist,  the  lower  end  of  the  ulna  was  carried  backward,  projecting  on  the  back  of  the 
wrist  and  pointing  outward, — i.e.,  towards  the  middle  finger.  The  backward  dis- 
placement probably  involves  the  tearing  of  the  triangular  fibro-cartilage  and  a  rup- 
ture of  the  posterior  radio-ulnar  ligament.  The  deviation  of  the  ulna  to  the  radial 
side  may  be  due  to  the  action  of  the  pronator  quadratus.  The  shallowness  of  the 
sigmoid  cavity  on  the  radius  favors  recurrence  after  reduction.  But  little  is  known 
of  this  injury. 


THE   CARPUS.  309 


THE   HAND. 

The  hand  is  composed  of  the  carpus  or  wrist,  consisting  of  eight  small  bones 
arranged  in  two  rows,  which  is  succeeded  by  five  rays  of  four  segments  each, — 
namely,  a  metacarpal  bone  and  three  phalanges,  excepting  the  thumb,  in  which  one 
phalanx  is  wanting. 

THE   CARPUS. 

There  are  eight  carpal  bones  arranged  in  two  rows  of  four  each.  The  first  row 
includes,  named  from  the  radial  towards  the  ulnar  side,  the  scaphoid,  the  semilunar, 
the  cuneiform,  and  the  pisiform  ;  the  second  row,  the  trapezium,  the  trapezoid,  the 
os  magjuim,  and  the  unciform.  Exceptionally,  several  other  bones  may  occur,  due 
to  the  persistence  of  centres  laid  down  in  early  fcetal  life,  which  normally  fuse  with 
other  centres  or  disappear.  Thus  there  is  much  in  favor  of  the  view  that  the  plan 
of  the  carpus  is  more  complicated.  This  point  is  further  considered  in  the  dis- 
cussion of  variations  (page  313).  The  pisiform  of  the  first  row,  whatever  may  be 
its  morphological  significance,  is  in  man  practically  nothing  but  a  sesamoid  bone 
in  the  tendon  of  the  flexor  carpi  ulnaris,  resting  on  the  palmar  surface  of  the  cunei- 
form, and  having  no  share  in  the  mechanics  of  the  wrist  excepting  as  giving  attach- 
ment to  a  part  of  the  anterior  annular  ligament.  The  first  row,  therefore,  consists 
really  of  the  three  first-mentioned  bones,  which  are  joined  into  one  flexible  piece  by 
interosseous  ligaments.  The  upper  end  of  this  combination  bears  an  egg-shaped 
articular  surface  for  the  wrist-joint,  to  which  all  three  bones  contribute.  Its  lower 
side  has  a  concavo-convex  outline,  the  concavity  receiving  the  inner  two  bones  and 
the  convexity  bearing  the  outer  two  of  the  second  row.  The  latter  consists  of  four 
bones  connected  by  ligaments  :  the  trapezium,  for  the  thumb  ;  the  trapezoid  and 
os  magnum,  for  the  next  two  fingers  ;  and  the  unciform,  for  the  ring  and  little 
fingers.  The  dorsal  side  of  the  carpus  is  slightly  convex  and  the  palmar  deeply 
concave,  forming  by  its  middle  the  floor  of  a  deep  canal,  bridged  by  the  anterior 
annular  ligament,  which  runs  between  bony  elevations  on  each  side  of  the  carpus. 
To  shorten  the  description,  it  may  be  said  that  little  depressions  for  ligaments  can 
be  seen  on  well-marked  bones  near  their  edges  on  the  dorsal  and  palmar  aspects, 
especially  the  former. 

The  scaphoid  [os  naviculare] ,  or  boat-shaped  bone,  is  the  largest  and  most 
external  of  the  first  row.  It  is  a  flattened  elongated  disk  placed  with  the  long  axis 
running  outward  and  downward.  It  receives  its  name  from  being  convex  on  the 
upper  and  outer  side  for  the  radius  and  concave  on  the  opposite  side  for  the  head 
the  os  magnum.       Nearly  corresponding  with   the  long  axis  is  the  long  and  very 


For  radii 


surface 


Right  scaphoid,  dorsal  aspecl.  Right  scaphoid,  inner  aspect 


narrow  dorsal  surface.  The  palmar  surface  is  broader,  runs  more  downward,  arid 
the  outer  end  rises  into  the  tuberosity  of  the  scaphoid,  from  which  part  of  the  anterior 
annular  ligament  springs.  The  convex  proximal  surface  for  the  radius  is  wholly 
articular  ;  the  inner  edge  is  straight,  the  dorsal  and  palmar  converge  externally  ;  it 
tends  to  encroach  on  the  dorsal  surface.      Internally  there  are  two  surfaces,  both 


3io 


HUMAN  ANATOMY. 


articular  :  the  upper,  very  narrow,  articulates  at  its  lower  border  with  the  semilunar 
and  gives  attachment  above  to  the  fibro-cartilaginous  ligament  connecting  these 
bones  ;  the  lower  is  an  elongated  cavity  embracing  part  of  the  top  and  the  outer 
side  of  the  head  of  the  os  magnum.  The  outer  surface,  continuous  with  the  dorsum, 
is  a  small  groove  for  the  lateral  ligament  of  the  wrist.  The  distal  surface,  forming 
the  convexity  of  the  medio-carpal  joint,  articulates  with  the  trapezium  and  trapezoid. 
It  is  convex  in  all  directions.  The  scaphoid  articulates  with  Jive  bones, — the  radius, 
semilunar,  trapezium,  trapezoid,  and  os  magnum. 

The  semilunar  [os  lunatum]  receives  its  name  from  its  outline  when  seen  from 
the  side,  the  proximal  surface  being  convex  and  the  distal  deeply  concave.  The 
dorsal  surface  is  quadrilateral.      Its  proximal  and  inner  borders  are  longer  than  the 


Fig.  323. 


Fig.  324. 

For  cuneiform  For  1 

Dorsal 


For  scaphoid 
milunar,  outer  aspect. 


For  magnun 


lilunar,  inner  aspect. 


others,  so  as  to  make  it  kite-shaped,  the  long  axis  running  distally  outward.  The 
two  shorter  surfaces  meet  at  an  overhanging  point.  The  palmar  surface  is  of  the 
same  general  shape.  Its  larger  distal  portion  is  smooth  as  for  a  bursa.  The  proxi- 
mal surface  is  convex  and  articular,  chiefly  for  the  radius  ;  but,  extending  under  the 
triangular  cartilage,  broadest  at  the  scaphoid  edge,  it  narrows  internally.  The  con- 
cave distal  surface  is  divided  by  a  ridge  into  a  larger  part  for  the  os  magnum  and  an 
inner  for  the  edge  of  the  unciform.  An  outer  surface  articulates  with  the  scaphoid 
and  an  inner  with  the  cuneiform.  Both  are  semilunar,  but  the  outer  is  the  more 
slender.  Both  are  nearly  plane  and  practically  wholly  articular,  there  being  but  a 
slight  roughness  for  the  interosseous  ligaments  at  the  proximal  end  near  the  dorsum. 
The  semilunar  articulates  with  five  bones, — the  radius,  scaphoid,  cuneiform,  os 
magnum,  and  unciform. 

The  cuneiform  [os  triquetrum],  or  pyramidal,  is  of  such  form  that  the  latter 
name  is  the  more  fitting.  The  base  is  the  articular  surface  for  the  semilunar  ;  the 
apex  is  at  the  inner  side  of  the  wrist.  The  base  is  plane  and  articular  except  where 
the  interosseous  ligament  joins  it.      The  dorsal  surface  is  narrow  and  not  clearly 


For  pisiform 


Fig.  326. 


For  semilunar 


For  triangular  cartilage 
Right  cuneiform,  palmar  aspect. 


Dorsal  surface 
For  semilunar 


Non-articular 
Right  cuneiform,  distal  aspect. 


separated  from  the  proximal  on  the  macerated  bone.  The  proximal  surface  is  a 
triangle  with  the  base  inward,  and  has  near  the  base  a  smaller  triangle  of  articular 
surface  for  the  triangular  cartilage.  The  inner  half  of  the  palmar  surface  is  occupied 
by  a  round  facet  for  the  pisiform.  The  distal  s?erface  is  a  very  complexly  curved 
articular  facet  for  the  unciform.  It  suggests  a  saddle-joint  that  has  been  spirally 
twisted.     A  transverse  section  of  this  surface  is  concavo-convex  from  without  inward. 


THE   CARPUS. 


3ii 


A  vertical  section  near  the  outer  end  is  concave,  near  the  inner  convex.  It  is  prac- 
tically a  screw  surface.  A  small  part  of  the  inner  side  is  non-articular.  The  inner 
surface  is  the  apex  of  the  pyramid,  a  small  knob  for  the  lateral  ligament.  The 
cuneiform  articulates  with  three  bones, — the  semilunar,  pisiform,  and  unciform. 

The  pisiform  [os  pisiforme]  is  a  small  rounded  bone,  rough  everywhere  except 
where  the  greater  part  of  one  surface  is  occupied  by  a  round,  slightly  concave  articu- 
lar facet  which  joins  the  palmar  aspect  of  the  cuneiform.      The  facet  is  at  the  proxi- 


Fig.  327. 


Rough  surface  for  an- 
tenor  annular  lig- 
ament  and  flexor 
carpi  ulnaris 


Right  pisiform,  dorsal  aspect 


Fig.  328. 


For  cuneiform 


Right  pisitorm,  palmar  aspect 


mal  part  of  the  dorsal  surface,  the  bone  projecting  from  it  downward,  forward,  and 
inward,  lying  in  a  plane  anterior  to  that  of  the  outer  carpal  bones.  The  pisiform 
articulates  with  only  one  bone, — the  cuneiform. 

The  trapezium  [os  multangulum  majus]  is  distinguished  by  an  isolated  facet 
on  the  distal  surface  for  the  metacarpal  bone  of  the  thumb.  This  surface  is  that  of 
a  typical  saddle-joint,  concave  from  side  to  side  where  the  borders  are  most  raised  ; 
convex  from  before  backward  ;  broadest  transversely.  The  proximal  surface  is  a 
four-sided  concavity  for  the  scaphoid,  separated  by  a  ridge  from  the  inner  surface. 
The  inner  surface  is  subdivided  :  the  proximal  portion,  much  the  larger,  is  an 
articular  concavity  for  the  trapezoid  ;  the  distal  portion  is  rough  except  for  a  facet 
at  the  dorsum  for  a  part  of  the  side  of  the  second  metacarpal.  The  outer  surface  is 
concave,  receiving  the  lateral  ligament.  The  dorsal  surface  is  elongated  from  side 
to  side,   slightly  hollowed  in  the  middle,  with  a  variously  developed  tubercle  on 


Fig.  329. 


Fig.  330. 


For  first  metacarpal 


For  second 
metacarpal 

For  trape 


Ridge 


Groove  for 
carpi  radialis 
aphoid 


Right  trapezium,  proxi 


,       For  second 
metacarpal 
trapezoid 

iner  aspect. 


either  side.  On  the  palmar  surface  is  a  deep  groove  for  the  tendon  of  the  flexor 
carpi  radialis.  Just  beside  this  is  a  prominent  ridge  at  the  junction  with  the  external 
surface  for  a  part  of  the  outer  insertion  of  the  palmar  annular  ligament.  The  trape- 
zium articulates  with  fo?ir  bones, — the  scaphoid,  trapezoid,  and  first  and  second  meta- 
carpals. 

The  trapezoid  [os  multangulum  minus]  is  best  recognized  by  the  dorsal  surface, 
which  is  pointed  distally  where  it  projects  into  the  second  metacarpal.  The  outer 
convex  border  against  the  trapezium  is  much  longer  than  the  inner  against  the  os 
magnum.  The  proximal  border  runs  obliquely  forward  and  inward.  The  small 
palmar  surface  is  irregularly  quadrilateral.  The  proximal  surface  is  a  quadrilateral, 
nearly  plane,  facet  for  the  scaphoid,  longer  from  dorsum  to  palm  than  transversely. 
The  distal  surface,  entering  the  base  of  the  second  metacarpal,  is  divided  by  a  ridge 
into  two  facets,  concave  from  dorsum  to  palm,  of  which  the  inner  is  the  longer. 
The  internal  sicrf ace,  in  the  main  concave,  articulates  with  the  body  of  theos  mag- 
num, but  has  a  non-articular  surface  near  the  dorsum  for  an  interosseous  ligament. 
The  outer  surface  is  mostly  articular  and  slightly  convex,  joining  the  trapezium  ; 


312 


HUMAN    ANATOMY. 


distally  and  towards  the  palm  there  is  a  rough  surface  for  ligaments.      The  styloid 
process  of   the  third  metacarpal  often  reaches  the  dorsal  aspect  of   the  trapezoid 


For  mag 
Right  trapezoid, 


Right  trapezoid,  outer  and  distal  aspect. 


between  the  os  magnum  and  the  second  metacarpal.     The  trapezoid  articulates  with 
four  bones, — the  scaphoid,  trapezium,  os  magnum,  and  second  metacarpal. 

The  os  magnum  [os  capitatum]  is  the  largest  bone  of  the  carpus,  and  possesses 
a  head,  neck,  and  body.  The  head  is  a  rounded  articular  eminence  at  the  proximal 
end,  playing  in  a  socket  formed  by  the  scaphoid,  semilunar,  and  unciform.  The  con- 
vex articular  surface  extends  much  farther  on  the  dorsal  side  than  on  the  palmar.  A 
faint  line  above  often  separates  the  part  resting  on  the  scaphoid  from  that  resting  on 
the  semilunar.  The  former  extends  down  the  outer  side  of  the  head.  The  inner 
side  of  the  head  is  a  sharply  cut  plane  surface  articulating  with  the  unciform.  The 
neck  is  a  constriction,  best  marked  on  the  dorsal  aspect,  generally  seen  on  all  sides 
except  the  inner.  The  distal  surface,  broader  on  the  dorsal  end,  faces  a  little  out- 
ward. It  is  wholly  articular,  bearing  the  third  metatarsal  bone.  A  groove  in  the 
place  of  the  outer  angle  receives  the  edge  of  the  second  metatarsal.  A  smaller 
surface  for  the  fourth  exists  at  the  inner  angle  just  below  the  dorsum.      The  dorsal 


Fig.  334. 

Dorsal  surface    Neck     For  scaphoid 


Neck 
Right  os  magnum 


Right  os  magnum,  outer  aspect. 


surface  shows  the  head,  and  distally  to  it  a  sharp,  slightly  concave  inner  border,  a 
shorter  outer  one,  and  a  distal  one  slanting  downward  and  inward,  so  that  the  outer 
angle  is  obtuse  and  the  inner  would  be  acute,  but  that  the  point  of  the  angle  is 
replaced  by  a  small  border  touching  the  fourth  metacarpal.  The  palmar  surface  is 
narrow  and  prominent  below  the  neck.  The  inner  surface  is  rough  for  a  ligament 
near  the  palmar  border  ;  above,  it  has  a  narrow  articular  surface  for  the  unciform, 
continuous  with  that  on  the  head.  The  outer  surface  has  a  small  articulation  with 
the  trapezoid,  which  exceptionally  is  continuous  with  the  facet  on  the  head.  The 
os  magnum  articulates  with  seven  bones, — the  scaphoid,  semilunar,  trapezoid,  unci- 
form, and  second,  third,  and  fourth  metacarpals. 

The  unciform  [os  hamatum]  is  distinguished  by  a  prominent  hook  projecting 
from  the  inner  side  of  the  palmar  surface  for  a  part  of  the  annular  ligament.  The 
dorsal  surface  is  nearly  or  quite  triangular.  It  presents  an  oblique  proximal  border, 
a  nearly  straight,  but  often  convex,  outer  one,  and  a  distal  one  tending  to  meet  the 
inner  end  of  the  proximal  border.  Should  they  meet,  the  surface  is  tria'ngular  ;  but 
more  often  there  is  a  very  short  inner  border  separating  them,  which  is  either  straight 


THE    CARPUS. 


313 


or  concave.  The  palmar  surface,  of  about  the  same  shape  as  the  dorsal,  presents 
externally  a  deep  groove,  a  part  of  the  canal  for  the  flexor  tendons,  overhung  inter- 
nally by  the  unciform  process,  which  has  a  broad  outer  and  inner  surface,  the  former 
concave  and  smooth,  the  latter  convex.  The  free  border  of  the  hook  presents  a 
curved  outline  from  the  inner  side.  The  rounded  edge  between  the  proximal  and 
outer  surfaces  rests  against  the  semilunar.  The  p?-oximal  surface  is  a  spirally 
twisted,  oblong  facet  corresponding  to  the  adjacent  side  of  the  cuneiform,  with  a 
prominent  convexity  at  the  proximal  end.  The  outer  surface,  rough  at  the  distal 
and  palmar  angles  for  an  interosseous  ligament,  is  elsewhere  articular  for  the  os 


rIG, 

335- 

Fig.  336. 

For  cuneiform 

For  magm 

1  ..,  '  ith 

niii.l.   J  [  p,[] 

For  fourth,, 
metacarpal 

-     • 

!\ 

l   1,11                '.,,[,'>! 

For  fifth— fi 
metacarpal   \ 

%    \f\ 

Right  unciform,  inner  and  proximal  aspect. 


Hook 
riform,  outer  and  distal  aspect. 


magnum.  The  distal  surface,  wholly  articular,  bears  the  fourth  and  fifth  metacarpals, 
a  ridge  marking  the  interspace  between  them.  The  surface  is,  in  the  main,  convex 
from  side  to  side  and  concave  from  dorsum  to  palm.  Often,  however,  the  part  for 
the  fourth  finger  is  concave  from  side  to  side  and  convex  in  the  other  direction. 
The  distal  surface  may  meet  the  proximal  at  a  sharp  border,  or  a  very  narrow  rough 
surface  may  intervene.  The  unciform  articulates  with  five  bones, — the  semilunar, 
cuneiform,  os  magnum,  and  fourth  and  fifth  metacarpals. 

Development  and  Variations. — In  early  fcetal  life  centres  appear  for  the 
above-described  carpal  bones,  and  also  for  many  others,  which  disappear,  or  are 
fused  with  the  usual  ones,  long  before  the  appearance  of  bone.  Additional  carpals 
depend  either  on  the  persistence  and  subsequent  ossification  of  centres  that  normally 
are  lost  or  on  the  separate  development  of  two  or  more  that  should  fuse.  The 
number  of  carpal  elements  is  put  by  Pfitzner 1  at  thirty-three.  He  arranges  the 
constant  and  possible  bones  in  five  rows  :  (1)  an  antibrachial  row,  consisting  of  an 
ossification  in  or  on  the  triangular  cartilage,  representing  the  os  intermedium,  and  a 
little  apparent  outgrowth  from  the  pisiform  ;  (2)  a  proximal  row,  consisting  of  the 
normal  bones  and  certain  subdivisions  of  the  scaphoid  and  cuneiform  ;  (3)  a  central 
row,  composed  entirely  of  occasional  bones  ;  (4)  a  distal  row,  composed  of  the  four 
normal  bones  plus  a  minute  metastyloid ;  (5)  a  carpo-metacarpal  row,  composed 
entirely  of  occasional  bones.  The  most  common  anomaly  is  the  appearance  of  a 
styloid  bone,  which  is  the  separated  styloid  process  of  the  third  metacarpal.  The 
metastyloid  of  the  fourth  row  is  a  minute  bone  representing  the  very  tip  of  the  styloid. 
Very  rarely  the  scaphoid  is  divided  into  a  radial  and  an  ulnar  part.  The  os  centrale 
is  the  persistence  of  still  another  piece,  which  normally  either  joins  the  scaphoid  in 
the  third  month  of  foetal  life  or  disappears.  It  apparently  is  composed  of  a  dorsal 
and  a  palmar  element,  of  which  the  latter  is  the  more  subject  to  degeneration.  The 
os  magnum  contains  two  elements  exceedingly  rarely  found  distinct,  the  subcapi- 
tatum  on  the  distal  end  of  the  palmar  surface  and  the  subcapitatum  secundarium 
forming  the  inner  distal  angle  of  the  dorsum.  The  hook  of  the  unciform  may  be 
separate.  Fusion  may  occur  between  bones  normally  distinct.  The  semilunar  may 
fuse  with  the  cuneiform,  especially  in  negroes. 

Ossification  occurs  from  one  centre  for  each  bone  ;  but  according  to  some 
authorities,  the  unciform  and  the  scaphoid  have  two  centres.      The  former  and  the  os 

1  Zeitschrift  fiir  Morphologie  und  Anthropol.,  Bd.  ii.,  1900. 


3H 


HUMAN   ANATOMY, 


magnum  are  the  first  to  ossify,  the  process  beginning  in  the  latter  part  of  the  first 
year.  The  order  of  its  appearance  in  the  other  bones  is  very  uncertain.  Those  of 
the  first  row,  excepting  the  pisiform,  contain  bone  by  the  end  of  the  first  five  or  six 

Fig.  337- 


Ossification  of  bones  of  hand.  A,  at  birth;  B,  latter  half  of  first  year;  Cat  three  years;  D,  at  eicht  years 
E,  at  twelve  years,  a,  centres  for  shafts  of  metacarpals  and  phalanges;  J,  magnum ;  c,  unciform;  dt  cuneiform 
<?,  base  of  first  metacarpal ;  ft  heads  of  metacarpals ;  g-,  bases  of  proximal  phalanges ;  h,  bases  of  distal  phalanges 
z,  scaphoid  ;  /,  trapezium  ;  k,  trapezoid  ;  /,  semilunar  ;  m,  bases  of  middle  phalanges  ;  n,  pisiform. 

years.  These  are  followed  by  the  trapezium  and  the  trapezoid,  so  that  by  the  eighth 
year  the  process  has  begun  in  all  the  carpals  save  the  pisiform,  in  which  it  begins 
about  the  twelfth  year. 

THE  METACARPAL  BONES. 
The  metacarpal  bone  of  the  thumb '  in  many  respects  resembles  a  phalanx  and 
calls  for  a  separate  description;  the  others  have  the  following  points  in  common. 
They  possess  a  shaft 2  and  two  extremities,  of  which  the  proximal  is  the  base  and  the 
distal  the  head:''  Each  base4  has  an  articular  surface  at  the  end  to  join  the  carpus  and 
one  on  the  side  or  sides  that  come  into  contact  with  the  other  metacarpal  bones,  with 
a  depression  for  an  interosseous  ligament  beyond  it.  The  bases  themselves  are 
cubical  and  rough  both  above  and  below.  The  shaft  narrows  in  front  of  the  base, 
and  has  a  median  dorsal  ridge,  which  soon  divides  into  two  lines  running  to  either 
side  of  the  head,  thus  bounding  a  long,  flat  dorsal  surface  occupying  more  than  half 
the  bone.  A  palmar  ridge  runs  nearly  the  whole  length  of  the  shaft,  dividing  very 
near  the  head  into  two  faint  lines  to  either  side  of  it.  Thus,  near  the  base  the 
shaft  may  be  called  cylindrical,  with  a  ridge  above  and  below,  while  farther  forward 
it  has  a  dorsal  and  two  lateral  sides.  This  description  applies  most  closely  to  the 
bone  of  the  index,  and  becomes  less  and  less  accurate  as  we  proceed  to  the  little 

1  Os  metacarpale  I.     -  Corpus.     3Capitulum.     4  Basis. 


THE    METACARPAL    BONES. 


3i5 


finger.  The  distal  end  or  head  has  a  rounded  articular  surface  projecting  to  the 
palmar  side,  while  it  does  not  rise  above  the  level  of  the  dorsum.  Both  on  the  palmar 
and  dorsal  aspects,  but  especially  on  the  former,  its  angles  are  produced  backward, 
and  the  whole  surface  encroaches  a  little  more  on  the  palmar  side,  where  it  is  de-' 
cidedly  broader  than  on  the  back.    A  tubercle  exists  on  each  side  where  the  diverging 


Ext.  carpi  ulnaris 
Styloid  process 


RD    PHALANX 


i  of  right  hand,  dorsal  aspect 


lines  of  the  dorsum  end,  with  a  depression  below  it  on  the  side  of  the  head.  The  lat- 
eral ligaments  spring  from  both  tubercle  and  depression.  The  nutrient  foramina, 
excepting  that  of  the  first  metatarsal,  are  recurrent,  running  towards  the  proximal  end. 
Peculiarities  of  the  Different  Metacarpals. — The  first  metacarpal  is 
shortest,  the  second  longest,  from  which  the  remaining  ones  decrease  in  length 
from  without  inward.      The  chief  distinguishing  marks  are  on  the  bases. 


316 


HUMAN   ANATOMY. 


The  first  metacarpal,  shorter  than  the  others,  has  a  nearly  flat  dorsal  surf  ace 
bounded  by  two  definite  borders,  of  which  the  outer  is  the  sharper.  The  palmar 
surface  of  the  shaft  is  overhung  by  the  ends.  It  is  thickest  and  most  convex  towards 
the  inner  side.  These  two  points  are  the  best  guides  to  determine  the  side  the  bone 
belongs  to.      The  difference  is  striking  in  a  transverse  section.      The  base  is  broad 


For  triangular  cartilage 


Abductor  and  flexor 
■  pollicis 
Adductores 
obliquus  et 
transvcrsus 


and  runs  to  a  point  on  the  palmar  aspect  rather  nearer  the  inner  side.  A  groove 
for  the  capsule  surrounds  the  joint,  and  on  the  outer  side  is  a  tubercle  for  the  tendon 
of  the  extensor  of  the  bone.  The  articular  proximal  end  is  convex  from  side  to  side 
and  concave  from  above  downward,  forming  a  typical  saddle-joint  with  the  trapezium. 
The  head  is  also  broader  from  side  to  side.      The  articular  surface  is  carried  only  a 


THE   PHALANGES.  317 

little  way  onto  the  dorsum,  but  bends  strongly  forward,  ending  in  two  lateral  pro- 
longations with  a  notch  between  them,  on  each  of  which  a  sesamoid  bone  plays. 
The  outer  of  these  is  the  more  prominent.  The  nutrient  foramen  runs  towards  the 
distal  end. 

The  second  metacarpal  has  a  base  which  is  triangular  when  seen  from  the 
end,  and  forked  to  straddle  the  point  of  the  trapezoid.  On  the  outer  side  is  a  small 
square  facet  near  the  dorsum  for  the  trapezium  ;  on  the  inner  side  there  is  a  narrow 
oblique  surface  for  the  os  magnum,  and  in  front  of  it  one  showing  a  tendency  to 
subdivide,  articulating  with  the  next  bone. 

The  third  metacarpal  has  an  oblong  proximal  surface,  broadest  on  the  dor- 
sum, where  a  tubercle,  the  styloid  process,  projects  towards  the  trapezoid.  We  have 
found  the  third  metacarpal  touching  this  bone  in  forty  per  cent,  of  100  specimens, 
and  sometimes  this  occurred  when  the  styloid  process  was  not  particularly  developed. 
Externally  there  is  a  facet  like  the  lower  part  of  the  inner  one  of  the  second,  and 
internally  a  double  one  to  meet  the  next. 

The  fourth  metacarpal  has  a  nearly  square  upper  surface  articulating  with 
the  unciform,  and  therefore  of  uncertain  nature, — sometimes  convex,  sometimes 
concave.  At  the  outer  dorsal  angle  of  this  surface  is  a  small  distinct  facet  for  a  joint 
with  the  os  magnum.  On  the  outer  side  are  two  facets  for  the  third,  and  on  the 
inner  a  long  one,  concave  from  dorsum  to  palm,  for  the  fifth. 

The  fifth  metacarpal  has  a  base  generally  broader  than  deep,  concave  from 
side  to  side  and  convex  from  above  downward.  A  single  facet  on  the  outer  side 
has  a  convexity  to  meet  the  concavity  on  the  fourth.  The  inner  side  has,  of  course, 
no  facet,  but  a  tubercle.  The  dorsal  ridge  on  this  bone  is  twisted,  starting  from  the 
inner  side. 

Development. — Each  bone  has  two  centres,  a  primary  one  for  the  shaft, 
appearing  early  in  the  third  month  of  fcetal  life,  and  one  for  an  end,  appearing  in  the 
third  year.  The  secondary  centre  is  for  the  distal  end  in  the  four  inner  metacarpals 
and  in  the  proximal  of  the  first, — that  is,  at  the  end  towards  which  the  nutrient 
artery  does  not  run.  They  fuse  at  about  eighteen.  Rarely  smaller  epiphyses 
appear  at  the  other  ends  also,  as  in  mammals  generally.  A  centre  for  the  styloid 
process  of  the  third  is  sometimes  seen,  and  it  may  become  distinct,  as  an  extra  carpal 
bone,  or  it  may  fuse  with  one  of  the  adjoining  ones. 

THE   PHALANGES. 

Features  of  Each  Bone. — The  phalanges1  of  the  first  and  second  row  differ 
(except  in  size)  only  in  the  proximal  ends.  The  dorsum  of  the  shaft  is  rounded 
from  side  to  side  ;  the.  palmar  surface  is  flat  with  raised  edges  for  the  sheaths  which 
bind  down  the  tendons  very  closely.  It  is  considerably  overhung  by  the  distal  and 
somewhat  by  the  proximal  end.     The  nutrient  foramen,  when  present,  runs  distally. 

The  proximal  end  of  the  frst  row  is  a  concave  articular  surface,  broadest  trans- 
versely. A  groove  runs  round  the  end,  except  on  the  palmar  surface,  for  the  cap- 
sule and  for  fibres  from  the  extensor  tendons  of  the  fingers  on  the  dorsum.  Two 
very  slight  inequalities  in  front  mark  the  attachment  of  the  glenoid  ligament.  There 
is  a  rough  tubercle  on  each  side,  just  below  the  groove  for  the  partial  insertion  of 
the  interosseous  muscles.  The  distal  end  in  both  the  first  and  second  rows  has  an 
articular  surface  which  curves  over  two  condylar  promi?iences,  separated  by  a  median 
furrow,  onto  the  palmar  aspect.  This  surface  is  seen  on  the  dorsum  only  as  a  small 
curved  median  facet  which  broadens  as  it  passes  over  the  end  and  continues  to 
expand  to  its  termination.  The  lateral  borders  of  the  joint  are  well  defined.  A 
depression  with  an  overhanging  tubercle  is  on  each  side  of  this  end  ;  both  depression 
and  tubercle  give  attachment  to  the  lateral  ligament. 

The.  proximal  ends  of  the  second  and  third  rows  are  essentially  the  same.  They 
differ  from  that  of  the  first  row  because,  while  the  latter  fits  onto  the  single  rounded 
end  of  a  metacarpal,  those  of  the  two  distal  rows  fit  onto  double  condylar  ends. 
Thus  the  proximal  articular  surface  presents  a  median  elevation,  separating  two 
hollows,  continued  into  a  projecting  point  on  the  surface  front  and  back.  In  the 
phalanges  of  the  second  row  the  dorsal  point  is  the  larger  ;  in  the  last  row  the  points 

1  Phalanges  digitorum  tuanus. 


3i8  HUMAN   ANATOMY. 

are  about  equal.  In  the  last  row  the  palmar  point  is  at  a  lower  level  than  the  rough- 
ness that  succeeds  it.  There  is  a  transverse  ridge  in  both  on  the  dorsal  aspect  for 
extensor  tendons  ;  the  flexor  tendons  are  inserted  on  the  palmar  side  to  a  slight 
ridge  on  the  second  phalanx  and  to  a  roughness  spreading  considerably  on  the  shaft 
of  the  terminal  one. 

The  phalanges  of  the  third  row  are  much  smaller  and  flatter  than  the  preceding. 
The  dorsum  of  the  diminutive  shaft  is  convex  from  side  to  side  and  its  palmar  aspect 
plane  where  not  encroached  upon  by  roughnesses.  The  free  end  is  sharp  and 
rounded,  with  points  at  each  end  projecting  backward.  The  dorsal  distal  border 
bears  a  narrow  semilunar  roughness  ;  a  much  broader  one  on  the  palmar  side  sup- 
ports the  pulp  of  the  end  of  the  finger,  giving  firm  attachment  to  the  connective 
tissue. 

Peculiarities  of  Individual  Phalanges.  —  Every  phalanx  of  the  first  row  is 
longer  than  any  of  the  second  row.  The  first  and  second  phalanges  of  the  middle 
finger  are  longer  than  the  corresponding  ones  of  the  ring  finger,  which  in  turn  sur- 
pass those  of  the  index.  Those  of  the  little  finger  are  the  smallest.  The  terminal 
phalanges  are  of  very  nearly  the  same  length. 

The  phalanges  of  the  first  row  have  the  following  peculiarities.  That  of  the 
index-finger  has  a  very  large  external  tubercle  at  the  dorsum  ;  the  hollow  at  the  base 
is  deeper  than  that  of  any  other  ;  the  base  is  relatively  strong  compared  with  the  shaft, 
which  is  flatter  than  any  other.  The  phalanx  of  the  middle  finger  is  strong  in  all  its 
parts ;  there  is  a  large  external  tubercle,  often  divided  into  a  dorsal  and  a  palmar  part ; 
at  the  distal  end  the  ulnar  condyle  is  more  prominent.  The  phalanx  of  the  ring 
finger  has  the  base  relatively  small  and  the  condyles  relatively  large,  so  that  the 
borders  are  nearly  parallel  ;  the  dorsum  is  more  convex  transversely  than  that  of  the 
third,  and  much  more  so  than  that  of  the  index  ;  it  is  also  narrower.  The  phalanx 
of  the  little  finger  is  weak,  narrowing  rapidly  so  as  to  appear  pointed  ;  there  is  a 
tubercle  at  the  inner  and  dorsal  side  of  the  base,  and  the  radial  condyle  is  the  more 
projecting.  One  cannot,  therefore,  determine  to  which  side  the  phalanx  of  the  ring 
finger  belongs. 

In  the  second  row  the  phalanx  of  the  middle  finger  is  always  stronger  than 
that  of  the  ring  finger,  and  the  latter  than  that  of  the  index.  According  to  Pfitzner,1 
the  distal  ends  are  the  more  characteristic.  In  the  second  finger  the  radial  condyle 
is  the  more  prominent  ;  this  is  also  true  in  the  third,  but  to  a  less  degree  ;  the  ulnar 
condyle  is  the  larger  in  the  fourth,  and  still  more  so  in  the  fifth. 

The  distal  or  terminal  phalanges  can  be  distinguished  more  surely  by 
strength  than  by  length  ;  the  third  is  the  strongest  ;  then  comes  the  fourth  ;  next 
the  second,  which  is  more  or  less  pointed  ;  and  last  the  fifth,  which  is  relatively 
weak.  These  characteristics  are  to  be  used  with  great  caution  in  drawing  differential 
deductions. 

Development. — The  phalanges  have  each  a  centre  for  the  shaft  and  one  for 
the  proximal  end.  The  former  appears  in  the  latter  half  of  the  third  month  of  fcetal 
life  at  about  the  same  time  in  the  terminal  and  proximal  rows.  Probably  the  termi- 
nal row  shows  ossification  somewhat  earlier  than  the  other  (Bade).  The  centres 
for  the  second  phalanges  appear  after  a  distinct  interval  about  the  middle  of  the 
fourth  month.  In  both  the  first  and  second  rows  the  centre  appears  nearer  the 
proximal  end.  It  is  said  that  in  all  the  rows  ossification  begins  in  the  middle  finger, 
next  in  the  index,  and  later  in  the  ring  and  little  fingers  ;  there  is,  however,  con- 
siderable variation.  The  centre  for  the  second  phalanx  of  the  little  finger  is  dis- 
tinctly later  than  the  others.  Ossification  begins  in  the  epiphyses  in  the  third  year 
or  later.  They  are  fused  by  eighteen.  In  addition  to  the  proximal  epiphyses,  the 
terminal  phalanges  have  each  a  distal  cap-like  ossification  of  perichondrial  origin, 
which  quickly  joins  the  shaft. 

Sesamoid  bones2  occur  in  the  metacarpo-phalangeal  joints.  In  the  fcetus  of 
the  fourth  month  they  are  very  numerous,  but  many  disappear  by  fusion  or  other- 
wise during  development.  A  pair  is  constant  in  the  joint  of  the  thumb.  They  are 
two  bones  of  variable  size,  in  general  rather  larger  than  a  small  pea,  lying  on  the 
palmar  side  of  the  head  of  the  first  metacarpal.  The  tendon  of  the  long  flexor  passes. 
]Schwalbe's  Morpholog.  Arbeiten,  Bd.  i.  and  ii.,  1893. 


PRACTICAL    CONSIDERATIONS  :    THE    HAND    BONES. 


3T9 


between  them.  They  each  have  one  cartilage-covered  surface  against  the  bone  and 
are  otherwise  surrounded  by  fibrous  tissue.  A  small  one  on  the  radial  side  of  the 
joint  of  the  index-finger  occurs  in  rather  less  than  half  the  cases,  and  one  on  the 
ulnar  side  of  the  little  finger  in  rather  more  than  four-fifths.  Pfitzner1  gives  the 
following  table  of  percentages  showing  the  frequency  of  the  various  sesamoid  bones, 
combining  his  work  and  that  of  Thilenius  : 


Ring. 


Fourth-month  foetus  .    . 
Fourteen  to  ninety  years 


30 
1323 


Rad.       Uln. 
IOO  IOO 

99.9      IOO 


46  23 

47.8       O.  I 


30 

i-5 


23    30 
o       o.  I 


Rad.      Uln. 
15         63 
2.3     82.4 


Variations  in  the  number  of  the  fingers  are  generally  regarded  as  malforma- 
tions. The  most  common  occurrence  is  an  extra  finger,  the  identification  of  which 
is  not  certain.  It  seems  often  as  if  we  should  content  ourselves  with  saying  that 
there  is  an  extra  finger,  but  that  no  particular  one  has  been  repeated.  Sometimes 
the  thumb  has  three  phalanges.  Occasionally  any  of  the  terminal  phalanges  is 
doubled.  A  very  uncommon  condition  is  that  of  seven  or  eight  fingers  and  no 
thumb.  The  dissection  of  such  a  case  revealed  the  absence  of  the  radius  and  of  the 
radial  side  of  the  wrist,  the  skeleton  of  the  forearm  consisting  of  two  ulnae,  and  that 
of  the  hand  of  the  ulnar  sides  of  two  opposite  ones  fused  together. 

PRACTICAL    CONSIDERATIONS. 

The  Carpus. — Of  the  carpal  bones  the  scaphoid  and  semilunar  are  most  fre- 
quently broken,  on  account  of  their  more  direct  relation  to  the  line  of  transmission 
of  force  in  falls  upon  the  hand.  The  diagnosis  is  difficult,  and  has  been  made 
oftenest  by  the  help  of  a  skiagraph.  There  is  but  little  displacement.  The  other 
bones  of  the  carpus,  on  account  of  their  shortness,  irregular  and  rounded  shape, 
and  compact  union  by  strong  ligaments  which  yet  permit  slight  movements  be- 
tween the  bones,  usually  escape  injury  except  in  cases  of  crush  of  the  whole  hand. 
They  are,  however,  not  infrequently  the  seat  of  tuberculous  disease,  as  might  be 
expected  from  their  great  liability  to  traumatism  of  all  grades.  Their  synovial  re- 
lations (Fig.  342)  favor  the  spread  of  such  disease  from  one  bone  to  the  remainder, 
and  render  conservative  treatment  unsatisfactory.  The  result,  too,  is  affected  by  the 
close  proximity  of  the  flexor  and  extensor  tendons,  which  become  involved  in  the 
tuberculous  process  or  bound  down  by  adhesions. 

The  Metacarpus. — The  first  metacarpal  bone,  which  is  morphologically  a 
phalanx,  is,  like  all  the  phalanges,  developed  from  an  epiphysis  situated  at  its 
proximal  end.  But  one  case  of  disjunction  has  been  recognized  during  life.  It  re- 
sembled a  dislocation  at  the  carpo-metacarpal  joint,  but  the  seat  of  abnormal  move- 
ment was  below  the  level  of  the  lower  edge  of  the  trapezium.  In  the  remaining 
metacarpal  bones  the  epiphysis  is  situated  at  the  distal  extremity. 

Falls  upon  or  striking  with  the  closed  fist  tend  to  produce  forward  displace- 
ment. As  the  metacarpal  bones  of  the  index-,  middle,  and  ring  fingers  are  the 
longer,  their  epiphyses  are  more  likely  to  be  separated  in  this  manner.  A  fall  on 
the  extended  fingers  and  metacarpo-phalangeal  region  may  cause  backward  displace- 
ment, though  this  is  rarer. 

The  diagnosis  from  dislocation  of  the  proximal  phalanges  is  not  easy.  It  is 
aided  by  the  recognition  of  "  muffled  crepitus"  (Poland)  and  by  the  great  tendency 
of  the  deformity  to  recur,  due  partly  to  the  small  articular  areas  of  the  separated 
bones  and  partly  to  the  action  of  the  flexors  and  the  interossei.  Skiagraphy  will 
usually  establish  the  diagnosis. 

Fracture  of  the  metacarpal  bones  is  usually  the  result  of  a  blow  with  the 
clinched  fist.  The  metacarpals  of  the  thumb  and  little  finger  are  therefore  rarely 
broken.  On  account  of  the  mode  of  application  of  the  force,  the  seat  of  fracture  is 
1  Zeitschrift  fur  Morph.  und  Anthropol.,  Bd.  ii.,  1901. 


320  HUMAN  ANATOMY. 

apt  to  be  near  the  distal  end,  although  the  thinnest  and  weakest  parts  of  the  bones 
are  just  above  the  middle  and  they  sometimes  break  there.  The  proximal  fragment 
is  held  firmly  by  its  ligamentous  attachments  and  is  less  movable  than  the  phalangeal 
portion  ;  its  distal  end  may  project  on  the  dorsum.  The  knuckle  of  the  affected 
finger  sinks  and  partially  disappears.  The  lumbricales  and  the  interossei  aid  in 
producing  this  deformity,  and  may  cause  the  proximal  end  of  the  distal  fragment  to 
become  prominent  on  the  dorsum  of  the  hand.  In  examining  for  these  fractures  it 
should  be  remembered  that  the  metacarpal  bones  of  the  index-  and  middle  fingers  are 
bound  tightly  to  the  carpus  and  possess  but  little  power  of  independent  movement. 
The  others  are  more  movable.  In  the  treatment  of  these  fractures  the  normal  palmar 
concavity  of  the  metacarpal  bones  should  never  be  forgotten. 

The  Phalanges. — Epiphyseal  separation  of  the  phalanges  is  extremely  rare. 
The  epiphyses  are  all  at  the  upper  ends  of  the  bones.  The  diagnosis  from  severe 
sprain  or  from  fracture  will  usually  be  made  by  the  X-rays.  It  is  now  thought  that  not 
a  few  of  the  cases  of  necrosis  of  the  proximal  end  of  a  phalanx  following  acute  inflam- 
mation or  whitlow  are  the  result  of  epiphyseal  sprain  or  disjunction.  Of  course, 
necrosis  is  often  the  sequel  of  the  spread  of  infection  from  the  superficial  structures 
of  the  hand  to  the  closely  applied  fibro-cellular  tissue  over  the  terminal  phalanges. 

Fractures  occur  most  frequently  in  the  proximal  and  most  rarely  in  the  ter- 
minal phalanges.  The  relation  of  the  tendons  on  the  dorsal  and  palmar  surfaces 
usually  prevents  any  marked  displacement.  Occasionally  an  anterior  angular  de- 
formity of  the  proximal  phalanx  is  seen  after  fracture.  It  is  believed  to  be  favored 
by  the  action  of  the  interossei. 

The  frequency  with  which  both  tuberculous  and  syphilitic  inflammations  affect 
the  phalanges  is  probably  due  to  their  exposure  to  slight  injury.  They  are,  how- 
ever, not  often  the  subject  of  post-typhoidal  infection.  The  cause  of  whitlow  has 
already  been  mentioned,  and  will  be  recurred  to.  The  reason  for  the  over- 
growth of  the  bony  structures  of  the  hand  in  acromegaly  and  in  hypertrophic  pul- 
monary osteo-arthropathy  is  not  known.  In  the  latter  case  it  has  been  suggested 
that  the  enlargement  of  the  terminal  phalanges,  like  the  "  clubbing"  of  the  fingers  in 
phthisical  patients,  may  be  due  to  an  osteogenetic  stimulus  derived  from  the  pres- 
ence in  the  circulation  of  the  secondary  products  of  the  pulmonary  infection.  This 
would  be  analogous  to  the  increased  rapidity  of  growth  observed  in  adolescents 
during  convalescence  from  typhoid. 

Landmarks. — On  the  inner  side  of  the  hand,  below  the  wrist,  the  pisiform 
bone  can  be  felt,  and  when  grasped  firmly  can  be  given  slight  lateral  movement. 
Lower  and  more  externally  the  hook  of  the  unciform  can  be  made  out.  On  the 
outer  side  the  tuberosity  of  the  scaphoid  just  below  and  internal  to  the  radial  sty- 
loid and  still  lower  the  ridge  of  the  trapezium  may  both  be  felt.  With  the  hand 
in  full  flexion,  the  dorsal  prominence  of  the  scaphoid  and  semilunar  and  the  curved 
line  of  their  articulation  with  the  radius  may  be  felt  ;  the  anterior  and  posterior 
lips  of  the  articular  surface  of  the  latter  bone  can  be  palpated  and  the  groove  or 
depression  beneath  them  recognized.  The  projection  of  the  os  magnum  on  the 
back  of  the  hand,  and  occasionally  of  the  base  of  the  third  metacarpal  at  its  articu- 
lation with  the  os  magnum,  may  easily  be  felt.  When  an  unusual  prominence  of  these 
bones  exists,  and  is  first  noticed  after  a  fall  or  strain,  it  sometimes  leads  to  a  mis- 
taken diagnosis  of  exostosis  or  of  ganglion. 

The  metacarpal  bones,  their  concavity,  their  expanded  anterior  extremities  form- 
ing the  knuckles,  the  shape  and  size  of  the  shafts  and  ends  of  the  phalanges,  and  of 
their  articulations  with  the  metacarpus  and  with  each  other,  can  all  readily  be  made 
out  through  or  between  the  overlying  tendons. 

The  surface  markings  of  the  hand  and  of  its  joints  will  be  considered  later  (page 
621.) 

LIGAMENTS   OF   THE   WRIST   AND   METACARPUS. 

The  ligaments  and  joints  of  the  wrist  include  three  articulations,  the  radio- 
caipal,  the  intracarpal,  and  the  carpo-metacarpal,  which  often  receive  detailed 
separate  description.  The  simpler  and  in  many  ways  more  desirable  conception  of 
these  joints  is  to  regard  them  as  parts  of  a  common  articulation  consisting  of  a 


LIGAMENTS    OF    THE    WRIST    AND    METACARPUS. 


321 


general  capsular  ligament  enclosing  synovial  cavities  separated  by  an  interarticular 
fibro-osseous  septum  composed  of  the  bones  of  the  first  tow  and  their  interosseous 
ligaments.  Preparatory  to  the  common  description  which  follows,  it  is  necessary  to 
consider  the  ligaments  and  relations  of  the  groups  of  bones  which  take  part  in  the 
formation  of  the  subdivisions  of  the  general  articulation. 

The  pisiform  being  practically  a  sesamoid  bone,  the  upper  end  of  the  carpus  is 
an  egg-shaped  articular  surface  made  chiefly  by  the  convexities  of  the  scaphoid  and 
semilunar  and  to  a  small  extent  by  the  cuneiform  (Fig.  340).  These  three  bones 
are  united  into  one  apparatus  by  two  strong  interosseous  ligaments  situated  just 
below  the  proximal  ends  of  the  bones,  covered  by  synovial  membrane  and  com- 

Fig.  340. 


Triangular  cartilage      pro^; 
Semilunar  JS 


Interosseous 
carpo-metacarpal 
ligament 


Dorsal  ligament  of  first  row 
Scaphoid 


ML_Trapezoid 


Dorsal  intermetacarpal  ligaments 


Dorsal  aspect  of  right  wrist.  The  joint  of  ulna  is  opened  and  the  shaft  displaced  forward  and  inward  to  show 
under  side  of  head.  The  radio-carpal,  intracarpal,  and  carpo-metacarpal  joints  are  shown  by  removing  the  dorsal 
ligaments  and  flexing  the  hand. 

pleting  the  articular  surface.  They  completely  shut  off  the  radio-carpal  from  the  in- 
tracarpal joint.  The  latter  is  concavo-convex,  the  concave pa?'t  being  formed  by  the 
cuneiform,  the  semilunar,  and  the  hollow  surface  of  the  scaphoid  ;  the  convexity  by 
the  lower  surface  of  the  latter  bone,  which  articulates  with  the  trapezium  and  trape- 
zoid. The  concavity  amounts  to  a  socket,  of  which  the  side  formed  by  the  scaphoid 
is  nearly  at  right  angles  to  the  base,  while  the  inner,  formed  by  the  cuneiform,  is 
oblique.  The  scaphoid  is  attached  to  the  semilunar  much  less  tightly  than  is  the 
cuneiform,  so  that  considerable  motion  occurs  between  them.  The  scaphoid,  besides 
sliding  in  various  directions  on  the  semilunar,  can  turn  on  an  approximately  trans- 
verse axis  through  its  proximal  part,  which  permits  of  flexion  and  extension,  to 
some  degree  independent  of  the  rest  of  the  first  row.      Its  lower  end  may  also  move 


322 


HUMAN    ANATOMY. 


somewhat  outward  and  inward,  so  as  to  broaden  or  narrow  the  socket.  The  distal 
row  of  carpal  bones  presents  a  prominence  made  by  the  os  magnum  and  the  unci- 
form, which  are  held  firmly  together  so  as  to  move  nearly  as  one,  fitting  into  the 
socket  presented  by  the  first  row.  The  outer  side  of  this  prominence  is  quite 
straight,  making  an  entering  angle  with  the  trapezoid,  receiving  the  ridge  between 
the  concavity  and  convexity  of  the  scaphoid.  At  this  point  near  the  palmar  surface 
the  os  magnum  receives  a  ligament  from  the  scaphoid,  which  may  occasionally 
deserve  to  be  called  interosseous.  The  pisiform  has  a  capsular  ligament  enclosing 
the  joint  between  it  and  the  cuneiform. 

The  four  bones  of  the  second  row  are  joined  by  three  interosseous  ligaments :  one 


Inferior  dorsal  radio-ulnar. 
ligament  (relaxed) 


Dorsal 
carpo-metacarpal  ligaments 


Dorsal  transverse  ligament 


'JZ1-A,    Accessory  bands 


Dorsal  aspect  of  right  wrist. 

between  the  trapezium  and  trapezoid,  near  the  palm  ;  one  between  the  trapezoid  and 
os  magnum,  near  the  dorsum  ;  and  one  between  the  os  magnum  and  unciform,  much 
the  strongest,  connecting  the  palmar  halves  of  the  bones  at  the  distal  end.  None 
of  these  interrupt  the  communication  of  the  synovial  cavity  of  the  intracarpal  joint 
and  those  at  the  bases  of  the  metacarpals.  The  scaphoid,  semilunar,  and  cuneiform 
have  very  properly  been  compared  to  an  intra-articular  fibro-cartilage  or  meniscus, 
subdividing  a  joint.  No  muscle  of  the  forearm  is  inserted  into  them.  (The  flexor 
carpi  ulnaris,  which  has  the  pisiform  as  a  sesamoid  bone  in  its  tendon,  has  its  real 
termination  in  the  fifth  metacarpal. )  Hence  this  series  is  never  directly  moved,  but 
changes  position  under  the  pressure  of  the  distal  row,  which  is  pulled  against  it 
by  the  muscles  moving  it.  It  plays  an  important  part  in  the  movements  of  the 
joint. 


LIGAMENTS    OF    THE    WRIST    AND    METACARPUS. 


323 


The  bases  of  the  metacarpals,  except  the  thumb,  articulate  with  one  another  by 
the  lateral  facets,  and  just  below  these  joints  are  held  together  by  strong  interosseous 
ligaments  connecting  the  rough   depressions  below  the  bases.      The  fibres  of    the 


Intracarpal  join 
(between  scaphoid  and  os  magn 


Joint  between  trapezium  a 
first  metacarpal 


Ulna 

Inferior  radio-ulnar  joint 


I'riangular  fibro-cartilage 


Carpo-metacarpal  joint 


Carpal  synovial 


interosseous  ligament  from  the  trapezium  to  the  trapezoid  are  inseparable  from  some 
from  the  trapezium  to  the  second  metatarsal. 

A  common  description  will  best  serve  for  the  ligaments  connecting  the  forearm, 
the  first  row,  the  second  row,  and  the  bases  of  the  metacarpals  (Figs.  340,  341). 
The  simplest  conception  is  of  a  capsule  passing  from  the  forearm  to  the  metacarpus 
and  attached  to  the  intervening  bones.      It  is  much  strengthened  by  neighboring 


324 


HUMAN    ANATOMY. 


tendons  and  their  sheaths.  It  is  strong  at  the  sides  ;  weak  in  front  and  behind. 
The  stronger  bands  are  inextricably  blended  with  the  rest ;  that  on  the  outside,  the 
external  lateral  ligament,1  runs  from  the  radial  styloid  process  to  the  outer  side  of 
the  scaphoid,  thence  to  the  trapezium,  and  is  continuous  with  the  capsule  of  the 
carpo-metacarpal  joint  of  the  thumb.  The  internal  lateral  ligament'1  runs  from  the 
styloid  process  of  the  ulna  to  the  side  of  the  cuneiform,  and  to  the  pisiform,  thence 
to  the  narrow  internal  edge  of  the  unciform,  and  finally  to  the  fifth  metacarpal.  The 
dorsal  part  of  the  capsule  is  the  weakest,  but  is  much  strengthened  by  the  extensor 
tendons.  A  continuous  layer  passes  from  the  radius  and  ulna  to  the  first  row,  thence 
to  the  second,  and  thence  to  the  metacarpals.      The  general  direction  of  the  fibres  of 

Fig.  343. 

Radius   Interosseous  membr; 


Styloid  process 
Radio-carpal  ligament 


Ant.  inferior  radio-ulnar 
ligament 

J-Styloid  process 
Pisiform  ligament 


Tubercle  of  scaphoid 

Ridge  of  trapez 
Anterior  carpal  ligament 


Int.  lateral  ligament 
Unciform 

Tendon  of  ext. 


Outer  end  of.  ant.  annular  ligament 
Anterior  aspect  of  right  wrist-joint.    A  port 


of  the  anterior  annular  ligament  has 
the  flexor  carpi  radialis  opened. 


of  ant.  annular  ligament 
removed  and  the  canal  for 


the  proximal  part  is  transverse,  inclining  inward  from  the  styloid  process  of  the  radius 
and  the  scaphoid  to  the  cuneiform.  This  constitutes  the  dorsal  transverse  ligament, 
which  serves  to  hold  the  head  of  the  os  magnum  and  the  adjoining  part  of  the  unci- 
form in  the  socket  made  by  the  concavity  of  the  first  row.  It  has  no  definite  borders. 
Tolerably  distinct  bands  pass  to  the  bases  of  the  four  inner  metacarpals  ;  those  to 
the  second  and  third  are  tense  and  the  others  lax.  Various  accessory  bands  are 
often  found.  The  anterior  part  of  the  capsule  in  the  hollow  of  the  wrist  is  stronger  : 
it  is  reinforced  by  oblique  bands  converging  downward.  Many  of  these  fibres  are 
attached  to  the  narrow  palmar  prominence  of  the  os  magnum.  Pretty  distinct 
bundles  go  to  the  bases  of  the  metacarpals.  Very  small  disks  project  into  both  the 
radio-carpal  and  the  intracarpal  joints  from  the  dorsum,  which  are  hardly  seen  except 


1  Lig.  collaterale  carpi  radiale.     cLig.  collateral  carpi  ulnare. 


LIGAMENTS    OF   THE   WRIST   AND    METACARPUS. 


325 


Muscles  of  little  lingi 


Anterior  annular  ligament 

T_carpal  ligaments 

'on  of  flex,  carpi  rad. 


Os  magnum 
Dorsal  carpal  ligaments 

section  through   right  wrist  from  above.     The  flexo 
have  been  removed  from  the  canal  beneath  the  annular  ligann 


in  frozen  sections.     Their  broader  bases  are  attached  to  the  capsule,  and  the  free 
sharp  edges  end  in  the  joint  fitting  in  between  the  bones. 

The  pisiform  has  a  special  joint  on  the  palmar  side  of  the  cuneiform,  with  a  lax 
capsule.  This  is  strength- 
ened internally  by  a  bundle  Fig.  344. 
from  the  cuneiform  run- 
ning from  the  dorsal  to  the 
palmar  side.  Two  well- 
marked  bands  pass  down- 
ward from  it  on  the  latter 
aspect  ;  the  one  to  the  base 
of  the  fifth  metacarpal  is 
really  the  end  tendon  of 
the  flexor  carpi  ulnaris, 
the  other  passes  obliquely 
to  the  proximal  edge  of 
the  unciform  process. 

The  Anterior  An- 
nular Ligament. — This 
is  an  extremely  strong  structure,  bridging  the  hollow  of  the  wrist,  and  enclosing  a 
canal  through  which  pass  the  tendons  of  the  long  flexors  of  the  thumb  and  fingers 
and  the  median  nerve.  It  springs  internally  from  the  process  of  the  unciform  and 
from  the  pisiform,  the  latter  part  being  fused  with 
Fig.  345.  the  band  from  it  to  the  unciform.      It  is  attached 

externally  to  the  ridge  on  the  trapezium,  and  by  a 
deeper  process  to  the  tuberosity  of  the  scaphoid 
and  to  the  inner  side  of  the  front  surface  of  the 
trapezium,  thus  splitting  to  allow  the  passage  of 
the  tendon  of  the  flexor  carpi  radialis  through  a 
special  canal  in  the  groove  of  the  trapezium. 
Frozen  sections  through  the  wrist,  passing  through 
the  pisiform  (Fig.  344)  (but  not  those  through  the 
unciform),  show  deep  fibres  from  the  annular  liga- 
ment passing  down  under  the  canal  and  blending 
with  the  front  of  the  capsular  ligament  of  the 
wrist.  The  proximal  and  distal  borders  of  the 
ligament  are  somewhat  artificial,  as  it  is  connected 
with  the  fascia  of  the  forearm  and  with  the  palmar 
fascia,  besides  receiving  fibres  from  the  flexor  carpi 
ulnaris.  This  anterior  annular  ligament  holds  the 
sides  of  the  wrist  firmly  together  and  prevents  them 
from  spreading  when  pressure  is  applied  from 
above.  Its  fibres  mingle  with  the  origins  of  mus- 
cles of  the  thumb  and  of  the  little  finger. 

The  posterior  annular  ligament  is  but  a 
thickening  of  the  fascia  of  the  back  of  the  forearm, 
and  has  no  place  among  the  true  ligaments. 

The  Carpo-Metacarpal  Articulations. — 
Those  of   the  four  inner  fingers  have  been  partially 
described.     They  connect  with  the  general  articular 
cavity  of   the  wrist.       A   band  from  the   adjacent 
edges  of  the  os  magnum  and  unciform  to  those  of 
the  third  and  fourth  metacarpals   (Fig.  340)  does 
not    completely    interrupt    the    continuity   of   this 
cavity,   as  it  does  not  reach    the  dorsal   surface. 
The  carpus  and  metacarpus  are  connected  on  both 
front  and  back  by  bands  which  can  be  fairly  distinguished  from  the  capsule.    Trans- 
verse  bands    run  also  on  both    surfaces  from   the  base  of   one  metacarpal  to  the 
next.      The  opposed  sides  of  the  bases  are  partly  covered  with  articular  cartilage, 


Intra-articular  disk 

Semilunar 

Intra-articular  disk 


Third  metacarpal 


W 


Frozen  section  through  right  middle  finge 
the  hand  being  straight. 


326 


HUMAN   ANATOMY. 


Os  magnum  Third  metacarpal 

Same  as  Fig.  345,  the  hand  being  flexed. 


as  has  been  described.  Interosseous  metacarpal  ligaments  connect  their  sides  distally 
from  this.  These  complete  the  capsules,  which  are  imperfect  only  on  the  carpal 
side. 

The  articulation  of  the  thumb  (Fig.  342)  differs  from  the  others  in  being 
complete  in  itself.      It  is  a  saddle-shaped  joint.      The  hand  lying  supine,  the  long 

axis  of  the  joint  slants  dovvn- 
Fig.  346.  ward    and    inward.       In    this 

direction  the  trapezium  is  con- 
cave ;  at  right  angles  to  it  con- 
vex. The  joint  is  surrounded 
by  a  capsule,  which  is  strongest 
on  the  dorsal  and  palmar  sides, 
where  the  direction  of  the 
fibres  is  longitudinal  ;  it  is 
weak  at  the  outer  anterior  end, 
where  it  is  strengthened  by 
the  tendon  of  the  extensor  of 
the  metacarpal  bone. 

The  motions  are  flexion, 
extension,    adduction,    abduc- 
tion, and  circumduction.     Ro- 
tation   in   the   flexed    position 
may  be  possible  from  the    im- 
perfect  adaptation  of    the  ar- 
ticular surfaces,  but  can  hardly  be  of  practical  importance.      Flexion  is  limited   by 
the  locking  of  the  palmar  projection  of  the  metacarpal  against  the  trapezium  ;  the 
other  angular  motions  by  the  tension  of  the  ligaments. 

Movements  and  Mechanics  of  the  'Wrist  and  Carpo-Metacarpal 
Articulations. — It  is  convenient  in  studying  these  movements  to  imagine  that  the 
metacarpus  follows  the  motions  of  the  second  row  of  carpal  bones.  This  is  true  of 
the  index-  and  middle  fingers,  but  not  of  the  others.  The  motions  of  the  wrist  in 
the  widest  sense  are  flexion,  extension,  adduction,  abduction,  and  circumduction. 
The  joint  is  a  compound  one,  egg-shaped  above,  the  scaphoid,  semilunar,  and 
cuneiform  acting  as  a  meniscus.  The  motions  are  best  studied  by  removing  the 
skin  and  tendons  on  the  dorsal  aspect  and  inserting  long  pins  into  the  radius,  semi- 
lunar, and  os  magnum,  and,  for  some  purposes,  the  scaphoid.  The  Rontgen  rays 
have  been   useful  chiefly  as 

corroboratory  evidence.      In  Fig.  347. 

flexion  the  motion  begins  in 
the  upper  joint,  where  it  is 
most  extensive  ;  as  it  goes 
on  the  lower  takes  part.  In 
extension,  starting  with  the 
arm  straight,  more  than  half 
occurs  in  the  lower  joint. 
Adduction  (ulnar  flexion) 
(Fig.  348,  B),  owing  to  the 
lesser  prominence  of  the  ulna, 
is  more  free  than  abduction. 
The  meniscus  glides  towards 
the  radial  side,  and  in  so 
doing  assumes  the  relation  to 
the  radius  that  it  has  in 
extension.        The    scaphoid 

touches  the  radius  only  by  one  end,  so  that  its  long  axis  approaches  the  direction  of 
that  of  the  forearm,  and  the  semilunar  leaves  the  triangular  cartilage.  The  curve  of 
the  meniscus  broadens,  increasing  the  distance  between  the  ends  of  the  cuneiform 
and  the  scaphoid.  A  small  part  of  the  motion  occurs  in  the  mid-carpal  joint.  The 
unciform,  moving  with  the  os  magnum,  comes  nearer  to  the  semilunar.      The  space 


d  being  overextended. 


LIGAMENTS    OF   THE    WRIST    AND    METACARPUS. 


327 


between  the  neck  of  the  os  magnum  and  the  scaphoid  enlarges.  In  abduction  (radial 
flexion)  (Fig.  348,  A)  the  second  row  of  the  carpus  has  a  larger  share  in  the  motion 
than  in  adduction.  The  meniscus  moves  to  the  ulnar  side  and  is  flexed,  while  its 
ends  approach  each  other,  narrowing  the  arch.  The  lower  end  of  the  scaphoid  is 
crowded  against  the  os  magnum  and  the  proximal  end  of  the  unciform  recedes  from 
the  semilunar.  Lateral  motions  do  not  occur  when  the  wrist  is  either  strongly  flexed 
or  extended.  The  screw  surfaces  of  the  cuneiform  and  unciform  are  important 
factors  in  the  combination  of  antero-posterior  and  lateral  motions  ;  but  the  os  mag- 
num and  unciform,  which  move  together,  do  not  twist  in  the  socket  formed  by  the 
first  row  if  the  latter  be  fixed.  Circumduction  is  a  combination  of  the  preceding 
motions.  Though  the  meniscus  moves  as  a  whole,  the  scaphoid  is  less  closely 
attached  to  the  semilunar  than  is  the  cuneiform. 

Fig.  348. 


Reduced  tracings  from  skiagraphs,  showing  the 


flexion.' 


Flexion  is  limited  by  the  tension  of  the  dorsal  ligaments  ;  extension  in  the 
upper  joint  chiefly  by  the  lateral  ligaments,  in  the  lower  by  the  locking  of  the  bones 
of  the  meniscus  against  those  of  the  first  row.  The  anterior  fibres  of  the  capsule 
probably  assist.  Lateral  motion  is  checked  in  the  upper  joint  by  the  side  liga- 
ments ;  in  the  lower  joint  it  is  limited  chiefly  by  the  shape  of  the  bones.  The 
number  of  joints  between  the  carpal  bones  divide  the  force  of  shocks  transmitted 
through  the  hand. 

The  motions  of  the  carpo-metacarpal  joints  of  the  fingers  are  almost  wanting, 
except  for  the  ring  and  little  fingers.  In  both  these  the  motion  is  essentially  flexion, 
most  marked  in  the  latter,  and,  owing  to  the  dorsal  convexity  of  the  carpus,  tending 
to  oppose  the  little  finger  to  the  thumb. 

The  metacarpo-phalangeal  articulations  are  surrounded  by  a  rather  loose 
capsule,  which  is  inserted  into  both  bones  pretty  close  to  the  articular  cartilage. 
It  is  weakest  on  the  dorsum,  where  it  is  supported  by  the  extensor  tendons.      It 

1  In  tracings  from  X-ray  photographs  it  is  in  places  very  difficult  satisfactorily  to  outline  the 
separate  bones,  partly  because  the  contours  of  both  surfaces  as  well  as  of  thick  processes  are 
shown,  and  partly  because  some  bones  lie  in  front  of  others,  owing  to  the  palmar  concavity  of 
the  wrist.  The  greatest  difficulty  is  with  the  respective  outlines  of  the  trapezium  and  trapezoid. 
In  the  above  figures  the  outline  of  the  latter  is  indicated  in  dotted  lines.  This  confusion  is  of 
little  practical  importance,  since  the  drawings  are  to  illustrate  the  changes  of  position  between 
the  first  row  and  the  forearm  on  one  side  and  the  second  row  on  the  other. 


328 


HUMAN   ANATOMY. 


Glenoid  cartilage 


Insertion  of 
ext.  commun. 
digitorum 


Outer  side  of  right  forefinger.     The  metacarpo 
phalangeal  joint  is  opened. 


springs  from  little  hollows  on  the  sides  of  the  heads  of  the  metacarpals.  Longi- 
tudinal fibres  are  distinct  at  the  sides,  if  sought  for  from  within  the  joint.  The  cap- 
sule is  strengthened  on  the  palmar  surface  by  fibrous  or  fibro-cartilaginous  plates, — 
the  glenoid  cartilages, — which  form  the  beginnings  of  the  floor  of  the  canals  for  the 

flexor  tendons   (Fig.  350).      These  plates  are 
Fig.  349.  firmly  fastened  to  the  bases  of  the  phalanges, 

whose  motions  they  follow,  and  loosely  to  the 
metacarpals.  In  the  thumb  the  glenoid  plate 
amounts  to  little  or  nothing,  as  the  palmar 
aspect  of  the  joint  is  chiefly  covered  by  the  two 
sesamoid  bones,  which  are  firmly  held  near 
together  by  transverse  fibres.  When  sesamoids 
are  present  in  the  other  joints,  they  are  lost  in 
the  fibrous  tissue  at  the  sides  of  these  plates. 
The  glenoid  cartilages  of  the  four  inner  fingers 
are  attached  to  one  another  by  a  series  of  bands 
of  little  strength, — the  transverse  metacarpal 
ligament  (Fig.  351).       . 

The  articular  surface  of  the  metacarpal  is 
in  the  main  convex  and  that  of  the  phalanx 
concave.  They  do  not  make  a  true  ball-and- 
socket  joint,  for  the  long  axis  of  the  latter  is 
transverse  and  at  right  angles  to  that  of  the 
former,  which,  moreover,  is  much  broader  at 
its  palmar  than  at  its  dorsal  end.  As  the 
glenoid  disks  are  parts  of  the  floors  of  the 
canals  for  the  tendons  diverging  from  the  mid- 
dle of  the  wrist,  those  of  the  second  and  fifth  fingers  are  not  squarely  placed,  but 
incline  to  the  middle  of  the  hand. 

Movements. — When  the  finger  is  straight,  it  can  be  moved  laterally,  a  little 
backward,  and  flexed,  as  well  as  circumducted.  It  can,  on  the  dead  hand,  be 
slightly  rotated  ;  but  this  motion  does  not  occur  in  life.  When  it  is  fully  flexed, 
lateral  motion  is  impossible  owing  to  the  tenseness  of  the  capsule,  which  has  occurred 
in  two  ways, — partly  from  the  fact  that  in  flexion  the  phalanx  rests  on  the  broadest, 
instead  of  the  narrowest,  part  of  the  head,  and  because,  the  depressions  for  the 
origins  of  the  strongest  lateral 
parts    being    near   the    dorsum,  Fig.  350. 

these      are      Stretched     when      the  Transverse  metacarpal  ligament 

phalanx  has  travelled  round  the 
palmar  prominence  of  the  head. 

The  interphalangeal  ar- 
ticulations differ  from  the  pre- 
ceding by  the  peculiarities  of  the 
articular  ends  and  the  greater 
relative  strength  of  the  lateral 
parts  of  the  capsules.  The  gle- 
noid cartilages  are  small.  There 
is  no  lateral  motion.  They  are 
the  purest  hinge-joints  in  the 
body. 

The  Surface  Anatomy 
of  the  Wrist  and  Hand. — 
The  joint  between  the  forearm 
and  the  carpus  can  be  approxi- 
mately indicated  by  a  line  either 
on  the  back  or  the  front,  but  more  accurately  on  the  former,  starting  from  the 
head  of  the  ulna,  running  nearly  transversely,  but  with  a  slight  upward  bend, 
to  near  the  radial  styloid,  and  then  sweeping  downward  to  its  tip.  The  first  row  of 
carpal  bones  can  be  made  prominent  on  the  back  by  flexing  the  wrist.      The  hollow 


Metacarpals 


aspect  of  right  metacarpo-phala: 
flexor  tendons  opet 


d  cartilages 
geat  joints.     She: 


PRACTICAL    CONSIDERATIONS  :    THE    WRIST-JOINT, 


329 


Metacarpals 


on  the  dorsum  of  the  os  magnum  is  distinct,  and  some  indication  of  the  mid-carpal 
joint  may  be  felt  near  it.  ' '  Slightly  external  to  the  middle  of  the  hand  is  a  promi- 
nence, sometimes  indistinct,  but  often  very  well  marked,  formed  by  the  styloid 
process  on  the  base  of  the  third  metacarpal  bone  at  its  articulation  with  the  os 
magnum"  (Thane  and  Godlee).  On  the  palmar  side  the  pisiform  can  be  felt  just 
at  the  beginning  of  the  hypothenar  eminence.  When  the  hand  is  flexed  and  the 
muscles  relaxed,  it  is  easily  moved  from  side  to  side.  The  unciform  process  can 
be    indistinctly  felt    below  it. 

The  tubercle  of  the  scaphoid  Fig.  351. 

is  felt  with  difficulty  below 
and  internal  to  the  radial 
styloid,  and  at  the  beginning 
of  the  thenar  eminence  (the 
ridge  on  the  trapezium)  more 
clearly.  The  position  of  the 
annular  ligament  may  be  de- 
duced from  these  points,  and 
it  may  be  felt  by  pressure  on 
the  hand.  It  is  a  general  rule 
for  the  joints  between  the  meta- 
carpals and  the  phalanges,  as 
well  as  for  those  between  the 
latter,  that  the  more  distal 
moves  on  the  proximal,  and 
that,  therefore,  the  promi- 
nence of  the  knuckle  in  flexion 
is  made  by  the  head  of  the 
metacarpal.  All  the  meta- 
carpophalangeal joints  can  be 
made  out  from  the  dorsum. 
The  sesamoid  bones  of  the 
thumb  are  felt  with  difficulty. 

The  web  of  the  fingers  lies  about  thirteen  millimetres  distal  to  the  palmar  aspect  of 
the  metacarpo-phalangeal  joints.  That  of  the  index-finger  is  about  midway  between 
the  transverse  furrow  reaching  the  radial  side  of  the  hand  and  the  first  crease  on 
the  finger  ;  those  of  the  other  fingers  are  in  the  same  relation  to  the  second  furrow 
and  the  respective  creases.  The  interdigital  joints  are  slightly  distal  to  the  upper 
line  of  the  complicated  creases  of  the  first  joints  and  to  the  single  line  of  the  creases 
of  the  second  row. 


Sheath  for  flexor 
tendons  opened 


Transverse  metacarpal  liga 


Palmar  aspect  of  right  metacarpo-phalangeal  joints.     Sheath  for  flexor 
tendons  on  one  finger  opened  ;  on  adjacent  finger  still  closed. 


PRACTICAL   CONSIDERATIONS. 

The  Wrist-Joint.— The  radio-carpal  has  the  greatest  amount  of  motion  of 
the  three  rows  of  joints  that  intervene  between  the  metacarpus  and  the  forearm.  Its 
strength  is  not  derived  from  the  shallow  concavity  on  the  lower  end  of  the  radius, 
or  from  the  ligaments  which,  taken  together,  compose  the  capsule,  but  rather  from 
the  tough  fibrous  tissues  forming  the  sheaths  of  the  large  number  of  tendons  that 
pass  over  the  anterior  and  posterior  aspects  of  the  joint  and  are  closely  united  to 
the  bones.  It  escapes  frequent  injury,  also,  because  of  the  numerous  bones  that 
enter  into  the  carpus,  which  by  their  gliding  motion  one  upon  the  other  diffuse  force 
received  through  falls  upon  the  hand  ;  because  of  the  same  effect  produced  by  the 
movement  of  the  mid-carpal  joint  (intracarpal  of  Dwight),  which  takes  up  part  of  the 
force  in  overextension  of  the  hand  before  it  reaches  the  wrist  ;  and  because  of  the 
absence  of  any  long  rigid  lever  on  the  distal  side  of  the  joint. 

Dislocation  backward  is  by  far  the  most  common,  on  account  of  the  frequency 
of  falls  upon  the  hand.  The  diagnosis  from  Colles's  fracture  is  made  by  observing 
that  in  dislocation  :  (1)  the  anterior  swelling  is  nearer  the  ball  of  the  thumb  ;  (2) 
the  posterior  swelling  is  more  sharply  defined  at  its  upper  edge  ;  (3)  the  styloid 
process  of  the  radius  is  nearer  the  hand  than  that  of  the  ulna  ;   (4)  the  distance  from 


330  HUMAN    ANATOMY. 

it  to  the  head  of  the  metacarpal  bone  of  the  index-finger  is  shortened  ;  (5)  the 
antero-posterior  diameter  of  the  wrist  is  increased  ;  (6)  the  flexion  and  immobility 
of  the  wrist  are  greater. 

In  dislocation  forward  the  posterior  swelling  (the  sharp  border  of  the  radius 
and  ulna )  approaches  the  hand  ;  the  rounded  prominence  of  the  carpus  is  on  the 
front  of  the  wrist  ;  the  antero-posterior  diameter  is  increased  and  the  stylo-meta- 
carpal  measurement  is  lessened. 

Outward  (radial)  dislocation  of  the  wrist  is  resisted  by  the  contact  of  the 
scaphoid  with  the  styloid  process  of  the  radius  and  by  the  internal  lateral  ligament. 
Inward  dislocation  would  theoretically  be  easier,  as  there  is  no  bony  obstacle,  and 
as  adduction  may  be  effected  to  a  greater  extent  than  abduction,  and  with  greater 
power,  on  account  of  the  leverage  afforded  by  the  projection  of  the  cuneiform  and 
pisiform  bones  on  the  inner  side  of  the  wrist.  It  is  for  this  reason  that  the  hand 
commonly  assumes  the  position  of  adduction  and  the  little  finger  becomes  inclined 
towards  the  ulna  when,  from  disease  or  other  cause,  the  muscles  lose  the  influence 
of  volition  and  exercise  an  uncontrolled  sway  over  the  part  (Humphry).  Disloca- 
tion in  either  lateral  direction  is,  however,  very  rare. 

Spontaneo?is  subluxation  forward  is  a  condition  thought  to  be  associated  with 
hard  manual  labor  in  which  the  strong  anterior  ligament  becomes  stretched  and  the 
radial  side  of  the  carpus  is  displaced  forward  and  upward.  This  is  followed,  in 
accordance  with  a  general  law  of  growth  (page  104),  by  an  overgrowth  of  the 
posterior  portion  of  the  lower  end  of  the  radius,  from  which  the  normal  opposing 
pressure  of  the  carpus  has  been  removed.  The  lower  end  of  the  ulna  becomes 
unduly  prominent. 

Disease  of  the  wrist-joint  is  frequently  tuberculous,  but  may  be  septic  or  rheu- 
matic or  gonorrhceal  in  its  origin.  As  the  joint-cavity  does  not  include  the  epiphyseal 
lines  of  either  the  radius  or  ulna,  the  synovial  membrane  being  attached  to  the 
margins  of  the  epiphyses,  disease  and  injury  of  the  latter  do  not  of  necessity  involve  the 
joint.  The  circumstances  already  detailed  that  protect  the  joint  from  dislocation 
also  protect  it  from  sprains  and  lessen  the  frequency  of  traumatic  synovitis  and  of 
the  sequelae  of  traumatism. 

Disease  of  any  variety  once  established  is  apt  to  extend  to  the  various  synovial 
pouches  of  the  carpus  on  account  of  their  proximity,  to  involve  the  flexor  and  ex- 
tensor tendon  sheaths  for  the  same  reason,  and  to  result,  in  accordance  with  its 
character,  in  either  extensive  disorganization  or  much  limitation  of  motion.  The 
flexors  and  extensors  on  the  front  and  back  of  the  wrist  act  with  about  equal  force, 
and  therefore  but  little  displacement  occurs. 

The  swelling  usually  shows  itself  first  on  the  dorsum  through  the  thinner  pos- 
terior ligament,  the  joint  being  nearer  the  surface  on  that  aspect. 

Landmarks. — The  line  of  the  wrist-joint  is  convex  upward.  A  straight  line 
drawn  between  the  two  styloid  processes  is  oblique  downward  and  outward.  It 
unites  the  two  extremities  of  the  arc  which  represents  the  line  of  the  joint.  The 
highest  point  of  that  arc  is  a  half-inch  above  the  interstyloid  line. 

If  a  knife  were  introduced  horizontally  below  the  tip  of  the  styloid  process  of 
the  ulna,  it  would  open  the  wrist-joint  ;  below  the  styloid  of  the  radius,  it  would 
strike  the  scaphoid. 

The  remaining  landmarks  are  described  on  page  621. 

The  Joints  of  the  Carpus,  Metacarpus,  and  Phalanges. — As  the  inter- 
mediate ligaments  uniting  the  separate  bones  of  each  row  of  the  carpus  are  all  trans- 
verse, and  do  not  pass  from  one  row  to  another,  the  mid-carpal  (intracarpal)  joint 
permits  of  considerable  motion  in  both  flexion  and  extension.  It  undergoes  disloca- 
tion with  extreme  rarity,  and  usually  only  as  a  result  of  a  degree  of  force  sufficient 
to  stretch  or  tear  tendons  and  ligaments. 

Dislocation  of  the  second  row  of  the  carpus  forward  is  prevented  by  the 
manner  in  which  the  concave  surfaces  of  the  trapezium  and  trapezoid  rest  upon  the 
posterior  convex  facet  of  the  scaphoid,  as  well  as  by  the  undulating  manner  in 
which  the  side  of  the  unciform  is  disposed  with  regard  to  the  side  of  the  cuneiform. 
Displacement  backward  is  prevented  by  the  manner  in  which  the  round  head  of  the 
os  magnum  and  the  convex  posterior  and  upper  surface  of  the  unciform  are  let  into 


PRACTICAL    CONSIDERATIONS:    THE    CARPAL   JOINTS.        331 

the  hollow  formed  in  the  anterior  and  inferior  surfaces  of  the  bones  of  the  first  row 
(Humphry). 

The  joints  between  the  individual  bones  of  the  carpus  allow  of  but  little  motion, 
and  much  force  is  needed  to  produce  displacement  of  those  bones.  In  the  order  of 
frequency  the  os  magnum,  semilunar,  scaphoid,  pisiform,  trapezium,  trapezoid,  and 
unciform  have  been  reported  as  separately  dislocated.  It  is  interesting  to  note  in 
relation  to  the  order  of  frequency  that  the  middle  finger  is  the  longest,  and  is  the 
one  most  exposed  to  injury  and  to  force  applied  to  the  fingers  ;  its  metacarpal  bone 
is  the  longest  ;  it  articulates  directly  with  the  strongest  carpal  bone, — the  os 
magnum, — and  it,  in  its  turn,  with  the  semilunar,  which  unites  with  the  scaphoid  in 
connecting  the  hand  with  the  forearm.  In  reported  cases  the  pisiform  was  thought 
to  be  dislocated  secondarily  after  the  rupture  of  the  tendon  of  the  flexor  carpi 
ulnaris  below  the  bone. 

The  other  separate  carpal  luxations  have  but  little  anatomical  interest. 

Disease  of  the  mid-carpal  joint  is  usually  tuberculous,  and  is  apt  to  begin  in  or 
extend  to  the  os  magnum  because — 1.  It  is  the  bone  most  exposed  to  traumatism 
(vide  supra),  receiving  the  effects  of  injury  to  three  metacarpal  bones.  2.  The  joint 
participates  in  the  movements  of  flexion  and  extension  of  the  wrist,  which  are  partly- 
limited  by  the  portion  of  the  oblique  fibres  (both  radial  and  ulnar)  of  the  anterior 
annular  ligament  (page  325)  and  by  some  of  the  radial  fibres  of  the  weak  posterior 
ligament,  which  are  attached  to  the  os  magnum.  3.  The  slight  rotation  permitted  in 
the  mid-carpal  joint  is  around  a  vertical  axis  drawn  through  the  head  of  the  os  mag- 
num. A  very  slight  enlargement  of  the  bone  would  tend  to  pinch  and  bruise  the 
synovial  membrane  between  it  and  the  trapezoid,  those  two  being  more  closely  bound 
together  than  any  of  the  other  bones.  It  has  been  noticed  (Mundell)  that  the  point 
of  greatest  tenderness  in  these  cases  of  carpal  tuberculosis  was  in  a  line  between  the 
index-  and  middle  fingers,  corresponding  to  the  junction  of  the  os  magnum  and  the 
trapezoid.  Barwell  says  that  in  tuberculosis  of  the  wrist-joint  the  point  of  special 
tenderness  is  on  the  outer  side  of  the  extensor  indicis  tendon.  This  is  on  the  same 
line,  and,  in  cases  in  which  the  carpus  has  become  involved,  would  correspond  to 
the  same  point  of  junction. 

Dislocations  of  the  metacarpal  bones  from  the  carpus  usually  involve  single 
bones,  are  incomplete,  and  are  in  the  backward  direction.  The  wavy,  irregular  out- 
line of  the  distal  edge  of  the  carpus,  the  dovetailing  of  the  metacarpals  and  carpals 
by  means  of  the  alternating  convexities  and  concavities,  and  the  strength  of  the 
interosseous  and  transverse  metacarpal  ligaments  sufficiently  explain  the  infrequency 
of  dislocation  of  the  metacarpus  as  a  whole. 

Dislocations  of  the  metacarpo-phalangeal  and  interphalangeal  joints  amount  to 
"  nearly  thirty  per  cent,  of  all  dislocations"  (Stimson).  Backward  displacement  of 
the  proximal  phalanx  of  the  thumb  is  the  most  frequent  and  the  most  important. 
The  cause  is  usually  exaggerated  extension  of  the  phalanx,  which  carries  its  proximal 
end  up  onto  the  dorsum  of  the  metacarpal  bone  above  the  articular  surface.  The 
telation  to  the  muscles  of  the  thumb  is  so  important  that  the  luxation  will  be 
described  in  that  connection  (page  617). 

Dislocations  between  the  phalanges  usually  occur  at  tne  first  phalangeal  joint, 
and  in  the  backward  direction,  as  the  cause  is  commonly  a  fall  upon  the  palmar 
surface  of  the  finger  in  extension. 


THE   LOWER  EXTREMITY. 

The  Pelvic  Girdle. — This  consists  of  the  two  innominate  bones,  which  join 
each  other  in  front,  and  the  sacrum  behind.  While  the  thoracic  girdle  is  adapted 
to  freedom  of  motion,  the  pelvic  is  fitted  for  strength  and  support. 

The  study  of  the  innominate  bone  should  be  preceded  by  a  general  idea  of  the 
pelvis.  A  plane  between  the  promontory  of  the  sacrum  and  the  top  of  the  pubes 
divides  the  pelvis  into  the.  false  pelvis  above,  formed  chiefly  by  the  ilia,  and  the  trice 
pelvis  below.  The  latter  presents  the  sacrum  and  coccyx  behind,  the  arch  of  the 
pubes  in  front  and  below,  and  the  tuberosity  of  the  ischium  at  the  side.  Behind  this 
is  the  sacro-sciatic  notch,  much  reduced  by  ligaments.  On  the  sides  are  the  hip- 
joints,  and  towards  the  front  the  obturator  or  thyroid  foramen. 

THE    INNOMINATE    BONE. 

This1  consists  originally  of  the  ilium,  pubis,  and  ischium,  each  of  which  forms  a 
part  of  the  hip-joint,  but  which  fuse  so  completely  that  the  lines  of  union  are  not 
usually  to  be  seen  in  the  adult.  The  ilium  forms  the  upper  and  posterior  part  of  the 
bone,  the  pubis  the  front,  and  the  ischium  the  inferior.  The  two  latter  enclose  the 
obturator  foramen. 

The  Ilium. — The  ilium,2  a  plate  of  bone  forming  the  side  of  the  false  pelvis 
and  a  part  of  the  true,  may  be  said  to  have  four  borders.  The  superior  border, 
or  crest,3  very  much  the  longest,  is  convex  upward  and  outward.  It  connects  two 
tubercles,  the  anterior  and  posterior  superior  spines  of  the  ilium,  of  which  the  former 
is  a  knob  overhanging  the  concave  anterior  border  and  giving  attachment  to  Pou- 
part's  ligament  and  the  sartorius,  while  the  latter  is  less  prominent.  The  crest  has 
a  double  lateral  curve,  the  front  half  being  convex  externally  and  the  posterior  inter- 
nally. It  is  thicker  at  the  ends  than  in  the  middle,  and  presents  also  a  thickening 
near  the  middle  of  each  curve,  projecting  on  the  convex  side.  There  is  an  external 
lip,  from  the  whole  length  of  which  springs  the  fascia  lata  of  the  thigh,  an  internal 
'  lip,  and  an  intermediate  space.  The  anterior  border  is  short,  rounded,  and  con- 
cave, descending  to  the  anterior  inferior  spine,  a  knob  a  little  above  the  border  of 
the  acetabulum  giving  origin  to  the  straight  head  of  the  rectus  femoris  and  a  part  of 
the  ilio-femoral  band  of  the  capsule  of  the  hip-joint.  The  posterior  border,  very 
short  and  also  concave,  ends  in  the  posterior  inferior  spine,  an  ill-marked  angle  at 
the  bottom  of  the  surface  that  joins  the  sacrum.  The  inferior  border  consists 
anteriorly  of  an  attached  part,  which  meets  the  other  bones  in  the  acetabulum,  and 
behind  this  of  a  free  concave  part,  which  bounds  the  upper  part  of  the  great  sacro- 
sciatic  notch.*  The  ilium  might  also  be  described  as  consisting  of  an  expanded  por- 
tion, narrowing  below  to  a  stem,  which  joins  the  other  bones  in  the  acetabulum.  Its 
upper  part  follows  the  curves  of  the  crest. 

The  lateral  or  outer  surface  is  crossed  by  the  three  curved  or  gluteal  lines, 
convex  above  and  behind,  all  ending  at  or  near  the  sciatic  notch.  The  superior, 
much  the  strongest,  arises  from  the  crest  at  the  middle  of  its  second  curve  and  ends 
a  little  in  front  of  the  posterior  inferior  spine,  marking  off  a  raised  rough  surface 
behind  its  upper  two-thirds.  The  middle  begins  at  the  crest,  one  or  two  inches 
from  the  anterior  superior  spine,  and  ends  near  the  top  of  the  notch.  The  inferior, 
the  faintest,  starts  a  little  above  the  anterior  inferior  spine  and  is  lost  near  the 
■  front  of  the  notch.  The  three  gluteal  muscles,  maximus,  medius,  and  minimus, 
arise  respectively  behind  these  three  lines  in  the  order  given.  A  slight  groove 
for  the  reflected  tendon  of  the  rectus  femoris,  starting  at  the  anterior  inferior  spine, 
runs  backward  above  the  acetabulum. 

The  ventral  or  inner  surface  is  divided  into  an  upper  posterior  and 
a  lower  anterior  part  by  the  ilio-pectineal  line 5  in  front,  and  a  rough  border  con- 
tinuing it.      The  former  is  a  line  beginning  on  the  pubis  and  continued  across  the 

1  Os  coxae.     2  Os  Ilium.     3  Crista  iliaca.     4  Incisura  ischiadica  major.     5  Linea  arcnata. 


THE    INNOMINATE    BONE. 


333 


ilium  to  the  sacrum,  separating  the  true  pelvis  below  from  the  false  above.  All  of 
the  ilium  above  this  line,  except  a  small  part  posteriorly,  is  a  smooth,  shallow  con- 
cavity, the  iliac  fossa,1  which  contains  the  iliac  muscle.  It  ends  in  front  in  a  groove 
between  the  anterior  inferior  spine  of  the  ilium  and  the  ilio-pectineal  eminence,"1  a 
swelling  above  the  inner  part  of  the  acetabulum  made  by  both  the  ilium  and  the 
pubis  at  their  point  of  meeting.  The  bone  is  very  thin  at  the  middle  of  the  fossa. 
The  lower  half  of  the  inner  surface  of  the  ilium  may  be  subdivided  into  two  very 
dissimilar  parts.     The  front  one,  forming  the  wall  of  the  true  pelvis,  opposite  a  part 


Fig.  352. 


Middle  gluteal  1 


Latissimus  dor 


Semitendinosus  and  biceps 
Semimemb. 
Quadratus  femoris 


Cotyloid  notch 
tor  externus 


Adductor  magnus  ' 
Right  innominate  bone,  outer  aspect. 


of  the  socket  and  above  the  sciatic  notch,  is  smooth  ;  the  posterior  is  rough.  The 
latter  presents  anteriorly  the  rough  and  pitted  auricular  surface'1,  corresponding  to 
that  of  the  sacrum.  A  narrow  depression,  the  pre-articular  groove ;  bounds  thison  the 
smooth  surface,  receiving  the  fibres  of  the  anterior  sacro-iliac  ligament.  Behind  the 
auricular  surface  is  a  rough  area  of  a  different  character  with  an  elevation  at  or  below 
the  middle  of  the  preceding  surface.  This  area  serves  for  the  attachment  of  the 
strong  posterior  sacro-iliac  ligaments.  Still  farther  back  the  bone  has  a  smoother 
finish  where   it  gives   origin   to   the   erector  spina;.      The  ilium   has   several  large 


334 


HUMAN    ANATOMY. 


nutrient  foramina  ;  one  on  the  inside  of  the  lower  hind  part  of  the  iliac  fossa  runs 
forward,  one  or  two  on  the  outside  near  the  anterior  inferior  spine  run  backward, 
and  one  near  the  middle  of  the  second  curved  line  runs  downward. 

The  Pubis. — The  pubis1  (os pectinis)  has  a  flat  squarish  body,  which,  meeting 
its  fellow  at  the  symphysis,  forms  the  front  wall  of  the  pelvis,  and  two  rami,  the 
superior  joining  the  ilium  and  the  inferior  joining  the  ischium.  The  median  end  of 
the  body2  is  wholly  taken  up  by  a  rough  oval  area,  the  symphysis  pubis,  bearing  the 
fibro-cartilage  of  the  joint.      The  spine3  of  the  pubis  is  a  pointed  tubercle,  projecting 


Internal  lip 
Transversals 


Comp 
Attachment  of  crus  penis 

Ischio-cavfrnosns 
Trans 


Right  innominate  bone,  inner  aspect. 


forward  from  the  front  of  the  upper  border  of  the  bone  some  two  centimetres  irom 
the  symphysis,  to  which  Poupart's  ligament  is  attached.  A  ridge  runs  from  this 
obliquely  backward  and  inward  to  the  posterior  end  of  the  top  of  the  symphysis, 
which,  together  with  the  rough  surface  internal  to  it,  constitutes  the  crest.  The 
term  a?igle  is  applied  to  the  line  of  junction  of  this  surface  with  the  symphysis.  The 
superior  ramus  '  is  prismatic,  having  an  antero-superior,  an  inferior,  and  a  posterior 
side.      It  enlarges  as  it  runs  outward  to  form  a  part  of  the  socket.      The  ilio-pectineal 

1  Os  pubis.     -Corpus  ossis  pubis.     ^Tubereulum  pubicum.     4 Ramus  superior. 


THE    INNOMINATE    BONE. 


335 


line  starts  from  the  spine  and  runs  obliquely  backward  and  outward  to  the  ilium. 
The  triangular  antero-superior  side  of  the  ramus,  narrow  at  the  inner  end,  broad  at 
the  outer,  concave  from  side  to  side,  convex  from  before  backward,  is  bounded 
behind  by  the  ilio-pectineal  line,  in  front  by  the  obturator  crest,1  which  runs  from  the 

Fig.  354. 


Conjoined  tendon 
Gimbernat's  ligament 

Poupart's  ligament 

Conjoined  tendon 
Rectus  abdominis 


/ 

Pyramidalis 
Region  of  symphysis  pubis  fr 


Obturator  crest 
Spine  of  pubis 


spine  to  the  inner  border  of  the  acetabular  notch,  and  externally  by  a  swelling  at  the 
upper  inner  part  of  the  socket, — the  ilio-pectineal  eminence.  The  posterior  side,  broad 
at  the  inner  end  and  narrow  at  the  outer,  is  quite  smooth.  The  inferior  border  is 
marked  by  the  broad  obturator  groove 2  above  the  foramen,  passing  from  behind  for- 


Fig.  355. 


Epiphyseal  lamina  on  ilium J 


odules 
Epiphyseal  lamina  < 


Innominate  bone  at  about  fifteen  years. 


ward  and  inward  for  the  obturator  vessels  and  nerve.  The  inferior  ramus/  flat 
and  thin,  rough  in  front,  smooth  behind,  extends  backward  and  outward  to  join  the 
ramus  of  the  ischium.  It  is  constricted  just  above  the  point  of  union.  The  inner 
edge,  forming  part  of  the  pubic  arch,  is  somewhat  everted. 

1  Crista  obturatoria.     -  Sulcus  obturatorins.      '  Ramus  inferior. 


336 


HUMAN    ANATOMY. 


The  Ischium. — The  ischium/  the  thickest  and  most  solid  part  of  the  bone, 
consists  of  a  body,  chiefly  concerned  with  the  acetabulum,  a  tuberosity,  and  a  ramus. 
The  body,  continuous  above  with  the  ilium,  forms  the  front  of  the  great  sciatic  notch,2 
below  which  is  the  sharp  spine  of  the  ischium  pointing  backward  and  inward  for  the 
lesser  sacro-sciatic  ligament.  The  tuberosity 3  is  a  great  thickening  of  the  back  of 
the  lower  end  of  the  body  of  the  ischium  which  bears  the  weight  in  sitting.  It  is 
broad  above  and  behind,  narrowing  in  front  as  it  passes  into  the  ramus.  It  extends 
but  little  onto  the  inner  side  of  the  bone,  which  otherwise  is  smooth.  Its  inner  lip 
receives  the  great  sacro-sciatic  ligament  and  its  falciform  prolongation.  A  smooth 
surface  (in  life  coated  with  cartilage)  passes  from  the  inside  of  the  back  of  the 
bone  just  below  the  spine  and  above  the  tuberosity,  forming  the  lesser  sciatic  notch* 

occupied  by  the  tendon  of 
Fig.  356.  the  obturator  internus.      In 

front  of  this,  under  the  ace- 
tabulum and  above  the  tu- 
berosity, is  a  groove  for  a 
part  of  the  obturator  ex- 
ternus.  The  upper  part  of 
the  tuberosity  is  divided  into 
an  upper  and  front  area  for 
the  origin  of  the  semimem- 
branosus, and  one  behind 
and  below  it  for  the  semi- 
tendinosus  and  biceps.  Be- 
low these,  extending  onto 
the  ramus,  is  a  surface  for 
the  adductor  magnus.  The 
ramus 5  is  a  strip  of  bone 
running  forward  to  meet  the 
inferior  ramus  of  the  pubis. 
The  lower  edge,  forming 
the  margin  of  the  subpubic 
arch,  is  twisted  outward  and 
rough.  The  border  towards 
the  foramen  is  relatively 
sharp.  The  line  of  junction 
of  the  rami  of  the  ischium 
and  pubes  can  be  distin- 
guished by  the  greater 
breadth  of  the  former, 
hium  The  acetabulum,  the 

socket  for  the  hip,  is  a  deep 
hemispherical  cavity  with  a 
raised  border,  imperfect  be- 
low.      The    imaginary   axis 

Oblique  sagittal  section  of  right  innominate  bone  passing  through  bottom      Qj    ^q    cavity    runs    Upward, 

inward,  and  backward.  It 
is  formed  by  all  three  bones,  the  ischium  contributing  the  most  and  the  pubes  the 
least.  The  lines  of  union  are  sometimes  seen  on  the  smooth  posterior  surface  in 
the  adult.  The  cavity  is  only  in  part  articular.  In  shape  this  portion  may  be  com- 
pared to  a  horseshoe  beaten  concave  and  fitted  into  the  cavity  with  the  two  ends 
pointing  downward,  enclosing  a  non-articular  cavity  at  a  somewhat  deeper  level, 
which  extends  more  than  half-way  up  the  back  of  the  socket.  The  bone  at  the 
bottom  of  the  cavity  is  very  thin.  The  articular  strip  is  broadest  above  and  behind 
the  middle  and  narrowest  in  front.  Of  the  two  ends  of  this  articular  strip  the 
posterior  is  the  more  prominent,  overhanging  a  groove  leading  into_  the  non- 
articular  hollow  from  below.  The  front  one'has  no  corresponding  projection.  The 
border  of  the  acetabulum  is  formed  by  the  convexity  of  this  horseshoe-shaped  strip, 
and  consequently  is  wanting  below.      The  interruption  is  the  cotyloid  notch. 6     The 


1  Os  iscliii.     -1 


ischiadica  major.     3  Tuber  iscliii. 


J  Ramus  inferior.     6  Inci; 


JOINTS    AND    LIGAMENTS   OF    THE    PELVIS.  337 

border  rises  from  the  surface  of  the  bone  distinctly  below  and  to  a  less  degree  behind 
and  above. 

The  thyroid  or  obturator  foramen '  is  a  large  oval  opening,  with  the  larger 
end  above  and  the  long  axis  running  downward  and  outward,  bounded  by  the 
pubis  and  ischium.  A  little  tubercle,  seen  best  from  the  inner  side,  marks  the 
upper  limit  of  the  ischium.  Above  is  the  obturator  groove  under  the  ramus  of  the 
pubis.      It  is  closed  by  a  membrane,  except  under  the  groove. 

Structure. — The  innominate  bone  is,  as  a  whole,  very  strong.  The  two  thin 
places  are  in  the  middle  of  the  ilium  and  of  the  cotyloid  cavity.  It  is  very  thick 
round  the  joint  wherever  pressure  may  be  transmitted  through  the  head  of  the 
femur.  Sections  show  radiating  trabeculse  from  the  socket  connected  by  concentric 
lines.  The  bone  is  very  thick  in  a  line  from  the  socket  to  the  outer  expansion  of 
the  iliac  crest,  which  runs  nearly  vertically  in  the  upright  position.  It  is  very 
strong  also  at  and  behind  the  auricular  surface. 

Development. — A  centre  for  the  ilium  appears  early  in  the  third  fcetal 
month  above  the  acetabulum  and  spreads  quickly  through  the  upper  part  of  the 
bone.  One  for  the  ischium  appears  below  the  socket,  usually  before  the  end  of  the 
same  month.  One  for  the  pubis  comes  decidedly  later  in  the  iliac  ramus.  It  is 
said  to  appear  from  the  fourth  to  the  fifth  month,  but  it  may  not  be  present  till  the 
sixth.  At  birth  there  is  still  much  cartilage  around  and  between  the  bony  expan- 
sions from  these  centres.  The  rami  of  the  pubis  and  ischium  unite  at  about  eight 
years  or  earlier,  but  the  suture  may  be  visible  on  the. inside  at  eighteen.  Ossifica- 
tion commences  by  several  centres  in  the  Y-shaped  cartilage  separating  the  bones  in 


Fig.  357- 


Ossification  of  innominate  bone.  A,  at  third  fcetal  month  ;  B,  at  birth  ;  C,  during  first  year;  D,  at  six  years  ; 
E,  at  about  fifteen  years,  a,  chief  centre  for  ilium;  b,  chief  centre  for  ischium  ;  c,  for  pubis;  d,  for  tuberosity  of 
ischium  ;  e,  for  iliac  crest ;  f,  for  anterior  inferior  spine. 

the  socket  at  an  uncertain  date,  probably  before  ten  years.  One  of  these  centres, 
much  larger  than  the  rest,  the  os  acetabuli,  persists  at  the  front  of  the  cavity  be- 
tween the  pubis  and  ilium  till  perhaps  fifteen,  when  union  has  made  much  progress 
between  the  various  parts  of  the  acetabulum.  The  lines  of  junction  may  be  seen  on 
the  inside  of  seventeen  or  eighteen,  that  between  the  pubis  and  ischium  persisting 
longest.  Secondary  centres  come  about  puberty  for  the  crest  of  the  ilium,  the  an- 
terior inferior  iliac  spine,  the  symphysis  pubis,  and  the  ischial  tuberosity.  They 
are  fused  at  twenty,  excepting,  perhaps,  that  for  the  crest  of  the  ilium,  the  union  of 
which  may  be  delayed  ;  the  suture  marking  its  presence  is  one  of  the  last  in  the 
body  to  disappear. 


JOINTS    AND    LIGAMENTS    OF   THE    PELVIS. 
These  may  be  divided  into  ( 1 )  those  connecting  the  ilium  with  the  sacrum  and 
last  lumbar  vertebra,  (2)  those  connecting  the  pubic  bones  at  the  symphysis,  and  (3) 
the  ligaments  forming  the  lateral  walls, — the  sacro-sciatic  ligaments  and  the  obtu- 
rator membrane. 

1  Foramen  obturatum. 


338 


HUMAN    ANATOMY. 


THE   SACRO-ILIAC   ARTICULATION. 

The  sacro-iliac  articulation,  often  improperly  called  the  sacro-iliac  synchondrosis, 
partakes  of  the  nature  of  both  a  true  and  a  half-joint.  The  opposed  surfaces  of 
the  sacrum  and  ilium  vary  greatly  in  shape.  The  sacrum  is  broader  in  front  than 
behind,  so  that  the  line  of  the  joint  slants  inward  as  well  as  backward  ;  but  occasion- 


Poslerior  sacro-iliac  ligament 


Sacro-iliac  joint 


Anterior  sacro-iliac  ligament 

tal  section  through  right  sacro-iliac  joint. 


ally  in  some  part  it  is  a  little  broader  behind  than  in  front.  Often  there  is  an  out- 
ward swelling  between  the  borders,  so  that  a  part  of  the  sacrum  is  received  into  a 
hollow  in  the  ilium,  and  a  transverse  cut  of  the  joint  shows  a  sinuous  line.  Perhaps 
quite  as  often  the  ilium  projects  into  the  sacrum.  In  any  case,  as  a  rule,  there  is  a 
certain  amount  of  interlocking.  The  opposed  surfaces  are  covered  with  cartilage. 
The  layer  on  the  sacrum,  from  one  to  two  millimetres  thick,  is  at  least  twice  as  thick 
as  the  other,  and,  though  generally  reckoned  fibro-cartilage,  has  much  the  appear- 
ance of  hyaline.  The  two  are  sepa- 
Fig.  359.  rated  by  a  synovial  cavity,  which 

)-iumbar  ligament  is  enclosed  by  the  sacro-iliac  liga- 

ments. The  size  of  this  cavity  is 
very  uncertain.  It  may  extend 
backward  beyond  the  auricular 
surfaces,  occupying  on  the  ilium 
a  part  of  the  space  usually  serving 
for  the  origin  of  the  posterior 
sacro-iliac  ligaments,  or  it  may  be 
encroached  upon  by  fibres.  Some- 
times, before  old  age,  the  joint  is 
replaced  by  bone. 

The  fibres  around  the  joint 
are  severally  named  according  to 
position.  The  posterior  sacro- 
iliac ligament  (Fig.  358)  is  very 
important.  It  comprises  many 
layers  of  strong  fibres,  filling  up  the  depths  of  the  cleft  between  the  sacrum  and  the 
overhanging  ilium,  extending  from  the  rough  area  on  the  latter  behind  the  auricular 
surface  to  the  back  of  the  lateral  masses  of  the  sacrum,  nearly  or  quite  to  the  pos- 
terior sacral  foramina  below  the  three  upper  sacral  vertebrae.      Those  of  both  sides 


THE   SYMPHYSIS    PUBIS. 


339 


resist  any  tendency  of  the  weight  of  the  body  to  force  the  sacrum  forward.  A  rather 
distinct  superficial  band,  the  oblique  sacro-iliac  ligament '  (Fig.  362),  passes 
from  the  posterior  superior  iliac  spine  to  the  second  and  third  sacral  vertebrae. 
Anterior  and  superior  fibres  are  spread  about  the  joint,  and  require  no  special 
description.      Some  of  them  go  to  the  pre-auricular  sulcus  of  the  ilium. 

The  ilio-lumbar  ligament2  (Fig.  359)  is  a  triangular  band  of  strong  fibres 
diverging  from  the  apex  and  the  front  surface  of  the  transverse  process  of  the  last 
lumbar  vertebra  to  the  top  of  the  crest  of  the  ilium  opposite  to  it  and  to  the  an- 
terior surface,  where  it  mingles  with  the  anterior  sacro-iliac  fibres.  A  more  or  less 
distinct  bundle  of  diverging  fibres  to  the  top  of  the  sacrum  near  the  joint  with  the 
ilium  is  the  sacro-lumbar  ligament  (Fig.  359). 

THE  SYMPHYSIS  PUBIS. 
The  symphysis  pubis  is  generally  a  typical  half-joint,  the  fibro-cartilage  coating 
the  opposed  pubic  surfaces  being  very  dense  and  the  central  cavity  small.  In 
section  it  appears  as  a  linear  cleft  nearer  the  back  than  the  front.  Sometimes, 
however,  especially  in  women,  a  part  of  the  surfaces  is  coated  with  hyaline  cartilage. 
The  total  breadth  of  the  soft  parts  (greater  in  woman  than  in  man)  rarely  exceeds 
five  millimetres.      The  cartilages  are  ensheathed  in  fibres,  the  deeper  parts  of  which 


Fig.  360. 


Fig.  361. 


Fibro-cartilage 


ament 
The  symphysis  pubis,  anterior  surface 


Inferior 
pubic  ligan 
Frontal  section  through  the  symphysis  pubis. 


are  inseparable  from  them  :  those  above  and  behind  are  of  little  consequence. 
The  anterior  ones  are  in  several  layers,  being  in  part  composed  of  fibres  from  the 
aponeurosis  of  the  external  oblique  and  of  fibres  of  origin  of  the  rectus.  They  are 
in  the  main  transverse,  but  those  from  the  obliques  run  downward  and  inward, 
sometimes  making  a  distinct  decussation.  The  inferior  or  subpubic  fibres  are  col- 
lected into  a  dense  transverse  band,  bounding  by  the  lower  side  the  pubic  arch  and 
being  joined  by  the  upper  to  the  fibro-cartilage. 

THE   SACRO-SCIATIC    LIGAMENTS. 

These  are  two  layers  of  fibres  passing  from  the  sides  of  the  sacrum  to  the 
ischium  and  forming  a  partial  wall  for  the  pelvis  at  the  sacro-sciatic  notch,  where  the 
bony  walls  are  wanting. 

The  great  or  posterior  sacro-sciatic  ligament3  (Fig.  362)  is  external  to 
the  lesser,  which  it  conceals  to  a  large  extent.  It  arises  from  the  outer  surface  of 
the  pelvis,  beginning  at  the  inferior  posterior  spine  of  the  ilium,  where  its  fibres 
mingle  with  those  of  the  posterior  sacro-iliacs,  then  from  the  posterior  edge  of  the 
border  of  the  three  lower  pieces  of  the  sacrum  and  from  one  or  two  of  the  coccyx. 
From  this  broad  origin  it  narrows  as  it  passes  forward,  and  at  the  same  time  twists 
so  that  the  outer  surface  becomes  the  inferior  as  it  is  inserted  into  the  under  side  of 
the  tuberosity  of  the  ischium.      As  it  reaches  the  tuberosity  the  fibres  at  its  inner 

1  Lig.  sacrolliacum  posterius  longum.     -  Lig.  iliolumbale.     3  Lie.  sacrotuberosum. 


34© 


Posterior  superior  spine  of  ilium 


Oblique  sacro-il 
ligament 


Supraspinous  ligament 


Sacro-coccygeal  ligament 

Tip  of  coccy 


HUMAN   ANATOMY. 
Fig.  362. 


Lesser  sacro-sciatii 

ligament 
Spine  of  ischium 


Origin  of  biceps- 

-Tuberosity  of  ischii 
External  surface  of  the  sacro-sciatic  ligaments. 


Fig.  363. 


Fifth  lumbar  vertebra 


Obturator  canal 


Auricular  surface 
Non-articular  surface 


Lesser  sacro-sciatic 
ligament 


Obturator  membrane 


Falciform  process  of  great  sacro-sciatic/ 
ligament 


Internal  surface  of  the  sacro-sciatic  ligaments,  showing  the  falciform  continuation  of  the  great. 


THE    PELVIS   AS    A   WHOLE. 


341 


border  become  raised  from  the  rest  and  are  inserted  into  the  inner  border  of  the 
ramus  of  the  ischium,  from  which  they  rise  in  a  fold,  the  falciform  ligament,  within 
the  pelvis,  continuous  with  the  obturator  fascia.  The  ligament  at  its  insertion  into 
the  tuberosity  is  continuous  with  the  fibres  of  origin  of  the  biceps. 

The  lesser  or  anterior  sacro-sciatic  ligament '  (Fig.  363),  much  the  smaller, 
is  situated  internally  to  the  great,  springing  from  the  edge  of  the  sacrum  below 
the  junction  with  the  ilium  and  from  the  side  of  the  upper  part  of  the  coccyx,  being 
more  or  less  continuous  with  the  interior  surface  of  the  great.  It  narrows  to  its 
insertion  into  the  spine  of  the  ischium. 

The  great  sacro-sciatic  foramen2  (F'ig.  362)  is  bounded  above  by  the  ilium, 
in  front  by  the  ilium  and  the  ischium,  behind  by  the  great  ligament,  and  below  by 
the  lesser.  It  transmits  the  pyriformis  muscle,  the  gluteal,  sciatic,  and  internal  pudic 
vessels  and  nerves,  and  the  nerves  to  the  obturator  internus  and  quadratus  femoris. 

The  lesser  sacro-sciatic  foramen3  (Fig.  362)  is  bounded  in  front  by  the 
body  of  the  ischium,  above  by  the  lesser  ligament,  and  below  and  behind  by  the 
oblique  border  of  the  great.  Through  it  pass  the  obturator  internus  muscle,  the 
internal  pudic  vessels  and  nerve,  and  the  nerve  to  the  obturator  internus. 

The  obturator  membrane4  (Fig.  363)  is  attached  to  the  margin  of  the  fora- 
men of  that  name,  which  it  completely  closes,  except  for  a  small  space  at  the  top  of 
the  groove  under  the  ramus  of  the  pubis.  Sometimes  there  are  perforations.  The 
attachment  at  the  inner  side  is  directly  to  the  sharp  edge  of  the  rami  of  the  pubis 
and  ischium.      At  the  outer  border  it  passes  into  the  periosteum  lining  the  pelvis. 

THE  PELVIS  AS  A  WHOLE. 
The  promontory  of  the  sacrum  and  the  ilio-pectineal  line  separate  the  true  pelvis' 
below  from  the  false6  above.      The  latter  is  bounded  by  the  lower  lumbar  vertebrae 

Fig.  364. 


The  pelvis  from  behind. 

and  by  the  flaring  ilia.      The  true  pelvis  is  bounded  by  the  sacrum  and  coccyx  behind, 
by  the  bodies  and  symphysis  of  the  pubis  in  front,  and  by  the  sacro-sciatic  ligaments, 

-  Forara.  ischiadicum    majus.     3  Foram.  isch.   minus.     4  Memhrana   obturatoria.     ''Pelvis    minor. 


342 


HUMAN   ANATOMY. 


the  ischia,  part  of  the  ilia,  and  the  pubic  rami  and  obturator  membrane  at  the  sides 
and  front.  The  plane  just  described  as  separating  the  true  and  false  pelvis  is  the 
plane  of  the  inlet1  of  the  latter.  Its  greatest  individual  variations  are  due  to  the 
greater  or  less  projection  forward  of  the  sacral  promontory.  The  outlet'1  is  bounded 
behind  by  the  coccyx,  from  the  sides  of  which  the  great  sacro-sciatic  ligaments 
pass  to  the  ischial  tuberosities,  thence  by  the  rami  of  the  ischia  and  pubes,  forming 
the  pubic  arch,  and  by  the  subpubic  ligament  below  the  symphysis.  It  is  evident 
that  these  planes  converge  in  front  and  that  the  axis  of  the  pelvis  (an  imaginary  line 
in  the  centre,  perpendicular  to  an  indefinite  number  of  intermediate  planes)  must  be 
a  curved  one. 

The  Position  of  the  Pelvis. — The  plane  of  the  inlet  of  the  pelvis  is  inclined 
to  the  horizon  about  6o°  when  the  body  is  upright.  This  inclination  varies  accord- 
ing to  the  figure  and  to  the  individual  peculiarities  of  the  pelvis  itself.  Hermann 
von  Meyer's  conjugata  vera,  a  line  from  the  top  of  the  symphysis  to  the  line  usually 


Fig.  365. 


Male  pelvis  from  before 


found  in  the  third  sacral  vertebra,  runs  at  about  300  with  the  horizon.  This  is  a  more 
trustworthy  angle  than  that  of  the  plane  of  the  inlet  ;  but  even  this  is  not  constant. 
It  is  better  to  try  to  determine  the  proper  position  of  every  pelvis  for  itself  than  to 
attempt  to  make  all  conform  to  one  angle,  which  for  these  reasons  is  impossible. 
The  two  borders  of  the  cotyloid  notch  should  be  put  in  the  same  level,  which  will 
bring  the  anterior  superior  spines  of  the  ilia  into  the  same  vertical  plane  as  the  spines 
of  the  pubes.  The  tip  of  the  coccyx  should  be  at  about  the  level  of  the  top  of  the 
symphysis  ;  owing  to  the  many  variations  of  the  former,  however,  its  position  must 
be  uncertain.  The  height  of  the  promontory  above  the  symphysis  is  about  9.5 
centimetres  (3^  inches)  in  man  and  about  10.5  centimetres  (4/4  inches)  in 
woman. 

The  diameters  of  the  true  pelvis  of  woman  are  of  great  practical  importance  in 
midwifery.  The  standards  are  the  antero-posterior,  the  transverse,  and  the  oblique 
(the  latter  from  the  sacro-iliac  joint  to  the  acetabulum  of  the  opposite  side)  measured 
at  the  inlet,  the  outlet,  and  at  an  intermediate  plane. 


1  Apertura  pelvis  supe: 


-  Apertura  pelvis  inferu 


THE    PELVIS    AS    A    WHOLE. 


343 


DIAMETERS   OF  THE  TRUE    PELVIS. 


Male. 

Female. 

Inlet. 
Cm.  (Inches). 

Cavity. 
Cm.  (Inches). 

Outlet. 
Cm.  (Inches). 

Inlet. 
Cm.  (Inches). 

Cavity. 
Cm.  (Inches) 

Outlet. 
Cm.  (Inches). 

Anteroposterior 
Transverse  .    .    . 
Oblique     .    .    .    . 

IO.25  U) 
12-75  (5) 

12.00  (4X) 

"■5  UX) 

12.0  (4X) 
"•5  14X) 

8.25  (3X) 
9°°  13X) 
10.25  (4) 

IO.25  (4) 
13-25  (5%) 
12.75  (5) 

12.75  (5) 

12-75  (5) 

13-25  (5'A) 

".5(4X0 

12.0  (4?/) 

II.5UX) 

The  index  of  the  pelvis,  of  interest  in  anthropology,  is  the  proportion  of  the 
antero-posterior  diameter  to  the  transverse  at  the  pelvic  inlet,  the  latter  being  100. 
This  index  is  80  for  European  males  and  78  for  females  (Verneau).  In  the  lower 
races  it  is  considerably  higher,  implying  a  narrower  pelvis.  Pelves  with  indices 
below  90  are  platypellic,  with  indices  from  go  to  95  mesatipellic,  and  above  95 
doliclwpellic. 

Another  index  to  show  the  relative  depth  of  the  pelvis  is  the  proportion  of  the 
breadth  between  the  most  distant  points  of  the  iliac  crests  to  the  height  from  the 
top  of  the  crest  to  the  tuberosity  of  the  ischium,  the  latter  being  100.     According  to 


Fig.  366. 


le  pelvis  from  befor 


Topinard,  this  index  is  126.6  for  male  and  136.9  for  female  Europeans.      It  is  lower 
in  the  lower  races,  showing  that  in  them  the  pelvis  is  relatively  deeper. 

Differences  due  to  Sex. — The  sexual  differences  of  the  pelvis  are  far  more 
marked  than  those  of  any  other  part  of  the  skeleton.  The  male  pelvis  is  deeper  and 
narrower,  the  female  shorter  and  broader.  It  is  to  be  noted  that  the  greater  breadth 
of  the  female  applies  essentially  to  the  true  pelvis.  At  the  inlet  this  is  both  relatively 
and  absolutely  broader  in  woman.  The  male  promontory  is  more  projecting.  The 
most  characteristic  feature  is  the  pubic  arch,  which  is  of  a  much  greater  angle  in 
woman.  According  to  Verneau,  it  is  from  380  to  770  in  the  male,  with  an  average 
of  6o°  ;  and  from  56°  to  1040  in  the  female,  with  an  average  of  74°.  The  symphy- 
sis is  shorter  in  woman,  and  the  borders  of  the  arch  probably  more  everted.     The 


344  HUMAN    ANATOMY. 

greater  lightness  of  the  female  skeleton  shows  particularly  in  this  part  qf  the  pelvis. 
It  is  owing  to  the  greater  divergence  of  the  rami  that  the  front  of  the  obturator  fora- 
men is  straighter  in  the  female,  making  it  more  triangular  and  less  oval  than  in  the 
male.  The  spines  of  the  ischia  are  farther  apart  in  woman.  According  to  Verneau,1 
those  in  man  are  rarely  more  than  10.7  centimetres  (4^  inches)  apart,  and  often 
less  than  9  centimetres  (3%  inches)  ;  while  in  woman  they  are  often  more  than  10.7 
centimetres  apart,  and  never  less  than  9  centimetres.  He  states  also  that  in  man 
the  spines  of  the  ischia  are  sometimes  internal  to  the  posterior  inferior  spines  of  the 
ilia,  but  that  they  are  always  external  to  them  in  woman.  The  sacro-sciatic  notch 
is  usually  wider  and  less  deep  in  the  female.  There  is  much  irregularity  in  regard 
to  the  false  pelvis.  The  anterior  superior  spines  of  the  ilia  are  farther  apart  in 
woman.  It  does  not  follow  that  the  same  is  true  of  the  most  lateral  points  of  the 
crests  of  the  ilia.  In  powerful  male  bodies  they  are  farther  apart  than  in  female 
ones.  The  vertical  depth  of  the  false  as  well  as  of  the  true  pelvis  is  greater  in 
the  male.  As  has  been  stated  elsewhere,  the  male  sacrum  is  the  more  regularly 
curved. 

Development. — The  pelvis  of  the  foetus  and  infant  is  strikingly  small,  and 
continues  relatively  so  for  some  years.  The  peculiarity  of  its  shape  is  largely  due 
to  the  sacrum.  Even  at  birth  there  is  but  a  very  rudimentary  promontory,  and  the 
sacrum  is  straight  or  nearly  so.  Consequently  the  pelvis  is  funnel-shaped,  being 
largest  above.  The  height  is  greater  in  proportion  to  the  breadth  than  later.  It 
has  been  shown  by  Fehling2  and  Thompson3  that  the  sex  of  the  pelvis  may  be 
recognized  by  the  usual  signs  as  early  as  the  fourth  month  of  fcetal  life.  In  the 
fcetus  the  transverse  diameter  of  the  inlet  exceeds  the  conjugate,  especially  in  the 
female.  The  average  subpubic  angle  of  the  fcetus  is  500  in  males  and  about  68°  in 
females.  In  the  latter  the  ischial  spines  are  farther  apart  and  the  sacro-sciatic 
notches  wider.  Although  after  birth  the  promontory  becomes  stronger,  it  has  a 
tendency  to  be  double  partly  above  and  partly  below  the  first  sacral.  This  is  cor- 
rected at  a  very  indefinite  time  in  early  childhood.  Of  the  details  of  the  changes  by 
which  the  great  difference  between  the  sexes  is  brought  about  we  know  very  little. 
Waldeyer*  states  that  the  external  measurements  of  the  female  pelvis  surpass  those 
of  the  male  from  the  eleventh  to  the  fifteenth  year,  but  particularly  from  the  four- 
teenth to  the  sixteenth.      The  growth  of  the  male  pelvis  is  more  regular. 

Mechanics  of  the  Pelvis. — The  mechanical  function  of  the  human  pelvis, 
apart  from  protecting  the  viscera,  is  chiefly  to  support  the  spine,  whether  sitting  or 
standing.  The  interruptions  of  the  bony  girdle  at  the  symphysis  and  the  sacro-iliac 
joints  add  to  the  strength  of  the  structure  and  break  shocks.  There  is,  however,  a 
real  motion  at  the  sacro-iliac  joints  which,  slight  under  ordinary  circumstances,  is  of 
importance  in  childbirth.  The  weight  of  the  body  transmitted  through  the  spine 
may  theoretically  be  said  to  tend  to  force  the  sacrum  down  between  the  innominate 
bones  and  also  to  carry  the  promontory  downward  and  forward  into  the  pelvis,  the 
sacrum  rotating  on  a  transverse  axis  passing  through  the  second  piece  at  the  sacral 
canal.  Motion  in  the  former  direction  does  not  occur,  but  in  the  latter  it  may  to 
a  slight  degree.5  With  the  body  lying  on  the  back,  if  the  legs  are  strongly  flexed 
and  pressed  against  the  abdomen,  the  pelvis  rotates  on  the  sacrum,  the  symphysis 
rises,  and  the  antero-posterior  diameter  of  the  inlet  is  lessened  ;  if  the  legs  be  strongly 
extended  by  being  brought  down  over  the  edge  of  the  table,  this  diameter  is  in- 
creased, the  difference  between  the  extremes  being  one  centimetre.  At  the  end 
of  pregnancy  these  joints,  as  well  as  that  of  the  symphysis,  are  loosened  so  as  to 
admit  of  more  motion,  which  is  no  doubt  of  real  value.  Assuming,  as  at  first,  the 
pelvis  to  be  the  fixed  part,  the  tendency  to  displacement  of  the  sacrum  in  either  of 
these  directions  is  resisted  by  the  posterior  sacro-iliac  ligaments.  The  sacrum  is  not 
really  a  keystone,  for  the  anterior  surface  is  broader  than  the  posterior,  except  in 
some  few  sections. 

1  Le  bassin  dans  les  sexes  et  dans  les  race,  Paris,  1S70. 

2  Arch,  fiir  Gynakol.,  Bd.  x.,  1S76. 

3  Journal  of  Anatomy  and  Physiology,  vol.  xxxiii.,  1899. 
*  Das  Becken,  Bonn,  1S99. 

5  G.  Klein  :  Zeitschrift  fiir  Geburtshiilfe  und  Gynakol.,  Bd.  xxi.,  1891. 


PRACTICAL   CONSIDERATIONS  :    THE   PELVIS.  345 

The  weight  in  standing  is  transmitted  to  the  thigh  bones,  in  sitting  to  the 
tuberosities  of  the  ischia  ;  in  both  cases  the  parts  of  the  pelvis  running  to  the  pubes 
act  as  "ties"  to  prevent  the  spreading  of  the  arch.  The  circumference  of  the 
acetabulum  is  of  strong  bone  to  resist  pressure  from  the  joint,  and  in  the  erect 
position  a  strong  part  runs  from  the  socket  directly  upward  to  the  crest  of  the 
ilium.  The  thinness  of  the  bottom  of  the  acetabulum  in  all  ages  and  the  meeting 
there  in  childhood  of  the  three  bones  make  it  a  weak  place. 

Surface  Anatomy. — The  anterior  superior  spine  of  the  ilium  is  easily  felt, 
but  care  must  be  taken  not  to  mistake  for  it  a  swelling  of  the  crest  an  inch  or  more 
behind  it.  To  make  sure  of  this  spine  as  a  point  for  measurements,  the  finger 
should  be  carried  over  it  from  the  crest  and  then  back  again  till  it  is  arrested  by 
the  overhanging  spine.  The  anterior  inferior  spine  cannot  be  felt.  The  outer 
lip  of  the  crest  of  the  ilium  can  easily  be  followed  to  the  posterior  superior  spine, 
which  is  marked  by  a  dimple,  and  is  on  a  level  with  the  middle  of  the  sacro-sciatic 
joint.  The  tuberosity  of  the  ischium  is  readily  felt,  but  it  is  too  thickly  covered  for 
details  to  be  recognized.  A  line  drawn  from  the  posterior  superior  spine  to  the  outer 
part  of  the  tuberosity  of  the  ischium  will  cross  the  inferior  spine  of  the  ilium  and  the 
spine  of  the  ischium.  A  line  from  the  same  point  to  the  top  of  the  greater  trochanter 
will  pass  very  close  to  the  highest  point  of  the  great  sacro-sciatic  notch.  The  sym- 
physis of  the  pubes  and  most  of  the  borders  of  the  pubic  arch  can  be  felt.  The 
spine  of  the  pubes  can  be  recognized,  but  usually  not  without  some  difficulty.  It 
may  be  necessary  to  feel  for  it  beneath  the  skin  by  invaginating  the  scrotum  or 
labium.  In  woman  it  is  nearly  2.5  centimetres  from  the  median  line  ;  in  man  some- 
what less. 

PRACTICAL   CONSIDERATIONS. 

Failure  of  development  in  the  separate  bones  of  the  pelvis  produces  certain 
well-known  deformities.  In  the  sacrum,  the  arch  of  the  upper  sacral  vertebra, 
which  is  formed  later  than  the  others  and  varies  notably  in  thickness,  is  frequently 
incomplete,  which  results  in  the  very  common  occurrence  of  spina  bifida  at  this 
region  (page  1051). 

When  the  pelvic  girdle  is  incomplete  anteriorly,  there  is  an  interval  of  several 
inches  between  the  pubic  bones,  and  all  the  bones  of  the  pelvis  are  changed  some- 
what in  shape  and  direction.  The  defect  may  be  associated  with  exstrophy  of  the 
bladder,  epispadias  in  the  male,  split  clitoris  in  the  female,  double  inguinal  hernia, 
ectopia  of  the  testicles,  and  sometimes  ventral  hernia  from  separation  of  the  recti 
muscles. 

Deformities  of  the  pelvis  have  even  more  interest  to  the  obstetrician  than  to 
the  surgeon.  The  usual  differences  between  the  male  and  female  pelves  are  some- 
times absent,  constituting  an  abnormality,  though  perhaps  stopping  short  of  actual 
deformity.  The  so-called  masculine  pelvis,  for  example,  is  characterized  by  a 
diminution  in  the  breadth  of  the  pubic  arch  and  an  increase  in  the  pubic  angle. 

The  female  pelvis,  as  compared  with  that  of  the  male,  is  lighter,  less  compact, 
more  expanded,  shorter  in  vertical  depth,  broader  at  the  inlet,  with  a  greater  angle 
in  its  pubic  arch,  a  lesser  curve  in  the  sacrum,  and  a  greater  separation  between  the 
ischial  spines,  and  is  thus  more  perfectly  adapted  to  the  purposes  of  parturition. 

The  chief  deformities  due  to  faulty  development  may  be  at  least  enumerated 
here  on  account  of  their  importance  in  this  relation.  In  the  simple  flat  pelvis  the 
antero-posterior  diameter  is  contracted  by  the  advancement  of  the  sacrum  in  a  down- 
ward and  forward  direction  between  the  iliac  bones.  The  equally  contracted  pelvis 
resembles  a  miniature  normal  female  pelvis  with  other  peculiarities  that  approxi- 
mate it  to  the  infantile  type.  The  funnel-shaped  pelvis  is  contracted  transversely 
at  the  outlet  in  both  the  antero-posterior  and  transverse  diameters,  the  cavity  is 
deeper,  the  sacrum  is  narrow  and  less  curved.  These  peculiarities  are  found  in 
very  early  life,  and  hence  this  is  also  known  as  the  fatal  pelvis.  The  obliquely  con- 
tracted pelvis  is  due  to  imperfect  development  of  the  ala  on  one  side  of  the  sacrum, 
which  is  associated  with  many  secondary  deformities,  among  them  a  lack  of  curva- 
ture of  the  innominate  bone  on  the  affected  side.  The  transversely  contracted  pelvis 
in  which  both  sacral  ala;  are  undeveloped  is  rarest  of  all  contracted  pelves.      The 


346  HUMAN    ANATOMY. 

functional  importance  of  these  pelvic  contractions  should  be  studied  in  connection 
with  the  mechanism  of  labor. 

The  pelvis  may  be  deformed  as  a  result  of  morbid  conditions  in  other  parts  of 
the  skeleton.  A  lateral  curvature  of  the  lumbar  spine  to  the  left  may  thus  be  ac- 
companied not  only  by  the  usual  compensatory  dorsal  curve  to  the  right,  but  by  a 
curve  in  the  latter  direction  in  the  sacrum,  the  upper  margin  of  which  will  be  higher 
on  the  right  side  than  on  the  left.  Even  the  corresponding  rotation  will  take  place, 
and  the  ala  on  the  concave  side  will  be  rotated  forward,  as  are  the  transverse  pro- 
cesses of  the  dorsal  vertebra?. 

Irregularity  in  the  lengths  of  the  lower  limbs  may  produce  a  similar  curve  in 
the  sacrum. 

In  both  cases  the  whole  pelvis  will  be  tilted  laterally,  the  iliac  crest  being 
higher  on  the  convex  side  of  the  sacrum.  It  has  been  suggested  that  this  continu- 
ation of  a  spinal  curvature  into  the  sacrum  is  sometimes  a  cause,  and  not  a  result,  of 
the  obliquely  contracted  pelvis  described  above,  with  which  it  is  often  associated, 
but  which  is  regarded  as  congenital  in  its  origin. 

Humphry,  after  describing  the  ring  of  the  pelvis  as  heart-shaped,  and  calling 
attention  to  the  wide  arch  with  a  flattened  or  depressed  centre  of  the  upper  or 
posterior  half,  and  the  greater  curve  with  flattening  at  the  ilio-pectineal  regions 
of  the  lower  or  anterior  half,  says,  "  It  results  from  this  configuration  of  the  pel- 
vic ring  that  it  is  weakest  at  five  points, — viz.,  at  or  a  little  external  to  both  sacro- 
iliac synchondroses,  at  the  symphysis  pubis,  and  midway  between  the  latter  and 
the  acetabula.  Hence  fractures,  whether  from  falls,  blows,  or  foreign  bodies  pass- 
ing over  the  pelvis,  are  most  frequent  at  these  points." 

In  studying  the  clinical  effects  of  traumatism  applied  to  the  pelvis,  it  is  helpful, 
however,  to  consider  it  with  reference  to  its  various  functions, — i.e.,  {a)  as  inter- 
posed between  the  vertebral  column  and  the  lower  extremities  as  a  weight-carrier  ; 
(Jj)  as  a  means  of  providing  for  the  motions  of  the  trunk  upon  the  lower  limbs  and 
of  affording  advantageous  points  of  attachment  for  the  muscles  which  effect  that 
motion  ;  (c)  as  a  bony  protection  or  receptacle  for  the  abdominal  and  pelvic 
viscera. 

i.  If  it  is  viewed  as  a  bony  ring  between  the  spine  and  the  thigh  bones, 
intended  to  transmit  the  weight  of  the  head  and  trunk  from  the  former  to  the  latter, 
the  pelvis  may  be  regarded  as  made  up  of  two  main  arches, — one  which  is  in  use 
when  standing,  the  other  when  sitting.  The  sacrum  is  the  point  of  union  of  both 
these  arches, — one,  the  femoro-sacral  (Morris),  extending  from  the  acetabulum 
through  the  strong  thickened  mass  of  bone  indicated  on  the  inner  surface  by  the 
upper  third  of  the  ilio-pectineal  line  to  the  sacrum  through  the  sacro-iliac  joint  ;  the 
other,  the  ischio-sacral,  extending  from  the  tuber  ischii  through  the  strong  bony 
mass  at  the  posterior  edge  of  the  acetabulum  to  the  same  point.  These  are  the 
essential  weight-carrying  portions  of  the  pelvis. 

Although  Cunningham  says  that,  as  the  sacrum  narrows  towards  its  dorsal  sur- 
face, and  is  really  suspended  from  the  iliac  bones  by  the  posterior  sacro-iliac  liga- 
ments, it  cannot  be  considered  as  the  keystone  of  an  arch,  yet  the  union  between 
the  sacrum  and  the  ilia  is  so  close  by  virtue  of  these  powerful  ligaments,  of  those 
upon  the  anterior  aspect,  and  of  the  reciprocal  irregularities  of  the  sacro-iliac  articu- 
lar surfaces,  that  the  objection,  though  technically  correct,  is  clinically  a  theoretical 
one  only.  In  describing  the  mechanics  of  the  remaining  or  accessory  portions  of 
the  pelvis,  regarded  as  a  weight-carrier,  Morris  calls  attention  to  the  fact  that  when 
much  strength  is  essential  in  an  arch,  it  is  often  prolonged  into  a  ring  so  as  to  form 
a  counterarch, — i.e.,  the  ends  of  the  arch  are  tied  together  to  prevent  them  from 
starting  outward.  A  portion  of  any  weight  to  be  carried  by  the  arch  is  thus  con- 
veyed to  the  centre  of  the  counterarch,  and  borne  in  what  is  called  the  sine  of  the 
arch.  In  the  pelvis  ' '  the  body  and  horizontal  rami  of  the  pubes  form  the  tie  or 
counterarch  of  the  femoro-sacral,  and  the  united  rami  of  the  pubes  and  ischium  the 
tie  of  the  ischio-sacral  arch."  The  ties  of  both  arches  are  united  in  front  at  the 
symphysis  pubis,  which,  like  the  sacrum,  is  common  to  both  arches. 

It  can  now  be  understood  how  and  why  a  fall  upon  the  feet,  or  a  crush  either 
antero-posterior  or  lateral  in  direction,  though  such  dissimilar  accidents,  are  so  apt  to 


PRACTICAL    CONSIDERATIONS  :    THE    PELVIS. 


347 


Fig 


produce  fracture  of  the  horizontal  or  the  descending  ramus  of  the  pubes,  the  ramus 
of  the  ischium,  or  of  the  ilia  external  to  the  sacro-iliac  junction. 

If  the  accident  has  been  a  fall  upon  the  feet,  the  injury  will  probably  be  confined 
to  the  acetabulum  or  to  the  pubes.  In  young  subjects  the  acetabulum  may  be  sep- 
arated into  its  three  anatomical  components  (Fig.  355),  or  a  portion  of  the  rim  may 
be  broken  off,  or  in  rare  cases  the  head  of  the  femur  may  be  driven  through  into  the 
pelvic  cavity. 

If  the  traumatism  has  been  a  crush  in  the  antero-posterior  direction,  the  pubes 
will  probably  first  fracture  ;  if  the  force  is  continued,  the  protection  afforded  by  the 
"  tie  arch"  having  been  withdrawn,  the  pressure  comes  upon  the  main  arches,  which 
tend  to  open  out.  A  portion  of  one  of  these  arches  may  then  give  way,  and  a  sec- 
ond fracture  may  occur  through  the  ilium  into  the  sacro-sciatic  notch,  or  vertically 
through  the  sacrum  itself.  More  commonly,  however,  the  anterior  sacro-sciatic 
ligaments  give  way  and  a  certain  amount  of  disjunction  of  that  joint  occurs.  Even 
if  the  crushing  force  is  applied  laterally,  it  is  usual  to  find  the  pubes  again  fractured 
from  indirect  violence.  If  the  application  of  the  force  is  continued,  the  strain  comes 
upon  the  posterior  sacro-iliac 
ligaments,  which  may  rupture, 
but  are  more  likely  to  with- 
stand the  violence,  which  then 
may  result  in  the  tearing  away 
of  a  portion  of  the  bone  into 
which  the  ligament  is  inserted. 

The  pubic  fracture  is  dis- 
coverable by  the  usual  means. 
The  vertical  fracture  of  the 
ilium  or  the  disjunction  of  the 
sacro-iliac  synchondrosis  an- 
teriorly should  be  suspected 
if  there  is  pain  in  the  region 
supplied  by  the  superior  glu- 
teal, the  lumbo-sacral,  the 
upper  sacral  nerves,  or  the 
obturator, — i.e. ,  in  the  sacral 
region,  the  buttock,  the  back  or  inner  part  of  the  thigh,  or  the  knee, — on  account 
of  the  relation  of  these  nerves  to  the  anterior  surface  of  the  joint. 

Marked  ecchymosis,  swelling,  and  tenderness  over  the  sacro-iliac  regions  pos- 
teriorly indicate  tearing  of  the  posterior  ligaments  or  the  fracture  by  arrachemeni 
that  has  been  described. 

In  all  these  cases  the  gravity  of  the  injury  depends  upon  the  presence  or  absence 
of  visceral  complications.  If  a  double  vertical  fracture  exists,  extending  through 
the  rami  of  the  pubes  and  ischium  in  front  and  through  the  ilium  near  the  sacro- 
iliac junction  posteriorly,  it  is  obvious  that  there  will  be  one  large  fragment  of  the 
pelvis  more  or  less  movable,  to  which  the  femur  on  that  side  is  connected.  This 
condition  may  be  associated  with  upward  displacement  of  the  fragment,  carrying  the 
femur  with  it,  and  it  may  give  rise  to  a  mistaken  diagnosis  of  fracture  of  the  neck  of 
the  femur.  It  should  be  remembered,  as  Tillaux  has  pointed  out,  that  in  the  pelvic 
lesion  the  relation  of  the  greater  trochanter  to  the  anterior  superior  iliac  spine  is 
normal,  and  the  real  length  of  the  limb  on  the  affected  side  is  the  same  as  that  on 
the  sound  side. 

2.  Other  fractures,  as  those  through  the  lateral  expansions  of  the  ilia,  and 
epiphyseal  separations  involving  the  pelvis,  have  relation  more  especially  to  its 
function  as  affording  a  means  of  moving  the  trunk  upon  the  lower  limbs.  The 
epiphyses  chiefly  separated  are  those  of  (a)  the  iliac  crest,  (&)  the  anterior  superior 
spine,  (c)  the  posterior  superior  spine,  and  (</)  the  anterior  inferior  spine. 

The  first  three  of  these  are  often  united  in  one  long  epiphysis,  but  portions  of 
this  may  be  detached  separately  by  muscular  action  or  by  direct  violence.  Cases  of 
separation  of  the  anterior  superior  spine  by  the  action  of  the  abdominal  muscles 
and  by  that  of  the  sartorius  have  been  reported. 


348  HUMAN    ANATOMY. 

The  anterior  inferior  spine,  which  is  peculiar  to  the  human  pelvis,  and  affords 
a  slight  leverage  which  partly  enables  the  rectus  femoris  to  overcome  the  disadvan- 
tage of  the  erect  position,  has  been  torn  off  in  the  act  of  running. 

Although  the  ischial  tuberosities  are  subjected  to  enormous  pull  from  the  pow- 
erful hamstring  muscles,  as  in  the  act  of  suddenly  straightening  the  trunk  from  a 
bending  position  (when  these  bones  project  far  behind  the  axial  plane  and  thus  offer 
better  leverage),  their  epiphyseal  disjunction  or  their  fracture  from  muscular  action 
is  practically  unknown.  From  direct  violence  both  of  these  lesions  occur,  but  with 
great  rarity. 

3.  Considered  in  relation  to  the  abdominal  and  thoracic  viscera,  the  injuries 
and  diseases  of  the  bones  of  the  pelvis  are  of  great  importance.  Fractures  of  the 
false  pelvis  have  been  followed  by  fatal  wound  of  the  small  intestine.  Fractures 
running  through  the  brim  of  the  pelvis  have  been  associated  with  hemorrhage  from 
the  iliac  vessels  ;  fractures  of  the  pubis  and  ischium  have  constantly  been  compli- 
cated by  wounds  of  the  urethra  and  bladder,  and  even  of  the  rectum.  The  pos- 
sibility of  these  complications  should  never  be  forgotten.  The  obvious  ana- 
tomical reasons  for  their  occurrence  will  be  recurred  to  when  these  viscera  are 
described. 

Disease  of  the  pelvic  bones,  like  their  deformities,  is  of  chief  importance  in  its 
relation  to  parturition. 

In  rickets  the  shape  of  the  pelvis  is  modified  through  the  medium  of  the  super- 
imposed weight  of  the  trunk  and  through  the  pull  of  muscles  resisted  by  the  inter- 
osseous ligaments. 

The  weight  of  the  body,  aided  by  the  psoas  muscles,  tends  to  press  the  sacrum 
downward  and  forward  between  the  iliac  bones  and  to  rotate  the  upper  end  forward 
on  a  transverse  axis.  The  sacro-sciatic  and  sacro-iliac  ligaments  resist  this  force, 
which  thus  results  in  thrusting  the  promontory  of  the  sacrum  towards  the  pubes  and 
in  increasing  the  sacro-vertebral  angle,  or  making  a  sharp  bend  in  it,  often  at  the 
junction  of  the  fourth  and  fifth  sacral  vertebrae.  The  sacro-iliac  ligaments  convey 
this  movement  to  the  posterior  superior  spinous  processes,  which,  advancing  some- 
what forward  and  inward,  would  tend  to  throw  the  anterior  half  of  the  innominate 
bones  outward.  These  are  held,  however,  firmly  at  the  symphysis  and — much  less 
effectively — by  Poupart's  ligament.  The  ilia  are  thus  thrown  outward  and  back- 
ward, so  that  the  distance  between  their  spines  may  be  equal  to  or  greater  than 
that  between  the  summits  of  the  crests.  As  a  further  result  of  these  combined 
forces  pushing  the  innominate  bones  forward  from  behind  and  holding  them  in  place 
in  front,  they  are  abnormally  curved,  as  a  bow  is  bent  between  one's  hand  and  the 
ground  (Hirst).  This  bending  of  the  ilia,  together  with  the  pull  of  the  external 
rotators  of  the  thigh  (increased  by  the  usual  bowing  of  the  femurs),  carries  the 
tuberosities  of  the  ischium  outward,  so  that  they  diverge  like  a  monkey's,  flattening 
and  widening  the  pubic  arch  and  increasing  the  transverse  diameter.  The  weight  of 
the  trunk  on  the  summit  of  the  sacrum  is  so  much  the  most  effective  and  continuous 
force  applied  as  the  growing  child  walks  or  stands  that  the  whole  pelvis  is  tilted 
forward  on  its  transverse  axis,  the  inclination  of  the  superior  strait  being  increased 
and  the  external  genitals  displaced  backward. 

In  osteomalacia  the  bones  are  much  softer  than  in  rickets  and  the  mechanism 
of  the  pelvic  deformity  is  simpler.  The  sacrum  yields  under  the  pressure  of  the 
body  weight,  and  becomes  acutely  angulated  and  driven  forward  and  downward  into 
the  pelvis  ;  the  ischia  and  pubes  are  pushed  inward  and  backward  by  the  force 
transmitted  through  the  acetabula,  the  pubic  angle  is  greatly  increased,  and  the 
pelvis  assumes  an  irregularly  triangular  or  ' '  triradiate' '  shape. 

The  rhachitic  and  osteomalacic  pelves  may  approximate  each  other  in  shape,  but 
are  usually  distinct. 

Exostoses  of  the  pelvis  are  usually  found  over  one  of  the  joints,  or  at  points  of 
muscular  or  fascial  attachment,  as  along  the  pubic  crests  where  the  iliac  fascia  is 
inserted. 

Enchondroma  is  relatively  common  in  the  pelvis,  and  other  growths  occasion- 
ally originate  there. 

Congenital  tumors  are  often  found  in  the  sacro-coccygeal  region.      Their  shape 


PRACTICAL    CONSIDERATIONS  :    THE    PELVIS. 


349 


Fig.  36S. 


sometimes  resembles  the  tail  of  lower  animals.  They  frequently  arise  from  the  an- 
terior part  of  the  coccyx  behind  the  rectum,  and  contain  muscular,  bony,  epithelial, 
or  cartilaginous  elements  in  an  imperfect  and  fragmentary  condition.  When  a  third 
lower  limb  is  found  connected  with  this  part  of  the  pelvis,  the  condition  is  known  as 
"  tripodism. " 

In  some  of  the  reported  cases  of  parasitic  fcetuses  the  point  of  junction  has  been 
in  this  region. 

Sinuses  over  the  sacrum  and  coccyx  occasionally  persist  after  abscesses  following 
blows  or  falls.  If  the  pus  has  travelled  in  a  lateral  direction,  the  suppurating  track 
will  be  found  to  lead  to  the  region  of  origin  of  the  tendinous  sacral  and  coccygeal 
fibres  of  the  gluteus  maximus.  The  probe  may  catch  against  these  points  and  give 
a  kind  of  grating  sound,  like  that  due  to  bare  or  dead  bone.  The  continuance  of  the 
sinuses  is  not  the  result  of  necrosis,  but  is  due  to  the  unyielding  character  of  the 
tendinous  structures.  This  prevents  apposition  and  union  of  the  sinus  walls  until 
tension  has  been  removed. 

Landmarks. — Anteriorly,  the  anterior  superior  spinous  process  of  the  ilium  is 
most  easily  recognized  as  a  prominence  at  the  outer  end  of  the  fold  of  the  groin. 
In  very  fat  subjects  its  situation  is  indicated  by  an  oblique,  slightly  elongated  de- 
pression. It  is  a  little  above  the  level  of  the  promontory  of  the  sacrum.  Running 
upward  and  outward  and  curving  backward  in  an  irregularly  S-shaped  line  is  the 
iliac  crest.  In  muscular  subjects  the  fibres  of  the 
external  oblique  overhang  the  crest,  causing  a  crease 
in  the  soft  parts  which  lie  between  these  fibres  and 
those  of  the  gluteus  medius  a  little  below  the  level  of 
the  crest  ;  it  is  known  as  the  "  iliac  furrow."  It  is  less 
marked  where  the  crest  passes  below  the  tendinous 
portion  of  the  erector  spina;. 

The  posterior  superior  spine  is  not  so  prominent 
as  the  anterior,  but  may  easily  be  found  by  following 
the  crest  to  its  posterior  termination.  Its  position  is 
indicated  by  a  slight  depression  on  the  surface  on  a 
level  with  the  second  sacral  spine  and  behind  the 
middle  of  the  sacro-iliac  joint.  The  third  sacral  spine 
lies  just  below  in  the  mid-line,  and  indicates  the  level 
to  which  the  membranes  of  the  cord  enclose  a  distinct 
space,  and,  therefore,  the  lowest  point  at  which  cerebro- 
spinal fluid  can  be  found.  The  curve  of  the  sacrum 
and  coccyx  may  be  traced  to  the  tip  of  the  latter. 

The  ischial  tuberosities  are  easily  felt  when  the 
hip  is  flexed  and  the  fibres  of  the  gluteus  maximus  are 
thus  withdrawn.  A  bursa  is  interposed  between  them 
and  the  layer  of  subcutaneous  fat  which  covers  them. 
They  can  be  felt,  but  with  more  difficulty,  through 
the  gluteus  fibres  when  the  hip  is  in  extension.  Five 
centimetres  (two  inches)  below  the  posterior  superior 
spine,  on  a  line  drawn  from  it  to  the  outer  part  of  the  tuberosity,  lies  the  pos- 
terior inferior  spine,  and  five  centimetres  (two  inches)  lower  still  the  spine  of  the 
ischium.  The  sciatic  and  internal  pubic  arteries  emerge  at  the  junction  of  the 
lower  and  middle  thirds  of  this  line.  The  pudic  artery  crosses  the  spine  of  the 
ischium  on  its  way  between  the  great  and  small  sacro-sciatic  foramina.  A  line, 
called  Nelaton's,  drawn  from  the  anterior  superior  spine  to  the  prominence  of  the 
tuber  touches  the  top  of  the  greater  trochanter  and  crosses  the  centre  of  the  ace- 
tabulum (Fig.  368). 

The  pubic  symphysis  may  be'  felt  indistinctly  and  the  horizontal  rami  more 
easily. 

The  pubic  spine  is  readily  felt  in  thin  persons.  In  fat  males  it  may  be  most 
easily  found  by  invaginating  the  scrotum.  In  either  sex  the  tendon  of  the  adductor 
longus — made  tense  by  abducting  the  thigh — is  an  unfailing  guide  to  it.  It  lies  on 
the  level  of  the  upper  edge  of  the  greater  trochanter.      It  is  just  below  and  a  little 


ng  Nelaton's  line. 


35Q 


HUMAN    ANATOMY. 


internal  to  the  external  abdominal  ring,  and  is  on  the  outer  side  of  an  inguinal 
hernia  and  on  the  inner  side  of  a  femoral  hernia. 

With  the  finger  in  the  rectum,  the  tip  of  the  coccyx  and  a  little  of  the  anterior 
curve  can  be  felt,  as  well  as  the  small  sacro-sciatic  ligaments  leading  to  the  ischial 
spines.  Laterally,  the  tuberosities  of  the  ischium,  the  smooth  bone  forming  the 
wall  of  the  pelvis,  and  the  structures  back  of  the  acetabulum  (page  1693)  can  be 
palpated. 

Through  the  vagina  the  configuration  of  the  subpubic  arch  can  be  felt,  also 
the  pelvic  wall  to .  either  side.  If  the  promontory  of  the  sacrum  can  be  touched, 
it  indicates  deformity  accompanied  by  diminution  of  the  antero-posterior  pelvic 
diameter. 

With  the  hand  in  the  rectum,  the  brim  of  the  pelvis,  the  arch  of  the  pubes,  the 
sacral  promontory,  the  curve  of  the  sacrum  and  coccyx,  the  spines  of  the  ischium, 
and  the  margins  of  the  sacro-ischiatic  foramina  can  be  palpated. 

The  Joints  of  the  Pelvis. — The  sacro-lumbar  joint  has  a  wider  range  of 
movement  than  any  of  the  joints  between  the  contiguous  dorsal  or  lumbar  verte- 
brae. This  is  due  to  the  greater  thickness  of  the  intervertebral  substance,  permit- 
ting flexion  and  extension,  and  to  the  fact  that  the  inferior  articulating  processes 
point  more  antero-posteriorly  than  those  of  the  other  lumbar  vertebrae,  thus  admit- 
ting of  more  rotation  on  a  vertical  axis. 

In  spite  of  this,  on  account  of  the  strength  of  the  ligaments  of  the  joint,  and 
more  particularly  for  the  reasons  that  tend  to  localize  the  effect  of  traumatism  some- 
what higher  in  the  spine  (page  145),  sprain  and  disease  of  the  sacro-lumbar  articu- 
lation are  both  uncommon. 

Overextension  of  the  joint  is  brought  about  if  with  the  body  prone  the  shoul- 
ders are  raised  while  the  hips  are  fixed.  Pain  thus  produced  suggests  lumbar  or 
sacro-lumbar  disease,  as  in  sacro-iliac  disease  this  movement  is  often  painless.  • 

The  sacro-coccygeal  joint  is  not  infrequently  strained  by  falls  upon  the  buttocks, 
and  occasionally  the  coccyx  is  displaced  forward.  The  joint  is  sometimes  the  subject 
of  disease.  The  symptoms  are  very  similar  in  all  these  conditions.  The  attachment 
of  the  gluteus  maximus  makes  a  change  from  a  sitting  to  a  standing  posture  or  the 
reverse  movement  painful  ;  it  also  causes  pain  if  long  steps  are  taken  or  if  running 
is  attempted,  and  this  is  aggravated  by  the  action  of  the  hamstring  muscles  through 
the  medium  of  the  great  sacro-sciatic  ligament.  As  the  fixed  point  of  the  external 
sphincter  is  at  the  tip  of  the  coccyx,  and  as  the  levator  ani  is  inserted  into  the  sides 
of  the  tip,  defecation  is  associated  with  movement  in  this  joint,  and  therefore  with 
pain.  The  latter  is  often  disproportionate  to  the  apparent  severity  of  the  injury  or 
disease,  and  there  may  be  also  great  tenderness  to  the  touch  posteriorly,  with  no  swell- 
ing or  local  heat.  As  these  cases  chiefly  occur  in  women,  Hilton  thinks  that  they 
are  truly  "hysterical,"  and  calls  attention  to  the  intimate  structural  communication 
between  the  many  sacral  nerves  spread  over  the  posterior  surface  of  the  sacrum  and 
coccyx  and  the  anterior  sacral  nerves,  which  join  with  the  hypogastric  plexus  of  the 
sympathetic  within  the  pelvis  and  thence  proceed  to  the  uterus  and  ovaries. 

The  motion  of  the  sacro-coccygeal  joint  is  of  great  importance  in  its  relation 
to  obstetrics.  Ankylosis  occurs,  as  a  rule,  between  the  thirtieth  and  fortieth  years, 
but  the  joint  between  the  first  and  second  sacral  vertebrae  usually  remains  unaffected, 
and  leaves  the  capacity  for  antero-posterior  expansion  during  labor  practically  un- 
impaired. 

The  Sacro-iliac  Joi?it. — Injury  to  and  disjunction  of  this  joint  have  been  suffi- 
ciently described  under  Fractures  of  the  Pelvis  (page  347). 

Disease  of  the  joint,  on  account  of  its  strength  and  immobility,  is  rare.  It  is 
usually  tuberculous  in  character,  and  is  often  secondary  to  suppuration  beneath  the 
ilio-psoas  from  disease  of  the  spine,  ilium,  or  hip.  Pain  is  felt  on  standing,  walking, 
or  sitting,  as  the  sacrum  in  all  these  positions  bears  the  weight  of  all  the  super- 
incumbent structures,  and  on  account  of  its  shape  (page  346)  transmits  it  to  the 
sacro-iliac  synchondrosis.  The  pain  is  increased  by  coughing,  straining,  or  twisting 
the  loins, — i.e.,  by  whatever  calls  into  action  the  muscles  attached  to  the  ilium. 
Through  the  relation  of  the  superior  gluteal  nerve  to  the  front  of  this  joint,  pain  is 
often  felt   in  the  buttock,  and  there  is  wasting  of  the  deep  gluteal  muscles.      The 


PRACTICAL   CONSIDERATIONS:    THE    PELVIC   JOINTS.         351 

relation  of  the  lumbo-sacral  cord,  the  upper  sacral  nerves,  and  the  obturator  has 
already  been  mentioned  (page  347). 

The  body  is  inclined  to  the  sound  side,  so  that  when  sitting  the  pressure  on  the 
diseased  structures  may  be  lessened,  and  when  standing  separation  of  the  joint  sur- 
faces may  be  secured  by  the  weight  of  the  lower  limb.  The  length  of  the  latter  is 
apparently  increased  on  account  of  a  downward  rotation  of 'the  innominate  bone  on 
the  affected  side,  but  measurements  from  the  anterior  spines  to  the  malleoli  will  be 
the  same.  Tenderness  on  direct  pressure  may  be  elicited  just  below  the  posterior 
iliac  spine  ;  on  indirect  pressure  by  squeezing  the  ilia  together  or  by  separating 
them  so  as  to  put  the  anterior  ligaments  on  the  stretch. 

Pus  may  find  its  way  backward  and  appear  at  or  near  the  joint  line.  It  more 
often  passes  forward  on  account  of  the  greater  thinness  of  the  anterior  ligament. 
It  may  then  enter  the  sheath  of  the  ilio-psoas  and  be  conducted  to  the  anterior  surface 
of  the  thigh  ;  it  may  follow  the  obturator  vessels  through  the  obturator  canal  and 
point  on  the  inner  aspect  of  the  thigh  ;  it  may  be  guided  by  the  sciatic  nerve  and 
the  lumbo-sacral  cord  to  the  region  behind  the  greater  trochanter  ;  it  may  descend 
between  the  obturator  fascia  and  the  anal  fascia  into  the  ischio-rectal  fossa  and  appear 
at  the  side  of  the  anus  ;  or,  finally,  it  may  ulcerate  into  the  rectum  and  be  dis- 
charged per  anum. 

The  symphysis  pubis,  as  the  centre  of  the  counterarch  of  the  pelvis  (page  346), 
is  subject  to  manifold  strains  and  injuries  ;  but,  as  the  union  between  the  two  innomi- 
nate bones  at  that  point  is  really  by  a  strong,  solid,  fibro-cartilaginous  band,  and  is 
without  a  synovial  cavity,  and  as  it  is  greatly  strengthened  by  the  decussation  of 
the  fibres  of  the  anterior  and  inferior  ligaments,  its  separation  by  traumatism  is  very 
rare,  and  is  in  effect  a  fracture. 

The  anterior  ligament  is  much  stronger  than  the  posterior  to  resist  the  down- 
ward and  forward  pull  of  the  adductors  and  the  weight  of  the  abdominal  walls  and 
viscera.  Its  strength  accounts  for  the  fact  that  fracture  of  the  horizontal  rami  is 
more  common  than  disjunction  of  the  symphysis  in  cases  in  which  compressing  force 
has  been  applied  to  the  pelvis  laterally. 

In  cases  of  disease  when  the  bond  of  union  is  weakened,  the  function  of  the 
counterarch  readily  explains  the  weakness  and  powerlessness  in  standing  or  sitting. 

The  symphysis  is  of  great  importance  in  its  relation  to  obstetric  mechanics  and 
measurements.  The  plane  of  greatest  pelvic  expansion  extends  from  the  junction  of 
the  second  and  third  sacral  vertebra;  posteriorly  to  the  middle  of  the  symphysis  ; 
the  plane  of  least  pelvic  diameter  from  the  sacro- coccygeal  articulation  to  the  lower 
third  of  the  symphysis. 

There  is  thought  to  be  a  trifling  separation  of  the  symphysis  during  pregnancy 
and  labor,  but  this  is  counteracted  by  the  decussation  of  the  aponeurotic  fibres  of 
the  oblique  muscles  at  the  linea  alba.  On  account  of  this  decussation  these  muscles 
tend,  when  in  vigorous  action,  as  in  parturition,  to  draw  the  pubic  bones  together. 

The  symphysis,  however,  although  comparatively  unyielding,  is  in  almost  the 
same  horizontal  plane  with  the  coccyx,  the  most  movable  bone  that  enters  into  the 
formation  of  the  pelvis,  and  with  the  obturator  foramina  and  the  lower  part  of  the 
great  sacro-sciatic  foramina.  This  is  in  accord  with  the  fact  that  in  no  horizontal 
plane  does  the  pelvis  form  a  complete  bony  and  unyielding  ring,  but  everywhere  the 
resisting  bony  portion  has  opposite  to  it  one  or  more  soft  and  yielding  segments, 
as,  for  example,  the  hypogastric  region  of  the  abdomen  is  opposite  the  fixed  and 
immovable  sacrum  (Morris). 

In  obstructed  labor  in  which  the  delivery  of  a  living  child  may  be  made  possible 
by  a  moderate  increase  in  the  pelvic  outlet,  the  operation  of  symphysiotomy  is  often 
performed.  The  aponeurosis  of  the  recti  is  incised,  the  retro-pubic  structures  sepa- 
rated by  a  finger,  and  a  probe-pointed  bistoury  passed  down  and  made  to  cut  for- 
ward and  upward.  The  incision  may  with  advantage  be  made  in  the  reverse  direc- 
tion, as  the  symphysis  is  wider  at  its  upper  than  at  its  lower  margin,  and  is  wider 
anteriorly  than  posteriorly.  The  subpubic  ligament  and  the  deep  perineal  fascia 
should  then  be  detached  from  the  pubic  arch  close  to  the  bone,  so  as  to  avoid  tear- 
ing the  structures  that" penetrate  the  fascia — the  vagina,  the  urethra,  the  dorsal  vein 
of  the  clitoris,  and  other  venous  channels — when  the  pubes  are  separated. 


352  HUMAN   ANATOMY. 

The  motion  which  permits  of  separation  takes  place  in  the  sacro-iliac  joints,  and 
the  pubic  bones  move  downward  as  well  as  outward,  adding  materially  to  the 
amount  of  pelvic  space  gained.  With  a  separation  of  seven  centimetres  (two  and 
three-fourths  inches),  which  is  possible  under  gentle  pressure  without  laceration  of 
the  sacro-iliac  ligaments,  the  gain  in  the  conjugate  diameter  is  1.5  centimetres 
(three-fifths  of  an  inch)".  The  projection  of  the  anterior  parietal  boss  into  the  pubic 
interspace  as  the  bones  recede  from  each  other  adds  to  the  space  gained,  so  that  by 
opening  the  pubic  joint  to  the  extent  of  6.5  centimetres  (two  and  three-fifths  inches) 
the  increase  in  the  conjugate  diameter  amounts  in  effect  to  about  two  centimetres 
(three-fourths  of  an  inch)  (Cameron). 

THE   FEMUR. 

The  femur,  a  typical  long  bone,  has  a  shaft  and  two  extremities.  The  lower 
end  rests  on  the  tibia,  pretty  nearly  in  a  horizontal  plane  ;  from  this  the  shaft  slants 
outward,  forming  an  angle  of  about  io°  with  a  vertical  line. 

The  upper  extremity  consists  of  a  head,  a  neck,  and  two  trocha?iters.  These 
last  are  on  the  shaft  at  the  junction  with  the  neck,  which  runs  upward  and  inward, 
forming  with  it  an  angle  of  about  1250  on  the  average. 

The  head  is  a  rounded  swelling,  representing  rather  more  than  half  a  sphere, 
capping  the  end  of  the  neck.  It  is  not  put  on  symmetrically,  but  covers  more  of 
the  upper  side  of  the  neck  than  of  the  lower,  and  probably,  as  a  rule,  more  of  the 
front  than  of  the  back.  Occasionally  it  is  prolonged  onto  the  upper  anterior  aspect 
of  the  neck.  It  is  smooth  and  covered  with  articular  cartilage  except  at  a  depression 
for  the  ligamentum  teres,  below  and  posterior  to  the  axis  of  the  head.  Brockway,1 
having  examined  300  femurs,  found  this  depression  oval  in  43  per  cent. ,  with  the 
long  axis  running  downward  and  somewhat  backward,  triangular  in  35  per  cent. , 
and  circular  in  22  per  cent.  In  84  per  cent,  he  found  vascular  foramina,  which  are 
larger  in  the  young  and  not  necessarily  pervious  in  the  old.  In  a  few  cases  he  found 
a  persistence  of  the  fcetal  condition, — namely,  a  groove  descending  nearly  to  the 
border  of  the  articular  surface. 

The  neck4  extends  upward  and  inward,  and  usually  forward.  Being  compressed 
from  before  backward,  it  has  a  front  and  a  back  surface  with  thick  upper  and  lower 
borders.  The  lower  rises  more  steeply  from  the  shaft  than  the  upper,  so  that  the 
neck  is  much  broader  at  the  base  than  where  it  joins  the  head.  The  lower  border  is 
the  longer,  and  the  posterior  surface  is  longer  than  the  anterior.  The  neck  is  smooth 
below  and  behind,  rather  rough  in  front  and  above.  The  upper  border  has  numer- 
ous nutrient  foramina.  The  lower  border,  springing  from  the  inner  aspect  of  the 
shaft,  often  presents  a  rounded  ridge  running  to  the  lesser  trochanter.  The  neck  is 
bounded  behind  by  an  elevation  connecting  the  trochanters,  the  posterior  intertro- 
chanteric ridge}  The  spiral  line,*  also  called  the  anterior  intertrochanteric  ridge, 
bounds  the  greater  part  of  the  front.  It  starts  at  the  little  superior  cervical  tubercle, 
at  the  junction  of  the  top  of  the  neck  with  the  greater  trochanter,  runs  downward  and 
inward  to  the  level  of  the  lesser  trochanter,  where  it  sometimes  presents  a  smaller 
inferior  cervical  tubercle,  and  then,  descending  more  rapidly,  twists  round  the  shaft 
to  join  the  inner  lip  of  the  linea  aspera.  Thus  a  small  part  of  the  neck  between  this 
line  and  the  lesser  trochanter  has  no  boundary.  We  have  found  the  average  length 
of  the  neck  on  thirty-eight  male  bones  and  twenty-six  female  ones  respectively  4. 3 
centimetres  and  4  centimetres.  Bertaux  gives  46.6  millimetres  and  43.1  millimetres 
respectively. 

The  greater  trochanter7  is  a  large  process  projecting  upward  and  outward  from 
the  top  of  the  shaft  and  turning  inward  to  overhang  the  back  of  the  neck.  Seen 
from  the  outside  its  outline  is  roughly  square,  but  the  upper  border  generally  rises 
towards  the  back  so  as  to  form  a  point.  The  anterior  surface  presents  a  depressed 
area  for  the  insertion  of  the  gluteus  minimus.  The  outer  side  is  crossed  by  a  ridge 
running  downward  and  forward,  to  and  in  front  of  which  is  attached  the  gluteus 
medius.  The  upper  border  receives  at  the  front  end  the  tendons  of  the  obturator 
internus  and  gemelli,  and  a  little  farther  back  that  of  the  pyriformis.  The  hollow 
3  Proceedings  of  the  Association  of  American  Anatomists,  1896. 

1  Caput  femoris.     -Fovea  capitis  femoris.     4  Collum  femoris.     'Crista  Intertrochanterica.     6  Linea  intcrtrochanterica. 
7  Trochanter  major. 


THE  FEMUR. 


353 


between  the  neck  and  the  overhanging  trochanter  is  the  trochanteric  ox  digital  fossa.1 
There  is  usually  a  round  recess  at  its  anterior  end  for  the  tendon  of  the  obturator 
externus. 

The  lesser  trochanter2  is  a  rounded  knob  at  the  inner  side  of  the  posterior 
aspect  of  the  shaft  at  its  junction  with  the  neck.  The  posterior  side  is  triangular. 
It  is  at  the  junction  of  three  lines  :  the  posterior  intertrochanteric  ridge,  a  line  run- 
ning down  to  the  linea  aspera,  and  an  inconstant  ridge  on  the  neck.  It  receives  on 
its  end  the  tendon  of  the  ilio-psoas,  and  below  some  of  the  iliac  fibres  of  that  muscle 


fflffl — Fossa  for  round 
ligament 


GREATER  TROCHANTER 


Tubercle  for 
quadratusft 


Third  trochanter. 


Gluteal  ridge 


Upper  extremity  of  left  femur  from  behind. 

That  part  of  the  spiral  line  above  the  level  of  the  lesser _ trochanter  (the  so- 
called  anterior  intertrochanteric  ridge)  is  generally  a  very  distinct  rough  line.  It 
may  be  so  faint  as  to  be  hardly  distinguishable,  and  extremely  rarely  a  hollow  may 
be  found  in  its  place.  The  posterior  intertrochanteric  ridge  is  a  thick  swell- 
ing, broader  above  than  below.  Near  its  junction  with  the  greater  trochanter  it  has 
a  slightly  rounded  prominence,  or  occasionally  a  vertical  line,  linea  quadrat,  for  the 
quadratus  femoris. 

The  shaft3  is  very  strong,  and  convex  in  front,  except  below  the  neck,  where  it 
is  slightly  concave.      In  the  middle  it  would  be  nearly  cylindrical  were  it  not  for  the 

1  Fossa  trochanterica.     2  Trochanter  minor.     3  Corpus  femoris. 


354 


HUMAN    ANATOMY. 
Fig.  370. 


Fossa  for  round  ligament 


--    -  Vastus  interims 


EXTERNAL  CONDYLE 


.«,J5J?f^r\  Adductor  tubercle 


NTERNAL  CONDYLE 


Right  femur  from  before.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


THE   FEMUR. 
Fig.  371. 


355 


Gastrocnemius 
(inner  head) 


I'astus  internus 


Adductor  magnus 


iM'l  mi 

Int.  supracondylar  ridge  -  /JBJ  ,       1[M        E 
PI 

|     ,'        ■ 


.  supracondylar  ridge 


m 

Adductor  tubercle^^   ^^•--"■'  Wtom-fl'Q 

Di  pn  ssion  foi  gastroi  nemius     .-•-'^v.;-'  ,    ^  .;;^f|fciy  .•'''     '" >* .^  l''^W —  Depression  for  gastrocnemii 

)f~&/?^  OrK^--^V$J  ^"^^       EXTERNAL   TUBEROSITY 

Popliteal  groove 


Intercondylar  notch 
Right  femur  from  behind.    The  outline  figure  shows  the  areas  of  muscular  attachment. 


356  HUMAN    ANATOMY. 

prominence  of  the  linea  aspera  at  the  back.  The  surface  on  either  side  of  this  line 
may  be  plane,  concave,  or  convex,  perhaps  more  often  concave.  The  shaft  expands 
slightly  above,  where  it  is  roughly  four-sided  with  rounded  borders.  A  ridge,  which 
is  very  variously  developed,  often  runs  from  the  lower  side  of  the  neck,  separating 
the  anterior  and  internal  surfaces.  When  strong,  it  emphasizes  the  concavity  of  the 
former.      The  lower  third  of  the  shaft  broadens. 

The  linea  aspera1  is  a  prominent  longitudinal  ridge  along  the  back  of  the 
middle  third  of  the  bone,  strengthening  the  concavity  and  giving  attachment  to 
many  muscles.  It  has  two  more  or  less  well-defined  borders  or  lips.  It  is  formed 
from  above  by  the  union  of  three  lines  :  the  spiral,  a  faint  intermediate  line  coming 
down  from  the  lesser  trochanter,  and  a  third  external  one  coming  from  the  back  of 
the  greater  trochanter.  The  upper  part  of  the  last  is  called  the  gluteal  ridge,  as  it 
receives  fibres  of  the  gluteus  maximus.  This  part  may  be  considerably  elevated, 
especially  in  muscular  subjects,  into  a  rough  knob,  the  spurious  third  trochanter. 
The  true  third  trochanter,  which  is  sometimes  seen  at  this  point,  is  a  smooth  rounded 
eminence,  the  analogue  of  the  third  trochanter  extensively  found  among  mammals 
and  particularly  developed  in  the  odd-toed  ungulata.  This  is  sometimes  best 
developed  on  delicate  female  femurs  with  no  rough  muscular  ridges.  Of  course  the 
two  forms  may  coexist.  A  rough  elongated  depression,  the  fossa  hypotrochanterica, 
also  receiving  fibres  of  the  gluteus,  is  sometimes  found  outside  the  gluteal  ridge. 
The  linea  aspera  divides  somewhat  below  the  middle  of  the  bone  into  two  supra- 
condylar ridges,  which  bound  a  triangular  space2  as  they  pass  down  to  the  tops 
of  the  condyles.  The  outer  ridge  is  at  first  much  the  sharper,  but  it  becomes  indis- 
tinct an  inch  or  more  above  the  condyle.  The  inner  is  but  slightly  raised  ;  it  is 
interrupted  above  its  middle  for  the  passage  of  the  femoral  vessels  into  the  popliteal 
space.  It  ends  in  the  sharp  adductor  tubercle  above  the  inner  border  of  the  condyle. 
At  its  termination  the  shaft  has  four  surfaces :  a  posterior  one  nearly  plane,  a  front 
one  slightly  convex,  a  distinct  outer  one,  and  an  oblique  inner  one,  passing  insensibly 
backward  and  inward  from  the  anterior  surface.  There  are  usually  two  nutrient 
foramina,  both  directed  upward,  the  larger  between  the  lines  converging  to  the 
linea  aspera,  the  other  near  the  middle  of  the  bone,  a  little  to  the  inside  of  that  line. 

The  lower  extremity,  articulating  with  the  tibia  below  and  the  patella  in 
front,  presents  two  backward  prolongations,  the  condyles,  along  which  the  tibia 
travels  in  flexion.  These  are  compressed  from  side  to  side,  and  separated  by  the 
intercondylar  fossa,3  which  is  beneath  the  back  part  of  the  shaft.  The  inner  co?idyle* 
is  the  lower  when  the  shaft  is  vertical,  but  in  life  both  are  in  the  same  plane.  The 
outer 5  is  longer  from  before  backward  ;  it  lies  in  an  antero-posterior  plane,  while  the 
inner  extends  backward  and  inward.  The  lateral  outline  of  each  has  been  well  com- 
pared to  a  watch-spring  partly  uncoiled.  Each  bears  a  tuberosity  near  the  posterior 
end  of  the  lateral  side,  very  nearly  in  continuation  with  the  supracondylar  ridges 
for  the  so-called  lateral  ligaments  of  the  knee.  A  depression  on  each  side  for  the 
head  of  the  gastrocnemius  is  found  above  and  behind  the  tuberosities.  The  ex- 
ternal condyle  bears  a  deep  oblique  groove  for  the  tendon  of  the  popliteus  at  the 
back  of  the  outer  surface. 

The  articular  surface  for  the  knee  not  only  covers  the  lower  and  posterior 
aspects  of  the  condyles,  but  is  prolonged  upward  on  the  front  for  the  support  of  the 
patella,  as  a  groove  which  is  shown  by  horizontal  sections  to  be  concave  in  the 
middle  and  convex  at  either  side.  The  upper  boundary  slants  upward  and  outward, 
the  shaft  just  above  it  presenting  a  slight  depression.  Its  outer  border  is  a  promi- 
nent ridge  resisting  outward  dislocation  of  the  knee-pan.  The  patellar  surface  is 
continuous  with  the  articular  facets  of  the  condyles,  being  marked  off  only  by  certain 
lines,  which,  though  distinct  on  the  fresh  cartilage,  are  often  obscure  on  the  dried 
bone,  representing  the  separation  of  these  joints.  In  some  animals  the  separation  is 
complete.  The  outer  line,  usually  concave  posteriorly,  runs  obliquely  inward  to 
just  in  front  of  the  intercondylar  notch.  The  inner,  less  clear  and  generally  straight, 
begins  much  farther  forward  and  runs  obliquely  backward  to  the  inner  side  of  the 
front  of  the  notch.  The  outer  in  particular  marks  a  distinct  change  of  level.  Be- 
hind these  lines  the  articular  surfaces  extend  along  the  lower  and  posterior  sides  of 
the  condyles  even  onto  the  upper  aspect,  so  as  to  allow  extreme  flexion  of  the  knee. 

1  Linea  aspera.     -  Planum  popliteum.     3 Fossa  intercondyloidea.     *Condylus  medialis.     6Condylus  lateralis. 


THE    FEMUR. 


357 


Frontal  sections  through  the  back  part  of  the  condyles  show  that  the  inner  is  nearly- 
symmetrical  in  its  convexity  from  side  to  side,  while  the  inferior  surface  of  the  outer 


Fig.  372. 


Outer  head  of  gastrocnemius 


External  lateral  ligament 

External  tibial  facet 


Popliteal  groov 


Lower  end  of  right  femur,  outer  aspect. 


slants  upward  and  inward.  The  length  of  the  articular  surface  of  the  inner  condyle 
from  the  back  to  the  line  marking  off  the  patellar  facet  is  considerably  greater 
(perhaps  two  centimetres)  than  that  of  the  outer. 


Fig.  373. 

Patellar  surface 


External  tuberosit) 


Limit  of  patellar  surface 
Internal  tuberosity 


ght  femur  fr> 


Structure. — Transverse  sections  in  series  through  the  whole  length  of  the 
femur  are  very  instructive.  They  show  the  great  strength  of  the  shaft,  the  thick- 
ness of  its  walls,  the  smallness  of  the  central  canal,  and  the  addition  made  by  the 
linea  aspera  ;  likewise  that  the  shaft  becomes  four-sided  both  above  and  below, 
and  that  in  the  latter  region  the  greater  diameter  is  transverse.  Coincident  with 
these  changes  are  a  great  diminution  of  the  thickness  of  the  walls  and  a  great  increase 
of  the  spongy  tissue.  The  weakness  of  the  walls  just  above  the  knee  is  very  striking. 
The  architecture  of  the  condyles  is  well  exhibited,  consisting  of  vertical  plates  run- 


358 


HUMAN    ANATOMY. 


ning  in  the  main  forward  and  backward,  crossed  by  transverse  ones,  in  part  diverging 
from  the  solid  bone  at  the  bottom  of  the  intercondylar  notch.  Such  sections  show 
also  the  prominence  of  the  outer  border  of  the  patellar  surface  and  the  curve  of  that 
articulation.  At  the  upper  end  they  display  the  prominence  of  the  lesser  trochanter, 
the  series  of  strong  plates  crossing  it,  which  at  a  higher  level  are  seen  diverging  from 
a  single  plate,  Bigelow's  true  neck1  (Merkel's  calcar femorale'1 '),  to  which  we  shall 
return.  The  greater  trochanter,  quite  free  from  all  pressure,  is  very  light  and  the 
head  very  dense.  Frontal  sections  of  the  head  and  neck  (Fig.  374)  show  the  series 
of  plates  given  off  successively  from  both  the  inner  and  outer  walls  forming  Gothic 


Fig.  375. 


Oblique  section  of  right  femur  parallel  to  lower 
border  of  neck,  through  upper  end  of  lesser  tro- 
chanter. 


Frontal  section  through  upper  end  of  femur,  she 
arrangement  of  pressure  and  tension  lamella 


arches  at  the  top  of  the  bone.  The  under  side  of  the  neck  is  thick  and  gives  off  a 
series  of  plates,  near  together,  running  obliquely  up  into  the  head  in  the  line  of  the 
greatest  pressure,  especially  when  the  shaft  is  oblique,  as  in  life.  A  less  distinct 
series  of  long  arches  springs  from  the  outer  side,  curving  across,  and  acting  as 
"ties."  The  head  is  of  the  round-meshed  pattern,  fitted  to  resist  pressure  in  any 
direction,  often  presenting  an  almost  solid  core  at  the  middle,  and  generally  showing 
the  curved  line  of  union  of  the  epiphysis  of  the  head.  The  true  neck  of  the  femur  is 
a  plate,  or  a  series  of  plates,  springing  from  a  thick  spur  of  bone,  which  leaves  the 
hind  wall  of  the  neck  to  run  outward  towards  the  greater  trochanter.      This  is  best 

1  The  Hip,  Philadelphia,  1869  ;  also  Boston  Medical  and  Surgical  Journal,  1875. 

2  Virchow's  Archiv,  Bd.  1.,  1870. 


THE   FEMUR.  359 

seen  in  sections  parallel  with  the  lower  wall  of  the  neck  (Fig.  375)  ;  it  appears  also 
in  transverse  ones.  When  strongly  developed  it  can  be  shown  as  a  real  septum  by 
gouging  away  the  spongy  tissue  of  the  posterior  intertrochanteric  ridge  beneath 
which  it  passes. 

Sexual  and  Individual  Variations. — Apart  from  general  lightness  of  struc- 
ture, the  female  femur  presents  distinctly  smaller  articulations  than  the  male.  The 
average  diameter  of  the  head  of  thirty-eight  male  bones  is  4.8  centimetres,  and  of 
twenty-six  female  ones  4.15  centimetres.  In  only  two  of  the  male  bones  is  the 
diameter  less  than  4.5  centimetres,  and  in  only  two  of  the  female  is  it  greater.  Both 
of  the  latter  are  long  ones.  In  women  the  size  of  the  head  increases  with  the  length, 
but  in  men  a  short  femur  is  about  as  likely  to  have  a  large  head  as  a  long  one.  The 
breadth  of  the  articular  surface  of  the  knee  is  less  conclusive  ;  the  averages  are  8.3 
centimetres  and  7.4  centimetres,  but  there  is  much  overlapping.  The  peculiarity 
of  outline  in  the  typical  female  femur  is  very  characteristic  when  well  marked  :  the 
shaft  narrows  gradually  from  the  condyles  till  at  or  above  the  middle  the  nar- 
rowest part  is  reached,  above  which  there  is  a  much  less  evident  expansion.  The 
typical  male  bone  narrows  much  more  suddenly  above  the  condyles,  so  that  the 
stouter  shaft  soon  reaches  a  tolerably  uniform  thickness.  The  inclination  of  the 
shaft  is  somewhat  greater  in  woman.  The  angle  with  a  vertical  line  in  the  above 
series  is  9.30  in  man  and  10. 6°  in  woman.  (According  to  Bertaux,  it  is  8.750 
and  ii°.)  It  is  naturally  greater  in  shorter  femurs,  and  consequently  is  of  very 
doubtful  value  as  a  sexual  characteristic,  especially  in  view  of  the  great  individual 
variation.  The  angle  of  the  neck  with  the  shaft  is  of  minor  significance.  In  the 
writer's  series  it  ranges  from  no°  to  144°,  the  average  for  men  being  125.1°  and 
that  for  women  125. 6°.  In  the  male  bones  there  is  little  connection  between  the 
length  of  the  femur  and  the  size  of  the  angle  ;  in  women  long  bones  have  a  large 
angle  and  short  bones  a  small  one.  The  average  angle  of  the  longer  half  of  the 
male  bones  is  126. 50  and  that  of  the  shorter  123.6°,  while  the  longer  and  shorter 
halves  of  the  female  series  give  129.2°  and  121.9°  respectively.  A  long  neck  gen- 
erally has  a  high  angle  and  a  short  neck  a  low  one.1  Thus  it  appears  that  there  are 
great  variations  in  the  angle  of  the  shaft  and  that  of  the  neck.  The  same  is  true  of 
almost  every  detail.  The  forward  inclination  of  the  neck  is  in  two- thirds  of  the  cases 
from  5°  to  20°,  and  usually  from  12°  to  14°.  Its  extreme  is  37°.  Very  rarely  this 
angle  is  negative, — that  is,  the  neck  slants  backward.  An  extreme  negative  angle 
of  25°  has  been  observed,  but  this  is  extraordinary.2  The  curve  and  outline  of  the 
shaft  vary  much.  An  extreme  form  is  the  pilastered  femur,  very  convex,  with  a 
prominent  linea  aspera,  generally  stout,  implying  strength.  An  opposite  form  is 
nearly  straight,  has  a  low  linea  aspera,  and  is  flattened  before  and  behind  in  the 
upper  part  of  the  shaft.  In  extreme  forms  the  depression  in  the  front  of  the  top  of 
the  shaft  is  increased  and  bounded  internally  by  a  sharp  ridge  running  up  to  the 
under  side  of  the  neck,  which  usually  has  a  low  angle.  Though  apparently  weaker, 
this  form  is  sometimes  found  in  very  powerful  men. 

The  index  of  the  shaft  is  the  proportion  of  the  thickness  to  the  breadth,  the 
latter  being  100.  Thus  (thlc^"^t^  100\.  This  is  taken  at  about  the  middle  of  the 
shaft  where  the  linea  aspera  is  most  prominent.  It  is  said  to  be  greater  on  the  right 
than  on  the  left  and  in  men  than  in  women.  Bertaux  found  the  average  in  adults 
104.4,  and  in  a  series  of  young  femurs  112. 1. 

The  index  of  the  neck  is  the  proportion  of  the  thickness  to  the  height.  Thus 
/thickness  x  ioo\  ^^  average  ;s  J23.05-  It  is  a  trifle  higher  in  women,  but  the 
difference  in  unimportant. 

A  strong  convexity  of  the  shaft  outward  as  well  as  forward  suggests  a  patho- 
logical condition. 

Development  and  Changes. — The  shaft  begins  to  ossify  not  later  than  the 
seventh  week  of  fcetal  life.  A  centre  appears  in  the  lower  end  during  the  last  month 
of  pregnancy.  It  is  rarely  wanting  at  birth,  but  the  precise  time  of  its  appearance 
as  well  as  its  size  are  too  variable  to  make  it  a  very  valuable  guide  to  the  age  of  the 

1  H.  H.  Hirsch  :  Anatomische  Hefte,  Bd.  xxxvii.,  1S99. 

2  Mikulicz  :  Arch,  fur  Anat.  und  Phys.,  1878. 


36° 


HUMAN    ANATOMY. 


foetus  or  infant.  Its  growth  seems  to  be  slight  during  the  first  three  weeks  after 
birth.  The  neck  grows  as  a  part  of  the  shaft  and  receives  three  epiphyses, — one  for 
each  trochanter  and  one  for  the  head,  which  fits  over  it  like  a  cap.  The  latter 
appears  in  the  second  half  of  the  first  year,1  and  is  pretty  conclusive  evidence  that 
the  age  of  six  months  at  least  has  been  reached.  The  epiphysis  for  the  greater 
trochanter  comes  in  the  third  year  (sometimes  some  years  later),  and  that  for  the 
lesser  at  a  time  variously  stated  as  from  eight  to  fourteen  years.      It  is  probable  that 


Fig.  376. 


Ossification  of  femur.  A,  at  eighth  foetal  month;  B,  at  birth;  C,  during  first  year;  D,  at  eight  years;  A",  at 
about  fifteen  years,  a,  centre  for  shaft;  b,  lower  epiphysis;  c,  for  head;  dt  for  greater  trochanter;  e,  for  lesser 
trochanter. 


the  former  is  much  nearer  the  mark.  The  head  unites  with  the  shaft  at  about 
eighteen,  the  trochanters  somewhat  later  ;  probably  there  are  great  variations  ;  but 
all  these  superior  epiphyses  should  be  joined  by  nineteen,  and  at  twenty  the  line  of 
union  is  indistinct  or  lost.  An  epiphysis  for  the  third  trochanter  has  been  seen. 
The  lower  epiphysis  is  joined  by  twenty,  and  often  sooner.  At  birth  the  angle  of 
the  neck  may  be  1600,  but  is  often  less  ;  it  diminishes  under  the  pressure  of  the 
weight  as  the  child  walks,  and  by  the  time  of  puberty  has  probably  assumed  about 
its  permanent  angle.  There  is  no  reason  to  believe  that  the  angle  diminishes  in 
old  age. 

Surface  Anatomy. — The  greater  trochanter  can  be  explored  when  the  muscles 
about  it  are  relaxed.  The  lesser  trochanter,  though  deep,  can  be  felt  from  behind. 
A  large  third  trochanter  can  be  recognized,  and  must  not  be  mistaken  for  a  tumor. 
Owing  to  the  individual  variations  of  the  neck  and  the  pelvis,  the  relations  of  the 
trochanter  must  vary.  According  to  Langer,  a  horizontal  line  at  the  top  of  the 
greater  trochanter  divides  the  head,  touches  the  top  of  the  symphysis,  and  about 
divides  the  nates.  This  is  particularly  true  of  broad  pelves,  and  therefore  of  women. 
We  have  found  from  measurements  of  118  males  and  37  females  that  the  trochanter 
is  1.1  centimetres,  on  the  average,  higher  than  the  symphysis  in  the  male  and  three 
millimetres  in  the  female.  Topinard  gives  as  provisional  distances  in  the  male  the 
following  :  the  anterior  superior  spine  of  the  ilium  is  six  centimetres  above  the  head 
of  the  femur,  the  latter  two  centimetres  above  the  greater  trochanter  (practically 
agreeing  with  Langer),  and  the  greater  trochanter  two  centimetres  above  the  pubes. 
The  head  of  the  femur  lies  under  a  crease  beneath  the  proper  fold  of  the  groin,  and 
can  sometimes  be  distinguished  at  the  inner  side  of  the  sartorius.  N61aton's  line  is 
drawn  from  the  anterior  superior  spine  of  the  ilium  to  the  most  prominent  point  of 
the  tuberosity  of  the  ischium.  It  should  just  touch  the  top  of  the  greater  trochanter. 
The  shaft  is  too  thickly  covered  to  be  examined  in  detail,  except  near  the  knee.  The 
sides  of  both  condyles  are  easily  examined  ;  the  lateral  tubercles  and  the  adductor 

1  Fagerlund  :  Wiener  Med.  Presse,  1S90. 


PRACTICAL    CONSIDERATIONS  :    THE    FEMUR. 


*6i 


tubercle  can  be  felt.  The  latter  marks  the  line  of  union  of  the  lower  epiphysis 
with  the  shaft.  When  the  knee  is  flexed,  the  patellar  surface,  its  borders,  and  part 
of  the  articular  surface  of  the  condyles  can  be  felt. 

PRACTICAL   CONSIDERATIONS. 

Before  the  age  of  four  the  upper  epiphysis  is  not  distinct,  and  traumatism  is  apt 
to  result  in  separation  of  the  upper  cartilaginous  end  of  the  bone, — i.e.,  a  fracture 
through  some  part  of  the  cartilaginous  neck.  Later  three  epiphyses  may  be  affected 
by  injury, — viz.,  those  for  the  head  and  the  two  trochanters. 


Fig.  377. 


Section  through  hip-joint,  showing  epiphyses  of  head  and  greater  trochanter  of  femur. 


The  epiphysis  for  the  head  is  shaped  like  a  hollow  hemisphere  set  upon  the 
convex  upper  end  of  the  neck.  The  epiphyseal  line  slopes  downward  and  inward, 
and  is  entirely  within  the  synovial  membrane. 

Separation  by  indirect  violence  occurs  as  a  result  of  extreme  extension  of  the 
thigh,  as  in  falls  backward  with  the  limb  fixed,  or  as  when  a  child  carried  in  the 
arms  of  a  nurse  throws  itself  violently  backward.  The  force  is  thus  in  effect 
applied  at  the  lower  end  of  the  femur,  which  acts  as  the  long  arm  of  a  lever.  When 
it  is  carried  far  backward  the  ilio-femoral  ligament  is  put  upon  the  stretch,  and  its 
point  of  insertion  becomes  the  fulcrum.  The  resistance  (or  weight)  is  at  the  point 
where  the  forward  movement  of  the  short  arm  of  the  lever — the  neck  and  head — 


362 


HUMAN   ANATOMY. 


is  resisted,  perhaps  slightly,  by  the  ligamentum  teres,  but  chiefly  by  the  anterior 
margin  of  the  acetabulum. 

Separation  is  followed  by  shortening.  This  may  be  recognized  by  Nelaton's  line 
(Fig.  378),  by  the  base  line  of  the  "  ilio-femoral  triangle"  (Bryant's)  (Fig.  379), 
or  by  Robson's  line,  which  is  a  line  dropped  vertically  from  the  anterior  spine  to 
meet  a  transverse  line  drawn  forward  and  inward  from  the  tip  of  the  greater  tro- 
chanter across  the  front  of  the  thigh,  the  patient  being  in  dorsal  decubitus. 

Eversion,  from  the  weight  of  the  limb,  is  usually  present. 

The  toughness  of  the  periosteum  and  the  strength  of  the  cartilaginous  bond 
between  the  neck  and  head  in  childhood  may  make  the  epiphyseal  line  stronger 
than  the  thin  neck  beneath  it,  and  fracture  of  the  neck  may  therefore  occur  even  in 
young  children  or  adolescents.  The  symptoms  are  very  similar  to  those  of  epi- 
physeal separation.  The  crepitus  may  be  rough  instead  of  "  muffled."  The  X-rays 
will  sometimes  differentiate  the  two  conditions.  In  a  case  of  injury  to  the  hip  in  a 
young  person,  it  is,  however,  probable  that  epiphyseal  disjunction  will  result  rather 
than  fracture  of  the  neck;  but  in  youth,  on  account  of  the  presence  of  the  epiphyseal 


Fig.  378. 


Showing  Nelaton's  lin 


>1 

Showing  Bryant's  triangle 


joint  and  the  weakness  of  the  neck,  both  of  these  lesions  are  more  frequent  than 
dislocation.  Either  of  them  will  convert  the  normal  obliquity  of  the  neck  to  a 
position  more  nearly  horizontal,  causing  prominence  and  ascent  of  the  trochanter, 
and  bringing  about  at  once  the  condition  known  as  coxa  vara,  which  will  probably 
increase  later,  as  whenever  the  angle  of  the  neck  with  the  shaft  is  diminished  the 
strain  upon  the  former  is  increased.  Thus,  either  epiphyseal  separation,  fracture 
of  the  neck,  or  slight  rhachitis  in  early  childhood  may  result  in  coxa  vara  at  the 
period  of  adolescence,  when  the  softening  incident  to  rapid  growth  is  taking  place, 
the  body  weight  is  increasing, — often  disproportionately, — and  laborious  occupations 
are  frequently  begun. 

The  epiphysis  for  the  greater  trocha?iter  unites  at  about  the  nineteenth  year.  It 
is  easily  dislocated,  almost  always  from  direct  violence,  and  usually  between  the 
thirteenth  and  eighteenth  years,  because  that  is  the  period  of  greatest  exposure  to 
traumatism,  and  because  at  the  latter  date  the  epiphysis  is  joined  to  the  shaft.  The 
line  of  junction  with  the  shaft  is  on  the  level  of  the  tubercle  for  the  quadratus  on  the 
posterior  edge  of  the  greater  trochanter  (Fig.  383).  It  is  therefore  below  the  level  of 
the  capsule  of  the  hip-joint  and  of  the  insertions  of  the  glutei,  obturators,  pyriformis, 


PRACTICAL    CONSIDERATIONS  :    THE    FEMUR. 


363 


and  gemelli.  Disjunction  from  indirect  violence — through  the  action  of  these 
muscles — is  rare,  on  account  of  :  (1)  The  prolongation  downward  and  outward  of 
the  fibres  of  the  capsular  ligament  which  extend  below  the  epiphyseal  line.  (2  )  The 
attachment  above  that  line  of  some  of  the  aponeurotic  fibres  of  origin  of  the  vastus 
externus.      (3)  The  toughness  of  the  periosteum. 

For  these  same  reasons,  when  disjunction  does  occur,  there  is  usually  but  little 
displacement.  If  it  exists,  and  is  marked,  the  epiphysis  is  drawn  into  approxi- 
mately the  same  position  as  that  occupied  by  the  head  of  the  bone  in  a  dislocation 
onto  the  dorsum  of  the  ilium.  The  age  of  the  patient  (epiphyseal  separation  being 
impossible  after  nineteen  and  dislocation  rare  before  that  age)  and  the  failure  of  the 
displaced  epiphysis  to  move  with  rotation  of  the  femur  are  aids  to 
diagnosis.  The  absence  of  rotation  and  of  shortening  of  the  limb 
distinguishes  this  lesion  from  "  extracapsular"  fracture  of  the 
neck. 

About  fifty  per  cent,  of  the  recorded  cases  have  died  of  py-  I^'ST 
aemia.  This  is  probably  because  :  ( 1 )  The  greater  trochanter  is 
an  apophysis  rather  than  an  epiphysis,  and  is  in  contact  at  its 
base  with  cancellous  tissue  of  a  lighter  and  more  spongy  character 
than  that  adjoining  the  true  terminal  epiphyses  of  the  long  bones. 
(2)  The  violence  causing  the  injury  is  direct  and  thus  associated 
with  much  bruising  and  crushing  of  that  tissue.  (3)  The  disjunction 
is  attended  by  extensive  detachment  of  the  periosteum  from  the 
vascular  upper  end  of  the  bone,  as  the  periosteum  over  the  tro- 
chanter is  very  thin  and  the  dense  tendinous  fibres  are  almost  di- 
rectly attached  to  the  osseous  tissue  itself  (Poland). 

The  epiphysis  for  the  lesser  trochanter  can  be  separated  usu-  ft  [\ 

ally  only  between  the  thirteenth  year  and  the  nineteenth,  when  it 
joins  the  shaft.  But  one  case  has  been  recorded.  It  was  then 
torn  off  in  a  boy  of  fourteen,  as  the  result  of  the  strain  on  the  ilio- 
psoas in  a  fall  backward  on  the  feet.    Death  from  pyaemia  followed. 

Fracture  of  the  neck  of  the  femur  is  common  (especially  in 
old  age),  in  spite  of  its  depth  and  its  thick  covering  of  soft  parts, 
because  :  (1)  In  falls  upon  the  feet  or  hip  it  receives  and  transmits 
much  of  the  weight  of  the  body,  which,  in  the  former  case  at 
least,  reaches  it  in  a  direction  which  causes  a  cross-strain  favorable 
to  fracture.  (2)  It  is  a  comparatively  fixed  portion  of  a  very 
long  lever  into  the  upper  end  of  which  many  powerful  muscles  are 
inserted.  (3)  It  is  of  itself  lengthened  and  thus  made  more  vul- 
nerable,— as  compared,  for  example,  with  the  neck  of  the  hu- 
merus,— so  as  to  increase  the  leverage  of  these  muscles,  the  degree 
of  mobility  of  the  hip-joint,  and  the  basis  of  support  for  the  trunk. 
(4)  Its  mechanical  weakness  increases  in  old  age  (a)  from  the 
absorption  of  cancellous  tissue  which  occurs  everywhere  in  the 
skeleton,  but  begins  and  proceeds  most  quickly  ( according  to  Llnes °en'uarCtur 
Humphry)  in  the  femoral  neck  ;  (6)  from  a  corresponding  thin- 
ning of  the  compact  tissue,  including  that  part  of  the  cortex  which  unites  the  lesser 
trochanter  and  the  under  and  anterior  part  of  the  head,  the  line  of  greatest  press- 
ure in  the  erect  position.  (5)  The  angle  between  the  neck  and  the  shaft  is 
believed  by  many  surgeons  gradually  to  decrease,  though  this  change  is  not  in- 
variable and  is  denied  by  some  excellent  authorities.  It  is  true,  however,  that  the 
angle  is  smaller  the  less  the  stature  ;  that  it  is  thus  smaller  in  women,  and  that 
in  them,  after  the  age  of  fifty,  these  fractures  are  two  and  a  half  times  more  common 
than  in  men. 

When  the  age  of  the  patient  is  advanced,  and  the  violence  is  slight  and  indirect, 
the  femoral  neck  breaks  more  frequently  near  its  junction  with  the  head,  because 
there  it  is  thinnest  and  weakest.      Such  fractures  are  entirely  intracapsular. 

In  younger  persons,  and  especially  if  the  violence  is  severe  and  is  received 
directly  upon  the  hip,  the  fracture  is  more  apt  to  involve  the  base  or  wider  portion 
of  the  neck,  and  is  likely  to  be  partly  intra-   and  partly   extracapsular.       If  it  is 


364 


HUMAN    ANATOMY. 


entirely  below  the  line  of  capsular  attachment  both  in  front  and  behind,  it  cannot  be 
a  fracture  of  the  neck,  as  it  would  then  be  below  the  anterior  intertrochanteric  line, 
and  would  involve  the  extreme  upper  end  of  the  shaft.      Posteriorly,  it  is  possible 

for  a  partial  fracture  of  the  neck  to 
Fig.  3S1.  be  extracapsular,   as  the  insertion  of 

the  capsule  is  from  twelve  to  seven- 
teen millimetres  (one-half  to  two- 
thirds  of  an  inch)  above  the  base 
of  the  neck.  Impaction  of  fracture 
at  the  narrow  part  of  the  neck  is  not 
very  common.  When  it  occurs, 
some  spicula  of  the  compact  cortex 
of  the  neck  are  driven  into  the  ex- 
panded cancellated  structure  of  the 
head. 

Impaction  of  fracture  at  the  base 
is  common,  because  the  spongy  tro- 
chanter is  easily  thrust  upon  and 
sometimes  split  by  the  small  and 
relatively  compact  cervix. 

In  most  fractures  of  the  neck 
there  will  be  found  : 

(1)  Eversion,  due  chiefly  to  (a) 


ving  elevation  of  tip  of  trochanter  and  shortening 
baje  of  Bryant's  triangle  in  fracture  of  neck  of  femur;  a,  a 
on  sound  side;  b,  on  fractured  side. 


Fig.  382. 


the  weight  of  the  limb,  which  tends  normally  to  roll  outward  ;  but  also  to  a  certain 
extent  to  (6)  the  action  of  the  ilio- psoas  and  other  external  rotators  ;  (c)  the  greater 
comminution  or  crushing  of  the  posterior  wall  of  the  neck,  which  is  weaker  than  the 
anterior  wall. 

(2)  A  fulness  over  the  upper  portion  of  Scarpa's  triangle,  due  to  effusion  into 
the  hip-joint  or  to  forward  projection  of  the  fragments  against  the  front  of  the 
capsule.  This  is  likely  to  occur  because  the  neck  is  normally  convex  forward,  the 
lesser  trochanter,  marking  the  inner  and  lower  boundary  of  the  neck,  being  on  a 
plane  posterior  to  the  head  ;  and  because 
of  the  greater  destruction  of  the  posterior 
portion  of  the  neck. 

(3)  Relaxation  of  the  ilio-tibial  band 
of  the  fascia  lata  (page  367). 

(4)  Approximation  of  the  trochanter 
to  (a)  the  anterior  superior  spine,  as  shown 
by  shortening,  best  determined  by  the 
length  of  the  horizontal  side  or  base  of  the 
ilio-femoral  triangle  ;  and  to  (d)  the  mid- 
line of  the  body,  as  shown  by  Morris's  line. 
Nelaton's  line  shows  the  former,  but  in- 
volves more  disturbance  of  the  patient. 
Chiene  demonstrates  shortening  by  placing 
the  edge  of  a  straight  flexible  piece  of  metal 
on  the  two  anterior  spines  and  that  of  an- 
other on  the  tips  of  the  two  trochanters. 
Parallelism  negatives  the  idea  of  fracture. 
Morris  measures  from  the  symphysis  pubis 
to  the  external  trochanteric  surfaces.  The 
distance  is  lessened  on  the  side  of  fracture. 

rp,  .  -ii  ,  of  the  injurec 

1  hese  points  can  easily  be  understood    of  neck  of  fe; 
by  reference  to  Figs.  381  and  382. 

Emphasis  is  placed  on  these  measurements  because  it  is  perhaps  more  important 
in  this  than  in  any  other  fracture  to  avoid  vigorous  efforts  to  elicit  crepitus. 

The  blood-supply  of  the  proximal  fragment — the  head — will  reach  it  only 
through  the  reflected  portions  of  the  capsule,  untorn  strips  of  periosteum,  and  the 
ligamentum  teres,  that  through  the  cervix  being  cut  off.      It  is,  therefore,  scanty  and 


PRACTICAL    CONSIDERATIONS  :    THE    FEMUR. 


365 


may  be  insufficient  to  furnish  reparative  material.  Any  movement  that  might  tear 
the  remaining  connections  between  the  fragments  is,  therefore,  most  undesirable. 
The  great  length  of  the  lower  fragment,  and  the  leverage  thus  exerted  as  a  result  of 
any  motion  of  the  inferior  extremity,  together  with  the  action  of  the  powerful  muscles 
running  from  the  pelvis  to  the  thigh,  make  it  especially  difficult  to  keep  the  frac- 
tured surfaces  in  close  apposition,  particularly  if  the  small  part  of  the  neck  is  involved. 
Impaction,  even  if  very  slight,  may  thus  be  a  favorable  circumstance,  and  should  not 
be  broken  up  by  rough  handling. 

Intracapsular  fractures,  in   spite   of  the  scanty  blood-supply,  the  presence  of 
synovial  fluid,  which  is  perhaps  the  most  important  unfavorable  factor,  and  the  mo- 
bility of  the  lower  fragment,  do  unite,  but  rather  as  an  excep- 
tion.     As  a  rule,  fractures  at  the  base  of  the  neck  unite.  Fig.  383. 

Fracture  of  the  shaft  is  most  common  at  the  middle,  at 
the  point  of  greatest  convexity  of  the  forward  curve,  in  spite 
of  the  fact  that  here  the  bone  is  denser  and  its  compact  outer 
wall  thicker.  At  the  upper  third  fracture  is  usually  due  to 
indirect  violence,  at  the  lower  third  to  direct  violence.  In  the 
former  case  it  is  apt  to  be  oblique,  in  the  latter  transverse. 
These  lesions,  as  well  as  those  of  the  lower  end,  just  above  the  Y<'."\ 
condyles,  will  be  considered  in  their  relation  to  the  muscles 
that  influence  them  (page  644). 

The  lower  epiphysis  of  the  femur,  the  only  one  whose  ossi- 
fication begins  before  birth, — "with  the  exception  of  the  occa- 
sional early  appearance  of  the  osseous  nucleus  in  the  upper 
epiphysis  of  the  tibia' '  (Poland), — is  the  last  to  join  its  diaphy- 
sis,  union  occurring  about  the  twentieth  year.  It  has  a  cup- 
shaped  upper  surface,  which  is  higher  externally.  Its  internal 
level  is  just  beneath  the  adductor  tubercle.  The  epiphysis 
includes  all  the  articular  surfaces  of  the  lower  end  of  the 
femur. 

In  the  majority  of  the  cases  of  disjunction  of  this  epiphy- 
sis the  cause  has  been  hyperextension  of  the  tibia  on  the  femur, 
often  combined  with  some  twisting  and  traction  upon  the  leg, 
as  when  a  boy  hanging  behind  a  cab  has  his  foot  caught  be- 
tween the  spokes  of  a  wheel.  In  twenty-seven  out  of  sixty- 
eight  cases  the  lesion  was  caused  in  this  way. 

The  ligaments  of  the  knee-joint  are  so  powerful  (as  they 
must  be  for  security,  on  account  of  the  shape  of  the  bones  that 
enter  into  it)  that  when  the  leg  is  brought  into  overextension 
tremendous  leverage  is  exerted  on  this  epiphysis  through  the 
crucial  ligaments,  the  external  and  internal  lateral  ligaments, 
and  the  popliteus  muscle,  aided  by  the  gastrocnemius.  Al- 
though the  latter  is  attached  partly  above  the  epiphyseal  line, 
the  periosteum  is  torn  off  the  lower  end  of  the  diaphysis  down 
to  the  extremely  dense  layer  at  the  cartilaginous  junction. 
The  muscle  then  becomes  an  important  factor  in  carrying  the  femVr.  ' 

epiphysis  forward — the  usual  displacement — and,  aided  by  the 

popliteus,  in  rotating  its  posterior  upper  edge  downward.  The  mechanism  has  been 
compared  to  that  of  fractures  of  the  radius  in  falls  upon  the  hand,  the  posterior 
ligament  of  the  knee-joint  bringing  a  cross-strain  upon  the  epiphysis  similar  to  that 
conveyed  to  the  radius  by  the  anterior  ligament  of  the  wrist. 

The  diaphysis  projects  into  the  popliteal  space  or  through  the  skin,  and  has 
caused  grave  injuries  to  vessels  and  nerves.  Amputation  has  been  required  in  a 
large  proportion  of  these  cases,  on  account  of  these  injuries  or  because  of  the  de- 
tachment of  the  periosteum  and  the  suppuration  that  often  follows  it.  The  joint 
is  rarely  involved,  because  the  ligaments  uniting  the  bones  of  the  leg  to  the 
epiphysis  are  more  powerful  than  the  cartilaginous  connections  of  the  latter  with  the 
diaphysis. 

As  might  be  expected,  the  chief  growth  of  the  femur  taking  place  from  this 


366  HUMAN    ANATOMY. 

epiphysis,  a  number  of  cases  of  arrest  of  growth  have  been  reported.  The  disjunc- 
tion has  been  mistaken  for  a  dislocation  of  the  knee  or  a  supracondylar  fracture 
of  the  femur,  but  the  undisturbed  relations  of  the  condyles  and  the  head  of  the 
tibia  and  the  freedom  of  motion  in  the  knee-joint  serve  to  distinguish  it  from  the 
luxation,  while  the  fracture  is  rare  in  children,  and  presents  differential  signs  that 
will  be  mentioned  later  (page  644). 

Fractures  between  the  condyles  (intercondylar),  when  T-shaped,  as  they  often 
are,  are  thought  to  be  secondary  to  the  main  or  supracondylar  fracture, — i.e. ,  the 
shaft  breaks  above  the  condyles  and  the  force  continuing  splits  them  apart.  The 
line  of  the  latter  fracture  is  nearly  vertical  and  follows  the  intercondylar  notch, 
already  weakened  by  numerous  foramina  for  vessels.  The  proximity  of  the  popliteal 
vessels  has  resulted  in  grave  complications  from  pressure  or  from  rupture.  Either 
condyle  may  be  split  off  separately.  The  joint  is  necessarily  involved  in  all  these 
fractures,  and  rapid  distention  may  make  the  diagnosis  difficult.  The  X-rays  should, 
of  course,  be  employed  in  such  cases,  and  indeed  in  all  doubtful  fractures  of  the 
femur. 

Osteotomy  for  genu  valgum  may  be  done  through  an  incision  on  the  outer 
side  of  the  thigh — the  region  of  safety — about  two  inches  above  the  external  condyle. 
The  ilio-tibial  band  of  fascia  is  cut  ;  the  incision  passes  in  front  of  the  biceps  ;  when 
about  two-thirds  of  the  shaft  has  been  divided  by  the  osteotome,  the  remainder  will 
fracture  easily,  as  the  outer  part  of  the  bone  is  here  thicker  than  the  inner.  The 
operation  has  the  advantages  of  remoteness  from  the  epiphyseal  line,  from  important 
blood-vessels,  and  from  the  synovial  membrane  of  the  knee.  The  bone  is  divided 
at  a  narrow  part. 

Disease. — Infective  disease  of  the  upper  end  of  the  femur  usually  involves  the 
hip-joint,  even  when  it  begins  in  the  diaphysis,  the  epiphyseal  line  being  intra- 
articular. 

In  spite  of  the  protective  covering  of  muscles  surrounding  the  shaft,  it  is  not 
infrequently  the  subject  of  inflammation,  probably  as  a  result  of  the  great  strains  and 
numerous  traumatisms  to  which  it  is  subjected,  and  of  the  physiological  activity 
•necessitated  by  its  rapid  growth,  which  between  birth  and  maturity  is  proportionately 
nearly  twice  as  much  as  that  of  the  leg  and  more  than  twice  as  much  as  that  of  the 
whole  body.  Thus,  post-typhoidal  osteitis  attacks  the  femur  in  about  twenty-five 
per  cent,  of  the  cases  in  which  the  lower  extremity  is  involved,  and  more  frequently 
than  an)'  other  bone  except  the  tibia  and  ribs,  although  the  superficial  bones  of  the 
skeleton  are  involved  by  this  disease  three  and  a  half  times  more  frequently  than  the 
deep  bones. 

At  the  lower  end  of  the  femur,  disease  resulting  in  necrosis,  especially  of  the 
posterior  aspect,  often  requires  amputation,  as,  owing  to  the  thinness  of  the  perios- 
teum in  that  region,  there  is  scarcely  any  attempt  at  the  formation  of  an  involucrum 
(Rose). 

Exostoses  of  the  femur  are  not  uncommon,  especially  in  horsemen,  in  the  neigh- 
borhood of  the  tendon  of  the  adductor  longus — i.e. ,  at  the  upper  end  of  the  femur 
— and  occasionally  in  that  of  the  adductor  magnus  at  the  lower  end, — "rider's 
bones. ' ' 

The  great  comparative  frequency  with  which  sarcomata  attack  the  femur  is  in 
accord  with  the  general  rule  that  they  are  more  frequently  found  on  long  bones 
than  on  short  ones,  on  the  lower  limb  than  on  the  upper,  and  on  bones  near  the 
trunk  than  on  those  remote  from  it.  As  they  are  also  more  malignant  the  nearer 
they  approach  the  trunk,  these  tumors,  like  those  of  the  humerus,  are  clinically  more 
serious  than  those  of  the  distal  portions  of  the  extremity.  Both  central  and  sub- 
periosteal sarcomata,  but  especially  the  former,  have  a  predilection  for  the  ends 
of  the  bones  ;  but  whereas  they  affect  chiefly  the  upper  end  of  the  humerus  and  the 
lower  ends  of  the  radius  and  ulna,  in  the  inferior  extremity  they  are  most  often 
found  at  the  lower  end  of  the  femur  and  the  upper  ends  of  the  tibia  and  fibula,— that 
is,  at  the  ends  towards  which  the  nutrient  arteries  are  not  directed,  and  at  which 
epiphyso-diaphyseal  union  takes  place  latest  (page  272). 

Landmarks. — In  very  thin  persons  the  head  of  the  femur  can  sometimes  be 
felt  immediately  below  Poupart's  ligament  and  just  external  to  its  middle. 


THE    HIP-JOINT.  367 

The  greater  trochanter  is  almost  subcutaneous,  being  covered  by  the  aponeu- 
rotic insertion  of  the  upper  fibres  of  the  gluteus  maximus.  It  is  from  7.5  to  10  cen- 
timetres (three  to  four  inches)  below  the  crest  of  the  ilium.  In  the  erect  position 
it  is  slightly  anterior  to  and  farther  from  the  mid-line  than  the  mid-point  of  the 
crest.  It  is  visible  in  thin  persons,  and  assumes  abnormal  prominence  when  there 
has  been  wasting  of  the  gluteal  muscles,  as  the  gluteus  medius  and  minimus  nor- 
mally efface  the  hollows  between  it  and  the  ilium.  In  fat  or  muscular  persons 
the  fascial  attachments  to  the  trochanter  cause  a  visible  depression.  Its  upper 
border  is  on  a  level  with  the  centre  of  the  acetabulum  (so  that  Nelaton's  line  passes 
over  those  two  points),  is  nineteen  millimetres  (three-quarters  of  an  inch)  lower 
than  the  top  of  the  femoral  head,  and  is  almost  on  a  level  with  the  pubes.  The 
depression  immediately  beneath  it  corresponds  to  the  tendinous  lower  portion  of 
the  gluteus  maximus  close  to  its  insertion.  The  gap  between  it  and  the  iliac  crest 
is  bridged  over  by  the  upper  portion  of  that  part  of  the  fascia  lata  known  as  the 
ilio-tibial  band.  Relaxation  of  this  band  in  fracture  of  the  femoral  neck  can  be  both 
felt  and  seen  (Allis). 

The  three  gluteal  bursae  interposed  between  the  trochanter  and  the  gluteal 
muscles  may  become  enlarged,  especially  that  beneath  the  gluteus  maximus,  and 
obscure  the  outlines  of  the  trochanter.  This  condition  is  sometimes  mistaken  for 
hip-joint  disease,  as  the  thigh  is  usually  adducted  and  flexed  on  the  pelvis,  because 
abduction  and  extension  bring  into  action  the  gluteal  muscles,  and  thus  cause  painful 
pressure  on  the  bursa.  Inflammation  of  that  bursa  is  almost  always  the  result  of 
a  blow  upon  the  trochanter  ;  the  joint  movements  are  free,  there  is  no  referred  pain 
in  the  knee,  and  forcing  the  head  of  the  femur  against  the  acetabulum  by  pressure 
upon  the  knee  is  painless,  as  is  pressure  over  the  capsule  of  the  joint  below  Pou- 
part's  ligament. 

In  subcutaneous  osteotomy  of  the  neck  of  the  femur  the  incision  for  admission 
of  the  saw  is  made  about  one  inch  in  front  and  one  inch  above  the  top  of  the 
trochanter.  The  saw  cut  runs  parallel  with  Poupart's  ligament  and  is  about  2.5 
centimetres  (one  inch)  below  it. 

The  lesser  trochanter  cannot  be  felt. 

The  shaft  of  the  femur  is  deeply  situated  and  cannot  be  closely  approached 
for  palpation,  except  at  the  outer  side  of  the  lower  third  in  the  space  between  the 
biceps  and  vastus  externus. 

The  most  prominent  part  of  the  inner  rounded  surface  of  the  knee  is  the 
tuberosity  on  the  inner  condyle  of  the  femur.  Above  it  is  the  adductor  tubercle 
marking  the  tendinous  insertion  of  the  great  adductor  and  just  above  the  inner  end 
of  the  epiphyseal  line. 

The  external  condyle  is  subcutaneous. 

The  remaining  landmarks  in  this  region  will  be  considered  in  relation  to  the 
knee-joint  and  the  soft  parts  (page  671). 

THE  HIP-JOINT. 
This  is  a  ball-and-socket  joint.  The  socket  is  formed  by  the  acetabulum  with 
the  assistance  of  the  transverse  and  cotyloid  ligaments.  The  articular  facet  which 
bears  the  articular  cartilage  has  been  described.  The  notch  at  the  lower  part  of  the 
periphery  of  the  acetabulum  is  bridged  over  by  the  transverse  ligament1  (Fig. 
384),  a  collection  of  interlacing  fibres,  which  thus  completes  the  margin  of  the  socket. 
An  opening  is  left  below  it  through  which  vessels  and  nerves  pass  ;  from  its  sides 
the  round  ligament2  arises.  Some  fibres  of  the  transverse  ligament  mingle  with 
those  of  the  latter.  The  cotyloid  ligament3  (Fig.  384)  is  a  fibro-cartilaginous  rim, 
which  deepens  the  socket  overlapping  the  head  of  the  femur  until  the  cavity  embraces 
more  than  half  a  sphere.  It  is  attached  to  the  edge  of  the  acetabulum,  and,  where 
this  is  wanting,  to  the  transverse  ligament.  The  cotyloid  ligament  is  about  five 
millimetres  broad  at  the  attached  base,  and  narrows  to  a  sharp  border,  so  as  to  be 
triangular  on  section.  The  distance  from  the  base  to  the  free  edge  is  very  nearly 
one  centimetre  at  the  top  of  the  joint,  where  it  is  greatest.  The  non-articular  space 
at  the  bottom  of  the  joint  is  filled  with  fat  and  by  the  round  ligament  nearly  up  to 

1  Lig.  transversum  acetabuli.     •  Lig.  teres  femoris.     :ILabrurn  glenoldale. 


368 


HUMAN  ANATOMY. 


the  level  of  the  articular  surface.  These  structures  are  covered  by  synovial  mem- 
brane. The  head  of  the  femur  is  covered  by  articular  cartilage,  except  at  the  de- 
pression for  the  insertion  of  the  round  ligament. 

The  bones  are  connected  by  the  capsule  and  the  round  ligament. 

The  capsule1  (Figs.  385,  386)  is  a  fibrous  envelope  enclosing  the  joint, 
strengthened  by  certain  bands,  which  are  inseparable  parts  of  its  substance,  though 
they  have  names  of  their  own.  The  capsule  is  attached  to  the  cotyloid  ligament  and 
to  the  periphery  of  the  acetabulum  just  outside  of  the  origin  of  the  latter.  In  this 
respect  there  is  much  uncertainty  ;  the  capsule  always  rises  from  the  free  edge  of  the 
transverse  ligament,  and,  as  a  rule,  elsewhere  outside  the  base  of  the  cotyloid  ;  but  it 
may  in  parts  arise  from  its  edge.  This  applies  to  the  capsule  examined  from  within  ; 
externally  the  fibres  extend  a  considerable  distance  from  the  border  of  the  joint. 
They  almost  conceal  the  opening  at  the  notch  below  ;  above,  they  partly  bridge 
over  the  reflected  tendon  of  the  rectus  and  partly  join  its  deeper  fibres.     The  cap- 


Articular  surfao 


Fat  in  acetabular  fossa 


Tuberosity  of  ischium 


Cotyloid  ligament 
Stump  of  round  ligament 
Transverse  ligament 


Capsule  reflected 


Socket  of  right  hip-joint.     The  capsule  has  been  divided  near  its  origin  and  reflected 


sule  extends  to  the  base  of  the  anterior  inferior  spine  of  the  ilium  and  some  distance 
on  the  obturator  crest.  The  attachment  to  the  femur,  seen  from  without,  runs  from 
the  top  of  the  greater  trochanter,  just  above  the  superior  cervical  tubercle,  down  the 
spiral  line  to  the  level  of  the  top  of  the  lesser  trochanter,  where  the  line  of  insertion 
turns  in  for  about  two  centimetres,  when  it  passes  upward  along  the  back  of  the 
neck,  less  than  half-way  from  the  head  to  the  posterior  intertrochanteric  line,  till, 
reaching  the  top  of  the  neck,  it  gradually  passes  outward  to  the  starting-point- 
Thus  the  capsule  stops  about  a  finger' s-breadth  short  of  the  lesser  trochanter,  in- 
cludes less  than  half  the  hind  side  of  the  neck,  and  stops  short  of  the  digital  fossa 
and  of  the  inner  side  of  the  top  of  the  greater  trochanter.  Posteriorly,  it  is  not 
truly  inserted  into  the  neck,  but  simply  crosses  it,  its  position  being  determined 
by  the  line  of  reflection  of  the  synovial  membrane.  The  general  direction  of  the 
fibres  is  longitudinal  ;  but  the  posterior  fibres,  when  the  femur  is  strongly  extended, 
assume  the  form  of  a  twisted  band  running  from  the  back  of  the  socket  outward 

1  Capsula  articularis. 


THE   HIP-JOINT. 


369 


and  upward  across  the  back  of  the  neck  to  the  top  of  the  greater  trochanter  (Fig. 
387).  Moreover,  beneath  the  longitudinal  layer  there  is  a  sling  of  circular  fibres, 
the  zona  orbicularis,  starting  from  the  anterior  inferior  spine  of  the  ilium  and  pass- 
ing behind  the  neck  to  return  to  the  same  point.  It  lies  near  the  head  of  the 
femur,  completely  concealed  by  the  longitudinal  fibres.  It  is  isolated  only  by  a 
rather  artificial  dissection. 

The  capsule  varies  much  in  thickness  in  different  places  ;  thus,  it  is  very  weak 
behind  and  very  strong  in  front.     It  is  strengthened  by  three  collections  of  accessory 

Fig.  385. 


Ilio-femoral  ligament 


Right  hip-joint,  anterior  aspect. 

fibres.  Much  the  most  important  is  the  ilio-femoral  ligament '  (Fig.  3S5),  a  thick 
triangular  expansion,  intimately  fused  with  the  capsule,  arising  by  its  apex  from  the 
lower  part  of  the  anterior  inferior  spine  of  the  ilium  and  from  the  bone  below  and 
behind  it  above  the  lip  of  the  acetabulum,  and  extending  by  its  base  from  the 
superior  cervical  tubercle  to  the  level  of  the  lesser  trochanter.  The  borders  of  this 
are  often  particularly  strong,  and  are  spoken  of  as  the  outer  and  inner  limbs  of  the 
ligament.  A  weak  space  is  sometimes  seen  between  them  near  the  insertion,  whence 
it  has  been  called  by  Big-elow  the  Y-ligament  from  a  resemblance  to  an  inverted  \ . 


1  Lig.  iliofemoralc. 
2*1 


3?o 


HUMAN  ANATOMY. 


Striking  examples  of  this  are  generally  artificial  productions.  The  beginning  of 
the  ilio-femoral  ligament  covers  the  outer  part  of  the  head.  The  capsule  is  much 
thinner  over  the  inner  part  of  the  head,  and  is  covered  by  the  bursa  under  the  ilio- 
psoas, which  often  communicates  with  the  joint.  The  pubo-femoral  liga- 
ment1 (Fig.  385)  is  a  slender  band  of  fibres,  thickening  the  under  side  of  the 
capsule,  extending  from  the  lowest  point  of  the  capsular  insertion  on  the  spiral 
line  to  the  outer  end  of  the  obturator  crest.  It  is  rarely  very  evident.  The 
ischio-femoral  ligament2  (Fig.  387)  is  a  strong  but  ill-defined  bundle  at  the  back 
of  the  joint,  extending  from  the  ischial  origin  of  the  capsule  to  the  top  of  the  digital 
fossa.  The  capsule  is  further  supported  by  muscles  and  by  bands  of  fibrous  tissue, 
generally  expansions  from  tendons  or  fascia?.      Morris  describes  a  band  on  the  upper 

Fig.  386. 


Cotyloid  ligam 


Round  ligament 


Obturator  membrane 


Frontal  section  through  right  hip-joint.     The  femur  has  been  allowed  to  fall  from  the  socket. 


anterior  aspect,  passing  between  the  reflected  tendon  of  the  rectus  and  the  highest 
origin  of  the  vastus  externus,  which  is  sometimes  very  strong,  but,  in  our  opinion, 
inconstant.  The  relation  of  the  ilio-psoas  has  been  mentioned.  Fibres  are  received 
at  the  upper  outer  part  from  the  gluteus  minimus.  The  obturator  internus  and  the 
gemelli  are  close  against  it  behind,  and  the  obturator  externus  behind  and  below. 
We  have  seen  a  tendinous  band  beneath  the  tendon  of  the  obturator  internus  quite 
distinct  from  the  capsule  internally  and  fused  with  it  externally.  It  may  have  been 
a  reduplication  of  that  muscle  or  an  extra  ischio-femoral  ligament. 3 

The  round   ligament   (ligamentum  teres)    (Figs.    384,    389)  is  a  weak   band 
of  fibrous  tissue,  containing  vessels  and  nerves,  surrounded  by  synovial  membrane, 
lying  under  the  fat  in  the  deep  non-articular  hollow  of  the  socket,  connecting  the 
3  Journal  of  Anatomy  and  Physiology,  vol.  viii.,  1S74. 

1  lag.  pubocapsulare.     2Lig.  ischiocapsulare. 


THE   HIP-JOINT. 


37i 


rim  of  the  acetabulum  with  the  head  of  the  femur.  The  origin  is  from  each  edge 
of  the  notch  and  from  the  deeper  fibres  of  the  transverse  ligament,  the  insertion 
into  the  deepest  part  and  upper  edge  of  the  depression  in  the  femoral  head.  A 
fresh  specimen,  especially  from  a  child,  shows  the  lower  half  of  the  depression 
becoming  gradually  shallower  and  forming  a  groove  in  which  the  upper  part  of 
the  band  rests,  which,  covered  with  the  synovial  membrane,  completes  the  spheri- 
cal shape  of   the  head.     Vessels  run  along  the  round  ligament,  which  in  infancy 


Fig.  387. 


Reflected  tendon  of  rectus 


Back  of  capsule 


Tuberosity  of  ischium  — 


Ischio-femoral 
ligament 


Right  hip-joint,  posterior  aspect. 

and  early  childhood  nourish  the  head,  but  in  the  adult  they  often  do  not  enter  the 
bone. 

This  ligament  is  sometimes  wanting.  According  to  Moser,'  this  defect  is  only  in 
the  old,  and  is  to  be  looked  upon  as  a  degenerative  change.  Comparative  anatomy 
teaches  that  it  is  the  analogue  of  a  part  of  the  capsule.  It  is  remarkable  that  it  is 
wanting  in  certain  species  closely  allied  to  others  possessing  it.  Besides  the  two 
extremes  of  complete  freedom  within  the  joint  and  of  total  absence,  the  ligamentum 
teres  of  animals  is  also  found  in  an  imperfectly  developed  condition  as  a  fold  along 
1  Schwalbe's  Morpholog.  Arbeiten,  Bd.  ii.,  1893.     This  paper  gives  the  literature. 


372 


HUMAN    ANATOMY. 


the  side  of  the  cavity  between  the  notch  in  the  acetabulum  and  the  head  of  the  bone. 
Many  of  the  statements  of  its  absence  require  confirmation  by  more  observations. 
Thus,  among  the  anthropoid  apes  it  seems  to  be  generally  present  in  all  but  the 
ourang.  In  this  animal,  though  usually  wanting,  it  has  been  found  in  a  rudimentary 
condition.  Meckel  declared  that  it  was  absent  in  the  gibbon,  but  we  believe  no 
other  observer  has  had  a  similar  experience.  It  is  very  strongly  developed  in  the 
ostrich,  but  is  wanting  in  the  rhea  (the  American  ostrich)  and  probably  in  the  casso- 
wary. Sutton '  considers  it  as  the  tendon  of  the  pectineus  muscle  which  has  become 
separated  through  skeletal  modifications.  Sutton  relies  a  good  deal  on  the  condition 
in  the  horse  for  support  in  his  argument.  He  found  it  consisting  of  two  bands, — 
one  within  the  joint,  apparently  the  usual  ligament,  and  another  passing  out  of  the 
cavity  to  the  linea  alba  at  its  junction  with  the  pubes,  which  he  calls  the  pubo- 
femoral portion.  The  pectineus  muscle  arises  in  part  from  this  latter  portion. 
Sutton  gives  a  table  telling  the  story  of  the  structure  according  to  his  theory.  In 
sphenodon  (a  lizard)  the  tendon  of  the  ambiens,  representing  the  pectineus,  passes 


Fig.  388. 

Cotyloid  ligament    Bursa  beneath  ilio-psoas 


Round  ligament 


Front  of  capsule 


Spine  of  ischium— ,7"-^ 


Cotyloid  ligament  Tendon  of  obturator  externus 

Horizontal  section  through  right  hip-joint. 


into  the  joint  to  the  head  of  the  femur  ;  in  the  ostrich  the  ligament  is  continuous 
with  the  tendon  by  means  of  connective  tissue  ;  in  the  horse  the  two  parts  are 
distinct  ;  and  in  man  the  external  part  is  wanting.  The  structure  is  evidently  a  very 
variable  one. 

The  synovial  membrane  (Figs.  386,  388)  lines  the  capsule,  covers  the  cotyloid 
and  transverse  ligaments,  surrounds  the  ligamentum  teres,  and  covers  the  fat  in  the 
fossa  of  the  acetabulum.  It  is  reflected  from  the  femoral  attachment  of  the  capsule 
onto  the  neck,  which  it  invests  to  the  border  of  the  articular  cartilage.  This  reflected 
part  presents  certain  folds  caused  by  fibres  from  the  capsule  running  up  along  the 
neck,  called  retinacula  (Fig.  390).  There  are  generally  three  chief  ones  :  a  superior, 
starting  from  the  superior  cervical  tubercle  and  running  along  the  upper  border,  or 
backward  across  the  neck  to  the  head  of  the  femur  ;  a  middle,  from  near  the  inferior 
cervical  tubercle  along  the  front  of  the  lower  border  of  the  neck  ;  and  an  inferior, 
from  near  the  lesser  trochanter  along  the  lower  side.  Any  of  these  may  be  more 
or  less  free  from  the  neck. 

1  Journal  of  Anatomy  and  Physiology,  vol.  xvii.,  1883. 


THE    HIP-JOINT. 


373 


The  retinacula }  probably  strengthen  the  union  of  the  head  and  neck  before  the 
union  of  the  epiphyses. 

Movements. — As  a  ball-and-socket  joint,  the  hip  permits  motion  on  an  indefi- 
nite number  of  axes.  If  the  ball  were  on  the  end  of  a  straight  rod,  we  could  assume 
that  flexion  and  extension  occur  on  a  transverse  axis  and  adduction  and  abduction 
on  an  antero-posterior  one,  but  the  inclination  of  the  shaft  of  the  femur  and  that  of 
the  neck  in  two  directions  complicates  the  problem,  so  that  accurate  analysis  of  the 


Fig.  389. 


Crest  of  ilium 


Head  of  femur 


Symphysis  pubis 


Obturator  membrane 


all  of  the  hip-joint  socket  has  been  cut  away,  exposing  the  head  and  round  ligament  without  disturbing 
the  capsule. 


movements  is  practically  impossible.  Rotation  is  motion  on  a  vertical  axis  which 
is  generally  assumed  to  pass  through  the  head  and  the  intercondylar  notch.  This 
must,  of  course,  vary  with  the  shape  of  the  bone.  Although  the  angular  motions  in 
the  four  conventional  planes  are  far  from  simple,  they  may  be  assumed  to  be  so 
for  practical  purposes.  Flexion  is  stopped  in  life  by  the  contact  of  the  thigh  and 
the  trunk  before  the  limits  of  the  motion  are  reached.      Extension  is  limited  by  the 

1  Fawcett :  Journal  of  Anatomy  and  Physiology,  vol.  xxx.,  1896. 


374 


HUMAN    ANATOMY. 


resistance  of  the  strong  ilio-femoral  ligament,  excepting  the  outer  band.      Abduction 
is  limited,  the  thigh  being  extended,  by  the  pubo-femoral  ligament  and  perhaps  by 

the    inner    limb   of    the    ilio-femoral. 
Fig.  390.  When  the  thigh  is  flexed,  the  latter  is 

Round  ligament  certainly  relaxed,  and  the  strain  comes 

on  the  pubo-femoral  and  a  part  of  the 
capsule  behind  it, — a  very  weak  re- 
gion. Adduction  with  a  straight  thigh 
is  limited  by  the  outer  limb  of  the 
ilio-femoral,  the  top  of  the  capsule, 
and  Morris's  band  from  the  rectus 
tendon  to  the  vastus  externus,  if  it 
be  present.  After  moderate  flexion 
is  passed,  the  ilio-femoral  is  relaxed. 
Outward  rotation,  the  thigh  being 
Capsule  straight,  is  checked  by  the  ilio-femoral, 
especially  by  its  inner  band.  As  the 
thigh  is  flexed  the  inner  band  is  re- 
laxed and  the  outer  is  at  first  tense, 
but  both  are  relaxed  as  flexion  reaches 
about  450.  Morris's  band  now  be- 
comes tense,  and  as  flexion  becomes 
extreme  the  round  ligament  is  tense 
also,  unless  the  thigh  be  abducted, 
when  it  is  completely  relaxed.  In- 
ward rotatioyi  is  checked  by  the  ischio- 
femoral ligament  in  any  position. 

The  most  important  part  of  the 
capsule  is  the  ilio-femoral  band,  which 
is  extremely  strong  and  prevents  over- 
extension. It  is  an  essential  element 
in  maintaining  the  upright  position. 
The  round  ligament  has  probably  no 
mechanical  function,  though  it  can  be 
made  tense  by  flexing,  and  at  the  same 
time  either  adducting  the  femur  or 
rotating  it  outward.  It  is  too  weak  to  be  of  any  real  use  as  a  restraint.  Probably 
its  chief  usefulness  is  to  carry  vessels  to  the  head  of  the  femur  in  childhood. 


Right  femur  seen  from  i 

synovial  membrane  < 


PRACTICAL   CONSIDERATIONS. 

The  greater  security  of  the  hip-joint,  as  compared  with  the  shoulder-joint,  is 
due  to  the  depth  of  the  acetabular  cavity  ;  to  its  reinforcement  by  the  cotyloid  fibro- 
cartilage  ;  to  the  attachments  of  the  ilio-psoas,  gluteus  minimus,  and  vastus  externus 
to  the  capsule  ;  but  chiefly  to  the  thickenings  of  the  capsule  itself,  which  are  described 
as  the  ilio-,  ischio-,  and  pubo-femoral  ligaments. 

The  greatest  pressure  upon  the  capsule  in  all  ordinary  positions  is  in  an  upward 
and  outward  direction,  or  upon  the  anterior  surface  of  the  capsule,  as  when,  under 
the  influence  of  the  powerful  extensors,  the  pelvis  and  trunk  tend  to  roll  backward 
upon  the  thighs  in  the  erect  posture.  The  tension  and  pressure  are,  of  course, 
greatest  near  the  pelvic  attachment  of  the  capsule  where  the  head  will  impinge  upon 
it  with  the  most  advantage  as  to  leverage.  The  capsule  is  especially  fitted  to  resist 
this  pressure. 

If  two  lines  be  drawn,  one  from  the  anterior  inferior  iliac  spine  to  the  inner 
border  of  the  femur  near  the  lesser  trochanter,  the  other  from  the  anterior  part  of 
the  groove  for  the  external  obturator  {i.e. ,  the  upper  part  of  the  tuberosity  of  the 
ischium)  to  the  digital  fossa,  all  the  ligament  outside  and  above  these  lines  is  very 
thick  and  strong  ;  whereas,  all  to  the  inner  side  and  below,  except  along  the  narrow 
pubo-femoral  band,    is   very   thin  and   weak,  so   that  the  head  of  the  bone  can  be 


PRACTICAL    CONSIDERATIONS  :    THE    HIP-JOINT. 


375 


Fig 


Diagra 


ndicating  strong 
joint 


weak  portions  of 
(Allis.) 


apsule  of  hip- 


seen  through  it  (Morris).     Fig.  391  represents  this  diagrammatically.      In  addition, 

the  greater  elevation  and  thickness  of  the  upper  and  outer  rim  of  the  acetabulum, 

and  the  pressure  against  the  trochanter  exerted  by  the  ilio-tibial  band  of  the  fascia 

lata  (Allis)  in  adduction  of  the  thigh  (which  means  an  outward  movement  of  the 

upper  extremity  of  the  femur) ,  should 

be  mentioned  among  the  factors  that 

resist    displacement.      The    ligamen- 

tum    teres   is  of    little  value,    as    its 

bony  attachment  to  the  femoral  head 

is    easily   separated  by  a   force  less 

than    that    required    to  rupture    the 

ligament. 

A  line  drawn  from  the  anterior 
spine  to  the  tuber  ischii  will  approxi- 
mately bisect  the  acetabulum  and 
will  divide  each  half  of  the  pelvis 
into  two  planes,  the  pubo-ischiatic, 
inner  or  anterior,  and  the  ilio-ischi- 
atic,  outer  or  posterior  (Fig.  392). 
When  the  head  of  the  femur  escapes 
from  the  acetabulum  it  must  lie  on 
the  surface  of  one  or  other  of  these 
planes.  All  dislocations  are,  there- 
fore, either  (1)  outward — i.e.,  pos- 
terior— or  (2)  inward — i.e. ,  anterior. 

1.  Outward  or  Posterior  Luxations. — Traumatisms  in  which  the  force  is 
expended  upon  the  region  of  the  hip  result,  as  a  rule,  in  children  in  epiphyseal  sep- 
aration (page  361),  in  old  persons  in  fracture  of  the  neck  of  the  femur  (page  363). 
In  173  cases  of  dislocation  of  the  hip,  138  were  between  fifteen  and  forty-five  years 
of  age. 

In  practically  all  positions  of  the  hip  in  which  luxation  is  probable  the  force 
acts  through  some  form  of  leverage  which  brings  the  short  arm  of  the  lever — always 

the  head  and  neck  of  the  femur — 
against  a  weak  portion  of  the  cap- 
sule. If  it  does  this  with  the  aid  of 
a  bony  fulcrum,  the  power  is  ex- 
erted to  the  greatest  possible  ad- 
vantage. Thus,  in  hyperextension 
of  the  thigh,  the  acetabular  rim  acts 
as  a  fulcrum,  but  the  head  of  the 
bone  is  brought  against  the  anterior 
part  of  the  capsule, — the  ilio-femoral 
ligament, — which  is  usuallystronger 
than  the  bone  itself.  Hyperflexion 
is  arrested  by  the  contact  of  the 
soft  parts  of  the  front  of  the  thigh 
with  the  abdomen  ;  hyperadduction 
by  the  contact  of  the  shaft  with  the 
pubes.  Hyperabduction,  however, 
brings  the  greater  trochanter  against 
the  prominent  outer  lip  of  the  ace- 
tabulum, while  the  head  is  carried 
downward  against  the  thin  inner 
and  lower  part  of  the  capsule  :  the 
ilio-femoral  and  ischio-femoral  liga- 
ments are  relaxed,  and  the  weak  pubo-femoral  ligament  offers  but  little  resistance  ; 
the  head,  being  opposite  the  shallowest  part  of  the  acetabulum,  projects  half  its 
bulk  out  of  that  cavity;  the  weight — i.e. ,  the  resistance  of  the  capsule — is  very 
close  to  the  fulcrum,  greatly  increasing  the  power  of  the  leverage. 


Fig. 


376 


HUMAN    ANATOMY. 


The  ilio-femoral  ligament  may,  in  cases  in  which  the  thigh  is  adducted  and 
rotated  inward  at  the  time  of  application  of  the  force,  take  the  place  of  the  acetabu- 
lar rim  as  a  fulcrum.      In  that  position  it  is  wound  round  the  neck  of  the  femur,  and 

Fig.  393. 


^^^m.:£J 


Luxation  of  the  head  of  the  femur  onto  the  dorsum  of  the  ilii 


when  the  flexed  leg  is  used  as  a  crank  the  head  may  be  made  to  burst  through  the 
lower  and  posterior  part  of  the  capsule. 

Allis '  has  shown  that  these  conditions,  easily  demonstrated  experimentally,  are 
reproduced  in  many  forms  of  accident.      It  is  obvious  that  they  are  all  favorable  to 
a  downward  dislocation,  and  this,  as  is  the  case  with  the  humeral  head,  is  the  direc- 
tion  primarily   taken    in    the 
vast  majority  of   these  luxa- 
Fig.  394.  tions.      If  the  thigh  has  been 

rotated  inward,  either  in  ad- 
duction or  abduction,  the 
head  of  the  bone  will  pass 
outward  and  backward  and 
rest  behind  the  acetabulum 
on  some  part  of  the  outer  or 
posterior  plane  of  the  pelvis. 
If  it  lies  upon  the  ilium,  a 
little  above  the  acetabulum, 
it  constitutes  the  ' '  iliac' '  dis- 
location,— "above  the  obtu- 
rator tendon  ;"  if  upon  the 
ischium,  on  a  level  with  or 
a  little  below  the  acetabulum, 
it  is  the  "  ischiatic"  or  "sci- 
atic" dislocation,  —  "  below 
the  obturator  tendon."  This 
obturator  internus  tendon 
sometimes  interposes  an  ob- 
stacle to  the  upward  passage 
of  the  head,  but  its  impor- 
tance in  this  respect  has  been  exaggerated.  The  degree  of  flexion  of  the  limb  at 
the  time  of  the  accident  is  more  likely  to  determine  the  level  at  which  the  head  rests. 

1  Reduction  of  Dislocations  of  the  Hip,  Philadelphia,  1S96. 


^ 


^508 


PRACTICAL   CONSIDERATIONS:    THE   HIP-JOINT. 


377 


In  both  positions  the  ilio-femoral  ligament,  which  is  almost  invariably  intact, 
has  now  become  the  fulcrum.  As  the  short  arm  of  the  lever — the  head  and  neck — 
has  moved  outward,  the  long  arm — the  shaft  of  the  femur — must  move  inward  ;  hence 
adduction  is  present  in  all  cases  of  outward  luxation  in  which  the  Y-ligament  is  not 
lacerated,  and  is  persistent  because  the  head  lying  in  contact  with  the  outer  wall  of 
the  pelvis  cannot  be  moved  inward.  Rotation  inward,  which  is  also  present  and 
persistent,  is  due  to  the  same  tension  upon  the  Y-ligament.  This  explains  the 
usual  position  of  the  limb  with  the  line  of  the  femur  crossing  that  of  the  opposite 
thigh  a  little  above  the  knee  and  the 

great  toe  resting    upon   the  instep  of  Fig.  395. 

the  sound  foot.  Flexion  of  the  thigh 
is  maintained  partly  by  the  tension  on 
the  ilio-psoas. 

The  muscles  have  a  very  minor 
part  in  the  production  or  maintenance  $\V 

of  the  characteristic  deformity.  The 
external  rotators,  the  glutei  and  the 
pectineus,  are  often  lacerated.  There 
is  shortening,  and  the  trochanter  is 
above  the  level  of   Nelaton's  line. 

In  the  rare  cases  in  which  the  Y- 
ligament — or  its  outer  limb — is  torn, 
outward  luxation  with  neither  adduc- 
tion nor  inversion  becomes  possible. 

2.  Inward  or  Anterior  Luxations. 
— These  always  occur  with  the  thigh 
in  abduction,  and  are  favored  by  out- 
ward rotation,  which  carries  the  head 
towards  the  lower  a7iterior  part  of  the 
capsule.  If  it  passes  upward  and  rests 
on  the  body  of  the  pubis,  it  constitutes 
the  "pubic"  luxation  (Figs.  395, 
396)  ;  if  downward,  it  is  in  or  opposite 
the  thyroid  foramen,  and  is  often  called 
an  "obturator"  or  "thyroid"  luxa- 
tion (Figs.  397,  398).  The  ilio-femoral 
ligament  again  becomes  the  fulcrum  ; 
the  short  arm  of  the  lever  has  been 
carried  inward,  necessitating  a  corre- 
sponding outward  movement  of  the 
long  arm  ;  hence  abduction  is  present. 
The  exaggerated  rotation  outward  is 
maintained  by  the  tension  of  the  liga- 
ment ;  hence  the  eversion  of  the  limb. 
Neither  abduction  nor  eversion  can  be 
overcome,  because  the  head  is  held 
firmly  against  the  pubo-ischiatic  pelvic 
plane.  The  gracilis,  pectineus,  and  ad- 
ductors are  apt  to  be  torn  ;  the  stretch- 
ing of  the  ilio-psoas,  the  glutei,  and  the 
muscles  inserted  into  the  greater  trochanter  aids  in  maintaining  both  the  flexion  and 
the  eversion.  The  ilio-tibial  band  of  fascia  will  be  found  relaxed  ;  the  trochanteric 
prominence  disappears  as  the  trochanter  approaches  the  mid-line  and  is  in  a  measure 
sunk  in  the  socket.  There  will  be  shortening  on  measurement  from  the  anterior 
superior  spine  to  the  condyle  ;  the  head  of  the  femur  will  be  unduly  prominent  in 
the  pubic  variety. 

With  the  patient  in  dorsal  decubitus,  it  will  be  evident  that  the  acetabula  are 
situated  on  a  horizontal  plane  about  midway  between  the  pubes  and  the  sacrum. 
From  this  level  the  pelvis  slopes  upward  to  the  symphysis  and  downward  to  the 


Luxation  of  the  head  of  the  femur  onto  the  pubi; 


378 


HUMAN    ANATOMY. 


sacro-iliac  junction.  It  is  obvious  that  no  anterior  dislocation  can  be  below  the  bi- 
acetabular  line  and  no  posterior  dislocation  can  be  above  it. 

As  the  femur  is  about  equal  in  length  to  the  tibia  and  tarsus,  if  the  head  is  in 
the  socket  the  foot  will  be  on  the  acetabular  level  when  the  thigh  is  vertical  and  the 
knee  flexed.  If  the  head  is  dislocated  anteriorly,  the  foot  will  be  on  a  higher 
level  ;  if  posteriorly,  the  foot  will  be  lower,  and  may  even  touch  the  surface  on 
which  the  patient  lies.  There  will  be  corresponding  changes  in  the  level  of  the 
knees  (Allis). 

The  femoral  vessels  are  not  often  injured  in  hip  luxations,  because  they  lie 
above  the  joint  and  luxations  are  always  primarily  downward  ;  and  because,  as  the 
head  approaches  them  in  the  inward  variety  only,  and  as  for  the  production  of  that 
variety  abduction  is  necessary,  the  muscles  beneath  them — the  pectineus  and  ilio- 
psoas— are  put  upon  the  stretch  and  the  vessels  are  lifted  out  of  harm's  way. 

The  relations  of  the  sciatic  nerve  to  these  injuries  are  of  great  importance.  The 
nerve,  is  in  close  relation  to  the  hamstring  muscles,  especially  to  the  biceps.      These 

structures  are  made  tense 


Fig.  396. 


and  are  stretched  across 
the  neck  of  the  femur  pos- 
teriorly by  flexion  of  the 
thigh  on  the  pelvis,  espe- 
cially if  the  leg  is  also 
extended  on  the  thigh,  so 
that  the  origin  and  inser- 
tion of  the  hamstring  mus- 
cles are  separated.  If,  in 
a  dislocation,  the  head  of 
the  femur  originally  lies  on 
the  anterior  plane  of  the 
pelvis,  and  either  by  the 
force  producing  the  dis- 
placement (as  is  commonly 
the  case),  by  the  action  of 
muscles,  or  during  efforts 
at  reduction  is  made  to  pass 
to  the  posterior  plane,  it 
must  traverse  the  narrow 
space  between  the  sciatic 
nerve  and  hamstrings  and 
the  edge  of  the  acetabu- 
lum. The  nerve  is  thus 
very  apt  to  be  bruised  and 
stretched  and  separated 
somewhat  from  the  biceps 
tendon.  Later,  if  replace- 
ment by  "  circumduction"  is  attempted,  the  head  may  pass  beneath  the  nerve, 
which  will  then  be  tightly  stretched  over  the  front  of  the  neck,  will  prevent  full 
extension  of  the  thigh,  and  will  cause  continued  pain  and  disability.  Other  com- 
plications associated  with  the  nerve  may  occur,  and  have  been  fully  demonstrated 
by  Allis,  whose  excellent  experimental  and  clinical  work  forms  the  basis  for  the  fore- 
going summary  of  the  anatomy  of  hip  luxations. 

In  reduction  of  posterior  dislocations  by  the  method  of  circumduction  the 
thigh,  which  is  already  flexed,  adducted,  and  inverted  by  the  agencies  above 
described,  is  still  further  flexed  and  adducted  and  lifted  upward  to  relax  the  ilio-psoas 
and  to  bring  the  head  of  the  bone  near  the  margin  of  the  acetabulum  ;  it  is  then 
abducted,  tightening  the  inner  band  of  the  ligament,  and  everted,  tightening  the  outer 
band  and  converting  the  femoral  attachment  of  the  whole  ligament  (but  chiefly  of 
its  outer  limb)  into  a  fulcrum  around  which,  as  a  centre, — the  abduction  and  eversion 
being  continued  into  circumduction, — the  head  of  the  bone  sweeps,  skirting  the 
lower   edge  of  the  acetabulum,  and  finally,  by  extensioji  of  the  thigh,  re-entering 


Relation  of  the  head  of  the  fem 


PRACTICAL    CONSIDERATIONS  :    THE    HIP-JOINT. 


379 


that  cavity  at  the  point  where  it  emerged.      The  whole  movement  is  made  up  of  the 
successive  steps  of  flexion,  adduction,  abduction,  eversion,  and  extension. 

In  reduction  of  anterior  dislocations  some  of  the  steps  of  the  procedure  are 
reversed, — i.e.,  the  movement  consists  of  flexion,  abduction,  adduction,  inversion, 
and  extension,  in  the  order  mentioned.  The  inner  limb  of  the  ligament  is  then  of 
chief  importance  as  a  fulcrum.  The  objection  to  this  method  in  both  cases  is  the 
danger  to  the  sciatic  nerve,  already  pointed  out,  and  also  to  the  femoral  vessels. 

Allis's  methods  of  reduction  are  intended  to  avoid  this  danger.  He  endeavors 
to  cause  the  head  to  retrace  accurately  the  path  by  which  it  left  the  socket.  In  a 
posterior  dislocation  the 

head  has  usually  left  the  Fig.  397. 

acetabulum  in  a  down- 
ward direction,  has  fallen 
below  the  socket,  and  has 
passed  outward  around 
the  edee  of  the  acetabu- 


K\|  ■ 


I 


lum  to  its  new  position  ; 
the  limb  has  then  fallen 
into  partial  extension  by 
its  own  weight.  Thus 
there  are  three  steps, 
which,  naming  them  in 
their  reverse  order,  are  : 
3,  extension  ;  2,  motion 
outward  ;  1,  motion 
downward.  The  steps 
of  his  method  are  accord- 
ingly :  1,  flexion  ;  2,  ro- 
tation of  the  head  inward 
(by  carrying  the  leg 
out),  placing  it  where  it 
was  immediately  after 
leaving  the  acetabulum  ; 
3,  lifting — to  bring  the 
head  to  the  level  of  the 
socket  —  and  extension 
(using  the  ilio-femoral 
ligament,  which  then  be- 
comes tense,  as  a  ful- 
crum, and  aided  by  the 
upward  pressure  of  the 
thumbs  of  an  assistant), 
carrying  the  head  up- 
ward into  the  socket. 

In  the  reduction  of 
anterior  dislocations  the 
anatomical  and  mechani- 
cal principles  involved 
are  the  same.  In  those 
dislocations  the  head  has 
left  the  socket  by  tearing 

the  capsule  on  its  inner  margin,  and  has  passed  inward  to  the  pubo-ischiatic  plane  ; 
the  limb  representing  the  other  end  of  an  inflexible  lever  must  move  in  the  opposite 
direction,  or  outward  ;  and  as  it  falls  a  little  downward  by  its  own  weight,  the  head 
rises  slightly.  To  restore  it,  reversing  these  steps,  flex  to  a  perpendicular,  lowering 
the  head  somewhat  ;  make  traction  on  the  limb,  drawing  the  head  outward;  and 
then,  the  head  being  fixed  by  the  hands  of  an  assistant,  adduct  and  extend  the  thigh, 
causing  the  head  to  enter  the  socket. 

By  these  methods  reduction  of  dislocation  complicated  with  fracture  of    the 


Luxation  of  the  head  of  the  femur  into  the  obturator  foramen. 


38o 


HUMAN    ANATOMY. 


femur  becomes  possible  because  of  the  firm  connection  between  (a)  the  base  of  the 
neck  and  the  acetabulum  through  the  unruptured  portion  of  the  capsule,  and  (&) 
the  two  fragments  through  the  attachment  of  muscles  along  the  linea  aspera. 
These  connections  enable  the  limb  to  be  used  for  traction,  although  the  fracture 
quite  precludes  the  employment  of  circumduction  and  rotation. 

Allis  summarizes  the  principles  of  his  method  by  saying  that  the  cardinal  rule 
applicable  to  every  form  of  dislocation  of  the  hip  is  :  draw  the  head  in  the  direction  of 
the  socket ;  apply  a  fulcrum  at  the  upper  part  of  the  lever  ;  pry  the  head  into  the 
socket. 

The  old  view  that  the  opening  in  the  capsule  was  often  a  slit  which  required 
enlargement  before  the  head  could  be  replaced  has  been  shown  (Allis  and  Morris) 
to  be  fallacious.  The  inelastic  character  of  the  capsular  fibres,  the  globular  shape 
of  the  femoral  head,   and  the  suddenness  of  application  of  the  force  (preventing 

stretching)    make   the  rent  in  every 


Fig.  398. 


case  as  large  as  the  head  ;  it  is  not 
infrequently  larger.  If,  however,  it  is 
situated  near  the  femoral  attachment 
of  the  capsule,  it  may  leave  a  cuff  of 
the  latter  hanging  from  its  pelvic  ori- 
gin over  the  acetabulum,  and  offering 
a  serious,  if  not  insuperable,  obstacle 
to  reduction. 

Congenital  dislocation  of  the  hip 
may  be  unilateral  or  bilateral,  and 
while  occasionally  the  result  of  intra- 
uterine traumatism,  is  usually  due  to 
an  arrest  of  development  of  the  ace- 
tabulum. The  head  rests  on  the  dor- 
sum ilii,  either  directly  upon  the  bone 
or  on  the  gluteus  minimus.  The  cap- 
sule is  stretched  and  thickened  to  bear 
the  weight  of  the  trunk.  The  tro- 
'chanters  can  be  seen  through  the 
glutei  ;  they  are  above  Nelaton's  line  ; 
there  is  usually  lumbar  lordosis  to 
compensate  for  the  displacement  pos- 
teriorly of  the  centre  of  gravity.  The 
perineum  is  widened. 

Disease  of  the  hip-joint  is  fre- 
quent and  grave.  It  may  begin  in 
the  epiphysis  for  the  head,  in  the 
synovial  membrane,  or,  much  more 
rarely,  in  the  articular  cartilage.  It 
may  be  of  any  variety,  but  tuberculous  disease  outnumbers  all  others. 

Both  the  frequency  and  the  gravity  of  disease  of  the  hip-joint  are  due  to  :  1, 
the  exceptional  exposure  of  the  joint  to  strains  or  traumatism  on  account  of  its  im- 
portance in  carrying  the  weight  of  the  trunk  and  in  progression  ;  2,  the  intra- 
capsular situation  of  the  upper  femoral  epiphysis  ;  3,  the  relation  of  the  joint  to 
some  of  the  most  powerful  muscles  of  the  body,  so  that  great  intra-articular  pressure 
is  easily  set  up  and  with  difficulty  overcome  ;  4,  its  enclosure  by  dense,  unyielding 
fibrous  structures  that  increase  tension  after  disease  has  begun  ;  5,  the  thinness  of 
the  non-articular  plate  of  bone  that  separates  it  from  the  pelvis,  and  the  presence 
up  to  puberty  of  the  Y-shaped  cartilage  which  divides  the  acetabulum  into  three 
bony  segments  (Fig.  353)  ;  6,  its  deep  situation,  rendering  the  early  symptoms  in 
many  cases  inconspicuous  ;  7,  the  deprivation  of  fresh  air  and  exercise,  and  often 
of  sunlight,  involved  in  the  immobilization  of  the  joint. 

The  disease  is  attended  by  certain  symptoms  having  a  definite  anatomical  basis  : 
1.  Swelling,  which  is  most  easily  demonstrated  (a)  at  the  lower  anterior  portion  of 
the  joint  just  internal  to  the  ilio-femoral  ligament,  where  the  capsule  is  thin  and  the 


PRACTICAL   CONSIDERATIONS  :    THE   HIP-JOINT.  381 

joint  is  nearest  the  surface  ;  and  (£>)  at  the  lower  posterior  part  of  the  capsule,  which 
is  also  thin.  2.  Tenderness  over  these  points, — i.e. ,  beneath  the  middle  of  Pou- 
part's  ligament  and  behind  the  trochanter.  3.  Alteration  in  position,  the  femur  being 
flexed,  abducted,  and  everted.  This  puts  the  joint  in  the  position  of  greatest 
comfort,  which  is  that  of  its  greatest  capacity.  In  extension  the  head  of  the  bone 
presses  against  the  upper  anterior  portion  of  the  capsule,  and  the  Y-ligament  is 
drawn  as  a  dense  band  across  the  front  of  the  joint.  Flexion  relaxes  the  superior 
or  main  portion  of  the  Y-ligament  and  the  ilio-psoas  muscle  ;  abduction,  the  outer 
limb  of  the  ligament  and  the  ilio-tibial  band  of  fascia  lata  ;  eversion,  the  inner 
limb.  Flexion  is,  in  its  effect  on  tension,  the  most  effective  of  these  motions  ; 
eversion  the  least.  The  joint  will  now  hold  a  larger  quantity  of  fluid  than  when  the 
limb  is  in  extension.  4.  At  this  stage,  to  bring  the  limb  parallel  with  its  fellow,  to 
overcome  the  shortening  caused  by  abduction,  and  to  relieve  strain,  as  the  thigh 
cannot  be  moved  on  the  pelvis,  the  lumbar  spine  is  curved  with  the  convexity 
towards  the  diseased  side  and  the  pelvis  is  tilted  downward  on  that  side.  This  is 
the  stage  of  apparent  lengthening.  The  real  position  of  the  limb  in  abduction  is 
shown  by  straightening  the  pelvis  so  that  a  line  drawn  between  the  two  anterior 
superior  spines  is  at  right  angles  to  the  longitudinal  mid-line  of  the  body.  5.  With 
the  same  object  of  securing  parallelism, — i.e. ,  of  reducing  strain  upon  the  mus- 
cular and  fibrous  structures  which  are  holding  the  limb  in  its  abnormal  position, 
— the  deformity  caused  by  flexion  (maintained  by  the  ilio-psoas,  which  is  in 
such  close  relation  to  the  front  of  the  capsule)  is  met  by  an  arching  forward — 
lordosis — of  the  lumbar  spine.  The  real  position  of  the  limb  in  flexion  is  shown 
by  raising  the  thigh  of  the  affected  side  until  the  lumbar  curve  is  effaced  and  the 
lumbar  spines  touch  the  surface  on  which  the  patient  lies.  6.  Pain  in  the  knee  is 
often  marked.  It  is  due  to  the  association  of  the  nerve-supply  to  the  two  joints, 
both  being  innervated  from  the  same  spinal  segments,  as  they  both  receive  twigs 
from  the  anterior  crural,  obturator,  sciatic,  and  sacral  plexus.  7.  Rigidity  of  the 
joint  is  due  to  fixation  by  («)  the  muscles  inserted  into  and  passing  over  the  cap- 
sule ;  (b)  all  the  muscles  moving  the  lower  limb  on  the  pelvis.  Rotation  is  the 
most  valuable  movement  for  diagnostic  purposes  because  it  is  least  likely  to  be 
interfered  with  by  extra-articular  disease.  For  example,  in  abscess  beneath  the 
gluteus,  or  in  enlargement  of  the  subgluteal  bursa,  flexion  of  the  thigh  is  interfered 
with  ;  in  psoas  or  iliac  abscess  extension  is  limited  ;  in  superficial  disease  of  the 
upper  end  of  the  shaft,  or  in  suppuration  of  the  bursa  over  the  trochanter,  adhe- 
sions of  the  soft  parts  may  limit  both  flexion  and  extension.  8.  Muscular  wasting 
is  often  a  very  early  symptom,  and  is  then  due  to  reflex  atrophy  from  the  associa- 
tion— emphasized  long  ago  by  Hilton — of  the  nerves  supplying  a  joint  with  those  of 
the  muscles  moving  that  joint  ;  in  this  instance  both  joint  and  muscles  are  supplied 
by  the  anterior  crural,  the  sciatic,  the  sacral  plexus,  the  obturator,  etc.  Later, 
atrophy  of  muscles  may  be  due  to  disuse.  The  glutei  and  the  thigh  muscles  are 
those  most  obviously  affected.  The  atrophy  of  the  former  aids  in  producing  the 
characteristic  obliteration  of  the  gluteo-femoral  crease.  9.  After  softening  of  the 
capsule  and  diminution  of  tension  have  occurred,  the  adductors  draw  the  limb 
inward.  The  lumbar  spine  is  now  curved  so  that  the  concavity  is  towards  the 
diseased  side,  thereby  drawing  up  the  pelvis  on  that  side  so  as  to  relieve  strain  and 
secure  parallelism  of  the  limb.  This  is  the  stage  of  apparent  shortening.  The 
real  position  of  the  limb  in  adduction  is  shown  by  bringing  the  interspinous  line  to 
a  right  angle  with  the  longitudinal  axis  of  the  body.  The  adductors  are  supplied 
almost  exclusively  by  the  obturator  nerve,  which  enters  largely  into  the  supply  of 
the  articulation,  and  act  to  great  advantage  when  the  capsular  and  ligamentous 
resistance  has  partly  disappeared.  As  the  shaft  and  lower  end  of  the  femur  move 
inward,  the  head  is  necessarily  brought  more  forcibly  against  the  outer  fibres  of  the 
capsule  near  its  pelvic  attachment,  and  when  they  soften  is  partially  projected  from 
the  acetabulum,  against  the  upper  and  outer  rim  of  which  it  rests.  10.  During 
this  stage  the  trochanter  on  the  diseased  side  is  often  found  to  be  nearer  the  middle 
line  of  the  body  than  the  other  trochanter.  The  cause  of  this  is  either  absorption 
of  the  head  and  neck  of  the  femur  or  deepening  of  the  acetabulum  with  sinking 
in  of  the  head,  and  the  diagnosis  between  these  may  be  made  by  rectal  examina- 


382  HUMAN    ANATOMY. 

tion,  which  sometimes  shows  thickening  over  the  inner  surface  of  the  acetabulum  in 
the  latter  case  and  not  in  the  former  (Cheyne).  In  dislocation  from  disease,  unless 
there  has  been  separation  of  the  head  or  great  absorption  of  the  neck,  the  tro- 
chanter will  be  farther  away  from  the  middle  line  on  the  affected  side  than  on  the 
sound  one.  This  will  serve  to  distinguish  shortening  of  the  limb  due  to  this  cause 
from  shortening  due  to  acetabular  deepening.  Abscesses  developing  within  the 
joint  may  pass  outward  through  the  thin  posterior  part  of  the  capsule,  and  under 
the  gluteal  muscles,  to  a  point  beneath  the  greater  trochanter ;  they  may  make  their 
exit  through  the  cotyloid  notch  and  point  in  Scarpa's  triangle  ;  they  frequently 
pass  out  anteriorly,  and  are  found  beneath  the  tensor  vaginas  femoris  at  the  outer 
aspect  of  the  thigh  ;  they  may  perforate  the  acetabulum  and  point  within  the 
pelvis.  A  finger  in  the  rectum  may  then  detect  fluctuation  through  the  structures 
that  separate  the  abscess  from  the  rectal  wall, — viz. ,  the  anal  fascia,  the  levator  ani,  the 
obturator  fascia  and  obturator  internus,  and  the  periosteum  of  the  inner  surface  of 
the  innominate  bone.  After  perforation  of  the  acetabulum,  an  abscess  may  extend 
upward  and  point  above  Poupart's  ligament  on  the  inner  side  of  the  vessels. 

Excision  of  the  hip  may  be  done  either  by  means  of  an  anterior  incision 
passing  between  the  tensor  vagina?  and  sartorius  muscles  superficially  and  the 
glutei  and  rectus  more  deeply,  or  by  a  posterior  incision  in  the  line  of  the  limb 
and  just  back  of  the  greater  trochanter,  the  muscles  attached  to  which  being  divided 
as  close  to  the  bone  as  possible. 

THE  FRAMEWORK  OF  THE  LEG. 
This  is  formed  -by  the  tibia  and  the  fibula  and  the  interosseous  membrane  (Fig. 
411).  The  bones  are  so  closely  united  as  to  constitute  one  apparatus,  but  as  they 
are  separable  it  is  necessary  to  describe  them  apart.  The  tibia,  very  much  the  larger, 
is  the  only  one  concerned  in  forming  the  knee-joint,  and  bears  almost  the  whole 
weight.  It  forms  the  upper  and  inner  side  of  the  mortise  known  as  the  ankle-joint. 
The  fibula,  placed  externally  and  posteriorly,  is  a  slender  bone.  The  upper  end  has 
a  true  joint  with  the  tibia,  the  lower  is  more  closely  fastened  to  it.  The  interosseous 
membrane  is  at  the  bottom  of  a  hollow  between  the  bones.  The  arrangement  favors 
lightness,  as  it  gives  increased  size  for  the  origin  of  muscles.  The  joints  of  the 
fibula,  as  well  as  its  elasticity,  serve  to  break  shocks. 

THE   TIBIA. 

The  tibia  consists  of  a  shaft,  an  upper  and  a  lower  extremity. 

The  upper  extremity,  or  head,  composed  of  an  outer  and  an  inner  tuberosity, 
is  very  large,  expanding  laterally  from  the  shaft.  The  outline  of  the  upper  surface 
is  transversely  oval,  the  inner  end  being  the  broader.  It  is  chiefly  occupied  by  two 
articular  surfaces  for  the  condyles  of  the  femur,  separated  at  the  middle  by  a  promi- 
nence, the  spinel  with  a  triangular  non-articular  surface  before  and  behind  it.  The 
former  of  these  is  rough,  the  latter  smooth  and  grooved.  The  spine  itself  is  com- 
posed of  two  lateral  parts  connected  behind,  of  which  the  inner  is  the  longer  from 
before  backward,  rising  from  the  condylar  surfaces.  The  crucial  ligaments  of  the 
knee-joint  are  attached  to  the  non-articular  surfaces  before  and  behind  it.  The 
inner  condylar  facet  is  concave  ;  it  has  an  oval  outline  and  is  longer  from  before 
backward  than  transversely.  It  rises  as  a  ridge  on  the  side  of  the  spine.  The  otder 
facet  is  more  nearly  circular,  being  shorter  than  the  inner.  It  is  slightly  depressed 
in  the  middle.  The  posterior  half  is  usually  a  little  convex  from  before  backward, 
and  is  often  prolonged  onto  the  posterior  surface  of  the  bone.  The  convexity  is 
much  greater  when  the  semilunar  cartilage  is  intact.  The  front  half  may  be  plane, 
convex,  or  concave  in  the  same  direction.  This  facet  rises  to  a  point  on  the  outer 
side  of  the  spine.  The  tuberosities2  overhang  the  back  of  the  tibia.  They  are 
separated  behind  by  the  popliteal  notch7'  continuous  with  the  groove  from  the  top. 
Under  the  back  of  the  outer  tuberosity  is  a  small  articular  facet  for  the  head  of  the 
fibula,  looking  downward  and  a  little  backward  and  outward.  Its  outline  is  uncer- 
tain, being  either  round  or  quadrilateral.      It  may  be  curved  in  any  direction,   and 

1  Emincntia  iutercondyloidea.     -  Condylus  lateralis  et  medialis.     3  Fossa  intercondyloidea  posterior. 


THE  TIBIA.  383 

its  inclination  varies  much.  In  some  cases  it  nearly  or  quite  reaches  the  superior 
articular  surface.  Laterally,  this  tuberosity  is  rough  for  the  ligaments  of  the  knee- 
joint.  The  same  may  be  said  of  the  side  of  the  inner  tuberosity,  which  towards  the 
back  has  a  broad  horizontal  groove  running  along  it  for  the  tendon  of  the  semi- 
membranosus. The  tubercle1  of  the  tibia  is  a  triangular  prominence  on  the  front  of 
the  upper  end.  Its  lower  part  is  rough  for  the  tendon  of  the  extensor  quadriceps, 
and  its  upper  smooth  for  a  bursa  between  this  tendon  and  the  bone.  The  top  of 
the  tubercle  is  about  an  inch  below  the  top  of  the  bone  ;  it  is  lost  below  in  the  ridge 
of  the  front  of  the  shaft. 

The  shaft 2  has  three  borders  and  three  surfaces.  The  anterior  border,  the  crest3 
begins  at  the  outer  side  of  the  tubercle,  curves  as  it  descends,  at  first  a  little  inward, 
then  a  little  the  other  way  through  the  middle  of  the  shaft,  where  it  is  very  sharp, 
and,  finally,  at  the  lower  third,  becoming  much  less  prominent,  it  sweeps  to  the 
front  of  the  inner  malleolus.  The  inner  border,  the  least  marked  of  the  three,  begins 
under  the  inner  tuberosity  near  the  back  and  goes  to  the  back  of  the  inner  malleolus. 
It  is  most  distinct  in  the  middle.  The  outer  border,  or  interosseous  ridge, *  begins  below 
the  facet  for  the  head  of  the  fibula,  runs  downward  and  somewhat  backward  past  the 
middle  of  the  shaft,  and  then,  inclining  forward,  divides  some  two  or  three  inches 
above  the  lower  end  into  two  lines  enclosing  a  space  on  the  outer  side  of  the  lower 
end,  to  which  the  fibula  is  bound  by  ligaments.  The  anterior  of  these  divisions  is 
the  more  evident  continuation  of  the  ridge.  The  internal  surface  is  subcutaneous  : 
generally  convex  above  and  concave  below  ;  the  outer,  bounded  behind  by  the  in- 
terosseous ridge,  is  at  first  external,  but  in  the  lower  third  twists  to  the  front.  The 
posterior,  in  its  upper  and  lower  parts,  faces  also  somewhat  outward.  It  is  crossed 
in  the  upper  third  by  the  oblique  line,5  which,  running  downward  and  inward  from 
the  back  of  the  fibular  facet  to  the  inner  border,  marks  off  a  triangular  space  above 
it  which  is  occupied  by  the  popliteus  muscle.  A  vertical  line,  generally  very  faint, 
running  down  for  some  distance  from  the  oblique  line  partially  divides  this  sur- 
face into  an  inner  broader  and  an  outer  narrower  part  :  the  former  for  the  flexor  of 
the  toes,  the  latter  for  the  tibialis  posticus.  The  nutrient  foramen,  the  largest 
in  the  body,  is  on  this  surface  at  the  junction  of  the  first  and  second  thirds  external 
to  the  oblique  line ;  it  runs  down  into  the  bone.  The  shaft  is  triangular  on  section  in 
the  upper  and  middle  thirds,  being  narrower  and  sharper  in  front  in  the  middle  one. 
In  the  lower  third  the  section  becomes  quadrilateral  as  the  shaft  broadens  and  the 
anterior  border  sinks  and  turns  inward. 

The  lower  extremity  is  thickest  transversely.  The  internal  malleolus*  is  a 
thick  projection  downward  and  inward  from  the  whole  of  the  inner  side,  to  form 
one  boundary  of  the  ankle.  Its  lower  end  is  thick,  reaching  farthest  down  in  front, 
with  a  depression  at  the  back  for  the  lateral  ligament  of  the  ankle.  The  surface 
looking  towards  the  joint  is  articular  ;  it  slants  a  little  away  from  the  median  line  of 
the  bone.  The  outer  side  of  the  lower  end  of  the  shaft  is  slightly  concave,  with  a 
tubercle  both  before  and  behind.  The  articular  cartilage  of  the  lower  end  is  pro- 
longed some  two  or  three  millimetres  onto  this  outer  side.  Both  in  front  and  behind, 
but  especially  in  front,  the  bone  presents  a  swelling,  separated  by  a  depression  from 
the  lower  border,  above  which  the  capsule  is  inserted.  On  the  posterior  surface  a 
broad  groove  for  the  tendons  of  the  tibialis  posticus  and  the  flexor  longus  digitorum 
runs  obliquely  downward  and  inward  onto  and  along  the  hind  border  of  the  mal- 
leolus. A  faint  groove  for  the  flexor  longus  hallucis  is  sometimes  seen  near  the 
outer  end  of  the  posterior  surface.  The  lower  side  forms  the  top  of  the  ankle- 
joint  and  is  wholly  articular.  It  is  broader  before  than  behind,  as  the  sides  converge 
towards  the  back.  It  is  concave  from  before  backward.  There  is  a  slight  antero- 
posterior elevation  in  the  middle,  fitting  into  a  depression  on  the  top  of  the  as- 
tragalus. 

Variations. — The  transverse  axes  of  the  knee-  and  ankle-joints  are  rarely 
parallel.  The  shaft  of  the  tibia  is  so  twisted  as  to  make  the  foot  point  outward. 
The  angle  between  the  two  axes  varies  from  o  to  480,  but  is  usually  between  50  and 
200.  The  backward  inclination  of  the  top  of  the  tibia  varies  considerably.  When 
excessive,  it  seems  to  imply  an  aptitude  for  the  squatting  position,  as  among  the 
natives  of  India,  but  no  inability  to  assume  the  upright  position.      A  continuation 

1  Tuberositas  tibiae.     -'Corpus  tibiae.     :t  Crista  anterior.     i  Crista  intcrossea.     ;'  Linea  poplitea.     c  Malleolus  mediaiis. 


382  HUMAN    ANATOMY. 

tion,  which  sometimes  shows  thickening  over  the  inner  surface  of  the  acetabulum  in 
the  latter  case  and  not  in  the  former  (Cheyne).  In  dislocation  from  disease,  unless 
there  has  been  separation  of  the  head  or  great  absorption  of  the  neck,  the  tro- 
chanter will  be  farther  away  from  the  middle  line  on  the  affected  side  than  on  the 
sound  one.  This  will  serve  to  distinguish  shortening  of  the  limb  due  to  this  cause 
from  shortening  due  to  acetabular  deepening.  Abscesses  developing  within  the 
joint  may  pass  outward  through  the  thin  posterior  part  of  the  capsule,  and  under 
the  gluteal  muscles,  to  a  point  beneath  the  greater  trochanter ;  they  may  make  their 
exit  through  the  cotyloid  notch  and  point  in  Scarpa's  triangle  ;  they  frequently 
pass  out  anteriorly,  and  are  found  beneath  the  tensor  vaginae  femoris  at  the  outer 
aspect  of  the  thigh  ;  they  may  perforate  the  acetabulum  and  point  within  the 
pelvis.  A  finger  in  the  rectum  may  then  detect  fluctuation  through  the  structures 
that  separate  the  abscess  from  the  rectal  wall, — viz. ,  the  anal  fascia,  the  levator  ani,  the 
obturator  fascia  and  obturator  internus,  and  the  periosteum  of  the  inner  surface  of 
the  innominate  bone.  After  perforation  of  the  acetabulum,  an  abscess  may  extend 
upward  and  point  above  Poupart's  ligament  on  the  inner  side  of  the  vessels. 

Excision  of  the  hip  may  be  done  either  by  means  of  an  anterior  incision 
passing  between  the  tensor  vaginae  and  sartorius  muscles  superficially  and  the 
glutei  and  rectus  more  deeply,  or  by  a  posterior  incision  in  the  line  of  the  limb 
and  just  back  of  the  greater  trochanter,  the  muscles  attached  to  which  being  divided 
as  close  to  the  bone  as  possible. 

THE  FRAMEWORK  OF  THE  LEG. 
This  is  formed  -by  the  tibia  and  the  fibula  and  the  interosseous  membrane  (Fig. 
411).  The  bones  are  so  closely  united  as  to  constitute  one  apparatus,  but  as  they 
are  separable  it  is  necessary  to  describe  them  apart.  The  tibia,  very  much  the  larger, 
is  the  only  one  concerned  in  forming  the  knee-joint,  and  bears  almost  the  whole 
weight.  It  forms  the  upper  and  inner  side  of  the  mortise  known  as  the  ankle-joint. 
The  fibula,  placed  externally  and  posteriorly,  is  a  slender  bone.  The  upper  end  has 
a  true  joint  with  the  tibia,  the  lower  is  more  closely  fastened  to  it.  The  interosseous 
membrane  is  at  the  bottom  of  a  hollow  between  the  bones.  The  arrangement  favors 
lightness,  as  it  gives  increased  size  for  the  origin  of  muscles.  The  joints  of  the 
fibula,  as  well  as  its  elasticity,  serve  to  break  shocks. 

THE   TIBIA. 

The  tibia  consists  of  a  shaft,  an  upper  and  a  lower  extremity. 

The  upper  extremity,  or  head,  composed  of  an  outer  and  an  inner  tuberosity, 
is  very  large,  expanding  laterally  from  the  shaft.  The  outline  of  the  upper  surface 
is  transversely  oval,  the  inner  end  being  the  broader.  It  is  chiefly  occupied  by  two 
articular  surfaces  for  the  condyles  of  the  femur,  separated  at  the  middle  by  a  promi- 
nence, the  spine,1  with  a  triangular  non-articular  surface  before  and  behind  it.  The 
former  of  these  is  rough,  the  latter  smooth  and  grooved.  The  spine  itself  is  com- 
posed of  two  lateral  parts  connected  behind,  of  which  the  inner  is  the  longer  from 
before  backward,  rising  from  the  condylar  surfaces.  The  crucial  ligaments  of  the 
knee-joint  are  attached  to  the  non-articular  surfaces  before  and  behind  it.  The 
inner  condylar  facet  is  concave  ;  it  has  an  oval  outline  and  is  longer  from  before 
backward  than  transversely.  It  rises  as  a  ridge  on  the  side  of  the  spine.  The  outer 
facet  is  more  nearly  circular,  being  shorter  than  the  inner.  It  is  slightly  depressed 
in  the  middle.  The  posterior  half  is  usually  a  little  convex  from  before  backward, 
and  is  often  prolonged  onto  the  posterior  surface  of  the  bone.  The  convexity  is 
much  greater  when  the  semilunar  cartilage  is  intact.  The  front  half  may  be  plane, 
convex,  or  concave  in  the  same  direction.  This  facet  rises  to  a  point  on  the  outer 
side  of  the  spine.  The  tuberosities  2  overhang  the  back  of  the  tibia.  They  are 
separated  behind  by  the  popliteal  notch*  continuous  with  the  groove  from  the  top. 
Under  the  back  of  the  outer  tuberosity  is  a  small  articular  facet  for  the  head  of  the 
fibula,  looking  downward  and  a  little  backward  and  outward.  Its  outline  is  uncer- 
tain, being  either  round  or  quadrilateral.      It  may  be  curved  in  any  direction,   and 

1  Etninentia  iutercondylnidea.     ~  Condylus  lateralis  et  medialis.     8  Fossa  intercondyloidea  posterior. 


THE  TIBIA.  383 

its  inclination  varies  much..  In  some  cases  it  nearly  or  quite  reaches  the  superior 
articular  surface.  Laterally,  this  tuberosity  is  rough  for  the  ligaments  of  the  knee- 
joint.  The  same  may  be  said  of  the  side  of  the  inner  tuberosity,  which  towards  the 
back  has  a  broad  horizontal  groove  running  along  it  for  the  tendon  of  the  semi- 
membranosus. The  tubercle1  of  the  tibia  is  a  triangular  prominence  on  the  front  of 
the  upper  end.  Its  lower  part  is  rough  for  the  tendon  of  the  extensor  quadriceps, 
and  its  upper  smooth  for  a  bursa  between  this  tendon  and  the  bone.  The  top  of 
the  tubercle  is  about  an  inch  below  the  top  of  the  bone  ;  it  is  lost  below  in  the  ridge 
of  the  front  of  the  shaft. 

The  shaft 2  has  three  borders  and  three  surfaces.  The  anterior  border,  the  crest3 
begins  at  the  outer  side  of  the  tubercle,  curves  as  it  descends,  at  first  a  little  inward, 
then  a  little  the  other  way  through  the  middle  of  the  shaft,  where  it  is  very  sharp, 
and,  finally,  at  the  lower  third,  becoming  much  less  prominent,  it  sweeps  to  the 
front  of  the  inner  malleolus.  The  inner  border,  the  least  marked  of  the  three,  begins 
under  the  inner  tuberosity  near  the  back  and  goes  to  the  back  of  the  inner  malleolus. 
It  is  most  distinct  in  the  middle.  The  outer  border,  or  interosseous  ridge,''  begins  below 
the  facet  for  the  head  of  the  fibula,  runs  downward  and  somewhat  backward  past  the 
middle  of  the  shaft,  and  then,  inclining  forward,  divides  some  two  or  three  inches 
above  the  lower  end  into  two  lines  enclosing  a  space  on  the  outer  side  of  the  lower 
end,  to  which  the  fibula  is  bound  by  ligaments.  The  anterior  of  these  divisions  is 
the  more  evident  continuation  of  the  ridge.  The  internal  surface  is  subcutaneous  : 
generally  convex  above  and  concave  below  ;  the  outer,  bounded  behind  by  the  in- 
terosseous ridge,  is  at  first  external,  but  in  the  lower  third  twists  to  the  front.  The 
posterior,  in  its  upper  and  lower  parts,  faces  also  somewhat  outward.  It  is  crossed 
in  the  upper  third  by  the  oblique  line,h  which,  running  downward  and  inward  from 
the  back  of  the  fibular  facet  to  the  inner  border,  marks  off  a  triangular  space  above 
it  which  is  occupied  by  the  popliteus  muscle.  A  vertical  line,  generally  very  faint, 
running  down  for  some  distance  from  the  oblique  line  partially  divides  this  sur- 
face into  an  inner  broader  and  an  outer  narrower  part  :  the  former  for  the  flexor  of 
the  toes,  the  latter  for  the  tibialis  posticus.  The  ?i2ttrie?it  foramen,  the  largest 
in  the  body,  is  on  this  surface  at  the  junction  of  the  first  and  second  thirds  external 
to  the  oblique  line ;  it  runs  down  into  the  bone.  The  shaft  is  triangular  on  section  in 
the  upper  and  middle  thirds,  being  narrower  and  sharper  in  front  in  the  middle  one. 
In  the  lower  third  the  section  becomes  quadrilateral  as  the  shaft  broadens  and  the 
anterior  border  sinks  and  turns  inward. 

The  lower  extremity  is  thickest  transversely.  The  internal  malleolus*  is  a 
thick  projection  downward  and  inward  from  the  whole  of  the  inner  side,  to  form 
one  boundary  of  the  ankle.  Its  lower  end  is  thick,  reaching  farthest  down  in  front, 
with  a  depression  at  the  back  for  the  lateral  ligament  of  the  ankle.  The  surface 
looking  towards  the  joint  is  articular  ;  it  slants  a  little  away  from  the  median  line  of 
the  bone.  The  outer  side  of  the  lower  end  of  the  shaft  is  slightly  concave,  with  a 
tubercle  both  before  and  behind.  The  articular  cartilage  of  the  lower  end  is  pro- 
longed some  two  or  three  millimetres  onto  this  outer  side.  Both  in  front  and  behind, 
but  especially  in  front,  the  bone  presents  a  swelling,  separated  by  a  depression  from 
the  lower  border,  above  which  the  capsule  is  inserted.  On  the  posterior  surface  a 
broad  groove  for  the  tendons  of  the  tibialis  posticus  and  the  flexor  longus  digitorum 
runs  obliquely  downward  and  inward  onto  and  along  the  hind  border  of  the  mal- 
leolus. A  faint  groove  for  the  flexor  longus  hallucis  is  sometimes  seen  near  the 
outer  end  of  the  posterior  surface.  The  lower  side  forms  the  top  of  the  ankle- 
joint  and  is  wholly  articular.  It  is  broader  before  than  behind,  as  the  sides  converge 
towards  the  back.  It  is  concave  from  before  backward.  There  is  a  slight  antero- 
posterior elevation  in  the  middle,  fitting  into  a  depression  on  the  top  of  the  as- 
tragalus. 

Variations. — The  transverse  axes  of  the  knee-  and  ankle-joints  are  rarely 
parallel.  The  shaft  of  the  tibia  is  so  twisted  as  to  make  the  foot  point  outward. 
The  angle  between  the  two  axes  varies  from  o  to  48°,  but  is  usually  between  50  and 
200.  The  backward  inclination  of  the  top  of  the  tibia  varies  considerably.  When 
excessive,  it  seems  to  imply  an  aptitude  for  the  squatting  position,  as  among  the 
natives  of  India,  but  no  inability  to  assume  the  upright  position.      A  continuation 

1  Tuberositas  tibiae.     "  Corpus  tibiae.     3  Crista  anterior.     4  Crista  interossea.     :>  Linea  poplitea.     °  Malleolus  medialis. 


3»4 


HUMAN   ANATOMY. 


Spine 


Fig.  399. 


Ext.  condylar  surface  y-\~.   Int-  condylar  surface 


For  ligamentum 


Biceps- 


Ext.  long r     '■'f\(ff 

digitorum       \     i      f\wf         Tendon  patella 
u  i*ji"!fil         (extensor 

-  quadriceps) 

-  Gracilis 
"?Sartorius 


Tibialis  antic 21  si 


-Semitendinosus 


For  astragalub^r  Internal  malleolus 
Right  tibia  from  before.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


THE  TIBIA. 


385 


Fig.  400. 

Int.  condylar  surface 


Internal  tuberosity 
Groove  tor  semimembr 


Semimembranosus- 


Soleus  (tibial  head)  — 
Flex.  long,  digit  or  urn — 


-  Tibialis  postii 


Groove  for  tibial,  post,  2.r\dflex.  long.  digit._j^ 
Internal  malleol 


External  tuberosity 


Posterior  dn 

interosseous  border 
Tibio-fibular  ligament 

Groove  tax  flex.  long.  hall. 


:  astragalus 
Right  tibia  from  behind.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


386 


HUMAN   ANATOMY. 


of  the  lower  articular  cartilage  onto  the  front  of  the  tibia,  allowing  extreme  dorsal 
flexion  of  the  ankle,   is  often  associated  with  this.     The  thickness  of  the  tibia  is 


Fig.  401. 

Spine 
Ext.  fibro-cartilage      /\     Post,  crucial  ligament 


Int.  fibro-cartilage 


Ext.  condylar  surface' 


Ext.  fibro-cartilage^ 
Anterior  crucial  ligame: 


Int.  condylar  surface 


Int.  fibro-cartilage 


Bursal  surface 


Attachment  of  tendon 
patellae 


Upper  end  of  right  tibia  from  above  and  before. 


very  variable.     The  very  thin,  platycnemic,  form  is  most  common  in  savage  races, 
and  is  therefore  associated  with  the  pilastered  femur.      It  is  found  not  rarely  among 

Fig.  402. 


Fig.  403. 


Frontal  section  of  upper  end  of  tibia. 


whites,  but  the  shape  of  the  accompanying  femur  is  uncertain.      The  tibial  index 
/transverse  diameter  x  100 \  jg    h    raj.jo    j    ^    transverse  to  the  antero-posterior  diameter. 

\ antero-postenor  diameter/  " 


PRACTICAL    CONSIDERATIONS  :    THE   TIBIA. 


387 


According  to  French  statistics,  this  in  whites  is  from  70  to  80  ;  in  savage  races  it  is 
much  lower.  The  method  of  reckoning  it  at  the  level  of  the  nutrient  foramen  is 
likely  to  be  superseded  by  one  choosing  the  middle  of  the  bone. 

Structure. — The  shaft  has  strong  walls  in  the  middle,  being  especially  thick 
under  the  crest.  At  both  ends  the  walls  become  thin.  The  head  contains  a  large 
amount  of  cancellated  tissue  with  comparatively  thin  walls.  The  architectural  arrange- 
ment of  the  trabecular  at  the  ends  is  very  clear.  A  frontal  section  of  the  upper  end 
shows  successive  vertical  plates  springing  from  the  sides  to  support  the  expanding 
tuberosities,  with  an  irregular  system  in  the  middle.  •  Sagittal  sections  show  plates 
from  the  walls  meeting  each  other  in  arches.  A  somewhat  similar  pattern  is  seen 
at  the  lower  end.  In  a  frontal  section  there  are  several  transverse  plates,  of  which 
the  strongest  marks  the  border  of  the  epiphysis.  Several  of  these  from  the  outer 
side  turn  down  to  join  the  lower  surface  at  the  origin  of  the  malleolus,  where  there 
is  a  distinct  thickening  of  the  crust.  There  is  sometimes  an  imperfect  bony  canal 
for  the  nutrient  artery  for  a  short  distance  after  its  entrance  into  the  cancellated 
tissue. 

Development. — There  are  only  three  centres  of  ossification  :  one  for  the 
shaft,  appearing  in  the  seventh  or  eighth  fcetal  week  ;  one  for  the  upper  end,  appear- 
ing usually  in  the  last  month  of  fcetal  life  ;  and  one  in  the  lower,  appearing  in  the 
second  half-year.1     These  epiphyses  correspond  to  what  has  been  described  as  the 

Fig.  404. 


Ossification  of  tibia  and  fibula.  A,  at  eighth  fcetal  month  ;  £,  at  birth  ;  C,  at  two  and  one-half  years  ■  D,  at  four 
"years;  E,  at  about  fifteen  years,  o,  centre  for  shafts  ;  A,  for  upper  epiphysis  of  tibia;  c,  for  lower  epiphysis  of  fibula; 
d,  for  lower  epiphysis  of  tibia  ;  e,  for  upper  epiphysis  of  fibula  ;  f,  for  tubercle  of  tibia. 

ends  of  the  bone.  The  upper  extends  farthest  down  on  the  front,  including  the 
tubercle,  which  may  have  a  separate  nucleus.  According  to  Rambaud  and  Renault, 
this  is  of  usual  occurrence,  appearing  at  from  eight  to  fourteen  years  and  quickly 
joining  the  epiphysis.  The  lower  end  joins  the  shaft  at  about  eighteen  and  the 
upper  at  nineteen  or  twenty. 


PRACTICAL   CONSIDERATIONS. 

The  upper  epiphysis  of  the  tibia  is  separated  only  by  traumatism  of  marked 
severity  because  of  :  (1)  its  great  width;  (2)  its  irregularly  cupped  surface;  (3) 
the  downward  projection  in  which  the  tibial  tubercle  is  developed,  or  to  which  the 
latter  becomes  united  when  it  arises  from  a  separate  centre  ;  (4)  the  protection 
afforded  it  (a)  on  the  outer  side  by  the  head  of  the  fibula  (which  is  connected 
exclusively  with  this  epiphysis),  the  anterior  and  posterior  upper  tibio-fibular  liga- 
ments, and  indirectly  by  the  external  lateral  ligament  ;  (d)  on  the  inner  side  by 
the  internal  lateral  ligament,  and  (c)  on  both  sides  by  the  fibres  of  insertion  of  the 

1  Fagerlund  :  loc.  cit. 


HUMAN    ANATOMY. 


vasti  and  semimembranosus  and  of  their  fascial  expansions  ;  (5)  the  toughness  of 
the  periosteum  uniting  it  with  the  diaphysis  ;  and  (6)  the  fact  that  while  there  is 
no  possibility  of  its  displacement  by  muscular  action,  it  does  not  project  enough 
to  be  exposed  to  the  effects  of  direct  violence.  The  possibility  of  disjunction  of 
this  epiphysis  complicating  an  injury  to  the  knee  continues  up  to  the  twentieth 
year  at  least  ;  in  injuries  to  the  elbow  epiphyseal  separation  may  be  excluded 
after  the  eighteenth  year. 

Three-fourths  of  the  recorded  cases  have  occurred  in  males,  as  might  be 
expected  on  account  of  their  more  frequent  exposure  to  serious  injury.  The 
epiphysis  has  been  displaced  forward,  and  outward  and  forward.  It  has  never  been 
displaced  backward,  partly,  at  least,  on  account  of  the  tongue-like  process  con- 
necting it  with  the  tibial  tubercle.  Its  inward  displacement  would  necessitate  the 
separation  of  the  head  of  the  fibula  or  the  laceration  of  the 
Fig.  405.  superior  tibio-fibular  ligaments.      The  attachment  of  the  syno- 

vial membrane  of  the  knee-joint  does  not  descend  to  the  level 
of  this  epiphysis  ;  hence  that  articulation  is  often  not  involved 
in  these  injuries.  They  should  not,  when  severe,  be  mistaken 
for  dislocation,  or,  when  slight,  for  sprains  of  the  knee.  They 
may  be  distinguished  from  the  former  by  the  age  of  the  patient 
and  the  unimpaired  mobility  of  the  knee,  and  from  the  latter 
by  the  situation  of  the  pain  or  tenderness.  Dislocation  of  the 
knee  is  very  rare  in  children. 

Good  union  has  taken  place  in  some  cases  ;  arrest  of  growth 
has  followed  in  others,  as  might  be  expected  from  the  fact  that 
the  chief  increase  in  length  of  the  tibia  takes  place  from  this 
epiphysis. 

The  tubercle  of  the  tibia  has  been  detached  in  ten  recorded 
instances,  all  males  :  nine  from  violent  action  of  the  quadriceps 
in  powerful  young  men,  eight  of  whom  were  between  sixteen 
and  eighteen  years  of  age,  the  age  of  the  remaining  two  not 
having  been  mentioned  (Poland). 

This  separation  should  be  carefully  distinguished  from  frac- 
ture of  the  patella.  In  disjunction  the  latter  bone  is  drawn 
upward,  the  patient  is  unable  to  extend  the  leg,  and  the  swell- 
ing following  laceration  of  the  subligamentous  bursa  may  simu- 
late swelling  of  the  knee-joint.  The  latter  may  be  involved 
directly — as  the  synovial  membrane  is  in  close  proximity  to  the 
tubercle — or  indirectly,  through  the  occasional,  though  rare, 
communication  with  the  subligamentous  bursa.  Fracture  of  the 
patella,  however,  does  not  occur  in  children  and  is  very  rare, 
in  adolescence.  In  patella  fracture  the  fragments  of  bone  are 
brought  together,  so  that  crepitus  may  be  felt  only  by  pushing 
the  two  fragments  towards  each  other;  the  groove  between 
them  can  almost  always  be  recognized.  In  disjunction  of  the 
Epiphyseal  lines  of  tibia,  tubercle  crepitus  can  be  elicited  only  by  pulling  the  fragment 
downward  ;  the  outline  of  the  patella  is  normal,  and  can  usually 
be  made  out.      The  X-rays  would  be  conclusive.      Bony  union  should  be  expected. 

The  shaft  of  the  tibia  gradually  decreases  in  size  to  about  the  junction  of  the 
middle  and  lower  thirds,  and  then  expands  again  to  the  ankle.  At  its  smallest 
point — on  an  average  about  ten  centimetres  (four  inches)  above  its  lower  end — it 
has  to  bear  a  greater  weight  on  a  smaller  area  than  any  other  bone  (Humphry).  At 
this  level  meet  the  two  independent  vertical  columns  into  which,  according  to 
Fayel  and  Duret,  the  spongy  tissue  of  the  tibia  is  divided  (one  occupying  the 
upper  two- thirds,  the  other  the  lower  third  of  the  bone),  and  hence  these  authorities 
assert  that  this  spot  represents  the  minimum  of  resistance  (Treves).  In  some 
tibiae  it  is  at  or  near  the  junction  of  an  ill-defined  long  upper  curve,  in  which  the 
crest  terminates,  and  a  short  lower  curve.  On  transverse  section  the  tibia  is  seen 
to  be  cylindrical  in  its  lower  third  and  three-sided  above.  As  it  has  been  demon- 
strated that   if  two   homogeneous   solids    present  on  section  equal  areas,   the  one 


PRACTICAL    CONSIDERATIONS:     THE   TIBIA. 


3§9 


triangular  and  the  other  circular,  the  former  has  the  greater  power  of  resistance 
(Tillaux),  the  shape  of  the  tibia  in  this  region  is  thought  to  be  an  additional  source 
of  weakness. 

For  all  these  reasons  it  is  the  most  frequent  seat  of  fracture  from  indirect  vio- 
lence. As  in  such  cases  the  breaking  strain  is  usually  continued  for  a  moment 
after  the  tibia  gives  way,  the  weak  fibula  is  apt  to  be  broken  also.  The  line  of 
fracture  usually  runs  from  its  level  on  the  crest  upward  and  backward,  and  under 
the  action  of  the  calf  muscles  and  the  weight  of  the  body  the  sharp  lower  end  of 
the  upper  fragment  frequently  protrudes,  making  the  fracture  compound. 

Fracture  at  about  the  same  level  from  direct  violence  is  also  very  common  on 
account  of  the  exposed  position  of  the  bone,  and  all  fractures  are  apt  to  be  com- 
pound as  a  result  of  the  large  proportionate  area  of  the  bone  which  is  subcutaneous. 

Fracture  of  the  shaft  at  the  upper  end  involving  the  knee-joint  is  rare,  and  is 
usually  from   either  direct  violence  or  a  fall  from   a  considerable  height, — "com- 
pression fracture."     Fracture  of  the  lower  end  of  the  shaft  involving 
the  ankle-joint  is  a  not  infrequent  complication  of  Pott's  fracture.  Fig.  406. 

Separation  of  the  lower  epiphysis  is  nearly  three  times  as  fre- 
quent as  that  of  the  upper.  It  is  caused  usually  by  a  considerable 
degree  of  violence,  and  in  fiftv  per  cent,  of  recorded  cases  has  been 
associated  with  fracture  of  the  lower  end  of  the  fibula  or  separation 
of  the  fibular  epiphysis,  in  which  case  the  displacement  is  often 
outward  ;  usually  it  is  backward. 

It  may  be  mistaken  for  dislocation  of  the  ankle.  In  patients 
from  eleven  to  seventeen  years  of  age  disjunction  of  the  epiph- 
ysis is  more  frequent  than  dislocation  ;  as  the  malleolus  and  the  foot 
go  backward  with  the  epiphysis,  the  inner  malleolus  preserves  its 
normal  relation  to  the  foot,  but  not  to  the  leg  or  outer  ankle.  In 
dislocation  the  reverse  is  the  case. 

The  ankle-joint  usually  escapes,  as  both  anteriorly  and  pos- 
teriorly the  synovial  membrane  is  below  the  epiphyseal  line.  The 
synovial  pouch  of  the  lower  tibio-fibular  joint  that  extends  upward 
between  these  two  bones  is  in  close  relation  to  that  line,  but  is  sepa- 
rated by  the  periosteum  which  is  continuous  over  the  epiphysis,  and 
thus  also  escapes  injury. 

Arrest  of  growth  is  not  common,  but  has  occurred,  and  severe 
ankle  sprains  in  the  young  should  be  treated  with  especial  care  on 
account  of  the  possibility  of  involvement  of  the  epiphyseal  joint  and 
later  disease  or  deformity. 

Disease  of  the  tibia,  if  infectious,  is  most  common  in  the  neigh- 
borhood of  its  two  epiphyses  and  at  the  junction  of  the  middle  and 
lower  thirds.      The  region  is  a  favorable  one  for   "  juxta-epiphyseal 
sprain,"  in  which  the  violence  is  expended  on  the  spongy  tissue  of 
the  diaphysis  near  the  epiphyseal  line.      "  Many  of  the  pains  called     ~Vi'bTa"and 'fibula."' 
'  growing  pains'  are  due  to  juxta-epiphyseal  sprain  or  injury.      Such 
a  sprain   is  often  nothing  but  the  first  degree  of  an  epiphyseal  separation,  in  the 
same  way  that  an  articular  sprain  is  nothing  but  the  first  degree  of  dislocation' ' 
(Poland). 

The  usual  causes — strain,  traumatism,  cold,  etc. — influence  the  localization  of 
tuberculous  disease  in  or  near  the  epiphyses.  If  recognized  early,  and  if  the 
infected  focus  is  removed  by  operation,  the  knee-  and  ankle-joints  will  usually  escape. 
In  the  later  stages  the  products  of  liquefaction  may  find  their  way  from  the  upper 
epiphyseal  line  to  the  knee-joint,  either  directly  through  the  intervening  half-inch  of 
bone  or  by  way  of  the  tibio-fibular  joint, — which  is  in  close  relation  to  the  epiphysis 
(Fig.  425), — and  then  to  the  subpopliteus  bursa,  which  always  communicates  with 
the  knee-joint  and  often  with  both  ;  or  they  may  gain  the  surface  of  the  tibia  and 
extend  upward  beneath  the  periosteum. 

If  the  lower  epiphysis  is  involved  a  similar  direct  or  indirect  infection  of  the 
ankle-joint  may  occur,  the  tibio-fibular  synovial  pouch  being  sometimes  first 
involved. 


392 


HUMAN    ANATOMY. 


Fig.  409. 

-Styloid  process 


Anterior  surface |j- 

Antero-internal  border- 
Antero-external  border 


Internal  surface; 


/ 


-Posterior  surface 


Tibialis' 
posticus    \ 


-Postero-external  border 


-Postero-internal  border 


nferior  interosseous  ligament  . 


X 


Facet  for  astragalus  { 

=■■',■' 

-Fossa 

"Ext.  lateral  ligament 

Right  fibula,  inner  aspect.     The  outline  figure  shows  the  areas  of  muscular  attachment. 


PRACTICAL    CONSIDERATIONS  :    THE    FIBULA.  393 

process.  It  is  strongest  at  and  below  the  middle  of  the  bone.  It  twists  backward 
and  is  lost  at  the  back  of  the  malleolus.  The  postero-internal  border  begins  at  the 
inner  side  of  the  back  of  the  head.  It  is  very  strong  at  about  the  middle.  It  ends 
in  the  last  quarter  by  joining  the  interosseous  ridge.  The  latter,  or  antero-internal 
border,  begins  poorly  marked  at  the  inner  side  of  the  neck,  soon  becomes  sharp, 
and  descends  rather  straighter  than  the  others  to  some  three  inches  above  the  lower 
end,  where  it  divides  into  two  lines  which,  ending  at  the  borders  of  the  articular  facet 
for  the  astragalus,  enclose  a  rough  space  for  ligaments.  The  interosseous  membrane, 
being  attached  to  this  ridge,  separates  the  front  of  the  bone  from  the  back.  The 
anterior  surface,  between  this  and  the  antero-external  border,  is  very  narrow.  It 
forms  a  part  of  a  hollow,  of  which  the  membrane  is  the  floor,  from  which  certain 
extensor  muscles  arise.  The  external  surface,  between  the  antero-external  and  the 
postero-external  borders,  is  a  characteristic  one,  presenting  for  more  than  the  lower 
half  a  shallow  groove  for  the  peroneus  longus  and  brevis,  which  sweeps  down  to 
the  back  of  the  malleolus  behind  the  subcutaneous  space  enclosed  by  the  splitting 
of  the  antero-external  border.  The  posterior  surface  is  bounded  by  the  postero- 
external border  and  by  the  postero-internal  till  that  border  joins  the  interosseous 
ridge,  which  bounds  the  surface  in  its  lower  part.  It  faces  backward  above  and 
inward  below.  The  nutrient  foramen,  running  downward,  enters  it  rather  above  the 
middle,  usually  near  the  postero-internal  border.  A  roughness  on  the  outer  part 
of  this  surface  is  for  the  origin  of  the  soleus.  The  i7iternal  surface,  relatively  broad 
in  the  greater  part  of  its  course,  looks  inward  to  the  hollow  between  the  two  bones. 
It  ends  in  the  last  quarter  where  the  oblique  ridge  joins  the  interosseous  one. 

The  lower  extremity  of  the  fibula  is  pointed,  forming  the  outer  malleolus,1 
which  projects  downward  and  a  little  outward.  Its  outer  surface  is  a  continuation  of 
the  subcutaneous  triangle,  and  the  greatest  prominence  near  its  back  is  in  line  with 
the  posterior  of  the  borders  of  the  space.  Most  of  the  internal  surface  is  occupied 
by  a  triangular  articular  facet  for  the  astragalus,  the  upper  part  of  which  is  nearly 
vertical,  while  the  lower  slants  outward.  Below  and  behind  this,  on  the  inner  side 
of  the  greatest  projection,  is  a  deep  hollow  for  part  of  the  external  lateral  ligament. 
The  malleolus  is  broader  behind  than  in  front,  presenting  a  groove  in  continuation 
of  the  external  surface  for  the  peroneal  tendons. 

Development. — The  centre  for  the  shaft  appears  in  the  eighth  fcetal  week  ; 
that  for  the  head  of  the  bone,  which,  according  to  the  usual  order  of  long  bones, 
should  develop  next,  does  not  come  till  after  that  of  the  malleolus.  The  latter  ap- 
pears in  the  second  year,  the  former  two  or  three  years  later.  The  lower  epiphysis 
is  probably  fused  with  the  shaft  by  eighteen  or  nineteen  and  the  upper  by  twenty. 

PRACTICAL    CONSIDERATIONS. 

The  upper  epiphysis  has  a  flat  lower  surface  and  is  about  on  a  level  with  the 
most  prominent  part  of  the  tibial  tubercle.  It  includes,  therefore,  all  that  portion 
of  the  head  of  the  fibula  into  which  the  biceps  tendon  and  external  lateral  ligament 
are  inserted.  Its  line  of  cartilage  at  and  after  the  thirteenth  year  is  in  close  relation 
with  the  synovial  membrane  of  the  tibio-fibular  joint.  Its  disjunction  is  favored 
by  its  situation  on  the  most  exposed  aspect  of  the  limb,  its  subcutaneous  position, 
and  the  insertion  into  it  of  the  biceps  muscle.  The  attachment  of  the  external 
lateral  ligament  also  enables  a  powerful  strain  to  be  brought  upon  it  in  over-adduction 
of  the  leg.  In  spite  of  these  favorable  circumstances,  the  protection  afforded  by 
the  slight  overhang  of  the  external  tuberosity  of  the  tibia  and  the  fixation  given  by 
the  strong  anterior  and  posterior  upper  tibio-fibular  ligaments  make  separation  of 
this  epiphysis  a  very  rare  occurrence.  Boyd  says  that  several  cases  are  known  in 
which  it  has  been  pulled  off  by  violent  contraction  of  the  biceps  in  an  effort  to  prevent 
falling.  It  is  then  felt  as  an  easily  recognizable  fragment  the  space  between  which 
and  the  diaphysis  is  increased  upon  extension  of  the  leg. 

Fracture  of  the  shaft  of  the  fibula  in  its  upper  two-thirds  occurs  from  direct 
violence  and  as  a  secondary  result  of  fracture  of  the  tibia.  In  spite  of  the  slender- 
ness  of  the  bone  and  its  position  on  the  outer  aspect  of  the  leg,  fracture  is  not  very 
frequent  because  of  (a)  its  elasticity,  which  is  marked  ;   (6)  its  protective  covering 

1  Malleolus  lateralis. 


394  HUMAN   ANATOMY. 

of  muscles  and  fascia  ;  and  (c)  its  backward  curvature,  which  carries  it  to  a  plane 
posterior  to  that  of  the  tibia,  which  thus  protects  it  both  internally  and  anteriorly 
from  direct  violence. 

Fractures  about  the  middle  of  the  lower  third  of  the  shaft,  and  especially  those 
about  7.5  centimetres  (three  inches)  from  the  ankle,  are  so  commonly  produced  by 
leverage  that,  whatever  their  exact  level,  most  of  them  may  be  grouped  as  instances 
of  Pott's  fracture,  although  an  effort  has  been  made  to  draw  between  them  distinc- 
tions that  are  ordinarily  academic  rather  than  practical. 

These  fractures  usually  result  from  over-abduction  of  the  foot.  When  that 
occurs  suddenly,  the  weight  of  the  body  being  upon  the  limb,  the  tension  first  comes 
upon  the  deltoid  ligament.  This  may  stretch  slightly  or  some  of  its  fibres  may  be 
torn,  or  there  may  be  a  small  detachment  from  its  malleolar  origin.  As  a  rule,  such 
a  case  ends  in  a  more  or  less  severe  sprain.  If  the  ligament  ruptures,  or  the  tip  of 
the  malleolus  is  torn  off,  or  the  malleolus  itself  is  fractured,  the  abduction  of  the 
foot  continues,  and  the  astragalus  is  subluxated  and  carried  against  the  inner  surface 
of  the  external  malleolus.  The  fibula  is  thus  converted  into  a  lever  of  the  first  order. 
The  force  is  applied  at  its  lower  end  ;  the  fulcrum  consists  of  the  stout  tibio-fibular 
ligaments,  which  are  often  stronger  than  the  bone  itself  and  which  are  rarely  com- 
pletely ruptured,  though  often  stretched  and  lacerated  ;  the  weight  or  resistance  is 
in  the  body  of  the  bone,  which  is  prevented  from  moving  inward  by  the  articulation 
of  its  upper  end  with  the  tibia.  As  soon,  therefore,  as  its  limit  of  elasticity  is  ex- 
ceeded, it  breaks  at  a  weak  (if  not  its  weakest)  point,  and  the  upper  end  of  the 
lever — i.e. ,  of  the  lower  fragment — is  forced  in  the  direction  opposite  to  that  of  the 
lower  end, — i.e. ,  the  malleolus  (Fig.  410).  The  impact  of  the  astragalus  and  the 
pull  of  the  ligaments  may  cause,  in  addition  to  the  fracture  of  the  tip  of  the  malleolus, 
fracture  of  the  anterior  or  of  the  outer  articular  edge  of  the  tibia.  If  the  tibio- 
fibular ligaments  rupture,  the  fibula  becomes  a  lever  of  the  second  order,  the 
fulcrum  shifting  to  its  upper  end.  The  dislocation  of  the  astragalus  outward  will  be 
more  marked.  The  bone  may  break  at  any  point,  but  the  fracture  is  still  likely  to 
be  within  the  limits  of  the  lower  third. 

Rose  and  Carless  have  adopted  the  following  useful  classification  based  on  the 
injury  to  the  inner  side  of  the  foot  or  to  the  tibia  itself.  It  divides  these  fractures 
into  four  groups,  the  term  Pott's  fracture  being  correctly  applied,  according  to  these 
authors,  to  the  first  two  only.  1.  The  internal  lateral  ligament  is  torn  through  ; 
the  intact  internal  malleolus  can  be  felt  projecting  beneath  the  skin  (Fig.  410,  A). 
2.  The  malleolus  is  torn  off  and  a  distinct  sulcus  can  be  felt  between  it  and  the  lower 
end  of  the  tibial  shaft  (Fig.  410,  B).  3.  The  interosseous  tibio-fibular  ligament  is 
ruptured  (or  the  flake  of  bone  at  the  tibial  attachment  is  torn  off)  ;  the  subluxation 
outward  is  very  marked  ;  either  the  inner  malleolus  or  the  deltoid  ligament  yields, — 
"  Dupuytren's  fracture"  (Fig.  410,  C).  4.  The  tibia  fractures  transversely  just 
above  the  base  of  the  malleolus  ;  the  lower  end  of  the  upper  fragment  may  be  mis- 
taken for  the  tip  of  the  malleolus  (Fig.  410,  Z>). 

The  less  frequent  accident  of  forcible  over-inversion  of  the  foot,  if  the  external 
lateral  ligament  holds,  produces  by  the  same  mechanism  a  similar  series  of  occur- 
rences. The  tip  of  the  external  malleolus  is  dragged  violently  inward,  the  tibio- 
fibular ligaments  act  again  as  a  fulcrum,  and  the  bone  is  apt  to  break  at  about  the 
same  level, — i.e. ,  from  5  to  7.5  centimetres  (two  to  three  inches)  above  the  joint, — 
the  upper  end  of  the  lower  fragment  being  carried  outward  instead  of  inward.  In 
these  cases  there  is  a  subluxation  of  the  astragalus  inward  which  not  infrequently 
results  in  a  fracture  of  the  inner  malleolus.  In  all  these  forms  of  fracture  the  lacera- 
tion of  ligamentous  structures  loosening  the  connection  of  the  foot  to  the  leg,  the 
upward  pull  of  the  calf  muscles,  and  the  weight  of  the  foot  itself  combine  to  produce 
a  subluxation  of  the  foot  backward  which  is  often  overlooked. 

The  cardinal  symptoms  of  the  common  form  of  Pott's  fracture  are  eversion  of 
the  foot,  prominence  of  the  inner  malleolus,  shortening  of  the  distance  from  the  front 
of  the  ankle  to  the  web  of  the  great  toe,  increased  width  between  the  malleoli,  and 
tenderness  over  (a)  the  space  between  the  tibia  and  the  external  malleolus  anteriorly, 
— i.e. ,  over  the  strained  or  torn  tibio-fibular  ligaments  ;  (6)  over  the  base  or  tip  or 
anterior  border  of    the  internal    malleolus, — i.e.,    over  a  ruptured  internal  lateral 


PRACTICAL    CONSIDERATIONS  :    THE    FIBULA. 


395 


ligament  or  a  fracture  of  the  malleolus  ;  and  (c)  over  the  fibula  from  two  to  four 
inches  above  the  tip  of  the  malleolus, — i.e. ,  over  the  fibular  fracture. 

The  lower  epiphysis  of  the  fibula  is  an  exception  to  the  rule  that  the  epiphyses 
of  long  bones  appear  first  at  the  end  from  which  the  nutrient  artery  is  directed,  and 
to  the  more  important  rule  that  the  chief  growth  of  the  long  bones  takes  place  at 
the  end  where  the  epiphysis  is  last  united  to  the  shaft  ;  in  the  other  long  bones  this 
is  also  the  end  from  which  the  nutrient  artery  is  directed.  We  have  seen  that  in 
the  upper  extremity,  the  nutrient  canals  being  directed  towards  the  elbow,  the  epiph- 
yses at  the  upper  end  of  the  humerus  and  the  lower  ends  of  the  radius  and  ulna  appear 
earlier  and  join  the  shaft  later  than  those, at  the  elbow,  and  that  thus  it  is  from  the 
shoulder  and  wrist  that  the  chief  growth  of  the  upper  limb  takes  place.  In  the  lower 
extremity,  the  nutrient  canals  being  directed  towards  the  hip  and  the  ankle,  the  lower 
epiphysis  of  the  femur  and  the  upper  epiphysis  of  the  tibia  appear  first  and  are  joined 
on  last,  and  the  chief  growth  of  the  lower  limb  takes  place  at  the  knee. 


Fig.  410. 


Showing  four  types  of  fract 


d  of  fibula  according  lo  classification  of  Rose  and  Carle 


In  the  case  of  the  fibula — the  upper  part  of  which  is  in  man  in  a  comparatively 
rudimentary  condition  (Poland)— the  exception  is  noted  to  avoid  confusion  in  the 
mind  of  the  student.  The  nutrient  artery  runs  downward,  but  the  lower  epiphysis 
is  both  the  first  to  appear  and  the  first  to  consolidate,  and  is  the  chief  seat  of 
growth.  It  is  not  of  great  practical  importance,  although  it  is  probable  that  in  most 
so-called  fractures  of '  the  extreme  lower  end  of  the  fibula  occurring  between  the 
twelfth  and  nineteenth  vears  there  has  been  a  disjunction  of  this  epiphysis.  The  so- 
lution of  continuity  would  then  be  below  instead  of  above  the  tibio-fibular  ligaments. 

The  synovial 'membrane  of  the  ankle-joint  is  attached  above  the  epiphyseal  line, 
and  that  articulation  is  therefore  likely  to  be  involved  more  frequently  than  in 
fractures  of  the  diaphysis.  This  fact,  together  with  the  importance  of  the  epiphysis 
in  its  relation  to  growth  of  the  bone,  should  cause  the  possibility  of  its  disjunction  to 
be  borne  in  mind.  If  arrest  of  growth  does  ensue,  a  condition  of  talipes  valgus  may 
result  from  the  relative  overgrowth  of  the  tibia.  For  the  relief  of  this  the  operation 
of  "  conjugal  chondrectomy"  — removal  of  the  lower  epiphyseal  cartilage  of  the  tibia 

has  been  suggested.      This  at  twelve  years  of  age  is  seventeen  millimetres  from  the 

tip  of  the  malleolus.      It  is  subcutaneous. 


396 


HUMAN   ANATOMY. 


Ant.  super,  tibi 
fibular  ligaments 


Sarcoma  of  the  fibula  attacks  the  upper  end  in  the  great  majority  of  cases. 
Osteophytes  are  not  infrequent  upon  the  median  margin  of  the  shaft  above  the  lower 
end. 

Landmarks. — In  extension  of  the  leg  the  position  of  the  head  of  the  fibula  is 
indicated  by  a  depression  on  the  posterior  part  of  the  outer  surface  of  the  leg  a  little 
below  the  level  of  the  tibial  tubercle,  corresponding  to  the  interval  between  the 
tendon  of  the  biceps  above  and  the  peroneus  longus  below.  The  head  is  subcu- 
taneous and  may  be  distinctly  felt  there.  In  flexion  it  projects  above  the  surround- 
ing surfaces  and  may  be  seen.  The  insertion  of  the  biceps  may  show  as  a  rounded 
prominence  at  the  base  of  the  styloid  profess.  The  synovial  membrane  of  the  knee 
descends  to  a  point  just  above  the  upper  level  of  the  head.  The  upper  half  of  the 
fibula  is  so  covered  by  muscles  that  its  outline  cannot  be  recognized  distinctly  by 
palpation.      In  the  lower  half  it  may  be  felt  through  the  muscles.      Its  lower  fifth  lies 

between  the  tendons  of  the  peroneus  tertius  and 
F'G-  411-  those   of    the   peroneus  longus    and    peroneus 

brevis,  and  is  subcutaneous,  as  is  the  malleolus. 
The  relation  of  the  plane  of  the  shaft  to  that  of 
the  tibia  should  be  remembered,  as  should  the 
plane  of  the  external  to  that  of  the  internal  mal- 
leolus (page  390).  The  tip  of  the  external 
malleolus  is  from  twelve  to  eighteen  millimetres 
(one-half  to  three-quarters  of  an  inch)  nearer  to 
the  heel  than  that  of  the  internal  malleolus.  The 
whole  malleolus,  viewed  from  without  inward, 
is  in  the  mid-line  (antero-posteriorly)  of  the 
ankle-joint.  It  becomes  abnormally  prominent 
in  cases  of  atrophy  of  the  peroneal  muscles, 
particularly  of  the  peroneus  longus. 

CONNECTIONS   OF   THE   TIBIA   AND 
FIBULA. 

These  are  the  superior  and  inferior  joints 
and  the  interosseous  membrane. 

The  Superior  Tibio-Fibular  Articu- 
lation '  (Fig.  411). — The  cartilage-covered  ar- 
ticular surfaces  already  described  vary  greatly 
both  in  direction  and  in  the  nature  of  their 
curves.  Perhaps  the  more  ordinary  arrange- 
ment is  for  the  tibial  facet  to  be  concave  in  a 
horizontal  and  convex  in  a  vertical  plane  ;  but 
the  converse  may  occur,  and  there  are  many 
intermediate  forms.  .  The  synovial  sac  extends 
upward  behind  and  may  communicate  with  the 
knee-joint.  The  capsule  is  very  strong,  except 
below,  and  especially  so  at  the  outer  side  where 
the  long  external  lateral  ligament  of  the  knee 
is  incorporated  with  it.  The  anterior  and  pos- 
terior superior  tibio-fibular  ligaments  2  are  strong 
fibres,  strengthening  the  capsule  and  passing 
outward  and  slightly  downward  from  the  tibia 
to  the  fibula. 

The  interosseus  membrane3  (Fig.  411) 
extends  from  the  head  of  the  fibula  down  along 
the  interosseous  ridges  of  both  bones  till  these 
split.       Its    fibres    run    in    the    main  downward 

and  outward,  but  in  the  upper  part  many  run  downward  and  inward.      There  is  a 

large  opening  at  the  top  above  the  membrane  or  through  it. 

The  Inferior  Tibio-Fibular  Articulation4  (Fig.  411). — This  joint  is  essen- 

1  Articulatio  tibiolibularis.      -  Ligg.  capituli  fibulae  anterius    et  posterius       ^Mernb.   interossea  cruris.      *  Syndesmosis 


Anterior  border- 


Ant,  infer,  libio-fibul 
ligament 


ligaments  from  before. 


THE  BONES  OF  THE  LEG  AS  ONE  APPARATUS. 


397 


tially  ligamentous,  though  the  articular  cartilage  of  the  ankle-joint  extends  for  a  few 
millimetres  onto  the  opposed  sides  of  each  bone. 

The  inferior  ligaments  are  the  interosseous,  the  anterior  and  posterior,  and  the 
tra?isverse.  The  interosseous  ligament  is  a  thickened  continuation  of  the  mem- 
brane, consisting  of  short  fibres  connecting  the  rough  surfaces  bounded  by  the  split- 
ting of  the  interosseous  ridges. 

The  anterior  and  posterior  ligaments1  (Fig.  411,  412)  are  strong  bands  situ- 
ated respectively  on  the  front  and  the  back  of  the  tibia  and  running  downward  and 
outward  to  the  fibula.  The  anterior  deepens  the  socket  but  slightly,  while  the 
posterior,  reaching  nearly  half-way  down  to  the  malleolus,  makes  a  considerable 
addition  to  the  back  of  the  joint.      The  transverse  ligament  (Fig.  412)  containing 


Fig.  412. 


Ant.  tibiofibular  ligament 


Capsule  reflected 


Ant.  lateral  ligament 


Middle  lateral  ligament 


Outer  malleolus 


Deltoid  ligament 


ransverse  ligament 

Pad  of  fat 
Post,  external  lateral  ligament 

Socket  of  right  ankle-joint  from  below 


Capsule 
Post,  tibio-fibular  ligament 


probably  elastic  fibres,  runs  obliquely  from  the  back  of  the  lower  border  of  the 
tibia  to  the  tip  of  the  outer  malleolus.  It  projects  into  the  joint,  the  capsule  form- 
ing a  pouch  between  it  and  the  posterior  tibio-fibular  ligament.  It  is  closely  con- 
nected at  the  fibula  with  the  posterior  fibulo-astragaloid  ligament.  The  two  have 
the  appearance  of  diverging  bundles  of  the  same  structure.  The  synovial  cavity  is 
prolonged  some  three  millimetres  upward  between  the  bones.  The  back  part  of  the 
crack  between  the  bones  is  concealed  by  a  pad  of  fat  (Fig.  412)  covered  by 
synovial  membrane  projecting  into  the  joint.  It  advances  or  recedes  between  the 
bones  according  to  changes  of  position. 

Movements. — The  motions  between  the  tibia  and  the  fibula  are  slight  and 
not  very  definite.  The  head  of  the  fibula  may  play  a  little  forward  and  backward, 
and  the  bone  may  rotate  on  its  long  axis.  These  motions  are  resisted  alternately 
by  the  anterior  and  posterior  ligaments  at  both  ends. 

THE  BONES  OF  THE  LEG  AS  ONE  APPARATUS. 
Surface  Anatomy. — The  upper  part  of  this  support  consists  of  the  head  of 
the  tibia  with  that  of  the  fibula  well  back  on  the  outer  side.  The  framework  nar- 
rows to  the  junction  of  the  middle  and  lower  thirds,  where  the  tibia  is  nearly  at  its 
smallest  and  seems  to  bend  towards  the  fibula.  Below  this  it  broadens  for  the 
socket  of  the  ankle.  The  fibula  in  the  lower  third  is  close  to  the  tibia  and  no  longer 
so  much  behind  it,  which  is  due  in  part  to  the  subsidence  of  the  crest  of  the  tibia. 
The  difference  of  relations  is  shown  by  sections  at  three  levels  (Fig.  413).  The 
whole  apparatus  is  described  as  having  three  borders  and  three  surfaces.  As  the 
details  have  been  given  with  the  bones,  the  chief  features  only  are  here  enumerated. 
The  anterior  border  is  the  crest  of  the  tibia  ;  the  posterior  and  internal  border  is  the 
posterior  border  of  the  same  bone ;  between  them  is  the  subcutaneous  internal  surface. 
The  posterior  and  external  border  is  the  postero- external  border  of  the  fibula.  Thus 
there  remain  an  antero-external  and  a  posterior  surface,  each  of  which  is  formed  in 

1  Ligg.  malleoli  lateralis  anterius  et  posterius. 


398 


HUMAN   ANATOMY. 


part  by  the  interosseous  membrane.  The  a?itero-external  surface  presents  the  fol- 
lowing features:  (i)  a  large  surface  of  the  tibia,  looking  outward  as  far  as  the 
lower  third  and  then  forward  ;  (2)  the  interosseous  membrane  ;  (3)  a  narrow'  sur- 
face of  the  fibula,  bounding  externally  the  fossa  of  the  front  of  the  leg,  shallow 
above,  deep  and  narrow  below  ;  (4)  the  antero-external  border  of  the  fibula,  split- 
ting below  to  enclose  the  subcutaneous  surface  above  the  outer  malleolus  ;  (5)  the 
grooved  surface  of  the  fibula  occupied  by  the  peronei. 

The  posterior  surface  presents,  continuing  in  the  same  course  :  (1)  the  posterior 
surface  of  the  fibula,  looking  backward  above,  inward  below  ;  (2)  the  postero-in- 
ternal  border,  ending  in  the  interosseous  ridge  ;  in  the  upper  two-thirds  this  over- 
hangs a  deep  hollow  ;  (3)  the  internal  surface,  which  ends  below  with  the  preceding 
border;  (4)  the  interosseous  membrane;  (5)  the  posterior  surface  of  the  tibia. 
The  interosseous  membrane  is  at  the  bottom  of  a  much  deeper  gutter  than  in  front, 
which  also  becomes  very  narrow  below. 

The  outward  twist  of  the  ankle  has  been  mentioned,  and  it  has  been  shown  that 
this  depends  on  the  twist  of  the  tibia.  It  is  to  be  noticed  that  while  the  antero- 
external,  the  postero-external,  and  the  postero-internal  borders  of  the  fibula  run  as  if 


Fig.  413. 


Anterior  border 


Internal  border 

Antero-ext.  border 

Postero-int.  bord< 
Postero-ext.  bord 


terior  border 


Anterior  border 


Antero-ext.  border 

Internal  border 

Postero-ext.  border 


Postero-ext.  border 
Sections  across  the  bones  of  right  leg,  showing  their  relations  at  different  levels  ;  seen  from  above.     A,  near  head  of 
fibula  ;  B,  near  the  middle  ;  C,  a  little  above  the  ankle. 

the  lower  end  of  that  bone  had  been  twisted  outward,  the  same  is  not  true  of  the 
borders  and  surfaces  of  the  tibia.  On  the  contrary,  the"  crest,  with  the  surface  on 
each  side  of  it,  slants  in  the  lower  half  of  the  leg  downward  and  inward.  It  is  as 
if  these  borders  of  both  bones  had  been  twisted  away  from  the  median  line  of  the 
leg,  one  to  each  side,  and  that  the  interosseous  ridge  had  stayed  straight.  There 
seems  to  be  no  relation  between  the  degree  of  forward  bend  of  the  neck  of  the 
femur  and  the  outward  twist  of  the  socket  of  the  ankle.  Probably  both  have  an 
influence  on  the  direction  of  the  foot,  but  it  depends  chiefly  on  the  latter.  It  is  un- 
warranted, therefore,  to  expect  all  children  to  turn  out  the  toes  alike.  The  whole 
of  the  front  and  sides  of  the  head  of  the  tibia  is  easily  felt,  but  it  is  thickly  covered 
behind.  The  top  of  the  tuberosities  is  clear  on  either  side,  and  in  front  the  whole 
of  the  tubercle  can  be  explored  when  the  tendon  is  relaxed.  The  head  of  the  fibula 
is  distinct  far  back  on  the  outer  side.  Descending  the  leg,  it  is  easy  to  follow  the 
sharp  crest  of  the  tibia  into  the  lower  third,  and  the  internal  subcutaneous  surface 
down  to  the  malleolus.  The  external  surface,  where  it  becomes  anterior  above  the 
ankle,  is  plain  in  spite  of  the  tendons  crossing  it.  The  shaft  of  the  fibula  is  so 
covered  with  muscles  that  little  more  than  its  general  position  is  to  be  made  out 
above  the  triangular  subcutaneous  surface  over  the  outer  malleolus,  which  latter  is 
also  easily  explored.  The  relations  of  the  malleoli  are  considered  with  the  foot 
(page  449). 

THE    PATELLA. 

The  knee-pan,  the  largest  sesamoid  bone,  is  triangular  or  shield-shaped.  The 
anterior  surface  is  covered  by  the  tendinous  fibres  of  the  quadriceps,  which  re- 
place the  periosteum  and  mark  the  surface  with  longitudinal  lines.  Jagged  spines 
from  the  ossification  of  the  tendon  are  often   found  at   the  top.      The  transverse 

1  In  the  transverse  sections  (Fig.  413)  this  surface  is  exceptionally  small. 


THE  PATELLA. 


399 


diameter  is  usually  rather  larger  than  the  vertical,  especially  in  strong,  and  conse- 
quently in  male,  bones. 

The  base1  is  above  with  a  slightly  curved  outline,  and  the  apex*  below,  usually 
somewhat  internal  to  the  middle.      The  outer  lower  border  is  more  oblique  than  the 


Fig.  414. 


Tendon  of  quadriceps  extensor 


Ligamentum  patellae  Ligamentum  patellae 

Right  patella,  anterior  and  posterior  surfaces. 

inner.      The  posterior  surface  is  divided  into  an  upper  articular  part  and  a  much 
smaller  non-articular  one  below,  in  which  the  bone  is  thinner  at  the  expense  of  the 


Fig.  415 


Prepatellar  bursa 


Alar  ligament 


Cavity  of  joint 

Lateral  part  of  capsule 


Posterior  crucial  ligament 
Horizontal  frozen  section  through  right  knee-joint. 


posterior  surface  and  is  covered  by  the  fibres   of  the  ligamentum   patellae.      The 
upper  part,  covered  with  articular  cartilage  and  forming  a  part  of  the  knee-joint,  is 

1  Basis  patell 


-  Apex  patella 


cartilage  and  forming  a  part  of  the  knee-joint,  is 


400  HUMAN    ANATOMY. 

much  broader  transversely  than  vertically.  The  outer  three-fifths  or  so,  which 
plays  on  the  external  condyle,  is  concave  transversely  and  the  inner  two-fifths  con- 
vex. The  convexity  begins  with  a  vertical  prominence  which  marks  the  greatest 
thickness  of  the  bone  and  appears  to  divide  the  hind  surface  into  two  parts,  as  a 
horizontal  section  shows,  the  surface  receding  from  it  on  either  side.  Neverthe- 
less, the  whole  inner  part  is  convex,  as  described.  Vertically,  both  sides  are  slightly 
concave.  A  close  examination  of  a  fresh  specimen  shows,  what  rarely  is  to  be  seen 
on  the  dry  bone,  that  the  articular  surface  is  to  be  further  subdivided.  A  narrow 
vertical  facet  is  seen  along  the  inner  side,  constituting  a  surface  which  rests  on  the 
edge  of  the  inner  condyle  in  extreme  flexion.  The  rest  of  the  articular  surface  is 
divided  into  three  horizontal  zones,  one  above  another,  by  two  transverse  lines.  The 
top  of  the  bone  is  very  thick;  most  of  it  being  occupied  by  the  insertion  of  the 
rectus.  The  capsule  of  the  knee-joint  is  inserted  all  around  the  articular  surface 
some  two  or  three  millimetres  from  its  edge,  so  that  a  little  of  the  border  is  enclosed 
in  the  joint.      Several  nutrient  foramina  are  found  on  the  anterior  surface. 

Development. — The  patella  appears  as  a  cartilaginous  point  in  the  course  of 
the  third  fcetal  month.  Ossification  begins  by  the  deposit  of  several  granules  some 
time  between  two  and  five  years.  These  soon  unite  into  a  central  mass,  from  which 
ossification  spreads,  more  rapidly,  however,  in  the  deeper  parts.  The  bone  is  not 
fully  formed  till  after  puberty,  perhaps  not  before  eighteen. 

THE   LIGAMENTUM    PATELLAE. 

This  name  is  applied  to  the  tendon  of  the  quadriceps  extensor  muscle,  in  which 
the  patella  is  a  sesamoid  bone  (Fig.  416).  It  is  a  strong,  flattened,  fibrous  band 
some  two  inches  long.  Just  below  the  knee-pan  it  is  at  least  one  and  one-quarter 
inches  broad,  but  at  its  insertion  into  the  front  of  the  upper  part  of  the  tuberosity 
of  the  tibia  its  breadth  is  not  over  one  inch.  The  line  of  insertion  is  oblique,  the 
outer  end  being  the  lower.  Just  above  the  insertion  a  synovial  bursa  lies  between 
the  tendon  and  the  bone.  A  mass  of  fat  above  the  bursa  separates  the  tendon  from 
the  capsule.  The  tendon  is  fused  at  the  sides  with  fibrous  expansions  from  the 
quadriceps. 

THE    KNEE-JOINT. 

This  is  a  compound  joint  between  the  femur  and  the  tibia,  the  patella  being  a 
sesamoid  bone  in  the  tendon  of  the  extensor  of  the  leg,  incorporated  in  the  front  of 
the  capsule.  The  patella  is  in  relation  to  the  femur  only,  and  sometimes  it  is  con- 
venient to  consider  the  knee-joint  as  the  sum  of  three  distinct  ones, — namely,  that 
between  femur  and  patella,  and  one  for  each  condyle  with  the  tibia.  The  joint  is 
enclosed  by  a  capsule  partially  subdivided  in  many  ways.  Fibrocartilaginous  disks, 
the  semilunar  cartilages  on  the  top  of  the  tibia,  tend  to  subdivide  the  joint  below 
each  condyle  into  an  upper  and  a  lower  half.  The  crucial  ligaments  nearly  cut  off 
communication  between  the  parts  of  the  joint  under  each  condyle.  The  mucous 
ligament  assists  in  this,  and  with  the  alar  ligaments  tends  to  isolate  the  patella. 

Discussion  of  the  knee-joint  calls  for  the  description  of  the  following  component 
structures  : 

The  Capsule  and  its  Accessories. 

The  Semilunar  Cartilages  and  their  Accessories. 

The  Crucial  Ligaments. 

The  Subpatellar  Fat  with  the  Ligamentum  Mucosum  and  the  Ligamenta 
Alaria. 

The  Synovial  Membrane. 

Certain  Bursae. 

The  capsule  (Fig.  416)  arises  from  the  femur,  mingling  with  the  periosteum, 
a  little  above  the  anterior  articular  surface  ;  from  the  sides  of  the  condyles  as  high 
as  the  level  of  the  lateral  tuberosities  ;  from  the  back  one  centimetre  beyond  the 
highest  point  that  the  cartilage  reaches  on  the  top  of  the  condyles  ;  and  from  a 
slightly  lower  level  above  the  intercondyloid  notch.  It  is  attached  in  front  around 
the  articular  surface  of  the  knee-pan  and  inferiorly  to  the  tibia  all  around,  but  a 


THE    KNEE-JOINT. 


401 


little  below  the  top  ;  for  the  articular  cartilage  is  continued  over  the  border  onto 
the  sides.  It  is  lower  at  the  back  of  the  outer  tuberosity,  where  the  joint  sometimes 
joins  that  of  the  head  of  the  fibula.  It  is  attached  to  the  periphery  of  the  semi- 
lunar cartilages.  This,  which  is  the  capsule  proper,  is  very  much  strengthened  by 
surrounding  structures.  On  each  side  a  strong  fibrous  layer  passes  from  the  con- 
dyles to  the  patella  {ailerons  de  la  roiule  of  French  authors)  (Fig.  418).  Super- 
ficial to  this,  and  not  adherent  to  it,  come  the  aponeurotic  fibres  of  the  vasti,  and 
still  more  superficially  the  fascia  lata.      They  fuse  with  the  capsule  at  the  sides  of 

Fig.  416. 

Tendon  of  quadriceps  extensor 


Capsule 
External  lateral  ligament 

Tendon  of  biceps 


rnal  lateral  ligament 
Ligamentum  patellae 


Fibula        Interosseous        Tibia 

Right  knee-joint  from  before. 


the  patella,  but  extend  over  the  latter  in  two  tolerably  distinct  layers.  Both  heads 
of  the  gastrocnemius  and  the  plantaris  are  to  a  great  extent  incorporated  with  the 
capsule" behind  (Fig.  417).  The  tendon  of  the  semimembranosus,  which  has  its 
chief  insertion  in  the  groove  in  the  inner  side  of  the  tibia  where  it  is  covered  by  the 
more  superficial  lateral  fibres  of  the  capsule,  sends  across  the  back  of  the  capsule 
strong  transverse  diverging  fibres,  known  as  the  ligament  of  Winslow,  some  of 
which  are  directly  continuous  with  the  outer  head  of  the  gastrocnemius  (Fig.  417). 
Some  longitudinal  fibres  near  the  back  of  the  inner  side,  only  artificially  separable 

26 


4Q2  HUMAN    ANATOMY. 

from  the  rest,  have  been  called  the  internal  lateral  ligament1  (Fig.  416J.  The 
long  external  lateral  ligament2  (Fig.  41S),  though  connected  with  the  capsule 
by  areolar  tissue  on  its  deep  surface,  is  truly  a  distinct  ligament.  It  arises  from  the 
external  tuberosity  of  the  femur  and  runs  as  a  flattened  cord  downward  and  some- 
what backward  to  the  outer  surface  of  the  head  of  the  tiouia,  almost,  or  quite, 
splitting  the  tendon  of  the  biceps,  which  is  inserted  external  to  it,  overlapping  the 
ligament  in  front  and  behind.  A  shorter  band  placed  more  posteriorly  and  insepa- 
rable from  the  capsule  can  often  be  traced  to  the  styloid  process.     The  tendon  of  the 

Fig.  417. 


Fibres  to  capsule  from     ffflfWf 
tendon  of  adductor  magnus—ft-f/'£/ 

Int.  head  of  gast 

Bursa  opening  into  joint 


External  head  of  gastrocnemius; 


Tendon  of  semimembranosus 


Posterior  ligament  of  Winslow- 


Head  of  plantaris 


xternal  condyle 

Bursa  opening  into  joint 


Popliteus  tendon 

External  lateral 

ligament 
Tendon  of  biceps 


perior  tibio-fibular  ligament 


r  ""■>  1 

Interosseous         Fibula 
membrane 


Right  knee-joint  from  behind. 


popliteus  entering  the  joint  from  behind  is  incorporated  with  the  capsule  beneath 
the  long  external  lateral  ligament,  as  described  with  the  bursae. 

The  semilunar  cartilages  (Figs.  419,  420)  are  two  crescentic  disks  of  fibro- 
cartilage  lying  each  on  top  of  one  of  the  tuberosities  of  the  tibia,  with  their  thick 
outer  borders  at  the  periphery  attached  to  the  capsule  and  their  thin  edges  free,  so 
as  partially  to  divide  the  joint  into  an  upper  and  a  lower  part.  The  pointed  ends 
{comua)  are  fastened  near  the  middle  line  of  the  joint.  Those  of  the  external 
cartilage 3  are  attached  to  the  front  and  back  of  the  fibular  facet  of  the  spine  of  the 
tibia  and  to  the  inner  border  of  the  raised  articular  facet  before  and  behind  it.      The 

1  Lig.  collaterale  tibiale.     -  Lig.  collaterale  fibulare. 


THE    KNEE-JOINT. 


403 


posterior  horn,  moreover,  joins  the  posterior  crucial  ligament.  There  is  not  more 
than  one  centimetre  between  the  two  horns,  so  that  this  cartilage  is  almost  circular. 
The  internal  cartilage  '  is  C-shaped.  The  anterior  horn,  thin  and  fibrous,  is  in- 
serted into  the  rough  surface  near  the  anterior  border  at  no  very  definite  point. 
Sometimes  it  runs  into  the  transverse  ligament  without  any  fixed  ending  ;  some- 
times the  extreme  point  is  free.  The  posterior  horn  is  attached  to  the  back  of  the 
tibial   facet   of  the  spine   and   to  the   edge  of   the  articular  facet  behind   it.      The 

Fig.  418. 


Inner  head  of 
gastrocnem 


Popliteus  tendon  and 
opening  into  joint 


Extensor  tendon 


Subrectal  bursa 


Superficial  band  to  pate 


gamentum  patellae 


Anterior  tibio-fibular  ligament 


Tendon  of  biceps' 

Head  of  fibula 


Right  knee-joint,  external  aspect.     The  extensor  tendon  is  drawn  forward  and  upward. 


distance  between  the  horns  is  about  three  centimetres.  The  anterior  horn  of  the 
internal  cartilage  may  not  come  into  contact  with  the  femur.  The  vertical  diameter 
of  the  cartilages  at  the  periphery  is  from  six  to  eight  millimetres.  The  breadth 
varies  in  different  joints,  ranging  from  one  to  nearly  two  centimetres.2  The  broadest 
part  is  near  the  back  of  the  internal  one,  but  the  external  is,  on  the  whole,  the 
broader.  It  is  said  sometimes  to  completely  divide  that  half  of  the  joint.  The 
free  border  is  very  thin  and  may  present  fine  prolongations  with  scalloped  edges. 
2  For  various  statistics,  consult  Higgins  :  Journal  of  Anatomy  and  Physiology,  vol.  xxix.j 


404 


HUMAN   ANATOMY. 


The  lower  surfaces  of  the  disks  adapt  themselves  to  the  top  of  the  tibia,  the  outer 
cartiiage  concealing  the  convexity  at  the  back  of  the  tuberosity.  The  upper  surfaces 
form  cups  to  receive  the  femoral  condyles.  At  the  sides  of  the  spine,  where  the 
cartilages  are  wanting,  the  cups  are  completed  by  the  upward  slope  of  the  tuber- 
osities. 

The  coronary  ligaments  (Fig.  420)  are  parts  of  the  capsule  connecting  the 
periphery  of  the  semilunar  cartilages  with  the  tibia.  They  are  of  little  strength  and 
allow  more  or  less  motion.  Those  of  the  external  cartilage  are  more  than  two  cen- 
timetres long  at  the  front  and  1.3  centimetres  at  the  back,  while  those  of  the  internal 
are  from  four  to  five  millimetres.  Thus  the  external  cartilage  can  move  very  freely 
on  the  tibia,  both  from  the  length  of  these  ligaments  and  from  the  approximation  of 
its  horns,  while  the  internal  can  move  but  little.      This  has  an  important  influence 


Patella 

Alar  ligament 

Internal  semilunar  cartilage^ 

Posterior  crucial  ligament 


Anterior  wall  of  right  knee-joint 


Alar  ligament 

Anterior  crucial  ligament 

External  semilunar  cartilage 
Tendon  of  popliteus 

Capsule  reflected 


behind,  the  lower  end  of  the  femur  having  been  removed. 


on  the  mechanics  of  the  joint.  The  popliteus  muscle  is  attached  to  the  outer, 
which  is  significant  in  the  same  connection. 

The  transverse  ligament '  (Fig.  420)  is  a  band,  usually  ill-defined  and  often 
quite  wanting,  which  connects  the  cartilages  at  the  front  of  the  knee,  running  from 
the  convexity  of  the  outer  to  near  the  anterior  cornu  of  the  inner  and  sometimes 
into  it.      It  is  closely  attached  to  the  capsule  in  front. 

The  crucial  ligaments  2  (Figs.  419,  420)  are  two  broad,  thick  bands,  the  strong- 
est in  the  joint.  The  anterior  arises  from  the  depression  in  front  of  the  spine  of  the 
tibia,  close  to  the  external  semilunar  cartilage,  and  runs  upward,  backward,  and 
outward  to  the  back  of  the  inner  side  of  the  outer  condyle.  The  posterior,  the 
stronger,  arises  from  the  back  of  the  groove  at  the  posterior  aspect  of  the  top  of  the 
bone,  and  from  its  outer  border,  leaving  the  floor  of  the  groove  and  the  transverse 
piece  of  the  spine  of  the  tibia  free  and  covered  by  synovial  membrane.  It  is  also 
closely  connected  with  the  external  semilunar  cartilage.  It  runs  forward,  upward, 
and  a  little  inward  to  the  front  of  the  outer  side  of  the  inner  condyle  and  of  the 

1  Lig.  transversum  genu.     cLigamenta  cruciata  genu. 


THE    KNEE-JOINT. 


405 


intercondylar  notch.  The  fibres  from  the  external  semilunar  cartilage  run  along  it 
in  a  varying  position,  but  usually  as  a  well-defined  bundle.  When  the  joint  is 
straight  the  surface  of  the  anterior  ligament  looks  approximately  forward  and  up- 
ward, its  line  of  insertion  being  about  vertical  ;  when  it  is  fully  flexed  the  outer 
edge  is  brought  forward  so  that  the  ligament  is  somewhat  twisted  on  itself  and  the 
upper  part  .looks  inward,  the  line' of  insertion  slanting  slightly  downward  and  back- 
ward. In  the  former  position  the  posterior  crucial  has  the  anterior  surface  looking 
outward,  forward,  and  downward,  the  line  of  insertion  being  .horizontal,  with  the 
front  external.  With  the  knee  flexed  the  ligament  is  closely  applied  to  the  internal 
condyle. 

The  Subpatellar  Fat,  the  Ligamentum  Mucosum,  and  the  Ligamenta 
Alaria  (Figs.  419,  423). — If  the  joint  be  opened  by  dividing  the  capsule  just  above 

Fig.  420. 

Patellar  surface 


Capsule  reflected 


External  condyk 


Ant.  crucial  ligament 
Ext.  semilunar  cartih 

Transverse  ligament 
Coronary  ligament 
Edge  of  superior  surface  of 


Capsule  reflected 

Post  crucial  ligament 
Internal  condyle 

Interna!  semilunar 
cartilage 

Coronary  ligament 
Bursa  beneath  ligamentum  patella: 


-Tuberosity  of  tibia 
Right  knee-joint,  opened  and  the  knee  flexed.     Seen  from  before. 

the  patella,  or,  better,  by  splitting  the  patella  and  turning  one-half  to  either  side,  a 
large  mass  of  fat  is  seen  inside  the  capsule,  below  the  patella  and  above  the  front 
and  top  of  the  tibia,  covered  by  the  synovial  membrane.  This  mass  has  a  definite 
shape,  though,  of  course,  subject  to  change  by  pressure.  It  is  perhaps  best  described 
as  pyramidal,  the  base  being  towards  the  surface  between  the  knee-pan  and  the  tibia. 
When  the  knee  is  straight  it  fills  the  patellar  surface  of  the  femur  and  laterally 
passes  under  the  condyles,  filling  the  space  between  them  and  the  tibia.  It  reaches 
to  the  semilunar  cartilages.  Towards  the  joint  it  has  two  free  angles,  a  larger  one 
below  entering  between  the  bones  as  just  described  and  a  smaller  one  above.  The 
lateral  halves,  including  the  synovial  covering,  are  called  the  alar  ligaments  l  (Figs. 
419,  423).  From  the  middle  of  this  mass  below  the  patella  runs  a  collection  of  fat 
with  areolar  and  elastic  tissue,  invested  by  synovial  membrane,  to  the  top  of  the  inter- 
condylar notch.  This  is  the  ligamentum  mucosum,2  of  little  strength  and  not 
absolute  constancy,  which  acts  as  a  guy,  preventing  the  mass  of  fat  from  falling 
away  from  the  femur.  There  are  also  collections  of  fat  about  the  crucial  ligaments 
and  at  the  back  of  the  joint  between  the  posterior  crucial  and  the  capsule. 

The  synovial  membrane  lines  the  capsule  in  a  general  way,  but  is  separated 


406 


HUMAN   ANATOMY. 


from  it  by  the  masses  of  fat  just  described.  It  surrounds  the  lower  halves  of  the 
crucial  ligaments  with  the  fat  in  a  common  envelope,  so  that  there  is  in  nature  no 
interval  between  them.  There  is  but  a  small  chink  between  the  upper  halves, 
though  each  has  its  separate  sheath.  The  back  of  the  posterior  crucial  is  partly  un- 
covered by  synovial  membrane.  Synovial  fringes  formed  by  the  membrane  and 
more  or  less  underlying  tissue  project  from  the  folds  of  the  alar  ligaments,  from  the 
ligamentum  mucosum,  and  from  near  the  borders  of  the  patella. 

Bursae. — ( I ).  The  most  important  is  a  large  one  under  the  extensor  tendons, 
just  above  the  capsule,  with  which  it  usually  communicates.  It  probably  in  most 
cases  develops  independently  of  the  capsule,  which  then  lies  in  front  of  its  lowest 

Fig.  421. 

Posterior  surface  of  femur 


Gastrocnemius- 

Back  of  capsul 

Internal  condyle 

Post,  crucial  ligament 

Int.  semilunar  cartilage 


Gastrocnemius 


Insertion  of  anterior 
crucial  ligament 

External  condyle 

Ext.  semilunar  cartilage 
Tendon  of  popliteus 
Tendon  of  biceps 


Frontal  frozen  section  of  right  knee-joint  passing  through  condyles  and  behind  shaft  of  femur.    Seen  from  behind. 
The  superior  tibio-fibular  joint  is  opened. 

part,  a  communication  forming  subsequently.  Such  a  communication  almost 
always  exists  in  the  adult,  less  frequently  in  the  infant.  The  opening  may  be  small 
and  well  defined  or  so  large  that  the  cavities  of  the  joint  and  bursa  give  no  sign  of 
subdivision.  This  carries  the  cavity  of  the  joint  any  part  of  three  finger-breadths 
above  the  knee-pan.  It  is  possible  that  sometimes  there  is  a  communication  from 
the  beginning.  (2)  Prepatellar  bursa  are  found  on  the  front  of  the  patella 
at  different  depths.  Directly  below  the  skin  is  the  superficial  fascia,  often  lamel- 
lated  and  adherent  to  the  layer  beneath  it.  According  to  Bize,1  (a)  a  bursa  is 
present  in  this  superficial  layer,  usually  over  the  lower  half  of  the  patella,  in  eighty- 
eight  per  cent,  of  knees  examined.  The  next  layer  is  an  aponeurotic  one  continu- 
ous with  the  fascia  lata,  beneath  which  (6)  a  bursa  is  found  in  ninety-five  per  cent., 
most  commonly  at  the  inner  inferior  part.      A  still  deeper  (Y)  bursa  occurs  beneath 

1  Journal  de  l'Anat.  et  de  la  Phys.,  1896. 


THE    KNEE-JOINT. 


407 


the  fibrous  layers  from  the  tendon  of  the  quadriceps  over  the  lower  part  of  the  bone 
in  eighty  per  cent.  (3)  A  large  and  constant  bursa  lies  on  the  smooth  anterior 
surface  of  the  tubercle  of  the  tibia  beneath  the  ligamentum  patella?,  which  is  inserted 
into  the  lower  part.  It  extends  upward  to  about  the  level  of  the  top  of  the  tibia, 
from  which  it  is  separated  by  the  fat  below  the  knee.  It  practically  never  communi- 
cates with  the  knee-joint.  As  the  tendon  before  it  is  inserted  obliquely,  descend- 
ing lower  on  the  outer  side,  the  shape  of  the  bursa  is  roughly  triangular.  The 
greatest  diameter  is  the  transverse  one  at  the  top,  the  outer  border  is  not  quite  so 
long,  and  the  inner  about  half  the  length  of  the  outer.  The  breadth  is  from  3  to  4 
centimetres,  the  outer  border  from  2.5  to  4,  and  the  inner  from  1.5  to  2.5  centi- 
metres.     (4)   A  subcutaneous  bursa  is  often  found  over  the  tuberosity  of  the  tibia 


Fig.  422. 


Posterior  crucial  ligament 


Anterior  crucial  ligament 


-tj-t  External  semilunar 
— Jul!     cartilage 
Capsule 


Frontal  section  through  middle  o 


joint.     Seen  from  behind. 


and  (5)  another  over  the  ligament  of  the  patella.  At  the  back  of  the  knee  there  are 
several  bursae.  (6)  The  largest  is  that  beneath  the  inner  head  of  the  gastrocne- 
mius (Fig.  426),  which  later  in  life  often  connects  with  the  joint.  It  is  usually 
prolonged  between  the  gastrocnemius  and  the  tendon  of  the  semimembranosus. 
(7)  A  bursa  is  commonly  found  between  the  long  lateral  ligament  and  the  tendon 
of  the  popliteus  as  it  passes  beneath  it,  and  another  between  the  ligament  and  the 
tendon  of  the  biceps. 

The  relations  of  the  tendon  of  the  popliteus  muscle  are  so  important  as  to  re- 
quire a  separate  description.  The  muscular  belly  is  usually  separated  from  the  back 
of  the  tibia,  near  the  top,  by  a  prolongation  of  the  capsule  between  the  tibia  and  the 
back  of  the  external  semilunar  cartilage,  which  is  described  by  some  as  a  bursa  com- 
municating with  the  joint.  According  to  either  view,  there  is  a  deficiency  of  the 
coronary  ligament  at  this  point.  The  muscle  is  connected  beyond  this  with  the 
outer  side  of  the  external  semilunar  cartilage.     Passing  above  this,  it  becomes  a  part 


408 


HUMAN  ANATOMY. 


of  the  capsule,  and  on  reaching  its  insertion  it  makes  a  more  or  less  prominent  pro- 
jection into  the  joint.  There  may  or  may  not  be  a  projection  of  the  capsule  like  a 
bursa  at  the  point  where  the  two  are  fused.  On  its  way  the  tendon  often  sends 
some  fibres  to  the  posterior  crucial  ligament. 

Movements. — The  motions  between  the  femur  and  the  patella  will  be  consid-i 
ered  after  those  between  the  thigh  and  the  leg.  The  knee  cannot  be  a  hinge-joint, 
for  in  such  the  moving  part  is  always  at  the  same  distance  from  the  axis  of  rotation, 
which  is  out  of  the  question  in  the  knee,  owing  to  the  shape  of  the  condyles.  The 
fact  that  these  are  neither  of  equal  length  nor  parallel  complicates  the  problem.  The 
joints  are  further  subdivided  by  the  semilunar  cartilages,  which  make  a  slight 
socket  for  each  condyle.  This  socket  is  more  or  less  movable  and  also  compressible 
and  elastic,  so  that  it  may  change  its  shape  to  accommodate  itself  to  the  form  of 


Fig.  423. 

Tendon  of  extensor  quadriceps 


Capsule 


Ligamentum 


External  condyle 


Ligamentum  patellar 


Tubercle  of  tibia 


om  right  knee,  which  is  strongly  flexed  to  show  alar  ligaments  and  ligamentum  mucosum.    A 
probe  is  passed  beneath  the  latter. 

different  parts  of  the  condyle.  The  external  semilunar  cartilage,  having  its  horns 
securely  attached  near  together  and  having  a  long  coronary  ligament,  can  swing 
backward  and  forward  pretty  freely  as  a  whole.  The  internal  cartilage  is  more 
closely  fastened  to  the  tibia,  excepting  the  anterior  horn,  which  has  no  constant 
arrangement.  Not  only  can  the  semilunar  cartilages  change  shape,  but,  as  Braune 
has  shown,  the  cartilage  of  the  joint  is  capable  of  compression.  For  all  these 
reasons  accurate  mathematical  statements  are  impossible. 

In  extension  of  the  leg  on  the  thigh,  beginning  with  the  knee  flexed,  the  tibia 
travels  along  the  irregular  curve  of  the  condyles,  carrying  the  semilunar  cartilages 
with  it.  There  is  practically  no  movement  between  the  internal  cartilage  and  the 
tibia,  unless  at  the  end,  and  probably  little  beneath  the  external.  The  external 
tuberosity  of  the  tibia  reaches  the  front  of  the  shorter  condyle  before  the  internal 
tuberosity  has  completed  its  course.  The  last  part  of  the  advance  of  the  latter  is 
accompanied  by  an  outward  rotation  of  the  tibia  on  a  vertical  axis  passing  through 
about  the  middle  of  the  outer  condyle,  so  that  while  the  inner  tuberosity  still  swings 


PRACTICAL   CONSIDERATIONS  :    THE    KNEE-JOINT.  409 

forward,  the  outer  part  of  the  external  swings  back.  This  motion  occurs  below  the 
external  semilunar  cartilage.  Flexion  begins  with  a  corresponding  inverse  rotation 
of  the  tibia.  While  the  knee  is  straight  the  tibia  is  firmly  fixed,  so  that  in  rotation 
of  the  limb  at  the  hip  the  bones  move  as  one.  The  long  lateral  ligament  and  that 
part  of  the  capsule  called  the  internal  ligament  are  placed  so  far  back  that  they  are 
relaxed  in  flexion  but  become  tense  in  extension.  Both  the  crucial  ligaments  are 
always  nearly  tense,  especially  the  posterior.  The  anterior  is  quite  tense  in  exten- 
sion, the  posterior  in  flexion.  The  latter  prevents  forward  displacement  of  the 
femur  on  the  tibia  when,  as  in  alighting  from  a  leap,  the  whole  weight  is  carried  for- 
ward by  the  impetus,  the  knee  being  flexed.  Another  rotation  on  a  vertical  axis 
through  the  middle  of  the  joint  may  occur  when  the  knee  is  flexed.  The  motion 
is  between  the  femur  and  the  internal  semilunar  cartilage,  and  both  above  and  below 
the  external  one.  This  motion  is  chiefly  passive, — i.e. ,  imparted  by  another  person 
twisting  the  leg  when  the  muscles  are  relaxed.  It  probably,  however,  can  be  exe- 
cuted actively  to  some  extent.  It  is  very  slight  in  less  than  semiflexion  of  the  knee, 
and  diminishes  as  flexion  becomes  more  extreme.  The  precise  angle  at  which  it  is 
greatest  seems  uncertain.  Rotation  of  the  tibia  outward,  tending  to  untwist  the 
crucial  ligaments,  is  resisted  by  neither,  but  by  the  internal  lateral  ligament.  Rota- 
tion inward  is  resisted  by  both  crucials,  especially  the  anterior,  and  by  the  external 
lateral.  The  posterior  ligament  is  made  tense  in  life  in  positions  in  which  it  would 
otherwise  be  lax  by  the  action  of  the  semimembranosus.  It  is  tense  in  extension.  The 
front  part  of  the  capsule  is  tense  in  flexion  and  relaxed  in  extension,  but  its  condi- 
tion in  the  latter  state  is  considerably  modified  by  the  degree  of  contraction  of  the 
quadriceps  extensor. 

Movements  of  the  Patella. — The  patella  in  the  upright  position,  when  the 
muscles  are  relaxed,  has  the  lower  part  of  the  articular  surface  resting  against  the 
top  of  that  of  the  femur.  When  the  muscle  is  contracted  the  former  is  drawn 
entirely  above  the  latter.  As  flexion  begins  the  lower  zone  of  the  articular  surface 
fits  into  the  groove  on  the  femur,  the  two  upper  and  the  internal  strip  not  being  in 
contact  with  it.  In  semiflexion  the  knee-pan  has  passed  below  the  patellar  surface 
of  the  femur,  and  the  middle  zone  rests  on  the  front  of  the  outer  condyle  and  on  a 
small  part  of  the  inner.  As  flexion  becomes  extreme  the  patella  follows  the  outer 
condyle,  resting  on  its  under  side  by  its  superior  zone,  the  convex  portion  is  in  the 
notch,  and  only  the  strip  along  the  inner  edge  is  in  contact  with  the  outer  side  of  the 
internal  condyle.  In  the  latter  part  of  the  movement  the  mucous  ligament  becomes 
tense,  and  through  it,  and  still  more  by  atmospheric  pressure,  the  alar  ligaments  are 
brought  close  in  to  fill  the  chink  between  the  femur  and  the  tibia. 

PRACTICAL    CONSIDERATIONS. 

The  Knee-joint. — The  anatomical  conditions  which  should  render  the  knee- 
joint  peculiarly  subject  to  dislocation  are  as  follows  :  1.  Its  situation  between  the 
longest  bones  of  the  skeleton  and  its  consequent  exposure  to  tremendous  leverage. 
2.  Its  similar  exposure  to  frequent  strain  and  traumatism.  3.  The  extensive  and 
varied  character  of  its  movements.  4.  The  absence  of  bony  prominences,  which 
could  effectively  strengthen  the  joint,  upon  either  the  articular  surface  of  the  lower 
end  of  the  femur  or  the  shallow  upper  surface  of  the  tibial  tuberosities. 

The  ability  of  the  joint  to  resist  dislocation,  which  is  of  very  rare  occurrence, 
lies  in  (a)  the  strength  of  the  ligaments,  especially  the  crucial  ;  (6)  the  expansions 
of  the  quadriceps  tendon  on  the  front  of  the  joint  ;  (c)  the  reinforcement  of  the 
posterior  ligament  by  the  semimembranosus  tendon  ;  (d)  the  similar  relation  of  the 
internal  lateral  ligament  to  the  semimembranosus,  and  of  the  external  lateral  to  the 
tendons  of  the  biceps  and  popliteus  ;  (e)  the  power  thus  conferred  upon  strong 
muscles  to  meet  and  modify  or  resist  sudden  strains  by  varying  the  tension  of  the 
capsule  and  even  of  the  ligaments  ;  (_/)  the  deepening  of  the  tibial  cup  by  the  semi- 
lunar cartilages,  and  the  adaptation  of  the  latter  to  the  varying  positions  of  the  bones 
so  that  the  contact  between  and  pressure  upon  the  joint-surfaces  are  as  extensive  and 
as  uniform  as  the  shape  of  the  condyles  will  permit. 

Dislocations  of  the  knee  may  be  antero-posterior  or  lateral  in  direction.      The 


410  HUMAN    ANATOMY. 

former  usually  and  the  latter  invariably  are  incomplete,  owing  to  the  large  superficial 
areas  of  the  joint-surfaces.  In  the  great  majority  of  cases  dislocations  of  the  knee 
are  due  to  indirect  violence  acting  through  the  femur  as  a  lever, — as,  for  example,  in 
falls  forward,  the  foot  and  leg  being  fixed.  The  weight  of  the  trunk  carrying  the 
upper  end  of  the  thigh  forward,  brings  the  lower  end  with  great  power — the  fulcrum 
and  the  resistance,  or  weight,  being  so  close  to  each  other — against  the  posterior 
ligament,  a  rupture  of  which  permits  the  movement  to  continue  and  results  in  an 
anterior  dislocation  of  the  knee,  which  is,  regarded  from  an  etiological  stand  point, 
a  displacement  of  the  femur  backward. 

If  the  fall  is  in  the  opposite  direction,  the  femur  may  be  displaced  anteriorly, — 
i.e. ,  posterior  dislocation  of  the  knee  may  occur.  Occasionally  the  anterior  disloca- 
tion has  followed  the  fall  of  a  weight  upon  the  front  of  the  femur.  The  application 
of  force  to  the  front  of  the  leg  when  the  knee  was  flexed  has  produced  a  posterior 
dislocation,  the  effect  of  the  biceps,  popliteus,  and  semimembranosus  in  reinforcing 
the  posterior  ligament  being  minimized  in  that  position. 

Lateral  dislocations  are  caused  by  adduction  or  abduction  of  the  leg,  the  thigh 
being  fixed,  or  by  falls  sideways  when  the  foot  and  leg  are  fixed.     The  great  width 

Fig.  424. 

Vastus  internus 


Tendon  of 
adductor  magnus 


Internal  condyle 


Tendon  of  sartorius 
Inner  aspect  of  right  knee-joint,  showing  expansion  of  quadriceps  tendon. 

of  the  joint  and  the  slight  resistance  offered  by  the  interposition  of  the  tibial  spine 
between  the  femoral  condyles  render  them  rarer  than  antero-posterior  luxations. 

Forward  dislocation  is  more  common,  possibly  because  of  the  greater  laxity 
of  the  capsule  in  front,  and  is  more  apt  to  be  complete  than  the  backward.  The 
knee  is  extended  ;  the  tibial  tubercle  prominent ;  the  antero-posterior  diameter 
increased  ;  the  anterior  margin  of  the  tibial  tuberosities  palpable  in  front  ;  the 
rounded  condyles  may  be  felt,  but  less  distinctly  posteriorly  ;  the  popliteal  concavity 
is  obliterated  ;  the  aponeurotic  expansion  of  the  quadriceps  is  loose  and  lies  in  folds 
about  the  upper  border  of  the  patella.  The  femoral  vessels  and  nerves  may  be 
bruised,  compressed,  or  lacerated. 

In  backward  dislocation  also  the  knee  is  in  extension  and  the  antero-posterior 
diameter  increased.  The  displaced  bony  prominences  may  be  recognized  by  palpa- 
tion. This  dislocation  is  even  less  apt  to  be  complete  than  the  forward  variety  ;  but 
if  it  is,  the  vessels  and  nerves  are  oftener  injured,  as  shown  by  the  more  frequent 
occurrence  of  gangrene.  This  is  probably  due  to  the  sharpness  and  prominence  of 
the  backward  projection  of  the  upper  edge  of  the  tibial  tuberosities,  as  compared 
with  the  rounded  depressed  notch  between  the  femoral  condyles  which  receives  the 
vessels  in  forward  dislocation. 

In   lateral  dislocation,   in  accordance  with  the  direction  of   the  displacement, 


PRACTICAL    CONSIDERATIONS  :    THE    KNEE-JOINT. 


411 


one  or  other  condyle  becomes  prominent,  as  does,  on  the  opposite  aspect  of  the 
limb,  the  head  of  the  fibula  or  the  inner  tuberosity  of  the  tibia.  The  patella,  owing 
to  the  shortness  and  strength  of  its  ligament,  is  carried  with  the  tibia.  The  lateral 
diameter  of  the  joint  is  increased.  The  foot  is  apt  to  be  rotated  in  the  direction  of 
the  luxation  owing  to  the  tension  of  the  biceps  in  the  outward  and  of  the  popliteus 
and  inner  hamstrings  in  the  inward  variety. 

Dislocations  by  rotation  have  also  occurred. 


Internal  semilunar, 
cartilage 


Crucial  ligaments 


External  semilunar 
cartilage 


Cavity  of  knee-joint 


Tibia  Fibula 

Frontal  section  through  knee-joint,  showing  articulating  surfaces  and  epiphyseal  lines. 


In  the  various  forms  of  luxation  the  crucial,  the  lateral,  and  the  posterior  liga- 
ments and  the  biceps  and  gastrocnemius  muscles  suffer  most  severely  ;  the  popliteus 
and  semimembranosus  less  so.  They  are  often  compound,  and  may  for  that  reason 
necessitate  amputation.  The  injury  to  the  ligaments  leaves  the  joint  weak  and 
insecure  for  a  long  time. 

Subluxation  of  the  semilunar  cartilages  occurs  usually  when  the  leg  is  fixed, 
the  knee  slightly  flexed,  and  the  femur  rotated  upon  the  tibia,  because  the  move- 
ments of  flexion  and  extension  take  place  between  the  femur  and  these  cartilages, 
which,  therefore,  follow  the  motion  of  the  tibia  ;  whereas  in  rotation — the  move- 


412  HUMAN   ANATOMY. 

ments  then  occurring  between  the  tibia  and  the  cartilages — one  of  them  is  fixed 
between  the  corresponding  condyle  and  the  tibia  which  rotates  beneath  it  :  the 
remaining  cartilage,  especially  if  the  rotation  is  marked,  may  be  dragged  or  squeezed 
so  that  it  is  nipped  between  the  tibia  and  femur.  Thus  the  contraction  of  the  biceps 
which  effects  outward  rotation  of  the  leg  brings  more  closely  together  the  external 
tuberosity  of  the  tibia  and  the  external  condyle,  and  the  outer  cartilage  is  held  firmly 
between  them.  This  increases  slightly  the  distance  between  the  internal  condyle  and 
the  head  of  the  tibia,  leaving  the  internal  cartilage  freer  to  move  into  an  abnormal 
position.  When  the  popliteus,  semitendinosus,  and  semimembranosus  contract  to 
rotate  the  leg  inward,  they,  in  like  manner,  fix  the  internal  cartilage  and  allow  of 
increased  mobility  of  the  external  cartilage. 

Subluxation  of  the  inner  cartilage  is  the  more  frequent  because  ( I )  outward 
rotation  of  the  leg  is  far  more  common  than  inward  rotation  ;  (2)  the  muscle  chiefly 
concerned  in  effecting  inward  rotation, — the  popliteus, — when  it  contracts,  steadies 
and  supports  the  external  cartilage  by  pressure  against  its  outer  margin  (Morris)  ; 
no  corresponding  support  is  given  the  internal  cartilage  during  outward  rotation  ; 
(3)  the  anterior  crucial  ligament  is  attached  somewhat  in  front  of,  and  often  directly 
to  the  inner  cornu  of  the  external  cartilage,  tending  to  limit  its  forward  motion.  It 
is  altogether  behind  the  internal  cartilage  ;  (4)  the  external  cartilage  has  a  strong 
attachment  to  the  femur  through  the  ligament  of  Wrisberg  posteriorly. 

The  displacement  is  forward  in  the  majority  of  cases.  The  symptoms  are  pain, 
from  the  pressure  on  the  cartilage  itself,  increased  by  reflex  spasm  of  the  muscles 
moving  the  joint,  and  followed  by  a  synovitis.  The  edge  of  the  cartilage  may  often 
be  felt. 

Disease  of  the  knee-joint  is  of  great  frequency  on  account  of  its  exposure  to  (a) 
direct  violence  and  to  cold  and  wet,  by  reason  of  its  superficial  position,  and  (b)  to 
strains  and  wrenches  through  the  leverage  of  the  femur  and  tibia.  The  factors 
competent  to  resist  luxation  are  not  able  to  protect  it  from  minor  injuries.  It  is  a 
favorite  seat,  therefore,  of  traumatic  synovitis,  and — on  account  also  of  its  complexity, 
its  large  size,  and  the  difficulty  in  keeping  it  at  absolute  rest — disease,  if  acute,  is 
apt  to  be  severe  and  threatening  ;  if  subacute,  tends  to  become  chronic  or  to  recur. 
All  the  above  reasons,  combined  with  its  inclusion  of  the  lower  femoral  epiphysis 
and  its  close  relation  to  the  upper  tibial  epiphysis, — the  seats  of  the  chief  growth  of 
the  lower  limb, — make  it  also  one  of  the  joints  most  commonly  subject  to  tuberculous 
disease,  while  gout,  rheumatism,  and  syphilitic  and  gonococcic  infection  are  often 
localized  in  it. 

Most  of  the  chronic  diseases  due  to  infection,  as  well  as  those  directly  following 
traumatism,  begin  in  the  synovial  membrane  because  of  the  large  superficial  expanse 
of  that  membrane.  The  intra-articular  effusion — whether  "simple,"  from  hyper- 
aemia,  or  inflammatory,  from  infection — causes  the  knee  to  assume  the  position  of 
moderate  flexion  because  ( 1 )  its  capacity  is  then  greater  than  in  full  extension  or 
full  flexion,  and  maximum  capacity  is  equivalent  to  minimum  pressure  ;  (2)  flexion 
relaxes  the  densest  and  most  resistant  ligaments, — the  posterior  and  the  lateral  (as 
they  are  attached  behind  the  centre  of  the  bone)  and  (if  moderate)  the  posterior 
crucial.  It  is  resisted  only  by  the  ligamentum  patellee,  which  is  in  less  close  rela- 
tion to  the  joint  (being  separated  by  the  pad  of  fat  on  which  it  lies),  and  by  the 
thinner  and  more  extensible  anterior  portion  of  the  capsule  ;  (3)  the  joint  is  inner- 
vated in  accordance  with  the  general  law  that  the  same  nerves  which  supply  the 
interior  of  an  articulation  supply  also  both  the  muscles  moving  it  and  the  skin  over 
the  insertion  of  those  muscles  (Hilton).  The  knee-joint  is  acted  on  by  ten  muscles, 
four  of  which  are  extensors  and  six  flexors.  The  latter  are  not  only  numerically  in 
excess,  but  are  also  the  more  powerful  and  the  more  favorably  situated  for  acting 
upon  the  joint.  Therefore,  when  the  articular  twigs  of  the  obturator,  sciatic,  and 
anterior  crural  nerves  are  irritated  by  disease,  and  both  the  anterior  and  posterior 
groups  of  muscles  contract  reflexly,  the  flexors  predominate.  The  principle  is  of 
wide-spread  application,  and  should  be  considered  in  reference  to  the  position  of 
most  joints,  at  least  in  the  early  stages  of  disease. 

Later  in  knee-joint  disease  the  softening  and  elongation  of  the  ligaments  permit 
the  pull  of  the  flexors  to  produce  posterior  displacement  of  the  bones  of  the  leg 


PRACTICAL   CONSIDERATIONS  :    THE    KNEE-JOINT.  413 

upon    the   thigh.       This   is   aided  in   dorsal  decubitus  by  gravitation,    which  also 
favors  the  outward  rotation  of  the  leg  that  commonly  occurs  at  the  same  time. 

The  swelling  of  synovitis,  whether  acute  or  chronic,  is  limited,  until  the  capsule 
gives  way,  by  the  attachments  of  the  synovial  membrane, — that  is,  it  extends  upward 
beneath  the  rectus  for  from  two  to  three  finger-breadths  or  from  four  to  five  centi- 
metres (one  and  a  half  to  two  inches)  above  the  summit  of  the  patella  ;  laterally,  it 
reaches  the  same  level  under  the  vastus  internus,  but  is  not  quite  so  high  on  the 
other  side,  under  the  vastus  externus.  Downward,  it  descends  to  nearly  the  middle 
of  the  ligamentum  patellae,  attaining  the  same  level  on  the  inner  side,  but  stopping 


Fro.  426. 


r—  Tendon  of  extensor  quadriceps 
— Suprapatellar  bursa 


—  Cavity  of  joint 


External  condyl 


Right  knee-joint.    The  joint-cavity  and 


-Prepatellar  bursa 


External  lateral  ligament — 
Tendon  of  popliteus 


Head  of  fibula- 


External  semilui 
cartilage 

Ligamentum  patella 
Subpatellar  bursa 


Tubercle  of  tibia 


(Spaltclwlz.) 


ided  with  injection  mass  before  dissecti< 


just  above  the  head  of  the  fibula  on  the  outer  side.  The  patella  is  separated  from 
the  trochlea  of  the  femur — "  floated  up."  In  testing  for  this  symptom,  it  is  impor- 
tant to  grasp  the  anterior  muscles  of  the  thigh  firmly  and  draw  them  towards  the 
knee  so  as  to  relax  the  pull  of  the  quadriceps,  which  is  occasionally  great  enough  to 
hold  the  patella  in  contact  with  the  femur,  even  in  the  presence  of  considerable 
effusion  (Fig.  426). 

The  condition  is  usually  unmistakable, -but  may  have  to  be  differentiated  from 
periarticular  abscess  or  haematoma.  In  the  latter  cases  the  swelling  will  not  be 
uniform  ;  the  inner  depression  at  the  side  of  the  patella  may  be  obliterated,  and  not 


414 


HUMAN    ANATOMY. 


Fig.  427. 


the  outer,  or  vice  versa ;  fluctuation  cannot  be  obtained  in  every  direction, — i.e., 
from  side  to  side  under  the  patella  or  obliquely  ;  the  patella  will  lie  directly  upon 
the  femur. 

The  diagnosis  from  bursal  enlargements  will  be  considered  in  relation  to  those 
structures. 

Syphilitic  disease  of  the  gummatous  type  is  apt  to  begin  in  the  subcutaneous 
tissue  without  the  joint,  which  it  involves  secondarily.  In  its  earlier  stages  the 
swelling  would  therefore  be  periarticular,  and  recognizable  by  the  foregoing  symp- 
toms. Later,  as  it  extends  in  both  directions,  there  will  usually  be  ulceration  of 
the  skin. 

The  knee  is  more  often  the  seat  of  the  so-called  loose  bodies  than  is  any  other 
joint.      They  are  sometimes  the  result  of  osteo-arthritis  (which  affects  the  knee  by 

preference) ,  causing  thickening  and  fibrinous 
or  calcareous  change  in  some  of  the  syno- 
vial fringes  ;  or  they  may  be  produced  in 
those  fringes  from  embryonic  remnants,  and 
are  then  composed  of  hyaline  cartilage  or 
fibro-cartilage  ;  or  they  may  result  from  the 
organization  of  inflammatory  lymph  after  an 
acute  arthritis  ;  or  they  may  be  portions  of 
an  interarticular  or  articular  cartilage  de- 
tached by  violence,  although  this  is  rare. 

In  a  case  of  suppurative  arthritis  the 
incisions  for  drainage  should  be  made  on 
either  side  of  the  patella  and  a  little  below 
its  middle,  and  should  be  placed  towards 
the  posterior  aspect  of  the  lateral  pouches 
of  the  synovial  membrane. 

Genu  valgum  —  ' '  knock-knee' '  —  in 
young  children  may  be  directly  due  to 
rickets,  or  may  follow  Charcot's  disease,  in- 
fantile paralysis,  or  any  sprain  or  dislocation 
of  the  knee  that  leaves  the  internal  lateral 
ligament  weak  or  defective.  In  children 
and  adolescents  without  these  antecedents 
its  essential  cause  is  still  a  matter  of  dispute. 
There  can  be  no  doubt,  however,  that  in 
the  great  majority  of  cases  the  production 
of  the  deformity  is  favored  by  static  modi- 
fications of  certain  anatomical  conditions 
which  are  probably  the  cause  and  not  the 
result  of  the  diaphyseal  overgrowth  of 
femur  and  tibia  (Mikulicz),  of  the  contrac- 
tion of  the  biceps  and  tensor  vaginae  femoris 
(Duchenne),  of  the  elongation  of  the  in- 
ternal lateral  ligament  (Stromeyer),  and  of 
the  atrophy  of  the  external  condyle  (Oilier) 
which  are  found  in  most  cases  of  this  de- 
formity, and  each  of  which  has  been  given  etiological  importance. 

The  angle  between  the  femoral  and  tibial  axes  (corresponding  to  that  between 
the  arm  and  forearm)  opens  outward  at  the  knee.  It  results  not,  as  in  the  upper 
extremity,  from  an  outward  obliquity  of  the  lower  segment  of  the  limb,  but  from  the 
inward  slant  of  the  thighs  from  the  pelvis  to  the  knees,  the  tibiae  (like  the  humerus) 
being  parallel  to  the  longitudinal  axis  of  the  body  and  to  each  other.  That  the  line 
of  the  knee-joint  may  be  horizontal,  the  internal  condyle  of  the  femur  is  longer  than 
the  external.  In  a  normal  person  standing  erect  in  the  military  attitude  of  "atten- 
tion" the  weight  of  the  trunk  is  transmitted  downward  from  the  head  of  the  femur 
in  a  vertical  line  which  passes  through  the  external  condyle  (Fig.  427).  The  erect 
position  must  therefore  be  maintained,  not  merely  through  the  approximation  of  the 


Line  of  pressure  between  hip  and  knee. 


PRACTICAL    CONSIDERATIONS  :    THE    KNEE-JOINT. 


415 


bones,  as  would  be  the  case  if  the  axis  of  the  whole  lower  limb  were  a  perpendicular 
running  through  the  acetabulum  and  the  centre  of  the  ankle-joint,  but  by  the  help 
of  muscular  and  ligamentous  structures. 

The  tendency  (which  is  so  common  a  factor  in  the  production  of  deformities) 
to  assume  an  attitude  which  will  transfer  strain  from  a  tired  muscle  to  the  neighboring 
ligaments  operates  here  to  cause  stretching  and  elongation  of  the  internal  lateral 
ligament,  as  the  "attitude  of  rest"  with  the  feet  separated  and  everted  is  the  one 
usually  adopted.  The  evil  effects  are,  of  course,  favored  by  much  standing,  and  are 
most  marked  in  young  persons  of  feeble  physique  whose  weight  has  increased  dis- 
proportionately to  their  muscular  strength.  The  outer  side  of  the  knee  shows  the 
changes  due  to  increased  pressure  and  to  long-continued  approximation  of  musculo- 
tendinous points  of  origin  and  insertion, — i.e. ,  atrophy  of  the  outer  condyle  and 
outer  tuberosity  ;  contraction  and  shortening  of  the  ilio-tibial  band  of  fascia,  of  the 
external  lateral  ligament,  of  the  tendon  of  the  biceps,  and  of  the  tensor  vaginae 
femoris.  The  inner  side  shows  the  effects  of  removal  of  normal  pressure  from  grow- 
ing bones  and  of  chronic  strain  of  fibrous  and  periosteal  tissue,  —  i.e. ,  overgrowth  of 
the  femoral  diaphysis  just  above  the  inner  end  of  the  epiphyseal  line  and  of  the  tibial 
diaphysis  just  below  the  corresponding  level  ;  lengthening  of  the  internal  lateral 
ligament  ;  bony  outgrowth  at  its  tibial  insertion  from  chronic  periostitis. 

The  tibia  is  apt  to  be  rotated  outward,  possibly  through  the  action  of  the  short- 
ened biceps.  Talipes  valgus  (q.  v. )  may  be  either  a  cause  or  a  result  of  genu  valgum. 
The  disappearance  of  the  deformity  when  the  knees  are  flexed 
is  probably  due  to  the  outward  rotation  of  the  femur  that  ac- 
companies flexion,  and  not,  as  is  generally  stated,  to  the  fact 
that  the  antero-posterior  diameter  of  the  condyles  is  unaffected 
by  the  disease. 

The  clinical  symptoms  and  results  and  the  treatment  by 
apparatus  cannot  be  described  here. 

In  Maceweri  s  osteotomy  the  femur  is  divided  from  the  inner 
side  of  the  thigh  at  a  point  twelve  millimetres  (half  an  inch) 
above  the  adductor  tubercle  and  in  a  line  at  right  angles  to 
the  long  axis  of  the  femur.  Osteotomy  may  also  be  done  from 
the  outside  of  the  thigh  and  at  the  same  level.  These  opera- 
tions are  usually  safe,  but  the  popliteal  artery,  the  anastomotica 
magna,  the  external  peroneal  nerve,  and  other  important  struc- 
tures have  been  accidentally  divided. 

Genu  varum — "  bow-leg" — is  almost  always  rhachitic  in  its 
origin.  '  A  child  with  rickets  and  having  lumbar  lordosis  of  the 
spine  stands  with  its  thighs  slightly  flexed,  either  as  a  secondary 
result  of  the  shortening  of  the  ilio-femoral  ligaments  produced 
by  backward  rotation  of  the  pelvis  (to  compensate  for  the  for- 
ward rotation  of  the  sacrum)  or  more  simply  as  an  easy  method 
of  relaxing  the  weak  ilio-psoas  muscles  and  preserving  the 
centre  of  gravity.  As  the  thighs  flex  the  knees  separate,  the 
femurs  rotate  outward  on  their  own  axes,  the  line  of  gravity 
falls  to  the  inside  of  the  centre  of  the  knee-joint  (Fig.  428),  the 
pressure  is  greatest  on  the  inner  condyle  and  tuberosity,  the  strain  comes  upon  the 
external  lateral  ligament,  and  the  outward  bowing  begins  and  is  continued  by  the 
leverage  of  the  body  weight. 

Genu  recurvatum — "back-knee" — is  a  deformity  in  which,  as  a  result  of  intra- 
uterine malposition,  or  of  congenital  paralysis  of  the  flexors  and  popliteus,  or  of 
pressure  brought  upon  the  posterior  and  crucial  ligaments  in  walking  in  a  case  of 
partial  paralysis  of  the  quadriceps,— the  limb  being  swung  forward,  the  heel  coming 
to  the  ground  in  full  extension,  and  the  weight  of  the  body  reaching  the  joint  in 
front  of  its  centre  of  gravity, — the  knee  is  bent  backward  and  the  whole  limb  presents 
a  long  curve  with  its  concavity  forward. 

In  excision  of  the  knee  the  lines  of  the  epiphysis  should  be  remembered  if  the 
patient  is  under  twenty  or  twenty-one  years  of  age  (page  365),  the  relation  of  the 
femoral  vessels  to  the  posterior  ligament,  the  situation  and  extent  of  the  synovial 


Showing  the  form  of  the 
bones  in  bow-legs. 


416 


HUMAN   ANATOMY. 


pouches  (which  in  infectious  cases  are  usually  involved),  the  direction  of  the  articular 
line  (with  which  the  saw  cut  should  be  parallel),  and  sometimes  the  possibility  of 
infection  of  the  neighboring  bursse. 

Landmarks. — The  synovial  membrane  rises  from  four  to  five  centimetres 
(one  and  a  half  to  two  inches)  above  the  upper  border  of  the  patella  ;  it  is  higher 
on  the  inner  than  on  the  outer  side  of  the  thigh  ;  its  upper  limit  descends  in  flexion 
of  the  knee. 

The  bony  points  have  been  described  in  connection  with  the  femur  and  tibia 
(pages  367,  390)  ;  the  bursse  will  be  described  later. 

The  Patella. — Congenital  absence  of  the  patella  on  one  or  both  sides  has  been 
noted  in  a  number  of  instances,  and  has  in  some  cases  been  observed  in  several 
members  of  the  same  family.  The  functional  disability  was  slight  or  altogether 
unnoticeable. 

Fracture  by  muscular  action  is  more  common  in  this  bone  than  in  any  bone  of 
the  skeleton.  It  occurs  usually  with  the  leg  in  partial  flexion  upon  the  knee.  In 
this  position  fracture  is  favored  because  (1)  the  ligamentum  patellae  is  then  taut 
and  fixes  the  lower  edge  of  the  bone  ;  (2)  the  patella  is  in  contact  only  through  the 
upper  third  of  its  convex  under  surface  with  the  most  prominent  part  of  the  articu- 
lar surface  of  the  condyles  (Fig.  429) ;  and  (3)  at  this  time  the  quadriceps  extensor 


Fig.  429. 


Rectus  muscle 


Subpatellar  tissue 
Tendo  patella? 


Showing  position  of  patella  in  relation  to  condyles  of  femur  with  knee  partially  flexed 


has  the  greatest  advantage  of  leverage  upon  the  patella,  as  when  the  knee  is  fully 
bent  the  muscle  gets  its  leverage  for  the  beginning  of  extension  through  the  projec- 
tion of  the  front  of  the  condyles,  and  the  patella  lies  on  the  pad  of  fat  between  the 
femur  and  tibia  (Fig.  430),  and  when  the  knee  is  almost  or  quite  extended,  the 
patella — or  three-fourths  of  it — occupies  the  depression  of  the  trochlea,  or  even  that 
just  above  it.  As  a  result  of  the  cross-strain  brought  to  bear  in  the  partially  flexed 
position  the  bone  usually  breaks  transversely  a  little  below  its  mid-line, — i.e.,  through 
the  area  unsupported  by  the  femur  beneath  (Fig.  429).  Occasionally  it  gives  way 
at  a  higher  level. 

The  accident  may  happen  as  the  result  of  a  fall,  but  the  fall  is  more  apt  to 
follow  than  to  precede  the  fracture.  In  ordinary  falls  upon  the  knee  the  force  is 
received  upon  the  tubercle  of  the  tibia,  not  upon  the  patella. 

Direct  violence  often  causes  an  irregular,  comminuted,  or  stellate  fracture. 

Fracture  never  occurs  in  children  and  is  extremely  rare  before  adult  life. 
When  the  bone  is  broken  the  fragments  are  immediately  separated  by  the  action 
of  the  quadriceps  upon  the  upper  one.  The  degree  of  their  separation  will  de- 
pend upon  the  amount  of  laceration  of  the  lateral  aponeurotic  expansions  of  the 
conjoined  tendon.  Unless  that  fibrous  structure  is  torn,  no  great  separation  of 
the  fragments  can  occur,  as  it  is  inserted  into  the  borders  and  front  of  the  patella, 


PRACTICAL    CONSIDERATIONS  :    THE    PATELLA. 


4i7 


which  is  thus  embedded,  as  it  were,  in  a  hood  spread  out  over  the  front  of  the  joint 
and  extending  to  the  lateral  ligaments  and  to  the  oblique  lines  running  up  from  the 
tubercle  to  the  tuberosities  (Fig.  424).  The  force  causing  the  fracture  in  cases  of 
direct  violence,  or  atmospheric  pressure  on  the  front  of  the  knee  if  the  fracture  was 
from  muscular  action,  drives  in  between  the  fragments,  as  they  separate,  in  the 
shape  of  shreds  or  of  an  irregular  fringe,  portions  of  that  part  of  the  rectus  tendon 
which  was  inserted  into  the  longitudinal  grooves  or  striae  on  the  anterior  surface  of 
the  bone.  These  offer  an  obstacle  to  bony  union.  As  the  synovial  membrane  of 
the  knee-joint  lies  in  contact  with,  and  is  attached  to,  the  under  surface  of  the 
patella,  it  will  usually  be  lacerated, — i.e. ,  the  knee-joint  will  be  opened  and  the 
fragments  surrounded  by  bloody  synovial  fluid.  The  synovial  membrane  is  re- 
flected from  the  patella  some  distance  above  the  apex  of  the  bone  ;  hence  a  fracture 
may  occur  at  that  level  without  involvement  of  the  joint.      The  pad  of  fat  on  which 


Fig.  430. 


Subpatellar  tissue 


the  tip  of  the  bone  rests,  and  over  which  the  membrane  is  reflected,  may  aid  in 
saving  the  joint  from  injury. 

The  common  failure  to  get  bony  union  by  non-operative  methods  is  thus  seen 
to  be  due  to  (1)  separation  of  the  fragments  by  the  quadriceps,  (2)  the  interposition 
of  portions  of  the  capsule,  (3)  the  presence  of  blood-clot  and  synovial  fluid,  and  is 
supposed  to  be  further  favored  by  (4)  the  sesamoid  character  of  the  bone  inclining 
it  to  unite  by  fibrous  rather  than  by  bony  tissue.  It  has  been  asserted,  however 
(Wirth),  that  the  patella  is  a  detached  portion  of  the  upper  tibial  epiphysis  and  not 
a  true  sesamoid  bone. 

As  non-union  is  common  on  account  of  the  above  anatomical  conditions,  oper- 
ative measures  are  often  resorted  to.  In  the  open  operations  used  in  old  united 
fractures  the  fragments  are  drilled  obliquely  from  a  half-inch  above  and  below  the 
line  of  fracture  to  just  above  the  cartilaginous  under  surface,  so  that  the  wire  used 
to  hold  them  together  does  not  lie  in  the  joint. 

27 


4i8  HUMAN    ANATOMY. 

To  approximate  the  fragments  elevation  of  the  limb  sometimes  suffices,  but 
occasionally  partial  section  of  the  lateral  expansions  of  the  quadriceps,  of  the  rectus 
tendon,  and  of  the  muscle  itself  will  be  required  as  successive  steps. 

In  the  best  of  the  operations  used  in  recent  fractures,  and  which  do  not  widely 
open  the  joint,  a  silk  or  silver  ligature  is  carried  through  an  incision  at  the  lower 
border  of  the  patella  behind  that  bone  and  between  it  and  the  trochlear  groove 
in  the  femur,  is  brought  out  through  an  incision  at  the  upper  border,  rethreaded 
on  a  needle  with  an  eye  near  the  point,  brought  down  in  front  of  the  patella, — 
beneath  the  skin, — and  tied  or  twisted  so  as  to  hold  the  fragments  together.  The 
blood-clot  and  synovial  exudate  are  squeezed  out  through  the  two  incisions  ;  the 
entangled  capsular  fibres  are  removed  by  attrition  of  the  fractured  surfaces  against 
each  other.  These  operations  are,  of  course,  not  applicable  to  old  fractures  in 
which  shortening  of  the  muscle  has  taken  place  and  approximation  and  forcible  rub- 
bing together  of  the  fragments  are  impossible. 

Operations  for  recent  fracture  by  open  arthrotomy  permit  the  direct  removal  of 
the  fringe  of  interposed  tendinous  and  capsular  fibres  and  the  repair  by  suture 
of  the  rents  in  the  capsule  and  in  the  lateral  expansions  of  the  quadriceps.  The 
patellar  fragments  may  also  be  sutured,  but  this  is  not  always  necessary. 

Dislocaticni  of  the  patella  usually  occurs  from  muscular  action  and  as  a  conse- 
quence of  sudden  contraction  of  the  quadriceps. 

The  displacement  is  commonly  in  the  outward  direction  because  the  long  axis 
of.  the  quadriceps  muscle  and  tendon  is  inclined  to  that  of  the  ligamentum  patellae 
in  such  a  way  that  the  bone  is  situated  at  the  apex  of  an  obtuse  angle  which  opens 
outward.  When  the  quadriceps  contracts  the  tendency  is  to  straighten  this  angle, 
— i.e. ,  to  carry  the  patella  outward, — and  this,  aided  by  the  greater  strength  of 
the  vastus  externus  as  compared  with  that  of  the  inner  vastus,  is  more  than  suf- 
ficient to  overcome  the  resistance  offered  by  the  greater  prominence  of  the  external 
condyle,  as  well  as  the  relatively  more  extensive  insertion  of  the  vastus  internus  into 
the  inner  margin  of  the  patella.  The  bone  may  even,  as  in  one  recorded  case, 
be  carried  entirely  past  the  condyle,  so  as  to  lie  behind  the  centre  of  motion  of  the 
knee  when  the  joint  is  bent,  thus  causing  the  quadriceps  extensor  to  act  as  a  flexor 
of  the  leg  on  the  thigh. 

The  external  articular  facet  on  the  under  surface  of  the  patella  is  larger  than  the 
internal.  The  patella  is  in  relation,  therefore,  chiefly  with  the  external  condyle,  and 
even  if  dislocation  occurs  from  direct  violence,  it  is  more  likely  to  be  driven  in  that 
direction  (Humphry).  If  it  has  once  passed  beyond  the  edge  of  the  outer  condyle 
— a  ' '  complete' '  luxation  necessarily  attended  by  laceration  of  the  capsule — it  is 
less  likely  to  be  replaced  than  if  it  had  gone  in  the  opposite  direction,  because  of  (a) 
the  resistance  offered  by  the  prominence  of  the  condyle  itself  and  (b~)  the  greater 
comparative  strength  of  the  vastus  externus. 

Outward  luxation  is  not  very  rare  in  cases  of  genu  valgum,  and,  per  contra,  in 
congenital  cases  of  patella  luxation  and  in  unreduced  traumatic  luxations  genu 
valgum  has  followed  (Makins). 

The  patella  may  be  displaced  inward  by  direct  force.  It  is  sometimes  turned 
on  edge  by  a  force  insufficient  to  dislocate  it  completely,  and  is  held  in  that  position 
by  the  tension  of  the  soft  parts  attached  to  it  and  by  the  pressure  of  the  over- 
lying fascia,  "like  a  stick  on  end  under  a  tightly  stretched  sheet"  (Stimson).  In 
flexion  of  the  knee  the  patella  lies  deeply  in  the  depression  between  the  condyles 
and  the  quadriceps  tendon  is  on  the  stretch.  The  bone  is  therefore  somewhat 
removed  from  danger  of  direct  violence,  and  is  steadied  and  fixed  by  the  quadri- 
ceps muscle.  In  extension  the  patella  rests  on  the  trochlear  surface  of  the  femur 
only  by  its  lower  margin  ;  it  is  more  prominent  and  thus  more  exposed  to  force 
directly  applied  ;  the  quadriceps  is  relaxed,  leaving  the  bone  freely  movable. 
For  these  reasons  extension  is  the  position  in  which  dislocation  most  commonly 
occurs. 


THE    TARSAL    BONES.  419 


THE   FOOT. 

The  framework  of  the  foot  consists  of  the  tarsits,  metatarsus,  and  phalanges, 
which  differ  in  their  proportionate  size  from  the  corresponding  divisions  of  the  hand. 
Thus,  in  the  latter  the  carpal  region  is  the  shortest  and  that  of  the  phalanges  the 
longest,  equalling  almost  precisely  the  other  two  ;  in  the  foot,  on  the  contrary,  the 
region  of  the  phalanges  is  the  shortest  and  that  of  the  tarsus  makes  about  half  the 
entire  length.  The  tarsus  differs  also  in  its  arrangement  more  than  the  carpus  from 
the  primitive  type.  The  tarsal  bones  may  be  considered  as  divided  into  two  lateral 
divisions  :  an  outer  series  of  two  bones  bearing  the  two  outer  toes,  and  an  inner 
series  of  five  bearing  the  three  inner  toes,  so  placed  that  the  proximal  bone  of  the 
inner  part  rests  on  top  of  the  proximal  of  the  outer.  The  outer  side  of  the  skeleton 
of  the  foot  rises  but  little  from  the  ground,  while  the  inner  is  highly  arched. 

THE   TARSAL    BONES. 
The  tarsal  bones  are  the  calcaneum,  or  os  calcis,  the  heel-bone  ;  the  cuboid,  which 
with  it  forms  the  outer  division  ;  the  astragalus,  or  talus,  which  joins  the  leg  ;  the 
scaphoid,  placed  between  the  astragalus  and  the  three  cuneiform,  which  bear  the 
three  inner  metatarsals. 

THE  CALCANEUM. 
The  calcaneum '  is  a  narrow  elongated  bone  forming  the  heel,  supporting  the 
astragalus,  and  joining  the  cuboid  in  front.  It  has  six  surfaces.  The  inferior  sur- 
face presents  at  the  back  a  swelling  subdivided  into  the  internal  and  external pla?i- 
iar  tubercles,  of  which  the  former  is  much  the  larger,  forming  the  posterior  pier  of 
the  foot.  These  tubercles  are  continuous  at  the  posterior  border,  in  front  of  which 
a  deep  notch  divides  them.  Each  appears  on  its  side  of  the  bone.  In  front  of 
these  the  lower  surface,  convex  from  side  to  side,  is  marked  by  longitudinal  grooves. 
Near  the  front  is  the  anterior  tubercle,  a  small  swelling,  from  which  and  from  a 
depression  near  it  arise  calcaneo-cuboid  ligaments.  The  posterior  surface  is 
roughly  oval  with  the  small  end  up.  The  tendo  Achillis  is  attached  to  a  roughness 
occupying  its  lower  half,  above  which  the  bone  slants  forward  and  is  smooth  for  a 
bursa  between  it  and  the  tendon.  The  lower  part  of  the  posterior  surface  is  con- 
tinuous with  the  plantar  tubercles.  The  internal  surface  is  smooth  and  concave  ; 
for  the  internal  tubercle  projects  strongly  inward,  while  in  front  and  above  there  is 
a  shelf-like  process,  the  sustentaculum  tali,  to  support  the  head  of  the  astragalus, 
slanting  downward  and  forward.  Beneath  this  is  a  slight  groove  for  the  tendon  of 
the  long  flexor  of  the  great  toe.  Lower  down  near  the  front  border  a  depression 
for  a  ligament  to  the  cuboid  runs  down  in  front  of  the  anterior  tubercle.  The  ex- 
ternal surface  is  the  longest.  It  presents  about  its  middle  a  vague  tubercle  for 
the  middle  bundle  of  the  outer  lateral  ligament  of  the  ankle,  and  nearer  the  front 
a  larger  one,  the  peroneal  spine.  When  well  marked  this  is  a  ridge,  covered  with 
cartilage,  slanting  downward  and  forward,  separating  two  grooves  for  the  tendons  of 
the  peroneus  longus  and  brevis.  The  outer  posterior  plantar  tubercle  projects 
somewhat  on  this  side.  Rather  more  than  the  anterior  two-thirds  of  the  superior 
surface  are  devoted  chiefly  to  the  joints  with  the  astragalus  ;  the  posterior  portion 
is  convex  from  side  to  side  and  concave  from  before  backward.  There  are  two 
articular  facets  :  the  posterior  facet,  the  larger,  a  vaguely  four-sided  swelling,  occu- 
pies the  middle  of  this  surface.  Its  long  axis  runs  forward,  downward,  and  out- 
ward. It  is  convex  in  this  direction.  The  upper  inner  end  is  the  broader,  and 
near  it  the  facet  is  very  often  concave  at  right  angles  to  the  long  axis,  but  in  the 
main  it  is  about  plane  in  that  direction  and  may  be  even  slightly  convex.  The  anterior 
facet,  long  and  narrow,  concave  from  before  backward,  runs  forward  and  outward, 
nearly  parallel  to  the  long  axis  of  the  former.  It  begins  internally  on  the  top  of  the 
sustentaculum  and  ends  at  the  most  anterior  point  of  the  bone.  In  about  half  the 
cases  this  surface  is  subdivided  into  two,  and,  as  a  rule,  when  it  is  not  there  is  a 


420 


HUMAN    ANATOMY. 
A  Fl«-  43i- 


Bones  of  right  foot,  dorsal  aspect.    A,  outer  series  ;  £,  inner  series. 


THE    CALCANEUM. 


421 


notch  in  the  free  border  just  at  the  end  of  the  sustentaculum.  Occasionally  the 
facet  in  front  of  the  interruption  is  rudimentary  or  wanting,  in  which  case,  instead 
of  articular  cartilage,  merely  synovial  membrane  is  beneath  the  head  of  the  astraga- 
lus. In  200  feet  we  have  found  the  facet  single  in  95,  divided  in  94,  and  in  1 1  the 
front  was  wanting.  The  two  chief  facets  (counting  the  anterior  as  one,  even  if  sub- 
divided) are  separated  by  a  deep  groove  for  the  interosseous  ligament  to  the  astrag- 
alus. This  gutter  broadens  in  front  into  a  rough  depression,  the  sinus  tarsi,  for 
ligaments.  At  its  outer  part  there  is  a  tubercle  for  the  origin  of  the  extensor  brevis 
digitorum.  The  anterior  surface,  turned  somewhat  inward,  is  wholly  articular 
for  the  cuboid.  It  is  three-sided  with  rounded  angles.  The  longest  diameter  is 
from  above  downward  and  outward,  nearly  parallel  with  the  inner  border.  The 
upper  border  is  straight  or  convex,  overhanging  the  joint  at  the  inner  side.  The 
outer  border  slants  a  little  inward  as  it  descends.  The  surface  is  concave  from 
above  downward  and  convex  transversely.      Both   these  curves  are  most  marked  at 


Astragalus 


Sustentaculum  tal 


Interosseous  groove 


Internal  tubercl 


Peroneal  spine 


Astragalu 


the  upper  inner  angle,  where  they  form  almost  a  groove  for  the  plantar  process  of 
the  cuboid.  The  general  effect  is  of  a  screw  surface  twisting  upward  and  inward. 
The  calcaneum  articulates  with  two  bones,  the  cuboid  and  the  astragalus,  and  excep- 
tionally with  the  scaphoid,  to  which  it  may  be  united  by  cartilage. 

Variations. — The  hind  end  of  the  sustentaculum  is  very  rarely  a  separate 
piece  :  os  sustentaculi  proprium.  The  inner  edge  of  the  front  of  the  bone,  which 
normally  comes  very  near  to  the  scaphoid,  may  meet  it.  Sometimes  the  two  bones 
are  fused.  The  calcaneum  secundarium  is  a  small  ossicle  rarely  present  on  the 
dorsum  between  the  calcaneum,  the  cuboid,  the  scaphoid,  and  the  head  of  the 
astragalus.  Fusion  of  the  calcaneum  and  astragalus  has  been  observed  at  the  sus- 
tentaculum. 

Structure. — The  walls  are  thin,  the  cancellated  tissue  filling  the  bone,  with  a 
tendency  to  the  formation  of  large  spaces  at  the  middle.  The  architectural  arrange- 
ment is  very  clear  in  an  antero-posterior  section,  which  shows  diverging  plates  from 


422 


HUMAN    ANATOMY. 


the  greater  articular  facet  for  the  astragalus  and  a  system  of  loops  connecting  them. 
The  large  spaces  are  at  the  neutral  point. 


Longitudinal  sect 


Development. — The  chief  nucleus  is  said  to  appear  in  the  sixth  month  ol 
foetal  life.  We  have  twice  seen  it  earlier, — once  at  about  the  fourth  month.  An 
epiphysis  for  the  back  of  the  bone  and  the  posterior  plantar  tubercles  appears  from 
the  seventh  to  the  tenth  year.  It  begins  to  fuse  by  fifteen,  completing  the  process 
in  a  year  or  so. 

THE  CUBOID. 
The  cuboid '  is  a  six-sided  bone,  flattened  from  above  downward,  interposed 
between  the  calcaneum  and  the  fourth  and  fifth  metatarsal  bones.  It  is  important 
to  remember  that  the  dorsal  surface  faces  almost  as  much  outward  as  it  does  upward. 
The  dorsal  surface,  slightly  rough,  has  the  following  outline  :  an  oblique  posterior 
border  against  the  calcaneum,  which,  though  most  often  convex,  may  be  concave, 
sinuous,  or  straight  ;  a  short  outer  concave  one  ;  an  internal  one,  at  first  straight 
when  against  the  scaphoid,  and  slanting  outward  when  against  the  external  cunei- 
form ;  and  an  anterior  one,  slanting  outward  and  backward.     The  plantar  surface 


Fig.  434. 


Promontory 
Right  cuboid. 


For  inf.  calcaneocuboid  ligament 
-  aspect ;  B,  posterior,  outer,  and  inferior  s 


Promontory 
lrfaces. 


has  essentially  the  same  shape,  only  the  angle  between  the  posterior  and  inner 
borders  is  drawn  out.  Owing  to  the  oblique  position  of  the  bone,  this  fits  into  the 
upper  inner  angle  of  the  anterior  surface  of  the  calcaneum.  _  Just  below  this  angle  is 
a  prominence,  the  plantar  tubercle.  A  thick,  rounded,  oblique  ridge,  the  promon- 
tory or  tuberosity,  starting  at  the  back  of  the  outer  border,  runs  forward  and  inward 
across  the  bone  behind  a  groove  between  it  and  the  anterior  border.  The  tendon  of 
the  peroneus  longus  lies  on  the  smooth  anterior  slope  of  the  promontory,  the  outer 

1  Os  cuboideum. 


THE   ASTRAGALUS. 


423 


part  of  which  is  coated  with  cartilage.  The  external  surface  of  the  bone  is  deeply 
notched.  The  internal  surface  is  mostly  rough,  but  presents  at  about  the  middle 
an  articular  facet  for  the  external  cuneiform,  broad  above,  narrow  below,  and  not  usu- 
ally reaching  the  plantar  surface.  Commonly  another  smaller  facet  for  the  scaphoid 
is  found  behind  this  one,  from  which  it  is  separated  sometimes  completely,  but  more 
often  merely  by  a  ridge,  which  makes  no  real  interruption.  The  anterior  surface, 
articular  for  the  bases  of  two  metatarsals,  has  an  inner,  an  upper,  and  a  lower  border, 
the  two  latter  meeting  at  a  rounded  angle  externally.  A  faint  vertical  ridge,  nearer 
the  inner  than  the  outer  border,  usually  divides  this  facet  into  an  inner  oblong  and 
an  outer  triangular  part  for  the  fourth  and  fifth  bones.  The  curves  of  these  articu- 
lations vary  greatly  :  sometimes  both  parts  are  concave  from  above  downward  ; 
sometimes  both  are  practically  plane.  The  posterior  surface,  entirely  articular, 
is  the  complement  of  the  front  of  the  os  calcis.  The  cuboid  articulates  with  the 
calcaneum,  the  external  cuneiform,  the  fourth  and  fifth  metatarsal  bones,  often  with 
the  scaphoid,  and  at  times  with  the  astragalus. 

Development. — There  is  but  one  centre,  appearing  at  about  birth  ;  in  our 
experience,  more  often  after  than  before. 

For  Secondary  Cuboid,  see  Scaphoid. 

THE  ASTRAGALUS. 
The  astragalus,  '  or  talus,  is  a  very  irregular  bone  devoted  almost  wholly  to 
articular  surfaces.  It  is  enclosed  above  by  the  socket  of  the  leg  bones.  Its  main 
part,  or  body;  rests  on  the  calcaneum,  and  presents  in  front  a  constricted  neck 
bearing  a  rounded  head,  projecting  forward  and  inward  into  the  hollow  on  the  back  of 
the  scaphoid.  The  upper  surface  presents  a  pulley-like  articular  facet  covering  the 
greater  part  of  the  bone,  convex  from  before  backward,  slightly  concave  transversely, 
decidedly  broader  in  front  than  behind.  The  cartilage  covering  it  is  continued 
down  on  either  side  to  meet  the  articular  surfaces  of  the  malleoli.     The  inner  border 


Fig.  436. 


of  the  upper  articular  surface  is  distinct,  but  generally  not  sharp  ;  the  outer,  which 
reaches  higher,  is  better  defined  in  the  region  just  anterior  to  its  middle,  but  behind 
on  the  dry  bone  it  seems  rounded.  A  very  well-marked  bone  shows  (what  is  very 
striking  in  the  freshly  opened  joint)  that  this  blunted  edge  is  really  a  narrow  tri- 
angular area  belonging  to  the  superior  surface,  broadest  behind,  made  apparently 
by  the  pressure  of  the  posterior  tibio-fibular  ligament  from  the  external  malleolus  to 


424 


HUMAN   ANATOMY. 


the  back  of  the  tibia.  A  much  smaller  similar  surface  is  found  at  the  front,  made 
by  the  corresponding  anterior  ligament.  The  direction  of  the  anterior  border  of  the 
articular  surface  is  very  uncertain.  It  usually  projects  forward  at  the  outer  end,  the 
rest  being  either  transverse,  posteriorly  concave,  or  oblique.  Just  anterior  to  it  is  a 
deep  transverse  hollow  on  the  upper  surface  of  the  neck,  which  receives  the  edge  of 
the  tibia  in  extreme  dorsal  flexion  of  the  foot.  The  posterior  border  of  the  articular 
surface  is  also  of  uncertain  shape.  Its  inner  end  is  usually  somewhat  farther  back 
than  the  outer.      Behind  it  two  rough  tubeixles  project  backward,  slanting  down  to 


Fig.  437. 


Calcaneum 
:o-astragaloid  joint  • 


Astragalus 
ided  anterior  articular  facet  on  calcaneum. 


a  posterior  sharp  edge.  Between  them  is  a  deep  groove  for  the  tendon  of  the  flexor 
longus  hallucis,  running  obliquely  downward  and  inward.  The  outer  tubercle, 
which  is  much  the  larger,  is  sometimes  separated  by  a  suture  from  the  rest  of  the 
bone,  and  is  then  known  as  the  os  trigomim.  The  inner  tubercle  may  be  barely 
distinguishable.  This  region  behind  the  superior  articular  facet  is  sometimes  de- 
scribed as  the  posterior  surface  of  the  bone.  The  external  surface  of  the  body 
shows  the  triangular  facet  for  the  outer  malleolus,  concave  from  above  downward, 


Fig.  438. 


Synovial  not  cartilagi 


For  scaphoid 


internal  calcaneo- 
caphoid  ligament 


For  sustentaculu 


Type  of  calcaneo-astragaloid  joint  when  anterior  facet  < 


Astragalus 
calcaneum  is  not  only  divided  but  has  front  porti< 


with  the  lower  end  projecting  outward,  plane  or  convex  from  before  backward. 
This  is  bounded  before  and  behind  by  a  rough  strip,  with  a  hollow  at  the  upper 
ends  for  the  front  and  back  bundles  of  the  external  ligament  of  the  ankle.  The 
internal  surface  has  at  the  top  a  narrow  curved  facet  for  the  inner  malleolus,  with 
a  concave  lower  border,  deepest  in  front  and  pointed  behind.  A  part  of  the  internal 
lateral  ligament  is  inserted  into  a  hollow  below  it.  The  inferior  surface  of  the 
body  presents  a  four-sided  facet,  concave  in  the  line  of  its  long  axis,  which  is  oblique, 
corresponding  to  that  of  the  greater  surface  on  the  top  of  the  calcaneum.  In  front 
of  and  parallel  to  this  is  a  deep  groove  for  the  interosseous  ligament,  expanding  at 
the  outer  end  into  a  trianerular'hollow  on  the  under  side  of  the  neck.      This  is  a 


THE   SCAPHOID.  425 

constricted  portion,  much  broader  transversely  than  vertically,  connecting  the  head 
with  the  body.  It  often  presents  a  groove  along  the  upper  and  inner  aspect  near 
the  articular  surface  of  the  head  for  the  insertion  of  the  ligament  passing  to  the 
scaphoid.  The  head,  which  points  forward  and  inward,  is  articular  in  front  and 
below.  The  anterior  surface,  which  fits  into  the  hollow  on  the  back  of  the  scaph- 
oid, is  vaguely  oval,  with  its  long  axis  running  downward  and  inward.  The  upper 
edge,  parallel  with  this,  is  nearly  straight.  The  articular  surface  of  the  head  ex- 
tends onto  the  under  side,  reaching  to  the  deep  groove  separating  the  neck  from 
the  posterior  facet  for  the  calcaneum.  On  a  fresh  bone  the  cartilage  shows  the 
following  facets,  which  are  less  well  marked  on  a  macerated  one  :  a ,  facet  on  the 
front  of  the  head  to  fit  into  the  scaphoid  ;  one  on  the  lower  and  inner  side  to 
rest  on  the  anterior  articular  facet  of  the  top  of  the  calcaneum  ;  one  partly  between 
these,  which  in  the  dried  bones  would  be  free,  appearing  between  the  sustentaculum 
and  the  scaphoid,  but  in  life  resting  on  the  inferior  calcaneo-scaphoid  ligament, 
which  is  partly  covered  with  cartilage  and  elsewhere  with  synovial  membrane, 
forming  a  part  of  the  socket.  The  cartilage  on  this  surface  is  distinguished  by  its 
thinness.  These  facets  are  modified  according  to  the  arrangement  of  those  on  the 
calcaneum.  If  there^oe  but  one  long  anterior  facet  on  both  sustentaculum  and  on 
the  end  of  the  body  of  the  calcaneum,  the  facet  on  the  head  for  the  anterior  facet 
of  the  calcaneum  reaches  that  for  the  concavity  of  the  scaphoid  in  front,  leaving 
internally  a  triangular  interval  between  the  two,  occupied  by  the  facet  for  the  liga- 
ment (Fig.  437).  In  the  other  extreme  (Fig.  438),  where  the  anterior  facet  on 
the  calcaneum  does  not  reach  beyond  the  sustentaculum,  the  area  of  the  head  rest- 
ing against  the  ligament  completely  separates  the  two  others  and  plays  on  that  part 
of  the  calcaneum  where  the  anterior  articular  cartilage  should  be.  Finally,  when 
the  anterior  facet  on  the  calcaneum  is  divided  into  two,  the  corresponding  facet  may 
be  completely  subdivided  by  an  interruption  of  the  cartilage,  or  in  less  marked 
forms  there  may  be  merely  a  ridge  breaking  the  surface  into  two,  but  without  sepa- 
ration ;  such  a  ridge  is  often  found  even  when  the  opposed  articular  surface  is  not 
divided.  The  lines,  however,  on  the  head  of  the  astragalus  do  not  strictly  correspond 
to  the  boundaries  of  these  surfaces.  The  astragalus  articulates  with  four  bones, — the 
tibia,  fibula,  calcaneum,  and  scaphoid. 

Development. — The  nucleus  probably  appears  at  about  the  seventh  month  of 
fcetal  life.  When  the  os  trigonum  occurs,  that  implies  another  centre  for  the  ex- 
ternal tubercle  and  the  part  of  the  articular  surface  under  it. 

The  deviation  of  the  axis  of  the  neck  from  that  of  the  long  axis  of  the  bone 
varies  considerably  among  individuals,  but,  nevertheless,  changes  during  develop- 
ment. In  the  adult  the  angle  varies  from  o  to  240,  the  mean  of  forty-three  bones 
being  12. 320.  In  the  foetus  (presumably  at  term)  the  angle  ranges  from  17. 50  to 
45.5°,  the  mean  of  twenty- two  bones  being  35. 760.1 

THE  SCAPHOID. 
The  scaphoid,2  or  navicular,  may  be  compared  to  a  disk,  concave  behind  where 
it  fits  onto  the  head  of  the  astragalus,  convex  in  front  where  it  rests  on  the  three 
cuneiform  bones.  It  is  thinner  at  the  outer  end,  where  it  touches  the  cuboid,  than 
at  the  inner,  where  it  presents  the  tuberosity.  The  superior,  or  dorsal,  surface 
is  long  transversely.  Its  posterior  border  is  regularly  concave,  the  anterior  slightly 
scalloped,  presenting  two  small  points  projecting  forward  on  either  side  of  the  mid- 
dle cuneiform.  When  in  position  the  highest  point  on  the  scaphoid  is  behind  that 
bone.  The  greater  part  of  the  dorsal  surface  slants  downward  on  the  inner  side  of 
the  foot.  The  inferior,  or  plantar,  surface  is  rough,  and  in  the  main  transversely 
concave.  The  tuberosity  at  the  inner  border  for  the  attachment  of  a  part  of  the  tibi- 
alis posticus  muscle  is  a  knob  formed  by  the  junction  of  the  dorsal  and  plantar  sur- 
faces, and  projecting  downward  chiefly  into  the  sole  of  the  foot.  The  end  of  the 
knob  is  sometimes  distinct  from  the  scaphoid,  and  is  known  as  the  tibiale  externum. 

1  C.  L.  Scudder  :  Congenital  Talipes  Equino-Varus,  Boston  Med.  and  Surg.  Journ.,  vol. 
ii.,  1887.     Parker  and  Shattock  :  The  Pathology  and  Etiology  of  Congenital  Club-Foot,  London, 


426 


HUMAN   ANATOMY. 


Its  identity  is  quite  evident  in  cases  in  which,  though  fused,  it  projects  as  a  hook. 
It  may  be  represented  by  the  sesamoid  bone  in  the  tendon  of  the  tibialis  posticus. 
Near  the  outer  end  of  the  plantar  surface  there  is  almost  always  a  slight  projection 
by  the  side  of  the  cuboid  which  may  be  very  much  developed,  extending  to  near 
the  notch  in  front  of  the  sustentaculum  of  the  calcaneum,  in  which  case  it  is  known  as 
the  secondary  cuboid.  The  external  surface  is  narrow  and  rough,  resting  against 
the  cuboid,  with  which  it  articulates  in  about  half  the  cases  by  a  facet  near  the  dor- 
sum, which  rarely  extends  far  towards  the  sole.1  The  posterior  surface  is  con- 
cave, in  the  main  oval  and  completely  articular.  Usually  the  regularity  of  the 
lower  border  is  interrupted  near  the  outer  part  by  the  external  knob  of  the  plantar 
surface.  If  this  be  much  developed  the  shape  of  the  posterior  surface  is  changed 
from  oval  into  quadrilateral,  but  it  is  always  articular  throughout.  The  anterior 
surface  is  slightly  convex  and  entirely  articular,  except  when  the  process  just  men- 
tioned is  so  large  as  to  appear  below  it.      The  articular  surface  is  divided  into  three 

Fig.  440. 

Dorsal  surface 


For  head  of  astragalu 
Right  scaphoid  from  behind,  proximal  aspect. 


Right  scaphoid  from  in  front. 


facets,  in  the  main  triangular,  corresponding  to  the  outline  of  the  bases  of  the  three 
cuneiform  bones.  The  character  of  these  facets  is  not  constant  :  the  inner  is  usually 
convex  and  the  outer  concave. 

The  scaphoid  articulates  with  the  astragalus,  the  three  cuneiform  bones,  often 
with  the  cuboid,  and  exceptionally  it  touches  or  joins  the  calcaneum.  The  secondary 
cuboid,  above  alluded  to,  has  but  once  been  seen  isolated,  although  we  have  met  with 
one  foot  in  which  it  seemed  possible  that  it  might  have  been  distinct  earlier.  It  is 
fused  with  either  the  cuboid  or  the  scaphoid,  but  apparently  much  more  frequently 
with  the  latter,  in  which  it  occupies  the  position  above  described,  lying  at  the  weak 
part  of  the  inferior  calcaneo-scaphoid  ligament. 

Development. — It  is  generally  held  that  ossification  begins  in  the  fourth  or 
fifth  year,  but,  according  to  Gegenbaur,  it  begins  in  the  first.  The  tibiale  externum 
exists  as  a  separate  cartilage  at  the  second  month  of  fcetal  life.  Usually  this  fuses 
with  the  rest,  but  it  may  have  a  centre  of  its  own. 

THE   THREE    CUNEIFORM    BONES. 

These  wedge-shaped  bones,  placed  between  the  scaphoid  and  the  three  inner 
metatarsals,  and  abutting  externally  on  the  cuboid,  form  an  important  part  of  the 
transverse  arch  of  the  foot.  The  thin  edge  of  the  internal  cuneiform,  which  is  much 
the  largest,  points  up,  that  of  the  others  down.  The  middle  cuneiform  is  the  smallest 
and  shortest,  so  that  the  second  metatarsal  bone  lies  in  a  mortise  between  the  inner 
and  outer. 

THE    INTERNAL    CUNEIFORM. 

The  internal  cuneiform,2  besides  the  proximal  and  distal  surfaces,  has  an  internal, 
an  external,  and  an  inferior.  The  posterior,  or  proximal  surface,  rounded  below 
and  pointed  above,  is  slightly  concave  and  wholly  articular.  The  anterior,  or  distal, 
surface,  also  articular,  is  kidney-shaped,  with  the  notch  in  the  outer  border.  The 
inner  surface  has  a  small  ridge  in  its  distal  half,  pointing  upward,  which  is  the 
'Pfitzner:  Morph.  Arbeiten,  Bd.  vi.,  1S96. 


THE   CUNEIFORM    BONES. 


427 


highest  part  of  the  bone,  but  almost  the  whole  of  this  surface  is  on  the  inner  side  of 
the  foot.  Its  outer  border  runs  obliquely  forward  and  outward  with  a  sinuous 
course  till  it  reaches  the  end  of  the  middle  cuneiform,  when  it  turns  forward.  It 
has  a  short  concave  posterior  border  for  the  scaphoid  and  a  long,  nearly  straight 
one  for  the  first  metatarsal  bone.  It  passes  without  a  sharp  boundary  into  the 
lower  surface.  It  is  crossed  by  a  faint  groove,  which  exceptionally  is  deep,  running 
obliquely  downward  and  forward  to  a  smooth  swelling  for  a  bursa  under  the  tendon 


Fig.  441. 


Fig.  442. 


Mid.  cuneiform 


ineiform,  outer  aspect. 


Right  internal  cuneifo 


of  the  tibialis  anticus  just  before  its  insertion.  The  inferior  surface,  rough  and 
round,  has  a  tubercle  near  the  proximal  end  for  a  part  of  the  tibialis  posticus.  The 
external  surface  is  mostly  rough,  with  a  smooth  articular  strip  for  the  middle 
cuneiform  following  its  upper  and  posterior  border.  The  internal  cuneiform  articu- 
lates with  the  scaphoid,  middle  cuneiform,  and  first  and  second  metatarsal  bones. 

Development. — A  centre  appears  in  the  third  year.  Very  exceptionally  it  is 
double,  and  the  bone  is  divided  by  a  suture  into  two, — a  dorsal  and  a  plantar. 

THE    MIDDLE    CUNEIFORM. 

The  middle  cuneiform  1  has  a  sharp  ridge  below  and  an  oblong  surface  above. 
The  latter,  or  superior  surface,  is  very  little  longer  than  broad.  The  lateral 
borders  of  this  surface  have  an  outward  inclination.  The  inner  of  them  corresponds 
to  the  proximal  part  of  the  outer  border  of  the  first  cuneiform.  The  outer  border, 
for  its  proximal  two-thirds,  rests  against  the  external  cuneiform,  beyond  which  there 
is  a  small  space  between  the  bones.  The  proximal  side  of  this  surface  is  a  little 
convex  and  the  distal  about  straight.      The  posterior  surface,  wholly  articular, 

Fig.  443. 


'  aspect ;  B,  outer  aspect. 


is  slightly  concave.  It  is  triangular,  with  the  dorsal  border  rounded,  the  outer 
concave,  and  the  inner  straight  or  slightly  convex.  The  anterior  surface,  ar- 
ticular for  the  second  metatarsal,  is  narrower.  It  has  a  slight  convexity  in  the  upper 
part  in  a  vertical  plane.  The  internal  surface  has  an  articular  facet  corresponding 
to  that  on  the  internal  cuneiform  and  a  rough  depression  for  an  interosseous  liga- 
ment. The  external  surface  has  a  facet  along  the  hind  border,  broader  above 
than  below,  and  rarely  a  small  one  at  the  front  lower  angle,   both  for  the  external 

1  Os  cuneiforme  secundum. 


428  HUMAN    ANATOMY. 

cuneiform.      The  middle  cuneiform  articulates  with  the  scaphoid,   the  internal  and 
external  cuneiforms,  and  the  second  metatarsal. 

Development. — One  centre  appears  in  the  fourth  year. 

THE    EXTERNAL    CUNEIFORM. 

The  external  cuneiform,1  seen  from  above,  is  much  longer  than  broad,  with  a 
very  oblique  proximal  border  slanting  outward  and  backward,  an  anterior  border 
running  less  obliquely  in  the  same  direction,  an  inner  one  close  against  the  middle 
bone  in  its  proximal  third  or  one-half,  then  receding  from  it  and  extending  onto  the 
outer  side  of  the  second  metatarsal,  and  an  outer  border  first  running  forward  and 
outward  against  the  cuboid,  and  then  forward  not  quite  against  it,  but  overlapping 
the  fourth  metatarsal.  The  ridge  constituting  the  inferior  surface  does  not  quite 
reach  the  proximal  end.  The  posterior  surface,  wholly  articular,  is  oblong,  with 
the  long  axis  vertical,  and  often  a  little  convex.  The  anterior  surface,  articular  for 
the  third  metatarsal,  is  triangular  and  about  plane.  Its  inner  border  rises  higher 
than  the  outer.     The  internal  surface  articulates  with  the  second  cuneiform  bone  by 

Fig.  444. 


Fourth 

metatarsal 
Third 

metatarsal 


Right  external  cuneiform.     A,  inner  aspect ;  B,  outer  aspect. 


one  or  two  corresponding  facets,  as  the  case  may  be,  and  has,  in  addition,  a  facet  for 
the  outer  side  of  the  base  of  the  second  metatarsal  at  the  front  upper  angle,  and 
often  extending  down  the  border  ;  or  the  middle  portion  may  be  wanting.  In  the 
middle  of  the  surface  is  a  roughness  for  the  interosseous  ligament.  The  external 
surface  is  chiefly  rough,  giving  origin  to  an  interosseous  ligament  for  the  cuboid  ; 
at  the  upper  proximal  angle  is  a  large  facet  for  the  same  bone,  and  at  the  distal 
upper  angle  there  may  or  may  not  be  a  small  one  for  the  side  of  the  fourth  meta- 
tarsal. The  external  cuneiform  articulates  with  the  scaphoid,  the  middle  cuneiform, 
the  cuboid,  and  the  second,  third,  and  fourth  metatarsals. 

Development. — Ossification  begins  in  the  first  year. 

The  Intercuneiform  Bone. — On  the  dorsum  there  is  a  little  pit  which  we 
have  called  the  intercuneiform,  fossa,  situated  between  the  proximal  portions  of  the 
internal  and  middle  cuneiform  bones,  usually  more  at  the  expense  of  the  latter  than 
of  the  former.  We  have  at  least  twice  seen  a  separate  ossicle,  the  intercuneiform 
done,2  in  this  fossa.  The  better  specimen  was  wedge-shaped,  its  length  exceeding 
one  centimetre.  It  clearly  was  more  intimately  related  to  the  middle  than  to  the 
internal  cuneiform.      Pfitzner  has  since  seen  it  fused  with  the  former. 

THE    METATARSAL    BONES. 

Of  these  five  bones 3  the  first  is  very  much  the  largest,  although  the  shortest. 
The  second  is  the  longest,  and  the  others  of  about  equal  length. 

The  first  metatarsal  bone  has  a  concave  base  corresponding  to  the  facet  on 
the  internal  cuneiform,  which  is  prolonged  down  into  a  point  (tuberosity)  rather 
to  the  outer  side,  on  the  external  aspect  of  which  the  peroneus  longus  is  inserted 
into  a  round  impression.  On  the  inner  side  of  the  base  is  a  small  prominence  for 
the  tibialis  anticus.  A  smooth  facet  for  the  second  metatarsal  is  often  found  on  the 
outer  side.  A  groove  for  the  capsular  ligament  more  or  less  perfectly  encircles  the 
2Anat.  Anzeiger,  Bd.  xx.,  1902. 

1  Os  cuneifornie  tertium.     30ssa  metatarsalia  I-V. 


THE    METATARSAL    BONES. 


429 


base.      The  strong  shaft  has  three  sides  :  an  internal,  looking  also  upward,  in  the 
main  convex  ;  an  external,  concave  and  nearly  vertical  ;  and  an  inferior,  or  plantar, 


Fig.  445. 

B 
Grooves  for  sesamoid  bones 


Phalangeal  surface 


cuneilorm 
External  surface 


Impression  of  peroneus  longus  Tuberosity  Internal  cuneiform 

Right  first  metatarsal.    A,  proximal  aspect ;  B,  plantar  aspect ;  C,  dorsal  aspect. 

also  concave.      The  borders  bounding  the  outer  surface  are  the  most  distinct.      One 
or  two  nutrient  foramina  enter  this  surface,  running  distally.      The  enlarged  and 

Fig.  446. 


External  cuneiform 
Right  second  metatarsal.    A,  proximal  aspect ;  B,  outer  aspect ;  C, 


rounded  distal  end,  the  head,  is  articular  except  at  the  sides,  where  it  is  flattened. 
The  facet  extends  farther  onto  the  plantar  aspect,  where  it  expands  laterally.      It 


43° 


HUMAN    ANATOMY. 


has  there  a  median  elevation,  with  a  groove  on  either  side  for  a  sesamoid  bone. 
There  is  a  rough  surface  for  ligaments  on  each  side  of  the  head. 

Fig.  447. 


Middle  cuneifo 


Second  metatarsal 

RBHflk 

Fourth  metatarsal 

External  cuneiform 
Right  third  metatarsal.    A,  proximal  aspect ;  Bt  outer  aspect ;  C,  inner  aspect. 

The  four  outer  metatarsal  bones  are  distinguished  by  their  bases.  That 
of  the  second  is  concave  at  the  end,  and  fits  the  middle  cuneiform  ;  on  the  inner 
side  a  small  facet  at  the  top  meets  the  outside  of  the  first  cuneiform  ;  on  the  outer 
side  there  are  two,  an  upper  and  a  lower,  with  a  deep  cut  between  each,  resting 

Fig.  44S. 


Third  metntarsa 


External  c 
metatarsal 


Right  fourth  metatarsal.     A,  proximal  aspect;  B,  outer  aspect 


on  both  the  outer  cuneiform  and  the  third  metatarsal.      The  occasional  facet  for  the 
first  metatarsal  is  on  the  shaft  rather  than  on  the  end.      It  is  often  wanting  on  the 


THE    METATARSAL    BONES. 


43i 


second  when  present  on  the  first,  implying  the  presence  of  a  bursa  rather  than  of  a 
joint.  The  base  of  the  third  metatarsal  fits  the  outer  cuneiform,  and  is  nearly 
plane.      The  posterior  upper  border,    seen  from  the  dorsum,   is  oblique,   running 

Fig.  449. 


Tuberosity  J  /J 


Right  fifth  metatarsal.    A,  distal  aspect ;  B,  dorsal  aspect ;  C,  plantar  aspect. 

outward  and  backward.      The  inner  surface  has  two  facets  for  the  second,  and  the 

outer  surface  one  at  the  top  for  the  fourth  metatarsal.      The  base  of  the  fourth 

metatarsal  is  also  oblique.      It  has  an  oblong  facet  for  the 

cuboid,  and  a  single  internal  one  at  the  top  for  the  third,  Fig.  45°. 

which  is  separated  from  the  proximal  end  by  a  rough  space 

for  the  insertion  of  an  interosseous  ligament  from  the  tarsus. 

There    is   externally  a   triangular  facet   at  the  upper  angle 

for  the  fifth.      This  last  facet  is  bounded  in  front  by  a  deep 

groove  which  receives   the  edge   of    the  facet  on  the  fifth. 

The  fifth  metatarsal  has  an  even  more  oblique  base,  the 

inner  two-thirds  of  which  bear  a  facet  for  the  cuboid.      The 

outer  part  is  prolonged  as  the  tuberosity  beyond  the  edge 

of   the  foot,  overhanging  the   joint.      The  inner  side  has  a 

facet  for  the  fourth  metatarsal  bone. 

The  shafts  of  the  metatarsal  bones  are  flattened  lat- 
erally, but  theoretically  three-sided,  like  the  first.  The 
second  has  an  external  surface  looking  directly  outward  ;  a 
superior  one  at  the  base,  which  twists  so  as  to  become  in- 
ternal. This  is  separated  from  the  former  in  the  distal  two- 
thirds  of  the  shaft  by  a  sharp  ridge.  The  third  side  is  internal 
at  the  base,  but  soon  becomes  inferior.  The  shaft  of  the 
third  differs  only  slightly,  the  external  surface  looking  some- 
what upward  and  there  being  more  of  a  ridge  below.  In 
the  fourth  it  seems  as  if  the  proximal  part  of  the  shaft  had 
been  bent  outward  on  its  axis,  so  that  the  outer  side  looks 
more  upward  and  the  other  two  are  less  twisted.  In  the 
fifth  this  process  has  gone  farther ;  the  originally  outer  side 
is  now  the  upper,  separated  by  one  border  from  the  inner  and  by  another  from  the 
inferior.  This  last  border,  now  external,  represents  the  one  that  was  the  inferior 
of  the  third  metatarsal.  The  nutrient  foramina  of  the  four  outer  metatarsals  are 
in  the  external  surfaces,  running  upward.      They  are  not  very  constant. 


Right  fifth  metatarsal, 
aspect. 


432 


HUMAN    ANATOMY. 


Fig.  451.      _ 

Os  intermetatarseum 


The  heads  of  the  metatarsal  bones  are  compressed,  like  the  shafts,  from  side 
to  side,  and  have  each  a  pair  of  lateral  tubercles  at  the  dorsal  aspect  of  the  end  of 
the  shaft,  separated  by  a  groove  from  the  articular  surface.  Lateral  ligaments  are 
attached  both  to  the  tubercles  and  the  grooves.  The  ar- 
ticular surface  is  oblong,  extending  well  onto  the  plantar 
side,  where  it  ends  in  two  lateral  prolongations,  of  which 
the  outer  is  the  more  prominent.  A  line  connecting  their 
ends  would  be  oblique  to  the  shaft,  especially  in  the  outer 
toes. 

Fusion  of  the  outer  cuneiform  with  its  metatarsal  occurs 
occasionally  at  the  plantar  aspect.  It  is  probably  con- 
genital. Pfitzner  has  seen  it  at  seventeen  and  we  at 
nineteen. 

Development. — Centres  for  the  shafts  of  the  meta- 
tarsals appear  towards  the  end  of  the  third  month  of  fcetal 
life.  A  proximal  epiphysis  for  the  first  and  distal  ones  for 
the  others  appear  in  the  third  year,  fusing  at  about  seven- 
teen. Occasionally  the  metatarsals,  especially  the  first, 
have  an  epiphysis  at  each  end. 
Os  Intermetatarseum. — This  is  an  occasional  wedge-shaped  bone  found  on 
the  dorsal  aspect  of  the  foot,  between  the  internal  cuneiform  and  the  first  and  second 
metatarsals.  It  may  articulate  with  all  three,  or  with  any  of  them,  or  be  attached  to 
them  by  connective  tissue.  More  often  it  is  connected  by  bone  with  one  of  the  three 
neighbors,  especially  with  the  internal  cuneiform,  of  which  it  may  seem  to  be  a  pro- 
cess (Fig.  451).      It  is  found  in  some  form  once  in  ten  feet  (Pfitzner). 


Intermetatarsal  bone  fused  with 
right  internal  cuneiform. 


THE   PHALANGES. 

There  are  two  for  the  great  toe  and  three  for  each  of  the  others.  Although  of 
very  different  proportions,  they  present  the  features  which  have  been  described  for 
those  of  the  hand,  especially  the  shape  of  the  articular  sur- 
faces. The  first  phalanx  of  the  great  toe  is  about  as  Fig.  452. 
long  as  that  of  the  thumb  and  nearly  twice  as  broad.  There 
is  a  tubercle  for  muscular  insertion  at  each  side  of  the  pal- 
mar aspect  of  the  base.  The  terminal  phalanx  of  the 
great  toe  is  also  very  massive.  The  first,  or  proximal,  pha- 
langes of  the  other  toes  diminish  in  length  from  within  out- 
ward. Those  of  the  second  row  are  so  short  as  to  be 
almost  cubical,  although  they  are  broader  than  thick.  The 
terminal,  or  distal,  phalanges  are  very  rudimentary. 
Pfitzner1  has  shown  that  in  about  one-third  of  the  cases  the 
terminal  phalanx  of  the  little  toe  is  fused  with  the  middle 
one,  even  before  birth.  Presumably  they  never  were  distinct 
in  the  embryo.  As  he  has  found  this  condition  in  Egyptian 
mummies,  certain  very  pessimistic  views  as  to  the  degener- 
ation in  store  for  the  human  foot  are  probably  unwarranted. 

Sesamoid  Bones. — Those  of  the  first  metatarsopha- 
langeal joint  are  large  and  constant  ;  those  of  the  same  joint 
in  the  other  toes  very  rare.  The  least  uncommon  are  those 
of  the  fifth  toe,  of  which  the  inner  sesamoid  is  found  in  5.5 
per  cent,  and  the  outer  in  6.2  per  cent.  A  sesamoid  of  the 
interphalangeal  joint  of  the  great  toe  is  found  in  50.6  per 
cent.  (Pfitzner2). 

Development. — The  first  nucleus  to  appear  is  that  of 
the  distal  phalanx  of  the  great  toe  at  the  end  of   the  third 
fcetal  month.      Those  of  the  other  distal  phalanges,  except  the  fifth,  come  some  two 
weeks  later.     The  bones  of  the  proximal  row  seem  to  ossify  rather  later  than  the 

1  Arch,  fur  Anat.  und  Entwick.,  1890. 

2  Morph.  Arbeiten,  Bd.  i. 


Third,  distal 
or  ungual, 
phalanx 


Second,  or 
middle, 
phalanx 


First,  or 
proximal, 
phalanx 


Phalanges  of  right  second 
toe,  plantar  surface. 


THE    PHALANGES. 


433 


distal  ones,  but  this  order  is  not  constant.  According  to  Bade,1  the  middle  phalanges 
have  begun  to  ossify  in  the  eighteenth  week  of  foetal  life,  but  we  have  found  bone 
wanting  considerably  later.  The  process  of  ossification  in  the  fourth  and  fifth  toes 
is  decidedly  later  than  at  the  inner  side  of  the  foot.  It  does  not  begin  in  the  middle 
phalanx  of  the  fifth  till  near  term,  and  we  have  sometimes  seen  no  sign  of  it  in  the 


Fig.  453. 


Ossification  of  bones  of  the  foot.  A,  during  sixth  foetal  month;  B,  at  eighth  fcetal  month;  C.  at  birth;  D, 
during  first  year  ;  E,  between  three  and  four  years  ;  F,  at  about  fifteen  years,  a,  for  shaft  of  metatarsals  ;  *,  for  cal- 
caneum  •  c,  for  proximal  phalanges  ;  rf,  for  distal  phalanges  ;  e,  for  astragalus  ;/.  for  middle  phalanges  ;  £■ ,  for  cuboid  ; 
A,  for  external  cuneiform;  1,  for  heads  of  metatarsal  hones  and  base  of  first  proximal  phalanx  ;  j,  for  base  of  first 
distal  phalanx ;  k,  for  internal  cuneiform  ;  /,  for  base  of  first  metatarsal. 


fifth,  and  even  in  the  fourth  at  birth.  Proximal  epiphyses  appear  from  the  fourth  to 
the  sixth  year,  and  fuse  at  about  sixteen.  The  terminal  phalanges  have  distal  caps 
like  those  of  the  hand.  The  fifth  toe,  according  to  Pfitzner,  has  the  following  pecu- 
liarities :  the  proximal  epiphysis  of  the  second  phalanx  and  the  centre  for  the  shaft 
of  the  terminal  one  are  wanting,  the  proximal  epiphysis  of  the  latter  being  greatly 
exaggerated. 


Arch,  fur  Mik.  Anat. 
28 


Bd.  lv.,  1900. 


434 


HUMAN    ANATOMY. 
Fig.  454- 


Groove  for  tendon  of 
flexor  long  us  hallucis 


Sustentaculum  tal 


Sesamoid  bones 


Abductor  and  fit 

brevis  hallucis 
Adductores  obhq\ 
et  iransversus 


Flexor  longus  hallucis 


Tibialis  post 

External  cuneiform 
Middle  cuneiform. 
Internal  cuneiform 

Tibialis  antic  us 


Peroneus  lo?igu 


First  metatarsal. 


Bones  of  right  foot,  plantar  aspect. 


BONES   OF   THE   FOOT. 
Fig.  455. 


435 


Tendo  Achillis 
Bursal  surface 


Lateral  articular  surface  for  fibul 
Groove  for  peroneus  long, 


Groove  for 
Extensor  brevis  digit 


Peroneus  terti 


Fourth  dorsal interosse 


Groove  for  flexor  longus  hallucis 


Superior  articular  surface  of 
astragalus 


Cuboid 
Scaphoid 

External  cuneiform 

Middle  cuneiform 

Internal  cuneiform 


First  metatarsal 


First  dorsal  intero 


Extensor  bi  ens  hallucis 


Extensor  brevis  digitor 

Extensor  longus  digit  or  u 


Extensor  longus  hallucis 


Bones  of  right  foot,  dorsal  aspect. 


436  HUMAN   ANATOMY. 


PRACTICAL   CONSIDERATIONS. 

The  union  of  the  foot  with  the  leg  at  a  right  angle,  while  necessitated  by  the 
erect  attitude  of  man,  makes  it  essential  that  the  bones  of  the  foot  shall  be  so  shaped 
and  united  that  they  may  afford  a  basis  for  both  support  and  propulsion,  all  pre- 
hensile function  being  sacrificed  to  those  ends.  Accordingly,  we  find  the  tarsus 
proportionately  much  larger,  both  it  and  the  metatarsus  stronger,  and  the  pha- 
langes much  smaller  and  less  mobile  than  the  corresponding  parts  of  the  hand. 
The  strength  of  the  foot  and  its  comparative  freedom  from  injury,  in  spite  of  its  con- 
stant exposure  to  traumatisms  of  various  grades  of  severity,  are  due  to  the  arrange- 
ment of  its  component  bones  into  the  form  of  an  arch,  which  is  well  adapted  not  only  to 
sustain  weight  and  to  provide  leverage  for  motion,  but  also  to  resist  and  distribute 
excessive  force  received,  as  in  falls  upon  the  feet.  The  posterior  pillar  of  the  arch, 
composed  of  the  os  calcis  and  the  hinder  portion  of  the  astragalus,  has  but  one  joint 
— the  calcaneo-astragaloid — with  a  very  limited  range  of  motion.  The  action  of  the 
calf  muscles  upon  the  heel  is  thus  applied  to  the  elevation  of  the  hinder  pillar  with 
the  least  possible  expenditure  of  force,  as  there  are  no  unnecessary  movements 
between  their  point  of  insertion  and  the  ankle-joint. 

The  anterior  pillar  beginning  at  the  top  of  the  astragalus — the  summit  of  the 
arch — may  be  said  to  include  practically  most  of  the  foot  anterior  to  the  ankle  and  to 
separate  naturally  into  ( I )  a  larger  and  stronger  inner  division  consisting  of  the  neck 
and  head  of  the  astragalus,  the  scaphoid,  the  three  cuneiforms,  and  the  three  inner 
metatarsals  ;  and  (2)  a  weaker  and  smaller  outer  division  composed  of  the  cuboid 
and  the  remaining  metatarsals. 

The  anterior  pillar  thus  secures  in  the  wide  surface  of  the  distal  extremities  of 
the  metatarsal  bones  a  broad  basis  of  support  ;  its  inner  division  carries  most  of  the 
weight,  and  is  enabled  to  do  this  by  the  thickness  and  strength  of  the  metatarsal  bone 
of  the  great  toe  and  by  the  parallelism  of  the  latter  with  the  great  toe  ;  its  outer 
division  bears  less  weight,  but  supports  the  inner  division  laterally  and  broadens  the 
surface  in  contact  with  the  ground.  The  normal  foot  thus  rests  directly  upon  the  os 
calcis  and  the  anterior  extremities  of  the  metatarsals,  the  outer  side  of  the  foot  aiding 
more  in  preserving  balance  than  in  carrying  weight. 

An  imperfect  transverse  arch — including  the  scaphoid,  cuboid,  and  cuneiforms — 
adds  to  the  elasticity  of  the  foot  and  aids  the  main  arch  in  affording  a  pressure-free 
area  for  the  plantar  vessels  and  nerves.  Both  arches  depend  for  their  integrity  not 
only  upon  the  shape  of  the  bones,  but  also  upon  the  fasciae,  ligaments  and  tendons, 
and  to  some  extent  upon  the  small  plantar  muscles.  Still  another  transverse  arch  is 
formed  by  the  bases  of  the  metatarsal  bones,  and  a  third,  but  less  distinct  one,  by 
their  heads. 

Perhaps  the  most  accurate  conception  of  the  foot  mechanically  is  as  a  semi-dome 
(Ellis),  the  whole  dome  being  completed  in  well-shaped  feet  when  the  inner  borders 
are  approximated. 

The  epiphysis  of  the  os  calcis  occupies  the  posterior  rounded  extremity  of  the 
bone,  and  has  inserted  into  it  the  tendo  Achillis.  No  positive  clinical  evidence  of 
separation  exists,  but  it  is  probable  that  the  X-rays  will  show  that  in  young  persons 
lesions  heretofore  supposed  to  be  fractures  of  the  os  calcis  from  muscular  action  are 
actually  epiphyseal  disjunctions. 

The  epiphyses  of  the  remaining  bones  of  the  foot  have  but  little  surgical  interest. 
The  first  metatarsal,  like  that  of  the  thumb,  has  its  epiphysis  at  the  proximal  end, 
and  to  that  extent  resembles  a  phalanx.  The  other  four  metatarsals  have  their  epiph- 
yses at  the  distal  ends.  All  the  phalangeal  epiphyses  are  at  the  proximal  ends. 
In  the  metatarso-phalangeal  joints  the  synovial  membrane  is  in  close  relation  to  the 
epiphyseal  lines  ;  in  the  phalangeal  joints  it  is  not.  A  knowledge  of  these  facts  may 
occasionally  be  useful  in  cases  of  disease  or  injury  limited  to  a  particular  bone. 

F}-acture  of  the  bones  of  the  tarsus  is  rare,  except  as  a  result  of  crushing  injuries 
or  of  falls  from  considerable  heights.  If  the  bones  of  the  anterior  pillar  are  broken, 
it  is  usually  by  direct  violence,  as  the  numerous  joints  and  ligaments  of  this  region 
render  it  so  elastic,  and  so  diffuse  forces  applied,  as  in  jumps  or  falls,  as  effectually  to 


PRACTICAL    CONSIDERATIONS  :    THE    FOOT    BONES.  437 

prevent  fracture.  The  bones  of  the  posterior  pillar  are  broken  in  both  ways.  In 
falls  the  astragalus  is  apt  to  break  about  its  neck, — the  weakest  portion  ;  or  if  the 
foot  is  strongly  dorsiflexed,  the  anterior  articular  edge  of  the  tibia  may  act  as  a 
wedge  and  split  it  across.  The  os  calcis  may  be  broken  between  the  astragalus  and 
the  ground, — compression  fracture  ;  or  it  may  be  broken  behind  the  insertion  of  the 
inferior  calcaneo-scaphoid  ligament,  the  anterior  arch  being  flattened  by  the  fall,  but 
the  ligament  resisting  rupture.  A  few  cases  of  fracture  of  the  sustentaculum  tali  have 
been  reported,  the  foot  having  been  in  forcible  inversion,  the  lesser  process  (susten- 
taculum) being  broken  off  against  the  edge  of  the  astragalus.  In  each  case  this  was 
followed  by  eversion  and  sinking  of  the  inner  border  of  the  foot  (valgus),  the  support 
given  by  the  internal  articulating  surface  to  the  astragalus  having  been  removed. 

Of  the  metatarsal  bones,  the  first,  although  the  strongest,  is  most  frequently  broken 
because  it  carries  so  large  a  proportion  of  the  body  weight  and  because  it  receives  an 
undue  share  of  the  violence  in  falls  associated  with  eversion  of  the  foot.  The  fifth 
comes  next  in  frequency  because  of  its  exposed  position  on  the  outer  side  of  the  foot 
and  the  added  violence  in  cases  of  inversion. 

Dislocation  of  separate  bones,  especially  of  the  astragalus,  is  rare.  It  is  always 
the  result  of  the  application  of  considerable  crushing  force,  is  usually  associated  with 
other  injuries,  and  is  influenced  but  little  by  anatomical  factors. 

Disease  of  the  bones  of  the  foot,  and  especially  tuberculous  disease  of  the  tarsus, 
is  common  because  of  :  (1)  the  frequency  of  traumatism  ;  (2)  the  exposure  to  cold 
and  damp  and  the  scanty  protection  afforded  by  the  superjacent  tissues  ;  (3)  the 
remoteness  from  the  centre  of  circulation  and  the  dependent  position  of  the  part, 
both  favoring  congestions  ;  (4)  the  preponderance  of  cancellous  tissue  in  the  bones  ; 
and  (5)  the  difficulty  in  securing  perfect  rest,  especially  after  minor  injuries,  which 
are  those  most  often  followed  by  tuberculous  osteitis.  It  affects  most  frequently  those 
bones  that  bear  most  of  the  weight  of  the  body, — the  os  calcis,  the  head  of  the 
astragalus,  and  the  base  of  the  first  metatarsal.  It  is  more  likely  to  remain  localized 
when  situated  in  the  os  calcis  or  in  the  hinder  part  of  the  astragalus  ;  in  the  anterior 
portions  of  the  tarsus  the  number  and  complexity  of  the  synovial  cavities  (often 
intercommunicating)  tend  to  prolong  and  to  spread  the  disease.  In  disease  of  the 
tarsal  bones — excepting  the  astragalus,  to  which  no  muscle  is  attached — the  tendon 
sheaths  in  the  vicinity  may  be  involved  by  direct  extension  from  the  periosteum. 

Any  metatarsal  bone  may  be  involved  in  cases  of  ' '  perforating  ulcer, ' '  the  situa- 
tion of  the  latter  being  determined  usually  by  the  degree  of  pressure  upon  the  sole  in 
cases  in  which  anaesthesia  is  already  present  ;  hence  the  frequency  with  which  the  first 
metatarsal  is  involved  in  this  disease. 

Excision  of  the  separate  bones  has  frequently  been  performed,  especially  of  the 
astragalus  and  os  calcis. 

Landmarks. — On  the  inner  side  of  the  foot  can  be  felt  :  (a)  the  ridge  between 
the  inner  and  posterior  surfaces  of  the  os  calcis  ;  (6)  the  tubercle  of  the  os  calcis  ;  (c) 
the  sustentaculum  tali,  one  inch  directly  below  the  tip  of  the  malleolus  ;  (d)  from  one- 
half  to  three-quarters  of  an  inch  in  front  of  the  latter  the  head  of  the  astragalus,  very 
noticeable  in  flat-foot ;  (c)  from  one-half  to  three-quarters  of  an  inch  more  anterior 
the  prominent  tuberosity  of  the  scaphoid,  the  space  between  it  and  the  sustentaculum 
being  filled  by  the  inferior  calcaneo-scaphoid  ligament  and  the  tibialis  posticus  tendon  ; 
from  the  tuberosity  the  tendon  may  be  traced  to  the  back  of  the  inner  malleolus  ; 
(/)  the  internal  cuneiform  ;  (g)  the  base  (one  and  a  half  inches  in  front  of  the 
scaphoid  tuberosity),  the  shaft,  and  the  expanded  head  of  the  first  metatarsal  ;  (A) 
the  base  of  the  first  phalanx  with  the  internal  sesamoid  bones  just  beneath  ;  (2)  the 
phalanges. 

On  the  outer  side  are  to  be  felt  :  («)  the  ridge  between  the  outer  and  posterior 
surfaces  of  the  os  calcis  ;  (6)  the  external  tubercle  of  the  os  calcis  ;  (c)  the  peroneal 
tubercle,  three-quarters  of  an  inch  below  and  a  little  in  front  of  the  tip  of  the  external 
malleolus,  lying  between  the  long  and  short  peroneal  tendons  ;  (d)  the  external 
surfaces  of  the  os  calcis  and  (when  the  foot  is  inverted)  the  edge  of  its  anterior 
extremity,  lying  just  above  the  cuboid  ;  (e)  the  prominent  base  of  the  fifth  metatarsal 
(about  two  and  a  half  inches  in  front  of  the  malleolus),  the  shaft,  and  the  expanded 
head  of  that  bone  ;   (/)  the  phalanges. 


438 


HUMAN    ANATOMY. 


On  the  sole  of  the  foot  between  the  tuberosity  of  the  os  calcis  and  the  heads  of 
the  metatarsals  the  bones  cannot  be  felt  distinctly.  The  internal  sesamoids  are 
directly  beneath  the  first  metatarso-phalangeal  articulation. 

On  the  dorsum  of  the  foot,  when  at  right  angles  to  the  leg,  the  bones  of  the 
tarsus  form  a  smooth  rounded  convexity,  with  a  slight  elevation  between  its  middle 
and  inner  thirds,  made  up  of  the  head  of  the  astragalus,  the  scaphoid,  the  middle 
cuneiform,  and  the  second  metatarsal.  With  the  foot  in  full  extension  the  head  of 
the  astragalus  projects,  and  the  extreme  anterior  ends  of  the  ridges  between  the  upper 
and  lateral  articular  surfaces  of  that  bone  can  be  felt.  The  internal  cuneiform  at  the 
summit  of  the  instep  is  easily  recognized.  The  other  cuneiforms,  the  cuboid,  and 
the  metatarsals  can  be  felt  in  thin  feet. 

THE    ANKLE-JOINT. 

The  articulation  is  between  the  bones  of  the  leg  and  those  of  the  foot  as  a 
whole, — i.e. ,  between  the  tibia  and  fibula  above  and  the  astragalus  below.  It  is  a 
hinge-joint,  although  the  mortise  of  the  leg  bones  and  the  top  of  the  astragalus  are 
both  broader  in  front  than  behind.      The  ligaments  are  :  the  capsular,  supporting 

Fig.  456. 


Tibialis  postic 

Groove  for  tibialis  posti< 

Sustentaculum  tali 
Groove  for  flexor  communis  digitor 

Groove  for  flexor  longus  hallucis  \ 


Right  ankle-joint, 


the  synovial  membrane,  and  itself  strengthened  by  very  strong  bands  at  the  sides 
{lateral  ligaments')  and  by  a  weak  one  at  the  back.  There  is  also  a  middle  external 
lateral  ligament  quite  distinct  from  the  capsule. 

The  capsule  (Fig.  456)  arises  from  the  front  of  the  tibia  nearly  one  centi- 
metre above  the  lower  border,  from  the  edge  of  the  anterior  tibiofibular  ligament, 


THE   ANKLE-JOINT. 


439 


from  the  front  of  both  malleoli  at  some  distance  from  the  anterior  border,  and  from 
the  under  side  of  both  malleolar  articular  surfaces.  The  posterior  half  of  the 
superior  origin  is  closer  to  the  articular  border  both  of  the  back  of  the  tibia  and  that 
of  the  inner  malleolus,  but  it  arises  from  the  posterior  border  of  the  outer  malleolus, 
so  as  to  leave  a  deep  pocket  behind  the  outer  articular  surface.  The  inferior  inser- 
tion surrounds  the  articular  surface  on  the  top  and  sides  of  the  astragalus,  being 
close  to  the  cartilage,  except  in  front,  where  the  distance  may  be  one  centimetre, 
and  behind,  where  the  separation  is  less.  This  capsule  consists  in  front  of  longi- 
tudinal fibres  of  no  great  strength,  often  with  fat  between  them.  The  posterior  part 
of  the  capsule  is  extremely  thin. 

Fig.  457- 


Posterior  fasciculus  of  external  lateral 
ligament  (:f- 

Middle  fasciculus  of 
external  lateral  ligament 


Anterior  inferior  tibio- 
fibular ligament 


Anterior  fasciculus  of 
external  lateral 
ligament 


Astragalo-calcaneal 
ligament 


^s  Interosseous  ligament 


Right  ankle-joint,  outer  aspect. 

The  internal  lateral1  or  deltoid  ligament  (Fig.  456)  is  an  extremely  strong 
part  of  the  capsule,  arising  from  the  notch  in  the  posterior  border  and  from  the 
tip  of  the  inner  malleolus,  the  former  portion  being  almost  one  centimetre  thick, 
running  downward  and  backward  to  the  astragalus  below  the  inner  articular  surface 
by  its  deeper  fibres  and  to  the  sustentaculum  tali  by  the  superficial  ones.  The 
great  strength  of  this  part  of  the  ligament  is  appreciated  by  examining  it  after 
division.  The  anterior  part,  thinner  but  still  strong,  runs  to  the  inferior  calcaneo- 
scaphoid  ligament,  and,  joining  the  superior  astragalo-scaphoid  ligament,  may  be 
traced  to  the  scaphoid.      It  has  no  line  of  separation  from  the  front  of  the  capsule. 

The  external  lateral  ligament  (Fig.  457)  is  described  as  consisting  of  three 
bands  which  radiate  from  the  external  malleolus,  although  only  two  are  really  parts  of 

1  Lie  deltoideum. 


44Q  HUMAN   ANATOMY. 

the  capsule.  The  anterior  band1  (Fig.  457)  passes  forward  and  inward  from  the 
front  border  of  the  malleolus  to  the  astragalus  in  front  of  the  lateral  articular  surface. 
It  is  made  tense  in  plantar  flexion.  The  posterior  band'  (Fig.  457) — a  very  strong 
one — arises  from  the  hollow  on  the  inside  of  the  tip  of  the  outer  malleolus  and  runs 
inward  and  backward  to  the  astragalus  behind  the  posterior  outer  angle  of  the 
articular  surface.  It  is  made  tense  in  dorsal  flexion.  With  the  transverse  tibio- 
fibular ligament  it  considerably  strengthens  the  back  of  the  capsule.  The  middle 
band3  (Fig.  457),  more  superficial  and  tending  to  be  free  from  the  capsule,  runs  down- 
ward and  backward  to  a  faint  tubercle  on  the  outer  side  of  the  calcaneum.  It  can 
be  made  fully  tense  by  no  motion  in  the  ankle-joint  alone,  but  restrains  certain 
motions  of  the  astragalus  on  the  calcaneum.  The  capsule  between  these  bands  is 
excessively  thin. 

The  synovial  membrane  lining  the  capsule  is  in  the  main  perfectly  simple, 
following  the  latter  ;  it  presents,  however,  a  prominent  fold  on  the  inside  of  the 
joint  over  the  posterior  band  of  the  external  lateral  ligament,  and  makes  something 
of  a  pouch  above  this,  below  the  transverse  ligament.  It  covers  the  pad  of  fat  be- 
tween the  bones  of  the  leg. 

Movements. — The  articulation  at  the  ankle  is  essentially  a  hinge-joint,  although 
not  a  pure  one,  since  the  fibula  moves  on  the  tibia,  and  the  astragalus,  being  more 
closely  fastened  to  the  fibula,  follows  the  latter  in  its  movements  ;  thus,  the  outer 
end  of  the  transverse  axis  of  rotation  is  subject  to  displacement.  When  the  foot  is 
midway  between  flexion  and  extension,  it  is  possible  in  the  dead  body  to  impart  a 
certain  lateral  motion  to  the  astragalus,  the  lateral  ligaments  being  apparently  not 
tense  ;  but  it  is  highly  improbable  that  this  ever  occurs  during  life,  unless  under 
accidental  circumstances,  for  the  muscles  supplement  the  ligaments.  As  the  foot 
moves  into  dorsal  flexion  the  broadest  part  of  the  astragalus  comes  into  the  broadest 
part  of  the  socket,  forcing  the  malleoli  somewhat  apart.  In  some  cases  it  would 
appear  that  the  fibula  rotates  on  a  longitudinal  axis,  while  the  head  slips  backward, 
but  both  the  degree  and  even  the  nature  of  the  movement  are  uncertain.  The  foot 
is  held  firm  and  immovable  by  the  spring  of  the  bones,  by  the  tension  of  the  pos- 
terior ligament  and  of  the  posterior  and  middle  divisions  of  the  external  lateral  one, 
and  especially  by  the  strong  posterior  part  of  the  internal  lateral.  In  extreme 
plantar  flexion  the  narrowest  part  of  the  astragalus  is  in  the  socket,  of  which  the 
bones  are  in  the  greatest  possible  approximation,  so  that  the  pad  of  fat  between 
them  is  squeezed  into  the  joint  and  rests  against  the  sickle-shaped  facet  of  the 
superior  surface,  except  that  the  hind  end  of  the  latter  is  against  the  posterior  tibio- 
fibular ligament.  The  fold  in  the  posterior  ligament  is  brought  against  the  back  of 
the  bone.  The  anterior  ligament  and  the  anterior  parts  of  the  lateral  ones  are  tense. 
Further  support  is  gained  by  the  back  of  the  astragalus  below  the  articular  facet 
resting  against  the  back  of  the  tibia  so  as  to  lock  the  joint.  The  front  bands  of  both 
outer  and  inner  lateral  ligaments  are  tense.  The  action  of  the  numerous  muscles 
crossing  the  ankle  is,  of  course,  greatly  to  strengthen  it  and  to  prevent  any  giving 
between  the  bones  when  the  ligaments  are  not  stretched  to  the  utmost.  Moreover, 
the  elasticity  of  the  fibula  is  an  important  element  in  the  mechanics  of  the  ankle- 
joint,  and  one  that  makes  it  impossible  to  contrive  a  model  that  will  represent  the 
conditions  actually  existing. 

THE  ARTICULATIONS   OF  THE   FOOT. 

As  has  been  shown,  the  bones  of  the  foot  are  so  arranged  (Fig.  431)  that  the 
astragalus,  placed  on  the  calcaneum,  carries  with  it  the  three  inner  toes,  while  the  two 
outer,  resting  on  the  cuboid,  are  more  under  the  influence  of  the  movements  of  the 
calcaneum.  It  is,  however,  possible  for  the  scaphoid  and  cuboid  to  move  together 
on  the  two  proximal  bones.  The  essential  joints  for  the  movements  of  the  foot, 
besides  the  ankle-joint,  are  those  between  the  calcaneum  and  astragalus  and  those 
between  the  astragalus  and  scaphoid  and  the  calcaneu?n  and  ciiboid  respectively. 
The  joints  between  the  smaller  bones  at  the  front  of  the  tarsus  are  mechanically  un- 
important, being  chiefly  to  break  shocks  and  to  allow  an  indefinite  giving  in  the 
arch  of  the  foot.      As  certain  ligaments  are  concerned  in  the  protection  of  several 

1  Lig.  taloiibulare  anterius.     2Lig.  talcGbularc  posterius.     3  Lig.  calcaneofibulare. 


THE   INTEROSSEOUS   LIGAMENTS. 


441 


joints,  it  is  best  first  to  study  the  ligaments  of  the  foot  all  together,  beginning  with 
such  as  are  essential  parts  of  the  framework  ;  then  to  examine  the  joints  seriatim; 
and,  finally,  to  discuss  the  motions  of  the  foot  as  a  whole.     In  the  case  of  the  smaller 

Fig.  458. 


Posterior  tibio-fibul 
ligament 


Cuneiform  bones 

Intercuneiform 
tarso- 
metatarsal 
ligaments 


Obliq 


through  the  right  foot. 


ligaments  it  is  our  object  to  avoid  pedantic  attention  to  useless  details.      We  shall 
consider  first  the  interosseous  ligaments,  then  the  dorsal,  and  lastly  the  plantar  ones. 


THE   INTEROSSEOUS   LIGAMENTS. 

The  astragalo-calcaneal  (Fig.  457)  is  a  thick  layer  of  fibres  filling  the 
groove  between  the  two  adjacent  articular  surfaces  of  each  bone.  At  the  outer 
part,  where  the  groove  widens,  it  tends  to  divide  into  two  layers.  A  considerable 
quantity  of  fat  is  found  in  its  meshes.  Each  side  of  it  is  lined  by  the  synovial  mem- 
brane of  the  joints  which  it  separates.  An  occasional  superficial  band — the  external 
astragalo-calcaneal  (Fig.  457) — may  be  continuous  with  this  ligament. 

The  calcaneo-cubo-scaphoid  (Fig.  460)  (seen  by  removing  the  astragalus 
and  the  synovial  membrane  covering  it)  is  a  series  of  short,  strong  fibres,  collected 
into  bundles,  joining  the  front  of  the  calcaneum  with  the  outer  border  of  the  scaph- 
oid, and  by  a  weaker  division  with  the  inner  side  of  the  cuboid.  It  forms  the  outer 
part  of  the  capsule  for  the  head  of  the  astragalus,  reaching  to  the  dorsum.  This 
capsule  is  completed  by  the  superior  and  inferior  calcaneo-scaphoid  ligaments. 


442 


HUMAN    ANATOMY. 


The  cubo-scaphoid  (Fig.  458)  passes  crosswise  between  these  bones,  close 
to  the  last  ligament.  Its  size  varies,  being  in  inverse  ratio  to  the  articular  facet 
between  the  bones  it  unites. 

The  cubo-cuneiform  (Fig.  458)  is  a  strong  band  connecting  the  non-articular 
surfaces  of  the  cuboid  and  the  outer  cuneiform  at  their  distal  ends  from  the  plantar 
to  the  dorsal  border. 

The  intercuneiform  (Fig.  458)  are  strong  ligaments  connecting  the  distal 
non-articular  surfaces  of  these  bones.  That  from  the  inner  side  of  the  middle 
cuneiform  does  not  completely  separate  the  joints  before  and  behind  it.  The 
arrangement  between  the  middle  and  outer  cuneiforms  is  variable  in  this  respect. 

The  interosseous  tarso-metatarsal  ligaments  (Fig.  458)  are  an  inner  and 
an  outer,  with  an  occasional  middle  one.  The  inner,  a  strong  band  arising  from 
the  outer  side  of  the  internal  cuneiform  where  it  overlaps  the  second  metatarsal,  runs 
obliquely  outward  and  forward,  most  of  its  fibres  going  to  that  bone,  but  a  few  to  the 

Fig.  459. 


Astragalo-calcaneal  ligament 


Articular  surface  for  cuboid 


Articular  surfaces  for  astragalus 


Sustentaculum 
The  inner  part  of  the  right  astragalus  has  been  removed. 

outer  side  of  the  first  metatarsal.  The  outer  interosseous  ligament  arises  from  the 
adjacent  sides  of  the  external  cuneiform  and  the  cuboid,  mingling  with  the  fibres  of 
the  ligament  already  described  as  passing  between  them,  and  runs  forward  to  the 
inner  side  of  the  base  of  the  fourth  metatarsal,  to  the  rough  surface  proximal  to  the 
facet,  and  to  the  plantar  half  of  the  outer  side  of  the  third.  The  middle  interosseous 
ligament  is  inconstant  and  small.  It  runs  from  the  outer  cuneiform  to  the  second 
metatarsal. 

The  interosseous  intermetatarsal  ligaments  (Fig.  458)  are  strong 
bands,  best  seen  on  section,  between  the  bases  of  the  four  outer  bones.  The  few 
fibres  between  the  bases  of  the  first  and  second  do  not  deserve  the  name. 

The  distal  intermetatarsal  ligament  is  not  an  interosseous  one,  properly 
speaking,  but  is  mentioned  here  as  it  is  an  important  piece  of  the  general  framework. 
It  is  a  fibrous  band  connecting  the  glenoid  cartilages  at  the  metacarpo-phalangeal 
joints  precisely  as  in  the  hand,  except  that  it  goes  to  the  great  toe  as  well  as  to  the 
others. 

THE   DORSAL   LIGAMENTS. 

The  dorsal  ligaments  of  the  tarsus  are  a  number  of  bands  of  varying  degrees 
of  distinctness,  all  of  which,  in  part  at  least,  assist  in  forming  the  capsules  of  the 
various  joints,  although  they  may  extend  farther. 

The  superior  astragalo-scaphoid  (Fig.  460)  might  be  divided  into  an  inner 
part,  composed  of  fibres  running  from  the  inner  side  of  the  former  bone  to  the  inner 
and  dorsal  aspect  of  the  latter,  and  into  a  dorsal  part,  running  from  the  margin  of 
the  head  of  the  astragalus  forward,  with  an  inclination  either  inward  or  outward. 


THE    DORSAL    LIGAMENTS. 


443 


A  series  of  well-marked  but  not  strong  ligaments  radiate  forward  and  outward 
from  the  scaphoid  (Fig.  460):  three  dorsal  scapho-cuneiform  and  one  scapho- 
cuboid  ligament. 

The  dorsal  calcaneo-cuboid  ligament  (Fig.  460)  is  a  thin  band  of  little 
note.  The  interosseous  calcaneo-cubo-scaphoid  reaches  the  dorsum  by  the  part 
going  to  the  scaphoid.  The  ligament  just  mentioned  is  sometimes  continuous  with 
it  at  its  origin,  and  the  two  have  been  called  by  French  anatomists  the  Y-ligament, 
to  which  much  consequence  has  been  ascribed.  The  interosseous  ligament  is  the 
important  one. 

Fig.  460.  ■ 


Dorsal  tarso-metatarsal 
ligaments 


Dorsal  scapho-cuneiform 
ligaments 


Astragalo-scaphoid 
ligament 

Scaphoid 

Calcaneo-cubo-scaphoid 
ligament 

Inferior  calcaneo- 
scaphoid  ligament 

Fibro-cartilage 


Interosseous  astragal 
calcaneal  ligament 


Dorsal  intermetatarsal 
ligament 


Peroneus  tertius 


Superior  scapho- 
cuboid  ligament 


Astragalo-calcaneal  ligament 


Upper  aspect  of  the  right  tarsus,  the  astragalus  having  been  removed. 


The  dorsal  tarso-metatarsal  ligaments  (Fig.  460)  are  simple  for  the  first 
metatarsal,  being  bands  running  from  the  internal  cuneiform.  For  the  others  they 
are  more  irregular,  and  there  is  an  interlacing  with  transverse  dorsal  ligaments 
between  the  metatarsals  connecting    the    outer  four  bones  and  the  second  to  the 


444 


HUMAN   ANATOMY. 


internal  cuneiform.  The  bands  over  the  cuboid  and  the  two  outer  metatarsals  are 
closely  interwoven  with  the  tendon  of  the  peroneus  tertius  when  that  muscle  is 
present.  These  ligaments  constitute  an  interrupted  series  of  bands  converging  for- 
ward from  either  side  of  the  foot. 

The  dorsal  ligaments  are  weak,  and  need  the  help  of  the  extensor  muscles  of 
the  toes  to  resist  the  strain  of  the  strong  muscles  of  the  sole. 

THE    PLANTAR    LIGAMENTS. 

The  plantar  ligaments  are  of  three  kinds  :   (#)  those  passing  from  one  bone  to 
the  next,  and  therefore  nothing  but  thickenings  of  the  capsule  ;   {b)  those  passing 


Fig.  461. 


Intermetatarsal  ligament 


Tendon  of  peroneus 
longus 


Long  plantar  ligament 
Peroneal  spine 


— Tendon  of 
tibialis 
posticus 


Tendo  Achillis 
Right  tarsus,  inferior  aspect. 


from  one  bone  to  one  or  several  distant  ones  ;   (V)  and  those  continuous  with  the 
tendon  of  the  tibialis  posticus,  which  is  very  strong  and  has  a  far-reaching  action. 


THE   CALCANEO-ASTRAGALOID   JOINT.  445 

The  plantar  calcaneo-cuboid  ligaments  are  the  long  and  the  short.  The 
former,  known  as  the  long  plantar  ligament  (Fig.  461),  arises  from  the  perios- 
teum of  the  under  side  of  the  calcaneum  in  front  of  the  posterior  tubercles,  and  runs 
forward  as  a  flat  band,  at  first  some  two  centimetres  broad,  to  the  whole  length  of 
the  ridge  of  the  cuboid,  except  its  inner  end.  It  passes  beyond  this  to  the  bases  of 
the  outer  three  metatarsals  in  a  somewhat  broken-  and  weak  layer  of  fibres  forming 
a  bridge  over  the  groove  for  the  tendon  of  the  peroneus  longus.  The  short 
plantar  ligament  (Fig.  461)  is  in  part  hidden  by  the  longer,  but  is  seen  at  its 
inner  side.  It  arises  from  the  anterior  tubercle  of  the  calcaneum  and  the  bone  in 
front  of  it  and  goes  to  the  under  side  of  the  cuboid,  between  the  posterior  border 
and  the  ridge.      The  inner  fibres  run  obliquely  forward  and  inward. 

The  inferior  calcaneo-scaphoid  ligament  (Fig.  460)  fills  the  gap  on  the 
plantar  side  of  the  foot  between  the  sustentaculum  and  the  scaphoid.  It  is  more  or 
less  divisible  into  two  parts,  which  have  a  common  origin  from  the  anterior  border 
of  the  sustentaculum.  The  inner  and  stronger  part  runs  obliquely  forward  and 
inward  to  the  lower  border  of  the  scaphoid  near  the  tuberosity.  The  outer  part 
runs  more  nearly  straight  forward  to  the  outer  part  of  the  same  border.  There  is 
generally  a  small  interspace  between  them.  The  upper  surface  of  the  inner  portion 
of  the  ligament  is  covered  by  a  coating  of  articular  cartilage  completing  the  joint 
for  the  head  of  the  astragalus.  This  cartilage  is  usually  wanting  at  the  anterior 
outer  angle  of  the  space  between  the  bones.  Beneath  and  to  the  inner  side  of  the 
ligament  runs  the  tendon  of  the  tibialis  posticus.  On  the  inner  side  of  the  foot 
this  ligament  is  continuous  with  a  part  of  the  superior  astragalo-scaphoid  and  with 
the  termination  of  the  deltoid  ligament. 

The  inferior  scapho-cuboid  ligament  (Fig.  461)  is  an  insignificant  group 
of  fibres. 

The  inferior  scapho-cuneiform  ligaments  (Fig.  461)  are  three  distinct 
bands,  of  which  the  inner  is  the  broadest,  the  others  being  more  cord-like,  diverging 
from  the  under  side  of  the  scaphoid  to  the  three  cuneiform  bones.  They  are  all 
continuous  with  the  fibres  of  the  tendon  of  the  tibialis  posticus. 

On  the  plantar  side  there  is  a  very  irregular  arrangement  of  fibres  passing  from 
the  tarsus  to  the  metatarsus  and  a  considerable  system  of  oblique  fibres  running 
inward  and  forward  from  the  cuboid  and  the  fifth  metatarsal  to  the  external  cunei- 
form and  to  the  bases  of  several  metatarsal  bones. 

The  joints  of  the  phalanges  are  on  the  same  plan  as  in  the  hand  and  require  no 
further  description.  The  sesamoid  bones  at  the  tarso- metatarsal  joint  of  the  great 
toe  are  very  large  and  connected  by  the  glenoid  ligament. 

THE   POSTERIOR   CALCANEO-ASTRAGALOID   JOINT. 

This  joint  (Fig.  460)  is  separated  from  the  anterior  by  the  interosseous  ligament, 
which  is  continuous  with  the  capsule  that  completely  surrounds  the  articulation. 
This  capsule  is  in  most  parts  weak,  but  is  strengthened  behind  by  the  posterior 
astragalo-calcaneal  ligament. 

THE  ANTERIOR   CALCANEO-SCAPHO-ASTRAGALOID   JOINT. 

This  articulation  (Fig.  460)  may  be  called  a  ball-and-socket  joint,  although  the 
head  of  the  astragalus  is  not  a  part  of  the  surface  of  a  sphere.  The  articular  surfaces 
have  been  described  with  the  bones.  The  socket  is  made  by  the  anterior  articular 
facet  or  facets  of  the  calcaneum,  by  the  posterior  facet  of  the  scaphoid,  by  the  inter- 
osseous ligament  joining  these  externally,  and  by  the  inferior  calcaneo-scaphoid  liga- 
ment, with  its  cartilaginous  plate,  which  fuses  on  the  inner  side  with  the  superior 
calcaneo-scaphoid  and  the  deltoid  ligament,  all  of  which  make  a  capsule  around  the 
head,  completed  by  the  interosseous  astragalo-calcaneal  ligament.  A  fold  of  syno- 
vial membrane,1  variously  developed,  which  may  contain  fibrous  tissue,  is  generally 
found  on  the  floor  of  this  socket,  extending  back  from  the  interruption  of  the  anterior 
facet  on  the  calcaneum,  or  from  a  corresponding  place  when  it  is  simple,  to  the  inferior 

1  E.  Barclay  Smith  :  Journal  of  Anatomy  and  Physiology,  vol.  xxx.,  1896. 


446  HUMAN   ANATOMY. 

border  of  the  head  of  the  astragalus.      The  tendon  of  the  tibialis  posticus  directly 
beneath  and  internal  to  the  joint  adds  to  its  security. 

The  motions  of  the  two  subastragaloid  joints  must,  of  course,  be  considered 
together.  They  are  resolved  into  turning  on  an  oblique  axis  running  through  the 
interosseous  ligament,  somewhat  internal  to  its  middle,  downward  with  something 
of  a  backward  and  inward  inclination.  Rotating  on  this,  the  posterior  concave 
articular  surface  of  the  astragalus  twists  with  a  screw  motion  on  the  opposed  surface 
of  the  calcaneum.  As  the  back  of  the  astragalus  moves  upward  and  outward,  the 
head  passes  downward  and  inward  in  the  socket.  This  movement  is  stopped  by  the 
front  of  the  posterior  articular  surface  of  the  astragalus  catching  in  the  hollow  at  the 
front  of  the  convex  surface  of  the  calcaneum  that  it  plays  on.  This  is  a  most  efficient 
device  for  locking  the  joint.  The  opposite  motion  is  stopped  by  the  inner  posterior 
tubercle  of  the  astragalus  striking  the  back  of  the  sustentaculum  tali.  In  the  anterior 
joint  there  is  also  to  be  considered  the  motion  between  the  head  of  the  astragalus 
and  the  scaphoid.  The  strong  interosseous  and  inferior  calcaneo-scaphoid  ligaments 
do  not  allow  much  displacement  of  the  scaphoid,  but  it  seems  that  it  can  travel  for 
a  short  distance  up  or  down  and  in  or  out,  and  can  therefore  be  slightly  circum- 
ducted ;  the  chief  motion,  however,  is  one  of  rotation  on  the  above-mentioned  axis 
through  the  astragalus.  Variations  in  the  slant  of  the  posterior  articular  surface  of 
the  os  calcis  must,  of  course,  modify  the  position  of  the  axis. 

THE   CALCANEO-CUBOID   JOINT. 

The  calcaneo-cuboid  joint  (Fig.  458),  surrounded  by  a  capsule  the  inner  side 
of  which  is  formed  by  the  interosseous  calcaneo-cubo-scaphoid  ligament,  is  a  modi- 
fication of  the  saddle-joint.  Apart  from  some  indefinite  gliding,  the  nature  and 
amount  of  which  vary  in  different  feet,  the  chief  motion  is  rotation  on  an  approxi- 
mately antero-posterior  axis  running  through  the  joint.  It  might,  perhaps,  be  more 
accurately  defined  as  a  screw  motion.  This  movement,  however,  is  very  limited. 
Rotation  of  the  cuboid  in  a  direction  that  would  raise  its  outer  border  is  checked  by 
the  interosseous  and  dorsal  ligaments  at  its  inner  side.  Rotation  in  the  opposite 
direction,  if  not  sooner  arrested  by  the  ligaments,  is  effectually  checked  by  the 
plantar  tubercle  of  the  cuboid  catching  on  the  overhanging  lip  of  the  articular  surface 
of  the  os  calcis,  thus  locking  the  joint. 

THE   SCAPHO-CUBO-CUNEIFORM   JOINT. 

This  articulation  is  a  synovial  cavity  bounded  behind  by  the  scaphoid,  extending 
forward  to  varying  distances  between  the  different  bones.  Thus,  between  the  first 
and  second  cuneiforms  it  communicates  with  the  joint  of  the  second  metatarsal,  it  is 
usually  bounded  by  the  interosseous  ligament  between  the  second  and  third  meta- 
tarsals, and  finally  by  that  between  the  latter  with  the  cuboid.  The  motions  are 
very  slight  in  each  joint  and  of  no  great  importance  when  combined.  There  is  next 
to  no  motion  of  the  internal  cuneiform  of  the  scaphoid  and  very  little  of  the  second. 
The  external  moves  more  freely,  sliding  slightly  up  and  down.  The  interosseous 
ligaments  resist  the  undue  spreading  of  the  transverse  arch  of  the  foot. 

THE  TARSO-METATARSAL   JOINTS. 

That  of  the  first  metatarsal  bone  (Fig.  458)  is  an  independent  joint  with  its 
own  capsule,  the  interosseous  ligament  between  the  internal  cuneiform  and  the 
second  metatarsal  shutting  it  off.  The  front  of  the  cuneiform  is  convex  from  side  to 
side  and  about  plane  from  above  down.  Rarely  it  is  subdivided  into  an  upper  and  a 
lower  compartment.  It  may  be  prolonged  onto  the  side  of  the  second  metatarsal. 
An  articular  facet  coated  with  cartilage  is  common  on  the  outer  side  of  the  first  meta- 
tarsal, but  that  on  the  second  is  indistinct  or  wanting.  It  seems  that  this  is  simply 
a  bursa  in  most  cases  just  beyond  the  joint,  but  they  sometimes  communicate.  Lat- 
eral motion  with  this  metatarsal  is  the  most  free,  and  there  is  a  certain  sliding  up 
and  down. 


THE    METATARSAL   JOINTS.  447 

The  second  tarso-metatarsal  joint  opens  at  the  inner  side  into  the  great 
tarsal  joint,  and  usually  with  that  of  the  external  cuneiform  and  third  metatarsal. 
The  motions  of    these   joints  are  slight  and 
indefinite.  FlG-  462. 

The  fourth  and  fifth  tarso-metatarsal  Head  of  f,rst  metatarsal 

joints,  between  the  cuboid  and  the  two  outer 
metatarsal  bones,  are  nearly  or  quite  separated 
from  the  preceding  by  the  interosseous  liga- 
ment from  between  the  outer  cuneiform  and 
the  cuboid  to  the  third  and  fourth  metatarsals  ;  internal- 

practically  they  form  a  distinct  joint.  The  sesamoid  bone  \  £rr-v 
motion  is  much  more  free  than  in  the  others.  Tiong°"haiiuds  cit"^ 
The  fourth  metatarsal  bone  plays  on  the  third 
by  a  facet  distal  to  the  interosseous  ligament 
just  mentioned.  The  fifth  plays  still  more 
freely  both  on  the  fourth  and  on  the  cuboid.  The  motion  is  of  a  nature  to  permit 
the  drawing  of  the  outer  side  of  the  foot  downward  and  inward  so  as  to  deepen  the 
hollow  of  the  sole.  It  also  allows  the  outer  metatarsals  to  be  displaced  dorsally 
when  the  transverse  arch  is  flattened. 

THE    METATARSO-PHALANGEAL   JOINTS. 

These  articulations  in  the  foot  are  similar  to  the  corresponding  ones  of  the  hand, 
the  capsule  including  the  glenoid  and  lateral  ligaments ;  the  latter  arise  from  both 
the  tubercles  and  the  depressions  on  the  heads  of  the  metatarsals.  That  of  the  great 
toe  is  large  and  distinguished  by  the  large  size  of  the  sesamoid  bones,  which  are 
interposed  between  the  head  of  the  metatarsal  and  the  ground.  As  in  the  hand,  there 
is  no  glenoid  ligament  in  this  joint.  The  transverse  metatarsal  ligament  differs  from 
that  of  the  hand  in  connecting  all  the  toes.  The  motions  correspond  to  those  of 
the  hand,  but  the  range  of  dorsal  extension  is  greater.  Lateral  motion  is  possible 
only  when  the  toes  are  nearly  straight. 

The  structure  and  motions  of  the  interphalangeal  joints  are  as  in  the  hand. 

SYNOVIAL  CAVITIES. 

The  following  synovial  cavities  are  found  (Figs.  458,  463).  (1)  That  of  the 
ankle-joint  proper  ;  (2)  the  posterior  calcaneo-astragaloid ;  (3)  the  anterior  calcaneo- 
astragaloid. completed  by  the  scaphoid;  (4)  the  calcaneocuboid;  (5)  the  scapho- 
cuneiform  cuboid,  the  great  tarsal  cavity  which  communicates  with  the  joints  at  the 
bases  of  the  second  and  third  metatarsals  by  a  passage  at  the  inner  side  of  the  middle 
cuneiform  and  sometimes  by  one  on  its  outer  side.  This  may  also  open  into  the 
preceding  synovial  cavity  ;  (6)  the  joint  between  the  internal  cuneiform  and  the 
first  metatarsal;   (7)  that  of  the  cuboid  and  the  outer  two  metatarsals. 

The  arrangement  of  the  synovial  sacs  about  the  bases  of  the  second  and  third 
metatarsals  is  variable. 

THE   FOOT   AS   A  WHOLE. 

The  foot  is  a  vault  which  may  be  considered  as  composed  of  an  indefinite  number 
of  arches  diverging  from  the  internal  tuberosity  of  the  calcaneum  and  ending  in 
front  at  the  heads  of  the  metatarsals.  The  highest  arch  is  that  in  the  line  of  the 
great  toe,  a  fact  in  some  degree  due  to  the  sesamoid  bones  which  are  between  the  head 
of  the  first  metatarsal  and  the  ground.  The  arch  at  the  outer  side  of  the  foot  is  the 
lowest.  It  is  clear  from  this  conception  that  transverse  sections  of  the  foot  must 
also  show  an  arched  structure  the  details  of  which  must  vary  with  the  line  of  section. 
The  shape  of  the  three  cuneiforms  is  an  essential  element  in  this  construction.  _  This 
vault  is,  however,  not  rigid,  but  elastic  and  capable  of  considerable  modification  of 
shape  under  varying  pressure. 

In  the  motions  of  the  foot  the  essential  joints  below  the  ankle  are  the  subastraga- 
loid  and  those  between  the  astragalus  and  the  scaphoid  and  the  calcaneum  and  the 
cuboid. 


448  HUMAN    ANATOMY. 

The  bones  in  front  of  the  astragalus  and  os  calcis  move  very  much  as  a  unit, 
although  there  may  be  some  play  between  the  scaphoid  and  cuboid  and  between  the 
latter  and  the  fifth  metatarsal.  The  astragalus,  having  no  muscle  inserted  into  it,  is 
acted  on  in  the  ankle-joint  by  the  other  bones,  as  is  the  first  row  of  the  carpus,  its 
motions  depending  on  the  pressure  it  receives.  When  the  foot  is  in  extreme  dorsal 
flexion,  all  the  joints  of  the  tarsus  are  locked  and  no  motion  is  possible.     Starting 

Fig.  463. 


Astragalus 

Calcaneo- 

astragaloid 

ligament 


Internal  sesamoid  bone 


Longitudinal  section  through  right  foot  i 


Sustentaculum 
Inferior  calcaneo-scaphoid  ligament 
axis  of  first  metatarsal  bone. 


from  a  position  of  moderate  flexion,  the  motions  (excepting  those  of  simple  flexion 
and  extension  which  occur  in  the  ankle)  are  combinations  of  adduction  and  abduction, 
inversion  and  eversion.  Adduction  is  generally  combined  with  inversion,  and  these 
two  motions  are  more  extensive  than  the  opposite  ones.  They  practically  never 
occur  pure.  Inversion  and  eversion  occur  chiefly  in  the  joints  below  the  astragalus, 
but  in  part  in  the  mid-tarsal  joint.  Adduction  and  abduction  are  perhaps  about 
equally  divided  between  the  two  ;  but  if  the  calcaneum  be  held  by  one  hand  and  the 


Fig.  464. 

Middle  cuneifo 


Fig.  465. 


Middle  cuneiform 


External  cuneiform 


Interosseous  ligament 


Interosseous  ligaments 


Transverse  section  thr 


Oblique  section  thr 


front  of  the  foot  moved  by  the  other,  it  is  clear  that  the  mid-tarsal  joint  allows  much 
more  abduction  and  adduction  than  eversion  and  inversion,  which  therefore  occur 
chiefly  between  the  calcaneum  and  astragalus. 

In  the  ordinary  position  of  supporting  the  body  it  appears  that  the  essential  arch 
is  through  the  calcaneum,  the  cuboid,  the  external  cuneiform,  joined  to  the  latter  by 
a  firm   interosseous  ligament,   and  the  third  metatarsal.1      This  can  be  proved  by 

1  H.  v.  Meyer :  Der  menschliche  Fuss. 


THE   FOOT   AS   A   WHOLE. 


449 


Fig.  466. 


removing  the  first  and  fifth  metatarsals  with  their  phalanges  and  the  first  cuneiform 
bone,  without  impairing  the  stability  of  the  foot.  The  fourth  metatarsal  may  next  be 
taken  away  without  trouble.  If  the  second  with  its  cuneiform  be  detached  with  care, 
the  arch  is  still  reasonably  firm.  It  is  possible  to  preserve  the  arch  after  taking  out 
the  astragalus,  and  then  removing  the  scaphoid.  Although  the  arch  still  stands,  it 
will  bear  little  weight,  the  third  cuneiform  being  inadequately  supported  behind  ;  but 
with  the  scaphoid  and  astragalus  retained  the  arch  is  a  good  one.  The  arches 
depend  very  much  for  their  stability  on  the  action  of  the  peroneus  longus  and  the 
tibialis  posticus,  which  pull  against  each  other  from  opposite  sides.  The  former  is 
efficient  in  maintaining  the  transverse  arch,  the  latter  in  maintaining  both  the  trans- 
verse and  the  antero-posterior.  To  these  should  be  added  the  plantar  fascia  and 
the  muscles  to  the  toes  arising  from  the  calcaneum.  When  in  life  the  weight  is 
equally  divided  between  the  feet,  the  part  in  contact  with  the  ground  is  the  heel,  the 
outer  border  of  the  foot,  the  region  of  the  heads  of  the  metatarsals,  and,  separated 
from  the  rest,  the  balls  of  the. toes,  which  bear  no  weight.  The  outer  border  also,  as 
a  rule,  is  doing  no  work  and  often  does  not  even  touch  the  ground,  It  is  easy  to 
pass  a  thin  spatula  under  the  head  of  the  fifth  metatarsal,  and  usually  not  hard  to 
pass  it  under  that  of  the  first,  thus  showing  that  in  this  position  they  are  not  essential 
parts  of  the  arch.  When  the  whole  or  nearly  the  whole  weight  is  transferred  to 
one  foot  the  following  changes  occur.  The  head  of  the  astragalus  turns  inward,  at 
the  same  time  sinking  under  the  weight  of  the  body  so  as  to  make  a  prominence  at 
the  inner  side  of  the  foot.  The  internal  malleolus  follows  this  movement.  The 
outer  malleolus  advances,  but  does  not  descend.  Thus  the  relation  of  the  front  part 
of  the  foot  to  the  posterior  is  one  of  abduction  and  eversion.1  The  weight-bearing 
region  changes  both  its  shape  and  position.  The  line  at  the 
outer  part  of  the  heel  is  the  only  part  that  remains  stationary. 
The  surface  of  pressure  (Fig.  466)  is  broader  at  the  heel  and 
still  more  so  at  the  heads  of  the  metatarsals.  The  connecting 
strip  moves  inward,  but  becomes  no  broader  ;  sometimes  it 
even  narrows.  The  chief  agent  in  resisting  this  change, 
which  is  greater  after  fatigue,  is  the  tibialis  posticus,  which 
opposes  the  inner  turn  of  the  head  of  the  astragalus  which 
precedes  its  descent.  When  this  is  inadequate,  the  change 
of  position  is  exaggerated  and  the  foot  breaks  down. 

As  the  heel  is  raised,  under  normal  conditions,  the 
weight  is  transmitted  through  the  astragalus  chiefly  to  the 
bones  and  soft  parts  forming  the  socket  for  its  head,  the 
calcaneum  receiving  little  of  it.  The  strain  comes  chiefly 
on  the  ligaments  securing  the  scaphoid,  for  that  bone  is  most 
directly  in  the  line  of  pressure,  which  it  transmits  through 
the  front  of  the  tarsus  to  the  heads  of  the  metatarsals,  chiefly 
to  the  first  ;  but  in  this  last  respect  individuals  vary.  Usu- 
ally the  region  of  the  heads  of  the  metatarsals  narrows,  the 
weight  being  borne  chiefly  at  the  inner  side,  but  in  some 
cases  by  all  the  heads.  When  the  weight  is  borne  by  the 
toes,  the  foot  being  inverted  and  abducted,  the  locking  by 
the  catching  of  the  plantar  tubercle  of  the  cuboid  in  the  os  calcis  is  an  important 
factor  of  stability. 

Surface  Anatomy. — The  malleoli  are  easily  felt,  the  inner  being  square,  the 
outer  longer  and  more  pointed  ;  the  latter  is  the  lower  and  the  more  posterior.  The 
ankle-joint  is,  therefore,  more  easily  opened  from  the  inner  side.  The  front  lower 
border  of  the  tibia  is  hard  to  examine  on  account  of  the  extensor  tendons  ;  the  line 
of  the  joint  is  from  one  to  two  centimetres  above  the  tip  of  the  inner  malleolus,  run- 
ning transversely.  The  general  features  of  the  os  calcis  can  be  made  out.  The  sus- 
tentaculum is  distinct  and  the  peroneal  spine  can  be  recognized.  Along  the  inner 
side,  the  head  of  the  astragalus  can  be  felt  at  the  dorsum  where  it  enters  the  hollow 
of  the  scaphoid.     The  tubercle  of  the  latter  is  lower  down  and  farther  forward.     The 


Surface  of  pressure  c 
sole  of  foot  as  seen  throug 
a  glass  plate  supporting  tr 
body. 


1  Lovett :  New  York  Medical  Journal,  1896. 
29 


45Q  HUMAN   ANATOMY. 

first  cuneiform  and  the  joint  behind  and  before  it,  the  first  metatarsal  and  perhaps 
the  inner  sesamoid  come  in  order.  A  very  moderate  swelling  obscures  most  of  these 
points.  On  the  outer  side  the  joint  between  the  calcaneum  and  the  cuboid  can  be 
found.  A  little  in  front  of  this  is  the  tuberosity  of  the  fifth  metatarsal,  the  only  dis- 
tinct landmark  on  the  outer  side.  The  general  dorsal  outline  of  the  tarsal  bones  is 
to  be  recognized,  but  only  under  favorable  circumstances.  The  dorsal  surfaces  of 
the  metatarsals  are  distinct.  The  joint  between  the  astragalus  and  calcaneum  behind 
and  the  scaphoid  and  cuboid  in  front  is  sinuous  :  convex  forward  at  the  inner  part 
and  tending  to  concavity  at  the  outer,  the  two  ends  of  the  line  being  nearly  in  the 
same  transverse  plane.  The  tarso- metatarsal  joint  is  very  oblique,  running  from 
within  outward  and  backward.  It  is  repeatedly  irregular,  the  chief  interruption  of 
the  direction  being  at  the  mortise  of  the  second  metatarsal  between  the  inner  and 
outer  cuneiforms.  The  joints  of  the  first  phalanges  with  the  metatarsal  bones  are 
about  2.5  centimetres  behind  the  web  of  the  toes. 

PRACTICAL   CONSIDERATIONS. 

The  Ankle-joint. — Uncomplicated  dislocations,  inward  or  outward,  are  almost 
unknown  because  of  (a)  the  close  lateral  approximation  of  the  malleoli,  which  are  held 
to  the  sides  of  the  astragalus  by  the  strong  inferior  tibio-fibular  ligaments  ;  (6)  the 
further  support  of  the  lateral  ligaments,  especially  the  inner  ;  and,  (t)  to  a  very 
minor  extent,  the  wavy  outline  of  the  upper  surface  of  the  astragalus,  which  slightly 
resists  sidewise  movements. 

Lateral  dislocations  are  accordingly  almost  always  associated  with  fracture  of 
one  or  other  of  the  bones  of  the  leg,  and  have  been  sufficiently  described  in  that 
connection  (page  395).  They  are  incomplete.  In  addition  to  the  inward  or  out- 
ward movement  of  the  astragalus  it  undergoes  a  partial  rotation  on  an  antero-posterior 
axis,  so  that  its  tibial  surface  points  obliquely  upward  in  a  direction  opposite  to  that 
of  the  displacement. 

Reduction  is  easy  and  the  after-treatment  is  that  appropriate  to  the  fracture. 

Backward  dislocations  of  the  astragalus — i.e. ,  of  the  foot  (which  are  etiologically 
forward  dislocations  of  the  tibia) — are  resisted  by  (a)  the  shape  of  the  upper  articular 
surface  of  the  astragalus,  which  is  about  one-fourth  narrower  behind  than  in  front  ; 
(b)  the  corresponding  shape  of  the  irregular  arch  in  which  the  astragalus  rests  ;  (<r) 
the  outward  slope  from  behind  forward  of  the  lateral  facets  of  the  astragalus  ;  (d)  the 
lower  level  of  the  posterior  as  compared  with  the  anterior  articular  edge  of  the  tibia  ; 
and  (e)  the  reinforcement  of  the  posterior  ligament  by  the  tendon  of  the  flexor  longus 
hallucis.  If  it  were  not  for  these  provisions,  the  frequency  with  which,  in  alighting  on 
the  ground  in  running  or  jumping,  the  foot  is  fixed  and  the  tibia  is  driven  forward 
against  the  weak  anterior  ligament  would  render  these  luxations  much  more  common. 
An  even  more  powerful  leverage  is  produced  in  the  same  direction  when,  the  foot 
being  fixed,  a  fall  backward  thrusts  the  lower  end  of  the  tibia  forward.  As  it  is,  the 
backward  far  exceed  in  frequency  the  forward  luxations  because,  although  the  above- 
mentioned  anatomical  factors  favor  the  latter,  the  weight  of  the  body  is  scarcely 
ever  brought  upon  the  limb  in  such  a  direction  and  with  such  force  as  to  induce 
them  (Humphry). 

In  backward  luxation  the  tibia  rests  upon  the  scaphoid  and  cuneiform,  the- 
anterior  ligament  is  ruptured,  and  the  posterior  and  lateral  ligaments  are  lacerated. 
The  foot  is  shortened  from  the  lower  anterior  edge  of  the  tibia  to  the  web  of  the  great 
toe,  the  heel  is  lengthened,  the  tendo  Achillis  describes  a  marked  curve  backward, 
and  the  depressions  on  either  side  of  it  are  exaggerated. 

Sprains  of  the  ankle,  on  account  of  its  position,  where,  in  lateral  twists,  it  can 
receive  through  the  leverage  of  the  whole  lower  extremity  the  weight  of  the  entire 
body,  are  more  common  than  of  any  other  joint. 

This  force  is  nearly  always  applied  through  eversion  or  inversion  (abduction  or 
adduction)  of  the  foot,  usually  the  former,  and  the  injury  consists  in  laceration  of  the 
fibres  of  a  lateral  ligament  with  strain  of  some  of  the  tendons  in  relation  to  the 
malleoli,  and  bruising  and  pinching  of  loose  synovial  membrane.  More  rarely 
extreme  dorsiflexion  will  injure  the  posterior  ligament  and  the  posterior  portions  of 


PRACTICAL    CONSIDERATIONS:    THE   ANKLE-JOINT.  451 

the  lateral  ligaments  (which  limit  that  movement),  and  further  injury  may  be  done  to 
the  synovial  sac  or  to  the  periosteum  or  to  the  bones  themselves  by  the  forcible 
impact  of  the  anterior  articular  edge  of  the  tibia  upon  the  astragalus.  Sprain  from 
hyperextension  (plantar  flexion)  is  still  rarer. 

In  sprains  from  abduction  there  may  be  in  the  severe  forms  a  momentary  slight 
outward  subluxation  of  the  astragalus,  as  the  shaft  of  the  fibula  is  elastic  enough  to 
permit  of  this  without  fracture. 

The  looseness  of  the  synovial  sac  (which  is  said  to  contain  normally  a  relatively 
larger  amount  of  synovia  than  any  joint  in  the  body),  the  dependent  position  of  the 
region,  and  the  remoteness  from  the  centre  of  circulation  make  the  swelling  and 
therefore  the  tension  of  the  joint  and  the  pain  following  sprain  very  noticeable. 

Disease  of  the  joint  is  frequent  for  the  same  reasons  that  sprains  are  frequent  and 
severe. 

In  simple  (traumatic)  synovitis  the  swelling  is  marked.  It  appears  first  in  front 
beneath  the  thin  anterior  ligament,  especially  towards  the  outer  side  just  in  advance 
of  the  lateral  ligament,  because  there  the  membrane  is  less  bound  down  by  extensor 
tendons.  Later  the  swelling  extends  downward  towards  the  dorsum  of  the  foot  for 
an  inch  or  more,  the  extensor  tendons  are  pushed  forward,  and  a  fulness  appears  on 
either  side  of  the  tendo  Achillis  which,  still  later,  extends  below  the  malleoli.  The 
posterior  swelling  is  perhaps  the  most  valuable  for  diagnosis,  as  it  is  not  so  likely  as 
the  anterior  swelling  to  be  confused  with  that  produced  by  disease  of  tendon-sheaths 
or  of  separate  bones  or  joints  of  the  tarsus. 

It  may  be  remembered  in  this  connection  that  the  general  shape  of  the  swelling 
in  ankle-joint  disease  is,  rudely,  like  that  of  an  "anklet," — horizontal, — while  the 
swelling  of  teno-synovitis  is  more  or  less  vertical  in  direction. 

No  early  distortion  of  the  foot  is  produced,  as  the  capacity  of  the  joint  is  but 
little  influenced  by  position  ;  but  later  the  calf  muscles  are  apt  to  overcome  the 
anterior  tibial  group  and  to  draw  up  the  heel,  causing  "  pointing"  of  the  toes. 

Tuberculosis  is  common,  and  is  unfavorable  in  its  course  because  of  the  ana- 
tomical conditions  above  recited,  the  proximity  of  the  numerous  tendon-sheaths,  the 
complex  synovial  sacs  of  the  tarsus,  and  the  large  amount  of  cancellous  tissue  in  the 
neighboring  bones,  and  also  because  of  the  difficulty  of  securing  complete  rest  and  at 
the  same  time  keeping  up  the  general  health. 

Excision  is  rarely  performed,  and  is  unsatisfactory  ;  but  arthrectomy,  done 
through  longitudinal  incisions  in  front  of  both  malleoli,  and  with  division  of  the 
malleoli  themselves,  or  removal  of  the  astragalus,  if  it  is  diseased,  has  been  followed 
by  good  results.  If  the  astragalus  is  to  be  removed  and  the  malleoli  spared  (which 
is  often  desirable  on  account  of  the  proximity  of  the  epiphyseal  lines),  the  lateral 
ligaments  will  have  to  be  divided.  By  one  or  other  of  these  plans  ample  access  to 
the  interior  of  the  joint  can  be  obtained.  Syme's  amputation  is,  however,  pre- 
ferred by  many  surgeons,  if  ankle-joint  disease  is  at  all  extensive. 

The  horizontal  line  of  the  ankle-joint  is  about  half  an  inch  above  the  tip  of  the 
internal  malleolus  and  therefore  an  inch  above  the  tip  of  the  external  malleolus. 

The  Joints  of  the  Tarsus,  Metatarsus,  and  Phalanges. — Dislocations  of 
the  astragalus — tibio-tarsal  dislocations — have  been  described  in  connection  with  the 
ankle-joint. 

Subastragaloid  dislocations — i.  e. ,  of  the  calcaneum  and  scaphoid  from  the  astrag- 
alus— are  almost  always  either  inward  and  backward  or  outward  and  backward, 
chiefly  because  of  the  shape  of  the  opposing  articular  surfaces  of  the  calcaneum  and 
astragalus.  The  upper  surface  of  the  os  calcis,  as  it  advances  forward,  descends 
suddenly  from  a  superior  to  an  inferior  level,  giving  the  articular  processes  an  oblique 
— i.e. ,  approximately  vertical — direction,  to  which,  of  course,  the  direction  of  the 
articular  facets  on  the  under  surface  of  the  astragalus  corresponds. 

It  is  obvious  that  much  more  resistance  is  offered  to  anterior  displacement  of 
the  calcaneum  than  to  displacement  in  the  opposite  direction,  and,  in  fact,  only  two 
examples  of  forward  subastragaloid  dislocation  have  been  recorded. 

The  astragalo-scaphoid  joint  is  involved  also,  but  the  rounded  head  of  the 
astragalus  offers  but  little  resistance  to  the  backward  or  lateral  movement  of  the 
scaphoid,  which,  moreover,  is  held  firmly  in  connection  with  the  os  calcis,  and  carried 


452  HUMAN   ANATOMY. 

with  it  because  of  the  greater  strength  of  the  calcaneo-scaphoid  as  compared  with  the 
astragalo-scaphoid  ligaments.  As,  owing  to  the  width  of  the  pelvis,  the  obliquity  of 
the  femur,  and  the  curve  of  the  tibia,  the  weight  of  the  body  is  transmitted  to  the 
astragalus  in  an  inward  direction,  it  would  be  displaced  inward  {i.e. ,  there  would  be 
an  outward  luxation  of  the  os  calcis  and  scaphoid)  far  more  frequently  than  in  the 
opposite  direction  were  it  not  for  the  resistance  offered  by  the  projection  of  the  sus- 
tentaculum and  the  lesser  articular  process  on  the  inner  side  and  the  outward  obliquity 
of  both  the  processes  of  the  posterior  calcaneo-astragaloid  joint.  The  two  lateral 
dislocations  associated  with  some  displacement  backward  are,  therefore,  about  equal 
in  frequency.  The  extensive  opposed  articular  surfaces  of  the  os  calcis  and  astragalus 
are  not,  as  a  rule,  completely  separated  ;  the  smaller  surfaces  of  the  astragalo-scaphoid 
joint  are,  so  that  the  one  is  a  subluxation,  the  other  a  complete  luxation. 

The  ligaments  uniformly  torn  are  the  interosseous  calcaneo-astragaloid,  the 
astragalo-scaphoid,  and  one  or  other  of  the  lateral  ligaments  of  the  ankle. 

In  inward  and  backward  luxation  the  symptoms  are  (a)  shortening  of  the  line 
between  the  mid-point  of  the  ankle  and  the  web  of  the  great  toe  ;  (b)  projection  and 
lengthening  of  the  heel  ;  (c)  inversion  and  adduction  of  the  foot,  the  inner  border 
shortened  and  concave,  the  outer  lengthened  and  convex  ;  (a?)  partial  disappearance 
of  the  internal  malleolus  ;  (<?)  projection  of  the  sustentaculum  tali  beneath  and  behind 
it  ;  (/)  projection  of  the  external  malleolus  and  of  the  head  of  the  astragalus  on  the 
outer  side  of  the  dorsum,  with  yielding  spaces  in  the  soft  parts  beneath  each.  The 
axis  of  the  leg,  when  continued  downward,  falls  to  the  outer  side  of,  or  even  external 
to,  the  foot.  The  scaphoid  can  be  felt  on  the  inner  side  of  the  foot.  The  deformity 
resembles  that  of  talipes  varus. 

In  outward  and  backward  luxation  a  and  b  are  the  same  ;  there  are  abduction  and 
eversion  of  the  foot,  and  disappearance  of  the  outer  and  prominence  of  the  inner 
malleolus  ;  the  deformity  resembles  that  of  talipes  valgus. 

The  medio-tarsal — astragalo-scaphoid  and  calcaneo-cuboid — articulation  usually 
escapes  injury  on  account  of  the  elasticity  of  the  anterior  pillar  of  the  arch  of  the  foot 
(into  which  it  enters)  and  because  of  the  numerous  joints  of  the  anterior  tarsal  and 
the  metatarso-phalangeal  regions  which  take  up  and  diffuse  force  applied  to  the 
anterior  part  of  the  foot. 

The  first  metatarsal  bone  is  more  frequently  dislocated  from  the  tarsus  than  any 
of  the  others,  as,  relatively  to  the  other  phalanges,  are  the  proximal  phalanx  and  the 


Fig.  467. 


First  metatarsal 


Fourth  metatarsal 


Sesamoid  bonea  * 
Section  of  right  foot  through  heads  of  metatarsal  bones,  showing  support  by  first  and  fourth. 

terminal  phalanx  of  the  same  toe.  These  dislocations  are  nearly  always  upward. 
Dislocation  of  the  proximal  phalanx  of  the  great  toe  may  be  as  difficult  to  reduce 
as  is  that  of  the  thumb.  Morris  thinks  that  the  sesamoid  bones  may  act  as  the 
anterior  ligament  does  in  the  latter  case, — i.e. ,  being  more  firmly  attached  to  the 
phalanx  than  to  the  metatarsal  bone,  they  may  be  torn  away  with  the  former,  and  by 
their  interposition  prevent  reduction. 

The  painful  affection  known  as  metatarsal gia  has  been  thought  (Morton)  to  be 
due  to  the  position  of  the  fifth  metatarso-phalangeal  joint,  so  much  posterior  to  the 
fourth  that  the  base  of  the  first  phalanx  of  the  little  toe  is  opposite  the  head  and  neck 
of  the  fourth  metatarsal.  As  the  fourth  and  fifth  metatarsal  bones  have  greater 
mobility  than  their  fellows,  it  was  supposed  that  this  relation  afforded  opportunity  for 


PRACTICAL    CONSIDERATIONS  :    THE    FOOT-JOINTS.  453 

accidental  compression  of  the  branches  of  the  external  plantar  nerve.  R.  Jones 
thinks  that  it  is  often  a  communicating  branch  between  the  fourth  division  of  the 
internal  plantar  and  the  external  plantar  that  is  compressed  between  the  bone  and  the 
ground  as  it  passes  beneath  the  head  of  the  fourth  metatarsal.  A  transverse  section 
of  the  foot  through  the  heads  of  the  metatarsals  shows  that  the  first  and  fourth  bear 
the  most  pressure  (Fig.  467).  The  situation  of  the  plantar  digital  nerves,  superficial 
to  and  not  between  the  bones,  and  the  collapse  of  the  transverse  arch  in  most  cases  of 
metatarsalgia,  broadening  the  intervals  between  the  bones,  but  increasing  pressure  on 
the  structures  beneath  them,  support  the  latter  view. 

Flat-foot  is  so  closely  associated  in  its  anatomical  deformities  with  talipes  valgus 
that  it  will  be  considered  in  relation  with  the  latter,  which,  with  the  other  varieties  of 
club-foot,  can  best  be  understood  after  the  muscles  and  fasciae  of  the  leg  and  foot 
have  been  described. 

Disease  of  the  tarsal  joints,  like  that  of  the  bones,  is  most  frequently  tuberculous 
in  character,  and  is  more  apt  to  remain  localized  when  it  is  situated  in  the  posterior 
pillar  of  the  main  arch, — i.e.,  in  the  posterior  half  of  the  calcaneo-astragaloid  joint. 
If  in  front  of  the  interosseous  ligament  dividing  that  articulation,  or  if  in  either  of  the 
mid-tarsal  joints  (with  which  it  communicates),  or  in  any  of  the  remaining  four 
synovial  cavities,  it  is  apt  to  extend  much  beyond  its  original  limits.  The  circum- 
stances that  favor  the  origin  (page  437)  and  influence  unfavorably  the  course  of  bone 
disease  in  this  region  apply  in  the  main  to  disease  of  the  joints.  In  whichever  tissue 
— bony  or  synovial — it  originates,  it  is  apt  to  spread  to  the  other.  The  astragalo- 
scaphoid  joint,  on  account  of  its  superficial  position  and  its  range  of  motion  (which  is 
greater  than  that  of  any  of  the  joints  below  the  ankle),  is  most  apt  to  be  affected. 
The  situation  of  the  swelling  and  tenderness  will  usually  differentiate  it  from  ankle- 
joint  disease  (page  450).  Probably  on  account  of  the  diffuse  infection  of  the  abundant 
cancellous  tissue  of  the  tarsal  bones  (either  primary  or  secondary  to  joint  disease), 
remote  tuberculous  infection — phthisis — follows  or  accompanies  disease  of  the  ankle 
and  tarsus  more  frequently  than  it  does  disease  of  any  other  part  except  possibly  the 
wrist  (Cheyne). 

Gout  affects  peculiarly  the  metatarso-phalangeal  joint  of  the  great  toe.  In  516 
cases  of  gout,  341  were  of  one  or  both  of  the  great  toes  alone  and  373  of  the  great 
toe  with  some  other  part  (Scudamore).  This  is  due  to  (a)  the  abundance  in  that 
region  of  dense  fibrous  tissue  of  little  vascularity  ;  (6)  its  remoteness  from  the  heart, 
the  force  of  the  circulation  being  at  its  minimum  ;  (c)  the  large  share  of  the  body 
weight  which  it  sustains,  as  the  anterior  extremity  of  the  main  arch  of  the  foot  ;  (d) 
the  frequency  of  traumatism  ;  (e)  the  constant  exposure  to  cold  and  damp  ;  (/)  its 
dependent  position. 

Landmarks. — The  ankle-joint  (q.v. )  lies  about  half  an  inch  above  the  tipof 
the  inner  malleolus.  Syme's  amputation  is  done  through  this  joint,  the  incision 
being  made  from  the  tip  of  one  malleolus  to  the  tip  of  the  other,  and  at  right  angles 
to  the  long  axis  of  the  foot. 

The  mid-tarsal  joint  (through  which  Chopart's  amputation  is  done)  runs  out- 
ward from  a  point  just  back  of  the  scaphoid  tuberosity,  and  passes  directly  over  the 
dorsum  of  the  foot  to  a  point  a  little  in  advance  of  the  middle  of  a  line  between  the 
tip  of  the  external  malleolus  and  the  tuberosity  of  the  fifth  metatarsal. 

Tne  tarso-metatarsal  joint  begins  at  a  point  about  one  and  a  half  inches  in  front 
of  the  tubercle  of  the  scaphoid, — i.e.,  just  back  of  the  base  of  the  first  metatarsal, — 
passes  at  first  directly  outward,  then  passes  irregularly  around  the  three  sides  of  the 
mortise  between  the  internal  and  external  cuneiforms  in  which  the  base  of  the  second 
metatarsal  rests,  and  then  slopes  slightly  backward  to  its  easily  recognized  termination 
on  the  outer  side  of  the  foot,  just  behind  the  base  of  the  fifth  metatarsal.  _ 

Hey's  amputation  begins  and  ends  at  the  two  extremities  of  this  joint-line,  but 
the  projection  of  the  internal  cuneiform  is  sawn  across.  In  Lisfranc's  amputation  the 
joint-line  is  followed  throughout.  The  metatarso-phalangeal  joints  lie  an  inch  behind 
the  interdigital  web. 


THE  MUSCULAR  SYSTEM. 

Muscular  Tissue  in  General. — Contractility,  although  exhibited  to  some 
degree  by  all  living  protoplasm,  is  possessed  especially  by  muscular  tissue,  the  sum 
of  the  contractions  of  such  tissue  being  expressed  in  motion,  the  most  conspicuous 
characteristic  of  all  the  higher  forms  of  animal  life.  Muscular  tissue  represents  a  high 
specialization  in  which  contraction  takes  place  along  definite  lines  corresponding  to 
the  long  axes  of  the  component  cells,  in  contrast  to  the  uncertain  contractility  occurring 
within  other  elements. 

The  simplest  form  of  contractile  tissue,  as  seen  in  some  of  the  low  invertebrates, 
is  represented  by  elements  of  which  the  superficial  part  is  related  to  the  integument, 
the  deeper  being  differentiated  into  contractile  fibres.  Although  such  musculo-epithe- 
lial  cells  may  form  an  almost  complete  contractile  layer,  the  muscular  fibres  do  not 
exist  as  an  independent  tissue.  The  differentiation  of  certain  cells  into  definite  mus- 
cular tissue,  however,  soon  appears  in  the  members  of  the  zoological  scale,  although 
the  existence  of  a  distinct  muscular  system  is  deferred  until  an  adequate  nervous 
system  is  developed. 

In  the  higher  animals  muscular  tissue  appears  in  two  chief  varieties,  the  striated 
and  non-striated,  depending  upon  the  respective  histological  characteristics  of  their 
constituent  elements.  The  former  makes  up  the  muscles  controlled  by  the  will,  and 
is,  therefore,  also  termed  voluntary  muscle  ;  the  latter,  which  constitutes  the  contrac- 
tile tissue  within  the  walls  of  the  hollow  viscera,  blood-vessels  and  other  tubes,  acts 
independently  of  volition,  and  is  spoken  of  as  involuntary  muscle.  The  last  named 
is  sometimes  also  designated  vegetative  muscle,  since  the  organs  in  which  it  is  present 
are  largely  concerned  in  the  nutritive  processes  ;  the  term  animal  may  be  applied  in 
contrast  to  voluntary  muscle.  The  association  of  the  striated  muscle  with  response 
to  volition  and,  on  the  contrary,  of  the  non-striated  variety  with  involuntary  action 
must  be  accepted  with  certain  reservations,  since  in  some  animals  the  development  of 
marked  striation  never  takes  place  within  the  fibres  of  voluntary  muscle.  There  is, 
indeed,  not  a  little  evidence  going  to  show  that  the  structural  differences  which  exist 
between  the  striated  and  non-striated  musculature  are  correlated  with  their  physio- 
logical activities,  and  that  no  fundamental  distinction  can  be  drawn  between  them 
on  purely  morphological  grounds.  Muscles  which  in  one  group  of  animals  possess 
the  characteristics  of  striated  muscle-tissue  may,  in  another  group,  be  represented 
by  non-striated  fibres  (the  muscles  of  the  cesophagus,  for  instance),  and  it  seems 
probable  that  the  greater  portion  of  the  voluntary  cranial  musculature  is  serially 
equivalent  to  the  involuntary  musculature  of  the  trunk. 

The  non-striated  or  involuntary  muscle  represents  a  tissue  less  highly  specialized 
than  the  striped,  the  latter  exhibiting  to  a  conspicuous  degree  histological  differentia- 
tion. Constituting,  in  a  way,  a  separate  and  intermediate  group  stands  heart  muscle, 
which,  while  beyond  the  control  of  the  will,  presents  striated  fibres  ;  the  latter  occupy 
histologically  a  place  between  the  fibre-cell  of  the  involuntary  and  the  elongated 
striated  fibre  of  the  voluntary  muscle.  It  is  desirable,  therefore,  to  consider  the  sim- 
pler type  of  contractile  tissue   before  examining  the  more  complex  voluntary  muscle. 

NON-STRIATED  OR  INVOLUNTARY  MUSCLE. 

This,  the  less  highly  differentiated  variety  of  muscular  tissue,  occurs  in  the  form 
of  bundles  and  thin  sheets  principally  within  the  walls  of  the  organs  and  vessels, 
although  enjoying  a  wide  distribution,  seldom  presenting  robust  masses,  and  being 
entirely  unconnected  with  the  skeleton.  Even  when  present  in  considerable  amount, 
this  tissue  is  usually  inconspicuous,  presenting  a  faint  yellowish  tint. 

The  distribution  of  non-striped  muscle  includes  :  i.  The  digestive  tract, — the 
muscularis  mucosa?  from  the  cesophagus  to  the  anus  and  delicate  bundles  within  the 
454 


NON-STRIATED   OR   INVOLUNTARY   MUSCLE.  455 

mucosa  and  villi ;  the  muscular  tunic  from  the  lower  half  of  the  cesophagus  to  the  anus  ; 
in  the  large  excretory  ducts  of  the  liver,  pancreas,  and  some  salivary  glands,  as  well 
as  in  the  gall-bladder.  2.  The  respiratory  tract, — in  the  posterior  part  of  the  trachea, 
encircling  bundles  in  the  bronchial  tubes  as  far  as  their  terminal  divisions.  3.  The 
urinary  tract, — in  the  capsule  and  pelvis  of  the  kidney,  ureter,  bladder,  and  urethra. 


Involuntary  muscle  from  intest 

4.  The  male  generative  organs, — in  the  epididymis,  vas  deferens,  seminal  vesicles, 
prostate  body,  Cowper's  glands,  and   cavernous  and  spongy  bodies  of  the  penis. 

5.  The  female  generative  organs, — in  the  oviducts,  uterus,  and  vagina  ;  in  the  broad 
and  round  ligaments  ;  in  the  erectile  tissue  of  the  external  genitals  and  of  the  nipple. 

6.  The  vascular  system, — in  the  coats  of  the  arteries,  veins,  and  larger  lymphatics. 

7.  The  lymphatic  glands, — in  the  capsule  and  trabecular  of  the  spleen  ;  sometimes  in 
the  trabecular  of  the  larger  lymph-nodes.  8.  The  eye, — in  the  iris  and  ciliary 
body  ;  in  the  eyelids.  9.  The  integument, — in  the  sweat-  and  some  sebaceous 
glands,  as  the  minute  erector  muscles  of  the  hair-follicles  and  in  the  skin  covering 
the  scrotum  and  parts  of  the  external  genitals. 

Structure. — Non-striated,  unstriped,  pale  or  involuntary  muscle  consists  of 
an  aggregation  of  structural  units  known  as  the  fibre-cells.  These  are  deli- 
cate spindle,  often  prismatic,  elements  which  terminate  in  oblique  surfaces  at  either 
end  for  contact  with  adjacent  cells.     They  vary  greatly  in  size,  measuring  from  .  050- 

.225  mm.  in  length  and  .003-008  mm. 
in  width.  The  muscle-cells  found  in  the 
skin  and  blood-vessels  are  short  (.015- 
.020  mm.)  and  broad  ;  those  in  the  in- 
testinal wall  are  more  elongated  (.215- 
.220  mm.)  and  delicate.  The  largest 
elements  are  encountered  in  the  gravid 
uterus,  in  which  they  attain  a  length  of 
.500  mm.  and  a  breadth  of  .030  mm. 
Occasionally  the  cells  are  bifurcated  at 
the  ends,  especially  among  the  lower  ver- 


tebrates. 


Fig.  470. 

Portions  of  intestinal  muscle-cells,  showing  nucleus  and        Bundles  of   involuntary  mus 
centrosome  (c).     Highly  magnified.     {Lcnlwssi'k.)  showing  the  fibre-cells  ( 

More  recent  critical  examinations  of  the  fibre-cells  have  demonstrated  the 
existence  of  greater  structural  complexity  than  was  formerly  recognized.1  According 
to  these  later  views,  each  fibre-cell  consists  of  a  protoplasmic  mass  in  which  lie 
embedded  the   nucleus  and  the   contractile  fibrillce.      The  former  is  appropriately 

1  An  exhaustive  review  of  the  literature  and  various  opinions  concerning  the  structure  of 
unstriped  muscle  is  given  by  M.  Heidenhain  :  Ergebnisse  der  Anatomie  und  Entwick.,  Bd.  x., 
1900.  J 


456 


HUMAN   ANATOMY. 


Fig.  471. 


voluntary  muscle  cut 


described  as  rod-shaped,  being  cylindrical  with  rounded  ends.  Its  position  is  fre- 
quently eccentric  with  regard  to  the  axis  of  the  cell,  as  well  as  often  somewhat  nearer 
one  pole  than  the  other.  The  nuclei  of  these  muscle-cells  are  rich  in  chromatin, 
which  usually  presents  a  reticular  arrangement.      Under  the  influence  of  contraction, 

the  nuclei  present  more  or  less 
variation  from  their  typical  rod 
form.  Centrosomes  (Fig.  469) 
may  be  distinguished  in  favorable 
preparations  lying  within  the  cy- 
toplasm close  to  the  nucleus  (Zim- 
mermann,  Lenhossek). 

The  contractile  fibrillce  rep- 
resent differentiated  anisotropic 
threads  within  the  cell-body,  in 
their  property  of  double  refraction 
resembling  the  fibrilla;  of  striped 
muscle.  They  are  most  conspicu- 
ous at  the  periphery  of  the  fibre- 
cell,  where  they  lie  closely  related 
to  the  condensed  boundary  zone 
(Heidenhain)  which  forms  the 
exterior  of  the  fibre  and  fulfils  the 
purpose  of  a  limiting  membrane 
or  sarcolemma,  although  no  such  definite  structure  encloses  the  muscle-cell  as  in  the 
case  of  the  striated  fibre.  The  demonstration  of  contractile  fibrillas  within  the  muscle- 
cells  of  the  higher  vertebrates  is  unsatisfactory  on  account  of  the  small  size  of  the 
elements  ;  in  the  large  cells  of  the  amphibia,  especially  in  the  huge  elements  of  the 
amphiuma,  their  presence  is  readily  established.  Although  lying  usually  within  the 
periphery  of  the  fibre-cell,  the  existence  of  a  conspicuous  axial  fibre  is  seen  in  certain 
cases,  as  in  the  large  isolated  muscle-cells  within  the  mesentery  of  newts. 

The  individual  elements  of  unstriped  muscle  are  held  together  by  delicate  mem- 
branous expansions  of  connective  tissue  prolonged  from  the  more  robust  septa  investing 
and  uniting  the  bundles  and  fasciculi  of  the  fibre- 
cells.  On  cross-section  (Fig.  470),  these  inter- 
cellular membranous  partitions  appear  as  delicate 
lines  between  the  transversely  cut  cells,  which 
were  formerly  interpreted  as  tracts  of  cement- 
substance  uniting  the  muscular  elements.  The 
appearances  of  intercellular  bridges,  described  by 
several  authors  (Barfuth,  de  firuyne,  Werner, 
Bohemann,  Apathy)  as  connecting  the  adjacent 
cells,  depend  probably  upon  the  shrinkage  of 
the  latter  due  to  the  action  of  reagents  (Stohr, 
Heidenhain). 

The  blood-vessels  supplying  involuntary 
muscle  are  guided  in  their  distribution  by  the 
septa  of  interfascicular  connective  tissue  in  which 
the  larger  twigs  run.  The  latter  give  off  minute 
branches  which  terminate  in  capillaries  that  ex- 
tend between  the  primary  bundles  of  the  muscle- 
cells.  The  blood-supply  of  non-striated  muscle 
is  meagre  when  compared  with  that  of  the  striped 
muscles. 

The  lymphatics  occur  closely  associated 
with  the  muscular  tissue  in  localities  in  which 

the  latter  exists  in  considerable  quantity,  as  in  the  wall  of  the  stomach  and  intestine, 
the  interfascicular  connective  tissue  containing  plexuses  of  lymph-channels, 

The  nerves  supplying  involuntary  muscle  are  intimately  related  to  the  sympa- 
thetic system.      The  larger  trunks  form  plexuses,  in  close  association  with  microscopic 


Fig.  472. 


Portion  of  injected  intestinal  wall,  showing- 
arrangement  of  blood-vessels  supplying  invol- 
untary muscle ;    upper    longitudinally,  lower 


STRIATED   OR   VOLUNTARY    MUSCLE. 


457 


ganglia,  from  which  delicate  twigs  pass  between  the  bundles  of  muscle-cells.  The 
mode  of  their  ultimate  termination  is  described  in  connection  with  nerve-endings 
(page  1015). 

Development. — All  muscular  tissue  in  the  higher  types,  with  the  exception  of 
that  found  within  the  sweat-glands  and  the  iris,1  may  be  regarded  practically  as  a 
derivation  of  the  mesoblast.  Reference  to  Fig.  34  (page  29)  recalls  the  division 
of  the  mesoblast  into  the  parietal  and  visceral  layers,  the  latter,  in  conjunction  with 
the  entoblast,  constituting  the  splanchno-pleuric  folds  by  the  union  of  which  the 
gut-tube  is  formed.  The  subsequent  differentiation  of  the  visceral  mesoblast  contributes 
the  layers  of  the  wall  of  the  digestive  canal  outside  the  epithelial  structures  derived  from 
the  entoblast  ;  in  typical  parts  of  the  tube  these  layers  are  the  submucous,  muscular, 
and  serous  coats.  The  muscular  tunic  consists  of  the  unstriped  involuntary  variety, 
the  component  fibre-cells  representing  specialized  mesoblastic  elements. 

Fig.  473. 

Mesothelium  of  serous  coat 


Differentiating  muscular  tissue 

Young  connective  tissue 
Epithelium  lin 


lar  tissue  from  splanchnic 


The  details  of  the  development  of  the  muscular  tissue  include  condensation  of 
the  young  mesoblast  produced  by  conspicuous  proliferation  and  increase  in  the  cells, 
followed  by  their  gradual  elongation  and  conversion  into  spindle  elements.  These 
are  at  first  short,  but  become  extended  as  the  tissue  assumes  its  fully  developed 
character.  In  localities  in  which  the  involuntary  muscle  occurs  in  sparingly  dis- 
tributed bundles  and  net-works  the  mesoblastic  elements  gradually  assume  the  form 
of  spindle-cells  which  for  a  time  are  inconspicuous  and  difficult  to  distinguish  from 
ordinary  young  connective  tissue.  The  formation  of  the  muscular  tissue  within  the 
walls  of  blood-vessels  is  closely  identified  with  the  intramesodermic  origin  of  the 
vascular  channels,  the  entire  walls  of  which  tubes  are  contributions  of  the  middle 
germinal  layer. 

STRIATED    OR    VOLUNTARY    MUSCLE. 

The  striped  muscular  tissue  constitutes  the  conspicuous  masses  known  as  the 
"  muscles"  or  "  flesh"  attached  to  the  bony  framework  of  the  body.  These  organs 
are  also  termed  the  skeletal  muscles,  and  supply  the  active  agents  in  moving  the 
passive  levers  represented  by  the  bones  in  producing  the  movements  of  the  animal. 

The  muscles  are  usually  elongated  in  form,  and  consist  of  aggregations  of  bundles 

of  the  ultimate  contractile  elements,  the  fibres,  grouped  into  fasciculi ;  upon  the  size 

of  the  latter  depends  the  texture  of  the  muscles,  coarse  or  fine,  as  distinguished  in  the 

dissecting-room.      In  localities  in  which  the  fasciculi  are  of  large  size,  as  in  the  gluteus 

1  Szili  :  Archiv  fur  Ophthalmol.,  Bd.  liii.,  1902. 


458 


HUMAN    ANATOMY. 


& 


maximus,  the  muscles  are  conspicuous  on  account  of  their  coarse  texture  ;  a  fine- 
grained muscle,  on  the  contrary,  is  composed  of  small  fasciculi.  In  addition  to 
variations  in  the  thickness  of  the  fasciculi,  the  latter  differ  greatly  in  length  irrespec- 
tive of  the  extent  of  the  entire  muscle,  since  the  length  of  the  fasciculi  depends  largely 

upon  the  arrangement  of  the  ten- 
iae 474.  dons.      A  long  muscle  may  be 
y?~X  composed  of  short  fasciculi,  since 
..-  ;"V  5  (TTv.                   the  latter  may  be  attached  to  ten- 
-.,/,.';  ".   "\  ■■  .              dons  which   cover  its   opposite 
.,-^;~f;-7".y']  CfT-h''---}    ''            sides   or  extend  within   its  sub- 
,yyyj  .'"-'"'■'"       '"-                        stance  as  septa.      In  such  cases, 
,.__  ^  .  \.,      " '•' ' '. '■■'  -  '   '    .•>  ,          as   m  the  rectus  femoris  or  the 
^•C^.f --■'--' i  ':         C-c.  ••  -    /^f%         deltoid,    the  short  fasciculi  run 
.yy--, --:■_'  j  _',.-""'     i  c'  -       ;"/          obliquely,    thereby  producing  a 
-  <~y?-'~~  ^'r'-^- ~i  :~  - ,       *    '.    ,,-.^--'V  .        pennate  arrangement  which  often 
,y !  r'-~ "V  "",.,"--".,..'-  ..•          •" :■  ■'  -  yy  •       characterizes    muscles    of   great 

strength.  When,  on  the  con- 
trary, the  tendons  are  limited  to 
the  ends  of  a  muscle,  the  fascic- 
uli are  relatively  long  and  may 
extend  its  entire  length.  The 
sartorius  contains  fasciculi,  as 
well  as  fibres,  of  conspicuous  ex- 
tent, some  bundles  stretching 
the  entire  distance  between  the 
tendons. 

General  Structure  of 
Striated  Muscle. — The  histo- 
logical unit  of  voluntary  muscular 
tissue  is  the  transversely  striated 
or  striped  muscle-fibre,  which 
represents  a  highly  specialized 
single  cell.  The  fibres  are  the 
contractile  elements  by  the  shortening  of  which  the  length  of  the  entire  muscle  is 
decreased  and  the  force  exerted.  The  fibres  are  cylindrical,  or  prismatic  with  rounded 
angles,  in  form,  and  vary  from  .01-  1  mm.  in  diameter  ;  no  constant  relation  exists 
between  the  thickness  of  the  fibres  and  the  size  of  the  muscle  of  which  they  are  the 
components,  and,  indeed,  their  diameter  varies  even  within  the  same  muscle.  In 
general  the  limb  muscles  are  composed  of  large  fibres,  those  of  the  mature  male  sub- 
ject usually  exceeding  the  corresponding  fibres  of  the  female.  The  length  of  the 
muscle-fibres  is  likewise  subject  to  great  variation.  As  a  rule,  the  fibres  composing 
a  muscle  are  of  limited  length,  generally  not  exceeding  from  4-5  cm. ;  in  exceptional 
instances,  however,  as  in  the  sartorius,  they  may  attain  a  length  of  over  1 2  cm.  and 
a  width  of  from  1-5  mm.  (Felix).  The  fibres 
are  usually  somewhat  spindle-shaped,  being 
slightly  larger  in  the  middle  than  at  the  ends, 
which  are  usually  more  or  less  pointed  ;  blunted 
or  club-shaped  and,  more  rarely,  branched  ex- 
tremities are  not  uncommon.  Branched  and 
anastomosing  fibres  occur  in  certain  localities, 
as  in  the  tongue,  facial  and  ocular  muscles. 

The  individual  fibres,  each  invested  in  its 
own  sheath,  or  sarcolemma,  are  grouped  into 
small  primary  bundles,  the  component  fibres  of 
which  are  held  together  by  a  meagre  amount  of 
connective  tissue,  the  endomysium.  The  latter  is  continuous  with  the  perimysium 
investing  the  primary  bundles.  These  are  associated  into  uncertain  groups,  the 
secondary  bundles,  which  are  united  and  enclosed  by  extensions  and  subdivisions  of 
the  general  connective-tissue  envelope  of  the  entire  muscle,  the  epimysium.    In  muscles 


Several  primary 


-^Sfiiiy; 

mscle-bundles  in  transverse  sectii 
tigement  of  component  fibres.     X  t 


Fig.  475. 


STRIATED   OR   VOLUNTARY    MUSCLE. 


459 


possessing  a  fine  grain  the  secondary  bundles  correspond  with  the  fasciculi,  but  in 
muscles  of  coarse  texture  each  fasciculus  includes  a  number  of  secondary  bundles 
between  which  the  ramifications  of  the  epimysium  extend.  The  characteristic  picture 
presented  in  transverse  sections  of  muscles  (Fig.  474)  illustrates  the  relation  of  the 
fibres  to  the  larger  groupings  of  the  muscular  elements. 

Structure  of  the  Muscle-Fibre. — Each  fibre  corresponds  to  a  greatly 
elongated  multinucleated  muscle-cell,  and  consists  of  a  sheath,  or  sarcolemma,  and 
the  contained  sarcous  substatice. 

The  sarcolemma  forms  a  complete  investment  of  the  fibre  and  alone  comes 
into  contact  with  the  surrounding  connective  tissue  by  which  the  muscle-fibres  are 
attached  either  to  one  another  or  to  the  tendinous  structures  upon  which  they  exert 
their  pull.  The  sarcolemma  is  a  transparent,  homogeneous,  elastic  membrane  which 
so  closely  invests  the  contained  sarcous  substance  as  to  be  almost  invisible  under 
ordinary  conditions.  Being  of  greater  toughness  than  the  muscle-substance,  it  often 
withstands  mechanical  disturbance,  as  teasing,  while  the  latter  becomes  broken  ; 
where  such  breaks  occur  the  sarcous  substance  sometimes  contracts  within  the  sarco- 
lemma, which  at  the  points  of  fracture  then  becomes  visible  as  a  delicate  tubular 
sheath  stretching  across  the  space  separating  the  broken  ends- of  the  more  friable 

Fig.  476. 


mum 


Diagrams  illustrating  structure  of  striated  muscle-fibre.  A,  usual  view;  B,  correct  view,  showing  sustentacular 
sepia  continued  across  ribrefrom  sarcolemma;  C,  septa  shown  after  vanadium-ha  matoxylin  staining,  ^.interme- 
diate disk  (Zwischenscheibe) ;  Jt  light  band;  Qt  transverse  disk  (Querscheibe)  \  Af,  median  disk  (Mittelscheibe)  ; 
S,  sarcolemma.     (After  M.  HciJcnhain.) 


sarcous  substance  (Fig.  475).  In  teased  preparations  the  sarcolemma  is  sometimes 
also  seen  projecting  beyond  the  sarcous  substance,  as  a  coat  sleeve  covers  the  stump 
of  an  arm. 

The  sarcous  or  muscular  substance  within  the  sarcolemma  in  turn  consists 
of  two  parts,  the  less  differentiated  passive  sarcoplasm  and  the  highly  specialized 
contractile  fib7'illce  in  which  the  active  changes  take  place  resulting  in  the  contraction 
of  the  muscle-fibre. 

Since  the  highly  characteristic  appearance  of  cross-striation  which  distinguishes 
the  fibres  of  voluntary  muscle,  as  well  as  supplies  the  reason  for  its  designation  as 
striped  or  striated,  depends  upon  the  arrangement  of  the  contractile  fibrillse,  the 
details  of  the  latter  first  claim  attention. 

The  cross-striation  consists  of  alternate  dark  and  light  bands  which  extend  the 
entire  width  of  the  fibre  and  depend  upon  the  differentiation  of  the  contractile  fibrillas 
into  segments  of  greater  or  less  density.  Close  lateral  approximation  of  the  more 
dense  and  deeply  staining  segments  in  the  fibrillar  lying  side  by  side  within  the  sarco- 
lemma, produces  the  dark  band  ;  the  similar  relation  of  the  less  dense  and  non-staining 
segments  produces  the  impression  of  the  light  band.  If  it  were  possible  to  isolate  the 
individual  contractile  fibrillas,  each  would  present  the  details  shown  in  the  accompany- 
ing diagram  (Fig.  476).      The  dark,  broad  transverse  disk  (Q)  of  doubly  refracting, 


460 


HUMAN    ANATOMY. 


or  anisotropic,  substance  is  succeeded  at  either  end  by  the  light  band  {J J)  of  singly 
refracting,  or  isotropic,  substance.  The  light  band  is  subdivided  by  a  delicate  line, 
the  intermediate  disk  (Z  ),  also  known  as  Krause1  s  ?nembrane.  The  sequence  which 
by  repetition  makes  up  the  contractile  fibrilla  consists,  therefore,  of  Z  +_/+  Q  -\-J-\-Z. 
Under  favorable  conditions  for  examination  the  transverse  disk  exhibits  less  density 
midway  between  its  ends  ;  this  zone  is  traversed  by  a  delicate  line  (  M ) ,  the  median 
disk  (Hensen,  Merkel)  or  middle  membrane  (M.  Heidenhain). 

The  interpretation  of  these  appearances,  shown  as  usually  seen  under  moderate 
amplification  in  the  accompanying  photograph  (Fig.  477),  has  been  the  subject  of 
much  laborious  investigation  and  vexed  discussion  ;  even  at  the  present  time  authorities 
are  far  from  accord  as  to  the  significance  of  the  observed  details  in  their  relations  to  the 
architecture  of  the  muscle-fibre.  It  is  beyond  the  purpose  of  these  pages  to  review 
the  various  theories  concerning  the  ultimate  structure  of  striped  muscle  ; '  suffice  it  to 
point  out  that,  apart  from  the  conclusions  of  those  observers  who  from  time  to  time 
have  contended  that  the  appearances  are  entirely  optical  and  do  not  correspond  to 

actual  structural  details,  two  chief 


Fig.  477. 


views  regarding  the  architecture  of 
the  muscle-fibre  have  been  held. 
According  to  the  one,  championed 
by  Krause,  the  intermediate  zone 
is  regarded  as  the  expression  of 
a  membranous  septum  which 
stretches  entirely  across  the  mus- 
cle-fibre as  an  inward  extension  of 
the  sarcolemma  and  thus  subdi- 
vides the  fibre  into  a  number  of 
minute  compaitments,  or  contrac- 
tile disks,  by  the  longitudinal  ap- 
position of  which  the  entire  fibre 
is  built  up.  The  other  view,  early 
accepted  by  Kolliker,  regards  the 
fibre  as  made  up  of  fibrill<z  ex- 
tending the  length  of  the  fibre, 
the  transverse  cleavage  into  disks 
being  secondary  and  artificial.  The 
fibrillar  theory  as  advanced  by  Rol- 
let  has  received  wide  acceptance 
and  deserves  brief  mention.  Ac- 
cording to  this  authority,  the  con- 
tractile fibrillar  are  to  be  conceived 
as  forming  anisotropic  rods  consisting  of  alternating  thicker  and  thinner  segments 
(Fig.  478),  the  former  corresponding  in  position  with  the  broad,  dark,  transverse 
disk,  the  latter  with  the  lighter  band,  since  the  meagre  amount  of  doubly  refracting 
substance  in  this  zone  is  masked  by  the  large  quantity  of  isotropic  sarcoplasm. 
Rollet  recognized  the  intermediate  disk  as  consisting,  not  of  a  continuous  membrane, 
but  as  an  interrupted  line  representing  a  row  of  minute  beads  which  exist  as  local 
accumulations  on  the  thinner  segments  of  the  fibrilla.  Rollet' s  conception  of  the 
fibre,  therefore,  included  the  sarcolemma  containing  the  sarcoplasm  in  which  the  con- 
tractile fibrillar  were  embedded. 

More  recent  investigations  with  the  aid  of  improved  differential  stains  have  led 
to  a  modification  of  the  fibrillar  view  in  so  far  that  the  intermediate  disk  is  to  be 
regarded  as  a  structure  that  is  attached  to  the  sarcolemma  and  extends  between  the 
fibrillar.  M.  Heidenhain  believes  the  median  disk  to  be  an  additional  membrane  that 
likewise  meets  the  sarcolemma  at  the  periphery  of  the  fibre.  The  later  conception 
of  muscle  architecture  in  no  wise  questions  the  existence  of  the  fibrillae  as  the  con- 
tractile elements  of  the  fibre,  but  regards  them  as  held  in  place  by  the  lateral  braces 

1  An  exhaustive  review  of  the  literature  and  various  opinions  regarding  the  structure  of 
striped  muscle  is  given  by  M.  Heidenhain:  Ergebnisse  der  Anatomie  und  Entwick.,  Bd.  ix. . 
1899. 


Photograph   of   striated  muscle,   showing  the 
under  moderately  high  magnification 


STRIATED    OR   VOLUNTARY    MUSCLE. 


461 


represented  by  the  intermediate  and  median  bands.  The  foregoing  diagram  (Fig. 
476),  modified  from  Heidenhain,  indicates  the  relations  of  the  several  bands  to  be 
seen  in  muscle  when  examined  under  the  most  favorable  conditions.  That  various 
reagents  produce  marked  changes  in  the  details  of  the  muscle-picture  admits  of  no 
question  ;  this  has  been  graphically  represented  by  the  last-quoted  author.1  The  fact 
that  the  intermediate  disk  is  attached  to  the  sarcolemma  is  shown  by  the  constrictions 
or  scalloped  margin  in  the  outline  of  the  fibre  during  contraction,  the  constrictions 
corresponding  in  position  to  the  attachment  of  the  membranes  of  Krause.  The 
striped  muscle  of  certain  insects  exhibits  an  additional  band,  the  accessory  disk,  sub- 
dividing the  light  zone  (J). 

The  distribution  of  the  contractile  fibrillae  throughout  the  fibre  is  not  uniform, 
since  the  fibrillae  are  grouped  into  bundles,  the  muscle-columns  or  sarcostyles.  This 
arrangement  is  well  shown  in  suitably  prepared  transverse  sections  of  muscular  tissue 
(Fig.  479),  in  which  the  individual  fibres  are  seen  to  be  made  up  of  minute  stippled 
areas  separated  by  clear  lines.  These  areas  are  known  as  Cohnheiiri  s  fields,  and 
represent  the  transversely  cut  groups  of  contractile  fibrillae.  The  clear  lines  indicate 
the  distribution  of  the  sarcoplasm  ;  in  addition  to  forming  the  net-work  dividing 
Cohnheim's  fields,  the  sarcoplasm  separates  the  groups  of  individual  fibrillae,  each 
muscle-column  being  entirely  surrounded  by  the  less  highly  differentiated  substance. 


Fig.  47S. 


Fig.  479. 


Diagram  illustrating  Rollet's  view  of  structure  < 
muscle-fibre  and  relations  of  assumed  details  to  usu; 
appearances  of  tissue. 


section,  showing 
'      X  650. 


When  seen  in  longitudinal  section,  the  sarcoplasm  between  the  groups  of  fibrillae 
appears  as  lines  extending  the  entire  length  of  the  fibre,  to  which  an  inconspicuous 
longitudinal  striation  is  thus  imparted. 

The  muscle-fibre  has  already  been  spoken  of  as  a  multinucleated  cell.  The 
nuclei  resulting  from  the  division  of  the  nucleus  of  the  embryonal  cell  remain  within 
the  sarcoplasm  and  are  termed  muscle-nuclei.  Their  position  in  mammalian  muscle 
is  usually  immediately  beneath  the  sarcolemma  ;  in  certain  fibres,  however,  as  those 
composing  the  semitendinosus  of  the  rabbit  (Fig.  480),  and  of  uncertain  distribution 
in  man,  the  nuclei  lie  more  deeply  embedded  within  the  sarcoplasm,  therein  agreeing 
in  location  with  the  position  occupied  by  the  nuclei  in  the  muscular  tissue  of  many 
of  the  lower  vertebrates  (Fig.  479). 

Variations  in  the  color  and  contractility  of  muscular  tissue  have  been  described 
by  Ranvier  and  Krause,  Klein,  Griitzner,  and  others.  While  the  skeletal  muscles 
are  usually  of  a  pale  tint  and  contract  energetically  when  stimulated,  particular  mus- 
cles of  certain  animals,  as  the  semitendinosus  and  the  soleus  in  the  rabbit,  possess  a 
deeper  color  and  contract  more  slowly  and  prolongedly  under  stimulation.  Such 
red  muscles,  as  they  have  been  named,  are  composed  of  fibres  which  are  thinner  than 
common  and  possess  a  relatively  larger  amount  of  sarcoplasm,  in  which  the  muscle- 
nuclei  are  embedded  not  only  immediately  beneath  the  sarcolemma,  but  also  in  the 

1  M.  Heidenhain  :  Anatom.  Anzeiger,  Bd.  xx.,  Nos.  2  and  3,  1901. 


462 


HUMAN    ANATOMY. 


deeper  parts  of  the  fibre  (Fig.  480).  The  longitudinal  striation  is  also  unusually  con- 
spicuous, due  to  the  exceptional  amount  of  interfibrillar  sarcoplasm.  Although  not 
present  in  mammals  generally  in  sufficient  quantity  to  affect  the  appearance  of  entire 
muscles,  the  peculiar  "  red"  fibres  are  found  in  many  localities  intermingled  with  the 
more  usual  pale  variety.  Klein  has  described  such  fibres  in  the  diaphragm,  and, 
according  to  the  investigations  of  Griitzner  and  of  J.  Schaffer,  it  is  probable  that  they 
are  found  in  all  muscular  tissue  upon  which  devolves  prolonged  effort.  These  fibres 
are,  therefore,  present  in  the  heart,  the  eye  muscles,  and  the  muscles  of  respiration  and 
of  mastication.  The  red  fibres  must  be  regarded  as  representing  a  less  complete 
differentiation  of  the  muscle-cell  and  as  possessing  consequently  a  larger  proportion 
of  reserve  protoplasm  ;  they  are  better  able  to  withstand  the  fatigue  of  contractions 
than  those  in  which  the  specialization  of  a  larger  part  of  the  cytoplasm  has  occurred. 
The  pale  fibres  gain  in  rapidity  of  contraction  at  the  expense  of  early  exhaustion. 

Attachment  of  the  muscular  fibres,  whether  to  other  fibres  or  to  tendons,  is 
accomplished  by  the  union  of  the  sarcolemma  with  the  connective  or  tendinous  tissue 


Fig.  4S0. 


Jem 


Fig.  4S1. 


m 


^4  c„ 


m  1 
1  ) 


(  S 


\r—^z ; 


Portion  of  the  soleus  muscle  of  the  rabbit 
verse  section.     The  more  coarsely  stippled  fibr- 
"  red"  muscle ;  they  also  contain  nuclei  w'" 
cous  substance.     X  160. 


Section  of  tendon,  showing  termination  of  muscle- 


and  never  by  direct  fusion  of  the  connective  tissue  with  the  sarcous  substance,  the 
latter  remaining  completely  invested  by  its  sheath.  On  joining  a  muscle  (Fig.  481), 
the  tendon-tissue  subdivides  into  small  bundles  which  receive  and  surround  the  pointed 
ends  of  the  muscle-fibres,  the  fibrous  tissue  becoming  attached  to  the  sarcolemma, 
while  the  areolar  tissue  between  the  tendon-bundles  blends  with  that  separating  the 
muscle-fibres. 

Cardiac  Muscle. — The  striped  muscle  of  the  heart,  in  addition  to  the  pecu- 
liarity of  being  beyond  the  control  of  the  will,  although  striated,  presents  certain 
modifications  in  the  form  and  arrangement  of  its  fibres  which  call  for  special  con- 
sideration. According  to  the  views  formerly  held,  the  histological  unit  of  the  myo- 
cardium was  the  branched  fibre-cell  (Fig.  482),  by  the  apposition  of  which  the  sheets 
of  muscular  tissue  were  formed.  The  fibre-cell  was  regarded  as  a  short  branched 
fibre,  devoid  of  a  sarcolemma  and  possessing  a  nucleus  surrounded  by  a  considerable 
area  of  undifferentiated  sarcoplasm.  The  investigations  of  M.  Heidenhain1  have 
shown  that  the  constitution  of  the  heart-fibres  corresponds  more  closely  to  that  of 
1  Anatom.  Anzeiger,  Bd.  xx.,  Nos.  2  and  3,  1901. 


STRIATED    OR    VOLUNTARY    MUSCLE. 


463 


ordinary  muscle,  the  chief  difference,  in  addition  to  their  shorter  length,  being  the 
complicated  partial  longitudinal  division  which  these  fibres  undergo.      Fig.  483  repre- 
sents diagrammatically  the  peculiar  step- 
Fig.  482.  like  relation  of  the  fibres  and  their  nu- 

merous secondary  or  intercalated  limbs. 
.     .;         ■<  Each  fibre  possesses  a  sarcolemma  which, 

::  ITR  however,   is  less   firm  and  resistant  than 

■'VO  /  _    4  t^lat  usua-Hy  seen.     The  heart  muscle  pos- 


m  t 


i#rh  ..  ; 


m  m 


■;'■ 


Muscle-fibres  of  human  heart.     X  375- 


sesses  a  relatively  large  amount  of  sarcoplasm,  as  evidenced  by  the  considerable 
accumulation  surrounding  the  nucleus,  as  well  as  the  thicker  strata  separating  the 
muscle-columns.      The  unusual  quantity  of  sarcoplasm  accounts  for  the  conspicuous 

Fig.  484. 


Capillary  blood-vessel 


M*% 


'ill/..,    r ., 


«a 


f       0^-.  %®m 

-  ■  J'.v  %  -"^     mk 


-Undifferentiated  sarcopla 


Wf% 


Fibres  of  cardiac  muscle  in  trans 


■  section.     X  375- 


longitudinal  striation  of  cardiac  muscle  and  agrees  with  what  may  be  expected  in 
muscular  fibres  subjected  to  such  constant  activity. 


464 


HUMAN    ANATOMY. 


The  blood-vessels  of  striped  muscle  are  very  numerous  to  insure  adequate 
nutrition  to  a  tissue  of  great  functional  activity.  The  larger  arteries  and  accompany- 
ing veins  penetrate  the  muscle  along  the  septal  extensions  of  the  epimysium  and 
divide  into  smaller  branches  which  run  between  the  fasciculi.      These  vessels  undergo 

further  subdivision  into  twigs  which  pass  between 
Fig.  485.  the  finer  bundles  of  muscle-fibres  and  ultimately 

break  up  into  the  capillaries  enclosing  the  indi- 
vidual fibres. 

The  capillary  vessels  of  voluntary  muscle 
form  a  characteristic  net-work  consisting  of  nar- 
row rectangular  meshes  (Fig.  485),  the  longer 
sides  of  which  correspond  to  the  direction  of 
■^^ij^1  the  muscle-fibres  between  which  they  run  ;  the 

shorter  sides  of  the  meshes  are  formed  by  the 
capillaries  which  extend  across  or  may  encircle 
the  individual  fibres.  The  capillaries  supplying 
muscles  subjected  to  prolonged  and  powerful 
contractions  often  exhibit  local  dilatations,  which 
may  serve  for  temporary  reservoirs  for  the  blood 
during  contraction.  The  closeness  of  the  capil- 
lary net-work  is  determined  by  the  size  of  the 
muscle-fibres,  muscles  composed  of  fine  fibres 
possessing  the  smallest  vascular  meshes. 

The  relation  of  the  blood-vessels  to  cardiac 
muscle  is  unusually  intimate,  the  capillaries  not 
only  enclosing  the  muscle-fibres  with  a  rich  net- 
work, but  lying  within  depressions  on  the  surface 
of  the  fibres,  or  even  in  channels  surrounded  by 
the  muscular  tissue  (Meigs). 
The  lymphatics  of  striated  muscular  tissue  are  represented  by  the  interfascicular 
clefts,  which  extend  within  the  connective  tissue  between  the  muscle-fibres,  and  the 
more  definite  channels  within  the  septa.  The  larger  lymph-vessels  formed  by  the 
confluence  of  those  lying  between  the  fasciculi  pass  to  the  sheath  of  the  muscle  and 
tendon  and  carry  off  the  lymph  from  the  muscular  tissue. 

The  nerves  supplying  striped  muscle  include  both  motor  and  sensory  fibres. 
The  former  terminate  in  specialized  arborizations,  the   motor  nerve-endings,  which 


Injected  voluntary  m 
ment  of  interfascicular 
X  50-  . 


Fig.  486. 


Neural  canal 


Ectoblast- 
Lateral  plate  of  myotome  - 


Medial  plate  of  myotome r^r?.  ',•?'     .'■  •   '^SiiS? 


Parietal  mesoblast  of £ 

somatopleura 


Wolffian  body 
Parietal  mesoblast 


Umbilical  vein 


Body-cavity  Aorta  Body-cavity 

Transverse  section  of  rabbit  embryo,  sbowing  differentiation  of  myotomes.    X  90. 


are  usually  regarded  as  lying  beneath  the  sarcolemma  upon  the  sarcous  substance. 
The  sensory  fibres  are  connected  witii  the  neuro-muscular  end  organs  or  muscle- 
spindles,  from  which  the  afferent  nerves  proceed  centrally.      The  detailed  description 


STRIATED    OR    VOLUNTARY    MUSCLE. 


465 


of  both  varieties  of  terminations  in  striped  muscle  will  be  found  under  nerve-endings 
(page  1014). 

Development  of  Striped  Muscle. — The  early  appearance  of  a  series  of 
quadrilateral  segmental  areas,  the  somites,  within  the  tract  of  the  paraxial  mesoblast 
on  each  side  of  the  neural  tube  has  been  described  (page  29).  Likewise  the  sub- 
sequent breaking  up  of  each  somite  into  the  centrally  situated  sclerotome  and  the 
peripheral  myotome  (Eig.  34).  The  latter  soon  becomes  a  compressed  C-shaped 
mass,  in  which  the  more  compact  lateral  part  is  usually  described  as  the  cutis-plate 
and  the  medial  portion  as  the  muscle-plate.  The  histological  characters  of  these  parts 
of  the  myotome  differ,  the  cutis-plate  consisting  of  several  layers  of  closely  packed 
cells  resembling  epithelial  elements,  while  the  muscle-plate  is  composed  of  more 
loosely  disposed  spindle-cells,  between  which  lie  irregularly  round  cells,   many  of 

Fig.  4S7. 


Fig.  4SS. 


Frontal  section  of  rabbit  embryo,  showing 
myotomes.    X  100. 


ntal  section  of  two  myotomes  of  rabbit  embryc 
showing  deyeloping  muscle.     X  130. 


which  are  actively  engaged  in  division.  The  less  differentiated  round  cells,  or 
myoblasts,  become  elongated  and  transformed  into  the  spindle-cells,  the  elements 
which  are  directly  converted  into  the  young  muscle-fibres.  The  spindle-cells,  at  first 
mononuclear,  rapidly  increase  in  length,  the  round  or  oval  nucleus  at  the  same  time 
undergoing  division.  In  consequence  the  elongated  muscle-cells  become  multinuclear. 
The  cytoplasm  of  the  cells  early  exhibits  differentiation  into  a  peripheral  and  a 
central  zone.  During  the  second  foetal  month  the  former  manifests  a  disposition  to 
become  fibrillar,  while  the  central  zone  for  a  time  remains  undifferentiated  and  contains 
the  muscle-nuclei. 

On  cross-section  the  young  muscle-fibres  at  this  stage  appear  as  stippled  rings 
enclosing  an  indifferent  core  surrounding  the  nuclei,  the  stippling  being  due  to  the 
partially  differentiated  fibrillae.  The  latter  appear  first  as  marginal  groups,  but 
later  form  a  continuous  peripheral  zone.  This  gradually  widens,  and  by  the  close 
of   the  sixth  fcetal  month  the  fibres  composing  the  muscles  of  the  upper  extremity 

30 


466  HUMAN   ANATOMY. 

have  become  fibrillar  throughout  their  entire  thickness  ;  those  of  the  lower  ex- 
tremity acquire  a  similar  condition  a  month  later.  With  the  deeper  extension  of 
the  fibrillee  the  characteristic  cross-striation  appears,  the  nuclei  migrating  to  the 
periphery  of  the  fibre  as  the  less  differentiated  cytoplasm  becomes  invaded.  The 
sarcolemma  appears  by  the  time  the  entire  fibre  has  become  fibrillar.  The  sarcoplasm 
surrounding  the  nuclei  of  the  mature  fibre  represents  the  remains  of  the  less  highly 
differentiated  cytoplasm  of  the  original  muscle-cell  ;    that,  however,  separating  the 

muscle-columns  must  be  regarded 
Fig.  4S9.  as  the  product  of  a  secondary  dif- 

ferentiation. 
-„r-,  r,.,  The  designation  "cutis-plate," 

gife-3        '-'-j     -*fi  applied  to  the  compact  outer  epi- 

C'i>         -3R    :^^g^g&s?~~~      "--         ^-.--i^  thelioid  portion  of  the  myotome, 

^sgg-\-  "      Z———    ■--"'    ;/  expresses  the    relation   to  the  in- 

■-'::.-;_  ^-*-         tegument  which  has  been  widely 

accepted,    since    this    part  of   the 
-r  myotome  is  generally  regarded  as 

-  -      -   : ..-a&£^~- concerned  in  the  formation  of  the 

V--.  .^sssfa--^— - ■" """--  '  ■'■-  connective-tissue    portion    of    the- 

~lTr-~--~^s« '/:.,-  skin.     This   fate   of    the    "  cutis- 

,->.       «g5^  ,1-^  plate"    was   long  age  denied   by 

^* •■  Balfour,  who  held  that  both  layers 

Developing  voluntary  muscle ;  the  fibres  are  still  unstriated.    X  525.      of    the  myotome  are  concerned  in 

the  formation  of  muscular  tissue. 
Kaestner  *  arrived  at  similar  conclusions,  and  more  recently  Bardeen 2  has  shown  that 
in  the  pig  practically  the  entire  epithelial  lamella  is  converted  into  muscle.  According 
to  this  investigator,  while-some  of  the  epithelial  elements  of  the  skin-plate  degenerate, 
the  greater  number  undergo  mitosis  and  give  rise  to  myoblasts  which,  in  turn,  become 
the  spindle-cells  from  which  the  muscle-fibres  are  developed.  The  outer  margin  of 
the  epithelial  lamella  is  sharply  defined  by  a  limiting  membrane  formed  by  the  adja- 
cent cells  ;  a  somewhat  similar  but  less  pronounced  boundary  guards  the  inner  con- 
tour of  the  lamella.  The  external  limiting  membrane  persists  until  the  conversion  of 
the  epithelioid  elements  into  myoblasts  and  spindle-cells  has  been  well  established,  by 
which  time  the  mesoblastic  tissue  surrounding  the  myotomes  has  grown  in  between 
the  latter  and  the  adjacent  ectoblast  ;  it  is  from  this  source,  therefore,  and  not  from 
the  "cutis-plate,"  that  the  connective- tissue  layer  of  the  integument  is  derived. 

The  masses  of  embryonal  muscle,  or  myomeres,  derived  from  the  somites  are 
early  separated  by  the  ingrowth  of  intersegmental  septa  of  connective  tissue  which, 

Fig.  490. 


Developing  muscle-fibres  in  which  striation  is  just  appearing.     X  375- 

later  support  the  intersegmental  blood-vessels  and  nerves  and,  in  the  thoracic  region,. 
the  costal  elements,  and,  by  the  ingrowth  of  a  connective-tissue  partition,  each  one- 
is  further  divided  into  a  dorsal  and  a  ventral  portion,  from  which,  in  a  general  way, 
the  muscles  associated  with  the  spine  and  the  antero-lateral  body-walls  are  derived 
respectively. 

In  this  primitive  condition  the  trunk  musculature  is  represented  by  a  series  of. 

1  Archiv  fur  Anat.  u.  Phys.,  Suppl.  Bd.,  1890. 

2  Johns  Hopkins  Hospital  Reports,  vol.  ix.,  1900. 


STRIATED   OR   VOLUNTARY   MUSCLE.  467 

bands, — the  myomeres, — each  of  which  consists  of  a  dorsal  and  a  ventral  portion, 
and  which  succeed  one  another  regularly  and  segmentally  throughout  the  entire 
length  of  the  trunk.  The  muscle-fibres  of  which  each  myomere  is  composed  extend 
from  the  intersegmental  septum  in  front  to  that  behind,  having  thus  a  regular  antero- 
posterior direction.  In  the  lower  vertebrates  this  condition  persists  with  but  little 
modification  throughout  life,  producing  the  flake-like  arrangement  of  the  muscles 
characteristic  of  the  fishes.  In  the  higher  vertebrates,  however,  numerous  secondary 
modifications  supervene,  whereby  the  myomeres  are  broken  up  into  individual  mus- 
cles, their  original  segmental  arrangement  becoming  at  the  same  time  greatly  ob- 
scured, although  it  still  persists  in  those  regions  in  which  the  muscles  are  intimately 
associated  with  segmental  skeletal  structures  such  as  the  vertebra  and  ribs. 

These  changes  are  of  several  kinds,  and,  as  a  rule,  several  varieties  of  modi- 
fication cooperate  in  the  differentiation  of  a  muscle.  Some  of  the  more  important 
are  as  follow  : 

1.  An  end-to-end  fusion  of  several  myomeres  or  portions  of  myomeres  takes 
place,  producing  a  muscle-sheet  or  band  which  extends  uninterruptedly  through  sev- 
eral primary  segments.  Such  a  modification  gives  rise  to  muscles  supplied  by  a 
number  of  segmental  nerves  ;  just  as  many,  indeed,  as  there  are  myomeres  partici- 
pating in  the  formation  of  the  muscle.  Examples  of  muscles  formed  in  this  way  are 
to  be  seen  in  the  musculature  of  the  abdominal  walls,  the  oblique  muscles,  the  trans- 
versalis,  and  the  rectus,  for  instance,  being  all  polymeric  muscles,  as  are  also  many 
of  the  longitudinal  muscles  of  the  back.  Not  infrequently  the  origin  of  these  mus- 
cles by  the  fusion  of  portions  of  successive  myomeres  is  shown,  independently  of 
their  nerve-supply,  by  the  persistence  in  their  course  of  some  of  the  intermuscular 
septa,  these  forming  transverse  tendinous  bands  traversing  the  muscle  in  a  horizontal 
direction.  Such  tendinous  inscriptions  {inscriptiones  ten/tinea),  as  they  are  termed, 
occur  normally  in  the  rectus  abdominis,  and  are  also  frequently  found  in  the  internal 
oblique,  the  sterno-hyoid,  and  the  sterno-thyroid  muscles. 

2.  A  longitudinal  division  of  the  myomeres  into  a  number  of  distinct  and  origi- 
nally parallel  portions  may  occur.  Examples  of  this  modification  combined  with  the 
end-to-end  fusion  of  the  portions  so  formed  from  successive  myomeres  are  very 
abundant.  Thus,  the  rectus  abdominis  is  the  result  of  the  splitting  off  of  the  ventral 
portion  of  a  number  of  successive  myomeres,  whose  remaining  portions  are  largely 
represented  in  the  oblique  and  transverse  abdominal  muscles.  So,  too,  in  the  neck,, 
the  differentiation  of  the  sterno-hyoid  and  omo-hyoid  is  due  to  the  same  process, 
and  it  has  also  acted  in  the  differentiation  of  the  various  muscles  of  the  transverso- 
costal  group  of  the  dorsal  musculature. 

3.  A  tangential  splitting  of  the  myomeres  is  again  an  occurrence  of  great  fre- 
quency, producing  superposed  muscles,  and  is  clearly  shown  in  the  dorsal  muscula- 
ture and  in  the  ventro-lateral  muscles  of  the  thoracic  and  abdominal  walls.  It 
does  not  necessarily  involve  all  portions  of  a  myomere  when  this  has  already  divided 
longitudinally,  but  may  be  confined  to  only  certain  of  the  parts  so  formed.  Thus, 
while  it  affects  the  ventro-lateral  abdominal  muscles,  it  does  not  affect  the  rectus 
abdominis,  this  muscle  representing  the  entire  thickness  of  the  ventral  borders  of  a 
number  of  successive  myomeres. 

4.  Associated  with  the  change  just  described  there  is  frequently  a  modification 
in  the  direction  of  the  fibres  in  one  or  more  of  the  superposed  muscles.  Primarily 
the  fibres  of  each  myomere  have  a  cephalo-caudal  direction, — a  condition  which  is 
still  retained  in  the  rectus  abdominis,  for  instance.  In  the  ventro-lateral  abdominal 
and  thoracic  muscles,  however,  the  original  direction  of  the  fibres  has  been  greatly 
altered,  those  of  the  superficial  layer  being  directed  in  general  downward  and  inward, 
those  of  the  middle  layer  to  a  considerable  extent  downward  and  outward,  while 
those  of  the  deepest  layer  are  directed  almost  or  quite  transversely, — that  is 
to  say,  in  a  direction  which  is  900  different  from  that  taken  by  the  fibres  of  the 
myomere. 

5.  An  exceedingly  interesting  modification  is  that  which  results  from  the  migra- 
tion of  some  of  the  myomeres  over  their  successors,  so  that  a  muscle  formed  from 
certain  of  the  cervical  myomeres,  for  example,  may  in  the  adult  condition  be  super- 
posed upon  muscles  derived  from  the  thoracic  segments.     In  such  cases  of  migration 


468  HUMAN    ANATOMY. 

the  segmental  nerve,  or  at  least  those  fibres  of  it  which  originally  supplied  the  por- 
tions of  the  myomeres  in  question,  retains  its  connection  and  is  consequently  drawn 
out  far  beyond  its  usual  territory,  a  ready  explanation  being  thus  afforded  for  the 
extended  course  of  the  long  thoracic,  long  subscapular,  and  phrenic  nerves.  The 
muscles  supplied  by  these  nerves,  as  well  as  the  pectoralis  major  and  minor  muscles, 
are  all  derived  from  cervical  myomeres,  their  adult  position  being  due  to  the  process 
of  migration,  of  whose  existence  they  form  convincing  examples. 

6.  Finally,  portions  of  one  or  several  successive  myomeres  may  undergo  degen- 
eration, becoming  converted  into  connective  tissue,  which  may  have  the  form  of 
fascia,  aponeurosis,  or  tendon.  Examples  of  this  degeneration  are  to  be  found  in 
practically  all  muscles,  since  the  tendons  by  which  they  make  their  bony  attachments 
have  resulted  from  its  action.  In  the  lower  vertebrates  and  in  the  fcetus  tendons 
and  aponeuroses  are  much  less  developed  than  in  the  higher  forms  or  in  the  adult, 
being  represented  by  muscular  tissue  which  later  becomes  converted  into  tendon  or 
aponeurosis.  The  intermuscular  septa  between  the  muscles  of  the  limbs  seem  to 
have  arisen  in  this  way,  and  occasionally  relatively  large  aponeurotic  sheets  have  so 
arisen,  as  in  the  case  of  the  aponeurosis  which  unites  the  two  posterior  serratus 
muscles.  Of  especial  interest  in  this  connection  are  the  degenerations  into  liga- 
ments of  muscle-tissue  primarily  occurring  in  the  neighborhood  of  many  of  the 
joints,  the  accessory  ligaments  being  in  many  cases  formed  in  this  manner.  Thus, 
the  external  lateral  ligament  of  the  knee-joint,  the  ligamentum  teres  of  the  hip-joint, 
and  even  the  great  sacro-sciatic  ligament  owe  their  origin  to  this  process,  and  many 
other  of  the  ligaments  may  also  be  referred  to  it. 

As  a  result  of  these  various  modifications  and  their  combinations  the  individual 
muscles  of  the  adult  body,  together  with  the  apconeurotic  sheets  which  are  frequently 
associated  with  them,  are  formed. 

GENERAL    CONSIDERATION    OF    THE   VOLUNTARY    MUSCLES. 

The  voluntary  or  striated  muscles  constitute  a  very  considerable  portion  of  the 
entire  mass  of  the  body,  their  weight  in  an  average  adult  male  having  been  esti- 
mated at  about  43.4  per  cent,  of  the  total  body  weight  (Vierordt).  Each  muscle 
is  a  distinct  organ  composed  of  a  number  of  contractile  fibres  united  into  bundles  or 
fasciculi  surrounded  by  a  delicate  sheath  of  connective  tissue,  the  perimysmm,  in 
which  blood-vessels  and  nerves  ramify  to  the  various  fasciculi,  and  which,  at  the 
surface  of  the  muscle,  is  continuous  with  the  fascia  which  encloses  the  entire  organ. 

At  each  extremity  of  the  muscle  the  contractile  tissue  is  united  with  dense 
connective  tissue,  the  general  structure  of  which  resembles  that  of  the  muscle,  its 
fibres  being  arranged  in  distinct  bundles  separated  and  enclosed  by  looser  tissue 
comparable  to  the  perimysium.  By  means  of  these  tendons,  as  they  may  generi- 
cally  be  termed,  the  attachment  of  the  muscle  to  portions  of  the  skeleton  or  other 
structures  is  effected.  The  extent  to  which  the  tendon  is  developed  varies  greatly 
in  different  muscles,  in  some  being  hardly  noticeable,  so  that  the  muscle-tissue 
appears  to  be  directly  attached  to  the  bone  (Fig.  496),  at  other  times  forming  a 
long  rounded  or  flattened  band  (Fig.  576),  to  which  the  term  tendon  is  usually 
applied,  or  again  forming  a  broad,  flat  expansion,  termed  an  aponeurosis  (Fig.  525). 
Both  the  tendons  and  aponeuroses  are  to  be  regarded  as  representing  portions  of  the 
original  muscle  converted  into  connective  tissue,  and,  indeed,  comparative  anatomy 
shows  that  many  of  the  ligaments  and  aponeuroses  of  the  body,  even  although  they 
may  not  seem  to  be  directly  related  to  neighboring  muscles,  are  really  to  be  regarded 
as  muscles  which  have  undergone  a  tendinous  degeneration. 

Attachments. — The  great  majority  of  the  voluntary  muscles  are  attached  at 
either  end  to  portions  of  the  skeleton,  passing  over  one  or  more  joints,  in  which 
they  effect  movement  by  their  contraction.  Occasionally,  however,  a  muscle  may 
be  attached  at  one  of  its  extremities,  in  part  or  entirely,  to  fascia,  as,  for  instance, 
the  gluteus  maximus  and  the  tensor  fasciae  lata?,  or  both  of  its  attachments  may  be 
to  fascia,  as  is  the  case  with  some  of  the  muscles  of  expression  and  with  the  muscles 
of  the  palate  and  the  intrinsic  musculature  of  the  tongue.  Others,  again,  may  have 
one  or  both  of  their  attachments  to  tendons  of  other  muscles, — e.g.,  the  accessorius 


GENERAL  CONSIDERATION  OF  THE  VOLUNTARY  MUSCLES.     469 

and  the  lumbricales, — while  others  may  pass  between  portions  of  the  skeleton  and 
special  organs  upon  which  they  act,  as  is  exemplified  by  the  muscles  of  the  eyeball. 
Whatever  may  be  the  nature  of  the  structure  to  which  the  attachment  is  made, 
it  is  convenient  for  purposes  of  description  to  regard  one  of  the  points  of  attachment 
of  each  muscle  as  the  fixed  point  from  which  it  acts  in  contraction,  and  to  speak  of 
this  as  its  origin,  and  to  regard  the  other  as  the  point  upon  which  it  acts,  speaking 
of  it  as  the  insertion.  It  must  be  understood,  however,  that  this  distinction  between 
the  two  attachments  is  somewhat  arbitrary,  since  what  is  usually  the  fixed  point  may 
under  certain  circumstances  become  the  movable  one.  For  instance,  in  the  case  of 
a  muscle  passing  from  the  pelvis  to  a  leg  bone,  if  the  body  be  erect,  the  contraction 
of  the  muscle  will  cause  an  inclination  of.  the  trunk  on  the  hip-joint,  the  attachment 
to  the  leg  bone  being  then  the  fixed  point  and  that  to  the  pelvis  the  movable  one. 
In  other  positions  of  the  body,  however,  the  contraction  of  the  muscle  will  produce 
a  movement  of  the  leg,  the  fixed  and  movable  points  being  exactly  reversed.  Since, 
however,  the  movement  of  the  leg  may  be  regarded  as  the  more  usual  result  of  the 
contraction  of  the  muscle,  the  pelvic  attachment  is  arbitrarily  regarded  as  the  origin 
and  the  attachment  to  the  femur  or  tibia  the  insertion  of  the  muscle  in  question. 


Diagrams  showing  semi-pinnate  (A) 
origin  aoove  to  that  of  insertion  below. 
(After  Poirier.) 


Fig.  491. 


Central  portion 


and  pinnate  (B) 

C,  compound  pinnate  ar 


Form. — The  muscles  assume  various  forms,  dependent  to  some  extent  upon 
the  structures  to  which  they  are  attached.  Some  are  thin  sheets  with  almost  parallel 
fibres,  others  are  more  or  less  band-like,  while  others  may  have  considerable  thick- 
ness, and  be  quadrate,  triangular,  or  spindle-shaped.  Surrounding  certain  of  the 
orifices  of  the  body  are  what  are  termed  orbicular  ox  sphincter  muscles  (Figs.  495, 
499),  consisting  of  a  muscular  sheet  whose  fibres  have  a  crescentic  course  around 
either  side  of  the  orifice,  the  lips  of  which  will  tend  to  be  drawn  together  by  the  con- 
traction of  the  muscle. 

Where  the  surfaces  for  attachment  are  considerable,  the  fibres  composing  a 
muscle  have  a  more  or  less  parallel  course  ;  but  where  a  comparatively  small  area  is 
all  that  is  available  for  the  attachment  of  a  strong  muscle,  as  is  the  case  with  many 
of  the  limb  muscles,  it  is  clear  that  such  an  arrangement  cannot  obtain.  The  muscle- 
fibres  then  converge  from  either  one  or  both  sides  to  be  inserted  one  above  the  other 
into  the  tendon,  forming  what  is  termed  a  semipinnate  (e.  g. ,  many  of  the  muscles 
of  the  leg,  Fig.  609J,  or  pinnate  muscle  (e.  g. ,  interossei  dorsales,  Fig.  590.)  This 
convergence  may  take  place  towards  either  one  or  both  tendons  of  attachment,  and 
occasionally  these  may  spread  out  over  opposite  surfaces  of  the  muscle  to  form  apo- 
neurotic sheets  which  overlap,  so  that  the  muscle-fibres  pass  obliquely  from  the  sur- 
face of  one  tendon  to  that  of  the  other  (e.g. ,  gastrocnemius,  semitendinosus,  Fig. 
635).  Finally,  in  some  of  the  broader  muscles  (e.g. ,  deltoid  and  subscapularis)  the 
muscle-fibres  may  arise  from  and  converge  to  a  series  of  tendinous  bands  which 


47Q  HUMAN    ANATOMY. 

alternate  with  one  another,  the  muscle  having  thus  a  compound  pinnate  arrangement 
(Fig.  491,  C). 

As  a  rule,  the  tendons  occur  in  connection  with  the  extremities  of  the  muscle, 
but  occasionally  one  or  more  tendinous  intersections  may  occur  in  the  course  of  the 
muscle,  which  thus  becomes  divided  into  two  or  more  bellies.  This  condition  may 
be  the  result  of  the  end-to-end  union  of  the  tendons  of  attachment  of  two  primarily 
distinct  muscles  (e.g.,  digastric,  Fig.  497)  or  to  the  persistence  of  some  of  the 
dividing  lines  which  separate  the  various  embryonic  segments  of  which  a  muscle 
may  be  composed  (e.g.,  rectus  abdominis,  Fig.  523)  ;  or  it  may  be  due  to  a  sec- 
ondary attachment  formed  by  a  muscle  in  its  course,  it  being  bound  down  to  a 
neighboring  bone  by  a  band  of  fascia  (e.g. ,  omo-hyoid). 

Certain  muscles  present  the  peculiarity  of  possessing  two  or  more  separate 
heads  of  origin,  attached  to  different  bones  and  uniting  to  form  a  common  tendon  of 
insertion.  In  certain  cases  (e.g. ,  biceps  femoris,  pronator  radii  teres)  this  condition 
indicates  the  union  of  two  primarily  distinct  muscles  which  had  a  common  insertion, 
or  which  were,  at  all  events,  originally  inserted  close  together,  but  in  other  cases  it 
has  resulted  from  a  separation  of  an  original  muscle  into  two  portions.  The  ana- 
tomical nomenclature  is  not  quite  consistent  as  regards  such  muscles,  since  it 
describes  the  biceps  femoris  as  a  two-headed  muscle,  although  its  two  heads  are 
fundamentally  distinct  organs  ;  while,  on  the  other  hand,  it  usually  regards  the 
psoas  and  iliacus  and  the  gastrocnemius  and  soleus  as  distinct  muscles,  notwith- 
standing their  common  insertion. 

Fasciae. — Connecting  the  various  muscles  and  uniting  them  into  groups,  and 
also  surrounding  the  entire  musculature  of  the  body  and  separating  it  from  the 
deeper  layers  of  the  integument,  are  sheets  of  connective  tissue  known  as  fascice. 
These  sheets  are  by  no  means  isolated  portions  of  connective  tissue,  but  are  rather 
to  be  regarded  as  parts  of  the  general  interstitial  connective-tissue  net-work  which 
traverses  all  parts  of  the  body,  thickened  to  form  more  or  less  definite  sheets  stand- 
ing in  relation  to  the  neighboring  organs.  The  density  of  the  sheets  varies  greatly  ; 
in  some  regions  they  are  imperfectly  developed  and  may  contain  considerable 
amounts  of  fat,  while  in  others  they  form  dense,  glistening  sheets  resembling  the 
expansions  of  tendons  mentioned  above,  and  termed,  like  these,  apo?ieuroses. 

It  is  convenient  to  recognize  two  principal  layers  of  fasciae,  the  superficial  and 
the  deep. 

The  superficial  fascia  immediately  underlies  the  skin  of  the  entire  body,  and  is 
sometimes  considered  a  portion  of  it  and  termed  the  panniculus  adiposus,  since, 
except  in  the  eyelids,  penis,  scrotum,  and  labia  minora,  it  contains  considerable  quan- 
tities of  fat.  It  is  connected  with  the  subjacent  deep  fascia  by  a  more  or  less  exten- 
sively developed  layer  of  areolar  tissue,  which,  however,  is  lacking  in  certain  regions, 
such,  for  instance,  as  the  face,  the  palmar  surface  of  the  hand,  and  the  plantar 
surface  of  the  foot,  where  the  superficial  and  deep  fasciae  are  intimately  united. 

The  deep  fascia,  on  the  other  hand,  immediately  covers  and  invests  the  muscles, 
and  in  the  intervals  between  them  becomes  continuous  with  the  periosteal  connec- 
tive tissue  enclosing  the  bones.  Those  lamellae  of  the  fascia  which  dip  down 
between  the  muscles  of  the  limbs — the  intermuscular  septa- — are  frequently  of  con- 
siderable firmness  and  serve  for  the  origin  of  fibres  of  the  neighboring  muscles,  and 
occasionally  muscles  (e.g. ,  soleus,  levator  ani)  take  their  origin  in  part  directly 
from  portions  of  the  deep  fascia,  which  then  becomes  thickened  along  the  line  of 
the  origin  to  form  strong  bands,  termed  arms  tendinei,  attached  at  either  extremity 
to  neighboring  bones. 

Certain  portions  of  the  deep  fascia,  and  especially  of  the  intermuscular  septa, 
represent  portions  of  the  muscular  system  which  have  undergone  tendinous  degen- 
eration, and  are  represented  by  muscular  tissue  in  the  lower  vertebrates.  Indeed, 
the  relative  amount  of  aponeurotic  and  tendinous  tissue,  as  compared  with  the  mus- 
cular, is  very  much  greater  in  the  higher  than  in  the  lower  forms,  and  is  appre- 
ciably greater  in  the  human  embryo  than  in  the  adult,  indicating  a  transformation 
of  one  tissue  into  the  other  during  the  life  of  the  individual. 

Tendon-Sheaths. — Where  tendons  run  in  grooves  of  bones,  bands  of  dense 
connective  tissue  extend  across  between  the  lips  of  the  grooves,  being  continuous 


GENERAL  CONSIDERATION   OF   THE  VOLUNTARY  MUSCLES.    471 

there  with  the  periosteum,  and  convert  the  grooves  into  canals  within  which  the  ten- 
dons are  enclosed,  although  capable  of  free  movement  to  and  fro.  These  connective- 
tissue  bands  are  the  tendon-sheaths,  and  the  canals  which  they  assist  in  forming 
may  contain  one  or  more  tendons.  Each  sheath  is  lined  on  its  deeper  surface  by  a 
synovial  membrane  similar  to  those  occurring  in  the  joints,  and  at  either  extremity 
of  the  sheath  this  membrane  is  reflected  upon  the  tendon  which  it  encloses,  so  that 
the  tendon  is  contained  within  a  double-walled  cylinder  whose  cavity  is  filled  with  a 
fluid  serving  to  diminish  friction  during  the  movements  of  the  tendon  (Fig.  492).  It 
is  customary  to  distinguish  the  synovial  portion  of  a  tendon-sheath  as  the  serous  or 
synovial  sheath  (vagina  mucosa)  from  the  fibrous  sheath 
(vagina  fibrosa)  with  which  it  is  always  closely  con-  Fig.  492. 

nected. 

Strands  of  connective  tissue  pass  at  intervals  across 
the  synovial  cavity  of  the  sheath  from  the  floor  of  the 
groove  on  the  bone  and  transmit  blood-vessels  to  the 
tendon  ;  these  strands  constitute  what  are  termed  vin- 
culo tendinum,  or,  from  their  general  similarity  to  the 

mesentery,  mesotendons.  Diagram  showing  relations  of  ten- 

J  '  111  donto  tcmloii-shcath  as  in  cross-suction 

In  some  cases  a  tendon-sheath  may  serve  to  a  cer-     0f  finger, 
tain  extent  as  a  pulley,  affording  a  smooth  surface  over 

which  the  tendon  changes  its  direction,  as  in  the  case  of  the  extensor  tendons  of  the 
hand  when  this  is  partly  extended.  A  special  development  of  this  condition  is  to  be 
seen  in  the  tendinous  loop  (trochlea  muscularis)  over  which  the  tendon  of  the  superior 
oblique  muscle  of  the  eyeball  is  reflected  (Fig.  516). 

Bursae. — The  intervals  between  the  various  muscles  and  between  these  or  their 
tendons  and  the  bone  are  occupied  by  loose  areolar  tissue.  In  situations  in  which 
a  muscle  or  tendon  in  its  movements  comes  in  contact  with  a  bony  prominence,  or  in 
which  two  tendons  glide  upon  each  other,  the  spaces  of  the  areolar  tissue  enlarge  and 
become  filled  by  a  fluid  resembling  that  of  the  synovial  cavities,  the  result  being  the 
formation  of  what  is  termed  a  bursa,  whose  purpose  is  to  diminish  the  friction  between 
the  muscle  or  tendon  and  the  bone.  Examples  of  such  bursa?  are  to  be  found  abun- 
dantly in  connection  with  the  muscles  of  the  limbs,  and  some  of  those  which  occur 
in  the  vicinity  of  joints  frequently  fuse  with  the  adjacent  synovial  cavities  ;  the  bursa 
of  the  subscapularis,  situated  between  that  muscle  and  the  neck  of  the  scapula,  for 
instance,  uniting  with  the  synovial  cavity  of  the  shoulder-joint,  and  the  bursa  supra- 
patellaris,  between  the  tendon  of  the  quadriceps  femoris  and  the  femur,  fusing  with 
the  cavity  of  the  knee-joint. 

Bursa;  are  also  developed  in  the  areolar  tissue  intervening  between  the  superficial 
and  deep  fascia?  in  situations  in  which  the  integument  rests  directly  upon  a  bone,  as, 
for  instance,  over  the  olecranon  process,  and  is  frequently  subjected  to  pressure  in 
that  region.  Such  bursse  are  termed  subcutaneous  biirscs  to  distinguish  them  from 
those  developed  in  connection  with  the  muscles. 

Classification  of  the  Muscles. — The  muscles  may  be  classified  according 
to  three  plans  :  they  may  be  arranged  according  to  their  topographical  relations, 
according  to  their  physiological  significance,  or,  finally,  upon  a  morphological  basis, 
their  embryological  or  developmental  significance  forming  the  guide  for  their  arrange- 
ment in  groups.  In  the  following  pages  the  last-named  plan  will  be  followed  as  far 
as  possible. 

Embryologically  the  skeletal  muscles  are  formed,  for  the  most  part,  from  a  series 
of  segmentally  arranged  masses  of  mesoblast — the  mesoblastic  somites — which  appear 
at  an  early  stage  of  development  on  either  side  of  the  notochord  and  later  extend 
ventrally  towards  the  mid-ventral  line  (page  465).  That  portion  of  the  musculature 
which  has  such  an  origin  may  be  regarded  as  consisting  primarily  of  a  series  of  plates 
arranged  segmentally  along  each  side  of  the  body,  each  plate  corresponding  to  and 
being  supplied  by  one  of  the  segmental  nerves  and  by  those  fibres  of  it  which  arise 
from  the  cells  of  the  anterior  horn  of  the  spinal  cord  or  their  homologues  in  other 
portions  of  the  central  nervous  system.  A  diagrammatic  representation  of  this  mus- 
culature in  its  primary  condition  is  shown  in  Fig.  493,  and  from  this  it  will  be  per- 
ceived that  the  series  of  muscle-plates  extends  throughout  the  entire  trunk  and  neck 


472 


HUMAN   ANATOMY. 


Fig. 


493- 


regions  of  the  body  and  to  a  certain  extent  into  the  head  region,  there  being,  how- 
ever, in  this  last  region  a  considerable  area  in  which  the  muscle-plates  are  unrepre- 
sented. 

Throughout  this  area  of  the  head  region  muscles  occur  which  arise  in  relation 
to  the  branchial  arches  and,  accordingly,  in  a  much  more  ventral  position  than  the 
mesodermic  somites.  Furthermore,  these  muscles  are  supplied  by  branches  from 
the  mixed  cranial  nerves,  arising  from  cells  situated  in  a  portion  of  the  medulla 
oblongata  which  is  comparable  to  the  lateral  horn  of  the  spinal  cord  and  con- 
stituting what  are  termed  lateral  motor  roots,  in  contradistinction  to  the  median 
or  anterior  motor  roots  which  supply  the  muscles  derived  from  the  mesodermic 
somites. 

There  are  thus  two  sharply  defined  systems  of  musculature  :  the  one,  primarily 
confined  to  the  cranial  region,  is  supplied  by  lateral  motor  nerves,  and  from  its  rela- 
tion to  the  branchial  arches  may  be  termed  the  branchiomeric  musculature  ;  the  other, 

supplied  by  anterior  motor  nerves,  is  arranged 
primarily  in  a  series  of  segmental  (metameric) 
plates,  and  may  be  termed  the  metameric  mus- 
culature.  These  two  systems  constitute  the 
first  divisions  in  the  morphological  classifica- 
tion of  the  musculature. 

The  further  subdivision  of  the  branchio- 
meric muscles  is  most  conveniently  made  with 
reference  to  the  various  cranial  nerves  by 
which  they  are  supplied.  For  the  metameric 
musculature  a  more  complicated  subdivision  is 
both  necessary  and  convenient,  and  in  the  first 
place  it  may  be  divided  into  the  axial  and 
the  appendicular  musculature.  For  the  latter 
group,  which  includes  all  the  muscles  of  the 
limbs,  a  derivation  from  the  mesodermic  so- 
mites seems  probable,  outgrowths  from  certain 
somites  extending  into  the  limb-buds  when 
these  develop  ;  but  it  has  not  yet  been  possi- 
ble to  demonstrate  that  this  is  the  case,  the 
limb  muscles  really  making  their  appearance 
in  an  unsegmented  mass  of  mesoblast  in  the 
limb-bud  which  appears  to  have  no  connection 
with  the  mesoblastic  somites,  these  structures 
apparently  not  being  continued  into  the  limb- 
bud,  but  seeming  to  stop  short  at  its  base.  In- 
deed, it  is  quite  possible  that  the  limb  muscles 
should  not  be  included  under  the  metameric 
musculature  ;  but  until  it  is  demonstrated  that 
their  mode  of  development  is  not  a  secondary 
condensation  of  the  embryological  history,  it 
seems  preferable  to  retain  them  as  members  of 
that  group. 

The  later  development  of  the  cranial  mes- 
oblastic somites  is  somewhat  different  from  that  of  the  others,  and  it  is  consequently 
convenient  to  group  the  axial  muscles  derived  from  them  by  themselves.  And  since 
the  somites  form  in  the  embryo  two  clearly  defined  groups,  it  seems  well  to  place 
the  derived  muscles  in  two  groups  which  may  be  termed  respectively  the  orbital  and 
the  hypoglossal  groups. 

The  remaining  somites,  which  may  be  grouped  together  as  the  trunk  somites,  in 
their  later  development  undergo  numerous  modifications,  some  of  which  may  be 
regarded  as  fundamental  and  primarily  affecting  all  of  the  series,  and  thus  affording 
a  basis  for  a  further  subdivision.  The  most  fundamental  of  these  modifications  is  a 
division  of  each  somite  into  a  dorsal  and  a  ventral  portion,  corresponding  respectively 
to  the  primary  divisions  of  the  spinal  nerves,  and  permitting  the  recognition  of  a 


Diagram  showing  grouping  of  head  and  trunk 
myotomes.  Ill,  IV,  VI,  orbital  group  (supplied  by 
cranial  nerves  indicated  by  Roman  numerals)  rep- 
resenting persisting  first  three  cephalic  myotomes; 
XII,  hypoglossal  group,  representing  persisting 
last  three  cephalic  myotomes,  intervening  ones 
having  disappeared;  i,  i,  i,  i,  i,  first  myotome  of 
cervical,  ^thoracic,  lumbar,  sacral,  and  coccygeal 
groups  of  trunk  myotomes.  Each  myotome  is  di- 
vided into  dorsal  and  ventral  segments. 


GENERAL   CONSIDERATION   OF   THE  VOLUNTARY   MUSCLES.    473 


Diagrammatii 


ing  primary  groups  ( 


dorsal  and  a  ventral  group  of  trunk  muscles.  The  portions  of  the  ventral  divisions 
on  either  side  of  the  mid-ventral  line  separate  to  form  a  subordinate  group  of  mus- 
cles which  may  be  termed  the  rec- 
tus group  (Fig.  494),  the  more  Fig.  494. 
lateral  portions  giving  rise  to  a 
group  which,  from  the  prevailing 
oblique  course  of  its  fibres,  may 
be  termed  the  obliquus  group ; 
and,  finally,  from  the  more  dor- 
sal portions  of  the  ventral  muscu- 
lature there  are  developed  in  cer- 
tain regions  of  the  body  muscles 
which  lie  ventral  to  the  bodies 
or  processes  of  the  vertebrae,  and 
may  be  termed  the  hyposkeletal 
muscles,  in  contrast  to  the  re- 
maining musculature  which  ex- 
tends between  the  skeletal  ele- 
ments or  lies  dorsal  to  them,  and 
hence  is  termed  the  episkeletal  mus- 
culature. 

To   sum  up  the  classification 
proposed  it  may  be  represented  in  the  following  manner  : 

I.  Branchiomeric  Muscles. 
II.   Metameric  Muscles. 

A.  Axial  Muscles. 

1.  Orbital  muscles. 

2.  Hypoglossal  muscles. 

3.  Trunk  muscles. 

a.  Dorsal, 

b.  Ventral. 

a.  Rectus  set. 

b.  Obliquus  set. 

c.  Hyposkeletal  set. 

B.  Appendicular  Muscles. 

Nerve-Supply. — The  segmental  regularity  of  the  mesodermic  somites  is  but 
slightly  retained  in  the  adult,  numerous  modifications,  such  as  fusion,  tangential  and 
longitudinal  splitting,  migration,  and  even  obliteration  taking  place  in  them  to  pro- 
duce the  various  muscles  of  the  adult.  The  various  modifications  have  not  in  all 
cases  been  traced,  but  a  study  of  the  nerve-supply  of  a  muscle  gives  in  many,  if  not 
all,  cases  an  important  clue  to  its  origin.  This  depends  upon  the  fact  that  the 
muscles  may  be  regarded  as  the  end-organs  of  the  motor  nerves,  and  that  the  seg- 
mental relation  established  in  the' embryo  between  a  nerve  and  the  muscle-tissue 
derived  from  a  given  mesodermic  somite  is  not  disturbed  in  later  development,  no 
matter  what  changes  of  relation  the  muscle-tissue  may  undergo.  Thus,  when  a 
muscle,  such  as  the  rectus  abdominis,  is  found  to  be  supplied  by  a  number  of  spinal 
nerves,  it  is  because  it  has  been  formed  by  the  fusion  of  portions  of  a  corresponding- 
number  of  mesodermic  somites  ;  and  when  a  muscle,  such  as  the  latissimus  dorsi, 
lying  mainly  in  the  lumbar  region,  is  found  to  be  supplied  by  a  cervical  nerve,  it  is 
because  it  has  wandered  from  its  original  point  of  formation  in  the  cervical  region. 

Variations  in  the  nerve-supply  are  occasionally  seen,  especially  in  the  limb  mus- 
cles; but  it  seems  probable  that  such  variations  are  only  apparent,  the  nerve-fibres 
supplying  the  muscle  being  in  all  cases  strictly  equivalent,  arising  from  the  same 
region  of  the  spinal  cord,  even  although  they  may  pursue  in  different  individuals 
somewhat  different  paths  in  order  to  reach  their  destination.  Thus,  a  muscle  which 
normally  is  supplied  by  fibres  from  the  median  nerve  may  sometimes  be  found  to  be 


474  HUMAN   ANATOMY. 

supplied  by  the  ulnar  nerve,  the  nerve-fibres  using  the  ulnar  nerve  as  a  pathway  by 
which  to  reach  their  destination,  instead  of  the  median  nerve. 

It  is  important,  therefore,  both  from  the  morphological  and  clinical  stand-points, 
that  not  only  should  the  nerve  along  which  the  fibres  pass  to  reach  their  destination 
be  known,  but  also  the  nerve-roots  by  which  they  issue  from  the  central  nervous 
system. 


THE   BRANCHIOMERIC  MUSCLES. 

The  branchiomeric  muscles  are  those  skeletal  muscles  which  are  derived  from 
the  mesoderm  associated  with  the  branchial  arches,  and  are  supplied  by  those  cranial 
nerves  whose  motor  fibres  constitute  what  are  termed  lateral  motor  roots.  These 
nerves  are  the  trigeminus,  facialis,  and  glossopharyngeo-vago-accessorius  groups, 
and  the  classification  of  the  muscles  may  well  be  according  to  their  innervation  Dy 
these  three  nerve-groups. 

I.     THE   TRIGEMINAL   MUSCLES. 

The  trigeminal  muscles  stand  in  relation  primarily  to  the  first  embryonic  or  jaw- 
arch,  and  in  the  adult  to  the  structures  developed  in  association  with  this, — i.e.,  to 
the  mandible  and  the  malleus.  The  mandibular  muscles  are  represented  by  the 
muscles  of  mastication  and  two  muscles,  the  mylo-hyoid  and  the  anterior  belly  of 
the  digastric,  which  extend  between  the  mandible  and  the  hyoid  bone,  and  may  be 
termed  the  .submental  muscles.  Connected  with  the  malleus  is  a  single  muscle,  the 
tensor  tympani,  and  an  additional  trigeminal  muscle  is  found  in  association  with  the 
soft  palate,  the  tensor  palati. 

(a)  THE  MUSCLES   OF  MASTICATION. 

1.  Masseter.  3.    Pterygoideus  Externus. 

2.  Temporalis.  4.    Pterygoideus  Interims. 

1.   Masseter  (Fig.  495). 

The  masseter  is  a  strong  quadrilateral  muscle  composed  of  two  portions,  sep- 
arated at  Jheir  origin  and  posteriorly  by  a  quantity  of  loose  areolar  tissue,  but 
united  towards  their  insertion  into  the  mandible. 

Attachments. — The  superficial  portion  arises  by  a  strong  aponeurosis  from 
the  anterior  two-thirds  of  the  lower  border  of  the  zygoma,  while  the  deeper  part 
arises  directly  from  the  posterior  third  of  the  lower  border  and  the  whole  of  the  inner 
surface  of  the  zygoma.  The  fibres  of  the  superficial  portion  pass  downward  and 
slightly  backward  to  be  inserted  into  the  outer  surface  of  the  angle  of  the  mandible, 
while  those  of  the  deeper  portion  pass  more  directly  downward  and  are  inserted  into 
the  outer  surface  of  the  ascending  ramus  as  high  as  the  bases  of  the  articular  and 
coronoid  processes,  encroaching  to  a  certain  extent  upon  the  insertion  of  the  temporal 
muscle. 

Nerve-Supply. — By  the  masseteric  branch  of  the  anterior  portion  of  the  man- 
dibular division  of  the  trigeminus. 

Action. — To  raise  the  mandible  and,  by  its  superficial  portion,  to  draw  it  for- 
ward to  a  slight  extent.  Owing  to  the  fibres  of  the  muscle  being  directed  almost 
perpendicularly  to  the  lever  upon  which  it  acts,  the  masseter  works  at  much  less 
mechanical  disadvantage  than  is  usual,  and  its  action  is  therefore  exceedingly  powerful. 

Relations. — A  considerable  portion  of  the  masseter  is  subcutaneous.  Poste- 
riorly, however,  the  parotid  gland  rests  upon  its  outer  surface,  and  it  is  crossed  by 
the  parotid  duct,  the  transverse  facial  artery,  and  branches  of  the  facial  nerve. 
Anteriorly  its  deep  surface  is  separated  from  the  buccinator  muscle  by  a  well-devel- 
oped mass  of  fat,  the  buccal  fat-pad  fpage  489). 

The  Parotideo- Masseteric  Fascia. — Covering  the  anterior  surface  of  the 
masseter  is  a  thin  layer  of  fascia,  the  masseteric  fascia,  attached  above  to  the  zygoma 


THE   TRIGEMINAL    MUSCLES. 


475 


and  fading  out  anteriorly  beneath  the  facial  muscles.  Posteriorly  it  becomes  thicker 
and  divides  into  two  layers  to  enclose  the  parotid  gland  (parotid  fascia),  the  super- 
ficial layer  becoming  continuous  behind  with  the  layer  of  the  deep  cervical  fascia 
which  encloses  the  sterno-mastoid  muscle,  while  the  deeper  layer  is  connected  inter- 
nally with  the  styloid  process  and  joins  the  deep  cervical  fascia  below.  A  thickening 
of  this  deeper  layer  forms  a  flat  band,  the  stylo-mandibular  ligament,  which  passes 
downward  and  outward  from  the  styloid  process  to  the  angle  of  the  jaw. 

2.  Temporalis  (Fig.  495). 

The  temporal  fascia  forms  a  strong  aponeurotic  membrane  attached  above  to  the 
superior  temporal  line  and  the  portion  of  bone  between  this  and  the  inferior  line, 
being  along  this  attachment  continuous  with  the  periosteum.  Below  it  divides  into 
two  layers  which  are  separated  by  a  quantity  of  adipose  tissue,  through  which  the 


Fig.  495. 


Masseter,  superficial  port! 


Lateral  aspect  of  skull  with  temporal,  masseter,  buccinator,  and  oral  muscles  in  place. 


middle  temporal  artery  may  run,  and  is  attached  to  the  zygoma,  its  superficial  layer 
inserting  into  the  upper  border  of  the  arch  and  its  deeper  layer  into  the  inner  surface. 

Attachments. — The  temporal  muscle  arises  from  the  upper  half  of  the  deep 
surface  of  the  temporal  fascia  and  from  the  whole  extent  of  the  floor  of  the  temporal 
fossa.  Its  fibres  converge  to  an  exceedingly  strong  tendon,  which  inserts  into  the 
coronoid  process  of  the  mandible,  occupying  both  its  borders,  the  whole  of  its  inner 
surface,  and  a  varying  amount  of  its  outer  surface. 

Nerve-Supply. — By  the  anterior  and  posterior  deep  temporal  branches  from 
the  anterior  portion  of  the  mandibular  division  of  the  trigeminus. 

Action. — To  raise  the  mandible.  The  more  posterior  fibres  serve  to  retract 
the  jaw,  acting  thus  as  an  antagonist  of  the  external  pterygoid. 


476 


HUMAN  ANATOMY. 


Relations. — Superficial  to  the  temporal  fascia  are  branches  of  the  superficial 
temporal  vessels  and  the  auriculotemporal  nerve.  Beneath,  the  muscle  is  in  relation 
to  the  internal  maxillary  artery  and  the  external  pterygoid  muscle. 

3.   Pterygoideus  Externus  (Fig.  496). 

Attachments. — The  external  pterygoid  arises  by  two  heads.  The  upper 
head  takes  its  origin  from  the  under  surface  of  the  great  wing  of  the  sphenoid,  inter- 
nal to  the  infratemporal  crest  (pterygoid  ridge),  while  the  lower  head  arises  from 
the  outer  surface  of  the  lateral  pterygoid  plate.  The  two  heads  are  at  first  separated 
by  a  narrow  triangular  interval  through  which  the  internal  maxillary  artery  passes, 
but,  passing  backward  and  outward,  they  soon  unite  to  be  inserted  into  the  anterior 
border  of  the  interarticular  fibro-cartilage  of  the  mandibular  articulation  and  into  the 

neck  of  the  condyloid  process  of  the 


Fig.  496. 


mandible. 

Nerve-Supply. — By  the  exter- 
nal pterygoid  branch  of  the  anterior 
portion  of  the  mandibular  division  of 
the  trigeminus. 

Action. — When  both  muscles 
act  together,  they  draw  the  jaw  and 
the  interarticular  fibro-cartilage  for- 
ward, a  movement  which  always 
accompanies  and  assists  in  the  de- 
pression of  the  jaw.  When  but  one 
muscle  acts,  the  ramus  to  which  it  is 
attached  is  drawn  forward,  while  the 
other  pivots  in  its  articular  surface, 
the  result  being  an  apparent  lateral 
movement  of  the  jaw  towards  the 
pivotal  side. 

Relations. — The  outer  surface 
of  the  external  pterygoid  is  in  rela- 
tion to  the  coronoid  process  of  the 
mandible  and  the  temporal  muscle, 
its  lower  head  is  frequently  crossed  by  the  internal  maxillary  artery  and  the  buccal 
nerve,  and  anteriorly  it  is  separated  from  the  masseter  by  the  buccal  fat-pad.  The 
deep  surface  rests  upon  the  upper  part  of  the  internal  pterygoid  muscle,  and  is  in 
relation  to  the  internal  maxillary  artery  and  the  inferior  dental  and  lingual  branches 
of   the  mandibular  division  of  the  trigeminus. 


Temporal  bone  (cut) 


-Condyle 


Upper  head)  External 
xLo\ver  head     /  pterygoid 


Internal  pterygoid 


Mylo-hyoid,  stump 
internal  pterygoid  muscle 


4.   Pterygoideus  Internus  (Fig.  496). 

Attachments. — The  internal  pterygoid  arises  from  the  walls  and  floor  of  the 
pterygoid  fossa,  the  majority  of  its  fibres  being  attached  to  the  inner  surface  of  the 
external  pterygoid  plate  and  to  the  tuberosity  of  the  palate  bone.  A  smaller  bundle 
of  fibres,  forming  what  may  be  termed  a  second  head,  separated  from  the  main  por- 
tion of  the  muscle  by  the  lower  head  of  the  external  pterygoid,  frequently  arises 
from  the  tuberosity  of  the  maxilla  and  the  adjacent  portion  of  the  palate  bone. 
From  these  origins  the  fibres  are  directed  downward  and  somewhat  outward  and 
backward  to  be  inserted  into  the  inner  surface  of  the  angle  and  ramus  of  the  mandi- 
ble below  the  mylo-hyoid  groove. 

Nerve-Supply. — By  the  internal  pterygoid  branch  from  the  trunk  of  the 
mandibular  division  of  the  trigeminus. 

Action. — Its  chief  action  is  to  raise  the  jaw,  having  in  this  respect  almost  as 
powerful  action  as  the  masseter.  Owing  to  the  direction  of  its  fibres,  it  will  also 
assist  the  external  pterygoid  in  protruding  the  jaw  and  in  producing  its  lateral 
movements. 

Relations. — The  outer  surface  of  the  muscle  is  in  relation  with  the  ramus  of 
the  mandible,  the  internal  maxillary  artery,  and  the  inferior  dental  and  lingual  nerves 


THE  TRIGEMINAL   MUSCLES.  477 

passing  between  the  muscle  and  the  bone.  Above  its  larger  head  is  covered  by  the 
external  pterygoid.  Its  inner  surface  is  in  contact  above  with  the  tensor  palati,  the 
superior  constrictor  of  the  pharynx,  and  the  ascending  palatine  artery,  while  towards 
its  insertion  it  is  in  relation  with  the  stylo-hyoid  and  posterior  belly  of  the  digastric 
and  with  the  submaxillary  gland. 

Variations  of  the  Muscles  of  Mastication. — The  muscles  of  mastication  are  all  derivatives 
of  a  single  muscular  mass  represented  by  the  adductor  mandibular  of  fishes,  and  indications 
of  their  common  origin  are  not  infrequently  to  be  seen  in  partial  unions  of  the  various  muscles. 
Thus,  fibres  from  the  posterior  portion  of  the  deeper  head  of  the  masseter  may  join  the  tem- 
poral, fibres  from  both  the  temporal  and  masseter  sometimes  pass  to  the  anterior  border  of  the 
fibro-cartilage  of  the  mandibular  articulation,  and  connections  have  also  been  observed  between 
the  temporal  and  the  external  pterygoid. 

Additional  independent  muscles  apparently  belonging  to  this  group  sometimes  occur  in 
the  pterygoideus  proprius,  which  extends  from  the  infratemporal  crest  of  the  sphenoid  to  the 
posterior  edge  of  the  external  pterygoid  plate,  and  in  the  pterygo-spinosus,  which  has  for  its 
attachments  the  spine  of  the  sphenoid  and  the  posterior  border  of  the  external  pterygoid  plate. 
The  significance  of  these  muscles  passing  between  points  which  are  immovable  is  somewhat 
obscure.  The  close  relationship  which  the  pterygo-spinosus  bears  to  the  spheno-mandibular 
ligament  seems  to  indicate  that  it  represents  the  musculature  of  that  portion  of  the  mandibular 
arch  which  has  become  transformed  into  the  ligament,  and  that  usually  it  is  represented  by  the 
connective  tissue  enclosing  the  ligament. 

(b)  THE   SUBMENTAL   MUSCLES. 

i.    Mylo-hyoideus.  2.    Digastricus  (Anterior  Belly). 

This  group  of  trigeminal  muscles  contains  but  two  representatives,  the  mylo- 
hyoid and  the  anterior  belly  of  the  digastric.  This  latter  muscle,  as  ordinarily 
described,  consists  of  two  distinct  muscles  united  at  their  attachment  to  the  hyoid 
bone,  the  anterior  of  the  two  muscles  belonging  to  the  trigeminal  group,  while  the 
posterior  is  a  member  of  the  facial  group.  It  will  be  convenient  to  describe  the 
muscle  as  a  whole,  even  although  it  belongs  only  in  part  to  the  group  under  con- 
sideration. 

1.   Mylo-Hyoideus  (Fig.  497). 

Attachments. — The  mylo-hyoid  a  rises  from  practically  the  entire  length  of  the 
mylo-hyoid  ridge  of  the  mandible,  from  which  the  fibres  pass  inward  and  slightly 
backward  to  be  inserted  for  the  most  part  into  a  median  fibrous  raphe  common  to 
the  two  muscles  of  opposite  sides,  the  posterior  fibres,  however,  being  attached  to 
the  upper  border  of  the  body  of  the  hyoid  bone.  The  two  muscles,  taken  together, 
form  a  muscular  floor  for  the  mouth,  the  diaphragma  oris,  upon  which  the  tongue 
may  be  said  to  rest. 

Nerve-Supply. — By  the  mylo-hyoid  from  the  inferior  dental  branch  of  the 
mandibular  division  of  the  trigeminus. 

Action. — To  draw  the  hyoid  bone  upward  and  at  the  same  time  to  raise  the 
floor  of  the  mouth,  pressing  the  tongue  against  the  palate. 

Relations. — The  superficial  surface  of  the  mylo-hyoid  is  in  relation  with  the 
anterior  belly  of  the  digastric  and  with  the  facial  artery.  The  submaxillary  gland 
curves  around  its  posterior  free  margin  and  is  thus  in  relation  with  both  its  surfaces, 
the  submaxillary  duct  running  forward  upon  its  deeper  surface.  This  latter  surface 
is  also  in  relation  with  the  genio-hyoid,  genio-glossal,  hyo-glossal,  and  stylo-glossal 
muscles,  with  the  sublingual  gland,  and  with  the  lingual  branch  of  the  trigeminus 
and  the  hypoglossal  nerve. 

2.   Digastricus  (Figs.  497,  502). 

Attachments. — The  digastric,  as  its  name  indicates,  consists  of  two  bellies 
which  are  united  by  a  strong  cylindrical  tendon.  The  anterior  belly,  which  alone 
belongs  to  the  trigeminal  group  of  muscles,  arises  from  the  digastric  fossa  of  the 
mandible,  and  is  directed  downward,  backward,  and  slightly  outward  to  become  con- 


478 


HUMAN   ANATOMY. 


tinuous  with  the  intermediate  tendon.  This  is  bound  down  to  the  greater  horn  and 
body  of  the  hyoid  bone  by  a  pulley-like  band  of  the  cervical  fascia  and  to  a  certain 
extent  by  the  stylo-hyoid  muscle,  which  divides  near  its  insertion  into  the  hyoid  into 
two  slips,  between  which  the  tendon  of  the  digastric  passes. 

The  posterior  belly  (Fig.  502)  takes  its  origin  from  the  mastoid  groove  of  the 
temporal  bone,  and  passes  downward  and  forward  to  become  connected  with  the 
intermediate  tendon. 

Nerve-Supply. — The  anterior  belly  is  supplied  by  the  mylo-hyoid  nerve  from 
the  inferior  dental  branch  of  the  mandibular  division  of  the  trigeminus,  the  posterior 
belly  by  the  digastric  branch  of  the  facial. 

Action. — The  digastric  either  raises  the  hyoid  bone  or  depresses  the  jaw, 


Fig.  497. 


-hyoid 

lo-hyoid  removed) 


Fascial  loop  binding 
.tendons  to  hyoid  bone 


Thyro-hyoid  memb 

Stylo-glossus- 
Internal  pterygoid- 

Thyro-hyoid 
Thyroid  cartilage- 
-Stylo-pharyngeus 


Crico-thyroid 


Digastric, 
posterior  belly 


l«il     LThyroid  gland 


Submental  muscles  from  below ;  trachea  has  been  displaced  downward  and  backward. 

according  as  one  or  other  of  the  bones  is  fixed  by  the  antagonizing  muscles.  By  raising 
the  hyoid  when  the  mandible  is  fixed,  it  assists  the  mylo-hyoid  in  pressing  the  tongue 
against  the  palate  during  the  first  portion  of  the  act  of  deglutition,  and  in  the  second 
portion  of  that  act  the  posterior  belly  will  assist  the  stylo-hyoid  in  drawing  the  hyoid 
upward  and  backward  and  so  help  in  elevating  the  larynx. 

Relations. — The  anterior  belly  rests  upon  the  mylo-hyoid  muscle.  The  pos- 
terior belly  is  covered  by  the  sterno-mastoid  and  splenius  muscles,  and  crosses  both 
the  external  and  internal  carotid  arteries,  the  internal  jugular  vein,  and  the  pneumo- 
gastric  and  spinal  accessory  nerves. 


Variations. — A  close  relationship  exists  between  the  mylo-hyoid  and  the  anterior  belly  of 
the  digastric,  and  there  is  usually  more  or  less  exchange  of  fibres  between  the  two  muscles, 
sometimes  amounting  to  a  complete  fusion.     A  duplicity  of  the  anterior  belly  is  a  rather  fre- 


THE   FACIAL   MUSCLES.  479 

quent  variation,  and  the  anterior  bellies  of  opposite  sides  may  be  united  by  the  more  or  less- 
complete  conversion  of  the  fascia  which  typically  passes  between  them  into  muscular  tissue. 
An  independent  muscle  extending  between  the  body  of  the  hyoid  and  the  symphysis  of  the 
mandible,  and  termed  the  mento-hyoid,  occasionally  is  found  running  alongside  of  the  medial 
border  of  the  anterior  belly,  and  is  to  be  regarded  as  a  separated  portion  of  that  muscle. 

As  regards  the  posterior  belly,  it  may  take  its  origin  from  any  part  of  the  mastoid  groove 
or  even  from  the  outer  portion  of  the  superior  nuchal  line,  and  occasionally  it  fuses  completely 
with  the  stylo-hyoid.  In  certain  cases  in  which  there  is  a  failure  of  the  anterior  belly  to  differ- 
entiate from  the  mylohyoid,  the  posterior  belly  is  inserted  into  the  angle  of  the  mandible 
instead  of  into  the  hyoid  bone, — a  condition  recalling  the  arrangement  typical  in  the  majority 
of  the  mammalia,  in  which  the  posterior  belly  of  the  digastric  is  represented  by  a  depressor 
mandibults. 

(c)   THE   TRIGEMINAL   PALATAL   MUSCLE. 
1.  Tensor  Palati  (Fig.  509). 

Attachments. — The  tensor  palati  (tensor  veli  palatini)  takes  its  origin  from 
the  scaphoid  fossa  and  spine  of  the  sphenoid  and  from  the  outer  surface  of  the  car- 
tilaginous portion  of  the  Eustachian  tube.  It  descends  along  the  outer  surface  of  the 
internal  pterygoid  plate,  and,  becoming  tendinous,  bends  at  right  angles  around  the 
hamulus  and  is  continued  inward  to  be  inserted  into  the  posterior  border  of  the  palate 
bone  and  into  the  aponeurosis  of  the  soft  palate. 

Nerve-Supply. — By  fibres  from  the  mandibular  division  of  the  trigeminus,. 
which  traverse  the  otic  ganglion. 

Action. — It  tends  to  draw  the  soft  palate  to  one  side.  The  two  muscles  acting 
together  will  stretch  the  soft  palate. 

(d)   THE  TRIGEMINAL  TYMPANIC   MUSCLE. 

I.  Tensor  Tympani  (Fig.  1252). 

Attachments. — The  tensor  tympani  is  a  small  bipenniform  muscle  which  lies 
in  a  bony  canal  situated  above  the  Eustachian  tube.  Its  fibres  take  their  origin  from 
the  cartilaginous  portion  of  the  Eustachian  tube,  the  adjacent  portions  of  the  great  wing 
of  the  sphenoid,  and  also  to  a  certain  extent  from  the  walls  of  the  bony  canal.  The 
tympanic  end  of  the  Eustachian  tube  is  separated  from  the  opening  of  the  canal  for 
the  tensor  by  a  bony  ridge,  the  processus  cochleariformis,  over  which  the  tendon  of 
the  tensor  bends  almost  at  right  angles  and  passes  outward  across  the  tympanic 
cavity  to  be  inserted  into  the  manubrium  mallei  near  its  attachment  to  the  head  of  the 
bone. 

Nerve-Supply. — By  fibres  from  the  mandibular  division  of  the  trigeminus, 
which  traverse  the  otic  ganglion. 

Action. — The  muscle  draws  the  handle  of  the  malleus  inward  and  so  tenses 
the  membrana  tympani. 

II.  THE   FACIAL   MUSCLES. 

The  muscles  supplied  by  the  facial  nerve  are  readily  divisible  into  two  groups. 
Primarily  this  musculature  is  associated  with  the  second  branchial  or  hyoid  arch, 
represented  in  the  adult  by  the  lesser  cornu  of  the  hyoid  bone,  the  stylo-hyoid  liga- 
ment, styloid  process,  and  stapes,  and  a  small  group  of  muscles — the  stylo-hyoid,  the 
posterior  belly  of  the  digastric,  and  the  stapedius — are  still  found  in  relation  to  these 
structures.  From  the  surface  of  the  mass  from  which  these  muscles  differentiate 
there  is  separated  at  an  early  stage  a  layer  which  gradually  increases  in  extent  and 
eventually  covers  all  the  neck  and  head  in  a  cowl,  as  it  were,  its  progress  from  the 
hyoid  arch  being  followed  by  a  branch  of  the  facial  nerve,  which  eventually,  with  the 
growth  of  the  muscle,  increases  to  such  an  extent  as  to  appear  to  be  the  main  stem 
of  the  nerve.  From  the  muscular  sheet  numerous  superficial  muscles  of  the  head 
and  neck  develop,  and  the  entire  group  so  formed  may  be  termed,  from  one  of  its 
principal  members,  the  platysma  group,  the  group  retaining  the  primary  relationships 
forming  the  hyoidean  group. 


480  HUMAN    ANATOMY. 

(a)  THE   HYOIDEAN   MUSCLES. 

i.   Stylo-hyoideus.      2.    Digastricus  (Posterior  Belly).      3.    Stapedius. 

1.   Stylo-Hyoideus  (Figs.  497,  502). 

Attachments. — The  stylo-hyoid  forms  a  slender  spindle-shaped  muscle  which 
arises  from  the  upper  portion  of  the  styloid  process  and  passes  obliquely  downward 
and  forward  to  be  inserted  into  the  base  of  the  greater,  cornu  of  the  hyoid  bone, 
usually  dividing  before  its  insertion  into  two  slips,  between  which  the  intermediate 
tendon  of  the  digastric  passes. 

Nerve-Supply. — By  a  branch  from  the  digastric  branch  of  the  facial  nerve. 

Action. — To  raise  and  draw  backward  the  hyoid  bone. 

Relations. — Above  the  stylo-hyoid  descends  along  the  inner  border  of  the 
posterior  belly  of  the  digastric,  passing  in  front  of  that  muscle  below.  Internal  to 
it  is  the  stylo-pharyngeus,  and  below  the  hyo-glossus  and  the  glossopharyngeal  and 
hypoglossal  nerves,  passing  forward  between  it  and  the  stylo-pharyngeus. 

2.    Digastricus   (Posterior  Belly).     See  page  478. 
3.  Stapedius  (Fig.  1254). 

Attachments. — The  stapedius  arises  from  the  walls  of  the  cavity  contained 
within  the  pyramidal  eminence,  and  its  tendon,  entering  the  tympanic  cavity  through 
the  aperture  at  the  apex  of  the  eminence,  is  inserted  into  the  neck  of  the  stapes. 

Nerve-Supply. — By  a  small  branch  arising  from  the  facial  nerve  during  its 
course  through  the  lower  part  of  the  facial  (Fallopian)  canal. 

Action. — By  its  contraction  it  draws  the  head  of  the  stapes  towards  the  pos- 
terior wall  of  the  tympanic  cavity,  depressing  the  posterior  part  of  the  foot-plate  of 
the  bone  while  it  raises  the  anterior  part,  thus  tensing  the  membrane  which  closes 
the  fenestra  ovalis. 

Variations  of  the  Hyoidean  Muscles. — A  close  relationship  exists  between  the  stylo-hyoid 
and  the  posterior  belly  of  the  digastric,  the  one  or  the  other  occasionally  failing  to  separate 
from  the  common  mass  from  which  they  are  derived.  A  bundle  of  muscle-fibres  sometimes 
passes  from  the  tip  of  the  styloid  process  to  the  angle  of  the  mandible,  forming  what  may  be 
termed  the  stylo-mandibularis,  and  recalling  by  its  insertion  the  condition  presented  in  certain 
cases  by  the  posterior  belly  of  the  digastric  (page  479) . 

A  duplication  of  the  stylo-hyoid  has  also  been  observed,  the  second  slip,  which  has  been 
termed  the  stylo-hyoideus  profundus,  varying  considerably  in  its  insertion,  sometimes  accompa- 
nying the  stylo-hyoid  proper  and  sometimes  inserting  into  the  lesser  cornu  of  the  hyoid,  and  in 
some  cases  replacing  the  stvlo-hyoid  ligament. 

The  division  of  the  stylo-hyoid  near  its  insertion  for  the  passage  of  the  intermediate  tendon 
of  the  digastric  does  not  always  occur,  the  insertion  being  by  a  single  head  which  may  pass 
either  to  the  outer  or  the  inner  side  of  the  tendon. 


{5)    THE   PLATYSMA   MUSCLES. 


(a)   Superficial  Layer. 

Platysma. 
Occipito-frontalis. 
Auricularis  posterior. 
Auricularis  superior. 
Auricularis  anterior. 
Orbicularis  palpebrarum. 
Zygomaticus  major. 
Levator    labii    superioris 


9.    Depressor  labii  inferioris. 
Levator  menti. 


(b)   Deep  Layer. 

1.  Orbicularis  oris. 

2.  Nasalis    (compressor   nasi    et 

depressor  alse  nasi). 

3.  Levator  labii  superioris. 

4.  Levator  anguli  oris. 

5.  Risorius. 

6.  Depressor  anguli  oris. 

7.  Buccinator. 


The  comparative  and  embryological  study  of  the  platysma  muscles  have  shown 
their  origin  from  the  musculature  of  the  second  or  hyoid  arch  and  their  extension 


THE   FACIAL   MUSCLES. 


481 


thence  over  the  head  and  neck.  At  first  they  are  confined  entirely  to  the  neck  region, 
but  even  in  the  lower  mammals  the  extension  upon  the  head  has  begun,  and  in  the 
higher  members  of  this  group  two  portions  can  be  distinguished  in  the  muscle-sheet. 
The  more  superficial  of  these  is  situated  in  the  lateral  and  posterior  portions  of  the 
neck,  and  extends  thence  upon  the  sides  of  the  face  and  over  the  vertex  of  the  skull 
to  the  orbital  and  nasal  regions  of  the  face.  The  deeper  one  lies  more  anteriorly  in 
the  neck,  and  extends  upward  over  the  jaw  to  the  region  around  the  mouth. 

In  the  higher  forms  a  differentiation  of  both  layers  to  form  a  number  of  more 
or  less  separate  muscles  takes  place  and  reaches  its  highest  development  in  man, 
whose  mobility  of  facial  expression  is  due  to  the  existence  of  a  considerable  number 
of  platysma  muscles.  These  muscles  have  arisen  from  the  common  sheets  by  the 
partial  conversion  of  these  into  connective  tissue,  by  the  secondary  attachment  of 
portions  of  the  sheets  to  the  skeleton,  by  various  modifications  of  the  primary  direc- 
tion of  the  fibres,  and  by  the  obliteration  of  certain  portions  of  the  sheet  found  in  the 

Fig.  49S. 


Depressor  anguli  oris 

Mandible 
Raphe  of  mylo-hyoid 


Depressor  labii  inferioris 
Levator  menti 


Platysma-W 


Stern  o-mastoid 


Stern  o-thyroid' 


Superficfal  muscles  of  neck. 


lower  animals,  the  cervical  portion  of  the  deep  layer,  for  instance,  being  normally 
lacking  in  man,  the  layer  being  represented  only  by  the  muscles  of  the  lips. 

The  platysma  musculature  is  characterized  for  the  most  part  by  the  pale  color  of 
its  fibres,  by  their  aggregation  to  form  thin  bands  or  sheets  usually  more  or  less  inter- 
mingled with  connective-tissue  strands,  so  that  their  margins  are,  as  a  rule,  ill-defined, 
and  by  their  attachment  in  frequent  cases  to  the  integument.  These  peculiarities, 
together  with  a  considerable  amount  of  variation  which  occurs  in  the  differentiation  of 
the  various  muscles,  have  brought  about  not  a  little  difference  in  the  number  of  muscles 
recognized  in  the  group  by  various  authorities,  some  recognizing  as  distinct  muscles 
what  others  regard  as  merely  more  or  less  aberrant  or  unusually  developed  slips. 

(a)    THE   MUSCLES   OF   THE   SUPERFICIAL   LAYER. 
1.   Platysma  (Figs.  498,  499). 
Attachments. — The  platysma  takes  its  origin  from  the  skin  and  subcutaneous 
tissue  over  the  pectoralis  major  and  deltoid  muscles  on  a  line  extending  from  the  car- 
tilage of  the  second  rib  to  the  tip  of  the  acromion  process.      Its  fibres  are  directed 


482  HUMAN   ANATOMY. 

upward  and  inward  and  are  inserted  into  the  body  of  the  mandible  from  the  sym- 
physis to  the  insertion  of  the  masseter,  the  more  posterior  fibres  extending  upward 
upon  the  face  towards  the  angle  of  the  mouth  and  becoming  lost  partly  in  the  fascia 
of  the  cheeks  and  partly  among  the  muscles  of  the  lips. 

Nerve-Supply.- — By  the  inframandibular  branch  of  the  facial  nerye. 

Action. — The  contraction  of  the  platysma  results  in  drawing  the  lower  lip 
downward  and  outward  and  at  the  same  time  raising  the  skin  of  the  neck  from 
the  underlying  parts.  It  is  one  of  the  most  important  muscles  employed  in  the 
expression  of  horror  and  intense  surprise.  It  does  not  seem  probable  that  the 
muscle  has  much  effect  in  producing  depression  of  the  mandible,  an  action  which 
it  might  be  expected  to  possess  on  account  of  its  upper  attachment. 

Relations. — The  platysma  rests  upon  the  deep  fascia  of  the  neck  and  covers 
all  the  structures  at  the  front  and  sides  of  that  region.  Upon  its  deep  surface  lie  the 
external  jugular  vein,  the  superficial  lymph-nodes  of  the  neck,  and  the  superficial 
branches  of  the  cervical  plexus.  It  covers  also  the  sterno-mastoid  muscle  and  the 
depressors  of  the  hyoid  bone,  and,  above,  the  digastric  and  mylo-hyoid  muscles, 
together  with  the  submaxillary  gland  and  the  lower  portion  of  the  parotid. 

Variations. — There  is  usually  more  or  less  decussation  of  the  two  muscles  across  the 
median  line,  especially  in  their  upper  parts,  where,  indeed,  a  certain  amount  of  decussation  may 
be  considered  a  normal  condition.  The  muscle  is  subject  to  considerable  amounts  of  variation 
in  its  development,  sometimes  forming  a  very  thin,  pale  layer  largely  interspersed  with  connective 
tissue,  and  at  other  times  it  is  composed  of  strong,  deeply  colored  bundles  with  much  less  inter- 
mixture of  connective  tissue.  Its  extension  upon  the  face  may  also  vary  considerably,  some- 
times being  traceable  as  high  up  as  the  zygoma  and  extending  backward  to  behind  the  ear.  On 
the  other  hand,  it  may  be  very  considerably  reduced  in  size,  especially  below,  a  complete  absence 
of  the  lower  half  of  the  muscle  having  been  observed. 

2.   Occipito-Frontalis  (Fig.  499). 

Attachments. — The  occipito-frontalis  (m.  epicranius)  is  a  muscular  and  aponeu- 
rotic sheet  which  covers  the  entire  vertex  of  the  skull  from  the  occipital  region  to  the 
root  of  the  nose.  It  consists  of  two  muscular  portions,  one  of  which,  the  occipitalis, 
arises  from  the  superior  nuchal  line  and  inserts  after  a  short  course  into  the  posterior 
border  of  the  epicranial  aponeurosis,  while  the  other,  the  frontalis ,  taking  its  origin 
from  the  anterior  border  of  the  galea,  is  inserted  into  the  skin  in  the  neighborhood 
of  the  eyebrows,  over  the  glabella,  and  into  the  superciliary  arches,  a  portion  of  it 
being  frequently  prolonged  downward  upon  the  nasal  bone,  forming  what  has  been 
termed  the pyramidalis  nasi  (m.  procerus),  which  is  frequently  described  as  a  distinct 
muscle. 

The  epicranial  aponeurosis  (galea  aponeurotica)  (Fig.  499)  is  a  dense  aponeu- 
rotic sheet  which  covers  the  entire  vertex  of  the  cranium  and  is  prolonged  laterally 
over  the  temporal  fascia  as  a  thin  layer  which  extends  almost  to  the  zygoma.  On 
its  superficial  surface  it  is  intimately  associated  with  the  integument,  being  united  to 
its  deeper  surface  by  a  thin  but  close  and  resistant  layer  of  fascia  which  represents 
the  superficial  fascia  of  other  regions  of  the  body  and  in  which  are  embedded  the 
vessels  and  nerves  of  the  scalp.  The  under  surface  of  the  galea  is,  however,  smooth, 
and  is  connected  with  the  periosteum  by  a  lax  layer  of  connective  tissue,  so  that  it  is 
capable  of  considerable  movement  to  and  fro  upon  the  periosteum,  the  skin  being 
carried  with  it  in  such  movements.  A  section  through  the  scalp  at  the  vertex  would 
show  from  without  inward  ( 1 )  the  skin,  (2)  the  dense  superficial  fascia  with  its  vessels 
and  nerves,  (3)  the  epicranial  aponeurosis,  (4)  loose  connective  tissue,  and  (5) 
periosteum  (Fig.  504). 

Nerve-Supply. — The  occipitalis  is  supplied  by  branches  from  the  posterior 
auricular  branch  of  the  facial  the  frontalis  by  branches  from  the  rami  temporales  of 
the  same  nerve. 

Action. — The  occipitalis  acting  alone  will  draw  backward  the  galea  aponeurotica, 
while  the  frontalis  draws  it  forward.  If,  however,  the  galea  be  fixed  by  the  occipitales, 
the  action  of  the  frontales  is  to  raise  the  eyebrows  and  throw  the  skin  of  the  forehead 
into  transverse  wrinkles,  both  of  these  actions  being  greatly  increased  by  the  simul- 
taneous contraction  of  both  the  occipitales  and  the  frontales.      It  is  consequently  the 


THE   FACIAL   MUSCLES. 


483 


muscle  employed  in  the  expression  of  interrogation  and  surprise  and  also,  in  con- 
junction with  the  platysma,  in  that  of  horror. 

The  transversus  nuchtz  is  a  thin  muscular  band,  frequently  present,  arising  from  the 
occipital  protuberance  and  extending  laterally  to  terminate  in  various  attachments  ;  sometimes, 
for  instance,  uniting  with  the  posterior  border  of  the  sterno-cleido-mastoid  or  with  the  auricu- 
laris  posterior.  It  may  take  its  origin  either  superficial  to  or  beneath  the  attachment  of  the 
trapezius  to  the  superior  nuchal  line,  and  in  the  former  case  is  to  be  regarded  as  a  portion  of  the 
platysma  group  of  muscles,  while  in  the  latter  it  is  more  prpbably  a  relic  of  the  primary  con- 
nection between  the  trapezius  and  the  sterno-cleido-mastoid  and  belongs  to  that  group  of 
muscles  (page  501). 

3.  Auricularis  Posterior  (Fig.  499). 

Attachments. — The  posterior  auricular  {retrahens  aureni)  is  composed  of  a  few 
bundles  of  fibres  which  arise  from  the  outer  extremity  of  the  superior  nuchal  line  and 
the  base  of  the  mastoid  process  and  pass  horizontally  forward  to  be  inserted  into  the 
posterior  surface  of  the  concha.  It  is  frequently  imperfectly  separated  from  the 
occipitalis. 

Nerve-Supply. — By  the  posterior  auricular  branch  of  the  facial  nerve. 

Action. — To  draw  the  auricle  backward. 

Fig.  499. 


Auricularis  superior 


Occipitalis 
Auricularis  anterior 


Auricularis  posteri 

Zygomaticus  major 
Zygomaticus 

Levator  anguli  oris 

Levator  labii  superioris 

Buccinator 

Risorius 


Corrugator  supercilii 
Orbicularis  palpebrarum 
Orbital  part  of  same  muscle 
Pyramidalis  nasi 

Lev.  labii  sup.  alseque  n 
Compressor  narium 

Dilatores  naris 

Depressor  alas  nasi 

Orbicularis  oris 

Depressor  anguli  oris 
Depressor  labii  inferioris 
Levator  menti 


Superficial  dissection  of  head,  showing  platysma  muscles. 

4.  Auricularis  Superior  (Fig.  499). 

Attachments. — The  superior  auricular  (attollens  aureni)  is  a  triangular  muscle 
which  arises  from  the  lateral  portion  of  the  galea  aponeurotica  or  from  the  temporal 
fascia  and  converges  to  be  inserted  into  the  upper  part  of  the  cartilage  of  the 
auricle. 

Nerve-Supply. — By  fibres  from  the  rami  temporales  of  the  facial  nerve. 

Action. — To  draw  the  auricle  upward. 


5.  Auricularis  Anterior  (Fig.  499). 

Attachments. — The  anterior  auricular  {attrahens  aureni)  is  frequently  con- 
tinuous with  the  preceding  muscle,  lying  immediately  anterior  to  it.  It  arises  from 
the  lateral  part  of  the  galea  aponeurotica  or  from  the  temporal  fascia  and  is  inserted 
into  the  upper  anterior  part  of  the  auricular  cartilage  or  into  the  fascia  immediately 
anterior  to  the  cartilage. 


484  HUMAN   ANATOMY. 

Nerve-Supply. — By  fibres  from  the  rami  temporales  of  the  facial  nerve. 
Action. — To  draw  the  auricle  upward  and  forward. 

,6.   Orbicularis  Palpebrarum  (Figs.  499,  500). 

The  orbicularis  palpebrarum  (m.  orbicularis  oculi)  is  an  elliptical  sheet  whose 
fibres  have  their  origin  in  the  neighborhood  of  the  inner  angle  of  the  eye  and  curve 
thence,  some  upward  and  outward  and  some  downward  and  outward,  around  the 
rima  palpebralis  to  terminate  in  the  neighborhood  of  the  external  angle.  The  course 
of  the  fibres  lies  partly  in  the  substance  of  the  upper  and  lower  eyelids  and  partly  over 
the  bones  surrounding  the  margin  of  the  orbit.  In  accordance  with  these  relations,  it 
is  customary  to  regard  the  muscle  as  consisting  of  two  main  portions,  the  pars  palpe- 
bralis and  the  pars  orbitalis. 

The  internal  palpebral  ligament  (ligamentum  palpebrale  mediale).  Where  the 
fibres  of  the  orbicularis  arise  at  the  inner  angle  of  the  eye  there  is  a  dense  band  of 
fibrous  tissue  which  is  attached  at  one  extremity  to  the  frontal  process  of  the  maxilla. 
Thence  it  is  directed  outward  across  the  outer  surface  of  the  lachrymal  sac  and  bifur- 
cates to  be  inserted  into  the  inner  border  of  each  tarsal  plate.  Just  before  its  bifur- 
cation the  ligament  gives  off  from  its  posterior  surface  a  bundle  which  is  reflected 

inward  over  the  lachrymal  sac  and 
Fig.  500.  passes  behind  this  to  be  attached  to  the 

Internal  palpebral  ligament        Orbicularis  palpebrarum  crest  of    the  lachrvmal  bone 

Te,lsortarsi      \      ,  I      tg- tarsal  plate  This  ligament,  which  is  also  known 

A-  L^v.  I  'JsL^s-  as  the  tendo  oculi,  may  be  regarded  as 

-    ^flf^T  fjff  i[ ;      External  |      the  tendon  of  origin  of  the  fibres  of  the 

orbicularis  oculi.  At  the  outer  angle 
of  the  eye  there  is  a  certain  amount  of 
decussation  of  the  fibres  of  the  muscle 
to  form  a  raphe  palpebralis  lateralis, 
-tarsal  but  there  is  no  distinct  formation  of  a 

pia'e  fibrous  band  comparable  to  the  inter- 

NOrbicularis  _    i  i*  _. 

palpebrarum  nal  ligament. 

Orbicularis  palpebrarum  has  been  dissected  from  its  deeper  Pars   Palpebralis. The  palpe- 

portton  ornte,"seor  tarsi.inward  w"h  eye'ids'  showi"s  IachrymaI     bral  portion  of  the  muscle  arises  partly 

from  the  internal  palpebral  ligament 
and  partly  from  the  crest  of  the  lachrymal  bone.  The  fibres  which  take  origin  from 
the  ligament  arch  outward  in  the  upper  and  lower  eyelids  to  terminate  in  the  lateral 
palpebral  raphe,  forming  a  thin,  pale  sheet  in  the  subcutaneous  tissue  of  the  eyelid. 
Its  marginal  fibres,  sometimes  more  or  less  distinct  from  the  others,  form  what  has 
been  termed  thenar.?  ciliaris  or  muscle  of  Riolan. 

The  fibres  which  arise  from  the  posterior  lachrymal  crest  are  usually  regarded  as 
forming  either  a  distinct  muscle,  which  has  been  termed  the  tensor  tarsi  or  Homer' s 
muscle,  or  else  as  a  separate  part  of  the  orbicularis,  the  pars  lacrimalis.  It  is 
directed  horizontally  outward  behind  the  lachrymal  sac,  resting  upon  the  posterior 
surface  of  the  reflected  bundle  of  the  internal  palpebral  ligament.  Towards  its  outer 
end  it  bifurcates,  sending  a  slip  to  each  eyelid  partly  to  be  inserted  into  the  tarsal 
plates  and  partly  to  fuse  with  the  rest  of  the  pars  palpebralis. 

Pars  Orbitalis. — The  orbital  portion  of  the  muscle  is  usually  of  a  deeper  color 
and  somewhat  thicker  than  the  palpebral,  and  the  fibres  towards  its  periphery  tend 
to  scatter  themselves  among  the  adjacent  platysma  muscles  and  to  make  numerous 
connections  with  these.  Some  bundles  from  the  lateral  and  lower  parts  of  the  muscle 
which  extend  downward  and  forward  upon  the  cheek  have  been  regarded  as  a  dis- 
tinct muscle,  the  malaris. 

The  main  muscle  arises  from  the  internal  palpebral  ligament,  the  frontal  process 
of  the  maxilla,  and  the  inner  portions  of  the  upper  and  lower  margins  of  the  orbit. 
The  fibres  arch  outward  to  the  lateral  palpebral  raphe,  a  portion  of  those  arising  from 
the  maxilla  inserting  into  the  integument  of  the  eyebrow  and  forming  what  has  been 
termed  the  corrugator  supercilii  (Fig.  499). 

Nerve-Supply. — By  the  rami  temporales  and  zygomatici  of  the  facial  nerve. 


THE   FACIAL   MUSCLES.  485 

Action. — The  principal  action  of  the  orbicularis  palpebrarum  is  to  approximate 
the  upper  and  lower  eyelids,  closing  the  palpebral  fissure.  In  addition,  the  attach- 
ment of  the  orbital  portion  to  the  skin  draws  the  eyebrow  downward  and  the  skin  of 
the  cheek  upward  to  form  a  fold  around  the  margin  of  the  orbit,  giving  increased 
protection  to  the  eyeball.  The  corrugator  supercilii  draws  the  eyebrow  downward 
and  inward,  producing  vertical  wrinkles  of  the  integument  over  the  glabella  and  giving 
a  thoughtful  expression. 

The  pars  lacrimalis  draws  the  tarsal  plates  inward  and  backward  and  so  tenses 
the  internal  palpebral  ligament,  causing  it  to  compress  the  lachrymal  sac. 

7.   Zygomaticus  Major  (Figs.  499,  502). 

Attachments. — The  zygomaticus  major  (m.  zygomaticus)  is  a  slender  muscle 
which  arises  above  from  the  outer  surface  of  the  zygomatic  bone,  near  its  articulation 
with  the  zygomatic  process  of  the  temporal,  and  passes  obliquely  downward  and  for- 
ward towards,  the  angle  of  the  mouth.  Its  fibres  interlace  with  those  of  the  depressor 
and  levator  anguli  oris,  and  terminate  by  blending  with  the  orbicularis  oris  and  by 
inserting  into  the  subcutaneous  tissue  of  the  lips. 

Nerve-Supply. — By  fibres  from  the  zygomatic  branch  of  the  facial  nerve. 

Action. — To  draw  upward  and  outward  the  angles  of  the  mouth,  as  in  smiling 
and  laughing. 

Variations. — A  slender  muscle  is  very  frequently  found  arising  from  the  zygomatic  bone 
anterior  to  the  zygomaticus  and  passing  downward  to  be  inserted  into  the  upper  lip.  It  has 
been  termed  the  zygomaticus  minor,  and  appears  to  be  a  separation  of  a  portion  of  the  zygo- 
matic muscle. 

8.   Levator  Labii  Superioris  Al^eque  Nasi  (Figs.  499,  501). 

Attachments. — This  muscle  takes  its  origin  from  the  outer  surface  of  the 
frontal  process  of  the  maxilla,  and  descends  along  the  angle  which  marks  the  junction 
of  the  nose  and  the  cheek  to  be  inserted  into  the  integument  of  the  upper  lip  and 
into  the  posterior  part  of  the  ala  nasi. 

Nerve-Supply. — From  the  rami  zygomatici  of  the  facial  nerve. 

Action. — The  principal  action  of  this  muscle  is  to  raise  the  upper  lip,  although 
its  insertion  into  the  ala  nasi  enables  it  to  assist  in  the  dilatation  of  the  nostrils. 

Variations. — This  muscle  is  subject  to  considerable  variation  in  its  development,  and 
frequently  comes  into  continuity  with  neighboring  muscles,  especially  with  the  zygomaticus 
minor,  when  this  is  present,  and  with  the  levator  labii  superioris  proprius.  Indeed,  these  two 
muscles  are  often  associated  with  it  to  form  what  is  termed  the  quadratics  labii  superioris,  of 
which  the  levator  labii  superioris  alaeque  nasi  forms  the  caput  angulare,  the  levator  labii  superi- 
oris proprius  the  caput  infraorbitale,  and  the  zygomaticus  minor  the  caput  zygomaticus.  Since, 
however,  the  levator  labii  superioris  proprius  belongs  to  the  deep  layer  of  the  platysma  muscles, 
and  therefore  to  a  different  group  than  the  other  heads  of  the  quadratus,  it  seems  preferable  to 
regard  all  the  heads  as  distinct  muscles. 

9.   Depressor  Labii  Inferioris  (Figs.  498,  499). 

Attachments. — The  depressor  of  the  lower  lips  (m.  quadratus  labii  inferioris) 
arises  from  the  body  of  the  mandible  beneath  the  canine  and  premolar  teeth,  its 
origin  being  covered  by  the  depressor  anguli  oris.  It  forms  a  thin  quadrate  sheet 
which  is  directed  upward  and  forward  and  is  inserted  in  the  skin  of  the  lower  lip,  its 
fibres  mingling  also  with  those  of  the  orbicularis  oris. 

Nerve-Supply. — From  the  supramandibular  branch  of  the  facial  nerve. 

Action. — To  draw  down  the  lower  lip. 

10.   Levator  Menti  (Fig.  498). 

Attachments. — The  levator  menti  (m.  mentalis)  arises  from  the  body  of  the 
mandible  below  the  incisor  teeth,  and  its  fibres  descend,  diverging  as  they  go,  to  be 
inserted  into  the  integument  above  the  point  of  the  chin. 

Nerve-Supply. — From  the  supramandibular  branch  of  the  facial  nerve. 


486  HUMAN    ANATOMY. 

Action. — To  draw  upward  the  skin  of  the  chin,  thereby  causing  protrusion  of 
the  lower  lip,  as  in  pouting.  When  its  action  is  combined  with  contraction  of  the 
depressors  of  the  angles  of  the  mouth,  it  gives  an  expression  of  haughtiness  or  con- 
tempt, and  has  thence  been  termed  the  m.  superbus.  When  slightly  contracted,  it 
gives  an  expression  of  firmness  or  decision. 

Belonging  to  the  superficial  layer  of  the  platysma  musculature  are  a  number  of 
additional  more  or  less  rudimentary  muscles  attached  at  both  extremities  to  various 
parts  of  the  cartilage  of  the  concha.  These  muscles  will  be  considered  in  connection 
with  the  description  of  the  ear  (page  1499). 


(b)   THE   MUSCLES   OF  THE   DEEP   LAYER. 
1.   Orbicularis  Oris  (Figs.  499,  501,  503). 

Attachments. — The  orbicularis  oris  is  a  rather  strong  elliptical  muscle  whose 
fibres  occupy  the  thickness  of  both  the  upper  and  lower  lips  between  the  skin  and 
the  mucous  membrane  of  the  mouth.  For  the  most  part  the  fibres  composing  the 
muscle  are  forward  prolongations  of  the  buccinator,  but  mingled  with  these  there  are 
fibres  from  all  the  muscles  which  are  inserted  in  the  vicinity  of  the  mouth,  such  as 
the  zygomaticus,  levator  anguli  oris,  levator  labii  superioris,  depressor  anguli  oris, 
depressor  labii  inferioris,  and  risorius. 

It  possesses,  however,  some  slight  attachment  to  skeletal  structures  by  three 
groups  of  fibres  which  have  frequently  been  regarded  as  distinct  muscles.  These 
groups  are  :  ( 1 )  the  incisivi  labii  superioris,  a  series  of  bundles  of  fibres  which  arise 
from  the  incisive  fossa;  of  the  maxilla;  and  pass  downward  and  outward  to  mingle 
with  the  other  fibres  of  the  orbicularis  at  the  angles  of  the  mouth  ;  (2)  the  incisivi 
labii  inferioris,  which  arise  from  the  alveolar  border  of  the  mandible  beneath  the 
canine  teeth  and  unite  with  the  orbicularis  at  the  angles  of  the  mouth  ;  and  (3)  the 
depressor  septi,  composed  of  the  uppermost  fibres  of  the  orbicularis,  which  bend  up- 
ward from  either  side  in  the  median  iine  and  are  inserted  into  the  margin  of  the  septal 
cartilage  of  the  nose. 

Nerve-Supply. — From  the  rami  buccales  and  supramandibular  branch  of  the 
facial  nerve. 

Action'. — The  main  action  of  the  orbicularis  oris  is  to  bring  the  lips  together, 
closing  the  mouth,  and  if  its  action  be  continued,  it  will  press  the  lips  against  the  teeth. 

Its  more  peripheral  fibres,  aided  by 
Fig.  501.  the  incisive  bundles,  will  tend  to  pro- 

Pyramidalis  nasi  trude  the  lips. 

2.    Nasalis  (Fig.  501). 

Attachments.  —  The  nasalis 
forms  a  thin  sheet  which  arises  from 
the  maxilla  in  close  association  with 
the  incisive  bundles  of  the  upper  lip. 
The  more  medial  fibres,  the  pars  alaris 
{depressor  alts  nasi),  are  inserted  into 
the  alar  cartilage  of  the  nose,  while 
the  more  lateral  ones,  the  pars  trans- 
versa {compressor  narium),  often  re- 
ceiving slips  from  the  adjacent  levator 
labii  superioris  alseque  nasi  and  the 
levator  anguli  oris,  extend  forward 
over  the  ala  of  the  nose  to  terminate 
upon  its  dorsal  surface  in  a  thin  aponeurosis  which  unites  it  to  the  muscle  of  the 
opposite  side. 

Nerve-Supply. — From  the  zygomatic  and  buccal  rami  of  the  facial_nerye. 
Action. — The  more  median  fibres  draw  the  alar  cartilage  downward  and  in- 
ward, while  the  more  lateral  ones  slightly  depress  the  tip  of  the  nose  and  at  the  same 
time  compress  the  nostril. 


Depressor  septi 


Muscles  of  the  nose. 


THE.  FACIAL   MUSCLES.  487 

Variations. — Fibres  from  the  nasalis  sometimes  pass  upward  upon  the  nasal  bones  and 
may  enter  into  the  formation  of  the pyramidalis nasi  (page  482).  Frequently  the  pars  alaris  and 
pars  transversa  are  recognized  as  distinct  muscles,  the  former  being  termed  the  depressor  ales 
nasi  or  myrtiformis,  while  the  latter  is  named  the  compressor  narium.  Uncertain  and  at  best 
feeble  muscular  slips  on  the  outer  margin  of  the  nostrils  are  sometimes  described  as  distinct 
muscles,  the  dilatores  naris  anterior  et posterior. 

3.   Levator  Labii  Superioris  (Fig.  499). 

Attachments. — The  elevator  of  the  upper  lip  (m.  levator  labii  superioris  pro- 
prius)  arises  above  from  the  infraorbital  margin  of  the  maxilla  and  extends  almost 
vertically  downward  over  the  infraorbital  vessels  and  nerve  to  join  with  the  orbicu- 
laris oris  and  also  to  be  inserted  into  the  skin  of  the  upper  lip  between  the  insertions 
of  the  levator  labii  superioris  alaeque  nasi  and  the  levator  anguli  oris. 

Nerve-Supply. — From  the  zygomatic  branches  of  the  facial  nerve. 

Action. — To  raise  the  upper  lip.  Acting  in  conjunction  withTTHe  levator  labii 
superioris  alaeque  nasi,  it  plays  an  important  part  in  the  expression  of  grief. 

4.   Levator  Anguli  Oris  (Figs.  499,  502). 

Attachments. — The  elevator  of  the  angle  of  the  mouth  (m.  caninus)  arises  from 
the  canine  fossa  of  the  maxilla  by  a  rather  broad  origin,  from  which  its  fibres  con- 
verge to  be  inserted  into  the  skin  at  the  angle  of  the  mouth,  partly  mingling  with  the 
fibres  of  the  depressor  anguli  oris. 

Nerve-Supply. — From  the  zygomatic  branches  of  the  facial  nerve. 

Action. — To  raise  the  angle  of  the  mouth. 

5.    Risorius  (Fig.  499). 

Attachments. — The  risorius  is  a  triangular  sheet  of  muscle  which  arises  from 
the  outer  surface  of  the  parotido-masseteric  fascia  and  from  the  integument  of  the 
cheek  and  passes  forward  towards  the  angle  of  the  mouth,  where  it  unites  with  the 
depressor  anguli  and  orbicularis  oris. 

Nerve-Supply. — From  the  rami  buccales  of  the  facial  nerve. 

Action. — To  draw  the  angle  of  the  mouth  outward.  Its  contraction  imparts 
a  tense  and  strained  expression  to  the  face  which  is  termed  the  risus  sardonicus. 

Variation. — The  risorius  is  frequently  absent,  and  may  be  represented  only  by  some 
scattered  muscular  bands.  Its  intimate  association  with  the  depressor  anguli  oris  indicates  its 
derivation  from  that  muscle. 

6.   Depressor  Anguli  Oris  (Figs.  498,  499). 

Attachments. — The  depressor  of  the  angle  of  the  mouth  (m.  triangularis) 
takes  its  origin  from  the  outer  surface  of  the  body  of  the  mandible  and  from  the' skin 
and  passes  upward  to  the  angle  of  the  mouth,  where  its  fibres  are  inserted  into  the 
skin  and  also  mingle  with  those  of  the  caninus,  risorius,  and  orbicularis  oris. 

Nerve-Supply. — From  the  supramarginal  branch  of  the  facial  nerve. 

Action. — To  draw  the  angle  of  the  mouth  downward  and  slightly  outward, 
giving  an  expression  of  sorrow. 

Variations. — A  bundle  of  fibres  not  infrequently  arises  from  the  anterior  border  of  the 
depressor  anguli  oris  near  its  origin  and  passes  obliquely  downward  and  inward  towards  the 
median  line  beneath  the  chin,  either  losing  itself  in  the  superficial  fascia  of  that  region  or  uniting 
with  its  fellow  of  the  opposite  side.  This  slip  has  been  regarded  as  a  distinct  muscle  and 
termed  the  transversus  menti.  It  seems  exceedingly  probable  that  both  this  bundle  and  the 
risorius  are  derivatives  of  the  depressor,  and  this  muscle,  notwithstanding  its  position  super- 
ficial to  both  the  depressor  labii  inferioris  and  the  platysma,  is  really  a  portion  of  the  deeper 
layer  of  the  platysma  musculature,  its  present  position  having  been  acquired  by  a  migration  from 
the  region  of  the  upper  lip. 


HUMAN    ANATOMY. 


7.   Buccinator    (Fig.  502). 

Bucco-Pharyngeal  Fascia. — The  buccinator  alone  of  the  platysma  group  of 
muscles  is  covered  by  a  distinct  layer  of  fascia  which  forms  the  anterior  part  of  the 
fascia  buccopharyngea  and  is  a  dense,  resistant  sheet  of  connective  tissue  intimately 

Fig.  502. 


Corrugator  supercilii 

Orbic.  palp.,  palpebral  part 
Pyramidalis  nasi 

Orbic.  palp.,  orbital  part 
Lev.  labii  sup.  al.  nasi  (cut) 
Levator  labii  superioris  (cut) 

Compressor  narium 
Levator  anguli  oris 
Zygomaticus 


* —  Depressor  labii  inferioris 


Temporal 


Tensor  palati 

Levator  palati 

Styloid  process 

Hamular  process 

Digastric,  posterior  bell 

Superior  constrictor 
Stylo-gl, 
Pterygo-mandibular  ligament 

Stylo-phyaryngeus 
Stylo-hyoid 

Mandible  (cut) 
Hyo-glossus 
Greater 
Middle  constrictor 


Thyro-hyoid 
Inferior  constrictor 


Oral,  pharyngeal,  and  styloid  groups  of  muscles ;  part  of  mandible  has  been  removed  to  show  deeper  structures. 

adherent  to  the  outer  surface  of  the  muscle.  Anteriorly  the  fascia  thins  out  to  disap- 
pear in  the  tissue  of  the  lips  ;  above  it  is  attached  to  the  alveolar  portion  of  the 
maxilla  and  to  the  internal  pterygoid  plate  of  the  sphenoid,  and  thence  is  continued 

backward  over  the  superior  con- 
riG.  503.  strictor  muscle  of  the  pharynx 

to  meet  with  its  fellow  of  the 
opposite  side  behind  the  phar- 
ynx ;  below  it  is  attached  to  the 
posterior  part  of  the  mylo-hyoid 
ridge  of  the  mandible.  Along 
a  line  which  descends  vertically 
from  the  tip  of  the  hamulus  of 
the  sphenoid  to  the  posterior 
extremity  of  the  mylo-hyoid 
ridge  of  the  mandible  the  fascia 
is  greatly  thickened,  forming 
the  pterygo-mandibular  liga- 
me?it,  from  which  fibres  of  the 
buccinator  arise  anteriorly,  while 
posteriorly  it  gives  origin  to  a 
portion  of  the  superior  constric- 
tor of  the  pharynx. 

Attachments. — The  buc- 
cinator forms  a  thick  quadrilateral  muscle  lying  immediately  exterior  to  the  mucous 
membrane  of  the  cheek.  Its  line  of  origin  is  horseshoe-shaped,  extending  above 
along  the  alveolar  border  and  tuberosity  of  the  maxilla  and  thence  upon  the  hamulus 


Levator  anguli  oris 


Depressor  anguli 


PRACTICAL   CONSIDERATIONS:    THE   SCALP. 


489 


of  the  internal  pterygoid  plate  of  the  sphenoid.  It  then  descends  upon  the  anterior 
border  of  the  pterygo-mandibular  raphe,  whence  it  passes  forward  along  the  body 
of  the  mandible,  above  the  mylo-hyoid  ridge,  as  far  as  the  premolar  teeth.  From 
this  extensive  origin  its  fibres  are  directed  forward  to  become  continuous  with  those 
of  the  orbicularis  oris,  also  inserting  to  a  certain  extent  into  the  integument  of  the  lips. 

Nerve-Supply. — From  the  buccal  branch  of  the  facial  nerve. 

Action. — The  buccinator  draws  the  angle  of  the  mouth  laterally,  pressing  the 
lips  against  the  teeth.  When  the  cheeks  are  distended  the  muscle  serves  to  com- 
press the  contents  of  the  mouth,  and  plays  an  important  part  in  mastication  in  pre- 
venting the  accumulation  of  the  food  between  the  cheek  and  the  jaws,  forcing  it 
back  between  the  teeth. 

Relations. — Superficially  with  the  bucco-pharyngeal  fascia,  which  is  separated 
from  the  anterior  part  of  the  masseter  and  from  the  zygomaticus  and  risorius  by  an 
extensive  pad  of  fat, — the  buccal  fat-pad.  This  is  prolonged  backward  into  the  zygo- 
matic fossa  between  the  temporal  and  pterygoid  muscles,  and  is  traversed  by  the  facial 
vessels  and  the  buccal  branches  of  the  trigeminal  and  facial  nerves. 

The  buccinator  is  pierced  from  without  inward  by  the  parotid  duct  and  by  the 
buccal  branch  of  the  trigeminal  nerve  on  its  way  towards  its  distribution  to  the 
mucous  membrane  of  the  cheek. 

PRACTICAL  CONSIDERATIONS  :     MUSCLES   AND    FASCI/E   OF    THE 

CRANIUM. 

The  Scalp. —  The  Occipito- Frontal  Regio7i. — The  layers  of  the  scalp  from 
within  outward  are  : 

1.  The  pericranium — as  the  periosteum  covering  this  part  of  the  skull  is 
termed — closely  invests  the  underlying  bones  and  is  firmly  attached  at  the  sutures 
through  which,  so  long  as  these  remain  ununited,  it  is  continuous  (intersutural  mem- 
brane) with  the  outer  layer  of  the  dura, — the  endosteum  of  the  cranium.      A  similar 


Superficial  fascia 


Apon 
Subaponeurotic 


and  more  constant  continuity  exists  through  the  foramina.  As  the  dura  is  the  chief 
source  of  blood-supply  of  the  cranial  bones,  they  rarely  necrose  after  accidents  which 
strip  the  pericranium  from  their  surface  (page  237).  Subpericranial  effusions  of 
blood,  or  collections  of  pus,  are  limited  and  outlined  by  the  lines  of  the  sutures. 
"  Cephalhaematomata"  in  this  situation  correspond  in  shape  to  that  of  one  bone  :  they 
are  commonly  congenital,  constituting  a  form  of  caput  succedaneum,  following  head 
presentations,  and  are  then  apt  to  be  found  over  a  parietal  bone,  since  that  region  is 
most  exposed  to  pressure  during  child-birth.  Tillaux  suggests  that  in  early  life  they 
may  be  encouraged  by  the  softness  and  vascularity  of  the  cranial  bones  and  the 


49Q  HUMAN    ANATOMY. 

laxity  of  the  pericranium,  and  that  their  greater  frequency  in  male  children  may 
depend  upon  the  larger  size  of  the  head  in  the  male  foetus.  The  close  association  of 
the  bloody  effusion  with  the  pericranium — an  osteogenetic  membrane — sometimes 
results  in  the  development  of  bone  at  the  periphery  of  the  swelling.  The  hard 
ridge  which  is  usually  present  at  this  situation  may  give  rise,  through  contrast  with 
the  relatively  depressed  centre,  to  the  mistaken  diagnosis  of  fracture  of  the  skull. 

Occasionally  a  collection  of  blood  beneath  the  pericranium  communicates  with 
the  diploic  sinuses,  when  it  will  probably  be  situated  to  one  side  of  the  cranium  ;  or 
with  the  superior  longitudinal  sinus,  when  it  will  be  in  the  mid-line.  No  traumatic 
history  may  be  obtainable.  The  swelling  will  be  soft,  reducible,  of  varying  tension, 
and  may  receive  from  the  brain  a  feeble  pulsatile  impulse. 

The  importance  of  the  emissary  veins  in  transmitting  extracranial  infection  to 
the  venous  channels  of  the  dura  may  be  mentioned  here,  but  can  better  be  under- 
stood after  the  venous  system  has  been  described  (page  876). 

2.  The  subaponeurotic  connective  tissue  between  the  pericranium  and  the  apo- 
neurosis of  the  occipito-frontalis.  This  is  so  loose,  thin,  and  elastic  that  the  union 
between  these  layers  is  not  a  close  one.  The  motion  of  the  "scalp"  upon  the  skull 
is  a  motion  of  the  parts  above  upon  the  parts  beneath  this  layer.  Movable  growths 
will,  therefore,  be  found  to  occupy  the  former  region  and  immovable  swellings  will 
probably  have  deeper  attachments.  Effusions  of  blood,  suppuration,  or  infective 
cellulitis  occurring  in  the  subaponeurotic  space  may  extend  widely,  and  may  be 
limited  only  by  the  attachments  of  the  musculo-fibrous  layer.  They  may  reach,  there- 
fore, posteriorly  to  the  superior  curved  line  of  the  occipital  bone,  anteriorly  to  a  little 
above  the  eyebrows,  and  laterally  to  a  level  somewhat  above  the  zygoma.  Exten- 
sive haematomata  are  uncommon,  as  the  vessels  in  this  cellular  tissue  are  few  and 
small.  If  they  are  large,  they  suggest  fracture  of  the  skull  with  laceration  of  a  branch 
of  the  middle  meningeal  artery  or  of  a  venous  sinus.  They  may,  however,  by  reason 
of  a  hard  border  and  soft  centre,  be  mistaken  for  depressed  fracture  when  the  skull 
itself  is  uninjured. 

Suppuration  and  cellulitis  are  often  serious  on  account  of  the  tendency  to  spread, 
the  possible  extension  to  the  meninges,  and  the  difficulty  in  applying  antisepsis,  in 
securing  drainage,  or,  later,  in  obtaining  the  rest  necessary  for  rapid  healing.  In 
abscess  the  diffusion  of  the  pus  is  favored  by  the  density  and  the  vitality  of  the  super- 
jacent layers,  which,  in  consequence  of  the  former  property,  do  not  soften  and  permit 
pointing,  and,  because  of  the  latter,  do  not  slough  and  thus  give  exit  to  the  pus,  which 
therefore  may  extend  in  the  line  of  least  resistance, — i.e.,  along  the  loose  subapo- 
neurotic layer.  Wounds  involving  either  the  muscle  or  its  aponeurosis,  if  transverse 
to  the  direction  of  their  fibres,  gape  widely.  Their  healing  will  be  hastened  by 
firm  bandaging  of  the  whole  cranium  so  as  to  control  and  limit  the  movements  of 
the  scalp. 

3.  The  occipito-frontalis  muscle  and  aponeurosis;  4,  the  superficial fascia ; ^  5, 
the  skin.  These  three  layers  are  so  intimately  blended  that  from  the  practical 
stand-point  they  may  be  considered  together.  The  thin  aponeurosis  is  tied  to  the 
skin  (which  is  here  thicker  than  anywhere  else  in  the  body)  by  dense,  inelastic, 
perpendicular  and  oblique  fibres  of  connective  tissue,  enclosing  little  shot-like  masses 
of  fat.  This  area  is  very  vascular,  almost  all  the  vessels  of  the  scalp  being  found  in 
it  adherent  to  the  cellular-tissue  walls  of  the  fat-containing  compartments.  As  a 
result  of  these  anatomical  conditions  it  is  found  that  ( 1 )  suppuration  is  very  limited 
in  extent  ;  (2)  superficial  infections  (such  as  erysipelatous  dermatitis)  are  accom- 
panied by  but  little  swelling  ;  (3)  incised  wounds  do  not  gape  ;  (4)  lacerated  and 
contused  wounds  are  not  followed  by  sloughing,  which  is  also  rare  as  a  result  of 
continuous  pressure,  as  from  bandages  ;  (5)  hemorrhage  after  wounds  is  abundant 
and  is  persistent  because  of  the  adherence  of  the  vessel-walls  to  the  subcutaneous 
layer  of  fascia,  which  prevents  both  their  retraction  and  contraction  ;  (6)  collections 
of  blood  after  contusions  may,  like  the  deeper  ones  already  described,  become  very 
firm  at  the  periphery, — in  this  case  from  an  excess  of  fibrinous  exudate  and  from 
the  presence  of  particles  of  displaced  fat, — while  the  inelastic  fibres  of  cellular  tissue 
(from  among  which  the  fat  particles  have  been  driven  out  by  the  force  of  the  blow) 
remain  depressed  in  the  centre  ;  these  appearances  have  not  infrequently  led  to  a 


PRACTICAL   CONSIDERATIONS  :    THE   SCALP.  491 

mistaken  diagnosis  of  fracture  of  the  skull  ;  (7)  lipomata  are  rare,  as  in  the  only- 
layer  in  which  fat  is  found  its  abnormal  growth  is  resisted  by  the  density  of  the 
surrounding  connective  tissue. 

Baldness  affects  especially  the  area  of  the  scalp  which  directly  overlies  the 
occipito-frontal  aponeurosis.  It  is  attributed  (Elliott)  largely  to  the  lack  of  muscular 
fibres  in  this  region,  so  that  the  skin  is  not  "  exercised"  and  the  lymph-current  is 
made  to  depend  chiefly  on  gravity.  The  density  of  the  superficial  fascia  connecting 
the  skin  and  the  aponeurosis  allies  it  with  that  of  the  palmar  and  plantar  regions,  in 
both  of  which  similarly  dense  fascia  is  found  and  hair  is  absent. 

Dermoids  are  common  over  the  anterior  fontanelle  and  the  occipital  protuber- 
ance because  the  early  contact  of  the  skin  and  dura  mater  continues  longest  in  these 
regions.  "Should  the  skin  be  imperfectly  separated,  or  a  portion  remain  persist- 
ently adherent  to  the  dura  mater,  it  would  act  precisely  as  a  tumor  germ  and  give 
rise  to  a  dermoid  cyst"  (Sutton). 

Wens  are  also  common  on  account  of  the  presence  of  large  numbers  of  seba- 
ceous glands.  In  removing  such  growths,  if  the  dissection  is  carried  close  to  the 
sac,  the  subaponeurotic  layer  will  not  be  opened  and  all  danger,  even  in  case  of 
infection,  will  be  minimized. 

So-called  "horns"  are  found  here  with  relative  frequency  by  reason  of  the 
number  of  sebaceous  glands. 

Emphysema  of  the  scalp  may  occur  as  a  complication  of  fractures  involving  the 
pharynx,  the  frontal  sinuses,  or  the  ethmoid  or  nasal  bones.  The  air  infiltrates 
either  the  subaponeurotic  or  subcutaneous  cellular  tissue. 

Pneumatocele  of  the  frontal  region  is  very  rare,  but  has  occurred  in  a  few  cases 
as  a  result  of  a  communication  between  the  nasal  cavity  and  bony  defects  in  the 
anterior  wall  of  the  frontal  sinuses.  The  swelling  is  soft,  elastic,  and  resonant,  and  is 
made  more  tense  by  forced  expiration,  less  so  by  pressure.  The  entrance  and  escape 
of  air  may  be  heard  on  auscultation.      The  air  is  always  beneath  the  pericranium. 

Syphilis,  tuberculosis,  carcinoma,  and  sarcoma  may  affect  the  scalp  primarily, 
and  are  mentioned  in  the  order  of  frequency  of  occurrence. 

Cirsoid  aneurism  is  especially  frequent  upon  the  scalp. 

The  Tempoi'al  Region. — Here  the  skin  is  thinner  and  less  intimately  adherent 
to  the  subcutaneous  fascia  than  in  the  occipito-frontal  region  ;  that  fascia  also  is 
somewhat  less  closely  connected  to  the  aponeurosis  beneath.  Hemorrhage  between 
these  layers  is  therefore  more  easily  controlled  by  the  usual  process  of  picking  up 
and  tying  the  vessel,  the  walls  of  which  will  be  found  freer  from  attachments  to  the 
bundles  of  fascia. 

The  fascia  over  the  temporal  muscle  itself  is  of  such  strength  and  thickness  that 
abscesses  beneath  it  rarely  point  above  the  zygoma,  but  are  directed  into  the  pterygo- 
maxillary  region  and  thence  into  the  pharynx  or  into  the  neck,  or  along  the  anterior 
temporal  muscular  fibres  to  the  coronoid  process  and  thence  into  the  mouth. 
Abscesses  above  it  have  no  special  anatomical  peculiarities. 

The  fat  in  the  temporal  fossa  is  abundant,  and  is  found  in  the  subcutaneous 
fascia,  between  the  two  layers  of  the  temporal  fascia,  and  directly  upon  the  muscle 
itself.  The  disappearance  of  this  fat  in  diseases  attended  by  emaciation  causes  the 
characteristic  unnatural  prominence  of  the  zygoma  and  apparent  deepening  of  the 
temporal  fossae. 

The  temporal  muscle  should  be  considered  with  the  pterygoids  in  their  relation 
to  fracture  of  the  ramus  and  coronoid  process  (pages  245,  493),  to  dislocation  of 
the  inferior  maxilla  (pages  246,  493),  and  to  resection  of  that  bone. 

The  pericranium  of  this  region  is  thinner  and  more  adherent  than  that  of  the 
occipito-frontal  region,  and  the  subpericranial  connective  tissue  is  absent ;  hence 
subperiosteal  abscess  or  hsematoma  is  practically  unknown. 

The  region  may  be  invaded  by  tumors  originating  in  the  orbit  and  spreading 
through  the  spheno-maxillary  fissure  or  through  the  thin  orbital  process  of  the 
malar  bone. 

Trephining  and  other  operations  in  this  region  are  so  closely  related  to  intra- 
cranial diseases  and  middle-ear  disease  that  they  will  be  considered  in  that  relation 
(page  1509). 


492 


HUMAN   ANATOMY. 


The  Mastoid  Regio?i.—¥ox  the  same  reasons  the  practical  anatomy  of  the  soft 
parts  covering  the  remaining  region  of  the  skull — the  mastoid — will  be  taken  up 
later  (page  1508). 

The  Face. — The  skin  of  the  forehead  and  cheeks  is  thin  and  vascular  and  the 
cellular  tissue  beneath  is  loose.  Therefore  wounds  bleed  freely  but  unite  rapidly  ; 
sloughing  is  rare  ;  cellulitis  tends  to  spread  ;  cedema  is  common  ;  superficial  infections 
(favored  by  the  constant  exposure  of  the  region)  are  attended  by  much  redness  and 
swelling  and  little  pain  ;  if  they  result  in  abscess,  it  is  not  apt  to  attain  a  large  size, 
as  the  delicacy  of  the  skin  permits  of  early  pointing.  On  the  other  hand,  necrotic 
processes  (as  in  cancrum  oris)  once  established  in  the  loose  cellular  tissue  and  fat  of 
the  cheeks,  run  a  rapid  and  destructive  course,  and  may  be  followed  by  great  dis- 
figurement and  by  limitation  of  the  motions  of  the  inferior  maxilla. 

Abscesses  beneath  the  buccinator  aponeurosis,  like  fatty  growths  in  the  same 
situation,  project  towards  the  cavity  of  the  mouth  ;  they  should  be  opened  through 
the  mucous  membrane. 

Fig.  505. 


Upper  cut  edge  of  masseter 

Temporal 

External  pterygoid 


Internal  pterygoid 
Masseter  (cut 


Parotid  gland 
partly  removed 


Posterior  fragment 


■Line  of  fracture 
— Anterior  fragment 
Digastric,  anterior  belly 

— -Mylohyoid 

Hyo-glossus 

Body  of  hyoid  bone 


Sterno-mastoid 


Dissection  of  fracture  of  body  of  mandible,  showing  displacement  produced  by  muscular  action. 

Over  the  lower  third  of  the  nose  the  skin  is  closely  adherent,  as  it  is  over  the 
chin,  where  it  is  also  very  dense.  Infections  in  those  regions  are  therefore  exception- 
ally painful  (page  246).  The  vascularity  and  mobility  of  the  skin  of  the  forehead 
and  of  the  cheeks  make  it  especially  useful  in  plastic  operations  upon  the  region  of 
the  nose  and  mouth. 

On  account  of  the  rich  blood-supply,  naevi  are  common  on  all  parts  of  the  face, 
as,  by  reason  of  the  numerous  sweat  and  sebaceous  glands,  are  acneiform  eruptions. 

Lupus  and  malignant  pustule  are  frequent  and  grave  forms  of  local  infection  ; 
rodent  ulcer  (epithelioma)  is  common  ;  while  on  the  forehead  the  early  syphilitic 
roseola  or  papule  (corona  veneris)  and  about  the  lips  and  nose  the  later  tubercular 
syphilide  are  often  seen. 

Lipomata,  in  spite  of  the  considerable  quantity  of  fat  in  the  subcutaneous  tissue, 
are  very  rare.      The  mass  of  fat  between  the  buccinator  and   masseter    muscles — 


PRACTICAL   CONSIDERATIONS  :    THE   FACE. 


493 


Fig.  506. 


Upper  joint-cavity 


"  boule  de  Bichat,"  "sucking  cushion" — is  believed  to  receive  and  distribute  the 
increased  atmospheric  pressure  which  follows  the  establishment  of  a  partial  vacuum 
in  the  mouth  during  sucking.  It  thus  aids  in  preventing  the  buccinator  from  being 
carried  in  between  the  alveoli.  It  is  relatively  smaller  in  adults  than  in  infants  and 
in  the  latter  does  not  much 
diminish  in  size,  even  in  the 
presence  of  emaciation,  when 
the  general  subcutaneous  fat 
has  largely  disappeared 
(Ranke).  Sutton  says,  " The 
sucking  cushions  sometimes 
enlarge  in  adults  and  simulate 
more  serious  species  of  tu- 
mors, and  it  is  curious  that  in 
some  of  the  recorded  cases 
the  enlargement  has  been  as- 
sociated with  the  impaction  of 
a  salivary  calculus  in  the  duct 
of  the  parotid  gland. ' ' 

The  importance  of  avoid- 
ing conspicuous  scars  on  the 
face  leads  the  surgeon  to  make 
his  incisions,  whenever  possi- 
ble, either  in  or  parallel  with 
the  lines  of  the  natural  furrows  due  to  the  insertion  of  some  of  the  facial  muscles  into 
the  skin  itself,  or  in  the  shadow  of  overhanging  parts,  as  beneath  the  upper  brow 
or  the  lower  edge  of  the  inferior  maxilla.  For  a  reason  not  understood,  but  possibly 
associated  with  the  difficulty  in  securing  rest,  combined  with  the  large  vascular  sup- 
ply, cicatricial  overgrowth  and  true  keloid  are  both  relatively  common  after  wounds 
of  the  face. 

In  fracture  of  the  inferior  maxilla  the  irregularity  in  the  horizontal  planes  of  the 
two  fragments  (the  anterior  being  the  lower)  is  due  to  (a)  the  weight  of  the  chin  and 

opposite  side  of    the  jaw 


Dissection  showing  relations  when  mandible  rests  within  glenoid 
fossa  ;  outer  part  of  capsular  ligament  has  been  cut  away,  exposing  upper 
and  lower  joint-cavities. 


Fig.  507. 


Tendor 
tempo 


(6)  the  action  on  the  an- 
terior fragment  of  the  di- 
gastric and  other  depressors 
of  the  chin  ;  and  (<r)  the 
effect  of  the  posterior  fibres 
of  the  temporal,  the  internal 
pterygoid,  and  the  super- 
ficial fibres  of  the  masseter 
in  elevating  the  posterior 
fragment  (Fig.  505). 

In  fracture  of  the  ramus 
there  is  little  displacement, 
as  the  bone  lies  between  the 
two  muscular  planes  of  the 
masseter  and  internal  ptery- 
goid and  is  splinted  by 
them.  In  fracture  of  the 
neck  of  the  condyle  the 
upper  fragment  is  drawn 
upward  and  forward  by  the 
external  pterygoid  ;  the  re- 
mainder of  the  jaw  is  some- 
what elevated  by  the  masseter,  temporal,  and  internal  pterygoid.  The  difficulty  in 
approximation  of  the  fragments  may  result  in  excess  of  callus,  which  greatly  interferes 
with  the  subsequent  movements  of  the  temporo-maxillary  articulation. 

The  mechanism  of  dislocation  of  the  lower  jaw  has  already  been  described  (page 


Dissection  showing  relat 
forward  upon  articular  emii 
sequence. 


hen  mandible  is  depr. 
capsular  ligament   is 


494 


HUMAN   ANATOMY. 


246),  but  can  now  be  better  understood.  It  should  be  remembered  that  the  muscles 
of  mastication  are  exceptionally  irritable  and  are  all  supplied  by  the  motor  branch  of 
the  mandibular  division  of  the  fifth  nerve.  When  the  mouth  is  opened  very  widely, 
as  in  yawning,  or  in  an  effort  to  take  an  unusually  large  bite,  the  deep  posterior  ver- 
tical fibres  of  the  masseter  (which  are  the  only  ones  attached  to  the  ramus  and  aiding 
in  closing  the  mouth  that  do  not  run  forward  as  well  as  upward)  are  carried  behind 
the  centre  of  motion,  so  that  their  contraction  tends  still  further  to  open  the  mouth 
or  to  keep  it  open.  Reflex  contraction  from  overstretching  is  excited  in  the  general 
group,  and  the  external  pterygoid  acting  with  most  advantage  in  that  position, 
draws  the  condyle  into  the  zygomatic  fossa,  where  it  is  held  by  the  masseter  and 
internal  pterygoid. 

' '  Noisy  movement' '  of  the  temporo-maxillary  joint  is  often  due  to  weakness  of 
the  muscles  of  mastication,  permitting  the  joint  surfaces  to  fall  apart  as  the  result  of 
the  slight  lengthening  of  the  ligaments  produced  in  time  by  the  weight  of  the  jaw. 

Paralysis  and  spasm  of  the  facial  and  masticatory  muscles  will  be  considered  in 
relation  to  the  nerves  supplying  them  (pages  1255,  1248). 

The  most  frequent  congenital  defect  of  the  muscles  of  the  face  is  in  connection 

with  harelip,  in  which  deformity 


Fig.  50S. 


poral  muscle 


Masseter 
muscle,  partly 
cut  away 


Dissection  showing  position  of  dislocated  jaw,  condyle  having 
slipped  in  front  of  articular  eminence. 


the  portion  of  the  orbicularis 
oris  corresponding  to  the  cleft 
is  absent. 

Dermoids  are  not  infre- 
quently found  at  the  angles  of 
the  orbit,  in  the  cheeks  near 
the  corner  of  the  mouth,  in  the 
naso-labial  furrows,  at  the  root 
of  the  nose,  and  in  the  mid-line 
of  the  chin.  Reference  to  the 
embryology  of  the  face  will  show 
that  these  are  localities  in  which 
epiblastic  inclusion  is  likely  to 
occur. 

Marked  congenital  asym- 
metry of  the  face  may  occur 
from  failure  of  developmental 
processes. 

Landmarks. — Just  within 
the  mid-point  of  a  line  drawn 
from  the  mastoid  process  to  the 
external  occipital  protuberance 


the  occipital  artery  can  be  felt  as,  with  the  great  occipital  nerve,  it  enters  the  scalp 
on  its  way  to  the  vertex. 

The  superficial  temporal  artery  can  be  felt,  and  often  can  be  seen  where  it  runs 
over  the  base  of  the  zygoma  in  front  of  the  ear.  Its  vein  and  the  auriculo-temporal 
nerve  are  just  behind  it.  The  division  of  the  artery  into  its  anterior  and  posterior 
branches  takes  place  about  5  cm.  (2  in.)  above  the  zygoma.  These  branches  are 
easily  palpable  on  the  firm  underlying  structures,  and  thus  afford  testimony  as  to  the 
presence  or  absence  of  arterial  degeneration.  In  old  persons  they  are  often  tortuous 
and  plainly  visible,  especially  the  anterior  branch  where  it  crosses  the  anterior  por- 
tion of  the  temporal  muscle.      The  region  is  a  frequent  seat  of  cirsoid  aneurism. 

At  the  junction  of  the  middle  with  the  inner  third  of  the  supra-orbital  bony 
margin  the  supra-orbital  notch  may  be  felt.  From  this  point  the  supra-orbital  nerve 
and  artery  pass  almost  directly  upward,  crossing  the  orbital  margin.  Between  that 
point  and  the  root  of  the  nose  the  frontal  artery  and  supratrochlear  nerve  ascend 
and  the  frontal  vein  descends. 

The  movement  of  the  condyle  of  the  inferior  maxilla  up  to  the  summit  of  the 
eminentia  articularis  when  the  mouth  is  open  and  the  external  pterygoid  contracts, 
and  its  return  into  the  glenoid  cavity  when  that  muscle  is  relaxed  and  the  mouth  is 
closed,  can  plainly  be  felt. 


THE   VAGO-ACCESSORY    MUSCLES.  495 

The  relation  of  many  of  the  bony  points  to  the  overlying  soft  parts  has  been 
described  (page  246). 

The  shape  of  most  of  the  muscles  cannot  be  separately  distinguished.  Com- 
parison of  a  skull  with  a  partially  dissected  head  will  show,  however,  that  over  the 
vault  of  the  cranium  from  the  supra-orbital  ridges  to  the  nucha  the  general  shape  of 
the  skull  determines  the  surface  form  during  life,  the  flattened  muscles  and  aponeu- 
rosis closely  conforming  to  it.  In  the  temporal  regions,  in  spite  of  the  deep  bony 
fossa,  the  triangular  muscle  and  the  accompanying  fat  (page  491)  make  the  surface 
in  vigorous,  well-nourished  persons  slightly  convex.  The  outlines  of  the  muscle  can 
be  seen  when  it  is  in  contraction,  especially  the  portion  anterior  to  the  hairy  scalp. 

On  the  face  the  characteristics  that  distinguish  the  individual  are  due  largely 
to  the  presence  of  muscles  and  of  subcutaneous  fat.  The  edge  of  the  orbit  and  the 
naso-frontal  junction  are  covered  and  given  rounded  outlines  by  the  orbicularis 
palpebrarum  and  the  pyramidalis  nasi.  The  muscles  running  from  the  malar  bone 
and  maxilla  to  the  upper  lip  aid  the  buccinator  and  the  fat  of  the  cheek  in  filling  up 
the  great  hollows  beneath  the  malar  prominences.  The  orbicularis  oris  gives  shape 
and  expression  to  the  mouth.  The  masseter  fills  out  the  posterior  portion  of  the 
cheek  and  becomes  visible  in  outline  when  in  firm  contraction,  especially  the  vertical 
anterior  border,  just  in  front  of  which  the  facial  artery  crosses  the  inferior  maxilla. 

As  nearly  all  the  facial  muscles  have  fibres  of  insertion  into  the  facial  integument, 
their  influence  upon  expression  and  upon  the  creases  and  folds  that  become  perma- 
nent as  "wrinkles,"   "crows'  feet,"  etc.,  is  apparent. 

III.    THE  VAGO-ACCESSORY   MUSCLES. 

The  muscles  supplied  by  the  glosso-pharyngeal,  vagus,  and  spinal.,  accessory 
.nerves  may  be  grouped  together  both  on  account  of  their  relations  in  the  adult  and 
on  account  of  the  intimate  relations  which  exist  between  the  three  nerves.  The 
glosso-pharyngeal  and  vagus  correspond  to  the  posterior  branchial  arches,  the  glosso- 
pharyngeal to  that  represented  in  the  adult  by  the  greater  cornu  of  the  hyoid  bone 
and  the  vagus  to  those  represented  by  the  laryngeal  cartilages.  Consequently  we 
find  the  muscles  supplied  by  these  nerves  to  be  those  associated  with  the  pharynx 
and  larynx,  one  of  the  muscles  of  the  soft  palate,  the  levator  palati,  being  also 
included  in  the  group.  The  pharyngeal  muscles,  for  the  most  part,  are  supplied  from 
the  pharyngeal  plexus,  into  which  fibres  from  both  the  glosso-pharyngeal  and  vagus 
nerves  enter.  The  laryngeal  muscles,  however,  are  supplied  by  branches  coming 
directly  from  the  stem  of  the  vagus  nerve. 

The  spinal  accessory  nerve  stands  in  such  intimate  relations  with  the  vagus  that 
its  nucleus  of  origin  may  well  be  regarded  as  an  extension  of  that  of  the  vagus,  and 
by  the  union  of  a  portion  of  its  fibres  with  those  of  the  vagus  to  form  a  common 
trunk  opportunity  is  afforded  for  its  fibres  to  participate  in  the  formation  of  the 
pharyngeal  plexus,  and  there  is  evidence  pointing  to  the  origin  of  the  fibres  of  the 
inferior  laryngeal  nerve,  which  supplies  the  majority  of  the  laryngeal  muscles,  from 
the  spinal  accessory  nucleus. 

In  addition,  however,  to  its  participation  in  the  supply  of  the  pharyngeal  and, 
possibly,  the  laryngeal  muscles,  the  spinal  accessory  also  innervates  the  trapezius 
and  sterno-mastoid  muscles,  and  these,  on  account  of  their  relations,  must  constitute 
a  subgroup  distinct  from  the  other  vago-accessory  muscles. 

{a)  THE  MUSCLES   OF  THE   PALATE  AND  PHARYNX. 

1.  Stylo-pharyngeus.  5.  Palato-pharyngeus. 

2.  Levator  palati.  6.  Constrictor  pharyngis  superior. 

3.  Azygos  uvulae.  7.  Constrictor  pharyngis  medius. 

4.  Palato-glossus.  8.  Constrictor  pharyngis  inferior. 

1.    Stylo-Pharyngeus  (Figs.  502,  509). 

Attachments. — The  stylo-pharyngeus  arises  from  the  inner  surface  of  the 
styloid  process  near  its  base.      It  is  directed  downward,  the  glosso-pharyngeal  nerve 


496 


HUMAN   ANATOMY. 


covering  its  outer  surface,  passes  between  the  middle  and  superior  constrictors  of  the 
pharynx,  and,  being  joined  by  fibres  from  the  palato-pharyngeus,  is  ifiserted  into 
the  posterior  border  of  the  thyroid  cartilage  and  the  posterior  wall  of  the  pharynx. 

Nerve-Supply. — By  a  branch  of  the  glosso-pharyngeal  nerve. 

Action. — To  draw  upward  the  posterior  wall  of  the  pharynx  and  the  thyroid 
cartilage. 

2.    Levator  Palati  (Fig.  509). 

Attachments. — The  elevator  of  the  soft  palate  (m.  levator  veli  palatini)  arises 
from  the  under  surface  of  the  apex  of  the  petrous  portion  of  the  temporal  bone  and 
from  the  cartilaginous  portion  of  the  Eustachian  tube.      It  descends  obliquely  down- 


Fig.  509. 


Eustachian  tube 


Salpingo-      |      / 
pharyngeus — ™   - 


Levator  palati' 


Palato-pharyngeus =jg  wjj^-A"' 


Stylo-pharyngeus 


Posterior  crico-arytenoid 


Muscles  of  palate  and  pharynx,  seen  from  behind  ;  pharynx  laid  open. 


ward  and  forward,  and,  broadening  out,  enters  the  substance  of  the  soft  palate,  into 
the  aponeurosis  of  which  it  is  inserted. 

Nerve-Supply. — From  the  pharyngeal  plexus  by  fibres  which  probably  have 
their  origin  in  the  anterior  part  of  the  nucleus  of  the  spinal  accessory  nerve. 

Action. — To  elevate  the  soft  palate. 

3.    Azygos  UvuljE  (Fig.  509). 

Attachments. — The  azygos  uvulae  (m.  uvulae),  so  named  on  the  supposition 
that  it  was  an  unpaired  muscle,  consists  of  two  narrow  slips  which  arise  from  the 


THE   VAGO-ACCESSORY   MUSCLES.  497 

aponeurosis  of  the  soft  palate  and  from  the  posterior  nasal  spine.  They  pass  back- 
ward and  downward,  almost  parallel  with  each  other,  into  the  uvula  to  be  inserted 
into  its  aponeurosis. 

Nerve-Supply. — From  the  pharyngeal  plexus. 

Action. — To  raise  the  uvula. 

4.    Palatoglossus  (Fig.  1339). 

Attachments. — The  palato-glossus  (m.  glossopalatinus)  is  a  thin  sheet  which 
arises  from  the  under  surface  of  the  aponeurosis  of  the  soft  palate  and  descends  in 
the  anterior  pillar  of  the  fauces  (arcus  glossopalatinus)  to  be  inse7-ted  into  the  sides 
of  the  tongue,  mingling  with  the  fibres  of  the  stylo-glossus. 

Nerve-Supply. — From  the  pharyngeal  plexus,  probably  by  fibres  from  the 
anterior  part  of  the  nucleus  of  the  spinaLaccessory  nerve. 

Action. — To  raise  the  back  part  of  the  tongue  and  at  the  same  time  to  narrow 
the  fauces  by  causing  an  approximation  of  the  anterior  pillars.  Acting  from  below, 
it  will  depress  the  soft  palate. 

5.    Palato-Pharyngeus  (Fig.  509). 

Attachments. — The  palato-pharyngeus  (m.  pharyngopalatinus)  arises  from  the 
aponeurosis  of  the  soft  palate,  from  the  posterior  border  of  the  hard  palate,  and  also 
from  the  lower  portion  of  the  cartilage  of  the  Eustachian  tube.  It  passes  downward 
and  backward  in  the  posterior  pillar  of  the  fauces  (arcus  pharyngopalatinus),  internal 
to  the  superior  and  middle  constrictors  of  the  pharynx,  and  is  inserted  into  the  pos- 
terior border  of  the  thyroid  cartilage  and  into  the  posterior  wall  of  the  pharynx. 
That  portion  of  the  muscle  which  arises  from  the  cartilage  of  the  Eustachian  tube  is 
often  regarded  as  a  distinct  muscle  which  has  been  termed  the  salpingo-pharyngeus. 

Nerve-Supply. — From  the  pharyngeal  plexus,  probably  by  fibres  from  the 
anterior  part  of  the  nucleus  of  the  spinal  accessory  nerve. 

Action. — It  draws  the  pharynx  and  thyroid  cartilage  upward  and  at  the  same 
time  approximates  the  two  posterior  pillars  of  the  fauces.  Acting  from  below,  it 
will  depress  the  soft  palate. 

6.    Constrictor  Pharyngis  Superior  (Figs.  501,  510). 

Attachments. — -The  superior  constrictor  of  the  pharynx  forms  a  thin  quadri- 
lateral sheet  whose  origin  is  closely  associated  with  part  of  that  of  the  buccinator, 
there  being  usually  some  interchange  of  fibres  between  the  two  muscles.  It  arises 
from  the  lower  part  of  the  posterior  border  of  the  internal  pterygoid  plate  and 
from  its  hamulus,  from  the  posterior  border  of  the  pterygo-mandibular  ligament,  and 
is  thence  continued  upon  the  internal  oblique  line  of  the  mandible,  the  mucous  mem- 
brane of  the  mouth,  and  the  side  of  the  tongue.  The  uppermost  fibres  pass  in  a 
curve  backward  and  upward  and  are  inserted  into  the  pharyngeal  tubercle  of  the 
occipital  bone,  while  the  remainder  unite  with  the  muscle  of  the  opposite  side  in  a 
median  raphe  on  the  posterior  wall  of  the  pharynx. 

Nerve-Supply. — From  the  pharyngeal  plexus  by  fibres  which  probably  arise 
from  the  anterior  portion  of  the  nucleus  of  the  spinal  accessory  nerve. 

Action. — To  compress  the  pharynx. 

Relations. — Between  the  uppermost  fibres  of  the  muscle  and  the  base  of  the 
skull  is  an  interval  in  which  may  be  seen  the  levator  palati  and  the  Eustachian  tube. 
This  interval  has  been  termed  the  sinus  of  Morgagni,  and  is  closed  by  a  sheet  of 
connective  tissue  termed  the  fascia  pharyngobasilaris,  which  is  an  upward  prolonga- 
tion to  the  base  of  the  skull  of  the  pharyngeal  portion  of  the  bucco-pharyngeal 
fascia  (page  488). 

Externally  the  superior  constrictor  is  in  relation  above  with  the  internal  carotid 
artery,  the  vagus  nerve,  and  the  cervical  sympathetic,  and  below  with  the  upper 
part  of  the  middle  constrictor  and  the  stylo-pharyngeus.  Internally  it  is  lined  by 
mucous  membrane  throughout  the  greater  part  of  its  extent,  being  in  relation,  how- 
ever, with  the  tonsil  and  the  palato-pharyngeus  muscle. 

32 


498 


HUMAN   ANATOMY. 


Variations. — A  considerable  amount  of  independence  may  exist  between  the  bundles  of 
fibres  coming  from  different  portions  of  the  line  of  origin,  and  the  muscle  has  consequently  been 
described  as  consisting  of  various  portions  to  which  the  terms  pterygo-pharyngeus,  bucco- 
pharyugeus,  mylo-pharyngeus,  and  glosso-pharyngeus  have  been  applied. 

Not  infrequently  a  bundle  of  fibres  is  to  be'found  arising  from  the  basilar  portion  of  the 
occipital  bone  or  even  from  the  inferior  surface  of  the  petrous  portion  of  the  temporal  or  the  spine 
of  the  sphenoid,  and  passing  downward  to  be  inserted  along  with  the  pharyngo-palatinus.  A 
bundle  which  passes  from  the  cartilaginous  portion  of  the  Eustachian  tube  to  be  inserted  with 
the  palato-pharyngeus  has  been  termed  the  salpingo-pharyngeics. 


Internal  carotid  artery 
Internal  jugular 


Central  attachment  of  pharynx 


■  Lateral 

I    expan- 

'     sion  or 

pharynx 


Longitudinal  muscle  of  oesophagus 


Muscles  of  pharynx  from  behind  ;  portion  of  inferior  constrictor  has  been  removed. 

7.    Constrictor  Pharyngis  Medius  (Fig.  510). 
Attachments. — The  middle  constrictor  of  the  pharynx  is  a  fan-shaped  sheet 
which  arises  from  the  stylo-hyoid  ligament  and  both  cornua  of  the  hyoid  bone.      The 
fibres   pass  backward  to  be  inserted  into   the   pharyngeal   raphe,  the  upper  fibres 


THE   V AGO- ACCESSORY   MUSCLES.  499 

overlapping  the  lower  part  of  the  superior  constrictor  and  extending  in  some  cases 
almost  to  the  occipital  bone,  while  the  lower  fibres  are  overlapped  by  the  inferior 
constrictor. 

Nerve-Supply. — From  the  pharyngeal  plexus,  probably  by  fibres  from  the 
anterior  portion  of  the  spinal  accessory  nucleus.  It  is  said  to  be  supplied  also  by 
the  glosso-pharyngeal  nerve. 

Action. — To  compress  the  pharynx. 

Variations. — As  in  the  case  of  the  superior  constrictor,  the  fibres  from  different  parts  of 
the  origin  may  have  considerable  independence.  Thus  the  fibres  from  the  greater  cornu  of  the 
hyoid  have  been  recognized  as  a  muscle,  the  cerato-pharyngeus,  distinct  from  the  remainder,  to 
which  the  term  chondro-pharyngeus  has  been  applied. 

8.    Constrictor  Pharyngis  Inferior  (Figs.  501,  510). 

Attachments. — Like  the  middle  constrictor,  the  inferior  is  also  a  fan-shaped 
sheet  and  arises  from  the  outer  surface  of  the  thyroid  and  cricoid  cartilages  of  the 
larynx.  The  fibres  radiate  backward  to  be  inserted  into  the  pharyngeal  raphe,  the 
upper  ones  overlapping  the  lower  part  of  the  middle  constrictor,  while  the  lower 
ones  mingle  with  the  musculature  of  the  cesophagus. 

Nerve-Supply. — From  the  pharyngeal  plexus,  probably  through  fibres  from 
the  anterior  part  of  the  nucleus  of  the  spinal  accessory.  It  is  said  to  receive  also 
fibres  from  the  vagus  through  both  the  superior  and  inferior  laryngeal  nerves. 

Action. — To  compress  the  pharynx.  The  three  constrictors  of  the  pharynx 
play  important  parts  in  the  final  acts  of  deglutition,  forcing  the  food  towards  the 
cesophagus.  They  are  also  important  agents  in  producing  modulations  of  the  voice, 
since  the  pharynx  may  be  regarded  as  forming  a  resonator,  alterations  of  whose  form 
will  naturally  result  in  modifications  of  voice. 

Variations. — The  portions  of  the  muscle  arising  from  each  of  the  two  laryngeal  cartilages 
may  be  more  or  less  distinct  and  have  been  termed  the  thyro-pharyngeus  and  crico-pharyngeus. 

(6)   THE  MUSCLES   OF  THE   LARYNX. 

The  muscles  of  the  larynx  will  be  considered  in  connection  with  the  description 
of  that  organ  (page  1824). 

(c)   THE  TRAPEZIUS   MUSCLES. 

1.    Sterno-cleido-mastoideus.  2.    Trapezius. 

This  group  includes  but  two  muscles,  the  trapezius  and  sterno-cleido-mastoid, 
which  extend  from  the  skull  to  the  pectoral  girdle.  Both  are  in  reality  compound 
muscles,  formed  by  the  fusion  of  fibres  derived  from  the  branchiomeres  supplied  by 
the  spinal  accessory  with  portions  of  the  myotomes  supplied  by  the  second,  third, 
and  fourth  cervical  nerves.  Strictly  speaking,  therefore,  they  belong  only  partially 
to  the  series  of  branchiomeric  muscles,  but  the  union  of  the  elements  derived  from 
the  two  sources  is  so  intimate  that  any  attempt  to  distinguish  them  in  a  brief  descrip- 
tion of  the  muscles  would  tend  to  confusion. 

1.    Sterno-Cleido-Mastoideus  (Fig.  541). 

Attachments. — The  sterno-mastoid  is  attached  below  by  two  heads  to  the 
sternum  and  the  clavicle.  The  sternal  head  arises  by  a  strong  rounded  tendon  from 
the  anterior  surface  of  the  manubrium  sterni,  while  the  clavicular  head  is  more  band- 
like, and  takes  origin  from  the  upper  surface  of  the  sternal  end  of  the  clavicle. 
The  two  heads  are  directed  upward  and  backward,  the  clavicular  head  gradually 
passing  beneath  the  sternal  one,  and  the  two,  eventually  fusing,  are  inserted  into  the 
mastoid  process  of  the  temporal  bone  and  into  the  outer  part  of  the  superior  nuchal 
line. 


5oo 


HUMAN   ANATOMY. 


Nerve-Supply. — The  external  branch  of  the  spinal  accessory  and  the  second 

and  third  cervical  nerves. 

Action. — The  two  muscles  of  opposite  sides,   acting  together,    will   draw   the 

head  forward,  thus  bending  the  neck.      Acting  singly,  each  muscle  will  tend  to  draw 

the  head  towards  its  own  side  and  at  the  same  time  to  rotate  it  towards  the  opposite 

side. 

Relations. — Superficially  the  muscle  is  covered  by  the  platysma,  and  is  crossed 

obliquely  by  the  external  jugular  vein  and  in  varying  directions  by  the  superficial 

branches  of  the  cervical  plexus.  It  covers, 
above,  the  upper  part  of  the  posterior  belly  of 
the  digastric,  the  splenius  capitis,  the  levator 
scapulae  and  the  scaleni,  and  below  it  crosses 
the  omo-hyoid  and  covers  the  lower  attach- 
ments of  the  sterno-hyoid  and  sterno-thyroid. 
It  also  covers  the  common  carotid  artery  and 
the  lower  portions  of  the  external  and  internal 
carotids,  the  facial  and  internal  jugular  veins, 
the  cervical  plexus,  and  the  lateral  lobe  of  the 
thyroid  gland. 

:cipital 


Variations.— Considerable  variation  exists  in  the 
amount  of  fusion  of  the  two  heads,  their  complete 
distinctness  being  of  so  frequent  occurrence  as  to  be 
regarded  as  normal  by  some  authors.  But,  in  ad- 
dition to  these  two  portions,  the  muscle  presents  fre- 
quently a  separation  into  other  parts,  and  compara- 
tive anatomy  reveals  a  primary  constitution  of  the 
muscle  from  at  least  five  distinct  portions,  any  one 
or  more  of  which  may  appear  as  distinct  bundles 
(Fig.  511).  These  portions  are  arranged  in  two 
layers,  the  superficial  one  consisting  of  a  superficial 
s/erno-mastoid,  a  sterno-occipital,  and  a  cleido- 
occipital  portion,  while  the  deep  one  is  formed  by 
a  deep  sterno-mastoid  and  a  cleido-mastoid  portion, 
the  names  applied  indicating  the  attachments  of  the 
various  bundles. 

Occasionally  the  lower  portion  of  the  muscle 
is  traversed  by  a  tendinous  intersection,  a  peculiarity  of  interest  in  connection  with  the  formation 
of  the  muscle  by  the  fusion  of  portions  derived  from  different  myotomes. 


Quadricipital  type  of  sterno-mastoid,  showing  the 
components  of  the  muscle.     {After  Maubrac.) 


2.    Trapezius  (Figs.  512,  559). 

Attachments. — The  trapezius  is  the  most  superficial  muscle  upon  the  dorsal 
surface  of  the  body,  and  is  a  triangular  sheet  whose  base  corresponds  with  the  mid- 
dorsal  line.  The  two  muscles  of  opposite  sides  being  thus  placed  base  to  base,  form 
a  rhomboidal  sheet  which  covers  the  nape  of  the  neck  and  the  upper  part  of  the  back 
and  shoulders,  resembling  somewhat  a  monk's  cowl,  whence  the  name  cucullaris 
sometimes  applied  to  the  muscle. 

It  arises  above  from  the  superior  nuchal  line  and  the  external  occipital  pro- 
tuberance, and  thence  along  the  ligamentum  nuchae  and  the  spinous  processes  of 
the  seventh  cervical  and  all  the  thoracic  vertebrae,  together  with  the  supraspinous 
ligaments.  The  upper  fibres  pass  downward  and  outward,  the  middle  ones  directly 
outward,  and  the  lower  ones  upward  and  outward,  and  are  inserted,  the  upper  ones 
into  the  outer  third  of  the  posterior  border  of  the  clavicle,  the  middle  ones  into  the 
inner  border  and  upper  surface  of  the  acromion  process  and  the  upper  border  of  the 
spine  of  the  scapula,  and  the  lower  ones  into  a  tubercle  at  the  base  of  the  scapular 
spine. 

Throughout  the  greater  part  of  its  length  the  origin  of  the  muscle  is  by  short 
tendinous  fibres  intermingled  with  muscle-tissue,  but  from  about  the  middle  of  the 
ligamentum  nucha?  to  the  spinous  process  of  the  second  thoracic  vertebra  it  is  entirely 
tendinous.  Furthermore,  throughout  the  upper  half  of  this  portion  of  the  origin  the 
tendinous  fibres  gradually  increase  in  length  and  throughout  its  lower  half  they  again 
diminish,  so  that  there  is  formed  by  the  two  muscles  of  opposite  sides,  in  this  region, 


THE   VAGO-ACCESSORY    MUSCLES. 


501 


a  well-marked  oval  or  rhomboidal  tendinous  area,  which  has  been  termed  the  oval 
aponeurosis. 

In  their  course  to  their  insertion  the  lower  fibres  pass  over  the  smooth  surface 
at  the  base  of  the  spine  of  the  scapula,  and  sometimes  a  bursa  mucosa  is  developed 
between  the  bone  and  the  muscle. 

Nerve-Supply. — From  the  external  branch  of  the  spinal  accessory  and  from 
the  third  and  fourth  cervical  nerves. 

Action. — Acting  from  above,  the  upper  fibres  draw  upward  the  point  of  the 
shoulder,  while,  acting  from  below,  they  draw  the  head  backward.     The  middle  and 

lower  fibres  draw  the  scapula  towards  the 
pIG    rI2  mid-dorsal    line   and   at   the   same    time 

rotate  it  so  as  to  raise  the  point  of  the 
shoulder. 


Sterno-mastoid 

Aponeurosis  of  trapezius 
Trapezius 

V.  Acromion 


Variations.— Like  the  sterno-mastoid,  the 
trapezius  is  a  compound  muscle  consisting  of 
three  distinct  portions.  That  portion  of  the 
muscle  which  inserts  into  the  tuberosity  of  the 


Fig 


Latissimus  ilorsi 


-Cleido-occipitalis  cervicalis 
..    -Clav'->- 

-\ Acromion 

/        Dorso-scapula 
superior 

Tuberosity  of  spine 

Tendinous  slip  to 

infraspinous  fascia 
Dorso-scapularis  inferior 


Superficial  dissection  of  back,  showing  trapezius 
and  adjacent  muscles. 


Components  of  human  trapezius  muscle. 
{Streissler.) 


scapular  spine  represents  what  is  termed  in  the  lower  mammals  the  dorso-scapularis  inferior, 
while  the  portion  which  inserts  into  the  spine  and  acromion  process  represents  the  dorso-scap- 
ularis superior.  The  clavicular  portion,  on  the  other  hand,  is  in  the  lower  forms  associated  with 
the  cleido-occipitalis  element  of  the  sterno-cleido-mastoid,  and  may  therefore  be  termed  the 
cleido-occipitalis  cervicalis. 

Indications  of  this  triple  constitution  are  to  be  seen  in  a  more  or  less  distinct  separation  of 
the  clavicular  portion  of  the  muscle  from  the  rest  and,  less  frequently,  by  a  separation  of  the 
lower  from  the  middle  portion  (Fig.  513).  Occasionally,  too,  bundles  pass  from  the  anterior 
border  of  the  clavicular  portion  to  join  the  cleido-occipitalis  portion  of  the  sterno-cleido-mastoid, 
indicating  the  common  origin  of  the  two  muscles.  Variations  likewise  occur  in  the  extent  of 
the  spinal  attachment  of  the  trapezius,  owing  to  the  reduction  of  one  or  other  of  its  parts,  and  it 
may  be  remarked  that  this  attachment  usually  extends  lower  in  the  muscle  of  the  right  side 
than  in  that  of  the  left. 

Of  especial  interest  from  the  comparative  stand-point  is  the  occasional  existence  of  a  bundle 
of  fibres  which  lies  beneath  the  cervical  portion  of  the  trapezius,  and  is  attached  at  one  extremity 
to  the  outer  end  of  the  clavicle  or  to  the  acromion  process  and  above  to  the  transverse  processes 
of  some  of  the  upper  cervical  vertebra;,  usually  the  atlas  and  axis.  It  is  apparently  the  equivalent 
of  the  omo-transversarius  of  the  lower  mammals,  a  muscle  which  is  closely  associated  with  the 
members  of  the  trapezius  group. 


5°2 


HUMAN    ANATOMY. 


THE  METAMER1C  MUSCLES. 


A.     THE   AXIAL   MUSCLES. 


As  has  been  pointed  out.  the  history  of  the  anterior  two  groups  of  myotomes, 
supplied  by  cranial  nerves,  differs  somewhat  from  that  of  the  remaining  ones,  and 
it  is  convenient,  therefore,  to  consider  the  muscles  derived  from  these  myotomes 
separately  from  the  rest. 


I.     THE   ORBITAL   MUSCLES. 


i.   Levator  palpebral  superioris. 

2.  Rectus  superior. 

3.  Rectus  internus. 


7.    Obliquus  inferior. 


4.  Rectus  inferior. 

5.  Rectus  externus. 

6.  Obliquus  superior. 


The  most  anterior  of  the  persistent  myotomes  are  three  in  number,  supplied  by 
the  oculo-motor,  trochlear,  and  abducent  nerves.  They  give  rise  to  the  muscles 
situated  in  the  orbit. 


1.    Levator  Palpebrae  Superioris  (Fig.  516). 

Attachments. — The  levator  palpebrae  superioris  is  a  rather  slender  muscle 
which  lies  in  the  greater  portion  of  its  course  immediately  beneath  the  periosteal 
lining  of  the  roof  of  the  orbit.      It  arises  at  the  back  of  the  orbit,  a  short  distance 

above  the  upper  margin  of 
Fig.  514.  the  optic  foramen,  and  is 

directed  forward,  broad- 
ening as  it  goes,  to  be  in- 
sertedby  a  broad  aponeu- 
rosis principally  into  the 
upper  border  of  the  tarsal 
plate  of  the  upper  eye- 
lid, the  uppermost  fibres 
mingling  somewhat  with 
those  of  the  palpebral 
portion  of  the  orbicularis 
oculi. 

The  aponeurosis  by 
which  the  levator  inserts 
into    the    tarsal    plate    is 
largely  composed  of  non- 
striated   muscular  fibres, 
which  constitute  what  has 
been   termed    the  orbito- 
palpebral  muscle.      This 
is    triangular    in    shape, 
with  the  truncated   apex 
united  to  the  levator  and 
with    the    base   attached 
to  the  external  palpebral 
raphe,  the  tarsal  plate  of  the  upper  eyelid,  and  the  internal  palpebral  ligament. 
Nerve-Supply. — From  the  oculo-motor  nerve. 
Action. — To  draw  the  upper  eyelid  upward  and  backward. 
Relations. — Immediately  above  the  levator  palpebrae  superioris,  between  it  and 
the  periosteum  of  the  roof  of  the  orbit,  are  the  trochlear  and  frontal  nerves  and  the 
supra-orbital  vessels.      Below  it  rests  upon  the  medial  half  of  the  rectus  superior. 


Superior  obliq' 
proximal  part 


Levator  palpebrae  sup. 
.Upper  tarsal  plate 
Palpebral  fissure 

Superior  rectus 

Inferior  oblique 

H.xUTiial  rectus 


Stump  of  levator 
palpebrae  superioris 


Ocular  muscles  seei 
upper  < 


THE   AXIAL    MUSCLES. 


503 


2.  Rectus  Superior  (Fig.  514). 

Attachments. — The  superior  rectus  arises  from  the  upper  portion  of  a  fibrous 
ring  termed  the  annulus  of  Zinn  (annulus  tendineus  communis),  which  surrounds  the 
optic  foramen  and  is  formed  by  a  thickening  of  the  orbital  periosteum  in  that  region. 
Thence  the  muscle  is  directed  forward  over  the  eyeball  and  is  inserted  into  the 
sclera  a  little  above  the  upper  margin  of  the  cornea. 

Nerve-Supply. — From  the  oculo-motor  nerve. 

Action. — To  rotate  the  eyeball  so  that  the  pupil  is  directed  upward  and  at  the 
same  time  somewhat  inward. 

3.  Rectus  Internus  (Fig.  514). 

Attachments. — The  internal  rectus  (m.  rectus  medialis)  arises  from  the  inner 
portion  of  the  annulus  tendineus  communis  and  passes  forward  along  the  inner  wall 
of  the  orbit  to  be  inserted  into  the  sclera  a  short  distance  behind  the  inner  margin  of 
the  cornea. 

Nerve-Supply. — From  the  oculo-motor  nerve. 

Action. — To  rotate  the  eyeball  so  that  the  pupil  is  directed  inward. 


Fig.  515. 


Supe 


External  rectus. 

Optic  nerve  (cut) 

Sphenomaxillary  fissure. 

Inferior  oblique. 


Levator  palpebrae  superioris 
Superior  oblique 

/  Trochlea,  tendon  of  superior 

oblique  in  place 


InU'l'lKll  rectus 


Right  orbit  seen  from  before,  showing  stumps  of  < 


cles  attached  to  common  tendii 


4.  Rectus  Inferior  (Fig.  516). 

Attachments. — The  inferior  rectus  arises  from  the  lower  portion  of  the  com- 
mon tendinous  ring,  its  line  of  origin  being  continuous  with  that  of  the  rectus  internus. 
It  is  inserted  into  the  sclera  a  short  distance  below  the  inferior  margin  of  the  cornea. 

Nerve-Supply. — From  the  oculo-motor  nerve. 

Action. — To  rotate  the  eyeball  so  that  the  pupil  is  directed  downward  and  at 
the  same  time  somewhat  inward. 

5.  Rectus  Externus  (Fig.  514). 

Attachments. — The  external  rectus  (m.  rectus  lateralis)  arises  by  two  heads, 
one  of  which  is  attached  to  the  lower  and  outer  portion  of  the  common  tendinous  ring 
and  to  the  spine  on  the  lower  border  of  the  sphenoidal  fissure,  and  the  other  to  the 
upper  and  outer  part  of  the  common  tendinous  ring.  It  passes  along  the  outer  wall 
of  the  orbit  and  is  inserted  into  the  sclera  a  little  behind  the  outer  border  of  the  cornea. 

Nerve-Supply. — From  the  abducens  or  sixth  nerve. 

Action. — To  rotate  the  eyeball  so  that  the  pupil  is  directed  outward. 

Relations. — Between  the  two  heads  of  the  external  rectus  there  pass  the  oculo- 
motor, nasal,  and  abducent  nerves  and  the  ophthalmic  vein. 


504 


HUMAN    ANATOMY. 


6.    Obliquus  Superior  (Figs.  514,  516). 

Attachments. — The  superior  oblique  muscle  of  the  eyeball  arises  a  little  in. 
front  of  the  inner  part  of  the  optic  foramen  and  passes  forward  along  the  upper  and 
inner  wall  of  the  orbit  to  terminate  in  a  round  tendon  which  passes  through  a  ten- 
dinous loop,  the  trochlea,  attached  to  the  fovea  trochlearis  of  the  frontal  bone. 
Thence  it  is  reflected  outward,  downward,  and  backward,  and,  passing  beneath  the 
superior  rectus,  is  inserted  into  the  sclera  beneath  the  outer  margin  of  that  muscle 
and  at  about  the  equator  of  the  eyeball. 

Nerve-Supply. — From  the  trochlearis  or  fourth  nerve. 

Action. — To  rotate  the  eyeball  so  that  the  pupil  is  directed  inward  and 
downward. 

Fig.  516. 


Levator  palpebral  superioris 


Superior  oblique 
Superior  rectus 
External  rectus  (cut). 
Internal  rec 
Optic  nerv 
Stump  of  external  rectus  v 


Inferior  rectus 


Insertion  of  levator  palpebral 
superioris  into  upper  tarsal 
plate 


Inferior  oblique 


Lateral  view  of  ocular  muscles  after  removal  of  outer  wall  of  orbit ;  elevator  of  upper  lid  has  been  pulled 
upward  and  inward. 

7.    Obliquus  Inferior  (Fig.  516). 

Attachments. — The  inferior  oblique  muscle  arises  near  the  margin  of  the 
orbit  from  a  small  depression  on  the  orbital  surface  of  the  maxilla.  It  is  directed  out- 
ward, backward,  and  upward,  and,  passing  between  the  inferior  rectus  and  the  floor 
of  the  orbit,  is  inserted,  into  the  sclera  a  little  behind  the  equator  of  the  eyeball  and 
under  cover  of  the  external  rectus. 

Nerve-Supply. — From  the  oculo-motor  nerve. 

Action. — To  rotate  the  eyeball  so  that  the  pupil  is  directed  upward  and  outward. 

Fasciae  of  the  Orbit. — The  muscles,  nerves,  and  vessels  of  the  orbit  are  em- 
bedded in  a  mass  of  loose  areolar  tissue  which,  abundantly  intermingled  with  a  soft 
fat,  completely  fills  the  orbital  cavity.  Around  the  vessels,  nerves,  and  muscles  this 
areolar  tissue  condenses  to  form  their  sheaths,  and  a  special  condensation,  the 
capsule  of  Tenon  (fascia  bulbi),  surrounds  the  posterior  four-fifths  of  the  eyeball, 
forming  a  socket  for  it.  The  inner  surface  of  this  capsule  is  smooth  and  is  united  to 
the  outer  surface  of  the  sclera  only  by  lax  and  slender  bands  of  fibres  which  traverse 
a  distinct  lymph-space  termed  the  space  of  Tenon  (spatium  interfasciale),  which  inter- 
venes between  the  capsule  and  the  eyeball,  thus  facilitating  the  movements  of  the 
latter  in  the  socket.  Posteriorly  the  capsule  is  continuous  with  the  sheath  of  the 
optic  nerve  and  anteriorly  it  joins  with  the  conjunctiva  anterior  to  the  line  of  insertion 
of  the  rectus  muscles  into  the  sclera.  The  tendons  of  the  rectus  muscles  conse- 
quently perforate  the  capsule,  which  is  prolonged  backward  upon  the  tendons  for  a. 
short  distance, — in  the  case  of  the  superior  oblique  as  far  as  the  trochlea.— -and  then 
becomes  continuous  with  the  areolar  sheaths  of  the  muscles  which  are  intimately 


THE   AXIAL   MUSCLES. 


505 


adherent  to  the  muscle-tissue  and  constitute  the  fasciae  musculares.  These  fasciae  are 
somewhat  thicker  in  their  anterior  portions  than  more  posteriorly,  and  give  off  pro- 
longations to  neighboring  parts.  From  the  fascia  of  the  rectus  superior  a  prolonga- 
tion passes  to  join  the  tendon  of  the  levator  palpebrae  superioris,  and  one  from  the 
rectus  inferior  passes  to  the  lower  border  of  the  tarsal  plate  of  the  lower  eyelid,  these 
two  recti  thus  acquiring  a  certain  amount  of  action  upon  the  eyelids.  From  the 
lateral  surface  of  the  fascia  of  the  external  rectus  a  rather  strong  prolongation  is 
given  off  which  attaches  to  the  orbital  surface  of  the  zygomatic  bone,  forming  what 
has  been  termed  the  external  check  'ligament  of  the  eyeball,  while  from  the  medial 
surface  of  the  fascia  of  the  internal  rectus  a  similar,  although  somewhat  laxer,  prolon- 
gation passes  to  the  crest  of  the  lachrymal  bone  and  the  reflected  portion  of  the 
internal  palpebral  ligament. 

The   Movements  of  the   Eyeball. — The  four  recti  muscles  of  the  eyeball 
may  be  regarded  as  forming  a  cone  whose  apex  is  at  the  annulus  tendineus  communis 

Fig.  517. 


Levator  palpebrae  superioris 

Fat        \  /; 


Superior  rectus 
Capsule  of  Tenon 
Superior  obliqu 
Fat 
Opt 

\ 


Septum  orbitale 


Ww 

N^  ^  /    Upper  fornix  of  conjunctiva 
Upper  tarsal  plate 


Space  of  Tenon 


Inferior  rectus 

Inferior  oblique 


Diagrammatic  sagittal  section  through  orbit,  showing  relations  of  fascia  to  muscles,  eyeball,  and  orbital 


and  the  base  at  the  insertions  of  the  muscles  into  the  sclera.  The  line  joining  the 
insertions  of  the  muscles  is  not,  however,  a  circle,  but  rather  a  spiral,  the  insertion 
of  the  internal  rectus  being  nearest  to  and  that  of  the  rectus  superior  farthest  from 
the  edge  of  the  cornea.  The  axis  of  the  cone  does  not  correspond  in  direction  with 
the  antero-posterior  axis  of  the  eyeball,  but,  owing  to  the  divergence  of  the  axes  of 
the  two  orbits,  is  inclined  to  it  from  within  outward  at  an  angle  of  about  200. 

It  follows  from  this  that  during  the  contraction  of  either  the  superior  or  infe- 
rior rectus  the  axis  of  rotation  of  the  eyeball  will  not  coincide  with  its  transverse 
axis,  but  will  be  inclined  to  it  (Fig.  518),  and  consequently  the  action  of  either  of 
these  muscles  in  directing  the  pupil  upward  or  downward  will  be  complicated  by  a 
certain  amount  of  oblique  movement,  in  the  one  case  inward  and  in  the  other  case 
outward.  In  producing  purely  upward  or  downward  movements  of  the  pupil  the 
rectus  muscles  are  associated  with  the  oblique  ones,  the  coordination  of  the  inferior 
oblique  with  the  superior  rectus  producing  a  purely  upward  rotation,  while  that  of  the 
superior  oblique  with  the  inferior  rectus  produces  a  purely  downward  movement. 


506 


HUMAN   ANATOMY. 


Fig.  518. 


It  has  been  demonstrated  also  that  the  oblique  movements  of  the  eyeball  are  by 
no  means  due  to  the  action  of  the  superior  and  inferior  oblique  muscles  acting  alone, 

but  that  in  every  such  movement  there  is 
a  coordination  of  two  of  the  recti  muscles 
with  one  of  the  obliques.  Thus,  in  rotations 
which  direct  the  pupil  upward  and  inward 
the  superior  and  internal  recti  cooperate  with 
the  inferior  oblique,  and  in  the  downward 
and  outward  movements  the  inferior  and 
external  recti  cooperate  with  the  superior 
oblique. 

A  purely  outward  or  inward  rotation 
can  be  produced  by  the  action  of  the  external 
or  internal  rectus,  as  the  case  may  be.  But 
it  is  to  be  noted  that  the  movements  of  the 
eyeball  are  always  bilateral,  and  that  the  in- 
ward rotation  of  the  one  eye  is  generally  as- 
sociated with  the  outward  rotation  of  the 
other,  the  combined  movements  thus  re- 
quiring the  cooperation  of  different  muscles. 
In  all  movements  of  the  eyeballs  there 
is,  accordingly,  a  coordination  of  various 
orbital  muscles,  and  when  the  combined 
oblique  movements  are  performed  this  co- 
ordination becomes  somewhat  complicated. 
The  direction  of  both  pupils  upward  and  to 
the  right  requires  the  coordination  in  the 
right  eye  of  the  inferior  oblique  and  the  su- 
perior and  external  recti  and  in  the  left  eye  of  the  inferior  oblique  and  the  superior 
and  internal  recti. 


Diagram  showing  action  of  ocular  muscles.  .^.Si, 
QyQiy  sagittal  and  transverse  axes  of  eyeball;  di- 
rection of  pull  of  muscles  is  indicated  by  lines ; 
dotted  lines  indicate  axes  around  which  superior 
and  inferior  recti  and  oblique  muscles  rotate  eye- 
ball;  vertical  axis  (O)  corresponds  to  axis  of  rota- 
tion of  internal  and  external  recti.     (Laridois.) 


Variations. — But  few  variations  have  been  observed  in  the  orbital  muscles.  Absence 
of  the  levator  palpebrae  superioris  has  been  noted,  and  a  slip  from  this  muscle,  termed  the 
tensor  trochlea,  sometimes  passes  to  the  trochlea. 


II.    THE   HYPOGLOSSAL   MUSCLES. 


Genio-glossus. 
Hyo-glossus. 


3.  Stylo-glossus. 

4.  Lingualis. 


It  is  well  known  that  the  hypoglossal  nerve  represents  the  anterior  roots  of 
three  spinal  nerves  which  have  secondarily  been  taken  up  into  and  consolidated  with 
the  cranial  region.  Corresponding  to  these  three  nerves  are  three  myotomes  which 
combine  to  give  rise  to  muscles  connected  with  the  tongue. 

1.   Genio-Glossus  (Fig.  1339). 
The  genio-glossus  is  described  with  the  tongue  (page  1578). 

2.    Hyo-Glossus  (Fig.  1339). 
The  hyo-glossus  is  described  with  the  tongue  (page  1578). 


Variations. — The  fibres  which  arise  from  the  lesser  cornu  of  the  hyoid  bone  are  frequently 
separate  from  the  rest  of  the  muscle  and  have  been  described  as  the  chondro-glossus,  and  the 
fibres  arising  from  the  body  of  the  hyoid  are  frequently  separated  by  a  distinct  interval  from 
those  arising  from  the  greater  cornu,  the  former  constituting  a  muscle  which  has  been  termed 
the  basio-glossus  and  the  latter  the  cerato-glossus.  A  bundle  of  fibres,  forming  what  has  been 
termed  the  triticeo-glossus,  sometimes  arises  from  the  cartilago  triticea,  situated  in  the  lateral 
hvo-thyroid  ligament,  and  passes  upward  and  forward  to  insert  along  with  the  posterior  fibres 
of  the  hyo-glossus. 


THE  TRUNK   MUSCLES.  507 

3.   Stylo-Glossus  (Fig.  1339). 

The  styloglossus  is  described  with  the  tongue  (page  1579). 

Variations. — The  styloglossus  is  occasionally  absent,  and  may  in  such  cases  be  replaced 
by  a  mylo-glossus,  which  arises  from  the  inner  surface  of  the  angle  of  the  mandible  or  from  the 
stylo-mandibular  ligament  and  is  inserted  into  the  sides  and  under  surface  of  the  tongue. 
This  muscle  is  usually  present  in  the  form  of  some  small  bundles  of  fibres  having  the  attach- 
ments described. 

4.    LlNGUALIS  (Fig.    1340). 

The  lingualis  is  described  with  the  tongue  (page  1579). 

III.    THE   TRUNK   MUSCLES. 

THE  DORSAL  MUSCLES. 

In  employing  the  term  dorsal  to  indicate  a  group  of  muscles  it  must  be  clearly 
understood  that  the  group  does  not  include  all  the  muscles  which,  in  the  adult  con- 
dition, are  found  upon  the  dorsal  surface  of  the  body.  The  term,  so  far  as  it  has 
a  topographic  significance,  refers  to  a  phylogenetic  stage  in  which  the  muscles  it  is 
intended  to  designate  were  the  only  dorsal  muscles,  and,  as  here  employed,  it  indi- 
cates only  those  muscles  which  are  derived  from  the  dorsal  portions  of  the  embryonic 
myotomes  and  are  supplied  by  the  posterior  divisions  (dorsal  rami)  of  the  spinal 
nerves. 

An  examination  of  the  muscles  of  the  back  readily  shows  that  they  consist  of 
two  distinct  sets.  There  is  a  superficial  set,  consisting  of  broad  and  flat  muscles, 
which  are,  with  few  exceptions,  attached  to  the  skeleton  of  the  fore-limb,  and  a 
deeper  set,  consisting  of  elongated  and  relatively  thick  muscles,  whose  attachments 
are  confined  to  portions  of  the  axial  skeleton.  The  muscles  of  the  former  set,  which 
may  conveniently  be  designated  the  spino-humeral  muscles,  are  all  supplied  by 
branches  from  the  ventral  rami  of  the  spinal  nerves  ;  they  have  reached  their 
present  position,  in  which  they  almost  completely  cover  in  the  true  dorsal  muscles, 
by  a  secondary  migration  from  the  more  ventral  portions  of  the  trunk,  and  prop- 
erly belong  to  the  system  of  limb  muscles,  in  connection  with  which  they  will  be 
described. 

The  true  axial  dorsal  muscles  are  all  included  in  the  deeper  set.  Viewed  from 
the  surface,  they  appear  to  form  elongated  columns  of  muscle-tissue,  extending  con- 
tinuously, more  or  less  parallel  with  the  spinal  column,  over  considerable  stretches 
of  the  back  ;  but  when  the  more  superficial  portions  of  the  columns  are  removed,  it 
will  be  seen  that  the  deeper  portions  are  associated  with  the  individual  vertebra?, 
their  fibres  possessing  a  more  or  less  distinct  segmental  arrangement.  The  columns, 
indeed,  are  to  be  regarded  as  formed  by  the  fusion  of  a  number  of  originally  inde- 
pendent muscle-segments,  derived  from  the  dorsal  portions  of  a  corresponding 
number  of  myotomes,  a  mode  of  formation  also  indicated  by  the  fact  that  the 
columns  are  supplied  by  nerves  from  a  greater  or  less  number  of  successive  spinal 
nerves,  from  just  as  many,  indeed,  as  there  are  myotomes  entering  into  their 
composition. 

Comparative  anatomy  demonstrates  that  the  dorsal  musculature  may,  further- 
more, be  regarded  as  consisting  of  two  parallel  portions  or  tracts,  a  median  and  a 
lateral.  The  former  portion,  which  includes  the  majority  of  the  dorsal  muscles,  is 
composed  of  those  muscles  which  fundamentally  arise  from  the  transverse  processes 
of  the  vertebra?  and  are  inserted  into  the  spinous  processes,  and  may  therefore  be 
termed  the  transversospinal  portion  ;  while  the  more  lateral  tract  consists  of  mus- 
cles which,  taking  their  origin  primarily  from  the  transverse  processes,  are  inserted 
into  the  ribs  or  their  homologues,  and  may  accordingly  be  termed  the  transverso- 
costal  portion.  A  certain  amount  of  overlapping  of  the  median  tract  by  the  lateral 
one  occurs  in  man  ;  indeed,  in  the  lumbar  region  the  two  tracts  fuse  to  a  certain 
extent  to  form  the  sacro-spinalis  ;  but  throughout  the  thoracic  and  cervical  regions 
they  are  fairly  distinct. 


5°8 


HUMAN    ANATOMY. 


Psoas  magnus 
Lumbar  vertebra 


The  deep  fascia  of  the  back  invests  all  the  muscles  of  the  dorsal  group, 
separating  them  from  the  spino-humeral  group.  Above,  the  fascia  is  not  especially 
strong,  and  in  the  cfervical  and  upper  thoracic  regions  forms  what  is  termed  the 
fascia  nuchae,  which  lies  beneath  the  trapezius  and  rhomboid  muscles.  In  the  lower 
thoracic  and  lumbar  regions,  however,  the  fascia  becomes  considerably  thickened, 
especially  that  portion  which  invests  the  sacro-spinalis  (vertebral  apo?ieurosis) ,  form- 
ing a  strong  rhomboidal  sheet  extending  from  about  the  level  of  the  sixth  thoracic 
vertebra  to  the  tip  of  the  sacrum,  its  anterior  borders  giving  attachment  to  various 
muscles,  while  the  posterior  ones  are  attached  to  the  posterior  portions  of  the  iliac 

crests,  where  it  becomes  contin- 
Fig.  519.  uous  with  the  fascia  lata  covering 

the  gluteal  muscles. 

This  dense  layer  is  termed 
the  fascia  lumbo-dorsalis  (Fig. 
559),  and  is  generally  regarded 
as  consisting  of  two  lateral  por- 
tions which  are  practically  united 
in  the  mid-dorsal  line  by  their 
common  attachment  to  the  spi- 
nous processes  of  the  vertebrae 
and  the  supraspinous  ligaments. 
Each  of  these  lateral  portions  is 
again  considered  as  consisting 
of  two  layers  which  together 
invest  the  sacro-spinalis  (Fig. 
519),  the  posterior  layer  being 
that  which  has  already  been  described,  while  the  ajiterior  layer  is  attached  medially 
to  the  tips  of  the  transverse  processes  of  the  lumbar  vertebrae,  above  to  the  lower 
border  of  the  twelfth  rib,  and  below  to  the  crest  of  the  ilium.  It  passes  outward 
beneath  the  sacro-spinalis,  separating  it  from  the  quadratus  lumborum,  and  at  the 
outer  border  of  the  former  muscle  it  fuses  with  the  posterior  layer  to  form  a  strong 
aponeurotic  band,  from  which  the  latissimus  dorsi  and  the  internal  oblique  and  trans- 
verse abdominal  muscles  take  partial  origin,  and  which  is  continued  ventrally  over 
the  inner  surface  of  the  transversus  abdominis  as  the  fascia  transfer  sails. 


Lumbar  spi 


Subperitoneal  tissue 

Fascia        Peritoneum 

Transversalis  fascia 

Transversalis  muscl 
Internal  oblique 
External  oblique 

Triangle  of  Petit 
uadratus  lumborum 

simus  dorsi 
Ant.  layer  of  lumbo-dorsal  fascia 
Superficial  fascia 
Posterior  layer  of  lumbo-dorsal  fascia 


Skin    Sacro-spinalis 


Diagram  showing  formation  and  relations  of  lumb> 
to  muscles  of  body-wall. 


(a)    THE  TRANSVERSO-COSTAL  TRACT. 

3.    Lonoissimus. 


Sacro-spinalis. 
Ilio-costalis. 


4.    Splenius. 


1.    Sacro-Spinalis  (Fig.  520). 

Attachments. — The  sacro-spinalis,  sometimes  termed  the  erector  spines,  forms 
a  large  muscular  mass  occupying  the  lumbar  portion  of  the  vertebral  groove.  It 
takes  its  origin  from  the  under  surface  of  the  lumbo-dorsal  fascia,  the  crest  of 
the  ilium,  the  posterior  surface  of  the  sacrum,  and  the  spines  of  the  lumbar  ver- 
tebrae. Anteriorly  it  divides  into  three  separate  muscles,  two  of  which,  the  ilio- 
costalis  and  the  longissimus,  belong  to  the  transverso-costal  group,  while  the  third, 
the  spinalis,  is  a  member  of  the  transverso-spinal  series. 

Nerve-Supply. — The  posterior  divisions  of  the  lumbar  nerves. 


2.    Ilio-Costalis  (Fig.  520). 

Attachments. — The  ilio-costalis,  also  termed  the  sacro-lumbalis,  is  the  most 
lateral  of  the  three  muscles  into  which  the  sacro-spinalis  divides,  and  is  the  forward 
continuation  of  the  portion  of  that  muscle  which  arises  from  the  crest  of  the  ilium. 
The  muscle  is  continued  upward  in  the  vertebral  groove  immediately  internal  to  the 
angles  of  the  ribs  as  far  as  the  fourth  cervical  vertebra,  receiving,  however,  acces- 
sions from  the  ribs  as  it  passes  over  them.      The  fibres  which  arise  from  the  iliac 


THE   TRUNK    MUSCLES. 


509 


Fig.  520. 


Obliquus  super 


Spinalis  coll 
Cervicalis  ascendem 
Transversalis  cervicis 


Spinalis  d 


Longissimus  dorsi — -^ 


Ilio-costali; 
<ilio-costalis  lumborum) 


-Quadratus  lumborun 


_Multifidus  spina? 


Dissection  of  muscles  of  back,  showing  transverso-costal  and  transverso-spinal  tracts. 


510  HUMAN    ANATOMY. 

crest  are  mainly  inserted  into  the  lower  six  or  seven  ribs,  and  form  what  is  termed  the 
ilio-costalis  luinborum.  With  the  remainder  of  the  iliac  fibres  bundles  arising  from 
the  lower  five,  six,  oY  seven  ribs  associate  themselves  to  form  the  ilio-costalis  dorsi, 
also  termed  the  accessorius,  which  inserts  into  the  upper  five  or  six  ribs  ;  and,  finally, 
the  uppermost  portion  of  the  muscle,  the  ilio-costalis  cervicis  or  ccrvicalis  ascendens,  is 
formed  by  the  union  of  bundles  arising  from  the  upper  six  or  seven  ribs,  and  is  in- 
serted into  the  posterior  tubercles  of  the  transverse  processes  of  the  fourth,  fifth,  and 
sixth  cervical  vertebra?. 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
lower  cervical  to  the  first  lumbar. 

Action. — The  various  portions  of  the  ilio-costalis  tend  to  bend  the  spinal 
column  backward  in  the  lower  cervical,  thoracic,  and  lumbar  regions,  and  also  to 
draw  it  somewhat  to  one  side.  They  may  likewise  have  some  action  in  drawing 
down  the  ribs,  assisting  in  forced  expiration. 

3.    Longissimus  (Fig.  520). 

Attachments. — The  longissimus  represents  the  upward  prolongation  of  that 
portion  of  the  sacro-spinalis  which  arises  from  the  dorso-lumbar  fascia  and  the 
lumbar  vertebrae.  It  is  continued  upward  immediately  medial  to  the  ilio-costalis  to 
be  inserted  into  the  mastoid  process  of  the  temporal  bone,  but,  like  the  ilio-costalis, 
it  receives  in  its  course  accessory  bundles  and  also  gives  off  bundles  which  are 
inserted  into  the  skeletal  parts  over  which  it  passes. 

The  fibres  which  represent  the  direct  continuation  of  the  sacro-spinalis  are  con- 
tinued as  far  upward  as  the  first  thoracic  vertebra,  and  are  reinforced  by  short  acces- 
sory bundles  from  the  transverse  processes  of  the  lower  six  thoracic  vertebrae  to  form 
what  is  termed  the  longissimus  dorsi.  The  fibres  of  this  portion  of  the  muscle  are 
inserted  along  two  lines,  the  medial  of  which  passes  along  the  accessory  processes  of 
the  lumbar  vertebrae  and  the  transverse  processes  of  all  the  thoracic  vertebrae,  while 
the  lateral  line  passes  along  the  transverse  processes  of  the  lumbar  vertebrae  and  the 
angles  of  the  ribs  as  far  forward  as  the  second.  From  the  transverse  processes  of 
the  upper  six  thoracic  vertebra;  bundles  arise  which  unite  to  form  the  longissimus 
cervicis  or  transversalis  cervicis,  which  continues  the  line  of  the  longissimus  to  an 
insertion  into  the  posterior  tubercles  of  the  transverse  processes  of  the  second  to 
the  sixth  cervical  vertebra;  ;  and,  finally,  the  longissimus  capitis  or  trachelo-mastoid 
is  formed  by  bundles  arising  from  the  transverse  processes  of  the  three  upper 
thoracic  vertebras  and  the  articular  processes  of  the  three  lower  cervical,  and  passes 
upward  to  be  inserted  into  the  mastoid  process  of  the  temporal  bone. 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
third  cervical  to  the  second  sacral. 

Action. — The  thoracic  and  cervical  portions  of  the  longissimus  will  draw  the 
spinal  column  backward  and  to  one  side  ;  the  longissimus  capitis  will  have  a  similar 
action  on  the  head. 

4.    Splenitis  (Fig.  520). 

Attachments. — The  splenius  forms  a  flat  muscle  which  arises  from  the  spinous 
processes  of  the  upper  four  or  six  thoracic  and  the  seventh  cervical  vertebras  and 
from  the  lower  half  of  the  ligamentum  nuchas.  It  passes  upward  and  slightly 
laterally  and  divides  into  two  portions,  the  lower  of  which,  curving  around  the  outer 
edge  of  the  upper  portion,  passes  to  an  insertion  in  the  posterior  tubercles  of  the 
upper  three  cervical  vertebras,  forming  the  splenius  cervicis.  The  upper  portion, 
which  is  termed  the  splenius  capitis,  continues  upward,  and  is  inserted,  by  a  short 
tendon  into  the  posterior  border  of  the  mastoid  process  of  the  temporal  bone  and 
into  the  outer  part  of  the  superior  nuchal  line. 

Nerve-Supply. — From  the  posterior  divisions  of  the  second  to  the  eighth  cer- 
vical nerves. 

Action. — The  splenius  cervicis  will  draw  the  upper  cervical  vertebras  backward 
and  will  rotate  the  atlas  towards  the  side  of  the  muscle  in  action.      The  action  of 


THE   TRUNK    MUSCLES.  5" 

the  splenitis  capitis  upon  the  head  will  be  similar  ;  the  simultaneous  action  of  the  two 
muscles  of  opposite  sides  will  bend  the  head  backward,  each  muscle  neutralizing  the 
rotatory  effect  of  the  other. 

(6)    THE  TRANSVERSO-SPINAL  TRACT. 

i.  Spinalis.  6.  Intertransversales. 

2.  Semispinalis.  7-  Rectus  capitis  posticus  major. 

3.  Multifidus.  8.  Rectus  capitis  posticus  minor. 

4.  Rotatores.  9.  Obliquus  capitis  superior. 

5.  Interspinals.  10.  Obliquus  capitis  inferior. 

1.    Spinalis  (Fig.  520). 

Attachments. — The  spinalis  in  its  lower  portion  is  the  continuation  of  the 
deeper  and  innermost  fibres  of  the  sacro-spinalis,  and,  like  the  longissimus,  with 
which  it  is  partly  associated,  it  is  regarded  as  consisting  of  a  thoracic,  a  cervical, 
and  a  cranial  portion.  The  spinalis  dorsi  arises  from  the  spinous  processes  of  the 
upper  two  lumbar  and  the  lower  two  or  three  thoracic  vertebras  by  tendons  common 
to  it  and  the  longissimus  dorsi.  It  forms  a  thin,  flat  muscle  which  passes  upward, 
inserting  as  it  goes  into  the  spinous  processes  of  the  thoracic  vertebrae  from  the 
second  to  the  eighth  or  ninth,  but  one  vertebra  intervening  between  its  uppermost 
tendon  of  origin  and  its  lowermost  tendon  of  insertion.  The  spinalis  cervicis  arises 
from  the  spinous  processes  of  the  upper  two  or  four  thoracic  and  the  lower  two 
cervical  vertebrae,  and  ascends  alongside  the  spinous  processes  of  the  cervical  ver- 
tebrae to  be  inserted  into  those  of  the  second,  third,  and  fourth  vertebras.  The 
spinalis  capitis  consists  of  bundles  arisi?ig  from  the  spinous  processes  of  the  upper 
thoracic  and  last  cervical  vertebrse,  and  passes  upward  to  be  inserted  with  the  semi- 
spinalis capitis. 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
third  cervical  to  the  last  thoracic. 

Action. — To  extend  the  spinal  column. 

2.    Semispinalis    (Fig.  520). 

Attachments. — The  semispinalis  forms  the  superficial  layer  of  the  muscles 
lying  in  the  groove  between  the  spinous  and  transverse  processes  of  the  vertebras. 
Three  portions  may  be  recognized  in  it.  The  semispinalis  dorsi  arises  from  the  trans- 
verse processes  of  the  lower  six  or  seven  thoracic  vertebras  ;  its  fibres  are  directed 
obliquely  upward  and  medially  and  are  inserted  into  the  spinous  processes  of  the  five  or 
six  upper  thoracic  and  last  two  cervical  vertebras.  The  semispinalis  cervicis  arises 
from  the  transverse  processes  of  the  five  or  six  upper  thoracic  vertebras  and  is  inserted 
into  the  spinous  processes  of  the  second,  third,  fourth,  fifth,  and  sometimes  the  sixth 
cervical  vertebras.  This  portion  of  the  muscle  is  almost  concealed  beneath  the  upper- 
most portion,  the  semispinalis  capitis,  which  arises  from  the  transverse  processes  of  the 
upper  six  thoracic  vertebras  and  the  articular  and  transverse  processes  of  the  lower 
three  or  four  cervical  vertebras.  The  fibres  are  directed  almost  vertically  upward, 
and  are  joined  by  the  spinalis  capitis  to  form  a  broad  muscle-sheet  which  is  inserted 
into  the  under  surface  of  the  squamous  portion  of  the  occipital  bone  between  the 
superior  and  inferior  nuchal  lines. 

An  intermediate  tendinous  intersection  usually  divides  the  semispinalis  capitis 
into  an  upper  and  a  lower  portion,  and  is  much  more  distinct  in  the  more  medial 
bundles  than  in  the  lateral  ones.  Frequently  these  more  medial  bundles  are  sep- 
arated somewhat  from  the  others,  and  they  have  been  considered  a  distinct  muscle 
and  termed  the  biventer,  the  lateral  portion  of  the  muscle  being  named  the  complexus. 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
second  cervical  to  the  last  thoracic. 

Action. — The  semispinalis  dorsi  and  cervicis  extend  the  vertebral  column  and 
rotate  it  somewhat  towards  the  opposite  side.  The  semispinalis  capitis  draws  the 
head  backward  and  also  rotates  it  slightly  towards  the  opposite  side. 


512 


HUMAN    ANATOMY, 


3.    Multifidus  (Figs.  520,  521). 

Attachments. — The  multifidus  {multifidus  sfiznts)  constitutes  the  middle  layer 
of  the  muscles  occupying  the  groove  between  the  transverse  and  spinous  processes 


Fig.  521. 


Levatores  costarum 


Levatores  costarum 


Deep  muscles  of  back. 


of  the  vertebrae,  and  is  covered,  in  the  thoracic  and  cervical  regions,  by  the  semi- 
spinalis.     It  takes  its  origin  from  the  dorsal  surface  of  the  sacrum  and  from  the  trans- 


THE   TRUNK   MUSCLES.  513 

verse  or  articulating  processes  of  all  the  vertebrae  as  far  up  as  the  fourth  cervical. 
The  fibres  from  each  vertebra  pass  over  from  two  to  four  of  the  succeeding  vertebrae 
and  are  inserted  into  the  spinous  processes  of  the  third  to  the  fifth,  the  entire  insertion 
of  the  muscle  extending  from  the  spinous  process  of  the  last  lumbar  vertebra  to  that 
of  the  axis. 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
third  cervical  to  the  last  lumbar. 

Action. — To  bend  the  spinal  column  backward  and  rotate  it  towards  the  op- 
posite side. 

4.    Rotatores  (Fig.  521). 

Attachments. — The  rotatores  {rotatores  dorsi)  form  the  deepest  layer  of  the 
muscles  occupying  the  spino-transverse  groove.  They  form  a  series  of  small  muscles 
hardly  distinguishable  from  the  bundles  of  the  multifidus,  beneath  which  they  lie. 
They  are  to  be  found  along  the  entire  length  of  the  spinal  column  from  the  sacrum  to 
the  axis,  arising  from  the  transverse  process  of  one  vertebra  and  passing,  some  of  the 
fibres  to  the  base  of  the  spinous  process  of  the  next  succeeding  vertebra  (rotato?-es 
breves)  and  the  rest  to  a  corresponding  point  of  the  second  vertebra  above  (rotatores 
longi) . 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
third  cervical  to  the  last  lumbar. 

Action. — To  bend  the  spinal  column  backward  and  rotate  it  towards  the  op- 
posite side. 

5.   Interspinales  (Fig.  521). 

Attachments. — The  interspinales  are  relatively  small  muscles  which  pass  be- 
tween the  spinous  processes  of  succeeding  vertebrae.  They  are  usually  absent 
throughout  the  greater  portion  of  the  thoracic  region,  occurring  only  in  connection 
with  the  first  and  the  last  two  spines,  but  they  are  exceptionally  well  developed  in 
the  lumbar  region  and  are  usually  paired  in  the  cervical  region,  where  they  stop  at 
the  axis. 

Nerve-Supply. — From  the  posterior  divisions  of  the  spinal  nerves  from  the 
third  cervical  to  the  fifth  lumbar. 

Action. — Acting  together  to  bend  the  cervical  and  lumbar  portions  of  the  spinal 
column  backward. 

6.    Intertransversales  (Fig.  521). 

Attachments. — The  name  intertransversales  (mm.  intertransversarii)  has  been 
applied  to  a  series  of  small  muscles  occurring  in  the  cervical  and  lumbar  regions  and 
extending  between  the  transverse  or  mammillary  processes  of  successive  vertebrae. 
In  each  of  the  regions  named  two  sets  of  intertransversales  are  recognized,  but  it 
seems  probable  that  only  one  of  the  sets  in  such  region  belongs  to  the  dorsal  group 
of  muscles.  This  set  will  alone  be  considered  here,  the  other  (anterior)  one  being 
described  with  the  ventral  muscles  of  the  regions  in  which  it  occurs. 

The  intertransversarii  posteriores  occur  only  in  the  cervical  region  and  extend 
between  the  posterior  tubercles  of  the  transverse  processes  of  succeeding  vertebrae. 
The  intertransversarii  mediales  occur  only  in  the  lumbar  region  and  extend  between 
the  mammillary  processes  of  successive  vertebrae. 

Nerve-Supply. — Probably  by  fibres  belonging  to  the  posterior  divisions  of  the 
cervical  and  lumbar  nerves,  but  it  is  at  present  insufficiently  determined. 

Action. — To  bend  the  cervical  and  lumbar  portions  of  the  vertebral  column 
laterally. 

7.    Rectus  Capitis  Posticus  Major  (Fig.  522). 

Attachments. — The  greater  straight  muscle  (m.  rectus  capitis  posterior  major) 
arises  from  the  apex  of  the  spinous  process  of  the  axis  and  passes  upward  and  out- 
ward, broadening  as  it  goes,  to  be  inserted  into  the  middle  portion  of  the  inferior 
nuchal  line. 

33 


5  H 


HUMAN    ANATOMY. 


Nerve-Supply. — By  a  branch  from  the  posterior  division  of  the  suboccipital 
nerve. 

Action. — To  draw  the  head  backward  and  to  rotate  it  towards  the  same  side. 

8.    Rectus  Capitis  Posticus  Minor   (Fig.  522). 

Attachments. — The  lesser  straight  muscle  (m.  rectus  capitis  posterior  minor) 
arises  from  the  posterior  tubercle  of  the  atlas  and  passes  upward,  broadening  as  it 
goes,  to  be  inserted  into  the  inner  portion  of  the  inferior  nuchal  line. 

Nerve-Supply. — By  a  branch  from  the  posterior  division  of  the  suboccipital 
nerve. 

Action. — To  draw  the  head  backward. 

Fig.  522. 


Rectus  capitis  posti 
minor 
Rectus  capitis  posticu: 
major 

Obliquus  superio; 
Suboccipital  triangle- 

Obliquus  inferior 


Supraspinous  ligament 


Posterior  tubercle  of  atlas 
Transverse  process  of  atlas 


Deep  dissection  of  neck,  showing  suboccipital  group  of  muscles. 

9.    Obliquus  Capitis  Superior  (Fig.  522). 

Attachments. — The  superior  oblique  muscle  of  the  head  arises  irom  the  trans- 
verse process  of  the  atlas  and  passes  upward  to  be  inserted  into  the  squamous  portion 
of  the  occipital  immediately  above  the  outer  part  of  the  inferior  nuchal  line. 

Nerve-Supply. — By  a  branch  from  the  posterior  division  of  the  suboccipital 
nerve. 

Action. — To  draw  the  head  backward  and  slightly  laterally. 


10.    Obliquus  Capitis  Inferior  (Fig.  522). 

Attachments. — The  inferior  oblique  muscle  of  the  head  arises  from  the  tip  of 
the  spinous  process  of  the  axis  and  is  directed  outward  and  upward  to  be  inserted  into 
the  transverse  process  of  the  atlas. 

Nerve-Supply. — By  a  branch  from  the  posterior  division  of  the  suboccipital 
nerve. 

Action. — To  rotate  the  axis  towards  the  same  side. 


THE   VENTRAL    MUSCLES.  515 

The  Sacro-Coccygeus  Posterior. — The  reduction  of  the  caudal  vertebrae  in  man,  indicated 
by  the  condition  of  the  coccygeal  vertebrae,  has  brought  about  a  reduction  of  the  terminal 
portion  of  the  dorsal  axial  musculature,  it  being,  as  a  rule,  represented  only  by  the  ligaments 
upon  the  dorsal  surface  of  the  coccyx.  Quite  frequently,  however,  muscular  fibres  occur  inter- 
mingled with  the  connective  tissue,  and  occasionally  a  distinct  muscle,  the  sacro-coccygeus 
posterior,  may  be  found,  extending  from  the  last  sacral  vertebra  or  even  from  the  greater  sacro- 
sciatic  ligament  to  the  coccyx. 

THE    VENTRAL    MUSCLES. 

The  ventral  trunk  musculature  includes  all  those  axial  muscles  which  are  supplied 
from  the  anterior  divisions  (ventral  rami)  of  the  spinal  nerves.  As  already  indicated 
(page  473),  it  is  divisible  into  three  subgroups  :  a  group  of  more  median  muscles,  char- 
acterized by  their  fibres  retaining  more  or  less  perfectly  a  longitudinal  direction  and 
constituting  the  rectus  group ;  a  more  lateral  group,  in  which  the  fibres  possess  a 
distinctly  oblique  or  transverse  direction,  and  may  consequently  be  termed  the 
obliquus  group  ;  and,  finally,  a  hyposkeletal gi'oup,  whose  fibres  have  a  longitudinal 
direction,  and  which  is  situated  anterior  or  ventral  to  the  spinal  column. 

Instead  of  considering  the  various  muscles  belonging  to  each  of  these  groups  in 
succession,  it  seems  more  convenient  to  combine  a  topographic  classification  with 
the  morphological  one,  and  to  describe  the  various  groups  as  they  occur  in  the  neck, 
thoracic,  abdominal,  and  perineal  regions.  It  must  be  understood,  however,  that 
the  delimitations  of  these  regions  are  somewhat  arbitrarily  chosen,  and  that  there  is, 
so  far  as  the  muscles  are  concerned,  a  considerable  amount  of  overlapping  of  certain 
regions,  portions  of  myotomes  which  strictly  belong  to  the  thoracic  region,  for 
instance,  being  found  within  the  limits  of  what  is  recognized  as  the  abdominal  region. 
In  many  cases  these  overlapping  myotomes  have  united  with  myotomes  of  the  lower 
region  to  form  a  continuous  muscle,  and  it  is  consequently  impossible  to  refer  them  to 
their  proper  topographic  position  without  doing  violence  to  the  individuality  of  the 
muscles  which  they  help  to  form  ;  but  when  they  remain  practically  distinct  from  the 
muscles  of  their  adopted  region,  they  will  be  referred  to  the  region  from  which  they 
have  come. 

It  will  be  convenient  to  consider  first  the  muscles  of  the  abdominal  region,  there- 
after taking  up  in  succession  those  of  the  thoracic  and  cervical  regions,  those  of  the 
perineal  region  being  left  until  the  last. 

THE    ABDOMINAL    MUSCLES. 

The  Superficial  Fascia  of  the  Abdomen. — The  superficial  fascia  of  the 
abdomen  is  usually  described  as  consisting  of  two  layers.  These,  however,  are  well 
marked  only  over  the  anterior  and  especially  the  lower  part  of  the  abdominal  wall, 
losing  their  distinctness  laterally  and  above,  where  they  pass  over  into  the  superficial 
fascias  of  the  back  and  thorax.  The  superficial  layer  {Camper  s fascia)  usually  con- 
tains a  considerable  amount  of  fat,  except  at  the  umbilicus,  and  may  occasionally 
reach  a  great  thickness  owing  to  the  development  of  that  tissue.  The  deeper  layer 
immediately  underlies  the  fatty  layer,  and  is  a  connective-tissue  membrane  of  vary- 
ing density,  containing  a  considerable  amount  of  yellow  elastic  tissue.  It  is  con- 
nected to  the  deep  abdominal  fascia  which  covers  the  muscles  of  the  abdominal  wall 
by  loose  areolar  tissue,  except  along  the  median  line,  where  it  is  firmly  adherent 
along  the  linea  alba  and  around  the  umbilicus.  A  short  distance  above  the  sym- 
physis pubis  it  gives  off  a  band  which  is  largely  composed  of  elastic  tissue  and  is 
inserted  below  into  the  fascia  of  the  penis,  forming  the  suspensory  ligament  of  that 
organ  (Fig.  528). 

In  the  inguinal  region  the  deep  layer  of  the  superficial  fascia  is  especially  well 
defined,  forming  what  has  been  termed  the  fascia  of  Scarpa.  Laterally  it  passes 
down  over  Poupart's  ligament  to  unite  with  the  fascia  lata  of  the  thigh,  the  super- 
ficial vessels  and  lymph-nodes  of  this  region  lying  between  it  and  the  superficial 
layer.  More  medially  it  is  continued  down  over  the  spermatic  cord,  becoming  con- 
tinuous below  partly  with  the  deep  layer  of  the  superficial  fascia  of  the  perineum 
{fascia  of  Colles)  and  partly,  after  fusing  with  the  superficial  layer,  which  loses  its 
fat,  with  the  dartos  of  the  scrotum. 


5i6 


HUMAN    ANATOMY. 


(a)  THE   RECTUS   MUSCLES. 
I.    Rectus  abdominis.  2.    Pyramidalis. 


1.   Rectus  Abdominis  (Fig.  523). 

Attachments. — The  rectus  abdominis  forms  a  flat  but  strong  muscle  which 
traverses  the  entire  length  of  the  ventral  abdominal  wall  immediately  lateral  to  the 
linea  alba.  It  arises  from  the  anterior  surface  of  the  xiphoid  process  of  the  sternum 
and  from  the  cartilages  of  the  fifth,  sixth,  and  seventh  ribs,  and  is  inserted  by  a  strong 
tendon  into  the  crest  and  symphysis  of  the  pubis. 

Fig.- 523. 


Pectoralis  major- 


Tendon  of  rectus 


Rectus,  cut  and  turned 


Posterior  sheath  of  rectus 
External  oblique 

Semilunar  fold 

Transversalis  fascia 

Deep  epigastric  artery 

Rectus,  stump. 


Saphe 


Sheath  of  rectus,  turned  < 


Tendinous  intersection 


Crest  of  ilium 


Anterior  superior  iliac 


,-ramidalis 
External 
abdominal  ring 
Cribriform  fascia 
closing  saphenous 
i         opening 
I .Spermatic  cord 


Muscles  of  anterior  abd 


The  fibres  are  directed  longitudinally,  and  are  interrupted  along  three  and 
occasionally  four  transverse  lines  by  tendinous  intersections  of  the  muscle.  One  of 
these  inscriptiones  tendinetz  occurs  about  the  level  of  the  umbilicus,  another,  often 
affecting  only  the  medial  portion  of  the  muscle,  corresponds  approximately  to  the 
lower  margin  of  the  thorax,  and  the  third  lies  about  midway  between  the  two.  The 
fourth,  when  present,  frequently  is  limited  to  the  lateral  portion  of  the  muscle,  and 
occurs  about  midway  between  the  level  of  the  umbilicus  and  the  crest  of  the  pubis. 


THE   VENTRAL    MUSCLES.  517 

Nerve-Supply. — From  the  anterior  divisions  of  the  thoracic  nerves  from  the 
fifth  to  the  twelfth. 

Action. — The  recti  act  as  flexors  of  the  thorax  upon  the  pelvis  or,  acting  from 
above,  they  flex  the  pelvis  on  the  thorax.  They  also  aid  in  the  compression  of  the 
abdominal  viscera  in  defecation  and  parturition  and  in  strong  expiratory  efforts. 

Variations. — The  origin  of  the  rectus  sometimes  ascends  to  the  fourth  or  third  rib  or  even 
higher.  The  tendinous  inscriptions  are  probably  the  persistent  representatives  of  the  connective- 
tissue  partitions  between  certain  of  the  myotomes  of  which  the  muscle  is  composed.  They  are 
subject  to  a  certain  amount  of  variation  in  number,  five  or  six  occasionally  occurring,  while,  on 
the  other  hand,  they  may  be  reduced  to  two. 

2.   Pyramidalis  (Fig.  523). 

Attachments. — The  pyramidalis  is  a  somewhat  variable  muscle  which  arises 
below  from  the  upper  surface  of  the  body  of  the  pubis  and  from  the  symphysis  and  is 
inserted  above  into  the  linea  alba,  somewhere  between  the  umbilicus  and  the  sym- 
physis. 

Nerve-Supply. — From  the  anterior  divisions  of  the  eleventh  and  twelfth 
thoracic  nerves. 

Action. — To  tense  the  linea  alba. 

Variations. — The  extent  to  which  the  muscle  is  developed  varies  greatly,  its  insertion  some- 
times extending  well  up  towards  the  umbilicus,  while,  on  the  other  hand,  it  is  not  infrequently 
absent.     This  latter  condition  has  been  estimated  to  occur  in  over  16  per  cent,  of  cases. 

(b)  THE  OBLIQUUS   MUSCLES. 

1.  Obliquus  externus.  4.   Transversalis. 

2.  Obliquus  internus.  5.    Ouadratus  lumborum. 

3.  Cremaster.  6.    Intertransversales  laterales. 

1.  Obliquus  Externus  (Fig.  524). 

Attachments. — The  external  oblique  forms  a  muscular  sheet  in  the  lateral 
portions  of  the  anterior  abdominal  wall.  It  arises  by  seven  or  eight  fleshy  digitations 
from  the  corresponding  number  of  lower  ribs,  the  upper  digitations  alternating  with 
digitations  of  the  serratus  magnus,  while  the  lower  three  alternate  with  those  of  the 
latissimus  dorsi.  The  fibres  from  the  lowest  ribs  pass  vertically  downward  to  be  in- 
serted into  the  crest  of  the  ilium  ;  the  remainder  are  directed  mainly  downward  and 
forward  and,  above,  directly  forward  to  join  a  broad  aponeurotic  sheet  which  con- 
tributes to  the  formation  of  the  ventral  abdominal  aponeurosis. 

Nerve-Supply. — From  the  anterior  divisions  of  the  eighth  to  the  twelfth 
thoracic  nerves  and  from  the  ilio-hypogastric  and  ilio-inguinal  nerves. 

Action. — Since  the  external  oblique  is  a  curved  sheet  which  passes  from  the 
lateral  portions  of  the  abdominal  wall  towards  the  mid-ventral  line,  contraction  of  its 
fibres  will  tend  to  compress  the  abdominal  contents  and  so  assist  in  micturition,  defe- 
cation, parturition,  and  expiration,  its  action  in  the  last-named  process  being  increased 
by  the  power  which  it  possesses  of  drawing  the  lower  ribs  downward.  Furthermore, 
according  as  it  acts  from  below  or  above,  it  will  flex  the  thorax  and  spinal  column 
upon  the  pelvis  or  the  pelvis  upon  the  spinal  column,  at  the  same  time  producing  a 
slight  rotation  of  the  thorax  to  the  opposite  side  and  the  pelvis  to  the  same  side. 
When  the  two  muscles  of  opposite  sides  act  together,  the  rotatory  action  of  each  will 
be  neutralized.  By  the  most  lateral  fibres  a  lateral  flexion  of  the  thorax  or  pelvis 
will  be  produced. 

2.  Obliquus  Internus  (Fig.  525). 

Attachments. — The  internal  oblique  muscle  lies  immediately  beneath  the  ex- 
ternal one.  It  arises  from  the  outer  two-thirds  of  Poupart's  ligament,  from  the 
whole  length  of  the  middle  lip  of  the  crest  of  the  ilium,  and  from  the  lumbo-dorsal 
fascia.  From  this  extended  origin  its  fibres  spread  out  in  a  fan-shaped  manner,  the 
more  posterior  ones  passing  upward  and  slightly  forward  to  be  inserted  into  the 


5i8 


HUMAN   ANATOMY. 


lower  three  ribs,  while  of  the  rest  the  more  anterior  ones  pass  forward  and  upward, 
those  from  the  neighborhood  of  the  anterior  superior  iliac  spine  directly  forward,  and 
those  from  Poupart's  ligament  forward  and  downward,  all  joining  in  a  flat  aponeu- 
rosis which  unites  with  the  anterior  abdominal  aponeurosis  at  the  linea  semilunaris. 
In  its  lowermost  portion  the  aponeurosis  unites  with  that  of  the  transversalis  to  form 
what  is  termed  the  coiijoined  tendon,  and  by  this  it  is  attached  to  the  crest  of  the  pubis. 


Fig.  524. 


Serratus  magnus 


Line  of  subcostal  arch 


Linea  transversa 
lunaris 


Anterior  superior  iliac  spin 


Suspensory  ligament  of  penis 
Poupart's  ligament 


Dissection  of  lateral  body-wall,  showing  external  oblique  and  adjoining  muscles. 


Nerve-Supply. — From  the  anterior  divisions  of  the  eighth  to  the  twelfth 
thoracic  nerves  and  from  the  ilio-hypogastric  and  ilio-inguinal  nerves. 

Action. — The  internal  oblique  acts  very  similarly  to  the  external  in  compressing 
the  abdominal  contents,  in  drawing  the  lower  ribs  downward,  and  in  flexing  the 
thorax  or  pelvis  laterally.  It  will  also  flex  the  thorax  and  vertebral  column  upon  the 
pelvis  or  the  pelvis  upon  the  vertebral  column,  but  in  these  actions  the  accompanying 
rotation  will  be  in  a  direction  contrary  to  that  caused  by  the  external  oblique,  the 
thorax  being  rotated  to  the  same  side  and  the  pelvis  to  the  opposite  side.  It  may  be 
remarked  that  the  rotatory  action  of  the  external  oblique  of  the  one  side  and  the 
internal  oblique  of  the  other  will  be  in  the  same  direction. 

Variations. — The  internal  oblique  may  be  crossed  by  one  or  more  tendinous  intersections 
which  have  probably  the  same  significance  as  those  of  the  rectus  abdominis. 


THE   VENTRAL    MUSCLES. 
3.  Cremaster  (Figs.  525,  1671). 


5i9 


Attachments. — The  cremaster  muscle  consists  of  a  series  of  somewhat  scat- 
tered loops  of  muscle-tissue  derived  from  the  lower  part  of  the  internal  oblique  and 
to  a  slight  extent  from  the  transversalis.  It  is  attached  laterally  to  Poupart's  liga- 
ment and  medially  to  the  anterior  layer  of  the  sheath  of  the  rectus.  The  loops  de- 
scend through  the  inguinal  canal  along  with  the  spermatic  cord,  the  muscle  being 

Fig.  525. 


Pectoralis  majo 


Serratus  magnus 


Latissimus  dorsi 


Edge  of  cut  external  oblique 


Posterior  aponeurosis  of  internal 
oblique 


Iliac  crest 
Fascia  lata. 


Cut  edge  of  fascia  lata 
Gluteus  maximus 


Edge  of  cut  aponeurosis  of 
external  oblique 


Internal  oblique 


Anterior  superior  iliac  spine 


Conjoined  tendo 


Suspensory  ligament 
Cremaster  fibres 


bowing  internal  obliqu 


well  developed  only  in  the  male,  and  spread  out  in  the  tunica  vaginalis  communis  of 
the  testis  and  spermatic  cord.  The  loops  are  united  by  connective  tissue  which  forms 
part  of  the  cremasteric  fascia. 

Nerve-Supply. — By  the  genital  branch  of  the  genito-crural  nerve. 

Action. — To  draw  the  testis  upward  towards  the  external  abdominal  ring. 

4.  Transversalis  (Fig.  526). 
Attachments.  —The  transversalis   (m.  transversus  abdominis)    is  the  deepest 
layer  of  muscle  on  the  lateral  abdominal  wall  and  immediately  underlies  the  internal 
oblique.      It  arises  from  the  cartilages  of  the  lower  six  ribs,  from  the  lumbo-dorsal 


520 


HUMAN   ANATOMY. 


fascia,  the  inner  lip  of  the  crest  of  the  ilium,  and  the  outer  two-thirds  of  Poupart's 
ligament.  Its  fibres  pass  horizontally  inward  to  join  the  ventral  abdominal  aponeu- 
rosis along  the  linea  semilunaris  ;  the  lower  ones,  however,  bending  somewhat  down- 
ward, pass  into  an  aponeurosis  which  unites  with  that  of  the  internal  oblique  to  form 
the  conjoined  tendon  attached  to  the  crest  of  the  pubis. 

Nerve-Supply. — From  the  anterior  divisions  of  the  seventh  to  the  twelfth 
thoracic  nerves  and  from  the  ilio-hypogastric  and  ilio-inguinal  nerves. 

Action. — To  compress  the  contents  of  the  abdomen. 

Fig.  526. 


Serratus  magnus 


Latissimus  dorsi 


Edge  of  cut  external  oblique 


Edge  of  cut  internal  oblique 
.     Lumbo-dorsal  fascia 


Fascia  lata 

Cut  edge  of  fascia  lata  -    ^ 

Gluteus  maximus 

Tensor  fascia?  lata? 


—  Pectoralis  major 


Edge  of  aponeurosis  of  external 
oblique 


Edge  of  aponeurosis  of  internal 
oblique 


Aponeurosis  of  transversalis 
Rectus,  covered  by  sheath 


Conjoined  tendon 


C remaster  fibres 


Dissection  of  lateral  body-wall,  showing  tran 


The  fascia  transversalis  is  a  thin  layer  of  connective  tissue  which  lines  the 
inner  (deeper)  surface  of  the  transversalis  muscle.  Posteriorly  it  is  continuous  with 
the  strong  aponeurotic  band  formed  by  the  fusion  of  the  superficial  and  deep  layers  of 
the  lumbo-dorsal  fascia,  anteriorly  it  combines  with  the  deeper  layer  of  the  ventral 
abdominal  aponeurosis  to  form  the  posterior  layer  of  the  sheath  of  the  rectus  muscle, 
and  above  it  unites  with  the  fascia  covering  the  lower  surface  of  the  diaphragm. 
Below  its  lateral  portion  is  attached  to  the  crest  of  the  ilium  and  the  outer  part  of 
Poupart's  ligament  where  it  becomes  continuous  with  the  iliac  fascia,  but  more  medially 
it  is  continued  downward  beneath  Poupart's  ligament  to  form  the  anterior  wall  of  the 
sheath  of  the  femoral  vessels,  the  portion  of  it  immediately  above  the  vessels  being 


THE   VENTRAL   MUSCLES. 


thickened  somewhat  to  form  the  deep  crural  arch  (Fig.  1496).  More  medially  still  it 
is  attached  to  the  free  edge  of  Gimbernat's  ligament  and  to  the  upper  surface  of  the 
superior  ramus  and  body  of  the  pubis. 

A  little  over  1  cm.  above  Poupart's  ligament,  and  about  half-way  between  the 
anterior  superior  iliac  spine  and  the  symphysis  pubis,  the  transversalis  fascia  is  per- 
forated by  the  spermatic  cord  in  the  male  and  by  the  ligamentum  teres  of  the  uterus  in 
the  female.  The  fascia  is  continued  downward  and  forward  over  the  cord  or  ligament 
to  form  a  somewhat  funnel-like  investment  for  it  termed  the  infundibuliform  fascia,  the 
inner  margin  of  the  funnel  marking  the  position  of  the  internal  abdominal  ring. 

5.     QUADRATUS    LUMBORUM  (Fig.    527). 

Attachments. — The  quadratus  lumborum  is  a  flat  quadrilateral  muscle  which 
lies  towards  the  back  part  of  the  ab- 
dominal wall,  extending  between  the  Fig.  527. 
crest  of  the  ilium  and  the  lower  bor- 
der of  the  twelfth  rib.  It  consists  of 
two  layers  of  fibres  which  frequently 
are  distinguishable  from  each  other 
only  with  difficulty.  The  anterior 
layer,  which  arises  from  the  trans- 
verse processes  of  the  lower  four  lum- 
bar vertebrae  and  from  the  posterior 
part  of  the  iliac  crest,  is  inserted  into 
the  lower  border  of  the  twelfth  rib  ; 
the  posterior  layer  (Fig.  527)  arises 
from  the  crest  of  the  ilium  and  is  in- 
serted into  the  lower  border  of  the 
twelfth  rib  and  into  the  transverse 
processes  of  the  upper  four  lumbar 
vertebrae. 

Nerve-Supply. — By     branches 
from  the  lumbar  plexus. 

Action. — To  draw  downward  the 
last  rib  and  to  bend  the  lumbar  por-        \vMk 
tion  of  the  spinal  column  laterally.  j " 

Relations. — The  quadratus  lum-       /    a^l 
borum    rests    behind   upon    the   deep       \  *  'W 
layer  of  the  fascia  lumbo-dorsalis  (Fig. 
519),  which  separates  it  from  the  spino- 
sacral  muscle.      Its  anterior  surface  is 
in  relation  to  the  kidney  and  the  as-     Quadratus  lumbon 
cending  or  descending  colon,  is  crossed 
by  the  lumbar  arteries,  and  is  covered  towards  its  inner  margin  by  the  psoas  major. 

6.   Intertransversales  Laterales  (Fig.  521). 

Attachments. — The  lateral  intertransversales  are  a  series  of  small  quadrilateral 
muscles  which  extend  between  successive  transverse  processes  of  the  lumbar  vertebrae. 

Nerve-Supply. — Probably  from  the  anterior  rami  of  the  lumbar  nerves. 

Action. — To  bend  laterally  the  lumbar  portion  of  the  spinal  column. 

The  Ventral  Abdominal  Aponeurosis  (Fig.  528). — The  broad  aponeurotic 
sheets  into  which  the  oblique  and  transverse  muscles  of  the  abdomen  are  continued 
at  their  anterior  (medial). edges  unite  more  or  less  intimately  with  one  another  and 
with  the  fascia  transversalis  to  form  the  ventral  abdominal  aponeurosis.  Laterally  the 
various  layers  of  which  this  aponeurosis  is  composed  are  to  a  certain  extent  discerni- 
ble, since  the  lines  along  which  the  fibres  of  the  three  muscles  pass  into  the  apo- 
neurosis do  not  coincide,  that  of  the  external  oblique  extending  from  the  outer  border 
of  the  rectus  muscle  above  obliquely  downward  and  laterally  to  the  anterior  superior 
spine  of  the  ilium,  while  those  of  the  internal  oblique  and  transversus  follow  essen- 


nuscle  of  right  side,  seen  from  behind. 


522 


HUMAN   ANATOMY. 


tially  the  outer  border  of  the  rectus,  except  below,  where  they  lie  a  little  lateral  to 
that  muscle.  More  medially,  however,  the  layers  become  intimately  associated  and 
can  only  be  separated  artificially. 

At  the  outer  border  of  the  rectus  muscle  the  aponeurosis  divides  into  two  layers 
(Fig.  529,  A)  which  pass  one  in  front  and  the  other  behind  the  rectus,  thus  forming  a 
sheath  for  it  (vagina  musculi  recti).  The  line  of  the  division  is  indicated  on  the  surface 
of  the  abdomen  by  a  slight  groove,  and  constitutes  what  is  termed  the  linea  semi- 
lunaris. When  they  reach  the  mesial  border  of  the  rectus  the  two  layers  unite  and 
become  continuous  in  the  middle  line  with  the  aponeurosis  of  the  opposite  side  to 
form  a  strong  fibrous  band  which  extends  from  the  front  of  the  xiphoid  process  of  the 

sternum  above  to  the 
Fig.  528.  symphysis   pubis   be- 

low, and  is  termed  the 
li?iea  alba.  In  its 
upper  part  this  band 
is  fairly  broad,  but 
below  the  umbilicus, 
which  is  situated  in 
the  band,  it  suddenly 
narrows  to  a  thin  line 
which  becomes  con- 
tinuous below  with  the 
superior  pubic  liga- 
ment, behind  the  in- 
sertion of  the  recti,  by 
a  triangular  expansion 
which  occasionally 
contains  muscle-fibres 
and  is  termed  the  ad- 
miniculum  lineae  albae. 
The  posterior  layer 
of  the  aponeurosis, 
which  forms  the  poste- 
rior wall  of  the  sheath 
of  the  rectus,  is  fairly 
thick  above,  but  a  lit- 
tle below  the  level  of 
the  umbilicus  it  sud- 
denly becomes  very 
much  thinner  along  an 
arched  line,  the  con- 
cavity of  which  is  downward,  and  may  sometimes  be  represented  by  a  distinct  fold. 
This  margin  is  termed  the  line  ox  fold  of  Douglas  (linea  semicircularis )  (Fig.  523). 


--    — Lii 


ransversrt' 


Hi  oblique 


m 


Anterior  superio 
iliac  spine 
Intercnlmnna 


External  abdomi- 
nal ring 

Spermatic  cord_ 


\ 


Suspensory 

\         ligament 
\        of  penis 


Superficial  dissection  of  abdo 


showing  ventral  aponeurosis. 


Various  suggestions  have  been  made  in  explanation  of  this  sudden  change  in  the  thickness 
of  the  posterior  layer  of  the  sheath  of  the  rectus.  It  has  been  supposed  that  it  was  connected 
with  the  passage  of  the  inferior  epigastric  artery  into  the  substance  of  the  muscle  (Henle),  a 
somewhat  inadequate  cause  even  if  the  point  of  passage  of  the  artery  through  the  sheath  cor- 
responded with  the  semicircular  line.  The  thinness  of  the  portion  of  the  sheath  below  the  line 
has  been  explained  on  the  ground  that  it  represents  the  portion  with  which  the  urinary  bladder 
was  in  contact  in  foetal  life  (Gegenbaur),  and  also  by  the  view  that  the  strain  exerted  on  this 
portion  of  the  sheath  is  less  than  that  placed  upon  the  upper  part,  since  the  latter  is  acted  on 
by  fibres  of  the  oblique  and  transverse  muscles  which  have  bony  attachments  drawn  upward 
during  inspiration,  while  the  lower  part  is  in  relation  to  the  less  active  fibres  attached  to  the 
inguinal  ligament  (Solger). 

Finally,  it  may  be  stated  that  the  immediate  cause  for  the  sudden  change  in  thickness  has 
been  assigned  to  the  development  of  the  processus  vaginalis  peritonei,  the  pouch  of  peritoneum 
which  in  the  embryo  descends  into  the  genital  swelling  and  gives  rise  in  the  male  to  the  tunica 
vaginalis  testis.  The  formation  of  this  peritoneal  pouch  is  held  to  prevent  the  lower  portions 
of  the  posterior  layer  of  the  abdominal  aponeurosis  which  are  derived  from  the  aponeuroses  of 
the  internal  oblique  and  transversalis  from  passing  behind  the  rectus  muscle,  the  posterior  wall 
of  its  sheath  being  formed  only  by  the  fascia  transversalis  (Eisler). 


THE   VENTRAL    MUSCLES. 


523 


In  the  lower  part  of  the  anterior  abdominal  wall  the  lowermost  fibres  of  the 
abdominal  aponeurosis — those  extending  between  the  anterior  superior  spine  of  the 
ilium  and  the  pubic  spine — form  a  strong  ligamentous  band,  the  ligament  of  Pou- 
part  (ligamentum  inguinale)  (Figs.  524,  530),  the  outer  portion  of  which  gives  rise  to 
some  of  the  fibres  of  the  internal  oblique  and  transversalis  muscles,  while  the  fascia 
lata  of  the  thigh  is  attached  to  it  below.  Near  its  medial  end  some  of  its  fibres  pass 
inward  to  be  attached  to  the  ilio-pectineal  line  of  the  pubis,  forming  a  horizontal  trian- 
gular sheet  whose  free  concave  lateral  border  forms  the  medial  boundary  of  the  femo- 
ral ring  (annulus  femoralis)  through  which  the  femoral  hernias  make  their  exit  from 
the  pelvis.  This  reflection  (Fig.  531)  is  the  ligament  of  Gimbernat  (ligamentum 
lacunare).  Furthermore,  a  sheet  of  fibres,  variable  in  its  development  and  termed  the 
triangular  fascia  (ligamentum  inguinale  reflexum),  or  ligament  of  Colles  (Fig.  1485), 
is  reflected  upward  and  medially  from  the  inner  portions  of  Poupart's  and  Gimbernat' s 
ligaments  in  front  of  the  lower  medial  portions  of  the  aponeuroses  of  the  internal 
oblique  and  transversalis  muscles  to  the  anterior  layer  of  the  sheath  of  the  rectus. 

The  Inguinal  Canal. — At  an  early  stage  in  the  development  of  the  foetus  an 
outpouching  of  the  lower  part  of  the  abdominal  wall  occurs  on  each  side  to  form  the 
genital  swellings,  which  later  become  the  scrotum  in  the  male  and  the  labia  majora 

Fig.  529. 


Transversalis  fascia 


of  aponeurosis  of  internal  oblique 
Posterior  sheath     ,  — Rectus —  , 


External  oblique 

Internal  oblique 

Aponeurosis  of  internal  oblique 


Anterior  sheath  of  rectus 
Superficial  fascia 
Aponeurosis  of  external  oblique 


Transversalis  muscle 
Internal  oblique 


Superficial  fascia 

Skin-"-" '—/ 

Aponeurosis  of  external  oblique  Anterior  sheath  of  rectus 

Diagrams  showing  constitution  of  sheath  of  rectus  muscle.    A,  in  upper  three-fourths;  B,  in  lower  fourth. 

in  the  female.  The  points  at  which  the  outpouchings  occur  are  those  at  which  the 
lower  ends  of  a  ligament  descending  from  the  primitive  kidneys  (mesonephri)  are 
attached  to  the  abdominal  wall,  and  these  ligaments,  consequently,  are  carried  through 
the  length  of  the  outpouching  beneath  its  peritoneal  lining  to  attach  to  the  walls  of 
the  scrotum  or  the  labia.  In  the  female  the  ligaments  become  in  part  the  round 
ligaments  of  the  uterus,  but  in  the  male  the  relations  of  the  outpouchings  become 
more  complicated.  Owing  to  the  descent  into  them  of  the  testes  (page  2040),  the 
ligaments  are  drawn  completely  into  the  pouch,  forming  the  gubemacula  of  the  testes, 
while  the  vasa  deferentia  and  the  vessels  and  nerves  of  the  testes  are  also  carried 
into  the  pouch,  uniting  to  form  the  spermatic  cord.  There  are,  consequently,  pass- 
ing from  the  abdominal  cavity  into  each  pouch,  in  the  female  the  round  ligaments  of 
the  uterus  and  in  the  male  the  spermatic  cord. 

At  first,  and  in  the  male  for  a  considerable  time  after  birth,  the  communication  of 
the  pouch  with  the  abdominal  cavity  is  widely  open  ;  but  later,  in  the  upper  part  of  the 
pouch  in  the  male  and  throughout  its  entire  length  in  the  female,  the  lumen  becomes 
reduced,  and  finally  is  completely  obliterated  by  the  union  of  its  walls  to  the  sper- 
matic cord  or  the  round  ligament,  its  lower  portion  persisting  in  the  male  as  the  space 
which  exists  between  the  visceral  and  parietal  layers  of  the  tunica  vaginalis  testis. 


524 


HUMAN   ANATOMY. 


As  a  result  of  these  processes  the  lower  portion  of  the  abdominal  wall  is 
traversed  on  either  side  by  the  spermatic  cord  or  by  the  ligamentum  teres  of  the 
uterus,  and  it  is  customary  to  regard  the  space  occupied  by  the  one  or  the  other  of 
these  structures  as  a  canal,  which  is  termed  the  inguinal  canal.  It  should  be 
understood,  however,  that  an  actual  space  surrounding  the  cord  or  ligament  does 
not  exist,  the  walls  of  the  canal  being  united  to  the  structure  contained  within  it. 
Nevertheless,  the  union  is  by  no  means  a  strong  one,  the  region  of  the  abdominal 
wall  traversed  by  the  ligamentum  teres  or  especially  by  the  spermatic  cord  being 
relatively  weak  and  not  infrequently  the  seat  of  an  inguinal  hernia. 

The  inguinal  canal  is  somewhat  over  3  cm.  (i}4  in. )  in  length  and  is  situated 
immediately  above  Poupart's  ligament,  which  it  crosses  obliquely  from  above  down- 
ward, medially,  and  forward.  Its  upper  or  inner  end  is  about  midway  between  the 
anterior  superior  spine  of  the  ilium  and  the  spine  of  the  pubis,  and  lies  about  12  mm. 
()4  in. )  above  the  line  of  Poupart's  ligament.  It  is  marked  by  a  more  or  less  distinct 
depression  on  the  posterior  surface  of  the  abdominal  wall  surrounding  the  spermatic 
cord  or  round  ligament,  termed  the  internal  abdominal  ring  (annulus  inguinalis 

Fig.   530. 


Anterior  superior  iliac  spine 


Poupart's  ligament 

Falciform  process 
Iliac  portion  of  fascia  lata 

Saphenous  openi 

Femoral  artery 
Femoral  v 


neurosis  of  external  obliqu 


External  abdominal  ring 
External  pillar 
Internal  pillar 

Gimbernat's  ligament,  inner 
boundary  of  femoral  ring 


Pubic  portion  of  fascia  lata 
Spermatic  cord 


Internal  saphenous 


Dissection  of  right  inguinal  region,  showing  external  abdominal  ring  and  saphenous  opening. 


abdominis).  The  depression  (Fig.  532)  is  due  to  the  transversalis  fascia  being  pro- 
longed downward  over  the  spermatic  cord  as  a  funnel-like  sheath,  the  infundibuli- 
fiorm  fascia.  The  lower  or  medial  end  of  the  canal  corresponds  to  the  external 
abdominal  ring  (annulus  abdominalis  subcutaneus)  (Figs.  523,  530),  and  lies  just 
lateral  to  and  a  little  above  the  spine  of  the  pubis  and  is  surrounded  by  the  lower 
medial  portion  of  the  aponeurosis  of  the  external  oblique.  The  fibres  of  the  aponeu- 
rosis which  bound  this  ring  are  somewhat  thickened,  forming  what  are  termed  the 
pillars  (crura)  of  the  ring,  the  uppermost  of  which,  the  internal  pillar  (crus  superior), 
consists  of  fibres  passing  to  the  symphysis  pubis  ;  the  lower  one,  the  external  pillar 
(crus  inferior),  is  formed  by  the  fibres  passing  to  the  pubic  spine,  and  corresponds 
to  the  medial  end  of  Poupart's  ligament.  Stretching  across  between  the  two  crura 
are  numerous  obliquely  arching  intercolumnar  fibres  (librae  intercrurales)  which  extend 
laterally  almost  as  far  out  as  the  anterior  superior  spine  of  the  ilium.  From  the 
margins  of  the  external  ring  an  attenuated  prolongation  of  the  aponeurosis  of  the 
external  oblique  is  continued  downward  over  the  spermatic  cord  as  a  thin  membrane 
known  as  the  intercolumnar  or  external  spermatic  fiascia. 


THE   VENTRAL   MUSCLES. 


525 


Owing  to  the  oblique  direction  of  the  canal,  that  portion  of  the  aponeurosis  of 
the  external  oblique  which  is  strengthened  by  the  intercolumnar  fibres,  together  with 
a  portion  of  the  internal  oblique,  forms  its  anterior  wall,  while  its  posterior  wall  is 
formed  by  the  aponeurosis  of  the  transversalis,  together  with  the  more  medial  lower 
portion  of  that  of  the  internal  oblique,  these  two  layers  of  fascia  uniting  in  this  region 
to  form  what  is  termed  the  co7ijoined  tendon,  which  is  attached  below  to  the  body  and 
superior  ramus  of  the  pubis,  and  medially  is  especially  thickened  to  form  a  band,  the 
falx  inguinalis,  firmly  attached  along  its  medial  border  to  the  tendon  of  the  rectus. 
More  laterally,  where  it  forms  the  medial  boundary  of  the  internal  abdominal  ring,  it 
is  also  thickened  (Fig.  531),  forming  the  ligament  of  Hesselbach  (ligamentum  inter- 
foveolare).  Between  these  two  thickenings  the  abdominal  wall  is  weaker  (Fig.  1493) 
and  may  give  way  to  internal  pressure,  permitting  a  hernia,  which  comes  to  the  sur- 
face at  the  external  abdominal  ring  without  having  traversed  the  inguinal  canal,  and  is 
therefore  spoken  of  as  a  direct  hernia,  in  contradistinction  to  the  more  usual  oblique 
hernia  which  enters  the  canal  at  the  internal  abdominal  ring. 


Fig.  531. 


Deep  epigastric  artery 

Interfoveolar  or 

Hesselbach's  ligament 

Weak  area. 

Conjoined  tendon 

Muscular  fibre: 

er  end  of  Poupart's  ligatm 

Urach 
Bladd 


—  Poupart's  ligament 
Transversalis  muscle 

—  Spermatic  vessels 

—  External  iliac  artery 
^-External  iliac  vein 

—  Deep  epigastric  artery  (cut) 
— .  Vas  deferens 


Femoral  ring 
Gimbernat's  ligament 


Dissection  of  posterio 


urface  of  anterior  abdominal  wall,  showing  relations  of  conjoined  tendo 
to  internal  abdominal  ring. 


A  small  fasciculus  of  muscle-tissue  is  sometimes  found  close  to  the  medial  border  of  the 
internal  abdominal  ring.  It  is  the  m.  interfqveolaris  (Fig.  531),  and  arises  from  the  superior 
ramus  of  the  pubis,  passing  almost  directly  upward  to  spread  out  on  the  posterior  surface  of  the 
transversalis.     It  is  generally  regarded  as  an  aberrant  portion  of  the  transversalis  muscle. 


The  Posterior  Surface  of  the  Anterior  Abdominal  Wall. — Throughout 
its  entire  extent,  with  the  exception  of  a  small  area  in  the  median  line  below,  the 
posterior  surface  of  the  anterior  abdominal  wall  is  lined  by  peritoneum.  In  the 
exceptional  area  the  peritoneum  is  kept  from  actual  contact  with  the  wall  by  a 
band  of  fibrous  tissue,  the  urachus,  which  extends  from  the  apex  of  the  urinary 
bladder  to  the  umbilicus  and  supports  the  peritoneum  somewhat  in  the  manner 
of  a  ridge-pole  of  a  tent,  so  that  between  it  and  the  abdominal  wall  there  is  an 
interval  occupied  only  by  loose  areolar  tissue  and  termed  the  prevesical  space  of 
Retzius  (page  1906). 

Laterally  from  the  urachus  a  fibrous  cord,  the  latei'al  ligame?it  of  the  umbilicus, 
may  be  seen  on  each  side,  passing  from  the  side  of  the  bladder  to  the  umbilicus  and 
representing  the  obliterated  hypogastric  arteries  of  the  fcetus  ;  while  still  more  laterally 
there  may  be  seen  coming  from  the  external  iliac  artery  the  inferior  or  deep  epigas- 
tric artery,  which,  passing  immediately  to  the  inner  side  of  the  internal  abdominal 
ring  and  posterior  to  the  interfoveolar  ligament  (Fig.  532),  extends  upward  and 
inward  to  penetrate  the  posterior  layer  of  the  sheath  of  the  rectus  a  short  distance 
below  the  level  of  the  umbilicus.  Both  these  structures  produce  a  slight  ridging  or 
fold  of  the  peritoneum,  that  formed  by  the  obliterated  hypogastric  artery  being  termed 
the  plica  umbilicalis  lateralis,  while  the  other  is  the  plica  epigastrica.  These  two 
folds,  together  with  the  urachus,  mark  off  the  lower  portion  of  the  abdominal  wall 


526 


HUMAN    ANATOMY. 


into  three  areas  or  fovea?  (Fig.  532).  The  median  of  these  fovea?  lies  between  the 
urachus  and  the  lateral  umbilical  fold  and  forms  the  supravesical  fossa,  having  for 
its  floor  the  rectus  muscle.  Between  the  lateral  umbilical  and  the  epigastric  folds 
is  the  inner  inguinal  fossa,  having  for  its  floor  the  conjoined  tendon,  and  being 
therefore  the  region  in  which  direct  inguinal  hernias  arise  ;  and  lateral  to  the  epi- 

Fig.  532. 


Peritoneal  surface 


Plica  epigastrica. 

Hesselbach's  triangle, 

Vas  deferens. 

External  iliac  artery 
External  iliac  vein 


Median  umbilical  ligament 

Posterior  surfac 


Outer  inguinal  fossa 
Inner  inguinal  fossa 


of  anterior  abdo 


al  wall  of  formalin  subject. 


gastric  fold  is  the  outer  inguinal  fossa,  in  whose  floor  is  found  the  internal  abdominal 
ring,  just  to  the  outer  side  of  the  deep  epigastric  artery. 

The  triangular  area  bounded  by  Poupart's  ligament  below,  the  lateral  edge  of 
the  rectus  muscle  medially,  and  the  plica  epigastrica  laterally  has  been  termed  the 
triangle  of  Hesselbach.  It  is  almost  identical  with  the  middle  inguinal  fossa,  and 
defines  a  little  more  precisely  the  seat  of  the  direct  hernias. 

(c)    THE   HYPOSKELETAL  MUSCLES. 

It  seems  probable  that  the  psoas  major  and  the  psoas  minor  muscles  are,  in  part 
at  least,  assignable  to  the  group  of  abdominal  hyposkeletal  muscles.  The  close 
association  of  the  psoas  major  with  the  iliacus  and  its  attachment  to  the  femur  make  it 
convenient,  however,  to  defer  their  description  until  later  (page  623). 


PRACTICAL  CONSIDERATIONS. 


THE   ABDOMEN. 

The  abdominal  cavity  is  bounded  above  by  the  diaphragm  ;  below  by  the  floor 
of  the  pelvis  ;  laterally  by  the  diaphragm,  the  lower  ribs,  the  abdominal  muscles,  and 
the  lateral  expansions  of  the  ilia  ;  posteriorly  by  the  diaphragm,  the  tenth,  eleventh, 
and  twelfth  ribs,  the  lumbar  muscles  and  vertebrae,  the  posterior  portions  of  the  ilia, 
and  the  ischial,  sacral,  coccygeal,  and  pubic  bones  ;  and  inferiorly  by  the  levatores 
ani  and  coccygei  muscles.  It  should  be  noted  that  the  roof,  the  floor,  and  much  of 
the  remaining  parietes  of  the  abdomen  are  made  up  of  muscular  tissue  which,  by 
contraction  or  by  relaxation  or  stretching,  can  alter  the  size  of  the  cavity,  affect  the 
relations  of  the  contained  viscera,  and  vary  the  compression  to  whicffthey  are  subject. 
The  tonicity  of  the  muscular  walls  brings  about  a  normal  intra-abdominal  pressure 
which  serves  in  health  to  retain  in  position  and  to  give  support  to  the  viscera. 
This  pressure  is  increased  in  inspiration  and  by  straining,  lifting,  or  coughing.  It 
then,  by  increasing  the  outward  pressure  of  the  viscera  upon  the  internal  sur- 
face of  the  parietes,  favors  the  production  of  hernia,  the  protrusion  of  the  intestine 


PRACTICAL    CONSIDERATIONS  :    THE    ABDOMEN. 


527 


through  a  wound,  the  stretching  of  scars,  and  some  forms  of  dystocia  and  of  uterine 
displacement. 

The  pelvic  cavity — "a  recess  leading  downward  and  backward  from  the  abdomi- 
nal cavity  proper"  (Cunningham) — is  divided  from  the  latter  by  an  imaginary  plane 
extending  from  the  promontory  of  the  sacrum  to  the  upper  edge  of  the  pubes.  It 
will  be  considered  separately. 

The  general  shape  of  the  abdominal  cavity  is  described  on  page  161 5  as  are  also 
the  regions  into  which,  for  convenience,  the  abdomen  proper  may  be  divided  by  cer- 
tain arbitrary  lines  (page  161 5). 

The  structures  and  organs  underlying  the  spaces  thus  marked  out  are  approxi- 
mately as  follows  : 


Right  Hypochondriac. 

Greater  part  of  right  lobe  of 
liver,  hepatic  flexure  of  colon, 
and  part  of  right  kidney. 


Epigastric 

Greater  part  or  whole  of  left 
lobe  and  part  of  right  lobe  of 
liver,  with  gall-bladder,  part  of 
stomach,  including  both  ori- 
fices, first  and  major  portion 
of  the  second  parts  of  duo- 
denum, duodeno-jejunal  flex- 
ure, pancreas,  upper  or  inner 
end  of  spleen,  parts  of  kid- 
neys, and  suprarenal  bodies. 


Left  Hypochondriac 

Part  of  stomach,  portion  of 
spleen,  tail  of  pancreas,  splenic 
flexure  of  colon,  part  of  left 
kidney,  and  sometimes  part  of 
left  lobe  of  liver. 


Right  Lumbar. 

Ascending  colon,  part  of 
right  kidney,  and  sometimes 
part  of  ileum. 


Umbilical. 

Greater  part  of  transverse 
colon,  lower  portion  of  second 
and  much  of  third  part  of  duo- 
denum, some  convolutions  of 
jejunum  and  ileum,  with  por- 
tions of  mesentery  and  greater 
omentum,  part  of  right,  often 
of  left,  and  sometimes  of  both 
kidneys,  and  part  of  both 
ureters. 


Left  Lumbar. 

Descending  colon,  part  of 
jejunum,  and  sometimes  part 
of  left  kidney. 


Right  Iliac 

Caecum  with  vermiform  ap- 
pendix and  termination  of 
ileum. 


Hypogastric 

Convolutions  of  ileum,  blad- 
der in  children,  and  when  dis- 
tended in  adults  also,  uterus 
when  in  the  gravid  state,  and, 
behind,  sigmoid  flexure. 


Left  Iliac 

Sigmoid  colon,  convolutions 
of  jejunum  and  ileum. 


The  contents  of  the  various  regions  and  the  structures  intersected  by  the  different 
planes — if  the  arbitrary  lines  are  continued  into  planes — vary  considerably  within 
normal  limits  and  greatly  in  the  presence  of  disease. 

The  shape  and  size  of  the  abdomen  are  also  extremely  variable.  In  the  normal 
adult  male  it  is  irregularly  cylindrical,  with  a  central  bulging,  an  antero-posterior 
flattening,  and  a  greater  width  near  the  pelvis  than  near  the  ribs.  In  the  adult  female 
the  larger  relative  size  of  the  lower  abdomen  is  due  to  the  greater  development  of  the 
pelvis,  and  usually  to  flabbiness  of  abdominal  muscles  and  accumulation  of  fat  from 
want  of  exercise,  and  to  compression  of  the  upper  segment  by  corsets  ;  it  is  increased 
by  the  stretching  of  repeated  pregnancies.  In  infancy  and  childhood  the  abdomen  is 
prominent  on  account  of  the  undeveloped  condition  of  the  pelvis,  the  pelvic  viscera 
being  then  practically  within  the  abdomen,  and  is  broader  above  than  below  by 
reason  of  the  relatively  great  bulk  of  the  liver. 

In  obesity  the  weight  of  the  intra-abdominal  and  subcutaneous  fat  carries  the 
lower  part  of  the  abdominal  wall  downward  by  gravity,  stretches  it,  and  produces  a 
pendulous  abdomen.      This  condition  is  also  favored  by  ascites,  pregnancy,  etc.      In 


528  HUMAN    ANATOMY. 

emaciation  the  whole  anterior  abdominal  wall  becomes  concave  {scaphoid),  especially 
the  upper  portion  bounded  by  the  ensiform  cartilage  and  the  subcostal  angle, — the 
scrobiculus  cordis  (page  171), — which,  with  the  patient  supine,  may  appear  to  rest 
directly  upon  the  vertebral  column,  with  walls  more  nearly  vertical  than  horizontal. 

Congenital  defor?nities  of  the  abdominal  wall  usually  consist  in  a  failure  of  the 
ventral  plates  to  unite  in  the  middle  line,  producing  various  degrees  of  umbilical 
hernia  (q.v. )  or  leaving  the  contents  of  the  abdomen  uncovered  over  a  considerable 
area. 

Contusions  of  the  anterior  abdominal  wall,  bounded  laterally  by  the  outer  free 
border  of  the  external  oblique, — i.e. ,  by  a  line  just  external  to  a  vertical  line  dropped 
from  the  lowest  part  of  the  ninth  rib, — are  of  importance  in  relation  to  the  effect 
upon  the  organs  contained  within  the  abdomen.  As  the  skin  over  the  abdomen  and 
the  abdominal  muscles  receive  their  nerve-supply  from  the  lowest  six  intercostal 
nerves  and  the  branches  of  the  anterior  division  of  the  first  lumbar,  the  contraction 
of  the  muscles  upon  the  approach  of  danger,  if  not  voluntary,  may  be  reflexly 
hastened  at  the  moment  of  external  application  of  force,  and  a  protecting  elastic 
barrier  may  thus  be  interposed  between  the  latter  and  the  abdominal  contents.  The 
rigidity  caused  by  the  contact  of  a  cold  hand  with  the  abdominal  surface,  preventing 
palpation  of  the  viscera  beneath,  affords  a  familiar  illustration  of  the  close  relation 
between  skin  and  muscles.  The  relation  of  the  nerve-supply  of  the  muscles  and 
that  of  the  underlying  viscera  explains  the  rigidity  of  the  belly  so  usually  seen  in 
injury  or  disease  of  abdominal  organs  (page  1683).  Finally  the  relation  of  the  cuta- 
neous and  muscular  branches  of  the  intercostal  nerves  is  well  shown  by  the  sudden 
inspiratory  effort  caused  by  a  dash  of  cold  water  on  the  lower  thoracic  or  abdominal 
region,  six  of  these  nerves  supplying  the  intercostal  muscles  as  well  as  the  antero- 
lateral surface  of  the  chest  and  belly. 

The  injurious  effect  of  contusions  is  diminished  by  the  presence  of  a  thick  layer 
of  subcutaneous  fat  or  by  the  interposition  of  a  fleshy  omentum.  If  the  abdominal 
muscles  are  relaxed,  serious  injury  to  the  viscera  may  be  done  without  obvious 
damage  to  the  parietes.  Absence  of  ecchymosis  or  other  visible  sign  of  injury  should 
therefore  not  lead  to  an  absolutely  favorable  prognosis  until  after  the  lapse  of  suffi- 
cient time  to  permit  of  the  development  of  visceral  symptoms. 

Wounds. — The  thinness  and  loose  attachment  of  the  skin  of  the  abdomen  favor 
the  occurrence  of  cellulitis  as  a  result  of  infection  from  superficial  wounds.  The 
superficial  layer  of  the  superficial  fascia  contains  the  greater  part  of  the  subcutaneous 
fat  and  covers  the  superficial  blood-vessels.  The  thickness  of  the  abdominal  wall 
depends  chiefly  upon  the  thickness  of  this  fatty  layer,  which  may  be  of  several  inches. 
An  abdominal  wound  may  therefore  be  of  considerable  depth  and  yet  be  attended  by 
little  or  no  bleeding  and  be  practically  ' '  superficial. ' '  The  deeper  layer  of  the  super- 
ficial fascia  (page  515)  is  firmer,  is  elastic,  and  in  its  lower  part  is  the  vestige  of  the 
"tunica  abdominalis,"  well  developed  in  the  horse  and  some  other  quadrupeds  for 
reinforcement  of  the  abdominal  muscles,  on  which  the  weight  of  the  viscera  comes 
more  directly  than  in  man.  It  is  attached  in  the  middle  line  to  the  deeper  struc- 
tures and  to  the  iliac  crest,  and  below  Poupart'  s  ligament  blends  with  the  fascia  lata 
of  the  thigh.  It  is  not  attached  over  the  space  between  the  pubic  spine  and  symphysis, 
but,  being  carried  downward  over  the  spermatic  cord,  becomes  continuous  with  the 
dartos  layer  of  the  scrotum  and  with  the  fascia  of  Colles.  Cellulitis  superficial  to  this 
layer  may  therefore  spread  in  all  directions,  but  beneath  it  is  likely  to  be  at  least  tempo- 
rarily arrested  at  the  lines  of  attachment  indicated.  General  emphysema,  effusions  of 
blood,  and  collections  of  pus  have  for  a  time  similar  limitations.  They  are  apt  to  be 
guided  by  this  fascia  into  the  space  between  the  spine  and  the  symphysis  and  to  descend 
into  the  scrotum  and  towards  the  perineum,  where  the  lateral  attachments  of  Colles' s 
fascia  to  the  margins  of  the  pubic  arch  and  posteriorly  to  the  base  of  the  triangular 
ligament  prevent  their  spreading  in  those  directions.  More  usually  the  extravasa- 
tion— -blood,  pus,  or  urine — gains  this  subfascial  space  below,  as  from  rupture  of  the 
urethra  anterior  (inferior)  to  the  triangular  ligament  (page  1932),  and  ascends  to  the 
abdomen  by  the  same  route,  being  prevented  from  crossing  the  mid-line  or  descend- 
ing to  the  thighs  by  the  attachments  of  the  deep  layer  of  the  superficial  fascia  that 
have  been  described. 


PRACTICAL   CONSIDERATIONS  :    THE   ABDOMEN.  529 

Wounds  involving  the  muscular  layers  of  the  abdominal  wall  may  gape  widely, 
but  the  differing  directions  of  the  fibres  of  the  external  oblique,  internal  oblique, 
and  transversalis  tend  to  limit  this  just  as  they  lessen  the  after-risk  of  ventral  .hernia 
and  favor  certain  physiological  acts,  as  the  emptying  of  the  bladder,  the  bowels,  or 
the  uterus.  This  difference  of  direction  is  taken  advantage  of  in  gaining  access  to  the 
abdominal  cavity  in  some  operations  (page  535). 

Infection  in  the  lateral  intermuscular  spaces  usually  spreads  rapidly  on  account 
of  the  abundance  of  loose  cellular  tissue.  The  cellulitis  or  resulting  abscess  (or 
collection  of  blood  or  air)  will  be  limited  by  the  semilunar  line  in  front,  by  the  costo- 
chondral  arch  above,  by  Poupart's  ligament  and  the  crest  of  the  ilium  below,  and  by 
the  edge  of  the  erector  spinae  behind  ;  in  other  words,  by  the  attachments  of  the 
muscles  between  which  they  spread  (Treves). 

Beneath  the  abdominal  wall,  practically  making  a  portion  of  it,  lies  a  layer  of 
loose  connective  tissue — the  subperitoneal  or  subserous  areolar  tissue — which  connects 
the  peritoneum  with  the  parietes.  ' '  Extraperitoneal  connective  tissue' '  has  been  sug- 
gested (Eccles)  as  a  better  name  for  it.  Infection  of  this  tissue,  whether  from  without, 
as  in  the  case  of  wounds,  or  by  extension  from  some  of  the  viscera  lying  wholly  or 
partly  behind  the  peritoneum,  as  in  perirenal  abscess  or  certain  forms  of  appendiceal 
abscess,  is  likely  to  spread  widely.  Abscesses,  especially  if  chronic,  often  gravi- 
tate into  the  iliac  fossa  and  are  arrested  at  Poupart's  ligament  by  the  junction  of  the 
transversalis  and  iliac  fasciae,  constituting  a  form  of  iliac  abscess.  If  they  are  incised 
here,  it  will  usually  be  necessary  to  go  through  only  the  abdominal  muscles  and 
aponeuroses,  including  the  transversalis  fascia,  as  the  looseness  and  abundance  of 
the  subserous  tissue  will  have  permitted  the  abscess  to  dissect  off  and  push  upward 
the  peritoneum.  If  the  patient  is  supine,  pus  in  the  iliac  fossae — i.e.,  in  the  shallow 
lower  zone  of  the  abdomen — may  gravitate  into  the  deep  lateral  recesses  of  the 
middle  zone  (page  1615),  and  it  often  takes  this  direction  in  cases  in  which  the 
source  of  infection  is  an  appendix  situated  behind  the  caecum.  It  should  be  noted 
that  a  true  iliac  abscess  is  beneath  the  iliac  fascia,  and  is  therefore  more  apt  to 
be  guided  by  that  fascia  to  the  lowest  point  of  the  ilio-psoas  space  and  to  pass 
with  the  ilio-psoas  muscle  into  the  thigh,  pointing  at  the  outer  side  of  the  femoral 
vessels. 

The  laxity  of  the  subserous  tissue  favors  certain  retroperitoneal  operations — 
e.g. ,  uretero-lithotomy — by  permitting  the  stripping  forward  of  the  peritoneum 
itself.  The  relatively  great  resistant  power  of  the  side  of  the  peritoneum  in  contact 
with  this  tissue  is  subsequently  described  (page  1754).  The  fat  contained  in  this 
layer — greatest  in  the  lumbar  region  {perinephric  fat)  and  in  front  of  the  bladder  in 
the  space  of  Retzius  (the  triangular  interval  defined  by  the  symphysis  pubis,  the 
bladder,  and  the  peritoneum),  and  abundant  in  the  inguinal  and  iliac  regions — 
may  serve  as  a  guide  in  approaching  the  peritoneum  by  incision,  or  may  mislead  if 
mistaken  for  the  omental  fat.  The  latter  error  has  resulted,  as,  for  example,  in 
operation  for  ovarian  cyst,  in  regarding  the  peritoneum  as  the  cyst-wall,  and  in 
detaching  it  from  the  parietes  over  a  wide  area.  This  fat  occasionally  works  its  way 
through  intervals  between  the  fibres  of  the  overlying  fascia  or  muscles,  especially 
along  the  linea  alba,  and  constitutes  the  subseroics  lipomata,  which,  if  large  enough, 
are  sometimes  thought  to  be  irreducible  ventral  herniae.  The  laxity  of  the  subse- 
rous areolar  layer  between  the  bladder  and  the  posterior  surface  of  the  symphysis 
pubis  permits  the  peritoneum  to  be  carried  up  on  the  summit  of  a  distended  bladder 
as  it  rises  into  the  abdomen  and  thus  facilitates  extraperitoneal  access  to  the  an- 
terior vesical  wall  (page  1912).  Its  looseness  over  the  iliacus  muscle  is  a  factor 
in  the  formation  of  the  sac  of  inguinal  hernia  (page  1767).  Wounds  of  the  abdom- 
inal wall  dividing  this  subserous  layer,  but  leaving  the  peritoneum  untouched, 
should  practically  be  classified  among  non-penetrating  wounds,  although  in  a  sense 
the  abdominal  cavity  has  been  opened.  The  symptoms  and  dangers  of  infec- 
tion will  be  as  above  enumerated.  Wounds  involving  the  peritoneum  are  called 
penetrating  wounds,  the  dangers  of  which  have  been  considered  in  the  section  on 
the  peritoneum. 

In  the  closing  of  abdominal  wounds  the  irregularities  that  may  result  from  the 
differing  directions  of  the  muscular  fibres  involved — causing  greater  retraction  at  one 

34 


53o  HUMAN   ANATOMY. 

point  than  at  another — should  be  remembered.  This  may  make  accurate  suturing- 
in  layers  difficult,  but  such  suturing,  together  with  careful  approximation  of  the  edges- 
of  the  peritoneal  layer,  is  necessary  to  lessen  the  risk  of  ventral  hernia. 

The  respiratory  movements  prevent  the  attainment  of  absolute  rest  during  the 
healing  of  abdominal  wounds,  as  they  do  after  fractures  of  ribs  ;  but  in  both  cases 
approximate  rest,  as  secured  by  strapping  with  adhesive  plaster  or  by  abdominal 
binders,  gives  excellent  average  results. 

THE  LOIN. 

The  posterior  abdominal  wall  is  in  far  less  intimate  association  with  the  peri- 
toneum or  the  small  intestine,  and  is,  in  its  relation  to  injury  or  disease,  of  less- 
importance  than  the  antero-lateral  walls,  but  it  will  be  convenient  to  consider  it  and 
the  loin  here.  Contusions,  if  over  the  ilio-costal  space, — the  posterior  segment  of 
that  portion  of  the  abdominal  wall  which  has  no  bony  protection, — are  apt,  if  severe 
enough,  to  result  in  injury  to  the  friable  kidneys  (page  1891)  rather  than  to  the  rela- 
tively strong  and  elastic  ascending  or  descending  colon.  Wounds,  if  they  pass- 
through  the  entire  thickness  of  the  wall,  may  involve  either  of  these  structures. 
When  they  become  infected,  the  resulting  cellulitis  or  abscess  will  be  influenced  as  to 
the  direction  it  takes  and  in  its  limitations  by  the  various  fasciae  and  muscular  sheaths. 
The  subcutaneous  connective  tissue  is  loose  and  abundant,  and  is  frequently  the  seat 
of  suppuration  or  of  extensive  collections  of  blood  which  gravitate  towards  the  iliac 
crest  or  pass  below  it.  The  boundaries  of  effusion  into  the  intermuscular  spaces: 
external  to  the  edge  of  the  erector  spinae  have  already  been  described  {vide  supra). 
Within  the  musculo-aponeurotic  compartments  made  by  the  splitting  of  the  strong- 
lumbar  fascia  into  three  layers  (page  508)  and  enclosing  the  erector  spina?  and 
quadratus  lumborum  muscles  the  products  of  suppuration  may  for  a  time  be  con- 
fined. The  middle  and  posterior  layers  are,  moreover,  very  dense  and  resistant,  and 
therefore,  as  they  form  the  sheath  of  the  erector  spina?,  that  muscle  is  rarely  the  seat 
of  abscess  of  other  than  vertebral  origin  ;  beginning  in  caries  of  the  neural  arches, 
however,  an  abscess  may  directly  penetrate  the  muscle  between  its  fibres  of  origin  or 
insertion.  The  anterior  layer,  separating  the  quadratus  lumborum  from  the  sub- 
serous areolar  tissue,  is  very  thin  and  is  continuous  with  the  transversalis  fascia.  For 
this  reason,  abscesses  originating  about  the  kidney  or  around  the  caecum  or  sigmoid 
not  infrequently  perforate  this  layer  and  pass  either  directly  through  the  outer  third 
of  the  thin  quadratus  lumborum  external  to  the  erector  spinae  (which  buttresses  its 
inner  two-thirds)  or  through  the  transversalis  fascia  external  to  the  quadratus.  If 
they  are  high  (perirenal),  they  may  follow  the  last  dorsal  nerve,  which  pierces  this 
fascia  and  the  transversalis  muscle  just  below  the  last  rib,  and  may  then  make  their 
way  through  the  internal  oblique  and  appear  at  the  outer  border  of  the  erector 
spinae  ;  or  they  may  gravitate  to  the  triangle  of  Petit, — the  interval  between  the 
crest  of  the  ilium  (its  base)  and  the  converging  edges  of  the  external  oblique  and 
latissimus  dorsi, — where,  as  the  floor  of  the  triangle  is  formed  by  the  internal 
oblique,  they  will  be  subcutaneous  as  soon  as  they  have  perforated  the  latter  muscle. 
An  abscess  of  lower  origin  (pericaecal,  pericolic)  may  reach  the  same  space  by  fol- 
lowing the  ilio-hypogastric  branch  of  the  first  lumbar  nerve. 

Abscesses  in  the  lumbar  subse?'Ous  areolar  tissue  are  more  frequent  on  the  right 
side,  on  account  of  the  presence  of  the  appendix.  Like  abscesses  of  perinephric 
origin  occupying  the  same  situations,  they  may  open  into  the  colon  or  sigmoid.  As 
this  tissue  is  continuous  below  with  the  corresponding  layer  in  the  pelvis,  abscesses 
originating  there  may  ascend  and  appear  at  one  or  other  of  the  various  points  de- 
scribed. True  iliac  abscesses  {vide  supra')  are  beneath  the  iliac  fascia,  which  is  con- 
tinuous with  the  transversalis  fascia  at  Poupart's  ligament,  but  encloses  the  ilio-psoas 
muscle  in  a  definite  compartment,  weak  below,  where  the  fascia  accompanies  the 
muscle  beneath  Poupart's  ligament  to  become  the  pectineal  fascia.  The  upper  part 
of  this  fascia,  covering  the  psoas  muscle,  is  thinner  and  less  resistant  than  the  lower. 
Abscesses  beginning  in  disease  of  the  lumbar  spine  may  penetrate  directly  into  the 
muscular  substance.  Those  beginning  in  the  thoracic  spine  are  often  so  limited  an- 
teriorly by  the  internal  arcuate  ligament  and  posteriorly  by  the  spine  and  last  rib 


PRACTICAL    CONSIDERATIONS  :    THE   ABDOMEN.  531 

that  they  are  diverted  into  the  psoas  sheath  between  those  slips  of  origin  of  the 
muscle  which  come  from  the  bodies  of  the  vertebra?  and  those  which  come  from 
the  transverse  processes.  Often  the  pus  descends,  as  in  iliac  abscess,  to  point  on 
the  thigh  external  to  the  femoral  vessels,  but  not  infrequently  it  passes  under  the 
external  arcuate  ligament  or  penetrates  the  psoas  sheath  at  its  outer  edge  and 
the  anterior  layer  of  the  lumbar  aponeurosis  (to  which  it  is  there  attached)  and 
points  in  the  loin,  in  which  case  it  may  be  mistaken  for  one  of  the  abscesses  origi- 
nating in  or  spreading  through  the  subserous  areolar  tissue. 

In  the  typical  psoas  abscess  the  thigh  is  flexed  to  relax  the  muscle  and  its 
sheath  and  to  lessen  the  compression  of  the  lumbar  nerves  which  are  contained 
within  it.  It  will  be  observed  that  a  psoas  or  a  true  iliac  abscess  is  in  close  relation 
to  these  nerves,  but  is  separated  from  the  iliac  vessels  and,  except  at  the  upper  por- 
tion, from  the  genito-crural  nerve  by  the  thick  iliac  fascia.  Iliac  aneurism  may, 
however,  by  pressure  cause  flexion  of  the  thigh  and  pain  in  the  course  of  the  same 
nerves. 

LANDMARKS  AND  TOPOGRAPHY   OF  THE   ABDOMEN. 

1.  The  bony  and  cartilaginous  structures  that  constitute  the  apparent  limits  of 
the  abdomen,  and  that  are  either  visible  or  palpable,  are  as  follows  : 

(a)  The  tip  of  the  ensiform  cartilage,  on  a  level  with  the  lower  part  of 
the  body  of  the  tenth  dorsal  vertebra.  (<5)  The  seventh,  eighth,  ninth,  and  te?ith 
costal  cartilages,  forming  the  lateral  boundaries  of  the  infrasternal  fossa  (Fig.  173, 
page  171).  A  notch  that  may  be  felt  on  the  costal  border  indicates  the  point  of 
union  of  the  tip  of  the  tenth  to  the  edge  of  the  ninth  cartilage  (Woolsey).  (c)  The 
tips  of  the  eleventh  and  twelfth  costal  cartilages  are  free,  except  as  they  are  con- 
nected with  each  other  by  the  intercostal  and  abdominal  muscles.  Sometimes  the 
twelfth  rib  is  rudimentary  and  does  not  project  beyond  the  external  edge  of  the 
erector  spinae  muscle.  Hence  in  planning  operations  that  open  the  abdominal  cavity 
just  below  that  rib — as  in  nephrotomy — it  is  well  to  count  the  ribs  from  above  ;  other- 
wise the  pleura  might  be  opened  by  mistake  (Fig.  1581).  (  d)  The  spines  of  the 
lumbar  vertebra,  corresponding  to  their  bodies  and  representing  the  posterior  bony 
wall  of  the  abdomen,  are  useful  landmarks.  Their  relation  to  the  abdominal  con- 
tents as  to  level  has  been  described  (page  148).  (e)  The  crest  of  the  ilium,  the 
anterior  and  posterior  iliac  spines,  and  the  pubic  spine  and  symphysis  have  been 
described  (page  349). 

2.  The  skin  is  usually  creased  or  furrowed  in  proportion  to  the  amount  of 
subcutaneous  fat  or — in  thin  persons — to  the  muscular  development.  In  fat  per- 
sons two  deep  transverse  furrows  form  across  the  abdomen.  In  the  upper  one, 
which  intersects  the  umbilicus,  the  latter  may  be  completely  concealed.  The  lower 
one  runs  just  above  the  crest  of  the  pubes.  Its  point  of  intersection  with  the 
linea  alba  is  a  convenient  landmark  for  the  introduction  of  the  trocar  in  suprapubic 
tapping  of  a  distended  bladder.  It  is  of  use  in  the  diagnosis  of  femoral  hernia 
(page  1774). 

In  cases  of  ankylosis  of  the  hip-joint  transverse  creases  may  be  seen  running 
across  the  belly  between  the  umbilicus  and  the  pubes.  They  are  produced  by  the 
freer  bending  of  the  spine  that  is  apt  to  occur  in  such  cases,  the  absence  of  some  of 
the  simpler  movements  of  the  hip-joint  in  flexion  and  extension  being  compensated 
for  by  increased  motion  of  the  vertebral  column  (Treves). 

The  stria  gravidarum  are  sinuous,  silvery  streaks,  resembling  scars,  that  follow 
atrophy  of  the  connective-tissue  layers  of  the  skin  from  stretching  due  to  abdom- 
inal distention,  as  in  pregnancy,  ovarian  cysts,  or  ascites. 

3.  Intermuscular  or  Interfascial  Markings. — The  linea  alba — the  fibrous  raphe 
formed  by  the  union  of  the  sheaths  of  the  recti  at  their  inner  borders — may  be  seen 
as  a  very  shallow  groove  extending  from  the  ensiform  cartilage  to  the  umbilicus. 
Below  the  tip  of  the  xiphoid  this  may  be  a  quarter  of  an  inch  in  breadth,  and  it 
is  apt  to  be  slightly  wider  just  above  the  umbilicus.  From  a  little  below  that  level 
— one  to  two  inches — it  cannot  be  seen,  as  until  it  nears  the  symphysis  it  is  merely 
a  line   of   fibrous  tissue  resulting:    from  the   coalescence  of    the  sheaths.       A  little 


532 


HUMAN    ANATOMY. 


above  the  symphysis  it  widens  into  a  narrow  triangle  (adminiculum),  but  is  still 
not  visible  on  account  of  the  suprapubic  fat.  It  may  be  congenitally  much  wider 
than  normal,  or  may  be  stretched  by  abdominal  swellings,  and  in  either  case  may 
be  the  seat  of  ventral  hernia.  The  absence  of  blood-vessels  in  and  over  the  linea 
alba  and  its  thinness  lead  to  its  selection  as  the  site  of  the  incision  in  many 
abdominal  operations. 

The  linea  semilunaris,  corresponding  to  the  other  border  of  the  sheath  of  the 
rectus  muscle,  may  be  seen  when  the  rectus  contracts  as  a  curved  line  from  6.5  to 
7.5  cm.  (2^-3  in.)  external  to  the  linea  alba,  at  the  level  of  the  umbilicus,  with  its 

Fig.  533- 


Infraclavicular  fossa 
Coracoid  process      ^ — -\ 


,  Suprasternal  notch 
Clavicle 
^Sternum 

'Acromion 


Groove  between  deltoid- 
and  pectoralis  major 


X-rib  cartilage 


Ensiform  cartilage 


!  Linea  alba 

j 


Anterior  superior  iliac  spine- 
Line  of  Poupart's  ligament  _ 


Anterior  surface  of  trunk,  from  photograph  of  living  model ;  bony  landmarks  have  been  somewhat  exaggerated. 


concavity  inward,  extending  from  the  tip  of  the  ninth  costal  cartilage  to  the  spine  of 
the  pubes.  As  it  marks  the  point  of  division  of  the  abdominal  aponeuroses 
(Fig.  529)  to  form  the  sheath  of  the  rectus,  it  also  marks  a  frequent  line  of  limita- 
tion of  emphysematous,  hemorrhagic,  or  purulent  extravasations  in  the  lateral  inter- 
muscular spaces  {vide  supra). 

The  linece  transversce,  which  may  also  be  seen  as  shallow  grooves  when  the 
rectus  is  in  action,  and  are  most  marked  in  muscular  persons,  correspond  to  the 
tendinous  intersections  that  interrupt  the  longitudinal  fibres  of  the  rectus.  They 
are    the    representatives  of    the  intersegmental    septa  which   separate    the    original 


PRACTICAL    CONSIDERATIONS  :    THE    ABDOMEN.  533 

myotomes  giving  rise  to  the  muscles  of  the  abdomen  ;  in  some  of  the  lower  verte- 
brates (reptiles)  these  intersections  are  replaced  by  bony  bars,  as  seen  in  the 
abdominal  ribs  of  crocodiles  and  some  lizards  (Hatteria).  The  highest  is  about  the 
level  of  the  tip  of  the  ensiform  cartilage,  the  next  at  that  of  the  tenth  rib,  the  third 
at  the  umbilicus.  Very  rarely  a  fourth  line  is  seen  below  this  level.  The  second 
and  third  are  the  most  constant,  and  divide  the  upper  part  of  each  rectus  into  two 
nearly  quadrilateral  portions,  easily  seen  in  athletic  subjects.  These  bands  tend  to 
prevent  overstretching  or  rupture  of  the  rectus  in  cases  of  great  abdominal  swelling 
or  of  violent  contraction.  The  anterior  sheath  of  the  rectus  is  adherent  to  these 
fibrous  bands.  Hence  an  abscess  or  a  collection  of  blood  on  that  aspect  of  the 
muscle  may  be  confined  to  the  space  between  any  two  of  them.  Posteriorly  this  is 
not  the  case.  Spasmodic  contraction  of  the  rectus  fibres  in  one  of  these  divisions  of 
the  rectus  is  the  cause  of  one  variety  of  "phantom  tumor,"  the  swelling  appearing 
and  vanishing  with  contraction  and  relaxation  of  the  fibres, — a  phenomenon  most 
frequently  seen  in  neurasthenics,  but  which  in  this  instance  may  occasionally  indicate 
a  reflex  disturbance  based  on  some  deep-seated  source  of  irritation.  Treves  has 
seen,  for  example,  this  condition  associated  with  cancer  of  the  stomach,  duodenal 
ulcer,  and  malignant  disease  of  the  peritoneum. 

The  inguinal  groove  runs  with  a  slight  downward  curve  from  the  anterior 
superior  iliac  spine  to  the  pubic  spine  and  corresponds  to  Poupart's  ligament.  As 
this  latter  structure  results  from  a  thickening  of  the  lowest  fibres  of  the  aponeurosis 
of  the  external  oblique,  and  as  the  internal  oblique  and  transversalis  muscles  arise 
from  its  outer  half,  it  follows  that,  by  reason  of  its  direct  continuity  with  the  fascia 
lata,  extension  of  the  thigh  on  the  trunk  increases  the  tension  of  the  anterior 
abdominal  wall.  Hence  in  abdominal  examinations  the  thighs  are  flexed  on  the 
abdomen  to  lessen  this  tension.  At  the  same  time  the  shoulders  and  trunk  should 
be  slightly  elevated  to  relax  the  recti. 

Posteriorly  the  spinal  furrow  marks  the  interval  between  the  erector  spina? 
muscles  and  the  line  of  attachment  of  the  skin  to  the  tips  of  the  lumbar  spines. 
Farther  out  the  outer  edge  of  the  erector  spinee  is  palpable  and  often  visible,  except 
in  very  fat  persons.  Occasionally  the  posterior  free  edge  of  the  external  oblique  may 
be  seen  when  it  is  not  overlapped  bv  the  latissimus  dorsi. 

4.  The  umbilicus,  except  as  a  landmark,  is  of  chief  interest  in  relation  to  hernia, 
in  connection  with  which  it  will  be  described.  The  creases  around  and  between  the 
folds  of  skin  forming  the  umbilical  papilla  are  difficult  to  sterilize,  and  should  receive 
especial  attention  before  operation. 

Fistula;  at  the  umbilicus  may  be  urinary  and  due  to  a  patent  urachus  (page  191 1 ), 
or  fecal,  resulting  from  a  persistent  vitello-intestinal  duct, — Meckel's  diverticulum 
(page  1652). 

5.  The  Vessels. — The  most  important  artery  is  the  deep  epigastric  (o.v.), 
but  branches  of  the  deep  circumflex  iliac,  the  last  two  intercostals,  and  the  abdominal 
branches  of  the  lumbars  may  require  ligation  during  various  abdominal  operations. 
The  course  of  the  deep  epigastric  artery,  which  is  sometimes  the  source  of  trouble- 
some hemorrhage,  should  be  remembered  in  studying  the  anterior  wall  of  the 
abdomen.  A  line  drawn  with  a  slight  inward  curve  from  the  junction  of  the  inner 
and  middle  thirds  of  Poupart's  ligament  towards  the  umbilicus,  crossing  the  outer 
edge  of  the  rectus  muscle  about  one-third  the  distance  between  the  level  of  the  sym- 
physis pubis  and  that  of  the  navel,  will  indicate  the  course  of  the  lower  part  of  this 
vessel.  At  the  internal  abdominal  and  the  femoral  rings  it  has  important  relations 
to  hernial  sacs  (page  1493) ;  it  lies  at  first  at  the  side  of  the  rectus  in  the  subserous 
areolar  tissue,  then  in  the  transversalis  fascia,  then  within  the  sheath  of  the  rectus 
(above  the  fold  of  Douglas)  behind  the  middle  of  the  muscle,  and  finally  in  the 
muscle  itself.  It  therefore  runs  from  without  inward  and  becomes  more  superficial 
as  it  ascends. 

With  the  exception  of  the  superior  epigastric  and  ascending  lumbar,  all  the 
abdominal  and  pelvic  veins  empty  directly  or  indirectly  into  the  inferior  vena  cava 
and  are  therefore  affected  by  the  conditions  that  obstruct  that  vessel  ;  hence  the 
superficial  veins  are  often  varicose.  Although  their  varicosity  is  usually  a  result  of 
obstruction  in  the  portal  vein  or  inferior  vena  cava,  it  may  occur  independently  of 


534 


HUMAN   ANATOMY. 


obstructive  cause,  as  do   many  cases  of  varicose  veins  of  the  lower  extremity,  and 
may  be  very  large  and  extremely  tortuous  {caput  medusa). 

The  mechanism  of  the  production  of  this  form  of  varicosity  by  portal  obstruc- 
tion will  be  more  readily  understood  by  reference  to  Fig.  534,  which  also  explains 
other  phenomena  associated  with  that  condition. 

The  superficial  epigastric  vein  is  often  visible.  Through  its  anastomosis  with 
the  deep  and  superior  epigastric  veins  it  is  connected  with  the  portal  and  parumbilical 
veins  and  may  be  enlarged  as  a  symptom  of  hepatic  disease  (page  1727). 

The  area  of  redness  about  the  umbilicus  seen  in  some  forms  of  peritonitis  is 
probably  due  to  inflammation  extending  along  the  obliterated  umbilical  veins 
(page  1757). 

The  surface  veins  above  the  umbilicus  empty  into  the  axilla  and  those  below  that 
level  into  the  groin,  but  the  venous  currents  may  be  reversed  by  disease.  For 
example,  the  superficial  epigastric  and  superficial  circumflex  iliac  normally  empty 
into  the  internal  saphenous  vein  a  little  below  Poupart's  ligament.  In  cases  of 
obstruction  of  the  inferior  vena  cava  the  blood-current  is  reversed  (as  it  is  in  the 
corresponding  deep  veins),  they  enlarge,  and,  by  anastomosing  with  the  superior 
epigastric,  internal  mammary,  and  thoraco-epigastric  veins,  carry  blood  from  the 
lower  limbs  into  the  axillary  or  innominate,  and  so  into  the  superior  vena  cava. 

In  hepatic  obstruction,  although  the  superficial  epigastric  may  become  varicose 
(through  its  connection  with  the  parumbilical  and  portal  veins),  this  reversal  of  the 

blood-current  does  not  occur 
Fig.  534.  in  it,   as  may  be  shown    by 

emptying  the  vein  by  press- 
ure and  observing  the  di- 
rection of  the  current  as  it 
refills. 

The  superficial  lymphatics 
of  the  abdominal  wall  below 
the  umbilical  level  empty  into 
the  nodes  at  the  groin,  those 
above  that  level  into  the 
nodes  in  the  axilla.  * 

6.  The  nerves  of  the 
abdominal  wall  (page  535) 
have  already  been  described 
in  their  relation  to  various 
clinical  phenomena  (pages 
1683,1755).  In  addition,  it 
should  be  said  here  that  the 
definiteness  of  the  relation 
in  nerve-supply  between  cu- 
taneous areas  and  abdominal  organs  is  often  of  great  value  in  diagnosis.  As  the 
sixth  to  the  twelfth  thoracic  and  the  first  lumbar  spinal  segments  aid  in  the  nerve- 
supply  to  the  abdominal  viscera,  and  as  the  corresponding  spinal  nerves  supply  the 
skin  of  the  abdomen,  pain  due  to  visceral  disease  is  often  referred  (through  the  com- 
municating branches  with  the  splanchnic  and  the  sympathetic  visceral  nerves)  to  the 
peripheral  terminations  on  the  skin  of  the  abdomen,  which  may  even  be  sensitive  to 
the  touch. 

It  is  possible  to  map  out  approximately  on  the  surface  the  area  of  distribution 
of  the  cutaneous  branches  from  each  of  these  segments  (Fig.  535). 

Head  has  associated  as  follows  these  areas  (which  are  almost  identical  with  the 
areas  of  distribution  of  the  corresponding  spinal  nerves)  and  the  viscera  in  closest 
connection  with  them  : 

The  sixth,  seventh,  eighth,  and  ninth  thoracic  segments  with  the  stomach  ;  the 
ninth,  tenth,  eleventh,  and  twelfth  thoracic  segments  with  the  intestinal  tract  ;  the 
seventh,  eighth,  ninth,  and  tenth  thoracic  segments  with  the  liver  and  gall-bladder  ; 
the  tenth,  eleventh,  and  twelfth  thoracic  and  the  first  lumbar  segment  with  the  kid- 
ney and  ureter  ;  the  second,  third,  and  fourth  sacral  with  the  rectum. 


CAPUT 
MEDUSAE 

Diagram  showing  anatomical  relations  of  certain  clinical  phenomena 
cirrhosis  of  liver.     {After  Hare  and  Taylor.) 


PRACTICAL   CONSIDERATIONS  :    THE   ABDOMEN. 


535 


The  distribution  to  the  pelvic  organs  will  be  considered  later,  but  it  may  be  said 
here  that  the  pelvic  viscera  are  supplied  from  the  fifth  lumbar  to  the  fourth  sacral 
segment  and  that  no  visceral 

branches    emerge  from    the  Fig.  535. 

second,  third,  or  fourth  lum- 
bar segments. 

Division  of  any  of  the 
motor  nerves  interferes  with 
the  function  and  ultimately 
with  the  nutrition  of  that 
portion  of  the  musculature 
of  the  abdominal  wall  that  is 
supplied  by  them,  giving  rise 
to  weakness  over  that  area, 
favoring  the  development  of 
ventral  hernia,  and,  if  ex- 
tensive, interfering  with  the 
physiological  action  of  those 
muscles  in  defecation,  urina- 
tion, or  parturition. 

For  clinical  purposes 
these  nerves  may  be  divided 
into  three  groups  (Eads): 
(a)  the  seventh  and  eighth 
intercostal  s  ascend  obliquely 
and  supply  the  upper  third 
of  the  abdominal  wall  ;  (6) 
the  ninth  and  tenth  intercos- 
tals  run  horizontally  inward 
and  supply  the  middle  third  ; 
(c)  the  eleventh  intercostal, 
the  last  thoracic,  and  the  ilio- 
hypogastric and  ilio-inguinal 
nerves  run  obliquely  down- 
ward and  inward  and  supply 
the  lower  third. 

It  is  obvious  that  verti- 
cal incisions  elsewhere  than 
in  the  linea  alba  (the  nerves 
do  not  cross  the  mid-line) 
will  divide  a  larger  number 
of  these  nerves  and  result 
in  more  extensive  atrophy  of 
abdominal  wall  than  will  in- 
cisions more  nearly  parallel 
with  the  nerves  and,  when 
possible,  with  the  chief  mus- 
cular fibres  of  the  region  in- 
volved. 

The  Anatomy  of  Ab- 
dominal Incisions. — A  dia- 
grammatic representation  of 
the  structures  of  the  abdom- 
inal wall  in  their  relation  to 
the  most  important  incisions 
may  help  to  elucidate  the 
practical  application  of  some  of  the  above-mentioned  facts.  It  should  be  noted  that 
in  many  of  these  incisions  the  approximately  parallel  fibres  of  the  internal  oblique 
and  transversalis  (when  they  are  both  muscular)  may  be  regarded  as  one  layer  and 


I   W  1 


Diagram  of  distribution  of  cutaneous  nerves,  based  on  figures  of  Hasse 
and  of  Cunningham.  On  right  side,  areas  supplied  by  indicated  nerves  are 
shown:  on  left  side,  points  at  which  nerves  pierce  the  deep  fascia.  <  ', 
V-  V3  divisions  of  fifth  cranial  nerve ;  GA,  great  auricular;  GO,  S(A 
greater  and  smaller  occipital ;  SO  superficial  cervical  ;  St,  CI,  Ac,  sternal, 
clavicular  and  acromial  branches  nf  supraclavicular  l.sr/l  ;  Li,  circumnex  , 
MS,  musculu-spiral ;  IH,  intercosto-humeral  ;  L/C.  IC.  lesser  internal  and 
internal  cutaneous  ;  IiC,  external  cutaneous  ;  ///,  iliohypogastric  ;  11,  nit 
itu'ttinal-  r1'-,  last  thoracic;  GC,  genito-crural ;  EC,  external  cutaneous; 
WC  middle  cutaneous  ;  IC,  internal  cutaneous  ;  P,  pudic  ;  SS\  small  s 
O  obturator;  C,  T,  L,  and  5\  cervical,  thoracic,  lumbar,  and  spinal  nerves. 


536 


HUMAN    ANATOMY. 


separated  on  the  same  line.      No  effort  has  been  made,  therefore,  to  show  the  latter 
muscle  in  the  diagram. 

Incisions  Nos.  I,  2,  and  3  are  through  the  linea  alba,  No.  2  being  carried 
around  the  umbilicus  to  the  left  to  avoid  the  parumbilical  vein  and  the  round  liga- 
ment of  the  liver.  The  chief  advantage  is  the  accessibility  to  the  whole  cavity- 
afforded  by  prolonging  the  incision.  The  slight  vascularity  of  the  median  raphe 
and  the  thinness  of  the  abdominal  wall,  while  operative  advantages,  tend  to  favor 
the  later  production  of  hernia. 

Incision  No.  4  combines  the  disadvantages  of  the  incisions  through  the  linea 
alba  with  the  added  interference  with  the  nerve-supply  to  the  rectus. 

Incision  No.  5  (McBurney)  has  been  described  (page  1685).  It  represents 
merely  the  separation  of  the  aponeurotic  fibres  of  the  external  oblique  ;  the  deeper 
wound  separates  the  internal  oblique  and  transversalis  fibres  transversely.  It  may 
be  noted  that  its  inward  extension   (Weir J,  even  if  it  involves  division  instead  of 

retraction  of    the  rectus  (page  1685), 
Fig.  536.  would  equally  avoid  nerve-trunks,  but 

might  involve  ligation  of  the  deep  epi- 
gastric. The  resulting  scar  in  the 
rectus  would,  however,  merely  add  in 
effect  another  linea  transversa  and 
would  not  impair  the  efficiency  of  that 
muscle. 

Incision  No.  6  (Eads)  separates 
the  same  structures,  but  affords  a  bet- 
ter opportunity  for  approach  to  many 
appendicular  abscesses  without  going 
through  the  peritoneal  cavity  (page 
1685). 

The  incision  for  inguinal  colos- 
tomy (page  1688)  may  be  made  on  the 
same  lines  as  those  just  described. 

Incision  No.  7,  after  division  of 
the  external  oblique,  permits  the  sepa- 
ration of  the  fibres  of  the  internal  ob- 
lique and  of  the  upper  abdominal  in- 
tercostal nerves,  which,  like  the  others, 
run  beneath  that  muscle,  and  is  used 
to  gain  access  to  the  gall-bladder 
region. 

Incision  No.  8  also  respects  the 
internal  oblique  fibres  and  the  seventh  and  eighth  intercostal  nerves  and,  when 
used  for  gastrostomy,  permits  the  development  of  a  valvular  or  sphincteric  action 
about  the  orifice  (page  1633). 

Incision  No.  9 — the  vertical  incision  through  the  rectus  recommended  for  gas- 
trostomy (Howse) — must  divide  the  terminal  branches  of  the  intercostal  nerves,  and 
consequently  that  portion  of  the  muscle  distal  to  the  line  of  division  will  be  weakened 
or  paralyzed  and  unable  to  contribute  to  the  formation  of  a  sphincter  (Eads). 

The  incision  for  lumbar  colostomy  has  been  described  (page  1688).  The  re- 
maining incisions  through  the  loin  may  be  more  appropriately  considered  in  relation 
to  the  approach  to  the  kidneys  or  ureters  (page  1894). 

Anatomical  Relations  bea?-ing  on  the  Examination  of  the  Abdomen. — Harris  has 
suggested  utilizing  the  fixed  and  circuitous  route  of  the  colon  (Fig.  1383)  to  subdi- 
vide the  abdominal  cavity  by  taking  the  inner  or  mesial  layers  of  the  longitudinal 
mesocolons  and  the  inferior  layer  of  the  transverse  mesocolon  as  the  dividing  lines. 
We  would  thus  obtain  four  regions, — namely,  (1)  the  central  region  surrounded  by 
mesocolon,  (2)  the  superior  region  lying  above  the  transverse  mesocolon,  (3)  the 
right  postero-lateral  and  (4)  the  left  postero-lateral  regions  lying  external  to  and 
behind  the  longitudinal  mesocolons. 

Tumors  of  special  viscera  begin,  as  a  rule,  in  the  region  normally  occupied  by 


PRACTICAL    CONSIDERATIONS  :    THE    ABDOMEN.  537 

those  organs,   and  often,  when   they  overlap  its  boundaries,  displace   the  colon  in 
definite  directions. 

The  course  of  the  colon  being  made  apparent  by  inflating  it  with  air,  it  may 
therefore  be  said  that  : 

1.  Growth  in  the  central  region  would  include  tumors  of  the  omentum,  mesen- 
tery, small  intestine,  and  peritoneum,  many  retroperitoneal  tumors,  and  such  growths 
affecting  the  female  generative  apparatus  as  rise  from  the  pelvis  into  the  abdomen. 
In  the  latter  case  the  caecum  and  sigmoid  would  be  displaced  upward  and  outward. 

2.  Tumors  beginning  in  the  superior  region  would  include  those  of  the  liver, 
gall-bladder,  stomach,  lesser  omentum,  spleen,  and  pancreas.  Harris  calls  attention 
to  the  fact  that  pancreatic  cysts  have  usually  been  mistaken  for  ovarian  cysts, 
although  the  former  almost  always  displace  the  transverse  colon  downward.  They 
also,  being  retroperitoneal,  carry  it  forward,  while  tumors  of  the  spleen,  although 
they  cause  downward  displacement  of  the  colon,  especially  of  the  splenic  flexure, 
override  it  and  hug  the  anterior  abdominal  wall.  Enlargement  of  the  gall-bladder 
similarly  tends  to  depress  and  to  overlap  the  right  half  of  the  transverse  colon. 

3  and  4.  In  the  postero-lateral  or  external  regions  the  most  common  tumors  are 
those  of  the  kidneys  ;  but  as  they  are  all  retroperitoneal,  they  tend  to  carry  the 
ascending  or  descending  colon  forward  as  well  as  inward.  There  are,  of  course, 
exceptions  to  these  relations, — as,  for  example,  in  the  case  of  a  movable  kidney, 
which  may  be  displaced  so  as  to  carry  the  inner  layer  of  the  mesocolon  forward  and 
inward  and  so  have  the  colon  lying  to  the  outer  side, — but  they  are  rare,  and  the 
anatomical  relations  described  are  of  distinct  diagnostic  value. 

Bowlby  has  formulated  the  anatomical  reasons  for  first  exploring  the  right  lower 
half  of  the  abdomen  in  cases  of  intestinal  obstruction  of  doubtful  origin.  He  says 
that  here  are  to  be  found  :  (a)  the  appendix  ;  (b)  intestinal  diverticula  perhaps 
attached  to  the  umbilicus  or  to  the  neighboring  mesentery  ;  (c)  a  common  site  for 
volvulus, — that  is,  the  caecum  ;  (d  )  a  usual  site  for  the  lodgment  of  an  impacted  gall- 
stone,— that  is,  the  lower  part  of  the  ileum  ;  (e)  a  common  place  for  adhesions  due 
to  caseous  mesenteric  glands  ;  (f)  the  sites  of  right-sided  inguinal,  femoral,  and 
obturator  herniae.  Further,  if  the  obstruction  is  in  the  small  intestine,  it  is  in  the 
right  iliac  fossa  that  undistended  intestine  will  be  found,  and  if  this  can  be  secured 
and  traced  upward,  it  is  the  surest  guide  to  the  seat  of  obstruction. 

A  brief  resume'  of  some  of  those  symptoms  of  abdominal  disease  having  a  definite 
anatomical  basis  will  serve  to  complete  the  consideration  of  this  important  region. 
The  patient  being  supine  with  the  thighs  flexed  : 

1.  Inspection  may  show  :  (a)  an  asymmetrical  swelling  referable  to  a  particular 
organ  or  region  (vide  supra)  ;  (b)  general  distention,  which,  if  due  to  ascites,  will 
cause  bulging  of  the  flanks,  the  fluid  settling  in  the  deep  lateral  recesses  of  the  middle 
zone  ;  if  to  flatulence  or  intestinal  paresis,  a  more  symmetrical  enlargement,  usually 
somewhat  emphasized  in  the  central  region  on  account  of  the  presence  there  of  the 
coils  of  thin  and  easily  dilatable  small  intestine  ;  if  to  pregnancy,  a  rounded  cen- 
tral prominence  in  the  lower  abdomen  ;  (c)  retraction,  which  if  extreme  (scaphoid ), 
might  be  due  to  tuberculous  meningitis,  to  lead  poisoning,  or  to  other  cause  of  great 
emaciation;  ( d )  cedema  of  the  skin,  indicating,  if  local,  an  abscess  underlying 
and  close  to  or  in  the  abdominal  wall  ;  (e)  enlarged  veins  (vide  supra)  ;  ( f)  a  flat- 
tened umbilicus  in  ovarian  or  uterine  growth,  or  a  pouting  umbilicus  in  ascites  or 
tuberculous  peritonitis. 

2.  Palpation  may  disclose  :  (a)  rigidity  of  the  abdominal  wall,  which,  if  in  the 
right  hypochondriac  region,  would  suggest  gall-bladder  disease  ;  if  in  the  epigastric 
region,  stomach  ulcer  or  pancreatitis  ;  if  in  the  right  iliac  fossa,  disease  of  the  appen- 
dix or  caecum.  The  entire  absence  of  rigidity  in  a  case  of  acute  abdominal  pain, 
especially  if  the  latter  is  relieved  by  pressure,  indicates  an  absence  of  inflammation 
and  suggests  irregular  or  spasmodic  peristalsis  (colic)  as  the  cause  ;  (b)  pulsation 
due  to  the  upheaval  of  a  growth  by  vessels  beneath  it,  to  an  aneurismal  swelling,  or, 
in  the  line  of  the  vessel  and  in  thin  persons,  to  the  pulse  in  a  normal  aorta  ;  (e)  tender- 
ness, which  is  sometimes  misleading  on  account  of  the  association  of  visceral  disease 
and  reflected  surface  pain  (vide  supra).  For  example,  the  characteristic  tenderness 
of  appendicitis  is  over  McBurhey's  point,  but  there  may  be  not  only  pain  but  also 


538  HUMAN    ANATOMY. 

tenderness  in  the  umbilical  region.  The  reflected  pain  of  ovaritis  may  be  beneath 
the  costal  margin  or  along  the  crural  branch  of  the  genito-crural  nerve,  where  super- 
ficial tenderness  may  be  elicited,  whereas  the  deep  pain  is  in  the  ovary  itself  (Mayo 
Robson). 

3.  Pain  due  to  abdominal  disease  has  been  described  in  connection  with  the 
various  viscera  (page  1756). 

4.  Much  information  may  be  elicited  by  percussion,  as  the  dulness  in  the  flanks 
(movable  on  change  of  position)  due  to  ascites,  or  the  localized  tympany  due  to 
volvulus  or  to  the  escape  of  gas  from  a  ruptured  appendix  into  a  surrounding  abscess  ; 
or  by  auscultation,  as  the  absence  of  the  usual  intestinal  sounds  when  a  general  peri- 
tonitis has  arrested  peristalsis  ;  or  by  inflation  of  the  stomach,  as  on  distinguishing 
between  a  growth  of  that  viscus  and  a  retroperitoneal  tumor,  or  of  the  colon  (vide 
supra),  which  will  then  lie  below  and  perhaps  behind  an  enlarged  gall-bladder  and 
in  front  and  probably  to  the  inner  side  of  an  enlarged  kidney. 

These  and  other  procedures  are  too  technical  to  be  described  here  in  detail,  but 
are  mentioned  that  they  may  be  associated  with  the  anatomical  relations  on  which 
they  depend. 

It  should  be  noted  that  Treves  and  Keith  state  that  the  ileo-caecal  valve  corre- 
sponds to  the  spino-umbilical  line,  that  the  region  of  the  valve  in  a  normal  person 
is  usually  tender  to  pressure,  and  that  the  root  of  the  appendix  is  placed  more  than 
one  inch  lower  and  perhaps  more  internally.  This  statement  if  confirmed  will  have 
a  most  important  bearing  on  the  value  of  certain  symptoms  thought  to  indicate  the 
existence  of   appendicitis  (page  1683). 


THE  THORACIC   MUSCLES. 

(a)    THE   RECTUS   MUSCLES. 

The  rectus  abdominis,  being  supplied  by  the  lower  intercostal  nerves,  is  evi- 
dently a  derivative  of  the  thoracic  myotomes.  That  portion  of  the  rectus  group 
of  muscles  which  should  be  derived  from  the  upper  thoracic  myotomes  is  normally 
unrepresented,  although  the  occasional  extension  of  the  rectus  abdominis  to  the  upper 
costal  cartilages  or  even  to  the  clavicle  is  probably  an  indication  of  it. 

(*)    THE   OBLIQUUS   MUSCLES. 

1.  Intercostales  externi.  4.    Levatores  costarum. 

2.  Intercostales  interni.  5.   Serratus  posticus  superior. 

3.  Triangularis  sterni.  6.    Serratus  posticus  inferior. 

Here,  again,  a  considerable  portion  of  the  obliqui  and  transversalis  abdominis 
is  derived  from  thoracic  myotomes.  In  addition,  however,  a  number  of  muscles 
belonging  to  the  group  occur  in  connection  with  the  ribs. 

1.    Intercostales  Externi  (Fig.  537). 

Attachments. — The  external  intercostal  muscles  are  eleven  in  number, 
stretching  across  all  the  intercostal  spaces  from  the  lower  border  of  one  rib  to  the 
upper  border  of  the  next.  The  fibres,  which  are  largely  interspersed  with  strands  of 
connective  tissue,  are  directed  downward  and  forward,  and  form  in  each  intercostal 
space  a  sheet  which  extends  in  the  upper  spaces  from  the  tubercle  of  the  rib  to  the 
junction  of  the  rib  with  its  costal  cartilage  and  in  the  lower  spaces  is  continued  upon 
the  cartilages.  The  interval  between  the  medial  borders  of  the  upper  muscles  and 
the  border  of  the  sternum  is  occupied  by  a  sheet  of  connective  tissue  known  as  the 
external  intercostal  fascia  or  anterior  intercostal  aponeuj-osis. 

Nerve-Supply. — By  the  anterior  divisions  (intercostal  nerves)  of  the  thoracic 
nerves. 

Action. — To  draw  the  ribs  upward. 


THE  THORACIC   MUSCLES. 


539 


2.   Intercostales  Interni  (Fig.  537). 

Attachments. — The  internal  intercostals  lie  immediately  beneath  the  external 
and,  like  these,  extend  across  each  of  the  intercostal  spaces.  The  fibres  have  a 
direction  almost  at  right  angles  to  those  of  the  external  intercostals,  being  directed 
obliquely  downward  and  inward  from  the  lower  border  of  one  rib  and  its  costal  car- 
tilage to  the  upper  border  of  the  next.  The  muscle-sheets  so  formed  extend  from 
the  medial  extremity  of  each  intercostal  space  as  far  back  as  the  angles  of  the  ribs, 
becoming  there  continuous  with  an  internal  intercostal  fascia  or  posterior  intercostal 


Fig.  537. 


I  rib        Clavicle 


External  intercostal  fascia 


Internal  intercostal  mus- 
cles, anterior  part  covered 
by  external  fascia 


ternal  intercostal  fascia 


Dissection  of  thoracic 


aponeurosis  which  continues  backward  to  the  tubercles  of  the  ribs.  The  medial  fibres 
of  the  muscles  of  the  lower  two  intercostal  spaces  become  continuous  with  the  upper 
portion  of  the  internal  oblique  muscle  of  the  abdomen. 

Nerve-Supply. — The  anterior  divisions  (intercostal  nerves)  of  the  thoracic 
nerves. 

Action. — To  draw  the  ribs  upward. 

The  Subcostal  Muscles. — Posteriorly  the  fibres  of  the  various  internal  intercostals  do  not 
confine  themselves  to  a  single  intercostal  space,  but  extend  downward  to  the  next  space  below, 
spreading  out  in  the  muscle-sheet  of  that  space.  These  fibres,  which  vary  greatly  in  the  ex- 
tent of  their  development,  form  what  are  termed  the  subcostal  muscles. 


54° 


HUMAN    ANATOMY. 


3.    Triangularis  Sterni  (Fig.  538). 

Attachments. — The  triangularis  sterni  fm.  transversus  thoracis)  forms  a  thin 
sheet  situated  upon  the  posterior  surface  of  the  medial  portion  of  the  anterior 
thoracic  wall.  It  arises  at  one  edge  by  a  series  of  slips  from  the  costal  cartilages  of 
the  second  or  third  to  the  sixth  or  seventh  rib  ;  the  upper  fibres  are  directed  obliquely 
downward  and  medially  and  the  lower  ones  transversely  to  be  inserted  by  a  thin,  flat 
tendon  to  the  sides  of  the  lower  portion  of  the  sternum  and  to  the  xiphoid  process. 
The  lower  fibres  of  the  muscle  are  practically  continuous  with  those  of  the  transversus 
abdominis. 

Nerve-Supply. — By  the  anterior  divisions  (intercostal  nerves)  of  the  second 
or  third  to  the  sixth  or  seventh  thoracic  nerve. 


Fig.  538. 


all  from  behind,  sho 


triangularis  sterni  and  intercostal  muscle 


Action. — To  draw  downward  the  anterior  portions  of  the  ribs  and  so  assist  in 
expiration. 

Relations. — The  internal  mammary  vessels  pass  downward  upon  the  anterior 
surface  of  the  muscle,  separating  it  from  the  fibres  of  the  internal  intercostals. 


4.    Levatores  Costarum  (Fig.  521). 

Attachments. — The  levatores  costarum  form  a  series  of  thin  triangular  mus- 
cles which  arise  from  the  transverse  processes  of  the  seventh  cervical  and  all  the 
thoracic  vertebrae  except  the  twelfth.  They  are  directed  downward  and  laterally  to 
be  inserted  into  the  posterior  surface  of  the  next  succeeding  rib  {levatores  costarum 
breves')  between  the  tubercle  and  the  angle,  some  of  the  fibres  of  the  lower  mus- 
cles passing  over  a  rib  to  be  inserted  into  the  next  but  one  below  {levatores  costarum 
longi). 


THE   THORACIC   MUSCLES. 


54i 


Nerve-Supply.  —  From  the  anterior  divisions  of  the  eighth  cervical  and  the 
first  to  the  eleventh  thoracic  nerves. 

Action. — To  assist  in  drawing  the  ribs  upward.  Acting  from  the  ribs,  they 
will  assist  in  bending  the  spinal  column  backward  and  laterally  towards  the  same  side 
and  in  rotating  it  towards  the  opposite  side. 

5.    Serratus  Posticus  Superior  (Fig.  539). 

Attachments. — The  superior  posterior  serratus  is  a  quadrangular,  flat  muscle 
which  arises  by  a  flat  tendon  from  the  lower  part  of  the  ligamentum  nuchae  and  from 
the  spinous  processes  of  the  seventh  cervical  and  upper  two  or  three  thoracic  ver- 

Fig-  539- 


Trachelo-mastoid 

Internal  pterygoid 

plexus 
Biventer  c 
Scalenus  medius 


VII  cervical  spinous  process 

Complexus 

U\yk^S% Scalenus  posticus 

II  rib 


Vertebral 
aponeurosis 


Semispinalis  dorsi 

Longissimus  dorsi 
Dorsal,  cervical,  and  thoracic  muscles. 

tebrae.  Its  fibres  are  directed  downward  and  laterally  to  be  inserted  into  the  outer 
surface  of  the  second  to  the  fifth  ribs,  lateral  to  their  angles. 

Nerve-Supply. — From  the  anterior  divisions  of  the  first  to  the  fourth  thoracic 
nerves. 

Action. — To  raise  the  ribs  to  which  it  is  attached  and  accordingly  assist  in 
inspiration. 

6.   Serratus  Posticus  Inferior  (Fig.  559). 

Attachments. — The  inferior  posterior  serratus  arises  by  a  broad  but  thin 
tendon  from  the  posterior  layer  of  the  lumbo-dorsal  fascia  from  about  the  level  of 
the  second  lumbar  to  that  of  the  tenth  or  eleventh  thoracic  vertebra.      Its  fibres  are 


542 


HUMAN    ANATOMY. 


directed  upward  and  laterally  and  are  inserted  into  the  outer  surfaces  of  the  lower 
four  ribs. 

Nerve-Supply. — From  the  anterior  divisions  of  the  ninth  to  the  twelfth 
thoracic  nerves. 

Action. — To  draw  the  ribs  to  which  it  is  attached  downward  and  outward. 
The  muscle  contracts  during  inspiration  and  assists  in  this  act  by  counteracting  the 
tendency  which  the  costal  part  of  the  diaphragm  has  to  expend  a  portion  of  its  con- 
traction in  drawing  the  lower  ribs  upward  and  inward. 

Variations. — Variations  in  the  extent  of  their  origin  are  not  uncommon  in  both  the  posterior 
serrati.  Stretching  between  them  there  is  an  aponeurosis,  termed  the  vertebral  aponeurosis, 
which  represents  the  degenerated  portion  of  a  large  muscle-sheet  present  in  the  lower  mam- 
malia, of  which  the  two  posterior  serrati  are  the  persistent  upper  and  lower  portions. 

(c)    THE   HYPOSKELETAL   MUSCLES. 

The  hyposkeletal  group  of  muscles  is  practically  unrepresented  in  the  thoracic 
region. 

THE   CERVICAL    MUSCLES. 

The  Deep  Cervical  Fascia. — The  deep  cervical  fascia  (fascia  colli)  is  a 
well-marked  sheet  of  connective  tissue  which  lies  beneath  the  platysma  and  forms  a 
complete  investment  for  the  neck  region,  giving  off  from  its  deeper  surface  numer- 
ous thin  lamella?  which  surround  the  various  structures  of  the  neck  region.      Pos- 


Fig.  540. 


Sterno-hyoid 
Thyrohyoid 
Omohyoid 
Arytenoid 
Inferior  constrictor 
Carotid  sheath 
Prevertebral  layer 

Platysma 

Sterno-mastoid 

Longus  colli 

Scalenus  amicus 

Scalenus  medius 

Scalenus  posticus 

Trachelo-mastoid 

Levator  anguli  scapulae 

Splenius  colli 

Multindus  spinas 

Semispinalis  cervicis 


Trapezius 
Splenius  capiti 


£^ Thyroid  cartilage 

Vocal  cord 


.Arytenoid  cartilage 
.Pharynx 

.Right  carotid  artery 
Right  internal  jugula 

.Vertebral  artery 
V  cervical  vertebra 


Spinal  cord 


Ligamentum  nucha 


across  neck  at  lower  border  of  fifth  cervical  vertebra. 


teriorly  the  fascia  is  attached  to  the  ligamentum  nucha?  and,  traced  laterally,  it  is 
found  to  divide  into  two  layers  which  enclose  the  trapezius  and,  uniting  again  at  its 
outer  border,  are  continued  forward  over  the  posterior  triangle  of  the  neck  to  the 
lateral  border  of  the  sterno-cleido-mastoid,  where  it  again  divides  into  two  layers  to 
enclose  that  muscle.  The  two  layers  again  unite  at  the  medial  border  of  the  muscle 
and  are  continued  over  the  anterior  triangle  of  the  neck  to  the  median  line,  where 
the  fascia  becomes  continuous  with  that  of  the  opposite  side. 

This  is  the  superficial  layer  of  the  deep  cervical  fascia.      Above  it  is  attached 
to  the  superior  nuchal  line  and  the  mastoid  process,  whence  it  is  continued  along 


THE   CERVICAL   MUSCLES.  543 

the  greater  cornu  and  body  of  the  hyoid  bone,  to  which  it  is  firmly  attached,  and 
where  it  becomes  continuous  above  with  the  deep  fascia  of  the  submental  region. 
This  fascia  covers  in  the  anterior  belly  of  the  digastric,  the  mylo-hyoid,  and  the 
submaxillary  gland,  and  is  attached  above  to  the  lower  border  of  the  mandible, 
where  it  becomes  continuous  with  the  parotideo-masseteric  fascia. 

Below  the  cervical  fascia  ends  over  the  anterior  surface  of  the  clavicle,  and, 
more  medially,  in  the  interval  between  the  lower  portions  of  the  two  sterno-cleido- 
mastoid  muscles,  it  splits  into  two  lamellae,  enclosing  what  is  termed  the  spatium 
suprasternal  or  space  of  Burns.  Both  the  lamellae  pass  down  to  be  attached  to  the 
upper  part  of  the  manubrium  sterni,  so  that  the  suprasternal  space  is  completely 
closed.  It  contains  some  fatty  tissue,  usually  some  lymphatic  nodes,  and  the  lower 
portions  of  the  anterior  jugular  veins  ;  a  diverticulum  from  it  is  prolonged  laterally 
behind  the  insertion  of  the  sterno-cleido-mastoid  along  each  vein  as  it  passes  towards 
its  point  of  union  with  the  subclavian  vein. 

From  the  under  surface  of  this  superficial  layer  a  deeper  or  middle  layer  is 
given  off  at  the  sides  of  the  neck,  and,  passing  forward,  assists  in  the  formation  of 
the  sheath  for  the  carotid  artery  and  internal  jugular  vein,  and  then  divides  to 
enclose  the  omo-hyoideus  and  the  other  depressors  of  the  hyoid  bone,  a  special 
thickening  of  it  extending  downward  from  the  intermediate  tendon  of  the  omo-hyoid 
to  the  clavicle.  Above,  the  middle  layer  is  attached  to  the  greater  cornu  and  body 
of  the  hyoid  bone  along  with  the  superficial  layer,  but  below  it  is  continued  down 
into  the  thorax  in  front  of  the  oesophagus  and  trachea  and  becomes  lost  upon  the 
upper  part  of  the  pericardium. 

A  third  or  deep  layer  of  the  cervical  fascia,  also  termed  the  prevertebral  fascia, 
is  given  off  from  the  under  surface  of  the  superficial  layer  about  on  the  line  of  the 
transverse  processes  of  the  vertebrae.  It  passes  almost  directly  inward  over  the 
scalene  and  hyposkeletal  muscles  of  the  neck,  enclosing  the  cervical  portion  of  the 
sympathetic  trunk  and  contributing  to  the  formation  of  the  carotid  sheath.  It 
unites  with  the  corresponding  layer  of  the  opposite  side  over  the  bodies  of  the 
vertebrae.  This  fascia  is  continued  downward  into  the  thorax  in  front  of  the  verte- 
bral column  and  above  it  extends  to  the  base  of  the  skull.  Towards  the  median 
line  in  its  upper  part  it  is  separated  from  the  pharyngeal  portion  of  the  fascia 
bucco-pharyngea  by  some  loose  areolar  tissue  which  occupies  the  so-called  retro- 
pharyngeal space.  This  is  continued  downward  in  the  loose  tissue  surrounding  the 
oesophagus,  but  is  bounded  laterally  by  the  union  of  the  pharyngeal  and  prevertebral 
fasciae. 

The  carotid  sheath  is  formed  by  the  union  of  portions  from  the  middle  and  deep 
layers  of  the  cervical  fascia.  It  forms  an  investment  for  the  common  carotid  artery,, 
the  internal  jugular  vein,  and  the  vagus  nerve. 


(a)  THE  RECTUS  MUSCLES. 

1.  Sterno-hyoideus.  3.   Sterno-thyroideus. 

2.  Omo-hyoideus.  4.   Thyro-hyoideus. 

5.    Genio-hyoideus. 

1.   Sterno-Hyoideus  (Fig.  541). 

Attachments. — The  sterno-hyoid  is  a  flat  band-like  muscle  situated  in  the 
front  of  the  neck  close  to  the  median  line.  It  arises  from  the  posterior  surface  of 
the  sternal  end  of  the  clavicle  and  from  the  manubrium  sterni  and  passes  upward  to 
be  inserted  into  the  lower  border  of  the  body  of  the  hyoid  bone.  A  mucous  bursa, 
more  constant  in  the  male  than  in  the  female,  usually  occurs  beneath  the  upper 
part  of  the  muscle,  resting  upon  the  hyo-thyroid  membrane  near  the  median  line 
and  immediately  below  the  hyoid  bone. 

Nerve-Supply. — From  the  first,  second,  and  third  cervical  nerves,  through 
the  ansa  hypoglossi. 

Action. — To  draw  the  hyoid  bone  downward. 


544 


HUMAN   ANATOMY. 


Variations. — The  sternohyoid  may  arise  entirely  from  the  clavicle  or  it  may  extend  its  origin 
to  the  cartilage  of  the  first  rib.  It  is  often  divided  transversely  by  a  tendinous  band  which  may 
occur  either  in  its  lower  part  on  a  line  with  the  intermediate  tendon  of  the  omo-h}-oid  or,  more 
rarely,  in  its  upper  part  on  a  level  with  the  insertion  of  the  sterno-thyroid. 

2.   Omo-Hyoideus  (Fig.  541). 

Attachments. — The  omohyoid  is  a  long,  flat  muscle  consisting  of  two  bellies 
united  by  an  intermediate  tendon.  The  inferior  belly  arises  from  the  lateral  portion 
of  the  superior  border  and  the  superior  transverse  ligament  of  the  scapula,  and  is 
directed  forward,  medially,  and  slightly  upward  to  terminate  in  the  intermediate 
tendon.  This  lies  behind  the  clavicular  portion  of  the  sterno-cleido-mastoid,  and  is 
enclosed  by  the  middle  layer  of  the  deep  cervical  fascia,  a  specially  thickened 
portion  of  which  binds  it  down  to  the  posterior  surface  of  the  clavicle  and  to  the 
first  rib.  The  superior  belly  arises  at  the  medial  end  of  the  intermediate  tendon  and 
passes  upward  and  slightly  medially  to  be  i?iserted  into  the  lower  border  of  the  hyoid 
bone,  lateral  to  the  sterno-hyoid. 

Fig.  541. 


Styloid  process 

Styloglossus 
Stylo-pharyngeu; 

Stylo-hyoii 

Digastric,  posterior  belly- 

Rectus  capitis  anticus  major. 

Spleniui 

Sterno-cleido-mastoid 

Levator  anguli  scapulae 
Trapezius' 

Scalenus  medius- 


Scalenus  anticus- 
Omo-hyoid, 
posterior  belly  -^gg 


Orbicularis  oris 
Depressor  anguli 
Depressor  labii 

inferioris 
Hyo-glossus 

Digastric,  anterior  belly 
Mylo-hyoid 
Hyoid  bone 

Inferior  pharyngeal  constrictor 
Thyro-hyoid 


■^ 


Muscles  of  the  neck;  larynx  has  been  drawn  forward. 

Nerve-Supply. — From  the  first,  second,  and  third  cervical  nerves,  through 
the  ansa  hypoglossi. 

Action. — To  draw  downward  the  hyoid  bone.  Acting  from  above,  it  will 
assist  slightly  in  drawing  the  scapula  upward.  This  muscle  may  also  act  as  a 
tensor  of  the  cervical  fascia,  thereby  preventing  undue  pressure  on  the  great  vessels 
of  the  neck. 

Relations. — At  its  attachment  to  the  scapula  the  inferior  belly  is  covered  by 
the  trapezius  and  the  muscle  is  crossed  in  the  middle  part  of  its  course  by  the 
sterno-cleido-mastoid.  The  inferior  belly  is  in  relation  posteriorly  with  the  scalene 
muscles  and  the  roots  of  the  brachial  plexus  and  sometimes  with  the  third  portion  of 
the  subclavian  artery,  the  transversalis  colli  and  suprascapular  arteries,  and  the  supra- 
scapular nerve.  The  superior  belly  crosses  the  common  carotid  artery  and  the 
internal  jugular  vein  at  the  level  of  the  cricoid  cartilage. 


THE   CERVICAL   MUSCLES.  545 

Variations. — The  omohyoid  and  the  sterno-hyoid  are  derived  from  a  muscular  sheet 
•which,  in  the  lower  vertebrates,  invests  the  anterior  portion  of  the  neck  region,  lying  beneath 
the  platysma.  This  sheet  is  represented  in  man  by  the  two  muscles  and  the  middle  layer  of 
the  deep  cervical  fascia.  The  omo-hyoid  or  one  or  other  of  its  bellies  may  be  absent,  or,  on 
the  other  hand,  an  accessory  omo-hyoid  may  be  'developed.  The  superior  belly  not  infre- 
quently fuses  more  or  less  completely  with  the  sterno-hyoid  and  the  inferior  belly  has  some- 
times a  clavicular  origin.  Occasionally  the  band  which  binds  the  intermediate  tendon  to  the 
■clavicle  remains  muscular,  and,  uniting  at  the  tendon  with  the  superior  belly,  produces  what 
has  been  termed  the  cleido-hyoideus. 

3.   Sterno-Thyroideus  (Fig.  541). 

Attachments. — The  sterno-thyroid  is  a  band-like  muscle  which  lies  immedi- 
ately beneath  the  sterno-hyoid.  It  arises  from  the  posterior  surface  of  the  manu- 
brium sterni  and  from  the  cartilages  of  the  first  and  second  ribs,  and  passes  upward 
to  be  inserted  into  the  oblique  line  of  the  thyroid  cartilage. 

Nerve-Supply. — From  the  first,  second,  and  third  cervical  nerves,  through 
the  ansa  hypoglossi. 

Action. — To  draw  the  larynx  downward. 

Relations. — Superficially  the  sterno-thyroid  is  covered  by  the  sterno-hyoid. 
Deeply  it  is  in  relation  with  the  inferior  constrictor  of  the  pharynx,  the  crico- 
thyroid muscle,  the  cricoid  cartilage,  the  lobes  of  the  thyroid  gland,  the  inferior 
thyroid  veins,  the  trachea,  and  the  common  carotid  artery,  and  it  crosses  the  left 
innominate  vein. 

Variations. — The  lower  portion  of  the  muscle  is  often  crossed  by  a  tendinous  intersection, 
and  frequently  some  of  its  fibres  are  continued  directly  into  the  thyro-hyoid  muscle.  The  two 
muscles  of  opposite  sides  are  frequently  united  in  the  median  line,  sometimes  throughout  the 
greater  portion  of  their  length,  at  other  times  merely  by  scattered  bundles. 

4.  Thyro-Hyoideus  (Fig.  541). 

Attachments. — The  thyro-hyoid  lies  beneath  the  upper  portion  of  the  omo- 
hyoid. It  arises  below  from  the  oblique  line  of  the  thyroid  cartilage  and  is 
inserted  above  into  the  lateral  portion  of  the  body  and  into  the  greater  cornu  of  the 
hyoid  bone. 

Nerve-Supply. — From  the  first  and  second  cervical  nerves,  by  fibres  which 
run  with  the  hypoglossal  nerve. 

Action. — To  draw  down  the  hyoid  bone,  or,  if  that  be  fixed,  to  draw  the 
larynx  upward. 

Relations. — As  the  muscle  passes  across  the  hyo-thyroid  membrane  it  covers 
the  superior  laryngeal  nerve  and  artery.  A  bursa,  the  b.  musculi  thyro-hyoidei,  is 
interposed  between  the  muscle  and  the  upper  part  of  the  hyo-thyroid  membrane. 

Variations. — The  thyro-hyoid  is  often  practically  continuous  with  the  sterno-thyroid.  A 
bundle  of  fibres  is  sometimes  to  be  found  passing  either  from  the  lower  border  of  the  hyoid  or 
from  the  thyroid  cartilage  to  the  lobe,  isthmus,  or  pyramid  of  the  thyroid  gland.  It  is  termed 
the  levator  glandules  thyroidece,  under  which  name  are  also  comprised  fibres  which  are  exten- 
sions of  theinferior  constrictor  of  the  pharynx  to  the  thyroid  gland. 

5.  Genio-Hyoideus  (Fig.  497). 

Attachments. — The  genio-hyoid  is  the  superior  portion  of  the  rectus  group 
of  muscles.  It  is  a  rather  narrow  band  which  arises  from  the  lower  genial  tubercle 
of  the  mandible  and  extends  backward  and  downward  to  be  inserted  into  the 
anterior  surface  of  the  body  of  the  hyoid  bone.  It  is  situated  close  to  the  median 
line,  under  cover  of  the  nrylo-hyoid  and  immediately  beneath  the  lower  border  of 
the  genio-glossus. 

Nerve-Supply. — From  the  first  and  second  cervical  nerves,  by  fibres  which 
accompany  the  hypoglossal. 

Action. — If  the  hyoid  bone  be  fixed,  the  genio-hyoid  depresses  the  mandible  ; 
if  the  mandible  be  fixed,  it  draws  the  hyoid  bone  forward  and  upward. 

35 


546 


HUMAN    ANATOMY. 


(b)     THE  OBLIQUUS   MUSCLES. 
i.   Scalenus  anticus.  3.    Scalenus  posticus. 

2.    Scalenus  medius.  4.    Rectus  capitis  lateralis. 

5.    Intertransversales  anteriores. 

1.  Scalenus  Anticus  (Fig.  542). 

Attachments. — The  anterior  scalene  (m.  scalenus  anterior)  arises  by  lour 
tendinous  slips  from  the  anterior  tubercles  of  the  transverse  processes  of  the  third 
to  the  sixth  cervical  vertebrae.  The  four  slips  unite  to  form  a  rather  flat  muscle 
which  extends  downward  and  forward  to  be  inserted  into  the  scalene  tubercle  on  the 
upper  surface  of  the  first  rib. 

Fig.  542. 


Sterno-mastoid,  stump 
Rectus  capitis  anticus  major 


Levator  anguli  scapulae. 


Subscapularis . 


Serratus  magnus 
middle  port' 


Scalenus  anticus' 
Scalenus  med 


Scalenus  posticus 
Rhomboidei 


s  Serratus  magnus,  upper  portion 
Dissection  of  right  side  of  neck,  showing  scalene  and  adjacent  muscles. 

Nerve-Supply. — By  branches  from  the  fourth,  fifth  and  sixth  cervical  nerves. 

Action. — To  bend  the  neck  forward  and  to  the  same  side  and  to  rotate  it  to 
the  opposite  side.  If  the  cervical  vertebrae  be  fixed,  it  will  then  raise  the  first  rib, 
assisting  in  inspiration. 

Relations. — The  anterior  scalenus  lies  in  front  of  the  roots  of  the  brachial 
plexus,  and  near  its  insertion  it  passes  over  the  second  portion  of  the  subclavian  artery 
and  under  the  subclavian  vein.  The  phrenic  nerve  rests  upon  its  anterior  surface 
during   its  course  down  the  neck. 

2.  Scalenus  Medius  (Figs.  541,  542). 

Attachments. — The  middle  scalene  is  situated  behind  the  scalenus  anterior. 
It  arises  by  six  or  seven  tendinous  slips  from  the  transverse  processes  of  the  lower 
six  or  of  all  the  cervical  vertebrae  and  extends  downward  and  outward  to  be  inserted 


THE    CERVICAL    MUSCLES.  547 

into  the  upper  surface  of  the  first  rib,  behind  the  groove  for  the  subclavian  artery. 
Some  fibres  of  the  muscle  may  extend  across  the  first  intercostal  space  to  be  inserted 
into  the  outer  surface  of  the  second  rib. 

Nerve-Supply. — By  branches  from  the  anterior  divisions  of  the  cervical 
nerves. 

Action. — To  bend  the  neck  laterally,  or,  if  the  cervical  vertebrae  be  fixed,  to 
raise  the  first  rib,  assisting  in  inspiration. 

Relations. — As  the  middle  scalene  passes  downward  to  its  insertion  it  diverges 
from  the  scalenus  anterior,  so  that  a  triangular  interval  exists  between  the  two 
muscles  through  which  the  subclavian  artery  and  the  brachial  plexus  pass,  these 
structures  lying  in  front  of  the  insertion  of  the  scalenus  medius. 

3.    Scalenus  Posticus  (Fig.  542). 

Attachments. — The  posterior  scalene  (m.  scalenus  posterior)  lies  immediately 
behind  the  scalenus  medius  and  anterior  to  the  ilio-costalis  cervicis.  It  arises  by 
two  or  three  tendinous  slips  from  the  transverse  processes  of  the  lower  two  or  three 
cervical  vertebrae  and  passes  downward  and  laterally  to  be  inserted  into  the  outer 
surface  of  the  second  rib. 

Nerve-Supply. — From  the  anterior  divisions  of  the  lower  three  cervical 
nerves. 

Action. — To  bend  the  neck  laterally,  or,  if  the  cervical  vertebrae  be  fixed,  to 
raise  the  second  rib. 

Variations  of  the  Scalene  Muscles. — There  is  not  a  little  variation  in  the  extent  of  the 
upper  attachments  of  the  scalene  muscles,  the  origins  being  increased  or,  more  usually,  dimin- 
ished in  number.  A  certain  amount  of  fusion  may  also  occur,  especially  between  the  medius 
and  posterior,  so  that  it  is  not  always  possible  to  distinguish  these  two  muscles.  Occasionally 
the  subclavian  artery  perforates  the  lower  portion  of  the  anterior  scalene,  and  the  portion  so 
separated  may  form  a  distinct  muscle,  the  scalenus  minimus,  which  lies  in  the  interval  between 
the  anterior  and  middle  scalenus,  and  is  attached  above  to  the  transverse  processes  of  the  sixth 
or  the  sixth  and  seventh  cervical  vertebrae  and  below  to  the  upper  surface  of  the  first  rib  and  to 
the  dome  of  the  pleura. 

A  muscle  occasionally  occurs  between  the  upper  part  of  the  pectoralis  major  and  the 
upper  external  intercostals,  from  both  of  which  it  is  separated  by  a  lamella  of  areolar  tissue. 
It  is  termed  the  supracostalis,  and  takes  its  origin  from  the  first  rib  and  sometimes  also  from  the 
fascia  which  covers  the  anterior  scalene,  and  passes  downward  to  be  inserted  into  the  outer 
surface  of  the  third  and  fourth  ribs,  sometimes  attaching  also  to  the  second  rib  and  sometimes 
descending  as  low  as  the  fifth.  It  has  been  regarded  as  an  aberrant  portion  of  the  pectoralis 
major  or  rectus  abdominis,  but  it  seems  to  be  more  probably  a  portion  of  the  obliquus  muscu- 
lature and  is  apparently  related  to  the  scaleni. 

4.    Rectus  Capitis  Lateralis. 

Attachments. — The  rectus  capitis  lateralis  is  a  short,  flat  muscle  which  arises 
from  the  transverse  process  of  the  atlas  and  is  inserted  into  the  inferior  surface  of 
the  jugular  process  of  the  occipital  bone. 

Nerve-Supply. — From  the  suboccipital  nerve. 

Action. — To  bend  the  head  laterally. 

5.    Intertransversales  Anteriores. 

Attachments. — The  anterior  intertransversales  are  a  series  of  small  muscles 
which  pass  between  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical 
vertebrae. 

Nerve-Supply. — From  the  anterior  divisions  of  the  cervical  nerves. 

Action. — To  bend  the  head  laterally. 

The  Triangles  of  the  Neck. — The  sterno-cleido-mastoid  muscle,  on  account 
of  its  position  somewhat  superficial  to  the  remaining  muscles  of  the  neck,  serves  to 
divide  that  region  into  two  triangular  areas  which  are  of  considerable  importance 
from  the  stand-point  of  topographic  anatomy. 


5-1-S. 


HUMAN    ANATOMY. 


Fig.  543. 


belly 


anterior  belly 


One  of  these  triangles,  the  posterior,  is  bounded  by  the  lateral  border  of 
the  upper  part  of  the  trapezius  behind  and  by  the  lateral  border  of  the  sterno- 
cleido-mastoid  *n  front,  and  has  for  its  base  the  upper  border  of  the  clavicle 
between  the  insertion  of  these  two  muscles.  The  anterior  triangle  is  reversed  with 
respect  to  the  posterior  one,  having  its  apex  downward  and  its  base  above.  Its  lateral 
boundary  is  the  medial  border  of  the  stemo-cleido-mastoid,  its  medial  boundary  is 
the  median  line  of    the  neck,   and  its  base  is  formed  by  the  lower  border  of  the 

mandible  and  a  line 
extending  horizontally 
backward  from  the  an- 
gle of  the  mandible  to 
the  mastoid  process. 

Each  of  these  two 
triangles  is  again  di- 
visible into  subordinate 
triangles  by  the  mus- 
cles which  cross  them. 
Thus  the  posterior  tri- 
angle is  divided  by  the 
inferior  belly  of  the  omo- 
hyoid, which  crosses  it 
obliquely,  into  an  upper 
or  occipital  triangle  and 
a  lower  or  subclavian 
triangle,  while  the  an- 
terior triangle  is  divisi- 
ble into  three  triangles 
by  the  superior  belly  of 
the  omo-hyoid  and  the 
posterior  belly  of  the 
digastric.  The  lowest  of 
these  triangles,  termed 
the  muscular  or  inferior 
carotid  triangle,  has  its 
base  along  the  median 
line  and  its  apex  directed  laterally,  its  sides  being  formed  by  the  sterno-cleido- 
mastoid  below  and  the  superior  belly  of  the  omo-hyoid  above.  The  superior  carotid 
triangle  has  its  base  along  the  upper  part  of  the  sterno-cleido-mastoid  and  its  apex 
directed  medially  ;  its  sides  are  formed  by  the  superior  belly  of  the  omo-hyoid  below 
and  the  posterior  belly  of  the  digastric  above.  Finally,  the  submaxillary  or  digastric 
triangle  is  the  basal  portion  of  the  original  anterior  triangle,  and  is  bounded  below 
by  the  two  bellies  of  the  digastric  muscle  and  above  by  the  line  of  the  lower  border 
of  the  mandible  and  its  continuation  posteriorly  to  the  sterno-mastoid  muscle. 


anterior  belly 


Omo-hyoid,  posterior  belly 


Triangles  of  neck. 


(c)   THE   HYPOSKELETAL   MUSCLES. 

1.    Longus  colli.  2.    Rectus  capitis  anticus  major. 

3.    Rectus  capitis  anticus  minor. 

1.   Longus  Colli  (Fig.  544). 

Attachments. — The  longus  colli  forms  an  elongated  triangular  band  whose 
base  is  towards  the  median  line  and  the  wide-angled  apex  directed  laterally.  It  may 
be  regarded  as  consisting  of  three  portions.  The  medial  portio?i  consists  of  fibres 
which  arise  from  the  bodies  of  the  upper  three  thoracic  and  lower  two  cervical 
vertebras,  forming  a  muscular  band  which  is  inserted  into  the  bodies  of  the  three  or 
four  upper  cervical  vertebras,  the  slip  to  the  atlas  being  inserted  into  its  anterior 
tubercle.  From  the  lower  part  of  the  medial  portion  slips  are  given  off  which  con- 
stitute the  inferior  oblique  portion,  and  are  inserted  into  the  transverse  processes  of 
the  fifth  and  sixth,  and  sometimes  also  of  the  fourth  and  seventh,  cervical  vertebrae. 


THE   CERVICAL   MUSCLES. 


549 


And,  finally,  the  superior  oblique  portion  is  formed  by  slips  arising  from  the  trans- 
verse processes  of  the  sixth  to  the  third  cervical  vertebrae  and  joining  the  upper  part 
of  the  medial  portion. 

Nerve-Supply. — From  the  anterior  divisions  of  the  second,  third,  and  fourth 
cervical  nerves. 

Action. — To  bend  the  neck  ventrally  and  laterally. 

Fig.  544. 


Longus  colli,  superior  oblique 
portion 


Rectus  capitis  anticus  major 


Anterior  tubercle  of  atlas 


Longus  colli,  median  portion- 


Lougus  colli,  inferior  oblique 
portion 


_VII  cervical  vertebra 


I  thoracic  vertebra 


Deep  dissection  of  neck,  showing  prevertebral  muscles. 


2.   Rectus  Capitis  Anticus  Major  (Fig.  544). 

Attachments. — The  rectus  capitis  anticus  major  (m.  longus  capitis)  partly 
covers  the  upper  part  of  the  longus  colli.  It  arises  by  four  tendinous  slips  from  the 
transverse  processes  of  the  third  to  the  sixth  cervical  vertebras,  and  passes  directly 
upward  to  be  inserted  into  the  basilar  portion  of  the  occipital  bone,  lateral  to  the 
pharyngeal  tubercle. 

Nerve-Supply. — From  the  anterior  divisions  of  the  second,  third,  and  fourth 
cervical  nerves. 

Action. — To  flex  the  head  and  rotate  it  slightly  towards  the  opposite  side. 


550  HUMAN    ANATOMY. 

3.   Rectus  Capitis  Anticus  Minor. 

Attachments. — The  rectus  capitis  anticus  minor  (m.  rectus  capitis  anterior) 
is  a  short,  flat  muscle  which  arises  from  the  anterior  surface  of  the  lateral  mass  of 
the  atlas  and  is  directed  obliquely  upward  and  medially  to  be  inserted  into  the 
basilar  portion  of  the  occipital  bone,  immediately  behind  the  insertion  of  the  longus 
capitis. 

Nerve-Supply. — By  the  first  cervical  (suboccipital)  nerve. 

Action. — To  flex  the  head. 

PRACTICAL   CONSIDERATIONS  :    THE  NECK. 

The  skin  of  the  front  and  sides  of  the  neck  is  thin  and  movable.  The  platysma 
myoides  is  closely  connected  to  it  by  the  thin  superficial  fascia.  The  edges  of  wounds 
transverse  to  the  fibres  of  that  muscle  are  therefore  often  inverted. 

In  the  region  of  the  nape  of  the  neck  the  skin  is  thicker  and  much  more  closely 
adherent  to  the  deep  fascia;  it  is  poorly  supplied  with  blood  ;  hair-follicles  and 
sebaceous  glands  are  numerous  ;  it  is  frequently  exposed  to  minor  traumatisms  and 
to  changes  of  surface  heat,  and  is  often  at  a  lower  temperature  than  the  parts 
immediately  above,  which  are  covered  with  hair,  or  than  those  directly  below,  which 
are  protected  by  clothing;  the  nerve-supply  is  abundant.  For  these  reasons  furun- 
cles and  carbuncles  are  of  common  occurrence  and  are  apt  to  be  exceptionally  painful. 

The  subcutaneous  ecchymosis  which  follows  fracture  through  the  posterior  cerebral 
fossa  first  appears  anterior  to  the  tip  of  the  mastoid  and  spreads  upward  and  back- 
ward on  a  curved  line  ;  the  blood  is  prevented  from  reaching  the  surface  more 
directly  by  the  cervical  fascia,  and  therefore  goes  laterally  in  the  intermuscular 
spaces,  being  directed  towards  the  mastoid  tip  by  the  posterior  auricular  artery. 

In  the  submaxillary  region  the  looseness  of  the  skin  makes  it  available  for 
plastic  operations  on  the  cheeks  and  mouth.  In  the  submental  region  the  accu- 
mulation of  subcutaneous  adipose  tissue  seen  in  stout  persons  gives  rise  to  the 
so-called  "  double  chin."  In  both  the  latter  regions  (covered  by  the  beard  in  men) 
furuncles  and  sebaceous  cysts  are  common. 

The  surgical  relations  of  the  fascia  of  the  neck  can  best  be  understood  by  refer- 
ence to  a  horizontal  section  at  the  level  of  the  seventh  cervical  vertebra  (Fig.  545). 

The  superficial  layer  (a,  a')  will  then  be  seen  to  envelop  the  entire  neck.  Pos- 
teriorly it  is  attached  between  the  external  occipital  protuberance  and  the  seventh 
cervical  spinous  process  to  the  ligamentum  nucha;  ;  anteriorly  it  is  interlaced  with 
the  same  layer  of  fascia  from  the  other  side  of  the  neck  ;  superiorly  between  the 
external  occipital  protuberance  and  the  middle  of  the  chin  it  is  attached  on  each  side 
to  the  superior  curved  line  of  the  occipital  bone,  the  mastoid,  the  zygoma,  and  the 
lower  jaw  ;  inferiorly  between  the  seventh  spine  and  the  suprasternal  notch  it  is 
attached  on  each  side  to  the  spine  of  the  scapula,  the  acromion,  the  clavicle,  and  the 
upper  edge  of  the  sternum.  After  splitting  to  enclose  the  trapezius  and  covering  in 
the  posterior  triangle,  this  fascia  divides  again  at  the  hinder  border  of  the  sterno- 
cleido-mastoid.  The  superficial  layer  continues  over  the  surface  of  that  muscle, 
covers  in  the  anterior  triangle,  and  blends  with  its  fellow  of  the  opposite  side. 

From  its  under  surface,  after  reaching  the  sterno-mastoid,  the  deeper  layer  gives 
off  from  behind  forward  (b)  a  process — prevertebral  fascia — which  begins  near  the 
posterior  border  of  the  sterno-mastoid,  passes  in  front  of  the  scalenus  anticus,  the 
phrenic  nerve,  the  sympathetic  nerve,  and  the  longus  colli  muscle,  and  behind  the 
great  vessels,  the  pneumogastric  nerve,  and  the  oesophagus  to  the  front  of  the  base 
of  the  skull  and  the  bodies  of  the  cervical  vertebra.  In  the  mid-line  this  descends 
behind  the  gullet  into  the  thorax.  At  the  sides  of  the  neck  it  helps  to  form  the  pos- 
terior wall  of  the  carotid  sheath,  spreads  out  over  the  scalene  muscles,  and  passes 
down  in  front  of  the  subclavian  vessels  and  the  brachial  plexus,  until  it  dips  beneath 
the  clavicle.  It  is  then  applied  closely  to  the  under  surface  of  the  costo-coracoid 
membrane  and  splits  to  become  the  sheath  of  the  axillary  vessels.  A  second  process 
(c),  leaving  the  sterno-mastoid  more  anteriorly,  aids  in  forming  the  anterior  wall  of 
the  carotid  sheath,  and  joins  the  preceding  layer  just  internal  to  the  vessels.      It  is 


PRACTICAL    CONSIDERATIONS  :    THE  NECK. 


55i 


usually  described  as  part  of  (d)  a  process — tracheal — which  leaves  the  sterno-mastoid 
nearer  its  anterior  border,  and,  running  behind  the  sterno-hyoid  and  sterno-thyroid 
muscles,  descends  in  front  of  the  trachea  and  the  thyroid  gland  to  become  connected 
with  the  fibrous  layer  of  the  pericardium. 

The  adhesion  of  the  deep  fascia  to  the  blood-vessels,  by  preventing  contraction 
and  collapse  of  their  walls,  favors  hemorrhage  and  increases  the  risk  of  the  entrance 
of  air  into  divided  veins. 

Tracing  the  layers  of  fascia  vertically  and  from  the  surface  inward,  it  will  be 
useful  to  remember  that  the  superficial  layer  (a,  Fig.  546)  passes  to  the  top  of  the 
sternum  (sending  a  slip  to  be  attached  to  its  posterior  border)  and  to  the  clavicle. 
The  second  layer  (6)  descends  behind  the  depressors  and  in  front  of  the  thyroid 
gland  and  trachea  to  merge  into  the  pericardium,  and  farther  out  to  form  a  sheath  for 
the  omo-hyoid  and  for  the  subclavian  vein,  and  is  lost  in  the  sheath  of  the  subclavius. 


Fig.  545. 


Sp 

Thyroid  bod 

CEsophagu 
Carotid  artery. 


Internal  jugular  vein 
Vertebral  vessels 


Sp: 

Extern,  jugular 


Spinal  nerves,  cut 
obliquely 


Spinal  cord 

Trapezius  muscle. 

Vertebral  spin 


Fusion  of  superficial  layer  in  mid-line 


ace  3b 


Fascia  covering 
posterior  triangle 


Fascia  passing 
beneath  trapezius 


Ligamentum  nuchas 
ical  vertebra. 


This  relation  of  the  omo-hyoid  is  of  value  in  enabling  that  muscle,  when  the 
hyoid  is  fixed,  to  increase  the  tension  of  this  layer  of  fascia,  and  thus  hold  open  and 
prevent  atmospheric  pressure  upon  the  walls  of  the  vessels — especially  the  veins — 
and  the  soft  parts  (including  the  pulmonary  apices)  at  the  base  of  the  neck. 
Hilton  uses  this  function  of  the  muscle — which  connects  it  with  the  act  of  respiration — 
to  illustrate  the  precision  of  the  nerve-supply  to  muscles  generally.  The  omo-hyoid 
arises  in  close  proximity  to  the  suprascapular  notch,  and  therefore  to  the  supra- 
scapular nerve.  Yet  it  never  receives  a  filament  from  that  nerve,  but  is  supplied 
by  the  cervical  nerves  to  bring  it  in  relation  to  the  movements  of  the  other  neck 
muscles,  is  connected  with  the  hypoglossal  to  associate  it  with  the  movements  of  the 
tongue,  and  with  the  pneumogastric  to  enable  it  to  act  as  above  described  during 
forced  respiration,  when  the  rush  of  air  into  the  thorax  might  otherwise  cause  harmful 
increase  of  atmospheric  pressure  in  the  lower  cervical  or  supraclavicular  region. 

The  pretracheal  layer  is  found  between  the  depressors  and  the  trachea  passing 
down  to  its  pericardial  insertion.  Hilton  thus  explains  this  insertion  :  ' '  The  peri- 
cardium is  most  intimately  blended  with  the  diaphragm,  distinctly  identified  with  it, 
and  capable  of  being  acted  upon  by  it  at  all  times.  It  is  also  attached  above  to  the 
deep  cervical  fascia.  It  is  thus  kept  tense  by  the  action  of  the  respiratory  muscles 
in  the  neck  attached  to  the  cervical  fascia  above  and  the  diaphragm  attached  to  it 


552 


HUMAN    ANATOMY. 


below  ;  or,  in  other  words,  these  two  muscular  forces  are  acting  on  the  interposed 
pericardium  in  opposite  directions,  and  so  render  it  tense  and  resisting.  And  the 
special  object,  no  doubt,  of  this  piece  of  anatomy  is  that  during  a  full  inspiration, 
when  the  lungs  are  distended  with  air  and  the  right  side  of  the  heart  gorged  with 
blood  from  a  suspension  of  respiration,  the  heart  should  not  be  encroached  upon  by- 
the  surrounding  lungs." 

The  prevertebral  layer  (V,  Fig.  546)  lying  between  the  oesophagus  and  spine 
passes  in  the  mid-line  directly  into  the  posterior  mediastinum;  laterally — beyond  the 
scalenus  anticus — it  aids  in  forming  the  sheath  of  the  subclavian  vessels  and  accom- 
panies them  into  the  axilla. 

Another  way  of  elucidating  the  practical  effect  of  the  somewhat  complex  dis- 
tribution of  the  cervical  fascia  is  to  regard  the  three  chief  layers — superficial,  middle, 
and  deep — as  dividing  the  neck  into  four  anatomical  spaces  (Tillaux). 

1.  Subcutaneous  (Space  I,  Fig.  545)  :  between  the  skin  and  the  superficial 
layer.  The  most  important  structure  in  this  space  is  the  external  jugular  vein,  which 
perforates  the  fascia  just  above  the  middle  of  the  clavicle. 

2.  Intra-aponeurotic   (Space   2,  Fig.  546)  :    between  the  superficial  and  mid- 

dle (sterno-clavicular)  layers.     This 
Fig.  546.  space  does  not  exist  in  fact  at  the 

summit  of  the  neck  where  the  two 
layers  are  one,  but  at  the  base  its- 
depth  is  equal  to  the  thickness  of 
the  sternum.  It  may  be  continuous 
with  the  space  left  at  the  top  of  the 
sternum  between  the  two  leaflets  of 
the  superficial  layer  attached  to  the 
anterior  and  posterior  borders  of  the 
sternum,  — Griiber's  "  suprasternal 
intra-aponeurotic  space,"  "  Burns's 
space."  It  contains  fat  and  lym- 
phatic glands,  the  sternal  head  of 
the  sterno-mastoid,  and  the  anterior 
jugular  veins.  It  is  not  infrequently 
the  seat  of  abscess. 

3.  Visceral  (Space  3  =  3a  +  3$, 
Fig-  545 ) :  between  the  pretracheal 
and  prevertebral  layers.  This  in- 
cludes all  the  principal  structures  of 
the  neck.  As  it  communicates  di- 
rectly with  the  thorax  and  axilla, 
suppuration  may  travel  in  those  di- 
rections. It  is  divided  into  minor 
spaces  (3a  and  3^)  by  a  layer  of  fascia  coming  from  the  under  surface  of  the  sterno- 
mastoid  muscle  and  by  the  bucco-pharyngeal  fascia,  a  thin  layer  that  comes  off  from 
the  prevertebral  fascia  where  it  leaves  the  carotid  sheath,  and  which  lines  the 
constrictors  of  the  pharynx,  leaving  between  it  and  the  layer  applied  to  the  spinal 
column  a  small  but  easily  distended  space — retropharyngeal — in  which  infection 
from  pharyngeal  lesions  occasionally  occurs. 

4.  Retrovisceral  (Space  4,  Fig.  546):  the  space  between  the  prevertebral  fascia 
and  spinal  column,  including  the  longus  colli  and  rectus  capitis  anticus,  the  sympa- 
thetic nerve,  etc. 

It  is  obvious  in  a  general  way  that  all  infections  beneath  the  middle  layer  of 
fascia  are  more  likely  to  be  serious  than  those  superficial  to  it. 

But  to  summarize  in  a  little  more  detail  the  practical  relations  of  the  cervical 
fascia,  we  may  conclude  that  superficial  to  the  outer  layer  (a,  Fig.  545)  there  might 
occur  from  traumatism  a  wound  of  the  external  jugular,  or  from  infection  a  spread- 
ing cellulitis.  The  space  is  the  seat  of  superficial  phlegmons,  which  tend  to  spread 
under  the  skin  only  (Space  1,  Fig.  545),  and,  in  the  absence  of  tension,  are  unat- 
tended by  throbbing  pain  or  marked  constitutional  symptoms. 


Diagram  showing  relations  of  cervical  fascia  in  longitudinal 


PRACTICAL    CONSIDERATIONS  :    THE    NECK. 


553 


The  space  between  cand  b  (3^,  Fig.  545)  is  occupied  only  by  the  great  vessels 
and  the  pneumogastric.  Infection  there — i.e. ,  within  the  sheath — may  mean  de- 
scending thrombosis  from  original  infection  of  a  cerebral  sinus,  or  may  have  spread 
directly  through  the  sheath  from  infected  tracts  of  cellular  tissue  outside.  Behind 
b,  Fig.  545  (retrovisceral  space),  suppuration  is  not  uncommon  as  a  result  of  verte- 
bral disease.  Direct  infection  through  the  pharyngeal  wall  usually  involves  the 
retropharyngeal  space.  In  either  case  dysphagia  and  dyspncea  are  usual  for  obvious 
reasons. 

Between  b  and  c,  Fig.  546  (pretracheal  and  prevertebral  layers),  abscess  would 
spread  most  readily  along  the  line  of  the  trachea  and  in  front  of  the  vessels  into  the 
superior  mediastinum. 

In  the  intra-aponeurotic  space  (Space  2,  Fig.  546)  an  abscess  would  probably 
point  superficially,  as  the  fascia  in  front  of  it  is  very  thin.  If  it  were  influenced  by 
gravity,  however,  it  would  follow  the  hyoid  depressors  and  their  intermuscular  spaces 
to  the  root  of  the  neck,  and  might  enter  the  superior  mediastinum. 

Two  additional  and  important  spaces  are  formed  by  extensions  or  reduplications 
of  the  cervical  fascia.  That  portion  of  the  superficial  layer  above  the  level  of  the 
angle  of  the  inferior  maxilla,  and  passing  from  that  bone  to  the  zygoma,  constitutes 
the  parotid  fascia,  which  on  the  surface  is  continuous  with  that  over  the  masseter, 
while  beneath  it  becomes  thickened  to  constitute  the  stylo-maxillary  ligament,  sep- 
arating the  parotid  and  submaxillary  glands  and  resisting  overaction  of  the  external 
pterygoid  muscle.  As  the  outer  fascial  investment  of 
.the  gland  is  dense  and  resistant,  and  as  internal  to  this 
ligament  the  inner  layer  is  thinner  and  weaker  than 
elsewhere, — a  positive  gap  existing  between  the  styloid 
process  and  the  pterygoid  muscle, — suppuration  within 
the  gland  may  result  in  extension  to  the  retropharyngeal 
region.  It  may  follow  the  external  carotid  downward  to 
the  chest,  or,  as  the  fascial  investment  is  also  incomplete 
above,  may  extend  upward  to  the  base  of  the  skull,  or 
even  into  the  skull.      It  sometimes  follows  the  branches  /  /  /^r- H>'old  boni 

of  the  third  division  of  the  fifth  nerve  through  the  fora-  '  /  Outer  layer  of  fascia 

men  Ovale  into  the  cranium.  /     Inner  layer  of  fascia 

The  second  space  alluded  to  is  formed  by  that  por-        submaxillary  gland 
tion  of  the    superficial   layer    between    the    jaw   and  the     ma,K°^ie^hU^rektionsofrc°eSr- 
hyoid  bone  and  in  front  of  the  stylo-mandibular  ligament,      vicai  fascia. 
As  it  passes  forward  from  the  latter  structure  it  splits  and 

envelops  the  submaxillary  gland,  and  becomes  firmly  attached  below  to  the  hyoid 
and  above  to  the  lower  jaw  externally  and  the  under  surface  of  the  mylo-hyoid 
muscle  internally  (Fig.  547).  Infection — "  Ludwig's  angina,"  "submaxillary 
phlegmon,"  "deep  cervical  phlegmon" — in  this  space,  which  contains  the  salivary 
gland  and  its  attendant  lymphatics,  is  rendered  exceptionally  grave  by  the  density 
of  these  fascial  layers.  The  infecting  organisms — usually  streptococci — may  gain 
access  through  a  lesion  of  the  floor  of  the  mouth  near  the  frenum,  or  from  an  alveo- 
lar abscess,  or  by  way  of  the  digastric  muscle  from  a  focus  of  disease  in  the  middle 
ear.  Once  established,  they,  with  their  secondary  products,  are  forced  along  the 
lines  of  least  resistance — by  the  side  of  the  mylo-hyoid  usually — towards  the  base 
of  the  tongue,  involving  the  cellular  tissue  about  the  glottis  and  along  the  vessels 
that  perforate  the  fascia,  causing  infective  venous  thrombosis  and  involving  the 
deeper  planes  of  connective  tissue.  Under  the  latter  circumstances,  if  tension  is  not 
promptly  relieved,  large  vessels  may  be  opened  by  the  necrotic  process.  Jacobson 
long  ago  called  attention  to  the  interesting  fact  that  communications  between  ab- 
scesses and  deep  vessels  have  usually  taken  place  beneath  the  cervical  fascia  and 
the  fascia  lata,  two  of  the  strongest  fascia?  of  the  body. 

Tumors  of  the  neck  may  originate  in  any  of  the  diverse  structures  of  that 
region.  It  may  be  mentioned  here  that  their  situation  above  or  beneath  the  cervical 
fascia  is  an  important  factor  in  determining  their  mobility,  and  hence  the  probable 
ease  or  difficulty  of  their  removal.  In  the  latter  situation  associated  pressure- 
symptoms  are  common. 


554  HUMAN    ANATOMY. 

Lipoma  is  frequent  ;  fibroma  and  enchondroma  are  occasionally  seen  in  the 
region  of  the  ligamentum  nuchae  ;  primary  carcinoma  is  rare. 

Congenital  cysts — "  hydroceles" — of  the  neck  are  found  beneath  the  deep  fascia, 
usually  in  the  anterior  triangle  and  below  the  level  of  the  hyoid.  They  may  arise 
from  dilatation  of  the  lymphatic  vessels,  or,  as  Sutton  suggests,  they  may  originate, 
as  do  the  cervical  air-sacs  in  some  monkeys,  especially  the  chimpanzees,  by  the 
formation  of  diverticula  from  the  laryngeal  mucous  membrane.  In  any  event,  they 
ramify  in  the  various  intermuscular  spaces,  and  their  complete  removal  is  therefore 
very  difficult. 

Branchial  cysts  and  dermoids  are  not  infrequent.  They  should  be  studied  in 
connection  with  the  embryology  of  the  region. 

Congenital  tumor  of  the  sterno-mastoid  is  a  condition  resulting  from  either  rup- 
ture of  muscular  fibres  or  bruising  of  the  muscle  against  the  under  surface  of  the 
symphysis  during  delivery.      It  may  be  a  cause  of  torticollis. 

Torticollis — "wry-neck" — maybe  due  to  spasm  of  the  sterno-mastoid  either 
alone  or  associated  with  a  similar  condition  of  the  trapezius,  especially  the  clavicular 
portion,  and  often  of  the  scaleni  or  the  complexus.  Later  there  is  apt  to  be  second- 
ary contraction  of  the  deep  fascia  and  of  the  posterior  cervical  muscles.  Tenotomy 
of  the  muscle  for  the  relief  of  this  affection  is  performed  at  a  level  just  above  its 
sternal  and  clavicular  insertion.  The  subcutaneous  method  has  been  largely  dis- 
carded in  favor  of  division  through  an  open  wound.  By  the  former  plan,  not  only 
were  the  anterior,  and  sometimes  also  the  external,  jugular  veins  endangered,  but  the 
cervical  space  described  as  ' '  visceral' '  was  occasionally  opened,  and,  if  infection 
occurred,  with  fatal  results  from  septic  cellulitis  or  pleurisy. 

Section  of  the  spinal  accessory  nerve  may  be  resorted  to  when  the  spasm  is 
limited  to  the  sterno-mastoid  and  trapezius,  or  of  the  posterior  primary  divisions 
of  the  first,  second,  and  third  cervical  nerves  when  the  posterior  muscles  are  involved. 

Landmarks. — Athough  but  few  organs  belong  exclusively  to  the  neck,  a  great 
many  structures  of  much  diversity,  and  connecting  the  trunk  and  head,  pass  through 
it.  The  "landmarks"  will  therefore  be  found  in  relation  to  different  systems, — vas- 
cular, nervous,  etc., — those  given  here  referring  chiefly  to  the  muscles  and  their  effect 
upon  surface  form. 

The  mid-line  posteriorly  has  already  been  described  in  its  relation  to  the  spines 
of  the  cervical  vertebra;  (pages  146-148). 

On  the  sides  of  the  neck  the  platysma,  when  in  action,  produces  inconspicuous 
wrinkling  of  the  skin.  Its  fibres  are  in  a  line  from  the  chin  to  the  shoulder.  The 
sterno-mastoid,  running  obliquely  from  the  skull  to  the  sternum  and  clavicle,  divides 
each  lateral  half  of  the  neck  into  two  triangles.  The  anterior  of  these  is  bounded 
above  by  the  lower  border  of  the  inferior  maxilla  and  a  line  extending  from  the  angle 
of  that  bone  to  the  mastoid  process  ;  anteriorly  by  a  straight  line  between  the  middle 
of  the  chin  and  the  sternum  ;  posteriorly  by  the  anterior  border  of  the  sterno-mas- 
toid. Its  apex  is  at  the  middle  of  the  upper  edge  of  the  manubrium.  The  posterior 
triangle  is  bounded  posteriorly  by  the  anterior  edge  of  the  trapezius,  the  hinder 
edge  of  the  sterno-mastoid  in  front,  and  the  middle  of  the  clavicle  below.  Its  apex 
is  just  behind  the  mastoid  process. 

It  will  be  seen  that  by  this — the  usual — description  those  structures  lying  imme- 
diately beneath  the  sterno-mastoid  would  be  excluded  from  both  triangles.  It  is  cus- 
tomary, however,  to  include  the  common  carotid  and  internal  jugular  vein  in  the 
anterior  triangle,  although  they  are  both  under  cover  of  the  anterior  edge  of  the 
sterno-mastoid. 

The  anterior  triangle  is  divided  into  three — the  superior  carotid,  the  inferior 
carotid,  and  the  submaxillary — by  the  digastric  muscle  and  the  anterior  belly  of  the 
omo-hyoid.  The  posterior  belly  of  the  omo-hyoid  divides  the  posterior  triangle  into 
a  lower  or  subclavian  and  an  upper  or  occipital  triangle.  The  structures  included 
within  these  various  triangles  will  be  described  in  connection  with  the  vessels, 
nerves,  etc. 

The  dividing  line  between  the  two  main  triangles — the  sterno-mastoid — -can  be 
both  seen  and  felt  if,  with  the  mouth  closed,  the  chin  is  depressed  and  the  skull  is 
rotated  towards  the  opposite  shoulder.      The  thick,  prominent,  rounded  anterior  bor- 


PRACTICAL    CONSIDERATIONS  :    THE    NECK. 


555 


der  can  then  be  made  out  from  mastoid  to  sternum,  but  is  more  accentuated  below, 
where  the  sternal  head  is  salient  and  sharply  denned.  This  thin  posterior  border  may 
be  felt  vaguely  at  the  upper  part,  but  cannot  be  seen.  At  about  the  lower  third  it 
becomes  visible  and  is  continued  into  the  broader  and  flatter  clavicular  head.  The 
middle  of  the  muscle  is  seen  throughout  most  of  its  length  as  a  fleshy,  rounded 
elevation.  Over  it,  and  usually  plainly  visible,  is  the  external  jugular  vein,  running 
between  the  platysma  and  the  deep  fascia  in  a  line  from  the  angle  of  the  jaw  to  the 
centre  of  the  clavicle.  In  rest  the  anterior  border  is  still  visible.  The  position  of 
the  muscle  on  the  side  towards  which  the  head  is  turned  is  indicated  by  a  slight 
furrow  in  the  skin.  The  muscles  partly  overlapped  by  the  sterno-mastoid  are,  from 
above  downward,  the  splenius,  levator  scapula?,  digastric,  omo-hyoid,  sterno-thyroid, 
and  sterno-hyoid. 

Fig.  548. 


Submaxillary  gland 


Digastric,  anterior  belly 
Hyoid  bone 


supraclavicular  fossa 


Suprasternal  notch 
(jugular  fossa) 


Omo-hyoid.  posterior  belly 
Supraclavicular  fossa 
Infraclavicular  fossa 


Surface  markings  of  neck,  from  living  subject. 


The  interval  between  the  sternal  and  clavicular  heads  of  the  muscle  is  indicated 
by  a  slight  depression, — the  lesser  supraclavicular  fossa, — and  is  bounded  below  by 
the  upper  edge  of  the  inner  third  of  the  clavicle.  Beneath  it,  about  on  a  line  with 
the  sternal  end  of  the  clavicle,  lie  on  the  right  side  the  bifurcation  of  the  innominate 
artery  and  on  the  left  the  common  carotid  artery. 

Between  the  outer  edge  of  the  clavicular  head  of  the  sterno-mastoid  and  the 
base  of  the  anterior  edge  of  the  trapezius  is  a  broad,  flat  depression, — the  supracla- 
vicular fossa, — which  is  made  very  evident  by  shrugging  the  shoulders,  and  across 
which  the  posterior  belly  of  the  omo-hyoid  runs  and  can  often  be  seen  and  felt  in 
thin  persons,  especially  during  inspiration  or  when  the  head  is  turned  towards  the 
opposite  side  (Fig.  548).  The  line  of  the  muscle  is  from  the  suprascapular  notch, 
slightly  ascending  to  the  anterior  margin  of  the  sterno-mastoid  at  a  level  with  the 
cricoid  cartilage  and  then  rapidly  ascending  to  the  body  of  the  hyoid.     Below  its 


556  HUMAN    ANATOMY. 

posterior  belly  run  the  brachial  plexus,  which  can  often  be  felt  and  sometimes  seen, 
and,  near  the  clavicle,  the  subclavian  artery. 

Farther  out  the  anterior  border  of  the  trapezius  may  be  seen  passing  from  the 
occiput  to  its  insertion  at  the  outer  end  of  the  middle  third  of  the  clavicle.  The 
triangular  interval  between  it  and  the  posterior  border  of  the  sterno-mastoid  is  filled 
— from  below  upward — by  the  scalenus  medius,  the  levator  anguli  scapulae,  and  the 
splenius,  but  none  of  them  is  recognizable  through  the  deep  fascia. 

In  the  mid-line  behind,  in  addition  to  the  bony  points  already  given  (pages 
146-148),  the  line  of  origin  of  the  trapezii  can  be  seen  as  a  slight  elongated  de- 
pression.    None  of  the  deeper  muscles  can  be  seen  or  felt  upon  the  surface. 

In  the  mid-line  in  front  the  hyoid  bone  and  its  cornua  can  be  felt  in  the  angle 
between  the  under  surface  of  the  chin  and  the  front  of  the  neck.  From  the  hyoid 
bone  on  either  side  the  anterior  bellies  of  the  digastric  run  up  towards  the  symphysis 
and  with  the  subcutaneous  fat  give  convexity  to  the  submental  region.  Farther  out 
on  this  level  the  submaxillary  salivary  glands  can  be  felt  and  often  seen. 

The  thyro-hyoid  depression,  the  prominence  of  the  thyroid  cartilage  {po?nnm 
Adamz),  the  crico-thyroid  space,  the  cricoid  cartilage,  and  sometimes  the  upper 
rings  of  the  trachea  may  be  felt  from  above  downward.  The  relations  of  these  parts 
to  important  vascular  and  nervous  structures  will  be  considered  later. 

The  sterno-thyroid  and  sterno-hyoid  muscles,  while  not  visible,  cover  over  and 
obscure  the  outlines  of  the  trachea,  as  does  also  the  thyroid  isthmus.  The  thyroid 
lobes  may  be  felt  on  each  side  of  the  larynx.  The  average  distance  from  the 
cricoid  to  the  upper  edge  of  the  manubrium  is  about  one  and  a  half  inches  when 
the  head  is  erect.  In  full  extension  three-quarters  of  an  inch  additional  can  be 
gained. 

The  trachea  recedes  as  it  approaches  the  sternum,  so  that  it  is  fully  an  inch  and 
a  half  behind  the  upper  border  of  the  latter.  In  this  position  between  the  two 
sternal  heads  of  the  sterno-mastoid  is  the  deep,  V-shaped  suprasternal  notch  (fossa 
jugularis),  the  depth  of  which  is  noticeably  affected  by  forced  respiration,  being 
much  increased  in  obstructive  dyspnoea. 

All  the  surface  appearances  above  described  differ  in  different  individuals,  and 
vary  in  the  same  person  in  accord  with  many  conditions,  as  the  amount  of  subcu- 
taneous fat,  the  muscular  vigor  and  development,  the  pulmonary  capacity,  the  state 
of  repose  or  of  violent  exertion,  etc.  This  should  be  remembered  in  looking  for 
landmarks  in  this  region,  which  is  in  that  respect  one  of  the  most  variable  of  the 
body,  and  most  unlike  that  of  the  cranium,  which  perhaps  typifies  the  other  extreme 
of  unchangeability. 

DlAPHRAGMA    (Fig.    549). 

The  diaphragm  is  a  dome-shaped  muscular  sheet  which  separates  the  thoracic 
and  abdominal  cavities.  Notwithstanding  its  position  in  the  adult,  it  is  a  derivative 
of  the  cervical  myotomes.  It  represents  the  upper  portion  of  a  structure  which  is 
termed  in  embryology  the  septum  transversum  (page  1701),  a  connective-tissue 
partition  which  extends  between  the  ventral  and  lateral  walls  of  the  body  and  the 
heart,  and  serves  to  convey  venous  trunks  to  that  organ.  Like  the  heart,  when 
first  formed  it  lies  far  forward  in  the  uppermost  part  of  the  cervical  region,  but  later 
it  descends  with  the  heart  until  it  reaches  its  final  position.  As  it  passes  the  third 
and  fourth  cervical  myotomes  in  its  descent,  it  receives  from  them  some  muscle-tissue 
which  eventually  forms  all  the  muscle-tissue  of  the  diaphragm,  that  structure,  so  far 
as  it  is  to  be  regarded  as  a  muscle,  being  a  derivative  of  the  cervical  myotomes 
named. 

The  diaphragm  is  a  muscular  sheet  composed  of  fibres  radiating  from  the  lower 
border  of  the  thorax  and  from  the  upper  lumbar  vertebrae  towards  a  central  tendi- 
nous area,  termed  the  centrum  tendineum.  According  to  their  origin,  the  muscle- 
fibres  may  be  grouped  into  three  portions.  The  sternal  portion  consists  of,  usually, 
two  bands  which  arise  from  the  posterior  surface  of  the  xiphoid  process  of  the 
sternum  and  are  separated  from  one  another  by  a  narrow  interval  filled  with  con- 
nective tissue.  Laterally  they  are  separated  by  a  similar  interval,  through  which 
the  superior  epigastric  artery  enters  the  sheath  of  the  rectus  abdominis,  from  the 


THE   CERVICAL    MUSCLES. 


557 


costal  portion,  the  fibres  of  which  take  their  origin  from  the  cartilages  of  the  lower 
six  ribs,  interdigitating  with  the  origins  of  the  transversalis  abdominis.  In  conti- 
nuity with  the  costal  part  is  the  lumbar  pari,  whose  fibres  take  origin  (i)  from  two 
tendinous  arches,  the  internal  and  external  arcuate  ligaments,  which  pass  over  the 
upper  portions  of  the  psoas  (arcus  lumbocostalis  medialis)  and  the  quadratus  lum- 
borum  muscles  (arcus  lumbocostalis  lateralis)  respectively,  stretching  between  the 
twelfth  rib  and  the  transverse  process  of  the  first  lumbar  vertebra,  and  (2)  by  two 
downward  prolongations,  the  crura,  from  the  anterior  and  lateral  surfaces  of  the 
upper  three  or  four  lumbar  vertebra?. 

The  right  crus  usually  extends  somewhat  farther  downward  than  the  left,  whose 
attachment  does  not  pass  below  the  second  or  third  vertebra.  Each  crus  has  been 
divided  into  three  portions,  medial,  intermediate,  and  lateral,  which  are  not,  how- 
ever, always  clearly  recognizable,  although  indicated  by  the  passage  of  certain  struc- 
tures from  the  thorax  to  the  abdomen.      Thus,  between  the  medial  and  intermediate 


Fig.  5^9. 

Interval  between  sternal  and  costal  portions  Lower  end  of  sternu 


Right  greater 

splanchnic  nerve. 

XII  rib. 


Inferior  vena  cava 
Sifurcation  of  aorta,  turned  forward 


L 

|>.~j — —  CEsopbagus 
Jff^'^g"  '   )    Left  portion  or 

?r: 

central  tendon 

~t    Aorta 

I^^jmE^L  Tboracic  duct 

XII: 

rib 

External  arcuate  ligament 

Quadratus  1 

umborum 

Left  ci 
Diaphragm, 


Internal  arcuate  ligament 
Psoas  magnus 
ed  from  below  and  the  left. 


crura  the  greater  splanchnic  nerve  and  the  azygos  (or  hemiazygos")  veins  pass,  while 
between  the  intermediate  and  lateral  crura  is  the  sympathetic  trunk. 

The  two  crura,  as  they  pass  upward,  leave  between  them  an  opening,  the  hiatus 
aorticus,  which  is  bridged  over  by  a  tendinous  band  {median  arcuate  ligament)  and 
gives  passage  to  the  aorta  and  thoracic  duct.  Just  behind  the  posterior  margin  of 
the  centrum  tendineum  the  crural  fibres  diverge  to  surround  in  a  sphincter-like 
manner  the  hiatus  cesophageus,  through  which  pass  the  oesophagus  and  the  vagus 
nerves  and  oesophageal  branches  from  the  gastric  artery  and  veins. 

The  centrum  tendineum,  into  which  the  fibres  of  the  three  portions  insert,  is 
situated  somewhat  nearer  the  anterior  than  the  posterior  margin  of  the  diaphragm, 
so  that  the  fibres  of  the  sternal  muscular  portion  are  considerably  shorter  than  the 
others.  It  has  a  trefoil  shape,  possessing  a  central  and  two  lateral  lobes,  the  right 
one  of  these  being  perforated  by  a  somewhat  quadrate  foramen,  the  foramen  vena; 
cava  {foramen  quadratum') ,  which  transmits  the  vena  cava  inferior. 

The  centrum  tendineum  forms  the  centre  of  the  dome  of  the  diaphragm,  and 
from  its  borders  the  muscular  fibres  slope  downward  towards  their  insertion,  the 
slope   of  the   crural   fibres   being  much  steeper  than   those  of   the  other  portions. 


558 


HUMAN    ANATOMY. 


The  dome  does  not,  however,  form  a  simple  curve,  but  is  divided  by  a  median 
depression,  which  traverses  it  from  before  backward,  into  two  secondary  lateral 
domes  which  are  unequally  developed,  that  of  the  right  side  extending  upward  as 
far  as  the  level  of  the  junction  of  the  fourth  costal  cartilage  and  rib,  while  that  of 
the  left  reaches  only  to  the  fifth  costo-cartilaginous  junction. 

Nerve-Supply. — From  the  third,  fourth,  and  sometimes  the  fifth  cervical 
nerves,  by  the  phrenic  nerves. 

Action. — To  increase  the  vertical  diameter  of  the  thorax,  a  contraction  of  the 
muscle-fibres  depressing  the  summit  of  the  dome. 

Relations. — The  upper  surface  of  the  diaphragm  forms  the  floor  of  the  thoracic 
cavity  and  is  in  contact  with  the  pleurae  and  pericardium,  the  latter  being  adherent  to 
the  centrum  tendineum.  Below,  the  diaphragm  is  largely  invested  by  peritoneum,  and 
is  in  relation  with  the  liver,  stomach,  spleen,  kidneys,  suprarenal  bodies,  duodenum, 
pancreas,  inferior  vena  cava,  and  the  branches  of  the  cceliac  artery. 

Variations. — Occasionally  the  diaphragm  is  incomplete  in  its  posterior  portion,  a  condition 
which  permits  the  formation  of  congenital  diaphragmatic  hernias.  Embryologically  the  pos- 
terior portion  of  the  diaphragm  is  the  last  to  form,  and  in  this  fact  is  probably  to  be  found  an 
explanation  of  the  location  of  this  imperfection  and  also  of  the  course  of  the  phrenic  nerves 
anterior  to  the  roots  of  the  lungs  to  reach  the  earlier  formed  anterior  portion  of  the  diaphragm. 

Fibres  which  arise  from  the  crura  and  pass  to  neighboring  structures  are  frequently  present. 
Among  the  more  constant  of  these  are  fibres  which  arise  from  the  inner  borders  of  both  crura 
and  pass  to  the  lower  portion  of  the  oesophagus,  mingled  with  dense  connective-tissue  fibres, 
and  others  which  pass  from  one  crus  or  the  other  into  the  mesentery  of  the  upper  part  of  the 
jejunum.  Probably  the  suspensory  muscle  of  the  duodenum,  or  muscle  of  Treitz,  which  passes 
from  the  left  crus  to  the  terminal  portion  of  the  duodenum,  belongs  to  this  latter  group  of  fibres, 
although  it  has  been  stated  to  be  formed  by  non-striated  muscle-fibres. 

THE    PELVIC   AND    PERINEAL   MUSCLES. 

The  ventral  portions  of  the  myotomes  succeeding  the  first  lumbar  and  from  that 
as  far  down  as  the  third  (or  second)  sacral  are  almost  entirely  unrepresented  in  the 
trunk,  being  devoted  to  the  formation  of  the  musculature  of  the  lower  limb.      Below 


Fig.  550. 


External  iliac  vessels 


llio-pectineal  line 
Acetabulum 
Levator  ani 


Obturator  internu 

Alcock's  canal    «S 


Pelvic  fascia 
Obturator  fascia 
Anal  fascia 


External  sphincter  j      I 

Internal  sphincter    Rectum 


Fascia  endopelvina 
^   Pelvic  fascia 
Recto-vesical  layer 


Diagrammatic  frontal  section  through  pelvis,  showing  relations  of  fascial  layers  to  pelvic  wall  and  floor. 

the  point  mentioned,  however,  the  ventral  musculature  again  appears  in  the  trunk 
in  the  pelvic,  the  perineal,  and  occasionally  the  coccygeal  region.  Owing  to  the 
conditions  under  which  it  appears,  it  is  not  possible  to  refer  the  muscles  derived  from 
it  to  the  various  subdivisions  into  which  the  ventral  musculature  of  other  regions  is 
divisible,  and  they  will  therefore  be  considered  in  sequence  without  any  attempt  at 
classification  other  than  regional. 

The  Pelvic  Fascia. — The  pelvic  fascia  is  attached  above  to  the  promontory 
of  the  sacrum  and  the  ilio-pectineal  line  (linea  terminalis)  of  the  pelvis,   where  it 


THE    PELVIC   AND    PERINEAL    MUSCLES.  559 

becomes  continuous  with  the  iliac  fascia.  It  descends  over  the  surface  of  the  pyri- 
formis  and  laterally  over  the  upper  portion  of  the  obturator  internus  and  the  pelvic 
surface  of  the  pelvic  diaphragm.  In  the  upper  part  of  its  course  over  the  pelvic  dia- 
phragm it  is  crossed  by  a  curved  thickening,  the  arcus  tendineus,  which  is  attached 
behind  to  the  spine  of  the  ischium  and  passes  in  front  upon  the  sides  of  the  prostate 
gland  or,  in  the  female,  upon  the  bladder,  and  is  continued  thence  to  the  anterior 
pelvic  wall  to  be  attached  on  either  side  of  the  symphysis  pubis,  a  little  above  its 
lower  border,  as  a  lateral  pubo-prostatic  (pubo-vesical)  ligame?it.  Along  this  tendi- 
nous arch  the  pelvic  fascia  gives  off  a  layer  which  passes  inward  to  the  pelvic  viscera, 
and  is  termed  the  fascia  endopelvina.  In  its  anterior  portion  this  forms  an  investment 
of  the  prostate  in  the  male  and  of  the  base  of  the  bladder  in  the  female,  and  its  under 
surface  in  this  region  is  in  contact  with,  and  indeed  may  be  regarded  as  being  fused 
with,  the  superior  layer  of  the  triangular  ligament  (page  563).  That  portion  of  the 
layer  which  intervenes  between  the  prostate  (or  bladder)  and  the  posterior  surface 
of  the  body  of  the  pubis  forms  what  is  termed  the  median  pubo-prostatic  {pubo-vesical ) 
ligament. 

The  continuation  of  the  pelvic  fascia  passes  downward  over  the  surface  of  the 
pelvic  diaphragm,  and  is  termed  the  superior  fascia  of  that  structure  (fascia  dia- 
phragmatis  pelvis  superior). 

The  Obturator  Fascia. — From  the  line  along  which  the  pelvic  fascia  leaves  the 
surface  of  the  obturator  internus  muscle  to  pass  upon  the  pelvic  diaphragm  a  sheet  of 
fascia  is  continued  downward  over  the  surface  of  the  obturator  internus  muscle  to  be 
attached  below  to  the  tuberosity  and  ramus  of  the  ischium  and  the  ramus  inferior  of 
the  pubis.      This  is  the  obturator  fascia. 

Along  its  upper  border,  nearly  corresponding  with  the  arcus  tendineus  of  the 
pelvic  fascia,  but  lying  above  this  thickening  and  ending  anteriorly  farther  from  the 
median  line,  is  a  similar  curved  thickening  extending  from  the  spine  of  the  ischium, 
or  in  some  cases  from  the  ilio-pectineal  line  behind  to  the  posterior  surface  of  the 
body  of  the  os  pubis  in  front.  From  this  thickening  the  greater  portion  of  the  levator 
ani  muscle  arises  ;  it  is  consequently  termed  the  arcus  tendineus  m.  levatoris  ani,  or 
more  briefly  the  white  line.  From  the  line  a  thin  layer  of  fascia  is  continued  inward 
upon  the  under  surface  of  the  levator  ani,  forming  what  is  termed  the  anal  fascia 
(fascia  diaphragmatis  pelvis  inferior). 

This  latter  fascia  forms  the  inner  and  the  obturator  fascia  the  outer  wall  of  the 
ischio-rectal  fossa.  Near  its  lower  border  the  obturator  fascia  splits  into  two  layers  to 
form  a  canal,  the  canal  of  Alcock,  along  which  the  pudic  vessels  and  nerve  pass 
towards  the  perineum. 

In  the  above  description  the  term  pelvic  fascia  is  applied  to  the  layer  of  fascia  which  lines 
the  entire  true  pelvic  cavity, — that  is  to  say,  the  funnel-shaped  cavity  included  between  the  pel- 
vic brim  and  floor.  This  conception,  employed  by  the  German  authors,  differs  somewhat  from 
that  usually  held  by  English  anatomists,  in  that  the  latter  restrict  the  term  to  that  portion  of 
the  fascia  extending  from  the  ilio-pectineal  line  to  the  white  line,  the  continuation  down- 
ward over  the  pelvic  diaphragm  being  termed  the  recto-vesical  fascia,  from  which  extensions 
pass  to  the  bladder,  prostate  gland,  and  rectum.  The  term  recto-vesical  has  also  been  restricted 
to  the  portion  of  the  sheet  which  extends  between  the  rectum  and  the  bladder  and  encloses  the 
seminal  vesicles  (Cunningham),  and  if  the  term  is  to  be  employed  at  all,  this  application  of  it 
seems  to  be  the  preferable  one. 

Confusion  has  also  existed  in  the  application  of  the  term  "white  line,"  since  it  has  been 
made  to  include  both  the  arcus  tendineus  proper  and  the  thickened  band  from  which  the  leva- 
tor ani  takes  its  origin  (arcus  tendineus  m.  levatoris  ani).  These  two  bands  are,  however,  quite 
distinct,  especially  anteriorly,  as  a  careful  inspection  of  the  subject  will  demonstrate,  and  it  seems 
preferable  to  restrict  the  term  "white  line"  to  that  from  which  the  levator  ani  arises,  naming 
that  at  which  the  fascia  endopelvina  begins  the  arcus  tendineus. 

(a)    THE   PELVIC   MUSCLES. 

1.    Levator  ani.  2.    Coccygeus. 

3.    Pyriformis. 

The  floor  of  the  pelvis  is  formed  by  two  muscles  which  constitute  an  almost 
complete  partition,  the  pelvic  diapliragm,  separating  the  pelvic  from  the  perineal 
region.      The  more  anterior  and  larger  of  these  muscles  is  the  levator  ani,  the  coccy- 


560 


HUMAN   ANATOMY. 


geus  lying  along  its  posterior  margin.  Above  the  upper  margin  of  the  latter,  and 
forming  the  posterior  wall  of  the  pelvis,  is  the  pyriformis.  Slight  intervals  occupied 
by  connective  tissue  usually  exist  between  the  coccygeus  and  the  other  two  muscles, 
presenting  opportunities  for  pelvic  hernias. 

i.  Levator  Ani  (Fig.  551). 
Attachments. — The  levator  ani  arises  from  the  posterior  surface  of  the  body  of 
the  os  pubis  in  front,  from  the  spine  of  the  ischium  behind,  and  in  the  interval  between 
these  two  points  from  a  thickening  of  the  upper  border  of  the  obturator  fascia,  the 
white  line.  From  this  long  line  of  origin  the  fibres  converge  downward  and  medially 
to  be  inserted  into  the  sides  and  tip  of  the  coccyx,  into  a  tendinous  raphe  extending 
in  the  median  line  between  the  tip  of  the  coccyx  and  the  anus,  and  into  the  sides  of 
the  lower  part  of  the  rectum.  The  fibres  from  the  most  anterior  portion  of  the  origin 
pass  almost  directly  backward  and  downward  to  reach  the  sides  of  the  rectum,  and 
between  them  and  the  corresponding  fibres  of  the  muscle  of  the  opposite  side  is  a 

Fig.  551. 


_  Tip  of  coccyx 
-  Ischial  spine 


Ro  lu 


(cut) 


7 


.Obturator  inter- 
nus  covered  by 
./  pelvic  fascia 

3^ -Urethra  (cut) 


lar  floor  of  pelv 


.      - 
ved  from  above. 


space,  occupied  in  the  male  by  the  lower  part  of  the  prostate  gland  and  in  the  female 
by  the  base  of  the  bladder  and  lower  part  of  the  vagina,  the  fascia  endopelvina  in 
this  region  coming  into  contact  with  the  upper  surface  of  the  superior  layer  of  the 
triangular  ligament  of  the  perineum. 

Nerve-Supply. — The  posterior  portion  of  the  muscle  is  supplied  by  a  special 
branch  from  the  third  and  fourth  sacral  nerves,  the  anterior  portion  by  twigs  from  the 
inferior  hemorrhoidal  branches  of  the  pudic  nerve. 

Action. — To  bend  the  coccyx  forward  and  to  raise  the  pelvic  floor  and  viscera. 

Variations.— The  levator  ani  is  always  a  well-developed  muscle,  although  the  extent  of  its 
attachment  to  the  sides  of  the  coccyx  varies  inversely  to  the  attachment  of  the  coccygeus  to  that 
bone.  There  is  usually  to  be  found  a  dividing  line  extending  across  the  muscle  on  a  level  with 
the  junction  of  the  superior  ramus  of  the  pubis  with  the  ilium  and  separating  those  fibres  which 
are  inserted  into  the  coccyx  and  the  posterior  portion  of  the  fibrous  raphe  from  those  which 
pass  to  the  anterior  part  of  the  raphe  and  the  rectum.  Each  of  the  portions  so  separated  is  sup- 
plied by  a  separate  nerve,  and  this,  combined  with  the  results  of  comparative  anatomy,  seems 
to  show  that  the  posterior  portion  of  the  levator  is  really  a  muscle  quite  distinct  from  the  ante- 
rior portion.     It  has  been  termed  the  m.  ilio-coccygeus.     Furthermore,  it  seems  probable  that 


THE    PELVIC   AND    PERINEAL    MUSCLES. 


56i 


the  anterior  portion  is  composed  of  two  morphologically  distinct  muscles,  one  of  which  arises 
from  the  pubis  and  anterior  part  of  the  white  line  and  is  inserted  into  the  median  fibrous  raphe, 
whence  it  is  termed  the  m.  pubo-coccygeus  ;  while  the  other,  situated  beneath, — i.e.,  superficial  to 
the  pubo-coccygeus, — consists  of  those  fibres  which  arise  from  the  pubis  and  are  inserted  into 
the  rectum,  and  is  termed  the  in.  pubo-rectalis. 

It  may  be  added  that  in  the  lower  mammals  the  muscles  corresponding  to  the  ilio-coc- 
cygeus  and  pubo-coccygeus  are  inserted  into  the  caudal  vertebrae  and  act  as  lateral  flexors  of 
the  tail. 

2.    COCCYGEUS   (Figs.  551,  603). 

Attachments. — The  coccygeus,  which  forms  the  posterior  and  lesser  portion 
of  the  diaphragma  pelvis,  lies  immediately  behind  the  levator  ani.  It  arises  from 
the  spine  of  the  ischium  and  is  inserted  into  the  sides  of  the  sacrum  and  coccyx. 

Nerve-Supply. — From  the  third  and  fourth  sacral  nerves. 

Action. — To  assist  the  levator  ani  in  raising  the  pelvic  floor.  It  also  flexes 
the  coccyx  laterally. 

Variations. — Occasionally  the  insertion  of  the  coccygeus  is  confined  to  the  sides  of  the 
sacrum,  in  which  cases  its  coccygeal  area  is  occupied  by  fibres  of  the  levator  ani.  The  muscle 
is  sometimes  termed  the  ischio-coccygeus,  and  is  represented  in  the  lower  mammals  by  a  muscle 
attached  to  the  caudal  vertebrae  and  acting  as  a  lateral  flexor  of  the  tail. 

The  Sacro-  Coccygeus  Anterior. — Occasionally  muscular  fibres  are  to  be  found  arising  from 
the  ventral  surface  of  the  sacrum  and  inserting  into  the  coccyx.  They  form  what  is  termed  the 
sacro-coccygeus  anterior  or  curvator  coccygis,  and  apparently  belong  to  the  hyposkeletal  group 
of  muscles. 

•3.   Pyriformis   (Figs.  551,  552,  602.) 

Attachments. — The  pyriformis  (m.  piriformis)  arises  from  the  ventral  surface 
of  the  sacrum,  between  the  first,  second,  third,  and  fourth  sacral  foramina.  It 
passes  laterally  through 
the  great  sciatic  fora- 
men, receiving  a  bundle 
of  fibres  from  the  upper 
margin  of  the  foramen, 
and  is  inserted  into  the 
summit  of  the  great 
trochanter,  its  tendon 
shortly  before  its  inser- 
tion becoming  closely 
united  with  that  of  the 
obturator  interims. 

Nerve  -  Supply. 
— By  branches  from  the 
sacral  plexus  from  the 
first  and  second  sacral 
nerves. 

Action. — To  ro- 
tate the  thigh  outward 
and  to  draw  it  slightly 
outward  and  back- 
ward. 

Relations.  —  By 
its  anterior  surface, 
while  within  the  pelvis, 

the  pyriformis  is  in  relation  to  the  sacral  plexus,  the  anterior  branches  of  the  internal 
iliac  vessels,  and  the  rectum.  It  lies  immediately  above  the  upper  border  of  the 
coccygeus  muscle.  Outside  the  pelvis  it  is  usually  separated  from  the  capsule  of  the 
hip-joint  by  the  gluteus  minimus  and  is  covered  by  the  gluteus  medius.  Above  the 
upper  border  of  the  muscle  at  its  exit  from  the  greater  sciatic  foramen  are  the  gluteal 
vessels  and  the  superior  gluteal  nerve,  while  below  its  lower  border,  between  this  and 
the  superior  gemellus,  are  the  sciatic  and  internal  pudic  vessels  and  the  pudic,  sciatic, 
small  sciatic,  and  inferior  gluteal  nerves.  A  bursa,  the  bursa  m.  pyriformis,  inter- 
venes between  the  tendon  of  the  muscle  and  the  summit  of  the  great  trochanter. 

36 


Greater  sacro- 
-»—  sciatic  foramen 
:If     Dorsum  of  ilium 
Greater  sacro- 
sciatic  foramen 
Pyriformis 

Obturator  internus 
Capsule  of  hip-joint 


Obturator  intern 
Greater 
ligament 


Deep  dissection,  showing  insertion 


d  external  obturator 


562 


HUMAN    ANATOMY. 


Variations. — The  pyriformis  is  occasionally  absent,  and  it  may  be  more  or  less  fused  with 
the  gluteus  minimus  or  medius.  Frequently  it  is  divided  into  two  or  more  portions  by  being 
perforated  by  the  sciatic  nerve. 

From  the  comparative  stand-point  the  pyriformis  is  to  be  regarded,  in  part  at  all  events,  as 
a  portion  of  the  musculature  extending  between  the  axial  skeleton  and  the  pelvic  girdle  or  limb,, 
and  is  represented  in  the  lower  vertebrates  by  the  caudo-femora/is. 


i.   Sphincter  ani  externus. 

2.  Transversus  perinaei  superficialis 

t,.    Ischio-cavernosus. 


(6)   THE   PERINEAL   MUSCLES. 

4.  Bulbo-cavernosus. 

5.  Transversus  perineei  profundus. 

6.  Compressor  urethras. 


In  the  early  stages  of  development,  while  the  urogenital  ducts  and  the  digest- 
ive tract  open  into  a  common  terminal  cavity,  the  cloaca,  muscle-fibres  derived 
from  the  second,  third,  and  fourth  sacral  myotomes  arrange  themselves  in  a  flat 
layer  around  the  external  aperture  of  the  cavity,  forming  what  is  termed  the 
sphincter  cloaccs.  Later,  with  the  division  of  the  cloaca  into  a  urogenital  and  a 
rectal  portion  and  the  resulting  formation  of  the  perineum,  this  primary  sphincter 
becomes  divided  into  two  portions,  one  of  which  forms  a  sphincter  ani,  while  the 
more  anterior  portion  gives  rise  to  the  muscles  of  the  perineum.  The  fibres  of  this 
latter  portion  undergo  various  modifications  in  accordance  with  the  changes  which 

Fig.  553. 

\     Y^ Peritoneur 

Urachus. 

Supravesical  space 


Symphysis  pubis 

Suspensory  ligament  of  penis 
Triangular  ligament,  sup.  lay- 
Deep  perineal  interspace t —  ~  _    ---    ..  ,  , 

„  .         , />/— -^==5^:    ^*^-  ^3t — Ht — : C^vper  s  gland 

Triangular  hgamt,  inf.  layer.    -*~  -—<•■ 

Ureth 
Penis,  corpus  cavernosu  . 

Perineal  centre 
Colles's  fascia 
Superficial  perineal  interspace 

Continuation  of  Colles's  fascia 


Diagrammatic  sagittal 


showing  relations  of  fascial  layers  of  perineum. 


take  place  in  the  urogenital  sinus,  and  a  horizontal  separation  of  the  original 
sphincter  into  two  layers  also  occurs,  whereby  the  perineal  muscles  are  arranged  in 
two  layers  separated  by  the  superior  fascia  of  the  urogenital  trigone. 

The  muscles  formed  during  these  changes  retain  the  original  sheet-like  form  of 
the  sphincter  cloacae  and  are  for  the  most  part  pale  in  color,  resembling  not  a  little  in 
their  general  character  the  platysma  muscles  of  the  face.  They  show  a  considerable 
amount  of  difference  in  their  development  in  different  individuals,  numerous  acces- 
sory muscles  having  been  described  by  various  authors,  some  of  which  will  be 
referred  to  in  the  succeeding  descriptions. 

The  Superficial  Perineal  Fascia. — The  superficial  perineal  fascia,  being 
continuous  anteriorly  with  the  superficial  fascia  of  the  lower  portion  of  the  anterior 
abdominal  wall,  is,  like  this,  composed  of  two  layers.  The  more  superficial  layer 
usually  contains  a  certain  amount  of  fat,  and,  as  in  the  abdomen,  is  really  the  pan- 
niculus  adiposus  of  the  skin.  The  deeper  layer,  which  has  been  termed  the  fascia 
of  Colles,  forms  a  continuous  membrane  which  is  attached  at  the  sides  to  the  rami 
of  the  pubes  and  ischia  and  in  front  becomes  continuous  with  the  dartos  of  the: 


THE   PELVIC   AND    PERINEAL   MUSCLES.  563 

scrotum  (or  fascia  of  the  labia  majora)  and  on  either  side  of  this  with  the  corre- 
sponding layer  of  the  abdomen.  Behind  it  unites  with  the  posterior  border  of  the 
trigonum  urogenitale  on  a  line  extending  between  the  two  ischial  tuberosities,  and 
thence  is  continued  backward,  forming  a  single  sheet  with  the  superficial  layer,  to 
unite  with  the  superficial  fascia  of  the  gluteal  region.  This  posterior  portion  of  the 
superficial  perineal  fascia  may  conveniently  be  termed  the  circumanal  fascia. 

By  the  union  of  the  deep  layer  of  the  superficial  fascia  with  the  triangular  liga- 
ment behind,  an  almost  completely  enclosed  space  is  formed  between  the  two  struc- 
tures ;  it  is  open  only  anteriorly  where  it  communicates  with  the  areolar  spaces 
between  the  superficial  and  deep  layers  of  the  abdominal  fasciae.  This  space  is  the 
superficial  perineal  interspace,  and  contains  the  bulb  and  spongy  portion  of  the 
urethra,  the  corpora  cavernosa,  and  certain  of  the  perineal  muscles. 

The  Trigonum  Urogenitale. — The  trigonum  urogenitale,  more  usually  called 
the  triangular  ligament  of  the  perineum,  is  formed  by  the  deep  fascia  of  the  peri- 
neum, and,  like  the  superficial  fascia,  is  composed  of  two  layers,  the  sziperior  and 
inferior  (fasciae  trigoni  urogenitalis  superior  et  inferior).  At  the  sides  both  layers  are 
attached  to  the  rami  of  the  pubes  and  ischia,  in  front  to  either  edge  of  the  lower 
border  of  the  pubis,  and  behind  they  unite  with  each  other  and  with  the  deep  layer 
of  the  superficial  fascia  along  a  line  extending  transversely  across  the  perineum 
between  the  tuberosities  of  the  ischia.  Between  the  two  layers  there  is  a  completely 
closed  space,  the  deep  perineal  interspace,  in  which  are  to  be  found  the  membranous 
portion  of  the  urethra,  the  bulbo-urethral  glands,  the  pudic  vessels  and  nerves,  and, 
in  front,  the  subpubic  or  arcuate  ligament  of  the  pubis. 

At  their  lateral  insertions  the  layers  of  the  trigone  are  continuous  with  the 
obturator  fascia,  and  the  superior  layer  is  fused  above  with  the  portion  of  the  fascia 
endopelvina  which  invests  the  lower  surface  of  the  prostate  gland  (or  the  base  of  the 
bladder).  The  trigone  is  perforated  by  the  urethra  and,  in  the  female,  by  the  vagina, 
and  anteriorly  the  dorsal  vein  of  the  penis  passes  through  it  immediately  behind  the 
subpubic  ligament  of  the  pubis,  the  fibres  of  the  trigone  immediately  behind  the 
opening  for  the  vein  being  thickened  to  form  a  transverse  band  known  as  the  trans- 
verse ligament  of  the  pelvis. 

1.  Sphincter  Ani  Externus  (Fig.  554). 

Attachments. — The  external  sphincter  of  the  anus  consists  of  a  group  of 
fibres  which  surround  the  terminal  portion  of  the  rectum,  the  superficial  fibres 
standing  in  close  relationship  with  the  integument.  Its  fibres  arise  posteriorly 
from  the  coccyx  and  from  the  raphe  extending  from  that  bone  to  the  anus,  and, 
passing  forward  around  the  anus,  are  inserted  into  the  superficial  fascia  and  the 
central  tendon  of  the  perineum,  and  may  in  some  cases  be  continued  forward  to 
join  with  the  fibres  of  the  superficial  transverse  perineal  and  bulbo-cavernosus 
muscles. 

The  central  tendon  of  the  perineum  is  situated  in  the  median  line  about  2. 5  cm. 
in  front  of  the  anus,  and  is  the  point  of  union  of  five  muscles, — namely,  the  external 
sphincter  ani,  the  two  superficial  transversi  perinei,  and  the  bulbo-cavernosi. 

Nerve-Supply. — From  the  fourth  sacral  nerve  and  the  inferior  hemorrhoidal 
branches  of  the  pudic. 

Action. — To  close  the  anal  aperture.  It  also  serves  to  fix  the  central  tendon 
of  the  perineum  during  the  contraction  of  the  bulbo-cavernosi. 

Variations. — The  common  embryological  origin  of  the  external  sphincter  ani  and  the  perineal 
muscles  is  indicated  by  the  extension  forward  of  the  fibres  of  the  former  to  join  the  bulbo-caver- 
nosus, and  occasionally  a  fasciculus  of  it  extends  as  far  forward  as  the  base  of  the  scrotum, 
forming  what  has  been  termed  the  retractor  scroti. 

The  longitudinal  muscle-fibres  of  the  lower  portion  of  the  rectum  pass  below  into  a  sheet 
of  connective  tissue,  which  divides  into  three  more  or  less  distinct  layers  extending  to  the 
integument.  The  outer  two  of  these  layers  traverse  the  substance  of  the  external  sphincter 
ani,  a  portion  of  the  outermost  one  being  continued  backward  to  the  region  of  the  coccyx  on 
each  side  of  the  median  line  as  a  moderately  strong  band  known  as  the  ano-coccygeal  ligament. 
By  these  layers  of  fibrous  tissue  the  external  sphincter  is  divided,  sometimes  quite  distinctly, 
into  three  portions  which  have  been  regarded  as  distinct  muscles.  One  of  these  lies  imme- 
diately beneath  the  skin  surrounding  the  anus,  and  has  consequently  been  termed  the  sphincter 


564 


HUMAN   ANATOMY. 


subaitaneus.  The  sphincter  superficialis  is  that  portion  of  the  muscle  which  lies  above  and  to 
the  outer  side  of  the  sphincter  subcutaneus,  while  more  deeply  still,  and  forming  a  ring-like 
mass  of  fibres  closely  encircling  the  rectal  wall,  is  the  sphincter  profundus.  It  is  from  the 
sphincter  subcutaneus  that  the  retractor  scroti,  when  present,  is  derived,  and  fibres  from  the 
sphincter  superficialis  are  frequently  prolonged  in  front  of  the  anus  to  various  insertions,  as,  for 
instance,  to  the  tuber  ischii,  the  lower  layer  of  the  trigonum  urogenitale,  or  even  the  sheath  of 
the  corpora  cavernosa.  This  layering  of  the  external  sphincter  is  probably  a  relic  of  the  separa- 
tion of  the  sphincter  cloacae  into  two  layers,  the  subcutaneous  and  superficial  sphincters  repre- 
senting a  portion  of  the  superficial  layer,  while  the  deeper  one  is  responsible  for  the  sphincter 
profundus. 

2.  Transversus  Perin^ei  Superficialis  (Fig.  554). 
Attachments. — The  superficial  transverse  perineal  muscle  is  an  exceedingly- 
variable  sheet  of  muscle-fibres  situated  in  the    posterior  portion  of   the  superficial 
perineal  interspace.      In  its  typical  form  it  may  be  described  as  a  band  of  fibres  which 

Fig-   554- 


Bulbo-cavern 


:m 


Triangular  liga- 
ment, inf.  layer 

Tendino 

1  centre 

Tuberosity  of 
ischium 


Obturator  fascia 


Gluteus 

/       maximus  (cut) 


ale  perineum  and  pel 


from  below. 


arises  from  the  medial  surface  of  the  ischial  tuberosity  and  passes  directly  medially 
to  be  i?iserted  into  the  central  tendon  of  the  perineum. 

Nerve-Supply. — From  the  perineal  branches  of  the  pudic  nerve. 

Action. — To  assist  in  fixing  the  central  tendon  of  the  perineum  during  the 
contraction  of  the  bulbo-cavernosi. 

Variations. — The  muscle  may  occasionally  be  entirely  absent.  It  frequently  receives  fibres 
from  the  anterior  ( pubo-rectal )  portion  of  the  levator  ani  and  from  the  external  sphincter  ani 
and  makes  connections  with  the  bulbo-cavernosi. 


3.    Ischio-Cavernosus  (Fig.  554). 

Attachments.— The  ischio-cavernosus,  also  named  the  erector  penis  (erector 
c/i/oridis),  represents  the  lateral  portion  of  the  sphincter  cloacae.  The  two  muscles 
occupy  the  lateral  parts  of  the  superficial  perineal  interspace,  each  arisi?ig  from  the 
base  of  the  tuberosity  of  the  ischium,  enclosing  the  base  of  the  crus  penis  (clito- 
ridis)  as  in  a  sheath,  and  passing  forward  to  be  inserted  into  the  corpus  cavernosum. 
The  muscle  in  the  female  differs  from  that  of  the  male  only  in  size. 

Nerve-Supply. — F'rom  the  perineal  branches  of  the  pudic  nerve 


THE    PELVIC   AND    PERINEAL    MUSCLES.  565 

Action. — To  compress  the  corpus  cavernosum  and  thus  assist  in  producing  or 
maintaining  erection  of  the  penis  (or  clitoris). 

4.    Bulbo-Cavernosus  (Fig.  554). 

Attachments. — The  bulbo-cavernosus  differs  somewhat  in  its  relations  in  the 
two  sexes.  In  the  male,  in  which  it  is  also  termed  the  accelerator  urince,  the  two 
muscles  of  opposite  sides  are  united  in  a  median  fibrous  raphe  which  extends  forward 
from  the  central  tendon  of  the  perineum  over  the  bulb  and  corpus  spongiosum. 
Arising  from  this  raphe,  the  fibres  are  directed  laterally  and  forward  over  the  bulb 
and  corpus  spongiosum  and  are  inserted  into  the  under  surface  of  the  inferior  layer 
of  the  urogenital  trigone  and  into  the  fibrous  sheath  of  the  corpus  cavernosum,  some 
of  the  more  anterior  fibres  being  continued  dorsally  to  insert  into  the  fascia  covering 
the  dorsum  of  the  penis  and  forming  what  has  been  termed  the  muscle  of  Houston, 
or  compressor  vents  dorsalis  penis. 

In  the  female,  in  which  the  muscle  has  been  termed  the  sphincter  vagince  (Fig. 
lTS2>)t  the  two  muscles  of  opposite  sides  are  widely  separated  from  each  other  by  the 
vagina,  which  they  surround.  They  arise  from  the  central  tendon  of  the  perineum, 
pass  forward,  investing  the  bulbi  vestibuli,  and  are  lost  in  the  fascia  covering  the 
corpora  cavernosa  and  the  dorsal  surface  of  the  clitoris. 

Nerve-Supply. — From  the  perineal  branches  of  the  pudic  nerve. 

Action. — To  compress  the  bulb  and  corpus  spongiosum  and  so  tend  to  expel 
any  fluid  contained  in  the  urethra.  The  fibres  which  pass  to  the  dorsum  of  the  penis 
(or  clitoris)  may  aid  slightly  in  the  erection  of  that  organ,  either  directly  or  by 
compressing  the  dorsal  vein. 

Variations.— The  posterior  portion  of  the  muscle,  that  surrounding  the  bulb,  is  unrepre- 
sented in  the  female  and  is  frequently  distinctly  separable  from  the  anterior  part  in  the  male  ; 
it  has  been  termed  the  compressor  bulbi.  The  deeper  fibres  of  this  part  of  the  muscle  are  sep- 
arated from  the  more  superficial  ones  by  a  thin  layer  of  areolar  tissue,  and  have  been  regarded 
as  forming  a  distinct  muscle,  the  compressor  kemisphericum  bulbi,  which  closely  surrounds  the 
bulb,  the  two  muscles  of  either  side  interlacing  above  the  bulb  so  as  to  form  practically  a  single 
muscle  very  variable  in  its  development.  Finally,  fibres  may  arise  from  the  ischial  tuberosities 
in  common  with  those  of  the  transversi  superficiales  and  pass  forward  and  medially  to  unite 
with  the  bulbo-cavernosi  forming  what  have  been  termed  the  ischio-bulbosi. 

5.    Transversus  Perintei  Profundus  (Fig.  1629). 

Attachments. — The  deep  transverse  perineal  muscle  is  situated  in  the  poste- 
rior part  of  the  deep  perineal  interspace.  It  arises  from  the  medial  surface  of  the 
inferior  ramus  of  the  ischium  and  passes  transversely  inward  to  the  median  line, 
where  it  partly  unites  with  its  fellow  of  the  opposite  side  and  partly  inserts  into  the 
central  tendon  of  the  perineum. 

Nerve-Supply. — From  the  perineal  branches  of  the  pudic  nerve. 

Action. — To  assist  in  fixing  the  central  tendon  of  the  perineum. 

6.    Compressor  Urethr^e  (Fig.  1629). 

Attachments. — The  compressor  or  constrictor  of  the  urethra  (m.  sphincter 
urethrae  metnbranaceae)  in  the  male  is  a  thin  sheet  of  muscle-tissue  situated  in  the  deep 
perineal  interspace  anterior  to  the  deep  transversus  perineei.  It  arises  from  the  inner 
surface  of  the  inferior  ramus  of  the  pubis  and  is  inserted  by  passing  medially  to  sur- 
round the  membranous  portion  of  the  urethra,  its  anterior  fibres  forming  a  median 
raphe  with  those  of  the  opposite  side.  The  posterior  fibres  of  the  muscle  enclose  the 
bulbo-urethral  gland. 

In  the  female  the  fibres  are  inserted  into  the  walls  of  the  vagina  as  it  traverses  the 
deep  perineal  interspace. 

Nerve-Supply. — From  the  perineal  branches  of  the  pudic  nerve. 

Action. — To  constrict  the  membranous  urethra  and,  in  the  female,  also  to 
flatten  the  wall  of  the  vagina. 

The  m.  ischio-pubicus  is  a  small  muscle  situated  at  the  side  of  the  deep  perineal  interspace. 
It  arises  from  the  inferior  rami  of  the  ischium  and  pubis  and  passes  anteriorly  to  be  attached  to 
the  arcuate  ligament  of  the  pubis.     It  is  frequently  wanting. 


566  HUMAN   ANATOMY. 


THE  APPENDICULAR  MUSCLES. 

The  limbs  make  their  appearance  as  two  pairs  of  flat  buds  (Fig.  69),  the  upper 
pair  being  situated  in  the  lower  cervical  and  the  lower  pair  in  the  lower  lumbar  and 
upper  sacral  regions.  Into  the  buds  processes  extend  from  the  myotomes  of  the 
regions  concerned  and  apparently  give  rise  to  the  more  proximal  muscles  of  the 
limb,  but  that  they  are  the  source  of  all  the  limb  musculature  is  as  yet  undetermined. 
The  greater  mass  of  this  musculature  develops  from  a  blastema  which  occupies  the 
interior  of  the  limb-bud  and  which  cannot  at  first  be  distinguished  from  that  which 
gives  rise  to  the  limb  skeleton,  and  whether  it  represents  a  condensation  of  tissue 
whose  fundamental  derivation  is  the  myotomes  or  is  a  derivative  of  the  ventral 
mesoderm  has  not  yet  been  definitely  decided. 

However  that  may  be,  the  limb  musculature  stands  in  relation  to  the  anterior 
divisions  of  definite  spinal  nerves,  that  of  the  upper  limb  being  supplied  by  the  lower 
five  cervical  and  the  first  thoracic  nerves  and  that  of  the  lower  limb  by  the  lower  four 
lumbar  and  upper  three  sacral  nerves,  and,  furthermore,  there  is  a  distribution  of 
these  nerves  to  the  muscles  which  may  well  be  regarded  as  segmental.  It  is  also 
worthy  of  note  that  in  those  regions  of  the  trunk  in  which  the  limbs  develop  the 
ventral  musculature  is  either  very  much  reduced  or,  as  in  the  lower  limb,  practically 
wanting. 

An  examination  of  the  limb  muscles  shows  that  they  may  be  regarded  as  being 
arranged  in  a  ventral  or  pre-axial  group  and  a  dorsal  or  post-axial  group,  and  in 
harmony  with  this  arrangement  the  nerve-fibres  which  pass  to  the  muscles  arrange 
themselves  in  ventral  or  pre-axial  and  dorsal  or  post-axial  groups.  In  the  fore-limb 
the  dorsal  group  is  represented  by  the  posterior  fasciculus  or  cord  of  the  brachial 
plexus,  while  the  ventral  one  is  distributed  between  the  lateral  and  medial  fasciculi. 
In  the  lower  limb  the  correct  relationships  of  the  two  groups  of  muscles  and  their 
nerves  are  less  readily  perceivable,  owing  to  the  forward  rotation  which  the  limb  has 
undergone  in  order  to  bring  its  axis  into  a  plane  parallel  with  that  of  the  sagittal 
plane  of  the  body,  a  rotation  which  brings  it  about  that  in  the  adult,  except  in  the 
more  proximal  portion  of  the  limb,  the  pre-axial  musculature  is  on  the  posterior  and 
the  post-axial  on  the  anterior  surface.  The  pre-axial  nerve-fibres  are  distributed 
mainly  by  the  obturator  and  greater  sciatic  (internal  popliteal)  nerves,  while  the 
post-axial  ones  pass  to  their  destinations  by  way  of  the  anterior  crural  and  greater 
sciatic  (external  popliteal)  ;  and  in  this  connection  it  is  interesting  to  note  that  the 
fibres  of  the  external  popliteal  or  peroneal,  if  traced  to  their  exit  from  the  spinal 
foramina,  will  be  found  to  lie  dorsal  to  those  of  the  internal  popliteal  or  tibial,  not- 
withstanding that  the  former  are  supplied  to  the  anterior  and  the  latter  to  the  pos- 
terior muscles  of  the  leg. 

In  this  arrangement  into  pre-axial  and  post-axial  groups  there  is,  accordingly, 
to  be  found  a  clue  to  the  proper  understanding  of  the  relations  of  the  nerves  to  the 
muscles  of  the  limbs,  and  a  further  examination  of  the  two  groups  will  reveal  indica- 
tions of  a  segmental  distribution  of  the  nerves  and  muscles  in  each.  This  arrange- 
ment may  be  most  satisfactorily  understood  by  means  of  a  diagram  (Fig.  555) 
showing  the  arrangement  of  the  muscles  and  nerves  in  what  may  be  regarded  as  its 
fundamental  condition.  The  limb-bud  may  be  regarded  as  a  flat  plate  whose  surfaces 
are  directed  dorsally  and  ventrally.  Into  the  upper  portion  of  this  plate  the  upper- 
most of  the  spinal  nerves  which  are  associated  with  it  is  prolonged,  its  post-axial 
and  pre-axial  fibres  passing  respectively  to  either  side  of  its  frontal  plane,  and  the 
succeeding  nerves  are  similarly  prolonged  into  it  in  succession  from  above  downward. 
The  nerves,  however,  which  lie  along  the  upper  and  in  the  lower  limb  also  along 
the  lower  borders  of  the  bud  are  not  prolonged  into  it  quite  so  far  as  the  others,  the 
free  edge  of  the  plate  being,  as  it  were,  rounded  off,  so  that  it  is  only  the  more  cen- 
tral (or  upper)  nerves  of  the  series  that  reach  that  portion  of  the  bud  from  which 
the  foot  (or  hand)  and  digits  will  be  developed. 

It  follows  from  this  arrangement  that  in  the  adult  each  spinal  nerve  concerned 
supplies  a  portion   of  both   the  pre-axial   and  post-axial  groups  of    muscles,  and, 


THE    APPENDICULAR    MUSCLES. 


567 


Dorsal  muscles 


lar  septum 


furthermore,  that  the  muscle-fibres  in  succession  from  one  border  of  the  limb  to  the 
other  are  supplied  by  successive  nerves,  those  supplied  by  the  uppermost  and,  in 
the  pelvic  limb  at  least,  the  lowermost  nerves  extending  only  to  the  neighborhood 
of  the  knee  (or  elbow)  or  even  a  shorter  distance  into  the  limb.  Thus,  in  the  fore- 
limb  one  may  expect  to  find  the  more  lateral  muscles  of  the  shoulder  and  arm 
supplied  by  fibres  from  the  uppermost  nerves  of  the  brachial  plexus,  those  lying 
towards  the  middle  of  the  shoulder  and  brachial  regions  and  in  the  lateral  portion 
of  the  antibrachium  and  hand  regions  by  the  middle  nerves,  and  those  along  the 
medial  portion  of  the  limb  by  the  lower  ones.  In  the  lower  limb,  however,  owing 
to  the  rotation  which  it  has  undergone,  the  arrangement  is  to  a  certain  extent 
reversed,  and  although  in  the  more  proximal  muscles  the  fibres  are  supplied  bv  suc- 
cessive nerves  from  above  downward,  lower 

down  the  fibres  from  the  upper  nerves  are  Fig.  555. 

to  be  found  along  the  inner  side  of  the  leg 
and  those  from  the  lower  nerves  along  the 
outer  side. 

If,  then,  an  originally  segmental  ar- 
rangement of  the  muscle-fibres  of  the  limbs 
is  to  be  recognized,  the  segments  must  run 
parallel  to  the  long  axis  of  the  limb,  and 
this  arrangement  has  permitted  their  free 
consolidation  to  form  the  various  muscles 
found  in  the  adult,  very  few  indeed  of 
which  are  supplied  by  a  single  nerve,  and 
represent,  accordingly,  portions  of  a  sin- 
gle primitive  segment.  Furthermore,  the 
adaptation  of  the  muscles  to  act  effectively 
on  the  various  joints  of  the  limbs  has 
brought  about  a  transverse  division  of  the 
segments,  and  has  also  led  to  a  complete 
degeneration  of  the  portions  of  some  of  the 
segments  in  one  part  of  the  limb  while  they  are  retained  in  another.  Thus,  for 
example,  in  the  pre-axial  musculature  of  the  brachial  region  no  trace  is  to  be  found 
of  the  segments  supplied  by  the  eighth  cervical  and  first  dorsal  nerves,  although 
the  eighth  cervical  is  represented  in  the  post-axial  musculature  and  both  in  the 
pre-axial  musculature  of  the  forearm. 

On  account  of  the  occurrence  of  both  fusion  and  degeneration,  little  trace  of  an 
original  segmental  arrangement  of  the  muscle-fibres  is  to  be  found  in  the  adult  limb 
muscles,  and  their  classification  according  to  the  segments  from  which  they  may  be 
derived  is  not  feasible.  Comparative  anatomy,  however,  shows  that  primarily  the 
limb  muscles  were  arranged  with  relation  to  the  various  joints  of  the  limb,  each 
muscle,  as  a  rule,  passing  over  but  a  single  joint,  and  in  this  relation  may  be  found  a 
basis  for  classification.  In  man  the  original  relations  have  been  modified  in  many 
cases  by  an  alteration  in  one  of.  the  original  points  of  attachment  of  a  muscle  so  that 
it  passes  over  two  joints,  or  by  the  end-to-end  union  of  originally  distinct  muscles 
so  that  the  same  result  is  brought  about.  Making  allowance  for  these  modifications, 
however,  the  muscles  of  the  upper  limb  may  be  classified  into  ( 1 )  those  passing  from 
the  axial  skeleton  to  the  pectoral  girdle,  (2)  those  passing  from  the  girdle  to  the 
brachium  or  arm,  (3)  those  passing  from  the  brachium  to  the  antibrachium  or  fore- 
arm, (4)  those  passing  from  the  antibrachium  to  the  carpus,  and  (5)  the  digital  mus- 
cles. Similarly  in  the  lower  limb,  in  which,  however,  owing  to  the  firm  articulation 
of  the  pelvis  to  the  sacrum,  the  first  group  of  muscles  is  practically  unrepresented, 
or  at  least  may  be  placed  with  those  of  the  second  group  extending  from  the  pelvic 
girdle  to  the  femur.  With  this  grouping  there  may  be  combined  a  recognition  of 
the  pre-axial  and  post-axial  musculature,  these  terms  being  used  in  the  lower  limb  as 
well  as  in  the  upper  to  indicate  the  relationships  which  obtained  before  the  rotation 
of  the  limb. 


Body-cavity 


Diagram  of  pre-  and  post-axial  groups  of  limb-muscles. 
{Kallmann.} 


568  HUMAN    ANATOMY. 


THE  MUSCLES  OF  THE   UPPER   LIMB. 

THE    MUSCLES    EXTENDING    BETWEEN    THE   AXIAL    SKELETON 
AND   THE   PECTORAL   GIRDLE. 

(a)     THE   PRE-AXIAL  MUSCLES. 

i.    Pectoralis  major.  2.    Pectoralis  minor. 

3.    Subclavius. 

The  Pectoral  Fascia. — The  superficial  pectoral  fascia  is  continuous  above 
with  the  superficial  cervical  and  below  with  the  superficial  abdominal  fasciae,  and 
covers  the  entire  anterior  wall  of  the  thorax.  It  usually  contains  a  considerable 
amount  of  fat  and  has  embedded  in  it  the  mammary  gland. 

The  deep  fascia  is  attached  above  to  the  clavicle,  and  forms  a  thin  membrane 
closely  adherent  to  the  surface  of  the  pectoralis  major,  at  the  lower  border  of  which 

Fig.  556. 


External  anterior  thoracic  nerve 
Cephalic 
Branch  of  acromio-tho 


.  Pectoralis  major,  cut  edge 
of  clavicular  portion 


I  ^>   Pectoralis  major,  cut 

■*  'h  _ edge  of  sternocostal 

^^»i--  portion 


Dissection  of  thoracic  wall  after  removal  of  greater  part  of  pectoralis  major,  showing  clavi-pectoral  fascia 
enclosing  pectoralis  minor  and  continuous  with  axillary  fascia.  , 

it  becomes  continuous  with  the  axillary  fascia.  Medially  it  is  attached  to  the  ventral 
surface  of  the  sternum  and  laterally  it  is  continuous  with  the  fascia  covering  the  deltoid. 
Beneath  the  deep  fascia  there  arises  from  the  clavicle  a  second  sheet  of  fascia 
{clavi-pectoral  fascia)  (Fig.  556)  which  encloses  the  subclavius  muscle  .and  is  then 
continued  downward  to  the  upper  border  of  the  pectoralis  minor.  There  it  divides 
into  two  sheets  which  enclose  the  muscle  and  at  its  lower  margin  unite  to  form  a 
single  sheet  which  becomes  continuous  with  the  axillary  fascia  close  to  the  lower 
border  of  the  pectoralis  major.  The  portion  of  this  fascia  which  intervenes  between 
the  clavicle  and  the  subclavius  muscle  and  the  upper  border  of  the  pectoralis  minor 
is  termed  the  coraco-clavicular  fascia  or  costo-coracoid  membrane.  It  is  prolonged 
laterally  along  the  upper  border  of  the  pectoralis  minor,  over  the  upper  portion  of 
the  axillary  vessels,  to  the  coracoid  process,  its  outer  portion  being  thickened  to  form 


THE    PECTORAL    MUSCLES. 


569 


a  band,  the  costo-coracoid  ligament  (Fig.  560),  which  passes  obliquely  downward 
and  laterally  from  the  clavicle  to  the  coracoid  process.  The  coraco-clavicular  fascia 
occasionally  contains  muscle-fibres  (the  m.  coraco-clavicularis) ,  and  is  usually  perfo- 
rated by  the  cephalic  vein  on  its  way  to  join  the  axillary,  by  the  thoraco-acromial 
artery,  and  by  the  external  anterior  thoracic  nerve. 

1.    Pectoralis  Major  (Fig.  557). 

Attachments. — The  pectoralis  major  is  a  strong  fan-shaped  muscle  situated 
on  the  anterior  thoracic  wall.  It  is  composed  of  three  portions  :  (1)  the  pars  cla- 
vicularis,  which  arises  from  the  inner  half  of  the  anterior  border  of  the  clavicle  ; 
(2)  the  pars  sterno-costalis,  which  arises  from  the  anterior  surface  of  the  sternum 
and  the  upper  six  costal  cartilages  ;  and  (3)  the  portio  abdominalis,  which  arises  from 

Fig.  557- 


Pectoralis  major, 
clavicular  portion 


Pectoralis 
major,  sterno- 
costal portion 


Serratus  magnus 


l.atissiinus  dorsi 


Direction  of  tho 


vail,  showing  pectoralis  major. 


the  upper  part  of  the  anterior  layer  of  the  sheath  of  the  rectus  abdominis.  From 
these  origins  the  fibres  are  directed  laterally  to  be  inserted  into  the  external  bicipital 
ridge  which  extends  downward  from  the  greater  tuberosity  of  the  humerus,  the  lower 
fibres  of  the  sterno-costal  and  the  abdominal  portions  of  the  muscle  passing  behind 
those  of  the  clavicular  and  upper  portions,  so  that  the  tendon  of  insertion  is  U-shaped 
in  section,  consisting  of  two  layers  separated  above  but  continuous  below.  A  bursa 
is  usually  interposed  between  the  posterior  surface  of  the  tendon  and  the  anterior 
surface  of  the  long  head  of  the  biceps  humeri. 

Nerve-Supply. — From  the  external  and  internal  anterior  thoracic  nerves  by 
fibres  from  the  lower  four  cervical  and  the  first  thoracic  nerves. 


57o  HUMAN    ANATOMY. 

Action. — When  the  arm  is  abducted  to  a  position  at  right  angles  to  the  body, 
the  pectoralis  major  will  draw  the  arm  forward  and  at  the  same  time  will  adduct  it. 
As  the  arm  approaches  the  vertical  position,  the  adductor  action  becomes  more 
pronounced  and  the  flexor  action  less  so,  and  a  slight  amount  of  internal  rotation 
appears.  When  the  arm  is  raised  above  the  level  of  the  shoulder  and  fixed,  the 
muscle  will  assist  in  drawing  the  trunk  upward,  as  in  climbing,  and  it  will  also  assist 
in  raising  the  ribs  in  forced  inspiration. 

Variations. — In  the  lower  mammals  the  pectoralis  major  is  represented  by  a  number  of 
distinctly  separate  portions,  a  condition  which  may  be  indicated  in  man  by  a  more  than  usual 
distinctness  of  the  three  portions  of  the  muscle  and  by  the  occurrence  of  accessory  slips.  The 
sterno-costal  and  abdominal  portions  may  be  greatly  reduced  or  even  absent. 

The  m.  sterna/is  is  present  in  something  over  4  per  cent,  of  all  cases  examined.  It  is  very 
variable  in  its  development,  and  consists  of  fibres  which  arise  anywhere  from  the  third  to  the 
seventh  costal  cartilage,  or  even  from  the  sheath  of  the  rectus,  and  extends  upward  to  be  attached 
to  the  anterior  surface  of  the  sternum,  the  clavicle,  or  the  tendon  of  the  sterno-cleido-mastoid. 
Usually  the  fibres  are  directed  vertically,  but  sometimes  they  may  have  a  more  or  less  oblique 
course. 

The  muscle  has  been  variously  regarded  as  a  portion  of  the  platysma,  a  downward  pro- 
longation of  the  sterno-cleido-mastoid,  an  upward  prolongation  of  the  rectus  abdominis,  and 
as  a  displaced  portion  of  the  pectoralis  major.  The  fact  that  in  the  majority  of  cases  it  is  sup- 
plied by  branches  from  the  anterior  thoracic  nerves  indicates  clearly  its  usual  derivation  from  the 
pectoralis,  but  it  is  asserted  that  in  certain  cases  it  received  its  nerve-supply  from  the  third  and 
fourth  intercostal  nerves,  in  which  cases  it  is  more  probably  to  be  regarded  as  representing  a 
thoracic  portion  of  the  rectus  trunk  muscles. 

The  chondro-epitrochlearis  is  a  slip  derived  from  the  pectoralis  major  which  takes  its 
origin  from  the  lower  costal  cartilages  or  the  abdominal  portion  of  the  pectoralis  and  is  inserted 
into  the  brachial  fascia  or  the  medial  epicondyle  of  the  humerus. 

2.   Pectoralis  Minor  (Fig.  560). 

Attachments. — The  pectoralis  minor  lies  beneath  the  pectoralis  major.  It 
arises  from  the  outer  surface  of  the  third,  fourth,  and  fifth  ribs  and  from  the  fascia 
covering  the  intervening  intercostal  muscles,  and  passes  obliquely  upward  and  later- 
ally to  be  inserted  into  the  coracoid  process  of  the  scapula. 

Nerve-Supply. — By  branches  of  the  external  and  internal  anterior  thoracic 
nerves  from  the  seventh  and  eighth  cervical  and  first  thoracic  nerves. 

Action. — To  draw  the  lateral  angle  of  the  scapula  downward  and  forward  ;  if 
the  scapula  be  fixed,  to  raise  the  ribs  to  which  it  is  attached. 

Relations. — The  pectoralis  minor  is  completely  covered  by  the  pectoralis 
major.  It  covers  the  outer  surface  of  the  upper  ribs  and  their  intercostal  spaces,  and 
near  its  insertion  it  passes  over  the  middle  portion  of  the  axillary  vessels  and  the 
cords  of  the  brachial  plexus. 

3.   Subclavius   (Fig.  560). 

Attachments. — The  subclavius  is  an  almost  cylindrical  muscle  attached  at  one 
extremity  to  the  anterior  surface  of  the  first  costal  cartilage  and  at  the  other  to  the 
under  surface  of  about  the  middle  third  of  the  clavicle. 

Nerve-Supply. — By  a  special  nerve  from  the  brachial  plexus  from  the  fifth  and 
sixth  cervical  nerves. 

Action. — To  draw  the  outer  end  of  the  clavicle  downward  and  forward. 

Variations. — The  subclavius  seems  to  be  the  persistent  representative  of  a  group  of 
muscles  more  perfectly  developed  in  the  lower  mammals  and  especially  in  those  in  which  the 
clavicle  is  more  or  less  rudimentary.  Muscle-bands,  which  represent  portions  of  the  group 
normally  degenerated,  are  occasionally  found  in  man,  and  on  account  of  their  variable  relations 
have  been  described  under  various  names.  They  may  all  be  grouped,  however,  under  three 
terms,  the  sterno-chondro-scapularis,  the  scapulo-claviailaris,  and  the  sterno-clavicularis  (Le 
Double).  In  the  mammals  which  lack  a  clavicle — in  many  Ungulates,  for  example — a  strong 
muscle-band  passes  transversely  across  the  upper  part  of  the  thorax  from  the  sternum  and  first 
costal  cartilage  to  the  scapula.  This  is  the  sterno-chondro-scapularis,  and  it  occasionally  occurs 
in  man  as  a  band  arising  from  the  points  named,  or  from  either  one  of  them,  or  from  the  first 
rib,  and  inserting  into  the  coracoid  process  of  the  scapula. 

In  those  mammals  which  possess  a  rudimentary  clavicle,  such  as  the  Rodents,  only  the 
terminations  of  the  sterno-chondro-scapular  persist,  each  inserting  into  the  clavicle,  and  forming 


THE   SCAPULAR    MUSCLES. 


57i 


the  scapulo-clavicularis  and  the  sterno-clavicularis.  Each  of  these  may  occur  as  an  anomaly  in 
man,  the  sterno-clavicularis  appearing  under  various  forms,  and  passing  either  above,  behind, 
or  in  front  of  the  clavicle.  It  should  be  stated,  however,  that  there  is  a  possibility  that  some  of 
the  varieties  of  the  sterno-clavicularis  may  really  represent  persisting  portions  of  the  muscular 
sheet  which  has  given  rise  to  the  middle  layer  of  the  cervical  fascia  and  to  the  sterno-hyoid  and 
the  omo-hyoid  (page  545). 

In  the  lower  mammals  a  thin  muscular  sheet  invests  a  greater  or  less  portion  of  the  trunk 
in  intimate  association  with  the  integument,  resembling  in  this  respect  the  platysma.  It  is 
termed  the  panniculus  carnosus,  and  in  man  is  normally  unrepresented.  Occasional  traces  of 
it  are  found,  however,  and  of  these  the  most  frequent  is  the  muscle  of  the  axillary  arch,  a 
somewhat  variable  band  of  muscle-tissue  which  passes  across  the  anterior  portion  of  the  axillary 
cavity  from  the  lateral  border  of  the  latissimus  dorsi  to  the  tendon  of  the  pectoralis  major.  It 
presents  considerable  variation  in  its  insertion,  being  connected  sometimes  with  the  biceps,  the 
coraco-brachialis,  the  pectoralis  minor,  or  the  chondro-epitrochlearis,  or  being  united  with  slips 
from  the  abdominal  portion  of  the  pectoralis  major,  or  being  inserted  into  the  coracoid  process 
of  the  scapula.     It  is  supplied  by  branches  from  the  anterior  thoracic  nerves. 

(6)   THE  POST-AXIAL   MUSCLES. 

1.  Serratus  magnus.  3.    Rhomboideus  minor. 

2.  Levator  anguli  scapulae.         4.    Rhomboideus  major. 

5.    Latissimus  dorsi. 

1.   Serratus  Magnus  (Fig.  558). 

Attachments. — The  serratus  magnus  (m.  serratus  anterior)  forms  a  large 
muscular  sheet  covering  the  lateral  wall  of  the  thorax.  It  arises  by  nine  or  ten 
fleshy  digitations  from  the  outer  surfaces  of  the  eight  or  nine  upper  ribs,  the  second 
rib  giving  attachment  to  two  slips.  Its  fibres  may  be  regarded  as  arranged  in  three 
groups  :  the  uppermost  group  consists  of  fibres  from  the  first  and  second  ribs  and  is 
inserted  into  the  ventral  surface  of  the  medial  angle  of  the  scapula  ;  the  middle  group, 
from  the  second  and  third  ribs,  is  inserted  into  the  ventral  surface  of  the  vertebral 
border  of  the  scapula  ;  while  the  remaining  fibres,  constituting  the  strongest  portion 
of  the  muscle,  converge  to  the  inferior  angle  of  the  same  bone. 

Nerve-Supply. — By  the  long  thoracic  nerve  from  the  fifth,  sixth,  and  seventh 
cervical  nerves. 

Action. — It  serves  to  keep  the  scapula  closely  applied  against  the  thoracic 
wall  and  draws  it  laterally.  Since  the  portion  inserted  into  the  inferior  angle  is  the 
strongest,  a  rotation  of  the  scapula  is  produced  whereby  its  lateral  angle  is  raised. 
By  this  action  the  serratus  plays  an  important  part  in  the  elevation  (abduction)  of 
the  arm,  since,  in  the  first  place,  by  fixing  the  scapula  it  allows  the  deltoid  to  expend 
all  its  action  on  the  humerus  instead  of  wasting  part  of  it  in  tilting  the  acromion 
downward,  and,  in  the  second  place,  after  the  deltoid  has  completed  its  action  and 
has  raised  the  arm  through  about  900,  the  further  elevation  through  another  right 
angle  is  accomplished  by  a  rotation  of  the  scapula  resulting  from  the  action  of  the 
serratus  magnus  and  trapezius. 

Variations. — Absence  of  a  portion  or  the  whole  of  the  muscle  has  been  observed.  Its 
origin  may  extend  as  low  as  the  tenth  rib,  and  it  may  receive  slips  from  the  transverse  processes 
of  the  cervical  vertebrae  and  from  the  levator  scapulae. 

2.   Levator  Anguli  Scapulae  (Fig.  559). 

Attachments. — This  (m.  levator  scapulae)  is  an  elongated  muscle  on  the  lateral 
surface  of  the  neck.  It  arises  from  the  transverse  processes  of  the  upper  four  cer- 
vical vertebras  and  passes  downward,  forward,  and  laterally  to  be  inserted  into  the 
medial  angle  and  outer  surface  of  the  vertebral  border  of  the  scapula  as  far  down  as 
the  base  of  the  spine. 

Nerve-Supply. — By  the  dorsal  scapular  nerve  from  the  fifth  cervical  nerve. 

Action. — To  draw  upward  the  medial  angle  of  the  scapula,  producing  a  rota- 
tion of  the  bone  contrary  to  that  effected  by  the  serratus  anterior.  If  the  scapula 
be  fixed,  the  action  is  to  bend  the  cervical  portion  of  the  spinal  column  laterally, 
rotating  it  slightly  to  the  opposite  side. 


572 


HUMAN   ANATOMY. 


Variations. — The  origin  may  extend  to  the  transverse  processes  of  all  the  cervical  ver- 
tebrae, and  may  be  continued  upon  the  mastoid  process  above  and  upon  the  upper  ribs  below. 
Slips  may  occur  connecting  the  levator  with  various  neighboring  muscles,  the  most  interesting 
of  these  connections  being  that  with  the  serratus  magnus,  since  comparative  anatomy  shows 
that  the  levator  was  primarily  continuous  with  that  muscle. 

A  separated  portion  of  the  outer  part  of  the  muscle  is  occasionally  inserted  into  the  outer 
end  of  the  clavicle,  forming  what  is  termed  the  levator  claviculcs. 


3.   Rhomboideus  Minor  (Fig.  559). 

Attachments. — The  rhomboideus  minor  is  a  band-like  muscle  which  arises 
from  the  lower  part  of  the  ligamentum   nuchae  and  from  the  spinous  process  of  the 

Fig.  558. 

Serratus  posticus  superi 


Superior  angle  of  scapul; 
Supraspinatus 
Coracoid  process 
Tendon  of  supraspinatus        \  \rf^ 

Acromion      ^jV^^^sE^^.!*' 
process — ^HWBBr^ 


Lesser_ 
tuberosity  of 
humerus 


Latissimus  dorsi,  cut  edge I 


Serratus  mag- 
nus,   upper, 
middle,  and 
por- 
tions 


Dissection  of  thoracic  wall,  showing  serratus  magnus  ;  clavicle  has  been 


ved  and  scapula  dr 


last  cervical  vertebra  and  passes  laterally  and  downward  to  be  inserted  into  the  ver- 
tebral border  of  the  scapula  at  the  base  of  the  spine. 

Nerve-Supply. — By  the  dorsal  scapular  nerve  from  the  fifth  cervical  nerve. 

Action. — To  draw  the  scapula  upward  and  medially,  at  the  same  time  rotating 
it  so  that  the  lateral  angle  is  moved  downward. 


4.   Rhomboideus  Major  (Fig.  559). 

Attachments. — The  rhomboideus  major  immediately  succeeds  the  rhom- 
boideus minor,  and  is  a  quadrilateral  sheet  which  arises  from  the  spinous  processes 
of  the  four  upper  thoracic  vertebra?   and  from   the  intervening  interspinous  liga- 


THE   SCAPULAR   MUSCLES. 
Fig    559. 


573 


Semispinals  capitis 
(complexus) 


Splenius  capitis  et 


Rhomboideus 
Supraspinatus^^^   .^-"T^r 


Levator  anguli  scapulse— TpM;i  f-V  jf 


'  C--  '     / 


Infraspinatus- 


Rhomboideus  major- 
Vertebral  aponeurosis 
Serratus  magnus 


w 


'^-—  Khombuideus  major 


-  Teres  major 


Latissimus  dorsi 


Aponeurosis  of  latissimus 
dorsi  (vertebral  aponeurosis) 


Gluteus  medius 


Gluteus  maximus- 


Superficial  muscles  of  the  hack. 


574  HUMAN    ANATOMY. 

ments.  It  is  directed  downward  and  laterally  and  is  inserted  into  the  lower  two- 
thirds  of  the  vertebral  border  of  the  scapula. 

Nerve-Supply. — By  the  dorsal  scapular  nerve  from  the  fifth  cervical  nerve. 

Action. — To  draw  the  scapula  upward  and  medially,  at  the  same  time  rotating 
it  so  that  the  lateral  angle  is  moved  downward. 

Variations  of  the  Rhomboidei. — The  rhomboidei  are .  sometimes  entirely  wanting,  and 
the  origins  of  both  muscles  may  be  extended  beyond  the  usual  limits. 

The  occipito-scapularis  is  a  muscle  occasionally  present  which  is  intimately  associated  in 
its  derivation  with  the  rhomboids.  It  arises  from  the  inner  part  of  the  superior  nuchal  line  and 
passes  downward  between  the  trapezius  and  splenius  to  join  the  rhomboideus  minor,  inserting 
with  it  into  the  vertebral  border  of  the  scapula. 

5.   Latissimus  Dorsi  (Fig.  559). 

Attachments. — The  latissimus  dorsi  is  a  large  triangular  muscle  which  arises 
from  the  spinous  processes  of  the  last  six  thoracic  vertebrae  and  the  intervening 
interspinous  ligaments  beneath  the  origin  of  the  trapezius,  from  the  lumbo-dorsal 
fascia,  from  the  posterior  portion  of  the  crest  of  the  ilium,  and  by  fleshy  digitations 
from  the  outer  surfaces  of  the  lower  three  or  four  ribs.  Its  fibres  pass  upward  and 
laterally  over  the  inferior  angle  of  the  scapula,  from  which  an  additional  slip  is  usu- 
ally added  to  the  muscle.  It  then  curves  around  the  lower  border  of  the  teres 
major  and  is  inserted,  ventrally  to  that  muscle,  into  the  crest  of  the  inner  tuberosity 
of  the  humerus.  A  mucous  bursa  {bursa  m.  latissimi  dorsi  )  lies  between  the  tendons 
of  insertion  of  the  latissimus  dorsi  and  teres  major. 

Nerve-Supply. — By  the  long  subscapular  nerve  from  the  seventh  and  eighth 
cervical  nerves. 

Action. — To  draw  the  humerus  downward,  backward,  and  inward,  at  the  same 
time  rotating  it  inward,  the  action  being  that  of  the  arm  in  swimming.  If  the 
humerus  be  fixed,  as  in  climbing,  it  draws  the  pelvis  and  lower  portion  of  the  trunk 
upward  and  forward. 

Variations. — The  latissimus  dorsi,  like  the  serratus  anterior  and  pectorales,  is  a  muscle 
which  has  migrated  extensively  from  the  region  of  its  first  formation,  the  lower  cervical  region, 
and  this  migration  can  be  witnessed  in  the  ontogeny  of  the  muscle.  Consequently  variations 
may  be  expected  and  do  occur  in  the  extent  of  the  origin  of  the  muscle,  whose  descent  and 
backward  migration  to  the  vertebral  column  may  be  interrupted  at  various  stages. 

A  great  amount  of  variation  of  this  nature  is  seen  in  its  attachment  to  the  crest  of  the  ilium. 
In  some  cases  this  attachment  extends  so  far  forward  as  to  meet  the  posterior  extremity  of  the 
attachment  of  the  external  oblique  of  the  abdomen,  but  usually  this  does  not  occur,  and  a  tri- 
angular interval,  known  as  the  triangle  of  Petit,  occurs  between  the  borders  of  the  two  muscles 
and  above  the  crest  of  the  ilium.  The  floor  of  the  triangle  is  formed  by  the  internal  obliquus 
abdominis,  and,  since  the  abdominal  wall  is  here  thinner  than  elsewhere,  the  triangle  may  occa- 
sionally be  the  seat  of  a  lumbar  hernia. 

Closely  allied  to  the  latissimus  dorsi  is  a  muscle,  the  m.  dorso-epitrochlearis,  which  occurs 
in  18  or  20  per  cent,  of  cases.  It  takes  its  origin  from  the  body  or  tendon  of  insertion  of  the 
latissimus  and  passes  to  the  brachial  fascia  or  to  the  medial  epicondyle  of  the  humerus.  It  has 
been  regarded  as  an  aberrant  portion  of  the  pectoralis  group  of  muscles,  but  its  supply  by  the 
musculo-spiral  nerve  places  it  among  the  post-axial  muscles. 

The  Axillary  Fascia. — The  axillary  fascia  is  a  firm  sheet  which  extends 
across  from  the  lower  border  of  the  pectoralis  major  to  that  of  the  latissimus  dorsi 
and  teres  major,  forming  the  floor  of  the  axilla.  Laterally  it  passes  over  into  the 
deep  fascia  of  the  arm,  medially  into  the  fascia  covering  the  serratus  magnus,  and 
near  the  border  of  the  pectoralis  major  it  has  inserted  into  it  the  downward  continu- 
ation of  the  fascia  which  encloses  the  pectoralis  minor  (Fig.  556).  It  is  pierced  by 
numerous  lymphatic  vessels,  and  along  its  medial  edge  is  considerably  thickened 
to  form  a  curved  band,  whose  concavity  is  directed  laterally,  and  which  stretches 
across  between  the  tendons  of  the  pectoralis  major  and  the  latissimus,  forming 
what  is  termed  the  axillary  arch.  Muscle-fibres  are  occasionally  found  in  this  arch 
(page  571). 

The  axilla  is  a  pyramidal  space  intervening  between  the  upper  part  of  the 
brachium  and  the  lateral  wall  of  the  thorax.      Its  apex  is  directed  upward  and  the 


THE    SHOULDER    MUSCLES.  575 

base,  which  is  formed  by  the  axillary  fascia,  downward.  Its  ventral  wall  is  formed 
by  the  pectoralis  major  and  pectoralis  minor,  its  dorsal  wall  by  the  latissimus  dorsi, 
teres  major,  and  subscapularis,  and  its  medial  wall  by  the  serratus  magnus.  In  the 
angle  formed  by  the  junction  laterally  of  its  ventral  and  dorsal  walls  lies  the  m.  coraco- 
brachialis,  and  in  the  groove  between  that  muscle  and  the  posterior  wall  are  the 
axillary  vessels  and  the  cords  of  the  brachial  plexus.  The  cavity  of  the  axilla  con- 
tains a  considerable  amount  of  fat  and  a  variable  number  of  lymphatic  nodes  ;  it  is 
traversed  by  the  thoracic  branches  of  the  axillary  vessels  and  by  the  intercosto- 
humeral  nerve,  and  the  long  thoracic  nerve  passes  downward  along  its  medial  wall  to 
the  serratus  magnus. 

THE  MUSCLES  PASSING  FROM  THE  PECTORAL  GIRDLE  TO 
THE  BRACHIUM. 

Pre-Axial.  Post-Axial. 

1.    Coraco-brachialis.  1.  Supraspinatus.        4.   Teres  major. 

2.  Infraspinatus.  5.    Subscapularis. 

3.  Teres  minor.  6.    Deltoideus. 

(a)    THE  PRE-AXIAL  MUSCLES. 
1.    Coraco-Brachialis  (Figs.  560,  570). 

Attachments. — The  coraco-brachialis  arises  from  the  tip  of  the  coracoid  pro- 
cess of  the  scapula  by  a  tendon  common  to  it  and  the  short  head  of  the  biceps.  It 
extends  downward  along  the  humerus  and  is  inserted  at  about  the  middle  of  its 
medial  border. 

Nerve-Supply. — By  the  musculo-cutaneous  nerve  from  the  seventh  cervical 
nerve. 

Action. — To  draw  the  upper  arm  forward. 

Relations.— It  is  crossed  ventrally  by  the  pectoralis  major,  and  dorsally  it  is  in 
relation  with  the  tendons  of  the  latissimus  dorsi,  the  teres  major,  and  the  subscapu- 
laris, from  the  last  of  which  its  tendon  is  separated  by  a  mucous  bursa  {bursa  m. 
coraco-brachialis').  Laterally  the  muscle  is  in  contact  with  the  short  head  of  the 
biceps.  It  is  usually  pierced  by  the  musculo-cutaneous  nerve,  and  is  in  relation 
medially  with  the  axillary  artery  and  the  median  and  ulnar  nerves. 

Variations. — Comparative  anatomy  shows  that  the  coraco-brachialis  is  primarily  an  ex- 
tensive muscle  consisting  of  three  portions,  of  which  only  the  middle  one  and  a  part  of  the 
inferior  are  normally  present  in  man.  The  variations  which  occur  usually  consist  in  the 
appearance  of  one  or  other  of  the  missing  portions.  Thus  the  upper  portion  is  sometimes 
represented  by  a  coraco-brachialis  superior,  which  arises  from  the  coracoid  process  and  passes 
laterally  to  be  inserted  into  the  lesser  tuberosity  of  the  humerus  or  into  the  capsule  of  the 
shoulder-joint,  while  the  lower  portion  may  be  more  completely  represented  by  the  insertion 
of  the  muscle  extending  as  far  down  as  the  medial  epicondyle  of  the  humerus. 

(b)    THE  POST-AXIAL  MUSCLES. 
1.    Supraspinatus  (Fig.  561). 

Attachments. — The  supraspinatus  occupies  the  supraspinous  fossa  of  the 
scapula,  arising-  from  the  inner  two-thirds  of  this  and  from  the  supraspinous  fascia. 
Its  fibres  pass  laterally  and  converge  to  a  tendon  which  is  inserted  into  the  upper  facet 
upon  the  greater  tuberosity  of  the  humerus  and  into  the  capsule  of  the  shoulder- 
joint. 

Nerve-Supply. — By  the  suprascapular  nerve  from  the  fifth  and  sixth  cervical 
nerves. 

Action. — To  abduct  the  arm. 

The  supraspinous  fascia  is  the  layer  of  connective  tissue  which  covers  the 
supraspinatus  muscle.  It  is  attached  to  the  superior  border  of  the  scapula  above,  to 
the  vertebral  border  medially,  to  the  spine  below,  and  gradually  fades  out  laterally. 


576 


HUMAN   ANATOMY. 


2.    Infraspinatus  (Figs.  561,  572). 

Attachments. — The  infraspinatus  occupies  the  infraspinous  fossa  of  the  scapula 
and  arises  from  the  entire  extent  of  the  fossa,  with  the  exception  of  a  portion 
towards  the  axillary  border  of  the  bone.  It  also  arises  from  the  infraspinous  fascia 
which  covers  it.  The  fibres  pass  laterally  and  converge  to  a  strong  tendon,  which 
is  frequently  separated  from  the  capsule  of  the  shoulder-joint  by  a  small  bursa  (bursa 


Fig.  560. 


Long  head  of  biceps 


Short  head  of  biceps 

Insertion  of 
pectoralis  major 


Subclavius 
Costo-coracoid  ligament 


Pectoralis  minor 


Serratus  magnus 


m.  infraspinati)  and  is  inserted  into  the  middle  facet  of 
the  greater  tuberosity  of  the  humerus. 

Nerve-Supply. — By  the  suprascapular  nerve  from 
the  fifth  and  sixth  cervical  nerves. 

Action. — When  the  arm  is  hanging  vertically,  it  is 
the  chief  outward  rotator  of  the  humerus.  When  the 
arm  is  abducted  to  a  horizontal  position,  the  muscle 
draws  it  backward. 

Variations. — The  upper  portion  of  the  muscle  is  sometimes 
distinctly  separated  from  the  rest,  and  has  been  termed  the 
infraspinatus  minor.  On  the  other  hand,  the  separation  which 
usually  exists  between  the  infraspinatus  and  the  teres  minor  may 
be  entirely  wanting. 

The  infraspinous  fascia  is  a  strong  fascia  which  covers 
the  infraspinatus  and  the  teres  minor,  giving  origin  to 
some  of  the  fibres  of  both  muscles.      It  is  attached  above 

to  the  spine  of  the  scapula,  medially  to  its  vertebral  border,  and  fades  out  laterally 

into  the  brachial  fascia. 

3.    Teres  Minor  (Fig.  561). 
Attachments.— The  teres  minor  arises  from  the  upper  two-thirds  of  the  dorsal 
surface  of  the  scapula,  close  to  its  axillary  border,  and  from  the  infraspinous  fascia. 


THE    SHOULDER    MUSCLES. 


577 


It  passes  laterally  along  the  lower  border  of  the  infraspinatus  to  be  inserted  into  the 
capsule  of  the  shoulder-joint  and  into  the  lower  facet  of  the  greater  tuberosity  of  the 
humerus. 

Nerve-Supply. — By  the  circumflex  nerve  from  the  fifth  and  sixth  cervical 
nerves. 

Action. — When  the  arm  is  vertical,  it  rotates  the  humerus  outward  ;  when  it 
is  horizontal,  it  draws  it  backward. 


Supraspinatus 


Spine  of- 
scapula 


Sectional  surface  of 
upraspinatus 


'  Greater  tuberosity 


'■ Teres  minor 


Quadrilateral  space 
Tendon  of  latissimus  dorsi 


Triangular  space 
__i___Long  (middle)  head  of 
triceps 
Outer  head  of  triceps 


— r^-r—       —   —Triceps 

I'. 


!     I 


Posterior  scapular  muscles  and  part  of  triceps ;  outer  part  of  ; 


lion  has  been  removed. 


4.  Teres  Major  (Figs.  561,  572). 

Attachments. — The  teres  major  arises  from  the  dorsal  surface  of  the  scapula, 
along  the  lower  third  of  its  axillary  border,  and  passes  laterally  to  be  inserted  into  the 
crest  of  the  lesser  tuberosity  of  the  humerus  immediately  dorsal  to  the  insertion  of 
the  latissimus  dorsi. 

Nerve-Supply. — By  the  lower  subscapular  nerve  from  the  fifth  and  sixth  cervi- 
cal nerves. 

Action.— To  draw  the  arm  backward  and  medially,  at  the  same  time  rotating  it 
inward. 

Relations.— The  teres  major  is  in  relation  below  with  the  latissimus  dorsi,  which 
bends  around  its  under  surface  so  as  to  lie  ventral  to  it  at  its  insertion.  Above  it  is 
in  relation  with  the  teres  minor  at  its  origin,  but  separates  from  it  as  it  passes  later- 

37 


578  HUMAN    ANATOMY. 

ally,  so  that  a  triangular  interval,  the  base  of  which  is  the  humerus,  lies  between 
the  two  muscles.  This  interval  is  crossed  by  the  long  head  of  the  triceps,  which 
overlies  the  dorsal  surface  of  the  teres  major,  and  is  thus  divided  into  a  more  medial 
triangular  space,  occupied  by  the  dorsal  scapular  artery,  and  a  more  lateral  quad- 
rangular space,  through  which  the  posterior  circumflex  vessels  and  the  circumflex 
nerve  pass. 

Variations. — Considerable  variation  occurs  in  the  size  of  the  teres  major,  an  increase  in 
the  size  of  that  muscle  being  associated  with  a  diminution  of  that  of  the  latissimus  dorsi,  and  vice 
versa.     The  teres  major  is,  indeed,  to  be  regarded  as  fundamentally  a  portion  of  the  latissimus. 

5.    Subscapulars  (Fig.  558). 

Attachments. — The  subscapularis  is  a  powerful  muscle  occupying  the  ventral 
(costal)  surface  of  the  scapula.  It  arises  from  the  whole  of  that  surface,  with  the  ex- 
ception of  a  small  portion  near  the  neck  of  the  bone,  some  fibres  also  taking  origin 
from  the  subscapular  fascia.  The  fibres  pass  laterally,  converging  to  a  strong  tendon 
which  is  inserted  into  the  lesser  tuberosity  of  the  humerus  and  to  a  certain  extent  into 
the  capsule  of  the  shoulder-joint. 

Nerve-Supply. — By  the  upper  and  lower  subscapular  nerves  from  the  fifth 
and  sixth  cervical  nerves. 

Action. — When  the  arm  is  vertical,  the  subscapularis  acts  as  a  powerful  inward 
rotator  of  the  humerus  ;  when  the  arm  is  abducted  to  a  right  angle  with  the  body, 
the  muscle  serves  to  draw  it  forward. 

Relations. — The  subscapularis  forms  a  considerable  portion  of  the  dorsal  wall 
of  the  axilla,  and  is  in  relation,  by  its  ventral  surface,  with  the  axillary  vessels  and  the 
cords  of  the  brachial  plexus,  and  laterally  with  the  coraco-brachialis  and  short  head  of 
the  biceps.  Its  lower  border  is  in  contact  with  the  teres  major  and  with  the  dorsal 
scapular  vessels  and  the  circumflex  nerve.  Dorsally  it  is  in  contact  with  the  long 
head  of  the  triceps,  and  is  separated  from  the  neck  of  the  scapula  by  the  large 
subscapular  bursa  (bursa  m.  subscapularis)  which  frequently  is  continuous  with  the 
synovial  cavity  of  the  shoulder-joint. 

Variations. — The  subscapularis  differentiates  in  the  embryo  from  the  same  sheet  which 
gives  rise  to  the  teres  major  and  the  latissimus  dorsi.  It  is  occasionally  divided  into  two  or 
more  fasciculi,  and  sometimes  there  is  separated  from  its  lower  portion  a  small  muscle,  termed 
the  subscapularis  minor,  which  arises  from  the  axillary  border  of  the  scapula  and  is  inserted  into 
the  crest  of  the  lesser  tubercle  of  the  humerus  and  sometimes  into  the  capsule  of  the  shoulder- 
joint. 

The  subscapular  fascia  is  a  firm  sheet  of  connective  tissue  which  covers  the 
ventral  surface  of  the  subscapularis.  It  is  attached  above,  medially,  and  below  to  the 
border  of  the  scapula  and  fades  out  laterally  into  the  brachial  fascia. 

6.   Deltoideus  (Fig.  562). 

Attachments. — The  deltoid  is  a  large  triangular  muscle  which  covers  the 
shoulder  as  with  a  pad.  It  arises  from  the  ventral  border  of  the  outer  third  of  the 
clavicle  and  from  the  acromion  process  and  lower  border  of  the  spine  of  the  scapula. 
Its  fibres  pass  downward,  and  converge  to  be  inserted  into  the  deltoid  tubercle  of  the 
humerus.  Where  the  muscle  passes  over  the  greater  tuberosity  of  the  humerus  a 
mucous  bursa  (bursa  subdeltoidea )  is  interposed  between  it  and  that  prominence. 

Nerve-Supply. — By  the  circumflex  nerve  from  the  fifth  and  sixth  cervical 
nerves. 

Action. — To  abduct  the  arm  to  a  position  at  right  angles  to  the  body.  Fur- 
ther abduction  is  accomplished  by  a  rotation  of  the  scapula  by  the  contraction  of 
the  trapezius  and  the  serratus  anterior,  whereby  the  lateral  angle  of  the  bone  is  tilted 
upward. 

Relations. — The  deltoid  is  in  relation  by  its  deep  surface  with  the  coracoid 
process  and  the  capsule  of  the  shoulder-joint  and  with  the  various  muscles  attached 
to  or  in  the  neighborhood  of  these  structures.  The  cephalic  vein  passes  upward 
alonsr  its  anterior  border. 


PRACTICAL    CONSIDERATIONS  :    AXILLA    AND    SHOULDER.     579 

Variations. — The  portion  of  the  deltoid  which  arises  from  the  clavicle  is  subject  to  con- 
siderable variation,  either  being  greatly  reduced  in  size  or  even  entirely  suppressed,  or  else 
being  more  extensively  developed  than  usual,  so  that  it  is  in  contact  or  even  fused  with  the 
clavicular  portion  of  the  pectoralis  major.  It  may  also  be  distinctly  separated  from  the  remain- 
der of  the  muscle,  and  not  infrequently  a  separation  of  the  acromial  and  spinal  portions  may 
also  occur,  so  that  the  muscle  becomes  three-headed. 

Fig.  562. 


-Sternocleidomastoid 


/  7     ';    ■'..•;.  ■  ,-.'  '.      ■.'.'<■  Pectoralis  major 

Deltoid,  spinal  portion-    

--     -    -  DeHtiM,  clavicular 

portion 


Deltoid,  acromial  porti* 


Accessory  bundles  of  fibres  are  occasionally  found  arising  from  the  fascia  infraspinata  or 
from  some  point  along  the  axillary  border  of  the  scapula,  and  either  insert  with  the  deltoid 
(m.  basio-deltoidens\  or  join  with  the  upper  part  of  the  muscle,  being  continued  onward  as 
tendinous  fibres  which  pass  to  the  acromion  process  and  lateral  extremity  of  the  clavicle  (m. 
costo-deltoideus) .  These  fibres  represent  a  portion  of  the  deltoid  which  in  the  anthropoid  apes 
arises  from  the  borders  of  the  scapula  and  in  some  of  the  lower  mammals  forms  a  distinct 
muscle. 

PRACTICAL   CONSIDERATIONS  :    THE   MUSCLES   AND    FASCIA   OF 
THE   AXILLA   AND   SHOULDER. 

The  practical  relations  of  the  fascia  descending  to  the  superior  borders  of  the 
clavicle  and  scapula  have  been  sufficiently  described  (page  551). 

Fracture  of  the  Clavicle. — The  action  of  the  muscles  which  move  the  arm  and 
shoulder  and  of  those  attached  to  the  clavicle  (page  259)  should  be  considered  with 
reference  to  the  common  form  of  displacement  in  cases  of  fracture  of  the  latter  bone. 

The  acromial  fragment,  as  it  moves  with  the  shoulder,  is  the  more  markedly 
affected.  It  is  carried  downward  by  gravity  acting  on  the'  upper  extremity  and 
aided  by  the  two  pectoral  muscles  and  the  latissimus  dorsi.      It  is  drawn  inward  by 


58o 


HUMAN    ANATOMY. 


the  sternal  fibres  of  the  pectoralis  major  and  by  all  the  muscles  passing  from  the 
trunk  to  the  humerus  and  scapula.  It  is  rotated  on  a  vertical  axis  so  that  its  inner 
end  points  backward  and  its  outer  end  forward.  The  cause  of  the  rotation  is  the 
action  of  the  two  pectorals  upon  the  shoulder  and  the  contraction  of  the  serratus, 
which-  (the  support  of  the  clavicle  having  been  removed)  draws  the  scapula  (and 
with  it  the  point  of  the  shoulder)  inward  and  forward  instead  of  more  directly  for- 
ward, and  so  causes  an  anterior  projection  of  the  acromial  end  of  the  outer 
fragment. 

Theoretically  the  inner  fragment  is  displaced  upward  by  the  clavicular  fibres  of 
the  sterno-mastoid,  but  this  action  is  so  strongly  resisted  by  the  costo-clavicular 
(rhomboid)  ligament  and  by  the  upper  and  inner  fibres  of  the  pectoralis  major,  as 
well  as  by  the  subclavius,  that  it  is  not  often  productive  of  much  deformity  (Fig.  563). 
The  rationale  of  the  good  effect  of  recumbency  with  the  head  slightly  elevated 
is  evident.  The  weight  of  the  upper  extremity  ceases  to  drag  the  outer  fragment 
downward.  The  vertebral  border  of  the  scapula  is  pressed  closely  to  the  thorax 
by  the  weight  of  the  trunk.  Its  outer  border,  therefore,  cannot  be  drawn  forward  by 
the  pectorals  and  serratus,  but  tends  to  fall  backward  and  outward,  correcting  both 

the  rotation    and    the    inward 
Fig.  563.  displacement.      The  slight  ele- 

vation of  the  head  relaxes  the 
sterno-cleido-mastoid  and  re- 
moves whatever  influence  it 
may  have  in  raising  the  outer 
end  of  the  inner  fragment. 

Fractures  within  the  limits 
of  the  rhomboid   ligament   at 
the  inner  end  or  within  those 
i  of   the  conoid   and    trapezoid 

ligaments  at  the  outer  end  are 
attended  by  but  little  displace- 
subciavius     ment. 

artela'y  Fractures    of  the  scapula 

Axillary  have  already  been  dealt  with 
pectoralis  (Page254)-  Muscular  action 
Deltoid  influences  them  but  little  be- 
yondwhat  has  been  mentioned. 
The  fascia  beneath  and 
connected  with  the  clavicle  is 
of  much  surgical  importance. 
The  superficial  fascia  of  the 
thorax  splits  to  enclose  the  breast.  The  processes  which  pass  from  it  to  the  skin 
(Cooper's  "  ligamenta  suspensoria" ),  by  their  involvement  and  contraction  in 
carcinoma,  produce  the  characteristic  adhesion  and  dimpling  of  the  skin. 

The  deep  pectoral  fascia  splits  to  form  the  sheath  of  the  pectoralis  major  muscle. 
Carcinoma  of  the  mamma  will  usually  be  found  adherent  to  this  layer  on  the  anterior 
surface  of  the  muscle.  Such  adhesion  can  best  be  demonstrated  by  attempting  to 
move  the  tumor  and  breast  in  the  direction  of  the  pectoral  fibres.  Motion  trans- 
verse to  that  line  may,  even  in  cases  in  which  the  tumor  and  muscle  are  inseparably 
connected,  appear  to  be  free,  because  the  muscle  itself  is  moved  on  the  subjacent 
structures. 

Beneath  the  deep  pectoral  fascia  an  additional  sheet,  the  clavi-pectoral  fascia, 
extends  as  a  continuation  downward  of  the  sheath  of  the  subclavius,  the  two  layers 
of  which  begin  above  at  the  two  lips  of  the  subclavian  groove  on  the  inferior  surface 
of  the  clavicle  and  unite  into  one  layer  at  the  lower  edge  of  the  subclavius.  This 
layer  is  continuous  towards  the  sternum  with  the  deep  fascia  covering  in  the  first  and 
second  intercostal  spaces  ;  externally  it  is  attached  to  the  coracoid  process  ;  interiorly, 
after  splitting  to  enclose  the  pectoralis  minor  muscle,  it  blends  with  the  axillary  fascia. 
The  portion"  of  the  clavi-pectoral  fascia  above  the  upper  border  of  the  pectoralis 
minor  is  known  as  the  costo-coracoid  membrane.      It,  together  with  the  subclavius 


■ .   ...  ■-.  ^ 

"t^.     Brachial  plexu 

-  ,    .  M\ 

-  \  '  '" 

Dissection  of  fracture  of  middle  of  clavicle. 


PRACTICAL    CONSIDERATIONS  :    AXILLA   AND    SHOULDER.     581 


muscle  (which  it  invests),  forms  the  floor  of  the  so-called  superficial  infraclavicular 
triangle,  the  roof  of  which  is  made  by  the  clavicular  fibres  of  the  great  pectoral,  the 
base  by  the  anterior  fibres  of  the  deltoid,  the  upper  side  by  the  sternal  half  of  the 
clavicle,  and  the  lower  side  by  a  line  parallel  to  the  uppermost  sternal  fibres  of  the 
great  pectoral.  Its  apex  is  at  the  sterno-clavicular  angle  of  junction.  The  floor  of 
this  space  is  pierced  by  the  external  anterior  thoracic  nerve,  the  acromio-thoracic 
vessels,  and  the  cephalic  vein  (Fig.  556).  Fat  containing  a  few  lymphatic  glands, 
often  involved  in  carcinoma  of  the  breast,  is  found  there.  It  is  closed  in  above  by 
the  clavicle,  but  is  continuous  below  with  the  space  between  the  two  pectoral  muscles 
down  to  the  level  where  the  superficial  layer  of  the  deep  fascia  and  the  clavi-pectoral 
fascia  (which  has  invested  the  pectoralis  minor  and  continued  downward  as  a  single 
layer  again)  unite  at  the  lower  border  of  the  pectoralis  major  to  form  the  axillary 
fascia.  Effusions  of  blood  or  collections  of  pus  occupying  this  space  between  the  two 
muscles  are  therefore  prevented  from  passing  upward  by  the  clavicle,  forward  by  the 
pectoralis  major,   and  backward  by  the  clavi-pectoral  fascia  and  pectoralis  minor. 


Humeral  br; 


ich  of  acromio-thora 
Pectoralis  minor 


Fig.  564. 


Pectoralis  major 
distal  stump 


Cut  edge  of 

superficial  pec- 
toral fascia 


Cut  edge  of  superficial  lay 
clavi-pectoral  fascia 


Teres  major  covered  by  axillary  fascia 


Dissection  of  thoracic  wall ;  pectoralis 


been  partly 


xposing  deep  layer  of  clavi-pectoral 


Consequently  they  are  apt  to  approach  the  surface  near  the  anterior  axillary  margin 
or  in  the  groove  between  the  great  pectoral  and  deltoid, — i.e.,  at  either  the  lower 
border  of  the  sternal  portion  of  that  muscle  or  the  upper  border  of  its  clavicular  fibres. 
Beneath  the  costo-coracoid  membrane  is  a  region  described  as  the  deep  infra- 
clavicular triangle.  Although  continuous  with  the  axilla,  this  space  is  conveniently 
studied  as  a  separate  region  on  account  of  the  important  structures  which  it  contains 
and  the  frequency  with  which  it  is  invaded  by  disease.  Its  floor  is  formed  by  the 
first  and  second  ribs  and  the  intercostal,  serratus  magnus,  and  subscapularis  muscles. 
Its  apex  is  at  the  angle  made  by  the  line  of  the  upper  border  of  the  small  pectoral 
and  that  of  the  clavicle  at  the  coracoid  process,  those  two  lines  constituting  its  sides. 
The  base  is  towards  the  sternum  at  the  line  where  the  costo-coracoid  membrane  is 
fused  with  the  deep  fascia  over  the  upper  intercostal  spaces.  Through  this  triangle 
pass  the  axillary,  superior  thoracic,  and  acromio-thoracic  vessels,  the  cephalic  vein, 
the  external  and  internal  anterior  thoracic  and  long  thoracic  nerves,  and  the  brachial 
plexus.      It  contains  fat,  with  numerous  lymphatic  glands  and  vessels.      It  is  obvious 


582  HUMAN   ANATOMY. 

that  it  is  continuous  above  with  the  neck  and  inferiorly  with  the  axilla.  The  latter 
space  is  shut  in  below  by  the  continuation  of  the  axillary  fascia  from  the  lower  bor- 
der of  the  pectoralis  major  backward  to  the  latissimus  dorsi,  outward  to  the  deep 
fascia  of.  the  arm,  and  inward  to  the  deep  fascia  of  the  thorax. 

Abscess  or  effusion  of  blood,  as  its  progress  in  all  these  directions  is  resisted, 
may  therefore  point  in  the  neck,  following  the  vessels  and  the  trunks  of  the  plexus 
up  from  the  axilla  through  the  deep  infraclavicular  triangle,  to  make  its  appearance 
above  the  clavicle. 

The  skin  over  the  fascia  at  the  base  of  the  axilla  is  thin  and  richly  supplied 
with  hair-follicles  and  with  sebaceous  and  sudoriparous  glands  ;  hence  superficial 
infections  are  frequent  and  secondary  glandular  abscesses  are  common.  The  con- 
nective tissue  of  the  axillary  space  is  loose  and  abundant,  permitting  of  free  motion 
of  the  arm,  but  also  favoring  the  occurrence  of  large  collections  of  blood  or  of  pus. 


Fig.  565. 


Fig.  566. 


Acron 
process 


Acromior— ^Jg|g« 

Coracoid   <&"S 
process         \  /  ^ 

Glenoid  _J 
cavity- 
Head  c 
humerus 


~:k 


ulder  of  subject  i 
is  been  produce 


The  fascia  over  the  scapular  muscles — supraspinous  and  infraspinous  fascia — 
has  already  been  described  in  reference  to  caries,  necrosis,  and  abscess  (pages 
255>  279). 

Dislocation  of  the  Shoulder- Joint. — The  circumstances  that  favor  or  resist  dislo- 
cation of  the  shoulder-joint  have  been  enumerated  ("pages  278,  279),  but  the  ana- 
tomical symptoms  of  that  lesion  may  now  be  considered  with  especial  reference  to 
the  muscles  involved.  Shoulder  dislocation  is  either  subglenoid  or  subcoracoid  in 
the  vast  majority  of  cases,  the  former  being  almost  invariably  the  primary  form,  for 
reasons  previously  given  (page  278'). 

A  luxation,  subglenoid  primarily,  usually  becomes  subcoracoid  from  the  con- 
tinuance of  the  force  producing  it,  aided  strongly  by  the  pectoralis  major  ;  hence 
the  subcoracoid  is  the  most  common.  The  subclavicular,  in  which  the  head  passes 
farther  inward  and  lies  on  the  second  and  third  ribs  beneath  the  pectoralis  major, 


PRACTICAL    CONSIDERATIONS  :    AXILLA    AND    SHOULDER.     583 

and  the  supracoracoid ,  In  which,  owing  to  fracture  of  the  coracoid  or  the  acromion, 
the  head  is  displaced  upward,  are  so  uncommon  that  they  need  merely  be  mentioned 
here.  The  backward  (subspinous)  luxation  is  resisted  so  strongly  by  the  subscapu- 
laris,  and  especially  by  the  long  head  of  the  triceps,  that  it  also  is  a  surgical  rarity. 

In  the  subglenoid  and  subcoracoid  varieties  (Figs.  565,  566)  it  will  be  found  : 
1.  That  the  normal  curve  of  the  shoulder  is  replaced  by  a  straight  line,  because  of 
(<z)  the  absence  of  the  head  of  the  bone  and  the  tuberosities  beneath  the  deltoid  ; 
(6)  the  stretching  of  that  muscle.  2.  For  the  same  reasons  it  will  be  found  that 
(a)  a  ruler  applied  to  the  outer  side  of  the  arm  will  touch  both  the  acromion  and  the 
external  condyle  at  the  same  time  (Hamilton)  ;  and  (d)  the  edge  of  the  acromion  is 
unnaturally  prominent,  while  beneath  it  is  a  palpable  depression  instead  of  the  nor- 
mal resistance  of  the  tuberosities.  3.  The  elbow  is  abducted  because  of  the  tension 
of  the  deltoid.  4.  The  forearm  is  flexed  on  account  of  the  tension  of  the  biceps. 
5.  The  vertical  measurement  of  the  axilla 

is  increased  (Callaway),  because  of  («)  Fi  0^567. 

the  presence  of  the  head  or  upper  por- 
tion of  the  shaft  in  the  line  of  meas- 
urement ;  and  (/>)   the  lowering  of  the 

axillary  folds  (Bryant),   the   insertions  \ 

of   the  pectoralis  major  and  latissimus      Acromion-; 

dorsi  being,   of  course,   carried    down-  \'s   >m\\  \ 

ward  with  the  humerus.     6.   The  elbow        Head  of—  vk'%  V 
cannot  be  made  to  touch  the  chest-wall      ,umerus 

while  the  hand   is  placed  ontheopp<>-  ''  '""  '  ..'  .' 

site  shoulder  (Dugas ),  because  the  head  i  ■  major 

of  the  bone  is  held  in  contact  with  that  :.  SHJ 

wall  by  the  tense  muscles  and  overlying 
structures,  and  its  lower  extremity — 
the  other  end  of  a  straight,  inflexible 
axis — cannot  be  made  at  the  same  time         .  • :,  ,    j;  . 

to  touch  at  a  second  point  the  curve  ««ps-J 
represented  by  the  wall  of  the  thorax. 
7.  There  is  rigidity  because  of  the  ten- 
sion or  spasm  of  the  muscles  moving 
the  humerus,  especially  of  the  sub- 
scapularis,  the  deltoid,  the  supra-  and 
infraspinatus,  the  biceps,  and  the  coraco- 
brachialis.     8.    In  the  subcoracoid  luxa-  t 

tion  the  prominence  of  the  head  may  be  :, 

felt  beneath  the  coracoid  or  outer  third 
of  the  clavicle  where  it  lies,  the  anatom- 
ical neck  resting  on  the  anterior  border       "^howti  „ 
of  the  glenoid  cavity.      There  is  a  little 

real  lengthening, — i.e.,  the  distance  between  the  glenoid  surface  and  the  lower  end 
of  the  humerus  must  be  increased, — but  this  may  be  converted  into  apparent  short- 
ening by  abduction,  which  approximates  the  tip  of  the  acromion  and  the  external 
condyle.  9.  In  the  subglenoid  variety  the  head  may  be  felt  low  in  the  axilla,  the 
anterior  wall  of  which  is  widened.  It  rests  on  the  upper  part  of  the  outer  border  of 
the  scapula  just  below  the  glenoid  cavity.  Lengthening  is  apt  to  be  marked,  and, 
when  the  arm  is  adducted  somewhat,  may  exceed  an  inch.  The  stretching  and 
"hollow  tension"  of  the  deltoid  and,  therefore,  the  abduction  of  the  arm  are 
marked.  10.  There  is  usually  (a)  pain  from  direct  pressure  upon  or  from  stretch- 
ing of  the  brachial  plexus,  and  frequently  (b)  cedema  from  similar  involvement  of 
the  axillary  vessels. 

In  all  luxations,  but  especially  in  the  subglenoid  and  subspinous,  the  circumflex 
nerve  is  apt  to  be  injured  ;  hence  obstinate  paresis  or  paralysis  of  the  deltoid  is  a 
not  infrequent  sequel. 

In  all  methods  of  reduction  of  shoulder  luxations  the  humerus  is  used  as  a 
lever,  and  in  all  it  is  desirable  to  secure  fixation  of  the  scapula  by  means  of  (a)  the 


5§4 


HUMAN    ANATOMY. 


weight  of  the  trunk  in  the  supine  and  recumbent  position  ;  (b)  pressure  on  the 
acromion  and  clavicle  ;  (c)  the  use  of  a  folded  sheet  placed  high  in  the  axilla,  so 
that  it  presses  upon  the  axillary  border  in  front  and  the  dorsum  posteriorly  when 
the  two  ends  are  carried  across  the  body  and  made  taut  ;  or  (d  )  by  dragging  on 
the  opposite  arm,  "which,  by  making  tense  the  trapezius  of  the  opposite  side,  pro- 
vokes contraction  of  the  muscle  on  the  injured  side"  (Makins). 

The  use  of  the  heel  or  foot  in  the  axilla  as  a  fulcrum  while  manual  extension  is 
made — the  long  arm  of  the  lever,  the  shaft  of  the  humerus,  being  carried  inward  so 
as  to  move  the  short  arm,  the  head,  outward — requires  no  anatomical  explanation. 

Kocher's  method  (applicable  especially  to  subcoracoid  luxation)  is  more  com- 
plex in  its  mode  of  action.  There  is  some  difference  of  opinion  as  to  its  exact 
mechanism,  but  it  is  safe  to  say  that  in  its  various  stages  it  acts  approximately  as 
follows,  i.  The  elbow  is  flexed,  relaxing  the  biceps,  and  the  arm  is  pressed  closely 
to  the  side,  making  tense  the  untorn  posterior  portion  of  the  capsule  extending 
between  the  posterior  lip  of  the  glenoid  fossa  and  the  under  and  back  part  of  the 

neck    of    the    humerus.      This 


Fig.  568. 


.Axillary 
vessels 

Displaced 
head  of 


portion  of  the  capsule  and  the 
tendons  of  the  posterior  scapu- 
lar muscles  are  drawn  tightly 
across  the  glenoid  fossa.  2. 
The  arm  is  rotated  outward 
until  the  forearm  is  parallel 
with  the  transverse  axis  of  the 
body,  the  hand  pointing  di- 
rectly outward.  This  rolls  the 
head  of  the  bone  outward  on 
the  tense  portion  of  the  cap- 
sule, which  is  partly  wound, 
as  it  were,  upon  the  neck,  and 
at  the  same  time  relaxes  the 
scapular  tendons  and  removes 
them  from  the  fossa.  3.  The 
elbow  is  raised  until  the  arm 
is  parallel  with  the  antero- 
posterior axis  of  the  body. 
This  relaxes  the  anterior  fibres 
of  the  deltoid,  the  coraco- 
brachialis,  and  the  upper  por- 
tion of  the  capsule,  and  perhaps 
widens  the  space  between  the 
margins  of  the  rent,  although 
no  obstacle  to  reduction  is  usu- 
ally met  with  there.  The  lower 
portion  of  the  capsule  is  still  tense.  4.  Rotation  inward  on  this  portion  as  a  fulcrum 
now  moves  the  articular  face  of  the  head  towards  the  comparatively  free  glenoid 
cavity  and  relaxes  the  subscapularis  ;  as  the  elbow  is  then  lowered  in  adduction  the 
lower  capsular  segment  relaxes  and  the  head  re-enters  through  the  rent  by  which  it 
originally  emerged.  These  details  can  be  worked  out  satisfactorily  in  experimental 
luxations  on  the  cadaver,  and  have  apparently  been  demonstrated  as  to  the  main 
points  by  Farabceuf,  Helferich,  and  others. 

Recurrent  or  "habitual  dislocation" — i.e.,  dislocation  occurring  from  trifling 
causes,  such  as  abduction  of  the  arm — may  be  a  remote  result  of  the  rupture  or  for- 
cible separation  of  the  tendons  of  the  supra-  and  infraspinatus  muscles  from  the  cap- 
sule of  the  joint,  with  rupture  of  the  capsule  at  its  upper  portion,  and  the  formation 
of  a  free  communication  between  the  joint-cavity  and  that  of  the  subcoracoid  bursa 
(Jossel,  quoted  by  Stimson).  It  is,  however,  usually  due  to  the  injury  to  the  capsule 
and  to  the  weakness  of  the  shoulder  muscles  resulting  from  the  original  accident. 

Bursa. — The  large  subacromial  .bursa  and  the  subdeltoid  bursa  have  been  de- 
scribed in  relation  to  their  possible  enlargements  (page  279).     The  subscapular  bursa 


Deeper  dissection  of  preceding  subcoracoid  luxation,  showing 
displacement  of  head  of  humerus  and  muscles  involved. 


THE    BRACHIAL    MUSCLES. 


585 


and  the  bursa  beneath  the  infraspinatus  often  communicate  with  the  shoulder-joint, 
and  disease  of  the  latter  may  spread  to  them. 

An  infraserratus  bursa  has  been  described  (Terrillon),  situated  between  the  infe- 
rior scapular  angle  and  the  chest-wall.  Its  enlargement  gives  rise  to  friction-like 
crepitation  or  creaking,  which  has  been  mistaken  for  fracture  of  ribs  or  scapula  or 
for  an  arthritis  of  the  shoulder.  Nancrede  says  that  this  symptom  is  due  to  (a)  an 
exostosis  on  the  ribs  or  scapula  which  has  caused  such  atrophy  of  the  subscapular 
and  serratus  magnus  muscles  as  to  allow  the  two  bony  surfaces  to  come  in  contact  ; 
or  (6)  a  localized  projection  of  the  ribs  due,  for  example,  to  a  post-pleuritic  con- 
traction of  the  chest,  and  with  the  same  muscular  atrophy  ;  or  (V)  a  primary  atrophy 
of  the  muscles,  as  in  ankylosis  of  the  scapulo-humeral  joint,  which  will  admit  of  the 
normal  scapula  and  ribs  becoming  apposed.  This  latter  condition  especially  causes 
increased  movements  of  the  scapula  over  the  thoracic  wall  and  favors  the  development 
of  this  bursa. 

THE    BRACHIAL    MUSCLES. 


Pre-Axial. 
Biceps 
Brachialis  anticus. 


Post-Axial. 

1.  Triceps. 

2.  Anconeus. 


The  brachial  group  includes  those  muscles  which  act  primarily  upon  the  fore- 
arm and  form  the  muscular  substance  of  the  arm.  Some  of  them,  however,  take 
origin  in  whole  or  in  part  from  the  pectoral  girdle  and  thus  have  some  effect  on  the 
movements  which  occur  about  the  shoulder-joint,  although  their  principal  action  is 
upon  the  forearm. 

The  Brachial  Fascia. — The  deep  layer  of  the  fascia  of  the  arm  forms  a  com- 
plete investment  of  the  muscles  of  the  brachial  region.  Above  it  passes  over  into 
the  thin  fascia  covering  the 

deltoid     muscle,     and     me-  Cephalic  vein  5   9'  Biceps 

dially  it  becomes  continu- 
ous with  the  axillary  fascia, 
while  below  it  is  continuous 
with  the  fascia  of  the  fore- 
arm, adhering  firmly  to  the 
periosteum  covering  the 
subcutaneous  portions  of 
the  humerus  and  the  ole- 
cranon process,  and  being 
reinforced  by  tendinous 
prolongations  from  the  bi- 
ceps and  triceps  muscles. 

From  its  lateral  and 
medial  surfaces  it  sends 
sheet-like  prolongations  in- 
ward to  be  attached  to  the 
humerus.  These  sheets, 
termed  the  intermuscular 
septa,  are  of  considerable 
strength  and  give  attach- 
ment to  adjacent  muscles. 
They  pass  to  the  humerus 

between  the  lateral  and  medial  borders  of  the  triceps  and  the  remaining  muscles  of  the 
arm,  and  it  is  to  be  noted  that,  while  the  medial  or  inner  septum  marks  the  boundary 
between  the  pre-axial  and  post-axial  muscles,  this  is  not  the  case  with  the  lateral  or 
external  septum.  In  the  lower  part  of  their  extent  the  septa  are  attached  to  the  supra- 
condylar ridges  of  the  humerus  and  terminate  at  the  condyles,  a  number  of  post-axial 
muscles  of  the  forearm  arising  from  the  outer  condyle  anterior  to  the  external  septum. 

A  number  of  subcutaneous  bursas  occur  between  the  integument  and  the  bra- 
chial fascia  in  those  regions  in  which  the  fascia  is  adherent  to  the  subjacent  perios- 
teum covering  so-called  subcutaneous  portions  of  the  skeleton.      Thus  there  is  a 


Superficial  fascia 
Deep  fascia 


External 

intermuscular 

septum 


Triceps,  outer  head 

Triceps,  middle  head 


586  HUMAN    ANATOMY. 

bursa  acromialis  over  the  acromion  process  of  the  scapula,  a  bursa  olecrani  over  the 
olecranon  process  of  the  ulna,  and  a  bursa  may  occur  over  each  condyle  of  the 
humerus. 

(a)  THE  PRE-AXIAL  MUSCLES. 

i.   Biceps  (Figs.  560,  570). 

Attachments. — The  biceps  (m.  biceps  brachii),  as  its  name  indicates,  takes 
origin  by  two  heads.  The  long  head  arises  from  the  upper  border  of  the  glenoid 
cavity  of  the  scapula  by  a  slender  round  tendon,  which  traverses  the  cavity  of  the 
shoulder-joint  invested  by  the  synovium  and  then  bends  downward  into  the  bicipital 
groove  (intertubercular  sulcus )  of  the  humerus,  accompanied  by  a  prolongation  of  the 
joint  capsule  (vagina  mucosa  iutertubercularis),  and  then,  becoming  muscular,  unites 
with  the  short  head,  which  arises  from  the  tip  of  the  coracoid  process  of  the  scapula 
in  common  with  the  coraco-brachialis.  By  the  union  of  the  two  heads  a  strong 
muscle  is  formed  which  descends  in  front  of  the  humerus  and  a  short  distance  above 
the  elbow-joint  passes  over  into  a  flat  tendon,  which  is  continued  downward  to  be 
inserted  into  the  tuberosity  of  the  radius,  a  mucous  bursa  (bursa  bicipitoradialis) 
being  interposed  between  the  anterior  surface  of  the  tuberosity  and  the  tendon. 
Some  of  the  fibres  of  the  muscle,  instead  of  passing  into  the  tendon,  are  continued 
into  a  flat  tendinous  expansion,  the  semilunar  ox  bicipital  fascia  ( lacertus  fibrosusj, 
which  passes  downward  and  medially  to  become  lost  in  the  fascia  of  the  forearm. 

Nerve-Supply. — By  the  musculo-cutaneous  nerve  from  the  fifth  and  sixth 
cervical  nerves. 

Action. — To  flex  the  forearm  on  the  brachium,  and  when  the  forearm  is  in  pro- 
nation to  supinate  it.  It  will  also  act  to  a  slight  extent  in  movements  of  the  arm  at 
the  shoulder-joint,  assisting  the  coraco-brachialis  in  drawing  the  arm  forward. 

Relations. — The  biceps  is  crossed  on  its  ventral  surface  by  the  tendon  of  the 
pectoralis  major  and  is  covered  above  by  the  lateral  portion  of  the  deltoid.  Deeply 
it  is  in  relation  with  the  humerus,  the  brachialis  anticus,  and  the  supinator.  Upon 
its  inner  side  lie  the  coraco-brachialis  above  and  below,  in  the  groove  between  it  and 
the  triceps  (sulcus  bicipitalis  medialis),  the  brachial  vessels,  and  the  median  nerve. 

Variations. — The  biceps  presents  numerous  variations.  Its  long  head  is  occasionally  want- 
ing, but  more  frequently  additional  heads  occur.  Of  these  the  most  frequent,  occurring  in  some- 
thing over  10  per  cent,  of  cases,  is  a  head  which  arises  from  the  medial  surface  of  the  humerus, 
between  the  insertions  of  the  deltoid  and  coraco-brachialis.  Other  heads  may  arise  from  the 
external  tuberosity  of  the  humerus  or  from  the  outer  border  of  that  bone,  between  the  deltoid 
and  brachio-radial  muscles. 

2.    Brachialis  Anticus  (Fig.  571). 

Attachments. — The  brachialis  anticus  (m.  brachialis)  occupies  the  anterior  sur- 
face of  the  lower  part  of  the  humerus  and  is  for  the  most  part  covered  by  the  biceps. 
It  arises  from  the  intermuscular  septa  and  the  anterior  surface  of  the  humerus  imme- 
diately below  the  insertion  of  the  deltoid,  which  it  partly  surrounds.  It  passes 
downward,  and  the  fibres  converge  to  a  short  tendon  which  is  inserted  into  the 
anterior  surface  of  the  coronoid  process  of  the  ulna. 

Nerve-Supply. — The  main  mass  of  the  muscle  is  supplied  by  branches  from 
the  musculo-cutaneous  nerve.  The  fibres  which  arise  from  the  lateral  intermuscular 
septum  and  are  covered  by  the  brachio-radialis  are  supplied  by  a  branch  from  the 
musculo-spiral  nerve.  The  nerve-fibres  come  in  both  cases  from  the  fifth  and  sixth 
cervical  nerves. 

Action. — To  flex  the  forearm. 

Variations. — The  nerve-supply  shows  the  brachialis  anticus  to  be  a  composite  muscle  the 
major  portion  of  which  is  derived  from  the  pre-axial  muscle-sheet,  while  the  lateral  portion  of 
it  comes  from  the  post-axial  sheet.  In  correspondence  with  this  derivation  of  the  muscle,  its 
lateral  portion  is  occasionally  separate  from  the  rest  and  may  terminate  below  on  the  fascia  of 
the  forearm  or  on  the  radius.  A  longitudinal  separation  of  the  pre-axial  portion  of  the  muscle 
may  also  occur,  and  it  seems  probable  that  the  most  frequently  occurring  third  head  of  the 
biceps  (see  above)  is  a  derivative  of  this  portion  of  the  brachialis. 

The  epitrochleo-anconeus  is  a  small,  usually  quadrangular  muscle  which  is  present  in  about 
25  per  cent,  of  cases.     It  arises  from  the  posterior  surface  of  the  inner  condyle  of  the  humerus 


THE   BRACHIAL   MUSCLES. 


587 


and  passes  downward  and  laterally  to  be  inserted  into  the  external  surface  of  the  olecranon 
process  of  the  ulna.     Notwithstanding  its  position  upon  the  posterior  surface  of  the  arm,  it  is  a 

Fig.  570. 


Clavicle 
Subc 


Biceps] 


Tendon  of  ii 
sertion  of  pec-      y   ~\    ^$$$t  ^ 
toralis  major 


IVcturalis  minor 


Fig.  571. 


idon  of  latissimus 


Brachialis  anticus 


Brachialis  ant 


Tendon  of  .... 
of  biceps 

Brachio-radialis 


M I  iner  head  of  triceps 


Int.  intermuscul 

septum 
Brachialis  antici 


Head  of_J 
radius 
Bicipital 
tuberosity  of  radius 
Insertion  of  biceps 


Muscles  of  anterior  surface  of  ai 


derivative  of  the  pre-axial  muscle-sheet  and  is  supplied  by  the  ulnar  nerve,  whose  main  stern, 
as  it  passes  down  between  the  olecranon  and  the  inner  condyle,  is  covered  by  the  muscle. 
When  absent,  the  muscle  is  represented  by  a  strong  fibrous  band. 


588 


HUMAN   ANATOMY. 


{6)    THE   POST-AXIAL   MUSCLES. 

i.    Triceps  (Figs.  570,  572). 

Attachments.     The  triceps  (m.  triceps  brachii)  is  a  strong  muscle  which  occu- 
pies the  entire  dorsal  surface  of  the  arm.      It  arises  by  three  heads.      The  scapular  or 

Fig.  572. 

Suprasplnatus 

/  Spine  of  scapula 


Acromion  process 


Head  of  humerus  covered  by 
capsular  ligament 


Tendon  of  insertion  of  teres 


~\      Axillary  border  of 
scapula 


Teres  minor  (cut) 


Inferior  angle  of 
apula 


long  head  takes  its  origin  by  a  tendon  from  the  infra- 
glenoid  tuberosity  of  the  scapula  ;  the  inner  or  medial 
head,  from  the  posterior  (dorsal)  surface  of  the  humerus 
and  from  both  intermuscular  septa  below  and  medial 
to  the  groove  for  the  musculo-spiral  nerve  ;  and  the 
outer  or  lateral  head,  from  the  external  intermuscular 
septum  and  the  posterior  surface  of  the  humerus  above 
and  lateral  to  the  groove  for  the  musculo-spiral  nerve. 
The  three  heads  unite  to  form  a  strong,  broad  tendon 
which  is  inserted  into  the  olecranon  process  of  the 
ulna.  The  common  tendon  of  insertion  begins  as  a 
broad  aponeurosis  upon  the  anterior  surface  of  the 
long  head,  the  fibres  of  which  are  attached  to  the 
upper  border  and  the  upper  part  of  the  posterior  sur- 
face of  the  aponeurosis.  The  fibres  of  the  lateral  head 
are  attached  to  the  lateral  border  of  the  aponeurosis, 
while  those  of  the  medial  head,  which  is  much  stronger 
than  the  lateral  one,  pass  to  its  anterior  surface. 

Nerve-Supply. — By  the   musculo-spiral   nerve     mmor  cut  away- 
from  the  sixth,   seventh,   and  eighth  cervical  nerves. 

Action.— To  extend  the  forearm  on  the  upper  arm  and  to  draw  the  entire  arm 
backward. 

Variations.— The  triceps  occasionally  possesses  an  additional  head  arising  either  from  the 
coracoid  process  of  the  scapula  or  from  the  capsule  of  the  shoulder-joint. 


Triceps  and  posterior  scapular  irius- 
;  portions  of  infraspinatus  and  teres 


PRACTICAL    CONSIDERATIONS  :    MUSCLES    AND"  FASCIA.      589 

2.    Anconeus  (Fig.  581). 

Attachments. — The  anconeus  is  a  short  muscle  which  arises  from  the  posterior 
surface  of  the  external  condyle  of  the  humerus.  Its  fibres  diverge  to  form  a  triangu- 
lar sheet  which  is  inserted  into  the  upper  part  of  the  posterior  surface  of  the  ulna  and 
into  the  outer  surface  of  the  olecranon  process. 

Nerve-Supply. — By  the  musculo-spiral  nerve  from  the  seventh  and  eighth 
cervical  nerves. 

Action. — To  assist  the  triceps  in  extending  the  arm. 


PRACTICAL    CONSIDERATIONS  :    MUSCLES    AND    FASCIA    OF    THE 

ARM. 

The  deep  fascia  of  the  arm,  continuous  above  with  that  over  the  deltoid  and  with 
the  clavi-pectoral  fascia,  closely  embraces  all  the  muscular  structures  and  resists  the 
outward  passage  of  subfascial  collections  of  blood  or  pus,  which  therefore,  under  the 
influence  of  gravity,  tend  for  a  time  to  follow  the  intermuscular  spaces  downward. 
(Edema  and  swelling  above  the  elbow  are  thus  not  uncommon  as  a  result  of  disease 
or  injury  at  a  higher  level.  Blood  or  pus  may  reach  the  surface  by  following  the 
structures  that  pierce  the  fascia, — viz.,  the  basilic  vein  and  the  internal  and  external 
cutaneous  nerves.  The  ecchymosis  after  fracture  sometimes  takes  this  course.  The 
intermuscular  septa  (page  585)  divide  the  space  enclosed  by  the  brachial  aponeurosis 
into  an  anterior  and  a  posterior  compartment  extending  from  the  level  of  the  deltoid 
and  coraco-brachialis  insertions  to  that  of  the  two  condyles.  They,  too,  have  some 
effect  in  limiting  effusions,  but  the  latter,  especially  if  due  to  infection,  can  readily 
pass  from  one  space  to  the  other  by  following  the  musculo-spiral  nerve  or  the  superior 
profunda  artery  through  the  outer  septum,  or  the  ulnar  nerve,  inferior  profunda  artery, 
or  anastomotica  magna  through  the  inner  septum. 

In  selecting  a  method  of  amputation  through  the  arm  it  should  be  remembered 
that  above  the  middle  most  of  the  muscles  that  it  would  be  necessary  to  divide  are 
free  to  retract, — i.e. ,  the  deltoid,  the  long  head  of  the  triceps,  the  coraco-brachialis, 
and  the  biceps.  Below  the  middle  the  biceps  is  the  only  muscle  unattached.  In 
the  former  situation,  therefore,  the  circular  method  is  apt  to  lead  to  a  "conical 
stump' '  from  the  too  free  retraction  of  the  flaps  and  from  the  activity  of  the  upper 
humeral  epiphysis  (page  272).  In  amputation  just  above  the  elbow  the  circular 
method  is  applicable,  but  the  incision  should  be  a  little  lower  at  the  antero-internal 
aspect  of  the  limb  to  allow  for  the  greater  retraction  in  the  bicipital  region. 

Inward  dislocation  of  the  tendon  of  the  long  head  of  the  biceps  muscle  has 
probably  occurred  from  direct  violence  as  an  uncomplicated  lesion  in  a  few  cases. 
The  symptoms  are  said  to  be  (White)  :  (a)  the  recognition  of  the  bicipital  groove 
empty  ;  (6)  inward  rotation  due  to  the  pressure  of  the  tendon  on  the  lesser  tuberosity 
and  on  the  tendon  of  the  subscapularis  ;  (c)  adduction  of  the  humeral  head,  leaving 
a  slight  depression  beneath  the  tip  of  the  acromion  ;  (a?)  obvious  tension  along  the 
inner  edge  of  the  biceps  muscle  when  the  forearm  is  extended  ;  (e)  diminution  in  the 
vertical  circumference  of  the  shoulder  ;  and  (/)  shortening  of  the  distance  between 
the  acromion  and  external  condyle  ;  both  of  the  last  two  symptoms  are  due  to  the 
elevation  of  the  humeral  head  under  the  influence  of  the  deltoid,  the  supraspinatus, 
and  the  clavicular  fibres  of  the  pectoralis  major,  that  of  the  biceps  tendon  being  with- 
drawn. These  and  other  symptoms*  of  this  lesion  (although  it  is  extremely  rare) 
should  be  studied  in  connection  with  the  anatomy  of  the  muscles  involved,  as  an  aid 
in  elucidating  their  action.1 

Rupture  of  the  biceps  tendon  has  always  been  caused  by  violent  muscular  action, 
and  is  usually  accompanied  either  by  the  sudden  appearance  of  a  more  or  less  firm 
tumor  on  the  front  of  the  arm  or  by  complete  relaxation  and  flabbiness  of  the  whole 
muscle.  The  symptoms  mentioned  as  characteristic  of  dislocation  of  the  tendon 
have  not  been  noted  in  any  recorded  case  of  rupture,  with  the  exception  of  those  due 
to  the  elevation  of  the  head  of  the  humerus. 

1  J.  William  White  :  American  Journal  of  the  Medical  Sciences,  January,  18S4. 


59° 


HUMAN    ANATOMY. 


Fractures  of  the  humerus  are  much  influenced  by  muscular  action,  although  the 
controlling  force  in  the  production  of  the  deformity  is  often  that  which  causes  the 
fracture. 

In  fracture  of  the  tuberosities  the  theoretical  displacement  is  upward  and  back- 
ward for  the  greater  tuberosity  under  the  action  of  the  supra-  and  infraspinatus  and 
teres  minor,  and  forward  and  inward  for  the  lesser  tuberosity,  which  is  supposed 
to  be  drawn  in  that  direction  by  the  subscapularis.  The  injury  is  extremely  rare  ; 
the  clinical  signs  are  obscure.  Increased  breadth  of  the  shoulder,  localized  tender- 
ness and  disability,  occurring  after  the  application  of  direct  force  or  after  violent 
action  of  the  shoulder  muscles,  would  be  suggestive  ;  recognition  of  a  preternaturally 
mobile  or  displaced  fragment  would  be  conclusive  ;  but  the  X-rays  will  usually  be 
essential. 

In  fracture  of  the  surgical  neck  of  the  humerus — i.e. ,  between  the  tuberosities 
and  the  insertions  of  the  axillary  muscles — and  in  separation  of  the  upper  epiphysis 
the  fragments  are  similarly  influenced  by  muscular  action.  The  upper  fragment  is 
held  in  place,  is  a  little  elevated,  and  is  obliquely  tilted  by  the  supra-  and  infraspinatus, 

subscapularis,  and  teres  minor. 
573- 


» 


-Pecto 
majo 


Short   he 
of  biceps 


Latissimus  dorsi 
and  teres  major 


The   upper   end  of   the  lower 

fragment  is  drawn  towards  the 
chest-wall  by  the  pectoralis 
major,  latissimus  dorsi,  and 
teres  major.  Their  action  may 
be  aided  by  that  of  the  deltoid, 
which  may  fix  the  middle  of 
the  bone  so  that  it  acts  as  a 
fulcrum,  or  may  actually  abduct 
the  elbow.  The  biceps,  triceps, 
and  coraco-brachialis  and  del- 
toid draw  the  lower  fragment 
upward,  causing  shortening 
(Fig.  573)- 

Epiphyseal  disjunction  may 
be  suspected  if  (<z)  the  patient 
is  a  child  or  an  adolescent  ; 
(b)  the  anterior  projection  of 
the  upper  end  of  the  lower  frag- 
ment is  at  an  unusually  high 
level, — i.e. ,  about  that  of  the 
coracoid  ;  (<:)  the  crepitus  is 
muffled  ;  (d )  the  shortening 
is  slight  (page  272).  The  ap- 
plication of  the  tests  mentioned 
above  (page  583)  will  distin- 
guish this  lesion  from  luxation  of  the  shoulder,  which,  moreover,  is  very  rare  before 
adult  life  (page  306). 

In  fracture  of  the  shaft  of  the  humerus  between  the  insertions  of  the  axillary 
muscles  and  that  of  the  deltoid  the  upper  fragment  is  drawn  inward  by  the  former 
muscles  ;  the  lower  fragment  is  drawn  upward  by  the  biceps,  triceps,  and  coraco- 
brachialis,  and  upward  and  outward  by  the  deltoid  (Fig.  573). 

In  fracture  just  below  the  deltoid  insertion  that  muscle  acts  to  such  advantage  in 
abducting  the  upper  fragment  as  to  counteract  the  pull  of  the  axillary  muscles  in  the 
contrary  direction.  The  relation  of  the  fragments  will  therefore  chiefly  depend  upon 
the  direction  of  the  line  of  fracture  ;  the  shortening,  under  the  influence  of  the  biceps, 
triceps,  and  coraco-brachialis,  will  depend  on  its  degree  of  obliquity.  In  this  fracture 
it  is  sometimes  necessary  to  dress  the  arm  in  abduction  to  overcome  the  deltoid  con- 
traction. 

In  fracture  just  above  the  condyles  (page  273)  the  line  of  fracture  is  usually 
oblique  from  above  downward  and  forward  (Fig.  288).  The  short  lower  fragment 
will  be  drawn  upward  by  the  biceps  and  triceps  and  backward  by  the  latter  muscle. 


Dissection  of  fracture  of  surgical  neck  of  humerus. 


THE   ANTIBRACHIAL    MUSCLES.  591 

The  lower  end  of  the  upper  fragment  will  then  arrest  flexion  of  the  forearm  by  contact, 
or  may  puncture  the  brachialis  anticus,  the  bicipital  fascia,  and  even  the  skin. 

The  diagnosis  of  this  fracture  from  luxation  of  the  elbow  (Fig.  575)  can  be 
made  by  (a)  the  recognition  of  the  relations  of  the  three  bony  points, — the  tips  of  the 
two  condyles  and  of  the  olecranon  (page  306)  ;  (b)  the  presence  of  crepitus  ;  (c)  the 
disappearance  of  the  deformity  on  extension  and  counterextension,  and,  usually,  its 
reappearance  when  extension  is  discontinued  ;  and  (d)  the  greater  freedom  of  exten- 
sion of  the  forearm  on  the  arm  in  fracture  ;  flexion  may  be  limited,  as  above  men- 
tioned, by  the  contact  of  the  upper  fragment  with  the  forearm  at  the  bend  of  the  elbow 
and  other  points  ;   (e)  the  arm  is  shortened  in  fracture  ;  the  forearm  in  dislocation. 

In  separations  of  the  lower  humeral  epiphysis  (page  273)  (a)  the  patient  is  a 
child  or  an  adolescent ;  (£)  there  is  muffled  crepitus  ;  (t)  the  lower  end  of  the  upper 

Fig.  574.  Fig.  575. 


.Brachialis  anticus 
-Biceps 


External  condyle 


Olecranon  y%-      ^____  ■;' /' V..  /     ■'--       '  -•  - 

Head  of— CvrT""  Olecranon      ^  J]  ', 

radius  *W&.-^«;.'.-_ .,  ^WeS^S  J#' W^SSftsssd 

"—--  ~— -  -.  """         j  '  *|*L- 

Displaced  head  of  radii 
Posterior  luxation  of  elbow  of  right  side. 

fragment  has  greater  breadth  and  is  more  rounded  than  in  fracture  ;  (d)  the  line  of 
separation  is  nearer  the  end  of  the  bone,  and  the  anterior  projection  of  the  diaph- 
ysis  is  on  a  level  with  the  fold  of  the  elbow  ;  in  fracture  it  is  usually  above  it 
(Poland). 

Condylar  fractures  have  been  described  (page  273),  but  it  may  be  mentioned 
here  that  the  elevation  of  the  internal  condyle,  if  not  corrected,  causes  the  line  of  the 
joint  to  incline  inward  instead  of  outward.  If  union  takes  place  in  that  malposition, 
the  so-called  "gun-stock  deformity,"  or  "cubitus  varus"  (in  which  the  "carrying 
angle"  of  the  forearm  with  the  arm  is  obliterated  or  changed  to  a  similar  angle 
opening  inward)  results. 

The  bursae  about  the  elbow  have  been  described  (page  307). 

THE   ANTIBRACHIAL    MUSCLES. 

The  muscles  which  belong  to  this  group  act  primarily  upon  the  bones  of  the 
forearm  or  of  the  carpus  and  constitute  the  muscular  substance  of  the  forearm.  Some 
of  them,  however,  have  undergone  a  secondary  extension  into  the  hand  and  act  as 


592  HUMAN    ANATOMY. 

flexors  or  extensors  of  the  digits,  this  extension  being  due  in  some  cases  to  the 
differentiation  of  the  fascia  of  the  hand  into  tendons  continuous  with  those  of  the  an- 
tibrachial  muscles,  in  other  cases  to  end-union  of  antibrachial  and  hand  muscles.  It 
will  be  convenient,  however,  to  regard  the  long  flexors  and  extensors  of  the  digits, 
formed  in  this  way,  as  antibrachial  muscles. 

Comparatively  studied,  an  arrangement  of  the  antibrachial  muscles  in  distinct 
layers  is  clearly  perceivable,  three  layers  being  found  in  the  pre-axial  and  two  in  the 
post-axial  muscles.  In  both  cases  the  superficial  layer  takes  its  origin  from  the 
humerus,  while  the  remaining  layers  are  attached  above  to  the  bones  of  the  forearm. 
Secondary  adaptations  have  in  some  cases  interfered  with  the  distinctness  of  the 
layers,  but  the  primary  conditions  will  be  taken  as  the  basis  for  the  classification  of 
the  muscles. 

The  antibrachial  fascia  completely  invests  the  muscles  of  the  forearm  and  is 
the  downward  continuation  of  the  brachial  fascia.  It  is  especially  strong  upon  the 
dorsal  surface  of  the  forearm,  where  it  is  attached  to  the  olecranon  process  and  the 
entire  length  of  the  posterior  border  of  the  ulna,  and  anteriorly  it  is  strengthened  in 
its  upper  part  by  the  fibres  of  the  semilunar  fascia  of  the  biceps.  At  the  wrist  it  is 
attached  to  the  bones  of  the  forearm  and  carpus,  and  becomes  thickened  by  trans- 
verse fibres  to  form  the  dorsal  and  volar  carpal  ligaments. 

The  anterior  annular  ligament  (ligamentum  carpi  volare)  lies  on  the  anterior  sur- 
face of  the -wrist,  covering  the  flexor  muscles  in  that  region  (Fig.  577).  Laterally 
and  medially  it  is  connected  with  the  dorsal  ligament.  This,  the  posterior  annular 
ligament  (ligamentum  carpi  dorsale),  is  a  stronger  transverse  band  on  the  posterior 
surface  of  the  wrist,  and  is  attached  laterally  to  the  outer  surface  and  to  the  styloid 
process  of  the  radius,  and  passes  inward  and  slightly  downward  to  the  styloid  process 
of  the  ulna  and  to  the  pisiform  and  cuneiform  bones,  making  attachments  to  the  ridges 
on  the  posterior  surface  of  the  radius  and  ulna  and  thus  converting  the  six  intervening 
grooves  into  canals  which  lodge  the  tendons  of  the  long  extensor  muscles  (Fig.  579). 
Beginning  at  the  radial  side,  the  first  canal  transmits  the  tendons  of  the  extensor  ossis 
metacarpi  pollicis  and  the  extensor  brevis  pollicis  ;  the  second,  the  tendons  of  the  two 
extensores  carpi  radiales  ;  the  third,  that  of  the  extensor  longus  pollicis  ;  the  fourth, 
those  of  the  extensor  communis  digitorum  and  the  extensor  indicis  ;  the  fifth,  that  of 
the  extensor  minimi  digiti  ;  and  the  sixth,  that  of  the  extensor  carpi  ulnaris.  Each 
of  the  canals  is  lined  by  an  independent  synovial  membrane. 

(a)    THE   PRE-AXIAL   MUSCLES. 
(aa)    The  Superficial  Layer. 

1.  Pronator  radii  teres.  3.    Palmaris  longus. 

2.  Flexor  carpi  radialis.  4.    Flexor  carpi  ulnaris. 

5.    Flexor  sublimis  digitorum. 

1.    Pronator  Radii  Teres  (Fig.  576). 

Attachments. — This  muscle  (m.  pronator  teres),  thick  and  band-like,  arises  by 
two  heads  (a)  from  the  inner  condyle  of  the  humerus,  the  adjacent  intermuscular 
septa,  and  the  deep  fascia,  and  (o)  from  the  medial  border  of  the  coronoid  process  of 
the  ulna.  It  passes  downward  and  laterally  and  is  inserted  into  about  the  middle  of 
the  outer  surface  of  the  radius.  The  median  nerve  passes  downward  between  the 
two  heads. 

Nerve-Supply. — By  the  median  nerve  from  the  sixth  cervical  nerve. 

Action. — To  pronate  and  flex  the  forearm. 

Variations. — The  pronator  teres  is  formed  by  a  combination  of  portions  from  the  super- 
ficial and  deep  layers  of  the  forearm  musculature,  the  condylar  head  representing  the  superficial 
portion  and  the  coronoid  head  the  deep  one.  In  the  lower  mammals  the  pronator  quadratus 
frequently  extends  well  up  towards  the  elbow-joint,  and  the  coronoid  head  of  the  pronator 
teres  represents  the  uppermost  portion  of  this  muscle,  its  lower  portion  persisting  as  the  pro- 
nator quadratus.  Not  infrequently  the  coronoid  portion  of  the  muscle  is  completely  separate 
from  the  condylar  head,  or  it  may  be  rudimentary  or  represented  only  by  a  connective-tissue 


THE   ANTIBRACHIAL    MUSCLES. 


593 


band.  The  entire  muscle  is  some- 
times incompletely  separated  from 
the  neighboring  muscles  of  the  su- 
perficial layer,  receiving  accessory 
heads  from  the  palmaris  longus  or 
the  flexor  sublimis  digitorum. 

2.   Flexor  Carpi  Radialis 

(Fig.  576). 

Attachments. — The  flexor 
carpi  radialis  arises  from  the  inner 
condyle  of  the  humerus,  by  a 
tendon  common  to  it  and  the 
neighboring  muscles  of  the  super- 
ficial layer,  from  the  adjoining 
intermuscular  septa  and  the  deep 
fascia.  It  passes  downward  and 
slightly  laterally  and  is  inserted 
into  the  bases  of  the  second  and 
third  metacarpal  bones. 

Nerve-Supply.  —  By  the 
median  nerve  from  the  sixth  cer- 
vical nerve. 

Action. — To  flex  the  hand 
and  to  assist  in  pronating  the 
forearm. 

Relations. — In  its  course 
down  the  forearm  the  flexor  carpi 
radialis  passes  obliquely  across 
the  flexor  sublimis  digitorum  and 
the  lower  part  of  the  flexor  longus 
pollicis.  At  the  wrist  it  passes 
through  a  special  sheath  within 
the  superficial  part  of  the  anterior 
annular  ligament,  and  just  before 
its  insertion  it  is  crossed  by  the 
tendon  of  the  flexor  longus  pol- 
licis. A  bursa  (bursa  m.  flexoris 
carpi  radialis)  is  interposed  be- 
tween the  tendon  and  the  base 
of  the  second  metacarpal  bone. 
Laterally  the  muscle  is  in  contact 
above  with  the  pronator  radii 
teres  and  below  with  the  brachio- 
radialis,  from  which  it  is  sepa- 
rated near  the  wrist  by  the  radial 
artery. 


I'.nu  liialis  anticus- 


Brachio-radiali: 


Extensor  car] 
radialis  longic 


'almaris 
longus 


digitorum 


Styloid  process — \ 

Exten: 

metacarpi 
pollicis 


M — Flexor  carpi  u!n 


Palmaris  brevi: 


^Palmar  fascia 


3.   Palmaris  Longus 
(Fig.  576). 

Attachments. — The  pal- 
maris longus  arises  with  the 
neighboring  superficial  muscles 
by  the  common  tendon  from  the 
inner  condyle  of  the  humerus, 
from  the  adjoining  intermuscular 
septa,  and  from  the  deep  fascia. 
It  forms  a  short  spindle-shaped 
belly  which  is  continued  into  a 


Superficial  dissection 
portion  of  antibrachial  fas 
has  been  left  in  place. 

3s 


■m   and   palm,  anterl 
"ing  origin  of  superfic 


594 


HUMAN   ANATOMY. 


Fig.  577. 


Brachialis  anticu 


Tendon  of  biceps. 


Extensor  carpi 
radialis  longior 


long,  slender  tendon  that 
passes  in  front  of  the  an- 
terior annular  ligament 
of  the  wrist,  and  is  in- 
serted into  the  palmar 
fascia. 

Nerve-Supply. — 
By  the  median  nerve 
from  the  sixth  cervical 
nerve. 

Action. — To  tense 
the  palmar  fascia  and  flex 
the  hand. 

Variations. — The  pal- 
maris  longus  is  a  very  vari- 
able muscle.  It  is  not  in- 
frequently absent,  and  may 
present  various  modifica- 
tions in  its  structure,  being 
sometimes  entirely  tendi- 
nous, or  entirely  fleshy,  or 
tendinous  above  and  fleshy 
below.  It  is  occasionally 
double. 

4.  Flexor  Carpi  Ul- 
naris  (Fig.  576). 

Attachments.  — 

The  flexor  carpi  ulnaris 
arises  from  the  medial 
condyle  of  the  humerus 
in  common  with  the 
neighboring  superficial 
muscles,  from  the  inter- 
muscular septa  and  deep 
fascia,  and  also  from  the 
posterior  surface  of  the 
olecranon  process,  and 
from  the  upper  part  of 
the  posterior  border  of 
the  ulna  by  means  of  an 
aponeurosis  common  to 
it  and  the  flexor  pro- 
fundus digitorum  and 
the  extensor  carpi  ul- 
naris. It  descends  along 
the  ulnar  border  of  the 
forearm  and  is  inserted 
into  the  pisiform  bone, 
its  tendon  being  contin- 
ued on  to  be  attached  to 
the  hook  of  the  unciform 
and,  often,  to  the  base  of 
the  fifth  metacarpal  bone. 

Nerve-Supply. — 
By  the  ulnar  nerve  from 
the  eighth  cervical  and 
first  thoracic  nerves. 

Action. —  To  flex 
and  adduct  the  hand. 


THE   ANTIBRACHIAL    MUSCLES.  595 

Relations. — By  its  deep  surface  this  muscle  is  in  relation  with  the  sublimis  and 
profundus  digitorum  and  with  the  ulnar  vessels  and  nerve.  The  ulnar  nerve  and 
posterior  recurrent  ulnar  artery  pass  beneath  a  tendinous  band  which  stretches  across 
between  the  two  heads  of  the  muscle,  and  towards  the  wrist  the  ulnar  artery  comes 
to  lie  along  the  lateral  border  of  the  tendon.  A  mucous  bursa  (bursa  m.  flexoris 
carpi  ulnaris)  is  frequently  to  be  found  between  the  tendon  and  the  upper  part  of  the 
pisiform  bone. 

Variations.— The  flexor  carpi  ulnaris  frequently  passes  distally  to  be  inserted  into  the  base 
of  the  fifth  metacarpal.  The  conversion  of  the  ulnar  head  into  connective  tissue  has  been 
observed. 

5.   Flexor  Sublimis  Digitorum  (Fig.  577). 

Attachments. — The  superficial  flexor  (m.  flexor  digitorum  sublimis)  arises  from 
the  inner  condyle  of  the  humerus  in  common  with  the  neighboring  superficial  mus- 
cles, from  an  oblique  line  on  the  anterior  surface  of  the  radius,  and  from  the  tendi- 
nous arch  extending  between  these  two  bony  points  and  beneath  which  the  median 
nerve  and  ulnar  artery  pass.  The  fibres  arising  from  these  origins  form  four  bellies, 
prolonged  below  into  as  many  tendons,  which  at  the  wrist  pass  beneath  the  ante- 
rior annular  ligament  and  then  diverge  towards  the  bases  of  the  second,  third,  fourth, 
and  fifth  fingers  and  enter  the  corresponding  digital  sheaths.  Here  each  tendon 
divides  over  the  surface  of  the  first  phalanx  into  two  slips,  which  pass  one  on  either 
side  of  the  subjacent  tendon  of  the  flexor  profundus  digitorum  and  partially  unite 
beneath  it  to  be  inserted  into  the  base  of  the  second  phalanx.  Slight  tendinous 
bands,  vinculo,  tendinum,  pass  between  the  tendons  of  the  profundus  and  the  terminal 
portions  of  those  of  the  sublimis. 

Nerve-Supply. — By  the  median  nerve  from  the  seventh  and  eighth  cervical 
and  first  thoracic  nerves. 

Action. — Primarily  to  flex  the  second  phalanx  of  the  four  medial  digits,  but  a 
continuation  of  its  action  will  flex  the  first  phalanges  of  the  same  digits  and  eventually 
the  hand. 

Relations. — Superficially  the  flexor  sublimis  is  covered  by  the  remaining 
muscles  of  the  superficial  layer  ;  deeply  it  is  in  relation  with  the  flexor  profundus 
digitorum,  the  flexor  longus  pollicis,  the  ulnar  vessels,  and  the  median  nerve. 

Variations. — Occasionally  the  portion  of  the  muscle  which  gives  rise  to  the  tendon  of  the 
fifth  digit  appears  to  be  wanting,  the  tendon  arising  from  the  palmar  fascia,  the  anterior  annular 
ligament,  or  the  flexor  profundus.  An  explanation  of  this  anomaly  is  found  in  the  developmental 
history  of  the  muscle.  In  the  lower  vertebrates  the  superficial  flexor  inserts  into  the  palmar 
fascia,  which  gives  origin  to  a  set  of  superficial  digital  muscles  whose  relations  are  similar  to 
those  of  the  digital  portions  of  the  sublimis  tendons.  In  the  mammalia  these  digital  muscles  de- 
generate into  tendinous  bands,  with  which  the  tendon  of  the  antibrachial  portion  of  the  muscle 
becomes  continuous.  The  origin  of  the  tendon  for  the  fifth  digit  from  the  palmar  aponeurosis 
or  transverse  carpal  ligament  is,  therefore,  a  persistence  of  a  phyletic  stage,  as  is  also  its  origin 
from  the  flexor  profundus,  since  in  the  lower  mammals  the  antibrachial  portions  of  the  two 
muscles  are  united  to  form  a  single  mass  (page  597). 

(6b)    The  Middle  Laver. 
I.    Flexor  profundus  digitorum.  2.    Flexor  longus  pollicis. 

1.    Flexor  Profundus  Digitorum  (Fig.  578). 

Attachments. — The  deep  flexor  (m.  flexor  digitorum  profundus)  arises  from  the 
anterior  and  outer  surfaces  of  the  ulna  and  from  the  inner  half  of  the  interosseous 
membrane.  Its  fibres  are  directed  downward,  and  at  about  the  middle  of  the  fore- 
arm are  continued  into  four  tendons,  which  pass  beneath  the  anterior  annular  liga- 
ment along  with  the  tendons  of  the  flexor  sublimis  to  enter  the  digital  sheaths  of  the 
second,  third,  fourth,  and  fifth  fingers.  Opposite  the  first  phalangeal  joint  each 
tendon  passes  between  the  two  slips  of  the  corresponding  tendon  of  the  flexor  sub- 
limis and  is  inserted  into  the  base  of  the  terminal  phalanx. 

Nerve-Supply. — The  lateral  half  of  the  muscle  is  supplied  by  branches  from 
the  anterior  interosseous  branch  of    the  median  nerve  and  the  medial  half  by  the 


596 


HUMAN   ANATOMY. 


Fig.  57S. 


Bnu/lnalis  anticus 


Insertion  of  pronator  radii  teres 


Flexor  longus  pollicis 


Flexor     A 
brev'is  pollicis.     - 
Adductor  pollicis, 
oblique  port' 


Tendon  of  flexor  carpi  radial 


Abductor  pollicis,  cut 
Opponens  pollicis 


Tendons 

of  fle 

subli 

itorum 


■ 


ulnar  ;  the  fibres  come  from 
the  seventh  and  eighth  cer- 
vical and  the  first  thoracic 
nerves. 

Action. — The  primary 
action  of  the  flexor  pro- 
fundus is  to  flex  the  ter- 
minal phalanges  of  the 
second,  third,  fourth,  and 
fifth  fingers,  but,  continu- 
ing its  action,  it  also  flexes 
the  remaining  phalanges  of 
those  digits  and  finally  the 
hand. 

Relations.  —  In  the 
arm  the  muscle  is  covered 
by  the  flexor  sublimis  digi- 
torum  and  the  flexor  carpi 
ulnaris,  and  has  resting 
upon  its  anterior  surface 
the  ulnar  vessels  and  the 
median  and  ulnar  nerves. 
Posteriorly  it  is  in  relation 
to  the  pronator  quadratus 
and  the  wrist-joint.  In  the 
hand  its  tendons  are  cov- 
ered by  those  of  the  flexor 
sublimis  and  by  the  lum- 
brical  muscles  ;  they  rest 
upon  the  adductor  pollicis 
and  interosseous  muscles 
and  cross  the  deep  palmar 
arch. 

Variations. — The  flexor 
profundus  frequently  receives 
additional  slips  from  the  flexor 
sublimis  and  may  be  united  to 
the  flexor  longus  pollicis.  A 
slip  which  has  been  termed 
the  accessorius  ad  flexorem 
profundum  digiiorum  not  in- 
frequently occurs,  arising  from 
the  coronoid  process  of  the 
ulna  and  joining  with  one  of 
the  tendons  of  the  profundus. 
The  significance  of  the  varia- 
tions of  the  profundus  will  be 
considered  in  connection  with 
those  of  the  flexor  longus  pol- 
licis. 

2.  Flexor  Longus  Pol- 
licis (Fig.  578). 

Attachments. — The 

long  flexor  of  the  thumb 
(m.  flexor  pollicis  longus) 
lies  to  the  lateral  side  of 
the  flexor  profundus  digi- 
torum  and  arises  from  the 
anterior  surface  of  the  ra- 
dius and  the  adjacent  half 


THE    ANTEBRACHIAL    MUSCLES.  597 

of  the  interosseous  membrane.  It  usually  possesses  also  an  origin  by  means  of  a 
slender  slip  from  the  coronoid  process  of  the  ulna  or  the  medial  epicondyle  of  the 
humerus.  The  muscle-fibres  pass  into  a  strong  tendon  at  the  middle  of  the  forearm, 
and  this  passes  downward  beneath  the  lateral  part  of  the  annular  ligament  and 
extends  along  the  volar  surface  of  the  thumb  to  be  inserted  into  the  base  of  its  ter- 
minal phalanx. 

Nerve-Supply. — By  the  anterior  interosseous  nerve  from  the  eighth  cervical 
and  first  thoracic  nerves. 

Action. — To  flex  the  terminal  phalanx  of  the  thumb  ;  continuing  its  action,  it 
will  also  flex  the  proximal  phalanx  and  assist  in  the  flexion  of  the  hand. 

Relations. — In  the  forearm  it  is  covered  by  the  flexor  sublimis  digitorum,  the 
flexor  carpi  radialis,  and  the  brachio-radialis,  and  has  resting  upon  it  the  radial  ves- 
sels. Deeply  it  is  in  relation  with  the  pronator  quadratus  and  the  wrist-joint.  In 
the  hand  its  tendon  is  covered  by  the  opponens  pollicis  and  the  flexor  brevis  pollicis, 
and  it  rests  upon  the  adductor  pollicis. 

Variations. — The  head  from  the  coronoid  process  or  medial  epicondyle  of  the  humerus  is 
sometimes  absent  and  the  muscle  is  frequently  connected  with  the  flexor  profundus  digitorum  or 
even  fused  with  it. 

Occasionally  there  arises  from  the  lower  part  of  the  anterior  and  external  surfaces  of  the 
radius  a  muscle  which  has  been  termed  the  flexor carpi radialis  brevis.  Its  insertion  varies  some- 
what, being  sometimes  on  one  of  the  carpal  bones,  at  other  times  on  either  the  second,  third,  or 
fourth  metacarpals,  and  at  others,  again,  into  the  transverse  carpal  ligament.  Although  asso- 
ciated by  name  with  the  flexor  carpi  radialis,  it  is  more  probably  a  derivative  of  the  deeper  layer 
of  the  flexor  musculature  and  is  supplied  by  the  volar  interosseous  branch  of  the  median  nerve. 

The  majority  of  the  variations  of  the  flexor  longus  pollicis  and  flexor  profundus  digitorum 
find  an  explanation  in  the  historical  development  of  the  muscles.  In  the  lowest  group  of  the 
mammalia,  the  monotremata,  the  two  muscles  are  fused  with  each  other  and  also  with  the 
flexor  sublimis  to  form  a  common  long  flexor,  from  the  tendon  of  which  the  tendons  of  the  flexor 
sublimis  arise.  In  slightly  higher  forms  this  common  flexor  can  be  seen  to  be  composed  of  five 
portions,  which,  from  their  points  of  origin  and  relations,  may  be  termed  the  condylo-ulnaris, 
condylo-radialis,  centralis,  ulnaris,  and  radialis,  and  as  the  scale  is  ascended  one  finds  at  first  a 
part  of  the  condylo-ulnaris  and  later  the  whole  of  that  portion  separating  from  the  common  mass 
and  joining  the  tendons  of  the  sublimis.  In  still  higher  forms  the  centralis  and  condylo-radialis 
portions  follow  the  example  of  the  condylo-ulnaris,  the  flexor  sublimis  digitorum  in  man  being 
composed  of  these  portions  of  the  common  mass'. 

The  ulnaris  and  radialis  portions  remain,  as  a  rule,  united  and,  after  the  separation  of  the 
superficial  portions  is  completed,  constitute  the  flexor  profundus.  In  man  and  a  few  other  forms 
the  radialis  separates  from  the  ulnaris  to  form  the  flexor  longus  pollicis. 

The  connections  which  occur  between  the  sublimis,  profundus,  and  flexor  longus  pollicis 
are  consequently  to  be  regarded  as  relics  of  the  historical  development  of  the  muscles,  as  the 
incomplete  separation  of  a  common  flexor  mass. 

In  the  lower  terrestrial  vertebrata  the  superficial  and  deeper  layers,  corresponding  practi- 
cally to  the  sublimis  and  profundus  (plus  the  flexor  longus  pollicis),  are  distinct,  their  fusion  in 
the  monotremes  being  a  secondary  condition,  which  forms  the  starting-point  for  the  differentia- 
tion of  the  mammalian  arrangement  of  the  muscles.  In  these  lower  forms  both  layers  insert 
into  the  palmar  aponeurosis,  the  extension  of  the  deeper  layer  to  the  digits  being  due  to  the 
separation  of  the  layer  of  the  aponeurosis  to  which  the  deeper  muscle-layer  is  attached  and  its 
differentiation  into  tendons. 

It  may  be  added  that  in  the  lower  vertebrates  the  palmaris  longus  is  not  represented  as  a 
separate  muscle,  and  it  is  to  be  regarded  as  a  portion  of  the  superficial  sheet  which  has  retained 
its  original  relations  to  the  palmar  aponeurosis,  its  occasional  absence  being  ascribed  to  its 
sharing  the  history  of  the  flexor  sublimis  and  being  incorporated  in  that  muscle. 

(rr)  The  Deep  Layer. 
1.    Pronator  quadratus. 

1.    Pronator  Quadratus  (Fig.  588). 

Attachments. — The  pronator  quadratus  is  a  flat  quadrangular  sheet  extending 
across  between  the  lower  portions  of  the  radius  and  ulna.  It  arises  from  the  volar 
surface  of  the  ulna  and  passes  laterally  and  slightly  distally  to  be  inserted  into  the 
lateral  and  anterior  surfaces  of  the  lower  end  of  the  radius. 

Nerve-Supply. — By  the  anterior  interosseous  branch  of  the  median  nerve  from 
the  seventh  and  eighth  cervical  and  the  first  thoracic  nerves. 

Action. — To  pronate  the  forearm. 


598  HUMAN    ANATOMY. 

Variations. — The  pronator  quadratus  usually  occupies  about  the  lower  fourth  of  the  fore- 
arm, but  it  may  be  considerably  reduced  or,  on  the  contrary,  may  extend  as  high  as  the  middle 
of  the  forearm  or  even  higher.  It  represents  the  lower  portion  of  a  muscle-sheet  which  extends 
in  some  of  the  lower  mammals  almost  the  entire  length  of  the  forearm,  the  upper  portion  of 
this  sheet  being  represented,  as  already  pointed  out,  by  the  coronoid  head  of  the  pronator  teres. 

(6)    THE  POST- AXIAL  MUSCLES. 

The  post-axial  muscles  of  the  forearm  may  be  regarded  as  consisting  of  two 
layers,  the  more  superficial  of  which  arises  from  the  external  condyle  of  the  humerus, 
while  the  deeper  one  is  attached  to  the  bones  of  the  forearm.  As  was  the  case  with 
the  pre-axial  muscles,  constituents  of  both  layers  have  extended  into  the  hand  to  act 
as  extensors  of  the  digits. 

(aa)  The  Superficial  Layer. 

1.  Brachio-radialis.  4.    Extensor  communis  digitorum. 

2.  Extensor  carpi  radialis  longior.  5.    Extensor  minimi  digiti. 

3.  Extensor  carpi  radialis  brevior.  6.    Extensor  carpi  ulnaris. 

1.    Brachio-Radialis  (Fig.   576). 

Attachments. — The  brachio-radialis,  sometimes  termed  the  supinator  longus, 
arises  from  the  external  condylar  ridge  of  the  humerus  and  from  the  lateral  inter- 
muscular septum.  Its  fibres  form  a  strong  muscle  which,  at  about  the  middle  of  the 
forearm,  passes  into  a  tendon  which  is  inserted  into  the  base  of  the  styloid  process  of 
the  radius. 

Nerve-Supply. — By  the  musculo-spiral  nerve  from  the  fifth  and  sixth  cervical 
nerves. 

Action. — To  flex  the  forearm.  If  the  arm  be  in  a  position  of  complete  prona- 
tion, it  will  produce  a  slight  amount  of  supination. 

Relations. — In  its  upper  part  it  is  in  contact  medially  with  the  brachialis  ami- 
cus, a  portion  of  whose  lateral  border  it  covers,  and  with  the  radial  nerve.  Below  it 
rests  upon  the  upper  portion  of  the  extensor  carpi  radialis  longior,  the  supinator,  the 
pronator  teres,  the  flexor  sublimis  digitorum,  and  the  radial  artery  and  nerve.  It  is 
crossed  near  its  insertion  by  the  tendons  of  the  abductor  longus  pollicis  and  extensor 
brevis  pollicis. 

Variations. — The  brachio-radialis  is  sometimes  wanting.  It  may  be  inserted  a  consider- 
able distance  above  the  base  of  the  styloid  process  of  the  radius,  a  condition  characteristic  of 
the  lower  mammals,  or  it  may  pass  as  far  down  as  the  carpal  bones  or  even  to  the  base  of  the 
third  metacarpal. 

2.    Extensor  Carpi  Radialis  Longior  (Figs.  576,  579). 

Attachments. — The  longer  of  the  radial  carpal  extensors  (m.  extensor  carpi 
radialis  longus)  lies  immediately  posterior  to  the  brachio-radialis.  It  arises  from  the 
lower  third  of  the  external  supracondylar  ridge  of  the  humerus,  the  external  inter- 
muscular septum,  and  the  extensor  tendon  common  to  it  and  the  neighboring  super- 
ficial muscles.  About  the  middle  of  the  forearm  it  is  continued  into  a  tendon  which 
passes  beneath  the  posterior  annular  ligament  in  the  second  compartment,  along  with 
the  extensor  carpi  radialis  brevior,  and  is  inserted  into  the  base  of  the  second  meta- 
carpal. 

Nerve-Supply. — By  the  deep  division  of  the  musculo-spiral  nerve  from  the 
sixth  and  seventh  cervical  nerves. 

Action. — To  extend  and  slightly  abduct  the  hand. 

Variations.— The  extensor  carpi  radialis  longior  is  occasionally  fused  with  the  extensor 
carpi  radialis  brevior.  It  may  send  tendinous  slips"  to  the  first  and  third  metacarpals  and  to  the 
'.rapezium. 

3.    Extensor  Carpi  Radialis  Brevior  (Fig.   579). 
Attachments. — The  shorter  radial  carpal  extensor  (m.  extensor  carpi  radialis 
brevis)  is  fused  with  the  neighboring  superficial  extensors  where  it  arises  from  the 


THE  ANTIBRACHIAL   MUSCLES. 


599 


external  condyle  of  the  hu- 
merus, from  the  adjacent  in- 
termuscular septa,  and  from 
the  deep  fascia  of  the  fore- 
arm. Its  fibres  converge  at 
about  the  middle  of  the  fore- 
arm into  a  flat  tendon,  which 
passes  with  the  long  exten- 
sor carpi  radialis  beneath  the 
posterior  annular  ligament 
in  the  second  compartment 
and  is  inserted  into  the  base 
of  the  third  metacarpal,  a 
bursa  (bursa  m.  extensoris 
carpi  radialis)  being  inter- 
posed between  the  tendon 
and  the  bone. 

Nerve-Supply.  —  By 
the  posterior  interosseous 
branch  of  the  musculo-spiral 
nerve  from  the  sixth  and 
seventh  cervical  nerves. 

Action. — To  extend 
the  hand. 

Variations. — It  may  be  fused 
to  a  greater  or  less  extent  with 
the  extensor  carpi  radialis  lon- 
gior  and  may  be  inserted  into 
the  bases  of  both  the  second 
and  third  metacarpals. 

4.   Extensor  Communis 
Digitorum  (Fig.  579). 

Attachments.  —  The 

common  extensor  of  the 
fingers  (m.  extensor  digitorum 
communis)  arises  in  com- 
mon with  the  neighboring 
superficial  extensors  from 
the  external  condyle  of  the 
humerus,  from  the  septa  be- 
tween it  and  the  adjoining 
muscles,  and  from  the  deep 
fascia  of  the  forearm.  At 
about  the  middle  of  the 
forearm  its  fibres  go  over 
into  four  tendons,  which  pass 
through  the  fourth  compart- 
ment beneath  the  posterior 
annular  ligament  and  diverge 
to  be  inserted  into  the  bases  of 
the  middle  and  terminal  pha- 
langes of  the  second,  third, 
fourth,  and  fifth  fingers.  Just 
before  they  pass  over  the 
metacarpophalangeal  joints 
of  their  digits  the  four  ten- 
dons are  usually  united  by 


Fig.  579. 


Brachio-radiali: 


Anrnnpnt;      ;         4 


Flexor  carpi  ulnaris 


Extensor  carpi  ulnaris-Li 


Extensor  minimi  digit: 


Posterior  annular 
ligament 


Extensor  indicis  tendon 


\'.        ■vflir!   V  MM      Tendon,.: 


Tendon  of  extensor 
carpi  radialis  longior 
Tendon  of  extensor 
carpi  radialis  brevior 


6oo 


HUMAN   ANATOMY. 


Fig.  580. 


Olecranon  proces: 


'   itr'W        m 


$2jiff— Extensor  carpi 

radialis  longior 
External  condyle 


Flexor  carpi  ulnaris 


Extensor  ind 


i  v,y      J   ft  \A\  I  -f^ — Extensor  < 

7  \  / J  ;\  I  A   l-bv — Extensor  1 
(/^/  \UyiBl        alislongi. 


Tendons 

extensor 

communis 

digitoruru 


Opponen_        ^J!  ft    >     )'\U  ,  u\\  V 
'ossein — «—  irt^~~~~h"'i     :4   '    -  ,.t-'~h--:- H» 

sales  rf  I  ''  v^': 


\X        Extensor  brevi 
Av      pollicis  tendon 


three  obliquely  transverse  ten- 
dinous bands  (juncturae  ten- 
dinum),  the  one  between  the 
index  and  median  digits  being, 
however,  frequently  wanting. 
As  each  tendon  passes  upon 
the  dorsum  of  the  first  phalanx 
of  its  digit  it  spreads  out  into  a 
membranous  expansion,  which 
receives  the  insertions  of  the 
interosseous  and  lumbrical 
muscles  and  then  divides  into 
three  more  or  less  well-defined 
slips.  The  median  slip  passes- 
to  the  base  of  the  second  pha- 
lanx, while  the  lateral  ones, 
passing  over  the  first  interpha- 
langeal  joint,  unite  over  the 
dorsum  of  the  second  phalanx 
and  are  inserted  into  the  base 
of  the  first  phalanx. 

Nerve-Supply. — By  the 
posterior  interosseous  branch 
of  the  musculo-spiral  nerve 
from  the  sixth,  seventh,  and 
eighth  cervical  nerves. 

Action. — To  extend  the- 
phalanges  of  the  second,  third, 
fourth,  and  fifth  fingers  and,, 
continuing  its  action,  to  extend, 
the  hand. 

Variations.  —  The  principal 
variations  of  the  common  extensor 
consist  in  the  absence  of  one  or 
other  of  the  tendons,  usually  that 
to  the  fifth  digit  and  more  rarely 
that  to  the  second,  or  else  in  the- 
occurrence  of  additional  tendons, 
due  to  the  division  of  one  or  more 
of  those  typically  occurring,  cer- 
tain of  the  digits  then  receiving- 
two  or  even  three  tendons.  Oc- 
casionally an  additional  tendon  is 
present  which  passes  to  the  thumb 
to  unite  with  the  tendon  of  its  long 
extensor. 

5.    Extensor    Minimi   Dig- 
iti  (Fig.  579). 

Attachments. — The  ex- 
tensor of  the  little  finger  (m. 
extensor  digiti  quinti  proprius ) 
arises  in  common  with  the 
preceding  muscle  from  the  lat- 
eral epicondyle  of  the  humerus 
and  from  the  antibrachial  fas- 
cia. Its  tendon  passes  beneath 
the  posterior  annular  ligament 
in  the  fifth  compartment  and 
fuses  over  the  fifth  metacarpal 


THE   ANTEBRACHIAL    MUSCLES. 


60 1 


Eiacliialis  anticus 


with    the  tendon  of    the  extensor  communis  digitorum  which  passes    to   the  little 
finger. 

Nerve-Supply. — By  the  posterior  interosseous  branch  of  the  musculo-spiraL 
nerve  from  the  sixth,  seventh,  and 
eighth  nerves.  Fig.  581. 

Action. — To  extend  the  lit- 
tle finger. 

Variations. — This  muscle  is  some- 
times absent,  probably  remaining  in- 
corporated in  the  Extensor  communis. 
Its  tendon  occasionally  sends  a  slip  to 
the  fourth  finger. 

6.    Extensor  Carpi  Ulnaris 
(Figs.  577,  579). 

Attachments. — The  exten- 
sor carpi  ulnaris  arises  in  common 
with  the  adjacent  superficial  ex- 
tensors from  the  external  condyle 
of  the  humerus,  from  the  deep 
fascia,  and,  usually,  from  the  apo- 
neurosis attached  to  the  posterior 
border  of  the  ulna  common  to 
this  muscle,  the  flexor  profundus 
digitorum,  and  the  flexor  carpi  ul- 
naris. Its  tendon  passes  through 
the  sixth  compartment  beneath 
the  posterior  annular  ligament  and 
is  inserted  into  the  base  of  the 
fifth  metacarpal  bone. 

Nerve-Supply.  —  By  the 
posterior  interosseous  branch  of 
the  musculo-spiral  nerve  from  the 
sixth,  seventh,  and  eighth  cervical 
nerves. 

Action. — To  extend  and  ad- 
duct  the  hand. 

Variations — A  fibrous   band  is 
often  given  off  from  the  tendon  of  the 
muscle  to  be  inserted  somewhere  over 
the  fifth  metacarpal  into  the  sheath  of  the  tendon  of  the  extensor  of  the  little  finger  ;  it  has: 
been  termed  the  m.  ulnaris  quinti  digili. 


Dissection  of  arm,  showing  deep  muscle 


:inity  of  elbow'. 


(6b)  The  Deep  Layer. 

1.  Supinator.  3.    Extensor  brevis  pollicis. 

2.  Extensor  ossis  metacarpi  pollicis.  4.    Extensor  longus  pollicis. 

5.    Extensor  indicis. 

1.   Supinator  (Figs.   580,  581). 

Attachments. — The  supinator,  also  termed  the  supinator  radii  brevis,  is  a  flat 
triangular  muscle  which  arises  partly  from  the  outer  condyle  of  the  humerus  and  the 
orbicular  ligament  of  the  elbow-joint,  and  partly  from  the  upper  part  of  the  lateral 
border  of  the  ulna  and  the  smooth  surface  beneath  the  lesser  sigmoid  cavity  of  that 
bone.  Its  fibres  pass  obliquely  downward  and  outward,  diverging  as  they  go,  and 
are  inserted  into  the  posterior,  lateral,  and  anterior  surfaces  of  the  radius,  curving 
around  that  bone.  The  insertion  extends  downward  to  about  the  middle  of  the 
radius. 


6o2 


HUMAN   ANATOMY. 


Nerve-Supply. — By  the  posterior  interosseous  branch  of  the  musculo-spiral 
nerve  from  the  sixth  cervical  nerve. 

Action. — To  supinate  the  forearm. 

Variations. — The  posterior  interosseous  nerve  perforates  the  supinator  and  occasionally 
marks  the  line  of  separation  of  the  muscle  into  two  portions,  which  correspond  to  the  epicon- 
dylar  and  ulnar  portions  of  the  muscle.  The  muscle  is  indeed  a  composite  one,  a  portion  of  it 
being;  derived  from  the  superficial  extensor  layer  and  the  rest  of  it  from  the  deep  layer. 


2.    Extensor  Ossis  Metacarpi  Pollicis  (Fig.  580). 

Attachments. — The  extensor  of  the  metacarpal  bone  of  the  thumb  (m.  abduc- 
tor pollicis  longus)  arises  from  the  middle  third  of  the  posterior  surfaces  of  the  ulna, 

the  interosseous  membrane,  and 
Fig.  582.  the    radius.      It    passes    down- 

ward and  laterally,  and  its  ten- 
don passes  through  the  first 
compartment  beneath  the  pos- 
terior annular  ligament  to  be 
inserted  into  the  outer  side  of 
the  base  of  the  first  metacarpal 
bone. 

Nerve-Supply. — By  the 
posterior  interosseous  branch  of 
the  musculo-spiral  nerve  from 
the  sixth,  seventh,  and  eighth 
cervical  nerves. 

Action. — To  abduct  and 
slightly  extend  the  thumb  and, 
continuing  its  action,  to  abduct 
the  hand. 

Relations. — It  is  covered 
by  the  muscles  of  the  superficial 
layer  and  is  crossed  obliquely  by 
the  dorsal  interosseous  artery. 
Below  it  crosses  obliquely  the 
tendons  of  the  extensores  carpi 
radiales  and  the  radial  artery. 

Variations. — It  may  be  par- 
tially or  wholly  fused  with  the  ex- 
tensor brevis  pollicis.  Occasionally 
it  possesses  two  tendons,  one  of 
which  may  be  inserted  into  the  dor- 
sal carpal  ligament,  the  abductor 
brevis  pollicis,  or  the  trapezium. 

3.    Extensor  Brevis  Polli- 
cis (Fig.   580). 

Attachments. — The  short 
extensor  of  the  thumb  (m.  exten- 
sor pollicis  brevis),  also  termed 
the-  extensor  primi  internodii  pollicis,  lies  along  the  medial  border  of  the  extensor 
ossis  metacarpi  pollicis.  It  arises  from  the  interosseous  membrane  and  the  pos- 
terior surface  of  the  radius,  partly  under  cover  of  the  extensor  longus  pollicis,  and  its 
tendon,  after  passing  with  that  of  the  abductor  through  the  first  compartment  of  the 
posterior  annular  ligament,  is  inserted  into  the  base  of  the  first  phalanx  of  the  thumb. 
Nerve-Supply. — By  the  posterior  interosseous  branch  of  the  musculo-spiral 
nerve  from  the  sixth,  seventh,  and  eighth  cervical  nerves. 

Action. — To  abduct  the  thumb  and  extend  its  first  phalanx. 


Flexor  sublimis  digito 


Extensor  ossis 
metacarpi  pollicis 
Extensor  brevis  pollicis 
xtensor  carpi  radialis  longior 
Extensor  longus  pollicis 
carpi  radialis  brevior 

Radial  artery 


First  dorsal 
interosseus 
Radialis  indicis 
rtery 


PRACTICAL   CONSIDERATIONS:    THE   FOREARM.  603 

Relations. — The  relations  of  the  muscle  are  essentially  the  same  as  those  of 
the  extensor  ossis  metacarpi  pollicis. 

Variations.— The  extensor  brevis  and  the  metacarpal  extensor  of  the  thumb  are  differen- 
tiations of  a  common  muscle  and  show  indications  of  this  in  their  partial  or  complete  fusion. 
The  tendon  of  the  extensor  brevis  is  sometimes  continued  onward  to  the  terminal  phalanx  of 
the  thumb  or  may  send  a  slip  to  the  base  of  the  second  metacarpal. 

4.   Extensor  Longus  Pollicis  (Fig.  580). 

Attachments. — The  long  extensor  of  the  thumb  (tn.  extensor  pollicis  longus), 
also  known  as  the  extensor  secundi  internodii  pollicis,  is  an  elongated  fusiform  mus- 
cle lying  along  the  medial  border  of  the  extensor  brevis  pollicis,  which  it  partly 
covers.  It  arises  from  the  interosseous  membrane  and  posterior  surface  of  the  ulna  ; 
its  tendon  passes  downward  in  the  third  compartment  beneath  the  posterior  annular 
ligament  and,  crossing  over  the  tendons  of  the  extensores  carpi  radiales,  is  inserted 
into  the  base  of  the  terminal  phalanx  of  the  thumb. 

Nerve-Supply. — By  the  posterior  interosseous  branch  of  the  musculo-spiral 
nerve  from  the  sixth,  seventh,  and  eighth  cervical  nerves. 

Action. — To  extend  the  terminal  phalanx  of  the  thumb  and,  continuing  its 
action,  to  extend  and  at  the  same  time  slightly  adduct  the  thumb. 

5.   Extensor  Indicis  (Fig.  580). 

Attachments. — The  extensor  of  the  index-finger  (m.  extensor  indicis  proprius) 
lies  along  the  medial  border  of  the  extensor  longus  pollicis.  It  arises  from  the  in- 
terosseous membrane  and  the  dorsal  surface  of  the  ulna.  Its  tendon  passes,  along 
with  the  tendons  of  the  extensor  communis  digitorum,  through  the  fourth  compart- 
ment beneath  the  posterior  annular  ligament,  and  eventually  is  inserted  with  the 
tendon  of  the  common  extensor  which  passes  to  the  index-finger. 

Nerve-Supply. — By  the  posterior  interosseous  branch  of  the  musculo-spiral 
nerve  from  the  seventh  and  eighth  cervical  nerves. 

Action. — To  extend  the  index-finger. 

Variations. — The  extensor  indicis  may  be  wanting,  or  its  tendon  may  send  slips  to  the 
third  and  fourth  digits.  Occasionally  a  muscle  arises  from  the  ulna,  below  the  origin  of  the  ex- 
tensor indicis,  and  passes  to  the  third  or  fourth  finger,  forming  what  has  been  termed  the  extensor 
digiti  medii  (vet  annularis)  proprius.  This  muscle  represents  an  additional  portion  of  the  deep 
extensor  layer  which  normally  disappears. 

PRACTICAL  CONSIDERATIONS  :    THE    FOREARM. 

The  fascia  descending  from  the  arm  to  the  forearm  should  be  studied  anteriorly 
with  relation  to  the  expansion  known  as  the  bicipital  aponeurosis  (Fig.  570), — one 
of  the  "  two  inferior  tendons  of  the  biceps"  of  the  older  anatomists, — which  becomes 
continuous  with  the  deep  fascia  of  the  forearm,  and  thus,  through  the  origin  from  its 
under  surface  of  fibres  of  many  of  the  superficial  muscles  of  that  region,  associates 
their  action  with  that  of  the  biceps  itself.  Partly  for  this  reason  injuries  and  diseases 
affecting  the  bicipital  region  are  sometimes  associated  with  a  certain  weakness  of 
grasp  and  feebleness  of  wrist  flexion.  The  facts  that  only  this  aponeurotic  expansion 
separates  the  median  basilic  vein  from  the  brachial  artery,  and  that  in  persons  of  poor 
muscular  development  it  is  often  so  thin  as  scarcely  to  constitute  a  recognizable 
layer,  were  of  practical  importance  when  phlebotomy  of  the  median  basilic  was  fre- 
quent. Arterio-venous  aneurism  from  accidental  puncture  of  the  artery  was  then 
quite  common. 

Posteriorly  the  outer  aponeurotic  expansion  of  the  triceps,  running  over  the 
anconeus  to  become  continuous  with  the  deep  fascia  of  the  forearm,  is  of  importance 
in  its  relation  to  the  power  of  extension  of  the  forearm  after  excision  of  the  elbow 
(page  308). 

The  fascia  of  the  forearm,  besides  giving  origin  to  many  fibres  of  the  subjacent 
muscles,  as  has  been  noted  above,  envelops  the  forearm  completely,  being  continu- 


604 


HUMAN   ANATOMY. 


Palmaris  longus 
Flexor  carpi  radialis 
Pronator  radii  teres 
Radial  artery 
Radial  nerve 


Flexor  longus  pollicis 
Median  nerve 

artery 
sublii 


ous  at  the  wrist  with  the  anterior  and  posterior  annular  ligaments.  The  septa  which 
run  in  from  it  to  be  attached  to  the  sides  of  the  ulna  and  radius  divide  the  forearm, 
with  the  aid  of  the  interosseous  membrane,  into  two  musculo-aponeurotic  spaces,  an 
antero-external  and  a  posterior  (Fig.  583).  The  former  contains  numerous  muscles 
and  the  main  vessels  and  nerves,  the  latter  is  almost  entirely  muscular. 

The  interpenetration  of  these  main  septa  ajid  of  the  intermuscular  fascia  by 
nervo-vascular  structures  renders  them  of  slight  importance  in  limiting  the  spread  of 
infectious  disease  or  of  collections  of  blood  or  pus.  But  in  the  not  infrequent  cases 
of  incised  wounds  severing  the  muscles  and  tendons  of  this  region  it  may  systematize 
the  search  for  and  reunion  of  the  divided  structures  if  the  somewhat  artificial  topog- 
raphy, as  described  by  Tillaux,  is  borne  in  mind.  The  antero-external  compart- 
ment is  thus  regarded  as  including  four  spaces.  1.  That  between  the  skin  and  the 
first  muscular  layer, — the  palmaris,  flexor  carpi  ulnaris,  pronator  radii  teres,  etc., — 
and  containing  the  internal  cutaneous  and  musculo-cutaneous  nerves,  the  perforating 
branches  of  the  radial  and  ulnar  nerves,  the  superficial  veins,  and  sometimes  the 
ulnar  artery  when  there  is  a  high  bifurcation  of  the  brachial.  2.  That  between  the  first 
muscular  layer  and  the  flexor  sublimis,  with  the  brachio-radialis  and  short  supinator 

externally.     This  contains 
Fig.  5S3.  the   radial   nerve,   artery, 

and  veins.  3.  That  be- 
tween the  flexor  sublimis 
and  the  flexor  profundus 
and  flexor  longus  pollicis. 
This  contains  the  median 
nerve  and  the  ulnar  nerve 
and  vessels.  4.  That  be- 
tween the  last-named  mus- 
cles and  the  interosseous 
membrane,  containing  the 
anterior  interosseous  ves- 
sels and  the  interosseous 
nerve. 

In  the  posterior  com- 
partment are  to  be  found, 
in  addition  to  the  exten- 
sors and  the  anconeus, 
only  the  posterior  inter- 
osseous vessels  and  nerve 
(Fig.  583)- 

Fractures  of  the  neck 
of  the  radius  (between  the  head  and  the  tuberosity)  are  very  rare,  as  it  is  covered  and 
protected  from  direct  violence  by  the  long  and  short  supinators  and  the  long  and 
short  radial  extensors.  Angular  displacement  forward  is  thought  to  be  caused  by 
the  action  of  the  biceps  on  the  upper  end  of  the  lower  fragment.  The  upper  frag- 
ment is  rotated  outward  by  the  supinator  brevis.  Fracture  of  the  radius  below  its 
tubercle  and  above  the  insertion  of  the  pronator  radii  teres  (a  little  above  the  middle 
of  the  outer  side  of  the  bone)  is  followed  by  supination  and  flexion  of  the  upper  frag- 
ment by  the  biceps  and  supinator  brevis.  The  lower  fragment  is  pronated  and  drawn 
towards  the  ulna  by  the  pronators. 

It  is  well  to  treat  cases  of  this  fracture  with  the  forearm  in  moderate  supination, 
so  as  to  approximate  the  fragments  and  preserve  the  axis  of  the  bone  and  the  future 
usefulness  of  the  supinators. 

In  fracture  of  the  radius  below  the  insertion  of  the  pronator  radii  teres  the 
upper  fragment  is  flexed  by  the  biceps,  so  that  its  lower  end  can  sometimes  be  seen 
and  felt  on  the  front  of  the  forearm  just  above  the  middle,  and  is  sometimes  pronated 
by  the  pronator  radii  teres  ;  the  lower  fragment  is  drawn  towards  the  ulna  by  the 
pronator  quadratus,  aided  by  the  action  of  the  brachio-radialis  on  the  styloid  process 
(Fig.  584). 

In  the  usual  position  in  which  such  fractures  are  treated,  the  flexion  of  the  elbow 


Extensor 
carpi  rad 
brev . 

Supinat 
Extensor  commun 
Post,  inteross.  vessels 

Interosseous  membrane  \  \        Extensor  carpi  ulnaris 

Extensor  ossis  metacarpi  pollicis  Extensor  longus  pollic 

Section  across  middle  of  right  forearm. 


PRACTICAL    CONSIDERATIONS  :    THE    FOREARM. 


605 


Fig.  5S4. 


and  the  mid-position  between  pronation  and  supination  sufficiently  relax  the  biceps 
and  the  pronator  radii  teres.      The  weight  of  the  hand  in  adduction  overcomes  the 
pull   of    the    brachio-radialis 
and  pronator  quadratus. 

Fracture  of  both  bones, 
from  either  direct  or  indirect 
violence,  usually  takes  place 
below  the  middle  of  the  fore- 
arm, as  there  the  muscular 
masses  which  protect  the 
upper  half  of  the  radius  from 
direct  violence  have  largely 
been  replaced  by  tendons, 
the  ulna  is  slender  and  weak,  Pronai 
and  the  opposing  forces  rep- 
resented by  the  biceps  and 
brachialis  anticus  above  and 
the  weight  or  force  applied 
through  the  hand  expend 
themselves.  Thus  Malgaigne 
(quoted  by  Agnew)  reports 
a  case  in  which  both  bones  Quadrat 
were  broken  by  muscular 
action  alone  while  the  patient 
was  carrying  weight  in  the 
form  of  a  shovelful  of  dirt. 
When  the  resulting  deform- 
ity is  due  chiefly  to  the  con- 
traction of  muscles,  it  is  apt 
to  consist  in  flexion  of  both 
upper  fragments  by  the  bi- 
ceps and  brachialis  anticus, 
supination  of  the  upper  frag- 
ment   Of    the     radius    by     the      Dissection  of  fracture  of  radii 

biceps  and  supinator  brevis,  the  two  pronator  m«st 

and  approximation  of  the  two 

lower  fragments  by  the  pronator  quadratus.      Much  overlapping  and  shortening  are 

usually  prevented  by  the  untorn  fibres  of  the  interosseous  membrane. 

During  the  period  of  repair  the  mid-position — between  pronation  and  supination 
— preserves  the  parallelism  of    the  two  bones,   maintains  the  interosseous  space  at 

almost  its  greatest 
Fig.  5S6.  width,    relaxes    (in 

conjunction  with 
the  flexion  of  the 
elbow)  the  muscles 
involved  so  far  as 
is  possible,  and  by 
the  weight  of  the 
hand  dropping  to 
the  ulnar  side  over- 
comes the  resist- 
ance of  others,  espe- 
cially of  the  brachio- 
radialis. 

The  large  pro- 
portion   of  the    re- 
turn      current      of 
blood  that  is  carried  by  the  superficial  veins  of  the  forearm  makes  it  especially  impor- 
tant that  the  splints  used  should  be  so  broad  that  the  bandage  does  not  undulv  com- 


V' 


-~ 


Dissection  of  fracture  of  ole- 
process  of  left  ulna  ;  joint 
opened  from  behind. 


Brachio-radialis 
Ext.  longus  pollii 


Ext.  brevi 


nd  turned  forward 


Radial  artery 
tendons 
of  upper  fragment 
et.  poll., 


Dissection  of  Colle 


elation  of  tendons  and  radial 


6o6 


HUMAN    ANATOMY. 


press  the  soft  tissues  ;  while  the  ease  with  which  both  veins  and  arteries  may  be 
obstructed  at  the  bend  of  the  elbow  should  lead  to  careful  avoidance  of  pressure  in 
that  region  from  the  upper  end  of  the  palmar  splint. 

The  preservation  of  the  interosseous  space  is  favored  by  the  omission  of  the 
primary  roller  bandage  and  by  the  avoidance  of  direct  pressure  upon  the  soft  parts 
by  the  bandage  used  to  retain  the  splints. 

THE   MUSCLES   OF   THE   HAND. 

The  Deep  Fascia  of  the  Hand. — The  deep  fascia  of  the  palmar  surface 
of  the  hand  is  usually  regarded  as  being  represented  by  the  palmar  aponewosis,  a 
firm  sheet  of  connective  tissue  which  occupies  the  palm  of  the  hand  and  lies  imme- 

Fig.  5S7. 


Thenar  eminence  covered_ 
with  lateral  portion  of 
palmar  fascia 


Hypothenar  eminence 


Digital  arteries 


>-  Palmar  fascia,  central 
portion 

Palmar  fascia,  lateral  portion 


— Digital  nerves 

Superficial  transverse  ligament 


Superficial  dissection  of  hand,  showing  palmar  fascia. 


diately  beneath  the  skin.  This  structure  represents,  however,  the  superficial  layer 
of  a  thick  aponeurosis  which  occurs  in  the  lower  vertebrates,  receiving  the  insertion 
of  the  antibrachial  flexors  and  giving  origin  to  the  digital  flexors.  From  the  proxi- 
mal portion  of  this  aponeurosis  there  is  formed,  however,  the  anterior  annular  liga- 
ment, and  this  may  be  considered  as  a  portion  of  the  palmar  aponeurosis. 

The  latter  (Fig.  587),  often  called  the  palmar  fascia,  is  a  fan-shaped  sheet 
whose  apex  is  directed  proximally,  receiving  the  insertion  of  the  palmaris  longus  and 
being  to  a  certain  extent  continuous  with  the  anterior  annular  ligament.      It  reaches 


THE    MUSCLES    OF   THE    HAND.  607 

its  greatest  breadth  over  the  distal  portions  of  the  metacarpals,  and  is  continued 
onward  as  four  more  or  less  distinct  bands,  which  are  inserted  into  the  integument  at 
the  bases  of  the  second,  third,  fourth,  and  fifth  fingers.  A  little  below  the  lower 
edge  of  the  aponeurosis  transverse  bands  of  fascia  (fasciculi  transversi)  stretch  across 
between  the  same  fingers,  lying  immediately  beneath  the  skin  and  being  connected 
to  a  greater  or  less  extent  with  one  another.  These  bands  constitute  the  superficial 
transverse  metacarpal  ligament  beneath  the  webs  of  the  fingers. 

The  anterior  a?iniclar  ligament  (ligamentum  carpi  transversum )  (Fig.  578)  is  a 
strong  band  which  stretches  across  from  the  trapezium  and  scaphoid  bones  of  the 
carpus  on  the  radial  side  to  the  pisiform  and  unciform  bones  on  the  ulnar  side, 
forming  a  bridge  across  the  groove  on  the  anterior  surface  of  the  carpus  which  trans- 
mits the  tendons  of  the  long  flexors  and  of  the  flexor  carpi  radialis  and  the  median 
nerve.  The  canal  so  formed  is  divided  by  a  partition  into  a  small  radial  compart- 
ment through  which  the  flexor  carpi  radialis  passes,  and  a  large  ulnar  one  which 
gives  passage  to  the  other  structures  mentioned.  The  tendons  are  enclosed  within 
synovial  sacs  which  extend  downward  to  about  the  middle  of  the  palm  and  upward 
to  a  short  distance  above  the  upper  edge  of  the  ligament.  The  sac  which  surrounds 
the  flexor  longus  pollicis  is  usually  separate  from  that  which  surrounds  the  remaining 
tendons  of  the  ulnar  compartment  ;  occasionally  the  portion  surrounding  the  tendons 
of  the  index-finger  is  also  separate. 

Towards  either  side  of  the  palmar  surface  of  the  hand  the  palmar  fascia  forms  a 
thin  covering  for  thenar  and  hypothenar  eminences  formed  by  the  superficial  muscles 
of  the  thumb  and  the  little  finger  respectively.  Upon  the  dorsal  surface  the  fascia  is 
thin,  and  is  continued  downward  from  the  lower  border  of  the  posterior  annular 
ligament  over  the  extensor  tendons  to  the  fingers,  where  it  unites  with  the  aponeu- 
roses of  the  tendons. 

(a)   THE  PRE-AXIAL  MUSCLES. 

The  pre-axial  muscles  of  the  hand  are  to  be  regarded,  from  the  comparative 
stand-point,  as  being  arranged  in  five  layers.  Although  these  layers  become  con- 
fused to  a  certain  extent  in  the  human  hand,  it  will,  nevertheless,  aid  in  the  proper 
understanding  of  their  relations  to  group  them  according  to  the  primary  layers  from 
which  they  are  derived. 

(aa)    The  Muscles  of  the  First  Layer. 

1.  Palmaris  brevis.  4.    Flexor  brevis  pollicis. 

2.  Abductor  pollicis.  5.    Abductor  minimi  digiti. 

3.  Opponens  pollicis.  6.    Opponens  minimi  digiti. 

7.    Flexor  brevis  minimi  digiti. 

The  most  superficial  layer  of  the  palmar  muscles  in  the  lower  vertebrates  takes 
its  origin  from  the  palmar  aponeurosis.  The  greater  portion  of  the  layer,  as  has 
already  been  pointed  out,  becomes  converted  in  the  mammalia  into  the  palmar  por- 
tions of  the  tendons  of  the  flexor  sublimis  digitorum,  and  it  is  only  towards  either 
margin  of  the  hand  that  it  persists  as  muscles,  which  show  indications  of  their 
primary  relations  in  their  origin  from  the  palmar  aponeurosis  or  the  anterior  annular 
ligament. 

1.    Palmaris  Brevis  (Fig.   576). 

Attachments. — The  palmaris  brevis  is  a  thin  quadrangular  sheet  which  lies 
immediately  beneath  the  skin  of  the  hypothenar  eminence.  It  arises  from  the 
proximal  portion  of  the  ulnar  border  of  the  palmar  aponeurosis  and  is  inserted  into 
the  skin  of  the  ulnar  border  of  the  hand. 

Nerve-Supply. — By  the  superficial  division  of  the  ulnar  nerve  from  the  first 
thoracic  nerve. 

Action. — To  wrinkle  the  skin  upon  the  ulnar  border  of  the  hand,  deepening 
the  hollow  of  the  hand. 

Variations. — The  muscle  may  be  greatly  reduced  in  size  and  is  occasionally  wanting. 


6o8  HUMAN   ANATOMY. 

2.  Abductor  Pollicis  (Fig.   577). 

Attachments. — The  abductor  of  the  thumb  (m.  abductor  pollicis  brevis)  is  the 
most  superficial  muscle  of  the  thenar  eminence.  It  arises  from  the  anterior  annular 
ligament  and  from  the  scaphoid  bone  or  the  trapezium  and  passes  distally  to  be  in- 
serted along  with  the  flexor  brevis  pollicis  into  the  radial  side  of  the  base  of  the  first 
phalanx  of  the  thumb  and  into  the  sheath  of  the  tendon  of  the  extensor  longus  pollicis. 

Nerve-Supply. — By  the  median  nerve  from  the  sixth  and  seventh  cervical 
nerves. 

Action. — To  flex  and  abduct  the  thumb. 

Variations. — The  portion  of  the  muscle  arising  from  the  carpus  is  sometimes  separate  from 
that  taking  origin  from  the  transverse  carpal  ligament.  Slips  are  occasionally  sent  to  the  abduc- 
tor from  the  extensores  carpi  radiales,  the  extensor  ossis  metacarpi  pollicis,  the  opponens  pol- 
licis, and  the  flexor  brevis  pollicis. 

3.    Opponens  Pollicis  (Figs.   578,  588). 

Attachments. — The  opponens  pollicis  is  almost  completely  covered  by  the 
abductor  pollicis.  It  arises  from  the  anterior  annular  ligament  and  from  the  trape- 
zium, and  is  inserted  into  the  whole  length  of  the  radial  border  of  the  first  metacarpal. 

Nerve-Supply. — By  the  median  nerve  from  the  sixth  and  seventh  cervical 
nerves. 

Action. — To  flex  and  adduct  the  thumb,  opposing  it  to  the  other  fingers. 

4.    Flexor  Brevis  Pollicis  (Figs.   578,   588). 

Attachments. — The  flexor  brevis  pollicis  lies  along  the  lower  (ulnar)  border 
of  the  opponens  pollicis.  It  arises  from  the  lower  border  of  the  anterior  annular 
ligament  and  is  inserted,  along  with  the  abductor  pollicis,'  into  the  radial  side  of  the 
base  of  the  first  phalanx  of  the  thumb. 

The  muscle  above  described  is  usually  regarded  by  English  anatomists  as  representing  the 
outer  or  radial  head  of  the  flexor  brevis,  a  second  inner  or  ulnar  head  being  included  as  part  of 
that  muscle.  Concerning  the  inner  head  three  views  are  held  :  (a)  no  inner  head  is  recognized, 
the  small  slip  arising  from  the  ulnar  side  of  the  base  of  the  first  metacarpal  bone  and  passing 
downward  to  be  inserted  with  the  adductor  pollicis  into  the  base  of  the  first  phalanx,  which  by 
many  English  anatomists  is  regarded  as  a  small  inner  head  of  the  flexor  brevis,  being  described 
as  an  additional  (first)  palmar  interosseus  (page  612)  ;  (6)  the  small  slip  just  noted  is  the  inner 
or  ulnar  head  of  the  flexor  brevis  ;  (r)  the  small  slip  and  all  the  fibres  described  as  forming  the 
adductor  obliquus  (page  610)  are  regarded  as  the  inner  head  of  the  flexor  brevis.  The  first 
view,  adopted  by  German  anatomists,  is  here  followed. 

Nerve-Supply. — By  the  median  nerve  from  the  sixth  and  seventh  cervical 
nerves. 

Action. — To  flex  the  first  phalanx  of  the  thumb. 

Variations. — The  muscle  is  sometimes  intimately  connected  with  the  abductor  pollicis  and 
opponens  pollicis. 

5.  Abductor  Minimi  Digiti  (Fig.   577). 

Attachments. — The  abductor  of  the  little  finger  (m.  abductor  digiti  quiriti) 
occupies  the  ulnar  border  of  the  hand.  It  arises  from  the  anterior  annular  ligament 
and  from  the  pisiform  bone  and  is  inserted  into  the  ulnar  side  of  the  base  of  the  first 
phalanx  of  the  little  finger. 

Nerve-Supply. — By  the  deep  division  of  the  ulnar  nerve  from  the  eighth  cer- 
vical and  first  thoracic  nerves. 

Action. — To  abduct  the  fifth  finger. 

6.  Opponens  Minimi  Digiti  (Fig.   578). 
Attachments. — This  muscle   (m.  opponens  digiti  quinti)   is  almost   completely 

covered  by  the  abductor  and  short  flexor  of  the  little  finger.  It  arises  from  the 
anterior  annular  ligament  and  the  uncinate  process  of  the  unciform  bone  and  is  in- 
serted into  the  whole  of  the  ulnar  border  of  the  fifth  metacarpal  bone. 


THE    MUSCLES    OF    THE    HAND. 


609 


Nerve-Supply. — By  the  deep  division  of  the  ulnar  nerve  from  the  eighth  cer- 
vical and  first  thoracic  nerves. 

Action. — To  flex  and  at  the  same  time  adduct  the  fifth  metacarpal. 

7.    Flexor  Brevis  Minimi  Digiti  (Figs.  577,  578;. 

Attachments.  —The   short   flexor  of  the  little  finger  (m.  flexor   brevis    digiti 
quinti)  lies  along  the  lateral  (radial)  border  of  the  abductor  minimi  digiti.      It  arises 

Fig.  58S. 


Radius- 
Anterior  interosseous  artery 


Flexor  brevis  pollicis  /& 

First  palmar  interosseus         ..&%?. 


Pronator  quadratus 


Flexor  carpi  ulnaris  tendo 


Pisiform  bone 

Adductor  pollicis,  oblique  portion 


Third  palmar  interosseus 


Fourth  palmar  interosseus 
Fourth  dorsal  interosseus 


Deep  dissection  of  wrist  and  hand,  showing  pronator  quadratus  and  short  muscles  of  thumb. 

from  the  anterior  annular  ligament  and  the  uncinate  process  of  the  uncinate  bone 
and  is  inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  little  finger. 

Nerve-Supply. — By  the  deep  division  of  the  ulnar  nerve  from  the  eighth  cer- 
vical and  first  thoracic  nerves. 

Action. — To  flex  and  slightly  abduct  the  first  phalanx  of  the  little  finger. 

Variations.— The  flexor  brevis  and  opponens  minimi  digiti  are  often  united  by  muscle- 
bundles  and  may  even  be  completely  fused. 


610  HUMAN    ANATOMY. 

(66)  The  Muscles  of  the  Second  Layer. 
In  the  lower  vertebrates  the  second  layer  also  arises  from  the  palmar  aponeu- 
rosis, but  from  its  deeper  layers.  These,  as  has  been  stated  (page  597),  differentiate 
into  the  palmar  portions  of  the  tendons  of  the  flexor  profundus  digitorum,  and  in 
the  mammalia  the  muscles  retain  their  primary  origin  and  arise  from  those  tendons 
forming  the  lumbrical  muscles. 

I.      LUMBRICALES    (Fig.    578). 

Attachments. — The  lumbricals  are  four  slender,  band-like  muscles,  situated 
in  the  palm  of  the  hand.  Counting  from  the  radial  side  of  the  hand,  the  first  and 
seco?id  lumbricals  arise  from  the  radial  side  of  the  flexor  profundus  tendons  to  the 
index  and  middle  fingers  respectively,  while  the  third  one  arises  from  the  adjacent 
sides  of  the  tendons  to  the  middle  and  ring  fingers,  and  the  fourth  from  those  of  the 
tendons  to  the  ring  and  little  fingers.  The  muscles  pass  distally  into  slender  tendons 
which  are  continued  to  the  radial  side  of  the  first  phalanges  of  the  second,  third, 
fourth,  and  fifth  fingers,  and  are  inserted  into  the  membranous  expansions  of  the 
tendons  of  the  extensor  communis  digitorum  to  those  fingers. 

Nerve-Supply. — The  first  and  second  lumbricals  are  supplied  by  the  median 
nerve  from  the  sixth  and  seventh  cervical  nerves  ;  the  third  and  fourth  by  the  deep 
division  of  the  ulnar  nerve  from  the  eighth  cervical  and  first  thoracic  nerves. 

Action. — To  flex  the  first  phalanges  of  the  second,  third,  fourth,  and  fifth 
fingers.  At  the  same  time,  by  their  traction  upon  the  extensor  tendons,  they  will 
tend  to  keep  the  second  and  third  phalanges  extended. 

Variations. — Variations  in  the  arrangement  of  the  lumbricals,  and  especially  of  the  third 
and  fourth,  are  not  uncommon.  The  tendon  of  each  of  these  muscles  may  bifurcate  and  be  in- 
serted into  the  adjacent  sides  of  the  third  and  fourth  or  fourth  and  fifth  fingers,  and  more 
rarely  the  sole  insertions  may  be  into  the  ulnar  sides  of  the  first  phalanges  of  the  middle 
and  ring  fingers.  The  third  lumbrical  is  frequently  supplied  wholly  or  in  part  from  the  median 
nerve. 

(cc)  The  Muscle  of  the  Third  Layer. 
In  the  lower  vertebrates  the  third  layer  consists  of  muscles  which  arise  from  the 
carpal  and  metacarpal  bones  and  pass  to  each  of  the  digits.  In  the  mammalia  they 
become  greatly  reduced  in  number,  frequently  persisting,  however,  in  connection 
with  the  thumb,  index,  and  little  fingers,  but  in  man  they  are  represented  only  by 
an  adductor  pollicis. 

1.  Adductor  Pollicis  (Figs.  578,  588). 

Attachments. — The  adductor  pollicis  is  a  flat  triangular  muscle  which  rests 
upon  the  metacarpal  bones  and  the  interosseous  muscles.  It  may  be  regarded  as 
consisting  of  two  portions.  The  portio  obliqua  (often  described  as  a  distinct  muscle, 
the  adductor  obliquus  pollicis')  arises  from  the  trapezium,  trapezoid,  and  os  magnum 
and  from  the  bases  of  the  second  and  third  metacarpals.  Its  fibres  are  directed  dis- 
tally and  radially,  and  are  inserted  by  a  tendon,  in  which  a  sesamoid  bone  is  usually 
developed,  into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  thumb.  It 
also  sends  off  a  slip  which  passes  beneath  the  tendon  of  the  flexor  longus  pollicis  to 
be  inserted  into  the  radial  side  of  the  base  of  the  first  phalanx  of  the  thumb  along 
with  the  flexor  brevis  pollicis. 

The  portio  transversa  (often  described  as  the  adductor  transversus  pollicis) 
arises  from  the  lower  two-thirds  of  the  volar  surface  of  the  third  metacarpal,  and  its 
fibres  pass  almost  directly  radially  to  be  inserted  into  the  ulnar  side  of  the  base  of 
the  first  phalanx  of  the  thumb. 

Nerve-Supply. — By  the  deep  division  of  the  ulnar  nerve  from  the  eighth 
cervical  and  first  thoracic  nerves. 

Action. — To  adduct  the  thumb. 

Relations. — The  adductor  pollicis  is  covered  by  the  tendons  of  the  flexor 
profundus  digitorum  for  the  second  and  third  fingers  and  by  the  first  and  second 
lumbricals.  It  conceals  the  interosseous  muscles  of  the  two  radial  intermetacarpal 
intervals  and  also  the  radial  artery  and  the  arteria  princeps  pollicis.  The  deep 
palmar  arch  passes  between  the  two  portions  of  the  muscle,  near  their  origins. 


THE    MUSCLES    OF    THE    HAND. 


611 


Flexor  carpi  radial 


(dd)  The  Muscles  of  the  Fourth  and  Fifth  Layers. 
i.    Interossei  volares.  2.    Interossei  dorsales. 

In  the  lower  vertebrates  the  musculature  of  the  fourth  palmar  layer  consists  of 
a  pair  of  muscles  for  each  digit,  arising  from  the  carpal  and  metacarpal  bones  and 
inserting  into  either  side  of  the  base  of  the  first  phalanx.  The  fifth  layer  lies 
dorsal  to  these,  and  consists  of  four  muscular  bands,  which  extend  slightly  obliquely 
across  the  four  inter- 
metacarpal spaces.  Fig.  589. 

In  the  mammalia 
a  shifting  of  the  in- 
sertion of  one  of  the 
muscles  of  the  pairs 
belonging  to  the  first 
and  fifth  digits  takes 
place,  so  that  they  are 
attached  to  the  radial 
and  ulnar  sides  re- 
spectively of  the  ad- 
jacent second  and 
fourth  digits,  uniting 
with  the  correspond- 
ing members  of  the 
pairs  belonging  to 
those  digits.  With 
the  compound  mus- 
cles so  formed  the 
first  and  fourth  inter- 
metacarpal muscles 
unite  to  form  the  first 
and  fourth  dorsal  in- 
terossei, these  two 
muscles  being  com- 
posed, accordingly, 
by  the  fusion  of  three 
primary  muscles. 

The  second  and 
third  intermetacarpal 
muscles  unitewith  the 
radial  and  ulnar  mem- 
bers respectively  of 
the  pair  belonging  to 
the  third  digit,  and 
form  with  these  the 
second  and  third  dor- 
sal interossei. 

The  remaining 
members  of  the  pairs 
belonging  to  the  first, 
second,  fourth,  and 
fifth  digits  persist  as 

independent  muscles,  forming  what  are  termed  the  volar  interossei,  whose  arrange- 
ment is  consequently  complementary  to  that  of  the  dorsal  interossei. 

The  intermetacarpal  muscles  occupy  the  most  dorsal  position  of  all  the  palmar 
muscles,  and  it  is  probably  owing  to  their  participation  in  the  formation  of  the 
dorsal  interossei  that  these  possess  an  almost  dorsal  position  in  the  hand.  They  are 
clearly,  however,  of  palmar  origin  and  are  supplied  by  pre-axial  nerves. 


6l2 


HUMAN   ANATOMY. 


i.   Interossei  Volares  (Fig.  589). 

Attachments. — The  volar  or  palmar  interossei  are  four  slender  muscles 
situated  in  the  intervals  between  the  metacarpal  bones  and  resting  upon  the  in- 
terossei dorsales.  The  first  and  second  muscles,  counting  from  the  radial  side,  arise 
from  the  ulnar  side  of  the  bases  of  the  first  and  second  metacarpals,  and  are  inserted 
into  the  ulnar  side  of  the  base  of  the  first  phalanx  and,  in  the  case  of  the  second 
muscle,  also  into  the   membranous   expansion  of  the  long   extensor  tendon  of  the 

Fig.  590. 


xtensor  carpi  radialis  longior  tendon 
Extensor  carpi  radialis  brevior 


Second  dorsal  interosseus 

Third  dorsal  interosseus 
Fourth  dorsal  interosseus 


Extensor  communis 
digitorum  tendons 


CI    ;   l      : 

1  f 


\3 

Dissection  of  back  of  hand,  showing  dorsal  interossei  and  insertion  of  extensor  tendons. 

corresponding  digit.  The  third  and  fourth  muscles  arise  from  the  radial  side  of  the 
fourth  and  fifth  metacarpals,  and  are  inserted  similarly  to  the  second  muscle,  but 
into  the  radial  sides  of  the  fourth  and  fifth  digits. 

Only  three  palmar  interossei  are  usually  described  by  English  anatomists,  the  muscle  in- 
cluded in  the  series  by  the  German  school  as  the  first  interosseus  (m.  interosseus  primus  volaris) 
being  regarded  as  the  small  ulnar  head  of  the  flexor  brevis  pollicis  (page  608).  The  inclusion 
of  this  muscle  in  the  series  of  palmar  interossei  is  warranted  by  its  morphological  relations. 

Nerve-Supply. — By  the  deep  division  of  the  ulnar  nerve  from  the  eighth 
cervical  and  first  thoracic  nerves. 

Action. — To  draw  the  first,  second,  fourth,  and  fifth  digits  towards  the  middle 
finger  and  to  flex  the  first  phalanx  of  the  same  digits. 


PRACTICAL    CONSIDERATIONS  :    WRIST    AND    HAND.  613 

Variations.— The  first  volar  interosseus  is  the  most  slender  of  the  series  and  is  covered  by 
the  oblique  portion  of  the  adductor  pollicis,  with  which  it  may  be  practically  incorporated. 
Occasionally  it  is  so  reduced  in  size  as  to  appear  to  be  wanting. 

2.   Interossei  Dorsales  (Fig.  590). 

Attachments. — The  dorsal  interossei  are  also  four  in  number  and  lie  in  the 
intervals  between  the  metacarpal  bones,  dorsal  to  the  volar  interossei.  Each  is  a 
bipinnate  muscle  arising  from  the  adjacent  surfaces  of  the  metacarpals  which  bound 
the  interspace  in  which  the  muscle  lies.  The  first  and  second  muscles,  counting 
from  the  radial  side,  are  inserted  into  the  radial  side  of  the  base  of  the  first  phalanx 
and  into  the  membranous  expansion  of  the  extensor  tendons  of  the  second  and 
third  fingers,  while  the  third  and  fourth  are  inserted  similarly  into  the  ulnar  sides 
of  the  third  and  fourth  fingers. 

Nerve-Supply. — By  the  deep  division  of  the  ulnar  nerve  from  the  eighth 
cervical  and  first  thoracic  nerves. 

Action. — The  first  and  fourth  muscles  draw  the  second  and  fourth  fingers 
away  from  the  third,  while  the  second  and  third  draw  the  third  finger  radially  or 
ulnarly,  as  the  case  may  be.  All  the  muscles  flex  the  first  phalanx  of  the  digits  to 
which  they  are  attached. 

Variations. — Occasionally  the  second  dorsal  interosseus  is  inserted  into  the  base  of  the  first 
phalanx  of  the  index-finger,  upon  its  ulnar  side. 

(b)  THE   POST-AXIAL  MUSCLE. 

Normally  no  post-axial  muscles  exist  in  the  human  hand.  Occasionally,  however,  an  ex- 
tensor brevis  digitorum  mantis  is  more  or  less  perfectly  developed.  It  arises  from  the  dorsum 
of  the  carpus,  or  sometimes  from  the  lower  end  of  the  radius  and  ulna,  and  passes  distally  into 
a  varying  number  of  tendons.  Most  frequently  the  muscle  is  small  and  gives  rise  to  but  a  single 
tendon,  which  joins  with  the  tendon  of  the  extensor  digitorum  communis  of  either  the  second 
or  third  digit.  Sometimes  two  tendons  occur,  passing  to  the  second  and  third  digits,  and  more 
rarely  three  have  been  observed,  passing  to  the  second,  third,  and  fourth  fingers.  In  a  single 
case  a  fourth  tendon  was  observed  which  terminated  upon  the  dorsal  surface  of  the  fifth 
metacarpal. 

PRACTICAL    CONSIDERATIONS. 

The  Wrist  and  Hand. — The  skin  of  the  wrist  and  of  the  back  of  the  hand  is 
thin  and  freely  movable  and  contains  numerous  hair-follicles  and  sebaceous  glands. 
These  structures  are  absent  in  the  palm  and  on  the  palmar  and  lateral  surfaces  of  the 
fingers,  as  well  as  on  the  dorsal  surface  of  the  terminal  phalanges.  Sudoriparous 
glands  are,  on  the  contrary,  relatively  more  numerous  in  the  palms  of  the  hands 
than  on  any  other  part  of  the  body  surface. 

These  anatomical  conditions  and  the  existence  of  the  subungual  and  periungual 
spaces  and  irregularities  render  the  sterilization  of  the  hands  for  surgical  purposes 
very  difficult. 

The  absence  of  hair-follicles  and  of  sebaceous  glands  explains  the  freedom  of 
the  palm  from  the  superficial  furuncular  infections  that  are  so  common  on  the  dorsum. 

In  the  palm  the  subcutaneous  connective  tissue,  like  that  in  the  plantar  region 
and  in  the  scalp  between  the  skin  and  aponeurosis,  is  very  dense.  This  similarity 
has  already  been  alluded  to  (page  491 )  in  relation  to  the  absence  of  hair-follicles  in 
the  two  former  regions  and  the  frequency  of  baldness  in  the  latter. 

On  the  dorsal  surface  the  subcutaneous  tissue  is  loose.  As  a  result,  in  whitlow, 
in  palmar  abscess,  in  hemorrhagic  extravasation,  in  oedema  or  cellulitis,  the  swelling 
is  apt  to  be  much  more  marked  on  the  dorsum  and  may  be  misleading  as  to  the 
real  seat  of  the  trouble.  Abscesses  immediately  beneath  the  palmar  fascia  will 
sometimes  point  in  a  metacarpal  space  on  the  dorsum. 

The  thickness  and  close  adhesion  of  the  skin  to  the  dense  fascia  beneath,  while 
admirably  protecting  the  vessels  and  nerves  of  the  palm  and  enabling  it  to  withstand 
pressure  and  friction,  greatly  increase  the  pain  in  cutaneous  or  subcutaneous  infections. 
On  account  of  this  same  adhesion,  superficial  wounds  of  the  palm  do  not  gape,  and 
heal  readily  if  non-infected  and  kept  at  rest. 


614 


HUMAN   ANATOMY. 


Ext.  carp,  ulnaris 


Ext.  communis 


"  It  must  be  noted  that  the  front  of  the  hand,  and  especially  the  palm,  is  singu- 
larly free  from  surface  veins.  Indeed,  the  great  bulk  of  the  blood  from  the  hand  is 
returned  by  the  superficial  veins  on  the  dorsum  of  the  fingers  and  hand"  (Treves). 

The  annular  ligaments  at  the  wrist  are  of  importance  in  their  relation  to  the 
tendons  and  their  sheaths.  The  tendon-sheaths  (Fig.  591)  which  pass  through  the 
six  compartments  in  or  under  the  posterior  ligament  behave  as  follows.  1.  That 
for  the  short  extensors  and  the  extensor  of  the  metacarpal  bone  of  the  thumb  runs 
from  the  joint  between  the  first  metacarpal  and  the  trapezium  to  a  point  almost  an 
inch  above  the  styloid  process  of  the  radius.      2.   That  for  the  long  and  short  radial 

extensors  of  the  carpus  runs 
Fig.  591.  from  the  insertions  of  those 

muscles  to  a  point  a  half  inch 
above  the  ligament.  3.  That 
for  the  extensor  longus  pol- 
licis  runs  from  the  insertion 
to  the  upper  border  of  the 
ligament.  4.  That  for  the 
extensor  indicis  extends  from 
the  upper  border  of  the  met- 
acarpus, and  that  for  the  ex- 
tensor communis  from  the 
middle  of  the  metacarpus, 
both  to  the  upper  border  of 
the  ligament.  5.  That  for 
the  extensor  minimi  digiti 
runs  from  the  middle  of  the 
metacarpus  ;  and  6,  that  for 
the  ulnar  extensor  of  the  car- 
pus from  the  insertion,  both 
to  the  upper  border  of  the 
ligament. 

Infective  disease  of  the 
dorsum  of  the  wrist  and  hand 
is  rare  as  compared  with  the 
palmar  surface.  The  dense 
connective-tissue  fibres  of  the 
palm  run  vertically  down- 
ward to  the  palmar  fascia 
and  tendon-sheaths,  and  thus 
convey  infection  directly  to 
the  deeper  parts.  This  layer 
is  often  described  as  the  su- 
perficial palmar  fascia.  The 
subcutaneous  connective-tis- 
sue fibres  on  the  dorsum  run 
horizontally,  and  infective  in- 
flammation is  therefore  more 
likely  to  remain  superficial 
(Warren).  If,  however,  it 
does  penetrate  and  gains 
access  to  the  tendon-sheaths,  the  natural  anatomical  limitations  are  those  indicated 
above. 

Teno-synovitis  from  strain,  from  gout,  or  from  rheumatism  is  especially  frequent 
in  these  sheaths,  on  account  of  their  exposure  to  wet  and  cold,  and  also  because  the 
muscles  connected  with  them  are  relatively  weak  and  are  less  often  used  than  those 
on  the  palmar  surface  of  the  forearm.  They  are  thus  more  liable  to  strain  from 
unaccustomed  exertion. 

Ganglion  of  the  simple  (non-tuberculous)  variety  is  also  frequent  here,  probably 
for  the  same  reasons. 


Dissection  of  d 


ficially  distended  sheaths  of 


PRACTICAL    CONSIDERATIONS  :    WRIST    AND    HAND. 


615 


ursa  surrounding  ten-_ 
don  of  flexor  longus 
pollicis 


I 


-Anterior  annu- 
lar  ligament 


One  of  the  most  common  and  most  serious  of  the  sequelse  of  fracture  of  the 
lower  end  of  the  radius  is  stiffness  of  the  wrist  and  fingers  from  adhesions  of  these 
extensor  tendons  and  their  sheaths  to  the  bone,  to  each  other,  and  to  the  surrounding 
structures. 

It  is  important  to  remember,  as  Treves  has  pointed  out,  that  ' '  the  tendons  do 
not  lie  free  within  the  sac,  but  are  bound  to  it  by  folds  of  synovial  membrane  in 
much  the  same  way  as  the  bowel  is  bound  to  the  abdominal  parietes  by  its  mesen- 
tery (Fig.  492).  These  folds  may  be  ruptured  in  severe  sprains,  when  the  nutrient 
vessels  for  the  tendon,  which  are  contained  in  them,  may  be  torn.  Rupture  is  fol- 
lowed by  effusion  into  the  sac.  These  folds  are  almost  absent  within  the  digital  sheaths, 
the    slight    ligamenta 

longa  and  brevia,  near  I7'0-  592. 

the  insertion  of  the 
tendons,  being  the  sole 
representatives.  Sy- 
novial sacs  are  lined  by 
endothelium,  and  have 
extremely  free  com- 
munication with  the 
lymphatic  vessels  of 
the  part.  Hence  the 
free  absorption  of  in- 
fective matter  from 
such  cavities. ' ' 

The  arrangement 
of  the  synovial  sheaths 
beneath  the  anterior 
annular  ligament  is 
of  great  practical  im- 
portance (Fig.  592). 
There  are  two  sacs, 
one  for  the  tendons  of 
the  superficial  and  the 
deep  flexors  ;  one  for 
the  long  flexor  of  the 
thumb.  They  extend 
upward  to  about  two 
finger-breadths  above 
the  annular  ligament. 
Downward,  that  for 
the  thumb  extends  to 
the  insertion  of  the 
tendon  in  the  terminal 
phalanx  ;  the  divertic- 
ula for  the  index,  mid- 
dle, and  ring  fingers 
end  about  the  mid- 
dle of  the  metacarpal 
bones ;  that  for  the  lit- 
tle finger  accompanies 

the  tendon  of  the  deep  flexor  to  its  insertion  in  the  last  phalanx.  The  synovial 
sheaths  for  the  digital  portions  of  the  flexors  for  the  index,  middle,  and  ring  fingers 
extend  upward  only  to  about  the  necks  of  the  corresponding  metacarpal  bones.  They 
are  thus  separated  by  an  interval  of  from  half  an  inch  to  an  inch  from  the  synovial 
sac,  extending  up  under  the  annular  ligament  to  the  forearm  (Fig.  592). 

It  results  from  this  that  infections  (felons,  wounds,  etc.)  of  the  thumb  or  little 
finger  are  especially  apt  to  extend  upward  above  the  wrist  and  involve  the  forearm. 

-    Compotcnd ganglio7i  (tuberculous  teno-synovitis)  frequently  affects  the  common 
synovial  sac  of  the  flexor  tendons  and  not  infrequently  that  of  the  longus  pollicis. 


Dissection  of  palmar  surface  of  right  hand,  showing  artificially  distended  sheaths 
of  flexor  tendons. 


616  HUMAN   ANATOMY. 

The  two  sacs  occasionally  communicate  with  each  other.  On  account  of  the  density 
of  the  annular  ligament,  the  distention  has  a  central  constriction  and  expansions  in 
the  palm  and  above  the  wrist, — "  hour-glass  shape."  These  tendons  also  are  often 
involved  in  fractures  of  the  lower  end  of  the  radius,  although,  on  account  of  the  fact 
that  the  extensors  are  in  closer  relation  to  that  bone  than  is  the  deep  flexor,  and 
that  the  other  flexors — excepting  the  longus  pollicis — are  still  farther  separated  from 
it,  limitation  of  their  motion  is  neither  so  frequent  nor  so  marked. 

In  the  palm  of  the  hand  the  thenar  and  hypothenar  eminences  are  covered  in 
by  their  fasciae,  which  separate  them  from  the  central  space  of  the  palm  through 
which  the  flexor  tendons  run,  and  over  which  is  spread  the  fan-shaped,  deep  palmar 
fascia,  beginning  at  the  tendon  of  the  palmaris  longus  above,  and  spreading  out  to 
be  divided  below  into  the  slips  for  the  fingers  (Fig.  587).  Transverse  fibres  unite 
and  strengthen  these  slips,  which  send  fibres  also  to  the  sheaths  of  the  flexor  tendons 
and  to  the  skin. 

It  may  be  noted  here  that  progressive  muscular  atrophy  usually  begins  in  the 
hand  muscles,  affecting  first  those  of  the  thenar,  then  those  of  the  hypothenar  emi- 
nence, and  next  the  interossei.  When  the  latter  are  greatly  wasted  the  hand  assumes 
the  appearance  of  a  bird's  claw, — the  main  en  griffe  (Duchenne). 

Dupuytren'  s  contraction  affects  chiefly  the  digital  prolongations  of  the  palmar 
fascia,  although  it  extends  secondarily  to  the  bundles  of  fibres  uniting  the  skin  and  the 
aponeurosis.  It  begins  usually  as  a  dense  thickening  of  the  fascia  near  the  line  of 
the  metacarpo-phalangeal  articulation.  It  extends  in  both  directions,  the  concomitant 
shortening  slowly  drawing  down  first  the  distal  and  then  the  intermediate  phalanx. 
The  skin  becomes  closely  adherent  to  the  contracted  fascia.  The  condition  is  seen 
oftenest  in  hands  subjected  to  frequent  slight  traumatism,  as  in  laborers,  or  in  those 
of  gouty  or  rheumatic  persons  past  middle  age. 

Beneath  the  flexor  tendons,  and  above  the  interossei,  the  metacarpal  bones,  and 
the  radial  arch,  lies  another  layer  of  fascia  (interosseous)  which  resists  but  feebly 
the  passage  of  pus  towards  the  dorsum  of  the  hand.  It  is  connected  with  the  thenar 
and  hypothenar  fasciae. 

Several  varieties  of  palmar  abscess  have  been  described  (Tillaux)  in  accord- 
ance with  the  original  site  of  the  infection,  the  spread  of  which  will  be  determined  by 
the  above-mentioned  anatomical  considerations,  (a)  Infection  just  beneath  the 
thick  epidermis  causes  a  superficial  pustule  or  abscess  (subepidermic)  which,  if 
promptly  and  freely  opened,  gives  rise  to  no  difficulty.  (6)  Infection  beneath  the 
skin  (subdermic)  is  attended  by  more  pain,  and,  if  neglected,  may  penetrate  the 
aponeurosis  ;  but  it  is  separated  by  that  structure  from  the  synovial  sheaths  and 
cavities  ;  it  may  be  widely  opened  with  no  reference  to  the  latter  or  to  vessels  ;  it  is 
accompanied  by  little  or  no  swelling  on  the  dorsum  ;  it  has  no  tendency  to  extend  up 
to  the  wrist  ;  movements  of  the  fingers  are  not  very  painful,  (c)  Subdermic  infec- 
tion beginning  in  the  spaces  just  above  the  interdigital  clefts  (i.e.,  between  the 
digital  slips  of  the  palmar  fascia)  may  extend  by  continuity  of  connective  tissue  very 
rapidly  to  the  dorsum  of  the  hand,  which  may  then  appear  to  be  the  chief  seat  of  the 
infection  ;  the  symptoms  are  relatively  mild,  as  the  toxic  exudate  is  not  under  great 
pressure.  (d)  Subaponeurotic  infection  —  true  palmar  abscess  —  is  excessively 
painful,  extends  rapidly  to  the  dorsum  by  perforating  the  interosseous  fascia,  and 
often  to  the  front  of  the  wrist  and  forearm  by  following  up  the  flexor  tendons;  move- 
ments of  the  fingers  are  painful  ;  the  dorso-palmar  diameter  of  the  hand  is  vastly 
increased  ;  the  constitutional  symptoms  are  often  marked. 

Such  abscess  may  also  point  just  above  the  interdigital  webs  or  near  the  ulnar  or 
radial  borders  of  the  hand.  Early  incision  is  imperative  and,  if  made  over  the  line  of 
a  metacarpal  bone  and  limited  in  an  upward  direction  by  a  transverse  line  correspond- 
ing to  that  of  the  web  of  the  fully  extended  thumb  (to  avoid  the  digital  vessels  and 
palmar  arches),  may  be  made  freely.  Above  the  wrist  the  region  of  safety  is  just  to 
the  ulnar  side  of  the  palmaris  longus. 

On  the  fingers  the  skin  resembles  in  its  characteristics  that  of  the  hand.  On  the 
palmar  surface  of  the  first  and  second  phalanges  the  skin  and  the  subcutaneous  fat  are 
connected  with  the  dense  fibrous  sheath  of  the  flexor  tendons  by  vertical  connective- 
tissue  fibres,  and  at  the  level  of  the  joints — where  the  sheaths  are  lax  and  thinner — 


PRACTICAL    CONSIDERATIONS  :    WRIST    AND    HAND. 


617 


Fig 


Head  of 
metacarpal  t 


Dissection  of  metacarpophalangeal  dislocation  of  thumb. 


by  vessels  which  penetrate  the  sheath  to  supply  the  tendons.  Over  the  last  phalanx 
the  fibro-fatty  subcutaneous  layer — the  ' '  pulp' '  of  the  finger — lies  directly  upon  the 
periosteum. 

Infection  of  the  dorsum  of  a  finger  often  originates  near  or  about  the  root  of  a  nail 
(onychia)  and  may  involve  the  matrix  of  the  latter.  It  is  not  under  much  pressure, 
and  is  therefore  not  usually 
serious,  although  through  the 
veins  and  lymphatics  it  may 
exceptionally  extend  rapidly 
up  the  arm. 

Infection  of  the  palmar 
surface  of  a  finger  (panaritium, 
paronychia,  whitlow,  felon)  is 
of  two  chief  varieties  :  (a) 
subcutaneous,  in  which  the 
symptoms  are  at  first  limited 
to  the  seat  of  infection  and  are 
superficial,  although,  as  it  is  a 
true  cellulitis,  they  may  ex- 
tend to  the  dorsum  or  towards 
the  palm  ;  and  (b)  thecal,  with 
more  severe  pain,  greater  lim- 
itation of  flexion,  and  more 
rapid  extension  upward. 

If  the  felon  involves  the 
distal  portion  of  the  finger,  the  close  relation  of  the  ' '  pulp' '  and  the  periosteum  of 
the  last  phalanx  makes  necrosis  of  that  bone  frequent,  although  its  upper  part  usually 
escapes  because  (a)  it  is  an  epiphysis  ;  (b)  the  insertion  of  the  tendon  of  the  deep 
flexor  probably  keeps  up  its  blood-supply  (Treves). 

The  absence  of  the  tendon-sheath  over  the  body  and  tip  of  the  last  phalanx  pre- 
vents the  conversion  of  the  subcutaneous  into  the  thecal  variety,  unless  the  infection 
extends  upward  as  far  as  the  base  of  the  phalanx. 

Elsewhere  the  thecal  variety  often  results  from  extension  from  a  subcutaneous 
focus  by  the  vertical  connective-tissue  fibres  and  the  vessels  already  mentioned.  The 
interphalangeal  joints  are  often  affected  because  it   is  opposite  them   that  («)  the 

tendon-sheaths    are    thinnest    and 
Fig.  594.  (b)  the  vessels  enter.      In  infection 

of  the  tendon-sheaths  of  the  index, 
middle,  and  ring  fingers  the  upward 
extension  is  arrested,  at  least  for 
a  time,  about  opposite  the  necks 
of  the  metacarpal  bones.  If  the 
thumb  or  little  finger  is  involved, 
the  infection  is  likely  to  spread  to 
a  higher  level  (page  615). 

The  so-called  ' '  subcuticular' ' 
felon  is  a  superficial  pustule,  while 
the  ' '  subperiosteal' '  felon  may 
either  result  from  extension  of  the 
foregoing  varieties  or  may  be  origi- 
nally an  infective  osteo-periostitis 
or  osteo-myelitis. 

In  relation  to  amputation  of 
the  finger  it  may  be  noted  that  the 
insertion  of  the  flexor  sublimis  tendon  into  the  sides  of'the  second  phalanx  renders 
amputation  at  the  metacarpophalangeal  joint  often  more  satisfactory  in  its  results 
than  one  done  through  the  first  phalanx  or  first  interphalangeal  joint. 

Dislocation  of  _  the  first  phalanx  of  the  thumb  upon  the  "dorsum  of  its  metacarpal 
bone  requires  special  mention  on  account  of  the  difficulty  of  reduction.      It  has  been 


Dissection  showing  position  of  bones  in  dislocation  of  thumb. 


61S  HUMAN    ANATOMY. 

attributed  (a)  to  the  gripping  of  the  neck  of  the  metacarpal  bone  between  the 
flexor  brevis  pollicis  and  the  oblique  portion  of  the  adductor  pollicis  (these  often 
being  considered  as  the  two  heads  of  the  flexor  brevis  pollicis)  ;  (b)  to  a  similar 
entanglement  of  the  head  and  neck  in  the  slit  in  the  capsule  ;  (c)  to  the  winding  of 
the  tendon  of  the  flexor  longus  pollicis  around  the  neck  of  the  bone  ;  and  (d)  to 
the  interposition  of  the  gleno-sesamoid  plate.  Of  these  theories  the  last  two  seem 
to  offer  the  most  satisfactory  explanation  of  the  difficulties  met  with  in  attempts  at 
replacement. 

The  Surface  Landmarks  of  the  Upper  Extremity. — The  axilla  (page  574) 
is  very  distinctly  bounded  anteriorly  by  the  lower  border  of  the  pectoralis  major,  which 
runs  in  the  line  of  the  fifth  rib  from  the  sixth  costal  cartilage  to  the  external  bicipital 
ridge  ;  posteriorly  by  the  lower  edge  of  the  latissiums  dorsi  and  teres  major,  extend- 
ing to  the  bicipital  groove.  The  shape  of  the  axillary  fossa  varies  with  the  position 
of  the  arm,  becoming  deeper  when  the  arm  is  raised  at  a  right  angle  to  the  trunk  or 
when  the  great  pectoral  and  latissimus  are  contracted.  With  the  arm  still  farther 
elevated,  the  depth  of  the  space  decreases  as  traction  on  those  muscles  approximates 
the  axillary  borders  and  the  humeral  head  enters  and  partly  obliterates  the  cavity. 
With  the  arm  close  to  the  thorax,  the  third  rib  may  be  reached  by  the  exploring 
finger.  The  concavity  of  the  space  is  lessened  or  effaced  by  glandular  tumors,  effu- 
sions of  blood,  or  collections  of  pus  (page  582).  In  opening  an  axillary  abscess  it 
should  be  remembered  that  the  inner  or  thoracic  wall  is  the  direction  of  safety  so  far 
as  the  great  vessels  are  concerned. 

In  the  region  of  the  shoulder  the  rounded  surface  is  produced  by  the  thick 
deltoid  muscle  spread  over  the  greater  tuberosity  of  the  humerus.  It  is  fuller  anteri- 
orly than  posteriorly,  partly  on  account  of  the  presence  of  the  lesser  tuberosity  in 
the  former  position,  but  chiefly  because  the  hinder  portion  of  the  muscle  is  thinner 
than  the  fore  part  and  because  of  its  close  attachment  to  the  infraspinatus  fascia  and 
muscle.  The  greatest  width  of  the  shoulders  does  not  correspond  to  the  points  at 
which  the  deltoid  muscles  overlap  the  head  of  the  humerus,  but  is  at  the  level  of  the 
lower  border  of  the  anterior  axillary  fold, — i.e.,  on  the  level  of  the  point  at  which 
the  various  bundles  of  deltoid  fibres  are  gathered  together  to  pass  to  their  insertion 
(Thomson).  The  bony  points  in  this  region  have  been  described  (pages  270,  279, 
280).  The  anterior  border  of  the  deltoid  presents  a  rounded  eminence  bounded 
internally  above  by  the  infraclavicular  fossa  {vide  infra)  and  below  by  the  closely 
applied  outer  margin  of  the  pectoralis  major.  In  the  shallow  groove  between  these 
two  muscles  the  cephalic  vein  and  a  branch  of  the  acromio-thoracic  artery  are  to  be 
found.  Just  external  to  the  groove  under  the  inner  fibres  of  the  deltoid  is  the  cora- 
coid  process  (page  255).  The  infraclavicular  fossa  is  the  triangular  interval  bounded 
by  the  outer  fibres  of  the  pectoralis  major  internally,  the  inner  fibres  of  the  deltoid 
externally,  and  the  clavicle  above.  The  surface  depression  known  by  this  name  may 
be  much  larger  than  this  intermuscular  interval,  and  may  almost  correspond  in  extent 
to  the  roof  of  the  superficial  infraclavicular  triangle  (page  581).  It  is  not  very  marked 
in  muscular  subjects.  It  is  effaced — owing  to  tension  of  fascia  and  muscles — in  sub- 
coracoid  luxation  of  the  humerus,  or  in  fracture  of  the  clavicle  with  marked  displace- 
ment of  the  fragments.  It  may  be  converted  into  a  rounded  elevation  by  glandular 
growths  extending  upward  from  the  axilla,  or  by  the  head  of  the  humerus  in  intra- 
coracoid  (infraclavicular)  luxation.  At  the  bottom  of  this  fossa,  just  within  the  cora- 
coid  process, — i.e.,  not  far  from  the  middle  of  the  clavicle, — the  first  portion  of  the 
axillary  artery  may  be  compressed  against  the  second  rib  by  pressure  directed  back- 
ward and  a  little  inward,  the  patient  being  supine. 

The  posterior  border  of  the  deltoid  above  is  tendinous,  is  closely  attached  to 
the  infraspinatus  muscle  beneath  it,  and  is  scarcely  discernible.  Below  it  is  thicker 
and  presents  a  well-marked  rounded  eminence  which  inclines  from  behind  forward  to 
meet  the  anterior  border  at  the  middle  of  the  outer  side  of  the  arm,  where  a  distinct 
depression  indicates  the  insertion  of  the  deltoid  (Fig.  595).  This  depression  is  a  valu- 
able practical  landmark  for  the  reasons  that  :  ( 1 )  It  corresponds  to  the  middle  of  the 
'  shaft  of  the  humerus,  where  the  two  curves  of  the  bone  unite  and  where  the  cylin- 
drical joins  the  prismatic  part  of  the  shaft,  which  is  there  smallest,  hardest,  and  least 
elastic  (page  272),  and  hence  is  most  frequently  broken.     (  2)  It  indicates  the  region 


PRACTICAL    CONSIDERATIONS  :    SURFACE    LANDMARKS.      619 

of  insertion  of  the  deltoid  and  coraco-brachialis,  and  embraces  part  of  the  origin 
of  the  brachialis  amicus  and  internal  head  of  the  triceps,  and  is  therefore,  and  on 
account  of  the  intimate  attachment  of  the  periosteum  (page  272),  a  not  uncommon 
seat  of  exostoses.  (3)  The  region  is — by  reason  of  the  close  relation  of  these  mus- 
cles to  the  bone — a  frequent  seat  of  ununited  fracture  (page  273).  (4)  The  nutrient 
artery  enters  the  bone  and  the  superior  profunda  artery  and  musculo-spiral  nerve 
wind  around  its  posterior  surface  at  that  level,  at  which  also  the  lesser  internal  cuta- 
neous nerve  and  the  basilic  vein  penetrate  the  deep  fascia,  the  median  nerve  crosses 
the  brachial  artery,  and  the  ulnar  nerve  leaves  it. 

On  the  outer  surface  of  the  arm  below  the  insertion  of  the  deltoid  can  be  seen 
the  shallow  furrow  (Fig.  596)  between  the  outer  head  of  the  triceps  and  the  brachio- 
radialis  which  indicates  the  position  of  the  external  intermuscular  septum  and  of  the 
external  supracondyloid  ridge  (page  273)  . 

On  the  posterior  surface  of  the  arm  the  three  heads  of  the  triceps  can  be  seen 
when  the  forearm  is  strongly  extended  (Fig.  596).  The  outer  head  makes  a  distinct 
prominence  just  beneath  the  posterior  border  of  the  deltoid  ;  the  inner  head 
is  less  distinct  ;  the  long  head  comes  into  view  where  it  descends  from  between  the 
two  teres  muscles,  and  lower  in  the  arm — where  it  has  become  tendinous — is  indi- 
cated by  a  broad,  shallow  depression  ending  at  the  olecranon.  The  long  and  outer 
heads  cover  the  musculo-spiral  nerve  and  superior  profunda  artery  from  just  beneath 
the  posterior  axillary  fold  to  the  point  where  they  perforate  the  external  septum. 

On  the  anterior  and  inner  surfaces  of  the  arm  the  rounded  swell  of  the  biceps 
and  the  external  and  internal  bicipital  furrows  are  the  most  important  landmarks. 


Fig.  595. 


Anteromedian  surface  of  right  arm,  showing  modelling  on  living  subject. 

The  elevation  of  the  biceps  shades  off  superiorly  into  the  narrower  and  less  distinct 
prominence  of  the  coraco-brachialis  where  it  comes  into  view  below  and  beneath  the 
anterior  axillary  fold.  Inferiorly  it  narrows  externally  and  merges  into  the  biceps 
tendon,  easily  seen  passing  into  the  forearm  in  the  deep  interval  between  the  rounded 
supinator  and  extensor  mass  on  the  radial  side  and  the  pronator  and  flexor  mass  on 
the  ulnar  side  (Fig.  595).  Internally  the  broader  flat  slip  of  bicipital  fascia — the 
inner  tendon — may  be  seen  with  its  sharp  upper  edge  when  the  forearm  is  semi- 
flexed and  the  biceps  is  in  strong  action.  The  outer  bicipital  furrow  indicates  the  posi- 
tion of  the  subcutaneous  cephalic  vein.  The  inner  and  deeper  furrow  marks  the 
line  of  the  basilic  vein  (subcutaneous  in  its  lower  half,  then  subfascial),  of  the  median 
nerve  and  the  brachial  vessels,  and  in  its  upper  half  of  the  ulnar  nerve.  To  the  outer 
side  of  the  outer  furrow  from  above  downward  lie  the  deltoid,  the  outer  head  of  the 
triceps,  the  outer  portion  of  the  brachialis  anticus  and  the  brachio-radialis,  and  the 
common  extensor  mass  (Fig.  596).  To  the  inner  side  of  the  inner  furrow  are  seen  the 
coraco-brachialis,  the  long  head  and  then  the  inner  head  of  the  triceps,  the  brachialis 
anticus,  and  the  pronato-flexor  mass. 

At  the  bend  of  the  elbow  anteriorly  the  subcutaneous  veins  are  often  visible. 
Their  arrangement  is  sufficiently  described  and  figured  elsewhere  (page  892, 
Fig.  764).  The  bicipital  fascia  passes  between  the  median  basilic  vein  and  brachial 
artery,  and,  by  springing  from  the  inner  edge  of  the  biceps  tendon,  makes  that  edge 


620 


HUMAN   ANATOMY. 


less  distinct  to  both  sight  and  touch  than  the  outer  edge.  Just  within  the  inner 
edge  is  the  brachial  artery  and  farther  in  the  median  nerve. 

The  fold  of  the  elbow  is  a  transverse  crease  in  the  skin,  seen  in  flexion,  convex 
downward,  and  running  from  the  tip  of  one  condyle  to  the  tip  of  the  other.  It  lies 
above  the  line  of  the  elbow-joint.  In  dislocation  of  the  radius  and  ulna  backward 
the  lower  end  of  the  humerus  is  below  this  crease  ;  in  fracture  of  the  humerus  above 
the  condyles  the  lower  end  of  the  upper  fragment  is  either  on  a  line  with  or  above 
the  crease.  This  relation  will  not  be  demonstrable  in  the  presence  of  much  swelling, 
as  this  fold  is  then  obliterated. 

On  the  front  of  the  forearm,  below  the  apex  of  the  triangular  space  resulting  from 
the  convergence  of  the  two  muscular  masses  descending  from  the  condylar  regions, 
there  are  no  salient  surface  landmarks,  and  none  of  great  practical  importance  until 
the  wrist  is  reached.  Many  of  those  of  that  region  and  of  the  hand  have  been  de- 
scribed (pages  228,  229,  230,  320).  It  should,  however,  be  noted  that,  instead  of 
being  flattened  from  before  backward  and  widest  from  side  to  side  as  when  in  the 
supine  position,  the  forearm  when  the  hand  is  pronated  becomes  rounded  and  its 
antero-posterior  slightly  exceeds  its  lateral  thickness  (Thomson).  This  is  due  to 
the  fact  that  the  tendons  of  the  supinator  and  extensor  masses  are  held  in  grooves 
in  the  lower  end  of  the  radius  by  the  posterior  annular  ligament,  and  are  thus  car- 
ried towards  the  ulna  when  the  radius  moves  in  that  direction. 


Outer  head  of  triceps 


Fig.  596. 

Braehialis  anticus 

External  bicipital  furrow 
Brachio-radialis 

Common  extensor 


Long  head         Triceps 

of  triceps  1  olecranon  rjina  uinar  styloid  proc 

Internal  condyle 

Posterior  surface  of  arm  shown  in  preceding  figure. 


Of  the  two  transverse  furrows  on  the  flexor  surface  of  the  wrist  the  lower  is  the 
more  marked.  It  is  almost  three-quarters  of  an  inch  below  the  summit  of  the  upward 
curve  of  the  wrist-joint,  is  on  the  line  of  the  intercarpal  joint  and  of  the  upper  border 
of  the  anterior  annular  ligament,  and  is  about  a  half-inch  above  the  carpo-metacarpal 
joint.  At  the  wrist  the  palmaris  tendon — when  present — is  made  prominent  by 
extending  the  digits,  slightly  flexing  the  wrist,  and  closely  approximating  the  thenar 
and  hypothenar  eminences.  To  its  radial  side  from  within  outward  lie  the  median 
nerve,  the  tendon  of  the  flexor  carpi  radialis,  and  the  radial  artery.  To  its  ulnar 
side  lie  first  the  rounded  elevation  made  by  the  flexor  sublimis  tendons,  then  the  ulnar 
artery,  and  then  the  flexor  carpi  ulnaris  tendon,  made  easily  palpable,  although  not 
very  prominent,  by  strong  flexion  of  the  wrist  and  little  finger. 

On  the  postero-lateral  aspect  of  the  forearm  may  be  seen  : 

1.  The  elevation  of  the  anconeus,  triangular  in  shape,  to  the  radial  side  of  the 
posterior  subcutaneous  surface  of  the  olecranon  and  separated  from  the  common 
extensor  mass  by  a  well-defined  depression.  This  muscle  and  the  expansion  of  the 
triceps  tendon  that  covers  it  are  of  great  value  in  the  movement  of  extension  of  the 
forearm  after  excision  of  the  elbow. 

2.  The  curved  border  of  the  ulna  (subcutaneous  in  supination),  at  the  bottom 
of  the  ulna?'  furrow,  between  the  flexor  carpi  ulnaris  and  the  common  extensor 
group,  is  easily  accessible  for  examination  through  its  whole  length  (page  289). 

3.  The  very  important  depression  just  below  the  external  condyle  and  exter- 
nal to  the  olecranon  has  been  described  (page  296). 


PRACTICAL   CONSIDERATIONS  :    SURFACE   LANDMARKS.      621 

4.  The  oblique  elevation  beginning  at  the  lower  third  of  the  forearm  in  the 
interval  left  by  the  divergence  of  the  supinator  and  the  common  extensor  muscles, 
and  running  downward  and  outward,  to  be  lost  on  the  posterior  surface  of  the 
thumb,  represents  the  extensors  of  the  thumb  crossing  over  the  tendons  of  the 
extensores  carpi  radialis  longior  and  brevior  to  their  points  of  insertion  (Fig.  582). 

5.  The  bony  points  to  be  seen  and  felt  at  the  elbow  and  wrist  have  been  de- 
scribed in  their  practical  relations  in  connection  with  the  bones  and  joints  (pages 
287,  296,  308,  320,  330).  The  tendon  most  easily  identified  on  the  dorsum  of  the 
wrist  is  that  of  the  extensor  longus  pollicis  when  the  thumb  is  strongly  extended  and 
abducted.  It  is  the  posterior  or  inner  boundary  of  the  hollow  at  the  base  of  the 
thumb  (vide  infra),  and  its  groove  in  the  lower  end  of  the  radius  is  about  the  middle 
of  the  posterior  surface  and  just  to  the  ulnar  side  of  the  prominent  middle  thecal 
tubercle, — a  useful  landmark  (page  296).  The  tendon,  just  before  it  reaches  the 
radius,  corresponds  approximately  to  the  scapho-semilunar  joint. 

The  surface  markings  of  the  palm  of  the  hand  are  often  valuable  landmarks. 

The  most  important  are  :  (1)  The  triangle  called  the  "  hollow  of  the  hand,"  the 
"cup  of  the  palm,"  etc.,  the  base  of  which  corresponds  to  the  three  elevations  oppo- 
site the  interdigital  clefts, — formed  by  protrusion  of  fat  between  the  flexor  tendons 
and  the  digital  slips  of  the  palmar  fascia  and  by  the  distal  extremities  of  the  lumbri- 
cales, — and  seen  best  when  the  metacarpo -phalangeal  joints  are  extended  and  the 
interphalangeal  joints  are  flexed.  The  sides  of  the  triangle  are  formed  by  the  thenar 
and  hypothenar  eminences.  Over  this  palmar  hollow  the  intimate  connection  of  the 
skin  and  fascia  is  of  practical  importance  (page  613).  (2)  The  chief  cutaneous 
creases  (Fig.  597)  are  four  in  number  :  («)  from  just  above  the  apex  of  the  palmar 
triangle  to  the  radial  side  of  the  hand  above  the  base  of  the  index-finger  ;  (b)  from 
the  lower  end  of  a  to  a  point  a  little  above  the  middle  of  the  ulnar  border  of  the  palm, 
which  it  does  not  quite  reach  ;  (c)  from  about  the  junction  of  the  lower  fourth 
with  the  upper  three-fourths  of  the  ulnar  border  of  the  palm  to  a  point  a  little  above 
the  cleft  between  the  index  and  middle  fingers  ;  (d )  from  b  to  c,  often  extending 
upward  towards  the  wrist  and  downward  towards  the  base  of  the  middle  finger. 
a  and  d  are  longitudinal,  the  former  being  caused  by  adduction  of  the  first  meta- 
carpal, the  latter  by  adduction  of  the  fifth  metacarpal  bone,  both  movements  being 
towards  the  mid-line  of  the  hand  ;  b  and  c  are  transverse,  and  are  produced  chiefly 
by  flexion  (b)  of  the  first  and  second  (c)  of  the  three  inner  metacarpophalangeal 
joints. 

a  represents  the  inner  border  of  the  thenar  eminence  and  therefore,  approxi- 
mately, of  the  outer  group  of  the  short  muscles  of  the  thumb  and  the  inner  margin  of 
the  fascia  intervening  between  them  and  the  palmar  space  through  which  run  the 
flexor  tendons.  It  intersects  the  deep  palmar  arch  at  about  the  highest  point  where 
it  crosses  the  metacarpal  bone  of  the  middle  finger. 

b,  at  the  centre  of  the  palm,  where  it  is  intersected  by  d,  crosses  the  same 
metacarpal  bone  a  line  or  two  below, — i.e.,  nearer  the  fingers  than  the  superficial 
palmar  arch,  which  runs  about  on  a  curved  line  from  the  lower  border  of  the  thumb, 
when  it  is  at  right  angles  to  the  hand,  to  the  pisiform  bone.  The  deep  palmar  arch 
is  from  a  quarter  to  a  half  an  inch  nearer  the  wrist. 

c  represents  the  upper  limits  of  the  synovial  sheaths  of  the  flexor  tendons  of 
the  index,  middle,  and  ring  fingers,  is  a  little  above  the  division  of  the  palmar  fascia 
into  the  digital  slips  and  the  bifurcation  of  the  digital  arteries,  crosses  the  necks  of 
the  three  inner  metacarpal  bones,  and  is  as  much  above  the  corresponding  meta- 
carpo-phalangeal  joints  as  they  are  above  the  webs  of  the  fingers. 

d,  at  its  upper  portion,  irregularly  outlines  the  outer  border  of  the  hypoth- 
enar eminence, — i.e.,  of  the  short  muscles  of  the  little  finger  and  of  the  fascia  sepa- 
rating them  from  the  central  space  of  the  palm, — but  it  is  the  most  irregular  and 
unimportant  of  these  creases.  The  transverse  folds  on  the  palmar  surfaces  of  the 
fingers  correspond,  the  highest  to  the  web  of  the  fingers, — i.e.,  from  one-half  to  three- 
quarters  of  an  inch  below  the  metacarpophalangeal  joint, — the  middle  to  the  proxi- 
mal interphalangeal  joint,  and  the  lowest  to  a  line  a  little  above  the  distal  interpha- 
langeal joint.  On  the  thumb  the  line  of  the  radial  side  of  the  index-finger,  if 
continued  upward,  almost  coincides  with  the  higher  of  the  creases,  which  crosses  the 


622 


HUMAN    ANATOMY. 


metacarpo-phalangeal  joint  obliquely.  The  lower  crease  corresponds  to  the  inter- 
phalangeal  joint.  The  papillary  ridges  of  the  skin  covering  the  terminal  phalanges 
assume  varied  curves  and  form  patterns, — immutable  and  characteristic  in  the  indi- 
vidual,— impressions  of  which  have  been  used  of  late  years  for  purposes  of  identifica- 
tion of  criminals. 

On  the  dorsum  of  the  hand  the  hollow  at  the  base  of  the  thumb  (the  so-called 
"snuff-box")   is  bounded  externally  (radially)  by  the  tendon  of  the  extensor  of  the 

Fig.  597. 


Surface  markings  of  right  pain 


metacarpal  bone  of  the  thumb  and  the  short  extensor,  and  internally  by  the  tendon  of 
the  long  extensor  (Fig.  582).  The  radial  artery,  a  large  vein, — cephalic  vein  of 
the  thumb  (Treves), — and  the  inner  division  of  the  radial  nerve  cross  this  space. 
Beneath  it  are  the  scaphoid  and  trapezium  and  the  articulation  between  the  latter 
and  the  first  metacarpal  bone. 

The  abductor  indicis  muscle  makes  a  distinct  fusiform  prominence  when  the 
thumb  is  adducted.  The  tendons  of  the  common  extensor  and  of  the  extensor  of  the 
little  finger  and  the  slip  connecting  them  may  be  seen. 

It  should  be  remembered  that  the  "knuckles"  are  at  each  joint,  the  distal 
extremities  of  the  proximal  bones  entering  into  the  articulation. 


THE   MUSCLES   OF   THE   LOWER   LIMB.  623 


THE  MUSCLES  OF  THE  LOWER   LIMB. 

In  describing  the  muscles  of  the  lower  limb  a  classification  similar  to  that  which 
was  employed  for  the  upper  limb  muscles  will  be  followed.  Owing,  however,  to  the 
firm  articulation  of  the  innominate  bones  to  the  sacrum,  the  muscles  extending 
between  the  axial  skeleton  and  the  pelvic  girdle  are  greatly  reduced,  and  those 
(such  as  the  psoas)  which  might  be  included  in  this  group  are  continued  to  the 
femur,  and  for  present  purposes  are  more  conveniently  grouped  with  the  muscles 
extending  from  the  girdle  to  the  femur. 

There  is  also,  in  the  lower  limb,  a  greater  number  of  muscles  passing  over  two 
joints  ;  indeed,  many  of  the  muscles  which  are  inserted  into  the  upper  portions  of 
the  leg  bones  take  their  origin  from  the  pelvic  girdle.  Most  of  these  seem  to  be, 
primarily,  members  of  the  femoral  group  of  muscles  and  will  be  so  classified  in  the 
succeeding  pages,  but  one  (the  gracilis),  at  least,  appears  to  belong  to  the  group 
extending  from  the  girdle  to  the  femur. 

THE   MUSCLES   EXTENDING   FROM   THE   PELVIC   GIRDLE 
TO  THE  FEMUR. 


I. 

Psoas  magnus. 

6.    Adductor  brevis. 

2. 

Iliacus. 

7.    Adductor  magnus. 

3- 

Pectineus. 

8.    Ouadratus  femoris. 

4- 

Gracilis. 

9.    Obturator  externus. 

5- 

Adductor  longus. 

10.    Obturator  internus. 

11. 

Gemelli. 

1.    Psoas  Magnus  (Fig.   598). 

Attachments. — This  muscle  (m.  psoas  major)  arises  from  the  sides  of  the 
bodies  of  the  twelfth  thoracic  and  all  the  lumbar  vertebra;  and  from  the  transverse 
processes  of  the  lumbar  vertebrae.  Its  fibres  pass  directly  downward  and  slightly 
forward  over  the  superior  ramus  of  the  pubis  and  are  inserted  by  a  tendon,  in  com- 
mon with  the  iliacus,  into  the  lesser  trochanter  of  the  femur. 

Nerve-Supply. — By  branches  from  the  lumbar  plexus  from  the  second,  third, 
and  fourth  lumbar  nerves. 

Action. — To  bend  the  spinal  column  laterally  and  to  flex  the  body  and  pelvis 
upon  the  femur.      Acting  from  above,  it  flexes  the  thigh  and  rotates  it  kwa#d.  inJSt 

Relations. — The  psoas  magnus  lies  along  the  side  of  the  lumbar  vertebrae, 
resting  upon  their  transverse  processes  and  the  medial  portion  of  the  quadratus 
lumborum.  Extending  as  high  as  the  last  thoracic  vertebra,  it  passes  beneath  the 
internal  arcuate  ligament,  or  medial  lumbo-costal  arch,  of  the  diaphragm,  and  below 
it  passes  beneath  Poupart's  ligament  to  reach  the  thigh.  In  its  abdominal  portion 
it  is  in  relation  ventrally  with  the  peritoneum,  on  the  right  side  with  the  ascending 
colon  and  duodenum,  and  on  the  left  side  with  the  descending  colon  and  pancreas. 
The  inner  border  of  the  kidney  overlaps  the  lateral  portion  of  the  muscle,  and  the 
ureter  and  spermatic  (or  ovarian)  arteries  descend  obliquely  along  it.  The  inferior 
vena  cava  lies  in  front  of  the  right  muscle.  The  nerves  formed  by  the  lumbar 
plexus  perforate  the  muscle,  and  the  genito-crural  nerve  passes  down  on  its  anterior 
surface.  In  the  pelvis  the  external  iliac  vessels  lie  along  its  medial  border,  and  it  is 
crossed,  just  before  it  passes  beneath  Poupart's  ligament,  by  the  vas  deferens.  In 
the  thigh  it  forms  a  portion  of  the  floor  of  the  femoral  or  Scarpa's  triangle,  and  lies 
between  the  iliacus  and  pectineus  muscles,  behind  the  femoral  vessels.  As  the  ten- 
don which  is  common  to  it  and  the  iliacus  passes  over  the  hip-joint  it  rests  upon  a 
rather  large  bursa  (bursa  iliopectinea) ;  just  above  the  insertion  a  second  bursa  (bursa 
iliaca  subtendinea)  intervenes  between  the  tendon  and  the  femur. 


624 


HUMAN    ANATOMY. 


External 
arcuate  ligament 


Internal 
arcuate  ligament 


The  psoas  magnus  appears  to  be  formed  by  the  union  of  a  hyposkeletal  trunk  muscle  with 
a  femoral  muscle,  the  remaining  portions  of  which  are  represented  by  the  iliacus  and  pectineus. 
It  is  interesting  to  note  in  this  connection  that  in  those  mammalia  in  which  the  quadratus  lum- 
borum  is  well  developed  the  psoas  magnus  is  correspondingly  weak,  and  vice  versa. 

The  psoas  parvus  or 
Fig    sqS  minor  ( Fig.  598 )  is  a  long, 

flat  muscle  which  lies  upon 
the  ventral  surface  of  the 
psoas  magnus,  represent- 
ing a  separated  portion  of 
it,  and  is  present  in  some- 
thing over  50  per  cent,  of 
cases.  It  arises  from  the 
bodies  of  the  last  thoracic 
and  first  lumbar  vertebrae 
and  is  inserted  into  about 
the  middle  of  the  ilio-pec- 
tineal  line  (linea  termina- 
lis)  of  the  pelvis. 

2.  Iliacus  (Fig.  598). 

Attachments. — 

The  iliacus  arises  from 
about  the  upper  half  of 
the  anterior  surface  of 
the  ilium.  Its  fibres 
converge  downward  to 
form  a  common  tendon 
with  the  psoas  major, 
which  is  inserted  into 
the  lesser  trochanter  of 
the  femur. 

Nerve-Supply. — 
By  the  anterior  crural 
nerve  from  the  second, 
third,  and  fourth  lum- 
bar nerves. 

Action. — To  flex 
the  thigh  and  rotate  it 
slightly  ^»vard  ;  when 
the  thigh  is  fixed,  to 
flex  the  pelvis  and  trunk 
upon  the  femur. 

Relations. —  The 
iliacus  covers  the  pos- 
terior wall  of  the  false 
pelvis,  and  upon  the 
right  side  has  resting 
upon  it  the  caecum  and 
on  the  left  side  the 
sigmoid  colon.  It  is 
crossed  obliquely  by 
the  external  cutaneous  and  the  anterior  crural  nerves ;  its  inner  border  is  covered 
by  the  psoas  magnus.  It  passes  beneath  Poupart's  ligament  external  to  the  psoas 
magnus,  its  relations  in  the  thigh  being  identical  with  those  of  that  muscle. 

Variations. — The  iliacus  and  psoas  magnus  are  not  infrequently  extensively  united,  and 
the  two  muscles,  together  with  the  psoas  parvus,  when  this  is  present,  are  frequently  spoken  of 
as  the  m.  ilio-psoas.  The  fibres  of  the  iliacus  which  arise  from  the  posterior  superior  spine 
of  the  ilium  are  often  separated  from  the  rest  of  the  muscle  to  form  an  iliacus  minor,  which  is 
inserted  into  the  capsule  of  the  hip-joint  or  into  the  anterior  intertrochanteric  line. 

The  Iliac  Fascia. — This  fascia  is  a  strong  sheet  of  connective  tissue  which 
covers  the  entire  ilio-psoas.      Above  it  is  attached  to  the  internal  arcuate  ligament  of 


Deep  dissection  of  posterior  body- 


nd  iliac  fossa  of  right  side. 


THE    MUSCLES    OF   THE    LOWER    LIMB.  625 

the  diaphragm,  and  thence  descends  over  the  anterior  surface  of  the  psoas.  On  reach- 
ing the  level  of  the  crest  of  the  ilium,  it  is  prolonged  outward  along  that  structure, 
where  it  is  in  connection  with  the  lower  edge  of  the  transversalis  fascia.  It  descends 
thence  over  the  anterior  surface  of  the  psoas  and  iliacus,  at  the  inner  border  of  the 
former  muscle  passing  over  into  the  pelvic  fascia.  Below  it  is  attached  in  its  lateral 
two-thirds  to  Poupart's  ligament,  more  medially  it  remains  in  contact  with  the  ilio- 
psoas and  passes  down  into  the  thigh  behind  the  femoral  vessels,  separating  these 
structures  from  the  muscle  and  the  anterior  crural  nerve  and  forming  the  posterior 
wall  of  the  sheath  for  the  femoral  vessel.  It  thus  divides  the  space  beneath  Pou- 
part's ligament  (Fig.  599)  into  a  muscular  compartment  (lacuna  musculorum)  which 
contains  the  ilio-psoas  muscle  and  the  anterior  crural  and  external  cutaneous  nerves, 
and  a  vascular  compartment  (lacuna  vasorum)  which  contains  the  femoral  artery  and 
vein  and  the  crural  branch  of  the  genito-crural  nerve,  its;'mnermost  portion,  between 
the  femoral  vein  and  the  free  edge  of  Gimbernat's  ligament,  transmitting  only  a  few 
loosely  arranged  lymphatic  vessels  and  forming  what  is,,  termed  the  femoral  ring 
(annulus  femoralis). 

This  ring  (Fig.  599),  which  is  covered  over  by  a  portion  of  the  transversalis 
fascia,  known  as  the  septum  crurale  or  femorale,  is  the  upper  end  of  a  space,  occu- 

Fig.  599. 


Anterior  superior  il 


:  fascia  attached  to  Poupart's  ligament 

Aponeurosis  of  external  oblique 
Iliacus  muscle 
Anterior  crural  nerve 


External  abdominal  ring 


Gimbernat's  ligament 


Femoral  ring 
Iliac  fascia  continued  as^ 
posterior  wall  of  femo- 
ral sheath 
Pudic  branch  of  obturator' 

Obturator  membrane 


pied  by  loose  areolar  tissue  and  lymphatic  vessels,  which  extends  a  short  distance 
downward  along  the  inner  side  of  the  femoral  vein,  forming  what  is  termed  the 
femoral  canal.  Owing  to  the  nature  of  its  contents  and  to  its  upper  end  being 
closed  only  by  the  relatively  thin  septum  femorale,  this  canal  may  allow  of  the 
escape  of  a  portion  of  the  intestine  from  the  abdominal  cavity  downward  into  the 
thigh,  producing  a  femoral  hernia. 

Medially  the  portion  of  the  iliac  fascia  which  forms  the  posterior  wall  of  the 
sheath  for  the  femoral  vessels  is  continued  over  the  anterior  surface  of  the  pectineus 
muscle  (Fig.  1496),  this  portion  of  it  being  sometimes  termed  the  pectineal  or  ilio- 
pectineal  fascia.  Above  it  is  attached  to  the  ilio-pectineal  eminence  and  below 
becomes  continuous  with  the  deep  layer  of  the  fascia  lata. 

3.   Pectineus  (Fig.  600). 

Attachments. — The  pectineus  arises  from  the  anterior  surface  of  the  superior 
ramus  and  ilio-pectineal  line  of  the  pubis  and  passes  downward  and  laterally  to  be 
inserted  into  the  pectineal  line  of  the  femur,  a  bursa  intervening  between  it  and 
the  bone. 


626 


HUMAN   ANATOMY. 


Nerve-Supply. — From    the  anterior   crural   nerve  by  the  second  and  third 
lumbar  nerves. 

Action. — To  adduct  and  flex  the  thigh  and  rotate  it  slightly  outward. 

Variations. — The  fibres  which  in- 
nervate the  pectineus  sometimes  pass 
to  it  wholly  or  partly  by  the  obturator 
nerve. 


Fig.  600. 


4.   Gracilis  (Fig.  600). 

Attachments. — The  gra- 
cilis is  a  long  band-like  muscle 
which  arises  from  the  anterior 
surface  of  the  body  and  inferior 
ramus  of  the  pubic  bone.  It  de- 
scends along  the  inner  surface  of 
the  thigh,  passes  behind  the  inner 
condyle  of  the  femur,  and  then, 
bending  slightly  forward,  is  in- 
serted into  the  inner  surface  of 
the  tibia  near  the  tuberosity,  just 
above  the  semitendinosus  and  be- 
hind and  beneath  the  expanded 
tendon  of  the  sartorius. 

Nerve-Supply.  —  By  the 
anterior  division  of  the  obturator 
nerve  from  the  second,  third,  and 
fourth  lumbar  nerves. 

Action. — To  adduct  the  leg 
and  flex  the  thigh.      It  will  also 
assist  in  rotating  the  leg  ^^atd,  PTXl'W' 
especially  if  the  thigh  be  flexed. 

5.  Adductor  Longus  (Fig. 
600). 

Attachments.  —  The  ad- 
ductor longus  arises  from  the  an- 
terior surface  of  the  body  and 
superior  ramus  of  the  pubis  and 
passes  downward  and  laterally  to 
be  inserted  into  about  the  middle 
third  of  the  inner  lip  of  the  linea 
aspera  of  the  femur. 

Nerve-Supply.  —  By  the 
anterior  division  of  the  obturator 
nerve  from  the  second  and  third 
lumbar  nerves. 

Action. — To  adduct,  flex, 
and  outwardly  rotate  the  thigh. 

6.  Adductor  Brevis  (Fig. 
601). 

Attachments. — The  ad- 
ductor brevis  arises  from  the  body 

Muscles  of  right  thigh,  anteromedian  aspect.  and    Jnferior    ramus    0f    the    pubic 

bone,  below  and  partly  external 
to  the  origin  of  the  adductor  longus.  It  passes  laterally  and  obliquely  downward  to 
be  inserted  into  the  upper  third  of  the  medial  lip  of  the  linea  aspera  of  the  femur. 


THE   MUSCLES   OF   THE   LOWER   LIMB. 

Fig.  6oi. 

\ 


627 


-^"f- Dorsum  of  ilii 


Obturator-^- 
interims 
Tuber  ischii 


Origin  of  semimem- 
branosus, semi- 

tendinosns.and 
biceps 


-Gluteus  minimus 
-Greater  trochanter 


Quadratus  femoris,  insertion 
"  Obturator  externus 


Adductor  brevi 

Adductor  magnu 


Perforating  arteries 


-Vastus  externu 


Fourth  perforating  artery 


Femoral  vein 
Femoral  artery 


Intemal  condvle 


Biceps,  short  head 


iceps,  long  head,  cut 


Popliteal  surface  of  femur 


External  condyle 

Deep  dissection  of  posterior  surface  of  right  thigh. 


628 


HUMAN    ANATOMY. 


Nerve-Supply. — By  the  anterior  ramus  of  the  obturator  nerve  from  the  third 
and  fourth  lumbar  nerves. 

Action. — To  adduct,  flex,  and  outwardly  rotate  the  thigh. 

7.    Adductor  Magnus  (Fig.  601). 

Attachments. — The  adductor  magnus  arises  from  the  inferior  rami  of  the 
pubis  and  ischium,  as  far  laterally  as  the  base  of  the  tuber  ischii.  Its  anterior  fibres 
are  directed  laterally  and  downward  to  be  inserted  into  nearly  the  whole  length  of 
the  inner  lip  of  the  linea  aspera  by  a  series  of  tendinous  arches  which  give  passage 
to  the  perforating  branches  of  the  profunda  femoris  artery  on  their  way  to  the  back 
of  the  thigh.  Its  posterior  fibres  converge  downward  to  a  strong  tendon  which  is 
inserted  into  the  adductor  tubercle  on  the  inner  condyle  of  the  femur. 

Nerve-Supply. — By  the  posterior  division  of  the  obturator  nerve  from  the 
third  and  fourth  lumbar  nerves. 

Action.— To  adduct  the  thigh.   CyW  hA&M  •    JL.f^r/,-.-  ^oUi  t- ' 

Relations. — The  adductor  muscles,  together  with  the  gracilis,  occupy  the 
medial  surface  of  the  thigh,  intervening  between  the  extensor  and  flexor  muscles. 
The  adductor  brevis  and  adductor  longus  enter  into  the  formation  of  the  floor  of 
Scarpa's  triangle  (page  639),  and  from  the  apex  of  the  latter  the  femoral  vessels  are 


Sacrum 
Greater  sacro-sciatic  foramen 
Greater  sacro-sciatic  ligament 


Gemellus  superior 

Obturator  intern  us 

Gemellus  inferior 


Gluteus  minii 


Greater  trochanter 

Tendon  of  obturator  externus 


Deep  dissection  of  right  buttock,  showing  muscles  attached  to  greater  trochanter  of  femur. 

continued  downward  upon  the  longus  and  magnus  close  to  their  insertion,  and, 
together  with  the  internal  saphenous  nerve,  are  bridged  over  by  an  aponeurotic 
membrane  which  passes  from  the  longus  and  magnus  to  the  surface  of  the  vastus 
internus.  By  this  membrane  the  space  occupied  by  the  vessels  and  nerve  is  con- 
verted into  a  closed  passage-way  termed  Hunte?'' s  canal  (canalis  addtictorius)  (Fig. 
606),  the  lower  end  of  which  corresponds  to  the  interval  (hiatus  tendineus)  between 
the  tendons  of  the  anterior  and  posterior  portions  of  the  adductor  magnus. 

The  perforating  branches  of  the  deep  femoral  artery  pierce  the  adductor  magnus 
near  its  insertion,  the  first  one  passing  above  and  the  second  below  the  adductor 
brevis,  or  both  perforate  that  muscle  also,  while  the  third  passes  through  the  magnus 
a  little  above  the  hiatus  tendineus. 


THE    MUSCLES    OF    THE    LOWER    LIMB. 


629 


Variations. — A  separation  of  any  of  the  adductor  muscles  into  distinct  portions  may  occur, 
and  indeed  the  upper  part  of  the  anterior  portion  of  the  magnus  is  usually  quite  separate  from 
the  rest  of  the  muscle  and  has  been  termed,  the  adductor  minimus.  The  posterior  fibres  of  the 
magnus  frequently  receive  their  nerve-supply  through  the  great  sciatic  nerve. 

8.   Quadratus  Femoris  (Figs.  602,  608). 

Attachments. — The  quadratus  femoris  arises  from  the  lateral  border  of  the 
tuber  ischii  and  passes  almost  directly  outward  to  be  inserted  into  the  femur  along 
the  linea  quadrati,  which  extends  a  short  distance  downward  from  about  the  middle 
of  the  intertrochanteric  line. 

Nerve-Supply. — By  a  special  nerve  from  the  fourth  and  fifth  lumbar  and  first 
sacral  nerves. 

Action. — To  rotate  the  thigh  outward,     -t    ^»-W-  wji^-tv-    /] 

Relations. — The  quadratus  femoris  is  concealed  by  the  lower  portion  of  the 
gluteus  maximus,  and  its  posterior  surface  is  crossed  by  the  great  and  small  sciatic 
nerves.      Beneath  it  lie  the  obturator  externus  and  the  termination  of  the  internal 


Fig.  603. 


V  lumbar  vertel 


Anterior  surface 


Obturator  foramen 


Symphysis  pubis  -\ 


Greater  sacro-sciatic  foramen 


nterior  sacral  for. 


Greater  sacro-sciatic  foramen 
Spine  of  ischium 
''occygeus 


NVGreater  sacro-sciatic  ligament 
^Obturator  internus 


Dissection  of  right  postero-lateral  wall  of  pelvis  from  within,  showing  pyriformis  and  obturator  internus  muscles. 


circumflex  artery.      Its  upper  border  is  in  contact  with  the  gemellus  inferior  and  its 
lower  border  with  the  adductor  magnus. 

Variations.— The  muscle  is  not  infrequently  apparently  absent,  being  fused  with  the 
adductor  magnus. 

9.    Obturator  Externus  (Figs.  552,  601). 

Attachments. — The  obturator  externus,  a  thick  triangular  muscle,  arises  from 
the  anterior  surface  of  the  lower  half  of  the  obturator  membrane  and  from  the  rami 
of  the  pubis  and  ischium  which  bound  the  lower  half  of  the  obturator  foramen.  The 
fibres  are  directed  outward,  and  converge  to  a  rounded  tendon  which  is  inserted  into 
the  floor  of  the  digital  fossa  of  the  femur. 

Nerve-Supply. — By  the  posterior  division  of  the  obturator  nerve  from  the 
third  and  fourth  lumbar  nerves. 

Action. — To  rotate  the  thigh  outward.        a  1:-  L 

10.   Obturator  Internus  (Figs.  602,  603). 
Attachments. — The  obturator  internus  arises  from  (1)  the  inner  surface  of 
the  rami  of  the  pubis  and  ischium  which  bound  the  obturator  foramen,  (2)  from  the 


630  HUMAN    ANATOMY. 

smooth  surface  of  bone  immediately  behind  the  foramen,  corresponding  to  the 
acetabulum  externally,  and  (3)  from  the  whole  of  the  inner  surface  of  the  obturator 
membrane.  Its  fibres,  passing  downward  and  backward,  converge  to  a  strong 
tendon,  which  gains  the  lesser  sacro-sciatic  foramen,  and  there,  bending  around  the 
margin  of  the  foramen,  a  bursa  (bursa  tn.  obturatoris  interni)  intervening  between 
the  tendon  and  the  bone,  passes  outward  through  the  foramen  to  be  inserted  into 
a  facet  on  the  inner  surface  of  the  greater  trochanter  of  the  femur  just  above  the 
digital  fossa. 

Nerve-Supply. — By  a  special  nerve  from  the  first,  second,  and  third  sacral 
nerves. 

Action. — To  rotate  the  thigh  outward.u*  *->rtu  H  d^iJL   \  v.  V^-v  ,  <u^  ,si-Ao>^w. 

11.   Gemelli   (Fig.  602). 

Attachments. — The  gemelli  are  two  slender  muscles  which  lie  one  on  either 
side  of  the  tendon  of  the  obturator  internus.  The  gemellus  superior  arises  from  the 
spine  of  the  ischium  and  the  gemellus  inferior  from  the  upper  part  of  the  tuber  ischii. 
Both  muscles  are  inserted  into  the  inner  surface  of  the  greater  trochanter  of  the  femur 
along  with  the  obturator  internus. 

Nerve-Supply. — The  superior  gemellus  by  the  nerve  to  the  internal  obturator 
from  the  fourth  and  fifth  lumbar  and  first  sacral  nerves  ;  the  inferior  by  the  nerve  to 
the  quadratus  femoris  from  the  first,  second,  and  third  sacral  nerves. 

Action. — To  assist  in  rotating  the  thigh  outward. 

Variations. — One  or  other  of  the  gemelli,  usually  the  superior,  is  occasionally  wanting. 
This  is  very  probably  due  to  fusion  with  adjacent  muscles,  the  gemellus  superior  with  the 
pyriformis  and  the  inferior  with  the  quadratus  femoris. 

(6)    THE  POST-AXIAL  MUSCLES. 

1.  Gluteus  maximus.  3.    Gluteus  medius. 

2.  Tensor  fascise  latse.  4.    Gluteus  minimus. 

1.   Gluteus  Maximus  (Figs.  604,  607). 

Attachments. — The  gluteus  maximus  is  an  exceedingly  thick,  coarse  muscle 
which  forms  the  principal  mass  of  the  buttock.  It  arises  from  the  lateral  surface  of 
the  posterior  portion  of  the  ilium,  behind  the  superior  gluteal  line,  from  the  pos- 
terior surface  of  the  sacrum  and  coccyx,  and  from  the  posterior  sacro-iliac  and  greater 
sacro-sciatic  ligaments.  The  fibres  pass  laterally  and  downward,  the  upper  ones 
curving  over  the  lateral  surface  of  the  greater  trochanter  of  the  femur  and  the  lower 
ones  over  the  tuberosity  of  the  ischium,  and  are  inserted  by  a  broad  tendon  partly 
into  the  ilio-tibial  band  of  the  fascia  lata  and  partly  into  the  gluteal  tuberosity  of  the 
femur. 

Nerve-Supply. — By  the  inferior  gluteal  nerve  from  the  fifth  lumbar  and  first 
and  second  sacral  nerves. 

Action. — -To  draw  the  thigh  backward  and  rotate  it  slightly  outward.  Acting 
from  below,  it  extends  the  trunk. 

Relations. — The  gluteus  maximus  is  covered  by  the  upper  posterior  portion 
of  the  fascia  lata.  It  covers  the  gluteus  medius,  pyriformis,  obturator  internus, 
gemelli,  quadratus  femoris  and  the  origin  of  the  hamstring  muscles,  and  also  the 
gluteal,  sciatic,  and  pudic  vessels  and  nerves. 

It  is  separated  from  the  lateral  surface  of  the  trochanter  major  by  a  large  bursa 
(bursa  trochanterica  m.  glutaei  maxiini),  two  or  three  additional  small  bursa?  (bursae 
glutaeofemorales)  separating  the  lower  portion  of  the  muscle  from  the  shaft  of  the 
femur.  A  bursa  is  also  frequently  present  beneath  the  muscle  where  it  passes  over 
the  ischial  tuberosity  (bursa  ischiadica  m.  glutaei  maximi). 

Variations. — The  lower  border  of  the  gluteus  maximus  is  occasionally  separated  from  the 
rest  of  the  muscle,  forming  what  may  be  termed  the  coccygeo-femoralis,  and  it  occasionally 
receives  a  slip  from  the  ischial  tuberosity,  which  has  been  named  the  ischio-femoralis. 


THE   MUSCLES    OF   THE    LOWER    LIMB. 


631 


2.  Tensor  Fasciae  Lat^e  (Figs.  600,  604). 

Attachments.— The  tensor  fasciae  latae,  also  termed  the  tensor  vagina  femo- 
ris,  is  a  flat  muscle  which 


arises  from  the  crest  of  the 
ilium,  immediately  behind 
the  anterior  superior  spine, 
and  passes  downward  and 
slightly  backward  to  be 
insei-ted  into  the  upper 
portion  of  the  ilio-tibial 
band  of  the  fascia  lata. 

Nerve-Supply. — By 
the  superior  gluteal  nerve 
from  the  fourth  and  fifth 
lumbar  and  first  sacral 
nerves. 

Action. — To  tense  the 
fascia  lata  and  at  th'e  same 
time  to  flex  the  thigh  and 
rotate  it  slightly  inward. 
OJttX^a*  *\  tUJrfl.  ' 
3.   Gluteus  Medius 

(Figs.  604,  609). 

Attachments. — The 

gluteus  medius  arises  from 

the    outer   surface  of    the 

ilium,  between  the  superior 

and  middle   gluteal   lines. 

Its  fibres   pass  downward,  1 

converging    to    a    tendon  § 

which  is  inserted  into  the 

iateral  surface  of  the  great 

trochanter    of    the    femur 

near  its  summit. 

Nerve-Supply. — By 
the  superior  gluteal  nerve 

from    the    fourth    and    fifth      Biceps,  long  head — * 

lumbar  and  first  sacral 
nerves. 

Action. — To  abduct 
'the  thigh;;-  and  by  its 
stronger  anterior  fibres  to 
rotate  it  inward.  _  Acting 
from  below,  to  flex  the 
pelvis  laterally. 

Relations. — The  an- 
terior portion  of  the  mus- 
cle is  covered  by  the  fascia 
lata  and  the  tensor  fasciae 
latae,  the  posterior  portion 
by  the  gluteus  maxim  us. 
Beneath  it  are  the  gluteus 
minimus  and  the  superior 
gluteal  vessels  and  nerve, 
its  tendon  passing  over  that 
of  the  pyriformis  near  its 
insertion. 


Fig.  604. 


Gluteus  medius 


Tensor  fasciae 
latae,  cut  at 
insertion  into 
fascia 


Rectus  femoris 


Biceps,  short  head 


-ijj — Iiio-tibial  band,  cut 


//" 


' 


Muscles  of  right  thigh,  lateral  aspect. 


A  bursa  (bursa  trochanterka  m   glutaei  medii  anterior)  is,  interposed  between  the 


6*2 


HUMAN    ANATOMY. 
Fig.  605. 


Gluteus  maximus 


■ 


X. 


-Gluteus  medius  covered  by  fascia  lata 
Anterior  superior  spine  of  ilium 

Tensor  fasciae  latae 

Fascia  lata,  cut  edges 

Symphysis  pubis 


Ilio-tibial  band 


Tendon  of  biceps 


Lateral  surface  of  right  thigh  invested  by  fascia  lati. 


THE    FEMORAL    MUSCLES. 


633 


tendon  of  the  muscle  and  the  upper  part  of  the  great  trochanter,  and  another  (bursa 
trochanterica  m.  glutaei  medii  posterior)  is  usually  present  between  the  tendon  and  that 
of  the  pyriformis. 

4.   Gluteus  Minimus  (Figs.  601,  602). 

Attachments. — The  gluteus  minimus  is  the  most  deeply  situated  of  the  gluteal 
muscles.  It  arises  from  the  lateral  surface  of  the  ilium,  between  the  middle  and 
inferior  gluteal  lines,  and  passes  downward  and  laterally  to  a  strong  tendon  which  is 
inserted  into  the  anterior  surface  of  the  great  trochanter  of  the  femur. 

Nerve-Supply. — By  the  superior  gluteal  nerve  from  the  fourth  and  fifth 
lumbar  and  first  sacral  nerves.  ^^  <ufiM-i-<S> 

Action. — To  abduct  the  thigh  ana,  acting  from  below,  to  flex  the  pelvis 
laterally.        iww^—o  rJT<4vV  \A+*-  4^0    ■ 

Relations. — Superficially  it  is'  covered  by  the  gluteus  medius  and  crossed  by 
the  superior  gluteal  vessels  and  nerve.  Deeply  it  rests  upon  the  capsule  of  the  hip- 
joint.  A  bursa  (bursa  trochanterica  m.  glutaei  minimi)  is  interposed  between  the 
tendon  and  the  great  trochanter. 

Variations.  — The  anterior  portion  of  the  muscle  is  sometimes  distinctly  separated  from 
the  rest,  forming  a  muscle  frequently  present  in  the  lower  mammals  and  termed  the  scansorius. 


THE   FEMORAL   MUSCLES. 

Many  of  the  muscles  which  belong  to  this  group  extend   the  entire  length  of 
the  thigh,  taking  their  origin,  in  whole  or  in  part,  from  the  pelvis. 

The  Fascia   Lata    (Fig.    605). — This,    the   deep  fascia  of    the  thigh,   is   a 


Fig.  606. 

5  femoris 


Vastus  intern 


Internal  intermuscular  septu 
/  Sartorius 

Internal  saphe 
/ 


External  interm 


Biceps,  long  head    Greater 
Section  across  right  thigh  through  Hunter's 


al.  seen  from  below. 


strong  layer  which  completely  encloses  the  muscles  of  the  thigh  and  covers  the  glu- 
teal region.  Its  upper  attachment,  beginning  from  behind,  is  to  the  coccyx  and 
sacrum  ;  thence  forward  along  the  entire  length  of  the  crest  of  the  ilium  and  me- 


634 


HUMAN   ANATOMY. 


Fig. 


Crest  of  ilium 


Sacral  an 
ligamentous 
origin  of  glu 
teus  maximi 


" 


Gluteus r^g 


Adductor- 
magnus 


dially  along  Poupart's  ligament  to  the  body  of  the  pubis  ;  thence  it  passes  backward 
and  downward  along  the  inferior  rami  of  the  pubis  and  ischium  to  the  ischial  tuberos- 
ity, where  it  passes  upon 
the  greater  sacro-sciatic 
ligament  and  so  back  to 
the  starting-point.  Below 
it  is  attached  to  the  bor- 
ders of  the  patella  and  be- 
comes continuous  with  the 
fascia  of  the  leg. 

The  fascia  lata  varies 
considerably  in  thickness 
in  different  regions.  Over 
the  gluteal  region  it  is  thin, 
but  over  the  great  tro- 
chanter of  the  femur  it 
becomes  greatly  thick- 
ened, and  this  thickening 
is  continued  downward 
upon  the  lateral  surface  of 
the  thigh  (Fig.  605)  as 
far  as  the  external  tuber- 
osity of  the  tibia,  forming 
what  is  termed  the  ilio- 
tibial  band  (tractus  ilio- 
tibialis).  This  receives  at 
its  upper  part  the  inser- 
tions of  the  tensor  fasciae 
lata;  and  part  of  the  glu- 
teus maximus,  and  from 
the  posterior  edge  of  its 
upper  portion  a  much 
smaller  and  feebler  band 
can  be  traced  backward  at 
first  across  and  then  below 
the  lower  portion  of  the 
gluteus  maximus  to  the 
ischial  tuberosity  ;  it  pro- 
duces the  gluteal  sulcus. 

In  its  lower  posterior 
part,  where  it  forms  the 
roof  of  the  popliteal  space, 
the  fascia  is  also  somewhat 
thickened. 

Anteriorly,  just  below 
the  inner  end  of  Poupart's 
ligament,  a  prolongation 
of  the  fascia  passes  deeply 
to  join  with  the  ilio-pec- 
tineal  portion  of  the  iliac 
fascia,  and  so  assists  in  the 
formation  of  the  sheath  for 
the  femoral  vessels.  Over 
an  oval  area,  situated 
immediately  external  to 
where  this  prolongation, 
which  is  termed  the  pubic 
portion  (Fig.  530)  of  the  fascia  lata,  is  given  off,  the  fascia  lata  is  quite  thin  and  is 
perforated  by  the  internal  saphenous  vein,  superficial  blood-vessels,  and  lymphatics  ; 


( — Vastus  externu 


Semimembranosus 


Gracilis,  tendon 


Gastrocnemius 


Superficial  dissection  of  posterior  surface  of  right  buttock  and  thigh, 
showing  muscles  undisturbed. 


THE    FEMORAL    MUSCLES. 


635 


whence  it  is  termed  the  cribriform  fascia  (fascia  cribrosa),  the  area  which  it  covers 
being  the  fossa  ova/is.     The  cribriform  fascia  is  readily  ruptured,  the  fossa  ovalis  then 


Tuberosity  of  ischium p-. 


Quadratus  femor 


-Gemellus  superior 

-  — Obturator  internus 

-  — Gemellus  inferior 
rr —  Greater  trochanter 


AcMuctor  ina^ini 


Biceps,  long  head 


-Biceps,  short  head 
..Vastus  externus 


Semimembranosus. 


..Popliteal  surface  of  femu 


_Tendon  of  biceps, 
.Gastrocnemius,  outer  head 


Muscles  of  posterior  surface  of  right  buttock  and  thigh,  gluteus 


nedius  having  been  reflected. 


appearing  as  a  perforation  in  the  fascia  lata,  termed  the  saphenous  opening.  (Fig. 
523).  The  fossa  ovalis  lies  immediately  over  (i.e.,  in  front  of)  the  lower  end  of  the 
femoral  canal,  and  is  consequently  of  importance  in  connection  with  femoral  hernia? 


636  HUMAN    ANATOMY. 

(page  1773),  which,  descending  in  the  canal,  press  against  the  thin  fascia  cribrosa  and 
may  cause  it  to  bulge  forward. 

The  part  of  the  fascia  lata  lying  to  the  outer  side  of  the  fossa  ovalis,  or  the 
saphenous  opening,  is  known  as  the  iliac  portion  (Fig.  530),  which  at  the  lateral 
margin  of  the  fossa  ovalis,  where  the  fascia  cribrosa  joins  the  fascia  lata,  is  somewhat 
thickened  to  form  a  curved  band  termed  the  falciform  process  (margo  falciformis). 
The  latter  is  prolonged  downward,  as  the  comu  inferius,  to  join  the  pubic  portion 
of  the  fascia  lata,  and  upward,  as  the  comu  superius,  also  termed  the  femoral  liga- 
ment or  Hey' s  ligament,  which  is  somewhat  stronger  and  continued  medially  to  join 
the  inner  end  of  Poupart's  and  Gimbernat's  ligaments. 

Septa  of  connective  tissue  are  continued  from  the  deep  surface  of  the  fascia  lata 
to  the  femur  separating  the  various  muscles  of  the  thigh.  Two  are  especially  strong  ; 
one,  the  internal  intermuscular  septum  (septum  intermuscularis  medialis),  passing  to 
the  inner  lip  of  the  linea  aspera,  between  the  vastus  internus  and  adductor  magnus 
muscles,  and  the  other,  the  external  intermuscular  septum  (septum  intermuscularis 
lateralis),  to  the  external  lip  between  the  short  head  of  the  biceps  and  the  vastus 
externus.  To  a  certain  extent  these  septa  furnish  surfaces  of  origin  for  some  of  the 
adjacent  muscles. 

(a)    THE  PRE-AXIAL  MUSCLES. 

1.    Biceps  femoris.  2.    Semitendinosus. 

3.   Semimembranosus. 

These  muscles  are  popularly  known  as  the  hamstring  muscles. 
1.   Biceps  Femoris  (Figs.  608,  609). 

Attachments. — The  biceps  femoris  takes  its  origin  by  two  distinct  heads. 
The  long  head  arises  from  lower  and  inner  facet  upon  the  tuberosity  of  the  ischium 
in  common  with  the  semitendinosus,  while  the  short  head  arises  from  the  whole 
length  of  the  outer  lip  of  the  linea  aspera  and  from  the  adjacent  septum  intermus- 
culare.  The  fibres  of  both  heads  are  directed  downward,  and  at  about  the  knee 
unite  in  a  common  tendon  which  passes  behind  the  outer  condyle  of  the  femur 
and  is  inserted  into  the  head  of  the  fibula,  bifurcating  to  embrace  the  long  external 
lateral  ligament  of  the  knee-joint.  Tendinous  bands  usually  extend  also  from  the 
tendon  to  the  outer  tuberosity  of  the  tibia. 

Nerve-Supply. — Both  heads  are  supplied  by  the  greater  sciatic  nerve.  The 
fibres  for  the  short  head,  however,  pass,  by  way  of  the  external  popliteal  division  of 
the  nerve,  from  the  fifth  lumbar  and  the  first  and  second  sacral  nerves,  while  those 
for  the  long  head  pass  by  the  internal  popliteal  division,  coming  from  the  first, 
second,  and  third  sacral  nerves. 

Action. — To  extend  the  thigh  and  flex  the  leg.  When  the  leg  is  flexed  the 
biceps  will  rotate  it  outward,  and  the  long  head  acting  from  below  assists  in  extend- 
ing the  trunk  upon  the  hip-joints. 

Relations. — The  common  tendon  of  origin  of  the  biceps  and  semitendinosus 
is  sometimes  separated  from  the  tendon  of  the  semimembranosus  by  a  bursa  (bursa 
m.  bicipitis  superior).  More  rarely  a  bursa  is  to  be  found  between  the  tendon  of 
insertion  of  the  biceps  and  the  lateral  head  of  the  gastrocnemius,  and  almost  con- 
stantly a  bursa  (bursa  m.  bicipitis  inferior)  separates  the  tendon  of  insertion  from  the 
fibular  collateral  ligament  of  the  knee-joint. 

Variations. — The  most  important  variations  of  the  biceps  are  an  occasional  absence  of  the 
short  head  and  an  extension  of  the  insertion  to  the  crural  fascia.  Both  these  anomalies  are 
explained  by  the  composition  of  the  muscle,  the  two  heads  not  only  representing  two  originally 
distinct  muscles,  but,  as  is  indicated  by  the  nerve-supply,  the  long  head  is  a  portion  of  the  pre- 
axial  musculature  of  the  thigh,  while  the  short  head  belongs  to  the  post-axial  group.  The  com- 
parative anatomy  of  the  muscle  shows  that  the  short  head  is  a  modified  representative  of  a 
muscle  belonging  to  the  gluteal  set,  which  extended  from  the  caudal  vertebras  to  the  fascia  of 
the  crus  and  has  only  secondarily  become  united  with  the  pre-axial  muscle,  sharing  in  its 
insertion. 


THE   FEMORAL   MUSCLES. 
Fig.  609. 


-Crest  of  ilium 


m  ■  ^ 


637 


Tuberosity  of  isch 


Adductor  magnus 


Pyriformis,  cut 


Obturator  interims 


3 — Greater  trochanter 


tQuadratus  femoris 
Tendon  of  vastus  externus 


Vastus  externu 


Biceps,  short  head 


Biceps,  long  head,  cut 


Tendon  of  semitend 


Aponeurotic  expansion  from  tendon  of 
branosus  to  posterior  liga- 


|gg    ."   I  J  ment  of  knee-joii 


Deeper  dissection  of  posterior  surface  of  right  hutlock  and  thigh,  exposing  semimembranosus 
and  short  head  of  biceps  muscles. 


638  HUMAN    ANATOMY. 

2.   Semitendinosus  (Fig.  608). 

Attachments. — The  semitendinosus  arises  from  the  tuberosity  of  the  ischium 
in  common  with  the  long  head  of  the  biceps.  Its  fibres  extend  downward  to  a  long, 
slender  tendon,  which  passes  behind  the  inner  condyle  of  the  femur  and  then  curves 
forward  along  with  the  tendon  of  the  gracilis  to  be  inserted,  below  that  tendon  and 
under  cover  of  the  expanded  tendon  of  insertion  of  the  sartorius,  into  the  inner 
surface  of  the  tibia  near  the  tuberosity. 

Nerve-Supply.— By  the  internal  popliteal  division  of  the  greater  sciatic  nerve 
from  the  fifth  lumbar  and  first  and  second  sacral  nerves. 

Action. — To  extend  the  thigh  and  flex  and  rotate  inward  the  leg.  Acting  from 
below  it  will  extend  the  trunk  upon  the  hip-joints. 

Relations. — A  large  bursa  (bursa  anserina)  intervenes  between  the  tendons 
of  the  gracilis  and  semitendinosus  and  the  tibia. 

3.   Semimembranosus  (Fig.  609). 

Attachments. — The  semimembranosus  arises  by  a  broad,  flat  tendon,  which 
extends  from  upper  and  outer  facet  upon  the  tuberosity  of  the  ischium  downward 
along  the  outer  border  of  the  muscle  to  about  the  middle  of  the  thigh.  The  muscle- 
fibres  pass  downward  and  inward  from  this  tendon  to  a  tendon  of  insertion,  which 
occupies  the  medial  border  of  the  muscle  and  passes  behind  the  inner  condyle  of  the 
femur  and  curves  forwardto  the  inner  surface  of  the  internal  condyle  of  the  tibia, 
into  which  it  is  inserted.  An  extension  of  the  tendon  of  insertion  usually  passes 
downward  and  outward  to  the  portion  of  the  deep  fascia  of  the  leg  which  covers  the 
popliteus  muscle  ;  another  band  extends  upward  and  outward  towards  the  outer  con- 
dyle of  the  femur,  blending  with  and  materially  strengthening  the  posterior  part  of 
the  capsular  ligament  of  the  knee-joint. 

Nerve-Supply. — By  the  internal  popliteal  division  of  the  greater  sciatic  nerve 
from  the  fourth  and  fifth  lumbar  and  first  sacral  nerves. 

Action. — To  flex  the  leg  and  assist  somewhat  in  rotating  it  inward.  Acting 
from  below  it  will  extend  the  trunk  upon  the  hip-joints. 

Relations. — The  semimembranosus  is  situated  in  front  of  the  long  head  of  the 
biceps  and  the  semitendinosus  and  behind  the  adductor  magnus.  The  greater 
sciatic  nerve  lies  along  its  lateral  border  (Fig.  606).  The  tendon  of  insertion  is 
separated  from  the  inner  head  of  the  gastrocnemius  by  a  bursa  (bursa  m.  seniimem- 
branosi  medialis),  which  often  communicates  with  the  synovial  cavity  of  the  knee- 
joint  ;  the  bursa  m.  semimembranosi  lateralis  intervenes  between  the  tendon  and  the 
inner  condyle  of  the  tibia. 

(b)  THE   POST- AXIAL   MUSCLES. 

1.  Sartorius.  4.    Crureus. 

2.  Rectus  femoris.  5.   Vastus  internus. 

3.  Vastus  externus.  6.    Subcrureus. 

1.   Sartorius  (Fig.  610). 

Attachments. — The  sartorius  is  a  long  band-like  muscle  which  arises  from 
the  anterior  superior  spine  of  the  ilium  and  the  adjacent  part  of  the  notch  below  it. 
It  descends  obliquely  downward  and  inward  across  the  front  of  the  thigh,  in  the 
groove  between  the  rectus  femoris  and  the  vastus  internus,  on  the  one  hand,  and  the 
adductor  muscles,  on  the  other,  and  then  passes  directly  downward  behind  the 
inner  condyle  of  the  femur.  It  finally  bends  forward  to  be  i7iserted  into  the  inner 
surface  of  the  tibia  near  the  tuberosity,  covering  the  insertions  of  the  gracilis  and 
semitendinosus. 

Nerve-Supply. — By  the  anterior  crural  nerve  from  the  second  and  third 
lumbar  nerves. 

Action.— To  flex  the  thigh  and  leg  and  to  rotate  the  thigh  outward  ;  when     . 
the  leg  is  flexed,  the  muscle  will  assist  in  rotating  the  thigh  inward.    . 


THE   FEMORAL   MUSCLES. 


639 


Relations. — As  it  passes  obliquely  across  the  upper  part  of  the  thigh,  the  sar- 
torius    forms  the  lateral  boundary  of    a  triangular  depression  which  is  known  as 


Scarpa' s  triangle  (trigonum  femorale). 
by  the  adductor  longus,  its  base  by 
Poupart's  ligament,  its  floor  by  the 
ilio-psoas  and  pectineus  and  often  to 
a  slight  extent  by  the  adductor  brevis, 
and  its  roof  by  the  fascia  lata  and 
the  cribriform  fascia.  The  space  so 
bounded  is  traversed  from  above  down- 
ward, from  the  middle  of  its  base  to 
its  apex,  by  the  femoral  vessels  and 
the  anterior  crural  and  crural  branch 
of  the  genito-crural  nerve,  and  con- 
tains a  number  of  lymphatic  nodes. 
At  its  apex  it  is  continuous  with  the 
adductor  or  Hunter's  canal. 

A  mucous  bursa  (bursa  m.  sar- 
torii  propria)  intervenes  between  the 
tendon  of  the  sartorius  and  those  of 
the  gracilis  and  semimembranosus, 
and  occasionally  communicates  with 
the  bursa  anserina  (page  638). 

The  remainder  of  the  post-axial 
musculature  of  the  thigh  is  almost  en- 
tirely represented  by  four  large  mus- 
cles, more  or  less  separable  above, 
but  united  below  in  a  common  tendon, 
which  is  inserted  into  the  upper  bor- 
der of  the  patella,  and  through  this 
and  the  ligamentum  patellae  acts  upon 
the  tuberosity  of  the  tibia.  These 
muscles  have  been  grouped  together 
as  the  extensor  quadriceps  femoris, 
and  include  the  rectus  femoris,  the 
vastus  externus,  the  crureus,  and  the 
vastus  internus. 


The  inner  boundary  of  this  triangle  is  formed 


7 — -Psoas 


-Tendon  of 
quadriceps 


2.   Rectus  Femoris  (Fig.  610). 

Attachments. — The  rectus  fem- 
oris has  a  double  origin,  the  one,  or 
st?-aight  head,    arising  from   the   an- 
terior inferior  spine  of  the  ilium,  and         IlicMi 
the  other,  or  re/lected  head,  from  the  ban 

surface  of  the  ilium  a  short  distance 
above  the  acetabulum.  The  two 
heads  give  rise  to  a  single  tendon 
which  descends  for  some  distance 
along  the  front  of  the  muscle  and,  in 
conjunction  with  a  median  septum, 
gives  origin  to  the  rmfscle-nbres. 
These  present  a  bipinnate  arrange- 
ment, and  pass  over  below  into  the 
common  tendon  to  be  eventually  in- 
serted by  the  ligamentum    patella?  into  Muscles  of  right  thigh,  anterior  aspect. 

the  tubercle  of  the  tibia. 

Nerve-Supply. — By  the  anterior  crural  nerve  from  the  third  and  fourth  lumbar 
nerves. 


-Tendo  patella 


640  HUMAN    ANATOMY. 

Action. — To  flex  the  thigh  and  extend  the  leg.  Acting  from  below  it  will  flex 
the  trunk  on  the  hip-joints. 

Relations. — The  rectus  femoris  rests  upon  the  capsule  of  the  hip-joint  above 
and  the  crureus  below.  A  bursa  frequently  intervenes  between  the  surface  of  the 
ilium  and  the  head  which  is  inserted  above  the  acetabulum. 


3.   Vastus  Externum  (Fig.  610). 

Attachments. — The  vastus  externus  (m.  vastus  lateralis)  arises  from  the  ante- 
rior intertrochanteric  line,  the  lateral  surface  of  the  greater  trochanter,  and  the  outer 
lip  of  the  linea  aspera.  The  fibres  curve  downward  and  inward  to  unite  with  the 
crureus  and  to  be  inserted  into  the  common  tendon. 

Nerve-Supply. — By  the  anterior  crural  nerve  from  the  third  and  fourth  lumbar 
nerves. 

Action. — To  extend  the  lee. 


4.   Crureus  (Fig.  606). 

Attachments. — The  crureus  (m.  vastus  intermedins)  lies  below  the  rectus 
femoris  and  between  the  vastus  externus  and  vastus  interims.  It  arises  from  the 
anterior  surface  of  the  femur  and  passes  downward  into  a  flat  tendon  which  is  i?ise?-ted 
into  the  common  tendon  a  short  distance  above  the  patella. 

Nerve-Supply. — By  the  anterior  crural  nerve  from  the  third  and  fourth  lumbar 
nerves. 

Action. — To  extend  the  leg. 

5.  Vastus  Internus  (Fig.  600). 

Attachments. — The  vastus  internus  (m.  vastus  medialis)  is  usually  so  blended 
with  the  crureus  as  to  be  hardly  separable  from  it.  It  arises  from  the  spiral  line  and 
from  the  inner  lip  of  the  linea  aspera  of  the  femur,  the  fibres  curving  downward  and 
outward  to  be  partly  united  with  the  crureus  and  partly  inserted  into  the  common 
tendon. 

Nerve-Supply. — By  the  anterior  crural  nerve  from  the  third  and  fourth  lumbar 
nerves. 

Action. — To  extend  the  leg.  Owing  to  the  oblique  direction  of  the  femur 
downward  and  inward  the  action  of  the  quadriceps  femoris  would  be  to  draw  the 
patella  outward  as  well  as  upward,  thus  tending  towards  an  outward  dislocation  of 
that  bone.  This  is  obviated,  however,  by  the  vastus  internus,  the  bulk  of  whose 
fibres  arise  from  the  lower  part  of  the  femur  and  are  directed  more  or  less  trans- 
versely outward  to  the  inner  border  of  the  common  tendon. 

Relations. — The  medial  border  of  the  vastus  internus  forms  the  outer  wall  of 
Hunter's  canal  (Fig.  606),  the  fascia  which  forms  the  roof  of  the  canal  extending 
across  between  this  muscle  and  the  adductor  magnus. 


6.    Subcrureus. 

Attachments.— The  subcrureus  (m.  articularis  genu1)  is  frequently  so  insepara- 
bly blended  with  the  crureus  that  it  may  well  be  regarded  as  the  deepest  layer  of 
the  latter  rather  than  as.  a  distinct  muscle.  It  arises  from  the  lower  part  of  the 
anterior  surface  of  the  femur  and  passes  downward  to  be  inserted  into  the  upper 
border  of  the  capsule  of  the  knee-joint. 

Nerve-Supply. — By  the  anterior  crural  nerve  from  the  third  and  fourth  lumbar 
nerves. 

Action. — To  tense  the  capsule  of  the  knee-joint. 


PRACTICAL  CONSIDERATIONS:  THE  BUTTOCKS. 


641 


PRACTICAL    CONSIDERATIONS:    MUSCLES    AND    FASCL-E 

OF   THE  BUTTOCKS,   HIP,  THIGH,  AND  KNEE. 

1.  The  Buttocks. — The  skin  over  this  region  is  thick  and  is  closely  connected 
with  the  superficial  fascia,  which  is  abundant,  loose,  and  contains  much  fat.  The  skin 
is  richly  supplied  with  nerves  from  the  small  sciatic,  the  external  and  the  perforating 
cutaneous,  the  ilio-hypogastric,  and  the  external  branches  of  the  posterior  division  of 
the  lumbar  and  sacral  nerves.  It  is  poorly  supplied  with  blood  as  compared  with 
other  cutaneous  areas,  and  hence  usually  has  a  relatively  low  surface  temperature.  It 
is  coarse,  with  numerous  sebaceous  follicles,  and  is  the  site  of  frequent  minor  forms  of 
irritation, — chafes,  bruises,  etc. , — and  is  for  these  reasons  a  common  seat  of  superficial 

Fig.  611. 


Dislocated  head  of  femur 
Obturator  internus 


Greater  sciatic  1 


Quadratus  femoris/ 


Dissection  of  posterior  luxation  of  left  femur  towards  dorsum  of  ilium. 

furuncles,  which,  on  account  of  its  intimate  union  with  the  underlying  fascia  and  its 
plentiful  nerve-supply,  are  apt  to  be  very  painful. 

The  presence  of  a  large  quantity  of  poorly  organized  fat  in  the  superficial  fascia 
and  the  frequency  of  local  irritation  render  the  region  a  favorite  seat  of  lipomata. 

The  laxity  of  the  superficial  fascia  permits  effusions  of  pus  or  of  blood  to  attain 
exceptionally  large  dimensions,  and  this  is  encouraged  by  gravity  in  the  usually 
dependent  position  of  the  part. 

The  deep  fascia  attached  to  the  back  of  the  sacrum  and  coccyx  and  to  the  crest 
of  the  ilium  covers  in  the  gluteus  medius  and  holds  it,  with  the  gluteus  minimus,  in 
an  osseo-fascial  space,  as  the  ilio-psoas  is  held  anteriorly  by  the  iliac  fascia  (page  624). 
The  posterior  space,  however,  is  completely  closed  superiorly  and  is  open  only 
mfenorly,  towards  the  thigh,  and  antero-internally,  towards  the  sciatic  foramina. 
Abscesses  or  extravasations  of  blood  in  this  space  may  originate  in,  or  may  find  their 

41 


642 


HUMAN    ANATOMY. 


Dislocated  head  of  femur 
1  artery 
Femoral  vein 


way  into  the  pelvic  cavity  ;  or,  guided  by  gravity,  they  may  travel  long  distances 
down  the  thigh  before  pointing.  They  are  apt  to  be  associated  with  much  pain 
because  of  the  compression  of  the  gluteal  and  other  branches  of  the  sacral  plexus 
between  the  bone  anteriorly  and  the  musculo-aponeurotic  wall  of  the  space  posteriorly. 
The  gluteus  maximus  is  embraced  by  a  sheath  formed  by  the  splitting  of  this 
fascia  into  two  layers,  the  superficial  one  of  which  is  thinner  and  less  dense  than  the 
deep  layer.  Abscess  or  hemorrhagic  extravasation  within  the  substance  of  that 
muscle  is,  therefore,  likely  to  give  more  external  evidence  of  its  presence  and  to  be 
less  painful  than  if  in  or  beneath  the  gluteus  medius.  The  gluteus  maximus  itself 
may  be  ruptured  by  violent  exertion  in  extending  the  pelvis  and  trunk  on  the  thigh, 
the  latter  being  fixed,  as  in  raising  a  heavy  weight  on  the  back  and  shoulders  while 
passing  from  a  stooping  to  an  erect  position,  or  in  carrying  a  similar  burden  upstairs, 
the  pelvis  and  femur  having  then  the  same  relative  position  at  each  upward  step  that 
they  have  when  the  thigh  is  vertical  and  the  trunk  and  pelvis  are  flexed.  In  the 
erect  position  the  muscle  is  relaxed.  When  it  is  paralyzed  the  patient  can  walk 
easily  on  a  level,  but  has  trouble  in  going  upstairs  or  in  exchanging  a  sitting  for  a 
standing  posture.  Wounds  of  the  buttock  without  fracture  of  the  bones  may  enter 
the  pelvic  cavity  through  the  sacro-sciatic  foramina,  and  Treves  has  recorded  a  case 

of  stab  wound  of  the 
Fig.  612.  buttock  in  which  the 

patient  died  from  peri- 
tonitis, the  wound 
having  involved  the 
bladder  and  caused  in- 
traperitoneal extrava- 
sation of  urine. 

A  subgluteal  tri- 
angle has  been  de- 
scribed (Guiteras),  the 
boundaries  of  which 
are  externally  the  fem- 
oral and  trochanteric 
insertion  of  the  glu- 
teus maximus,  inter- 
nally the  long  head 
of  thebiceps,  the  tuber 
ischii,  and  part  of  the 
sacro-sciatic  ligament, 
superiorly  the  pyri- 
formis.  The  floor  of 
the  triangle  is  made 
by  the  external  rota- 
tors and  the  adductor 
magnus.  It  is  the  re- 
gion of  aneurism  of 
or  occasional  hemorrhage  from  the  sciatic  artery,  of  emergence  of  the  sciatic  nerve, 
and  of  one  form  of  sciatic  hernia,  below  the  pyriformis.  The  ' '  triangle' '  is  an  arti- 
ficial one,  and  is  mentioned  merely  as  an  aid  to  localization  of  the  above  structures. 

The  subgluteal  bursae  are  of  considerable  importance.  One  is  found  interposed 
between  the  trochanter  and  each  of  the  gluteal  muscles  (page  630).  Inflammation 
and  enlargement  of  these  bursse  will  be  followed  by  adduction  and  flexion  of  the 
thigh,  because  active  extension  of  the  thigh,  in  which  the  glutei  aid,  and  rotation  in- 
ward, putting  them  on  the  stretch,  are  painful.  Flattening  of  the  buttock  and  oblit- 
eration of  the  gluteo-femoral  crease  may  follow  atrophy  of  the  muscles  from  disease 
(page  381).  Caries  of  the  trochanter  has  resulted  from  suppuration  in  these  bursaa. 
The  bursse  over  the  tuberosities  of  the  ischium  frequently  enlarge  and  may  cause 
two  solid  symmetrical  swellings — "weavers'  bottom" — which  require  removal. 

2.   The   Hip   and  Thigh. — The  skin  over  the  hip  is  less  dense  than  over  the 
buttock,  and  is  still  thinner  below  Poupart's  ligament  and  in  the  region  of  Scarpa's 


Adductor  longus 


Dissection  of  pubic  luxation  of  hip-joint. 


PRACTICAL    CONSIDERATIONS  :    THE    HIP   AND   THIGH. 


643 


triangle.  Over  all  the  lower  portion  of  the  thigh  it  is  loosely  connected  by  abundant 
connective  tissue  with  the  fascia  lata,  its  attachment  being  closest  along  the  line  of 
the  external  intermuscular  septum,  between  the  vastus  externus  and  the  hamstring 
muscles.  It  is  coarse  externally  and  thinner  over  the  abductor  surfaces.  It  is  easily 
stripped  up  by  effusions  or  retracted  during  operations. 

The  superficial  fascia  in  the  subinguinal  region  is  in  two  layers,  in  the  more 
superficial  of  which  is  the  subcutaneous  fat.  The  deeper  layer  is  the  denser,  and  on 
it  lie  the  lymphatic  nodes  occupying  the  saphenous  opening.  It  offers,  however,  in 
this  region,  but  little  resistance  to  the  progress  of  pus  towards  the  surface,  as  it  is 
perforated — hence  "  cribriform  fascia" — by  the  lymph- vessels  passing  from  the  super- 
ficial to  the  deep  set  of  inguinal  nodes,  by  the  superficial  epigastric  and  external 
pudic  vessels,  and  by  the  internal  saphenous  vein  to  empty  into  the  femoral. 

Lipomata  are  not  infrequent  in  this  fascia,  especially  on  the  front,  but  sometimes 
on  the  back  of  the  thigh,  and  on  account  of  its  laxity  and  of  the  absence  of  firm 
attachments  of  their  capsules,  are  apt  to  travel  downward  by  gravity. 

Fig.  613. 


Femoral  arten 
Femoral  vein 


Pectineus, 
upper  portion  '\ 
Obturator  nei 


Internal  sapl 


X  Pectineus,  lower  portion 

Adductor  longus  and  brevis,  lower  portion 
Ligamentum  teres 
Pectineus,  lower  portion 


Dissection  of  thyroid  luxation  of  femur,  showing  muscles  ruptured. 

The  deep  fascia  or  fascia  lata  (page  633),  attached  above  to  the  lower  edge  of 
the  great  sacro-sciatic  ligament,  the  tuberosity  and  ramus  of  the  ischium,  the  crest  of 
the  ilium,  Poupart's  ligament,  and  the  body  and  ramus  of  the  pubes,  and  below  to 
the  lateral  margins  of  the  patella  and  to  the  tibia,  and  continuous  posteriorly  with  the 
deep  fascia  of  the  leg,  forms  an  almost  unbroken  sheath  around  the  thigh.  Its  con- 
tinuity is  interrupted  only  by  the  saphenous  opening  (page  635).  It  is  of  sufficient 
strength  and  density  everywhere  to  influence  the  course  of  abscesses  and  to  modify 
the  surface  appearance  or  feel  of  deep  growths.  A  lipoma  beneath  the  fascia  lata  may 
apparently  have  the  density  of  a  malignant  growth.  A  psoas  abscess  (page  143), 
after  it  has  followed  the  muscle  under  and  below  Poupart's  ligament,  usually  perfo- 
rates the  sheath  and  the  fascia  lata  and  points  external  to  the  vessels  at  the  upper  part 
of  the  thigh  ;  but  after  escaping  from  the  sheath  it  mav  be  unable  to  penetrate  the 
ascia,  and  may  be  guided  by  it  to  the  lower  third  of  the  thigh,  the  knee,  or  even  as 
low  as  the  leg  or  ankle. 

The  fascia  has  been  torn  or  wounded,  and,  as  it  embraces  the  subjacent  muscles  so 
closely,  the  latter  have  bulged  through  the  opening,  appearing  on  the  surface  of  the 
thigh  as  rounded  elevations  varying  in  size  and  tension  with  the  position  of  the  limb 


644  HUMAN   ANATOMY. 

Rupture  of  the  fascia  has,  in  recorded  instances,  been  associated  with  rupture  of 
the  ilio-psoas,  the  rectus,  and  the  biceps  femoris.  The  outer  and  inner  intermuscular 
septa  (page  636)  are  of  less  surgical  importance  than  the  corresponding  structures  in 
the  arm,  and  have  but  little  effect  in  limiting  or  determining  the  course  of  a  cellulitis 
or  an  abscess. 

On  the  outer  side  of  the  thigh,  running  from  the  forepart  of  the  crest  of  the  ilium 
above  to  the  outer  tuberosity  of  the  tibia  and  the  head  of  the  fibula  below,  is  the 
thickening  of  the  fascia  lata  known  as  the  ilio-tibial  band,  the  dense,  glistening  fibres 
of  which  bridge  over  the  supratrochanteric  space  between  the  summit  of  the  trochan- 
ter and  the  iliac  crest.  Normally  at  this  point  the  band  offers  distinct  resistance  to 
pressure  with  the  fingers.  In  fracture  of  the  neck  of  the  femur,  with  shortening,  it 
must  be  relaxed  and  less  resistant  (Allis),  and  this  sign  is  of  especial  value  in  obscure 
cases  of  impacted  fracture  of  the  neck  in  which  crepitus,  preternatural  mobility,  and 
other  of  the  conventional  symptoms  of  fracture  are  lacking  (pages  364,  367,  390). 

The  relations  of  the  muscles  about  the  hip  to  dislocation  (Figs.  395,  396,  pages 
377,  378)  and  to  hip  disease  (page  381)  have  been  described.  Suppuration  affecting 
the  iliacus  or  the  ilfo-psoas  has  also  been  dealt  with  (page  381). 

Strains  of  the  ilio-psoas  muscle  are  not  infrequent,  and  may,  especially  in  chil- 
dren, give  rise  to  a  mistaken  diagnosis  of  hip-joint  disease.  In  sprains,  however, 
the  movements  of  the  joint  that  do  not  affect  the  ilio-psoas  will  be  painless  and  most 
of  the  other  anatomical  symptoms  (page  380)  will  be  absent. 

The  extensive  bursa  between  the  capsule  of  the  hip-joint  and  the  ilio-psoas 
muscle  {ilio-psoas  bursa)  may  enlarge  and  become  visible  at  the  front  of  the  thigh 
below  the  middle  of  Poupart's  ligament.  The  thigh  will  be  found  flexed  from  reflex 
irritation  of  the  ilio-psoas  and  to  lessen  pressure  on  the  bursa  (page  381).  As  the 
latter  not  infrequently  communicates  with  the  hip-joint,  infectious  disease  of  one  may 
extend  to  the  other. 

The  adductors  are  also  often  strained  or  overworked,  particularly  during  horse- 
back exercise,  and  are  sometimes  sprained  or  stretched  close  to  their  pelvic  origins. 
The  latter  injury  may  result  in  a  sclerosis  of  one  of  the  adductor  tendons,  possibly 
going  on  to  true  ossification,  and  producing  a  condition  seen  oftenest  in  cavalrymen, 
and  known  as  "  rider's  bone." 

Fractures  of  the  femur  situated  below  the  neck  (page  363)  and  above  the  con- 
dyles (page  366)  are  much  influenced  by  muscular  action,  as  might  be  expected  from 
the  number  and  strength  of  the  muscles  concerned.  Three  of  these  fractures  may 
be  considered  in  this  relation  : 

1.  Fracture  just  below  the  trochanters  (subtrochanteric  fracture).  This  is  one 
of  the  most  difficult  of  femoral  fractures  to  manage  because  of  the  flexion,  abduc- 
tion, and  outward  rotation  of  the  upper  fragment,  caused  by  the  action  of  the  ilio- 
psoas, the  gluteus  minimus  and  medius,  the  obturators,  quadratus,  pyriformis,  and 
gemelli.  The  lower  fragment  is  drawn  upward  by  the  rectus,  gracilis,  tensor  fasciae 
lata?,  and  sartorius,  upward  and  inward  by  the  adductors,  upward  and  a  little 
backward  by  the  hamstrings.  In  the  treatment,  elevation  and  abduction  of  the  thigh 
— i.  e. ,  of  the  lower  fragment — are  often  resorted  to  for  obvious  reasons. 

2.  Fracture  of  the  middle  of  the  shaft  is  very  frequent  (page  365).  It  is 
usually  moderately  oblique  from  behind  downward  and  forward.  The  upper  frag- 
ment is  almost  always  in  advance  of  the  lower  fragment  because  (a)  the  fracturing 
force  is  more  apt  to  be  applied  from  in  front  and  to  the  lower  rather  than  the  upper 
part  of  the  thigh  ;  (6)  the  weight  of  the  limb  in  the  supine  position  would  favor  a 
posterior  position  of  the  lower  fragment  ;  (c)  the  ilio-psoas  tends  to  advance  the 
upper  fragment,  and  the  adductor  magnus  and  gastrocnemius  draw  the  lower  frag- 
ment somewhat  backward  (Fig.  614).  There  is  often  a  forward  angulation  or  bow- 
ing in  the  direction  of  the  normal  curve  of  the  femoral  shaft  (page  365),  thought  to 
be  due  to  the  action  of  the  adductors  which  subtend  the  arc  of  the  curve. 

The  shortening  is  produced,  as  usual,  by  the  muscles  running  from  the  pelvis 
to  the  thigh  and  leg. 

3.  Fracture  just  above  the  condyles  (supracondylar  fracture).  This  is  usually 
the  result  of  severe  injury  or  of  direct  violence.  It  is  commonly  oblique  from  be- 
hind forward  and  downward.      The  fracture  takes  place  at  about  the  point  of  junction 


PRACTICAL    CONSIDERATIONS  :    THE    KNEE. 


645 


of  the  compact  tissue  of  the  shaft  with  the  cancellated  tissue  of  the  expanded  lower 
extremity.  It  is  from  one  to  two  inches  higher  than  the  epiphyseal  line.  The  same 
backward  rotation  of  the  lower  fragment  occurs  as  in  disjunction  of  the  epiphysis 
(page  365),  and  in  both  cases  from  the  action  of  the  gastrocnemius.  In  the  fracture, 
however,  the  sharp  lower  end  of  the  upper  fragment  is  far  more  apt  to  project  ante- 
riorly than  is  the  diaphysis  in  cases  of  epiphyseal  disjunction.  It  is  not  infrequently 
entangled  in  fibres  of  the  rectus  and  may  lacerate  the  suprapatellar  synovial  pouch. 
The  difference  probably  results  from  the  character  of  the  fracturing  force,  which  in  the 
epiphyseal  accident  is,  in  the  majority  of  cases,  hyperextension  of  the  leg  on  the 
thigh.  The  action  of  the  ilio-psoas  tends  to  advance  the  lower  end  of  the  upper 
fragment,  but  must  be  feeble.  The  pectineus  slightly  and  the  adductors  quite  strongly 
draw  it  inward.  The  shortening  is  produced  by  the  hamstrings,  rectus,  sartorius, 
etc.  The  most  difficult  element  of  the  deformity  to  do  away  with  is  the  posterior 
rotation  of  the  lower  fragment,  which  may  also  result  in  serious  pressure  upon  or 
injury  to  the  popliteal  vessels  and  nerves.  In  setting  such  a  fracture  it  may  be  neces- 
sary to  relax  the  chief  muscles  concerned  by  flexing  the  thigh  to  a  right  angle  with 


Fig.  614. 


Popliteal  artery 


Dissection  of  fracture  of  upper  third  of  r 
showing  forward  and  inward  displac 


Dissection  of  fracture  of  lower  third  of  left  femur,  show- 
ing displacement  of  popliteal  artery  by  lower  fragment. 


the  pelvis  to  relax  the  ilio-psoas,  drawing  the  knee  inward  a  little  to  relax  the  ad- 
ductors, and  flexing  the  leg  on  the  thigh  to  relax  the  gastrocnemius,  and  then  to 
make  extension  by  means  of  the  forearm  placed  in  the  ham.  Not  uncommonly  the 
displacement  recurs  so  obstinately  that  it  becomes  necessary  to  treat  the  case  with 
the  leg  fully  flexed  on  the  thigh,  and  even  to  divide  the  tendo  Achillis. 

3.  The  Knee. — The  skin  over  the  front  of  the  knee  is  dense,  coarse,  and 
loose,  qualities  that  diminish  the  gravity  of  the  frequent  injuries  to  the  integument 
itself  and  also  serve  to  protect  the  underlying  joint,  "  especially  in -stabs  with  bluntish 
instruments"  (Treves)  and,  in  fact,  in  many  forms  of  accident  in  which  the  free 
movement  of  the  skin  over  the  subjacent  structures  serves  to  make  the  application  of 
force  to  the  latter  much  less  direct. 

In  full  flexion  the  skin,  in  spite  of  its  laxiry,  is  drawn  tensely  over  the  patella, 
and  a  fall  may  result  in  an  extensive  wound. 

The  relation  of  the  cutaneous  nerves  and  vessels  over  the  knee  to  those  supply- 
ing the  articulation  should  be  studied  in  connection  with  the  common  application  of 
counterirritants  or  of  blisters  to  the  re°ion. 


646 


HUMAN    ANATOMY. 


Fig.  €r6. 


The  quadriceps  tendon  is  separated  from  the  femur  by  a  large  bursa,  which,  in 
from  70  to  80  per  cent,  of  cases,  communicates  with  the  knee-joint  and  may  be  in- 
volved in  its  diseases.  When  separate  from  the  joint  and  distended  by  effusion,  it 
may  be  mistaken  for  synovitis  of  the  knee,  but  the  patella  will  not  be  floated  up  and 
the  concavities  at  either  side  of  that  bone  and  those  at  the  sides  of  the  ligamentum 
patellae  will  not  be  effaced. 

The  prepatellar  bursa,  separating  the  patella  from  the  skin,  is  frequently  enlarged 
in  persons  who  spend  much  time  kneeling, — "  housemaid's  knee." 

The  bursa  between  the  ligamentum  patellae  and  the  tubercle  of  the  tibia  may  be 
enlarged  or  inflamed,  and  is  then  apt  to  be  painful  on  account  of  its  compression 
between  two  non-distensible  structures,  the  bone  and  the  ligament.  The  little  pad 
of  fat  (page  400)  between  the  tubercle  and  the  ligament,  which  protrudes  at  the  sides 
of  the  latter  when  the  quadriceps  extensor  is  in  action  (page  405),  should  not  be  mis- 
taken for  enlargement  of  this  bursa. 

Posteriorly — over  the  ham — the  skin  is  thinner  and  less  movable.  The  deep 
fascia — here  the  popliteal  fascia — is  dense  and  exerts  marked  obstruction  to  the  exten- 
sion of  abscess,  growth,  or  aneurism  towards 
the  surface,  in  this  way  causing  severe  pain 
from  the  pressure  upon  the  nerves  that  run 
through  the  space.  As  the  latter  is  open 
above  and  below,  abscesses  may  extend  in 
either  direction. 

Pus  or  infection  may  be  guided  to  the 
subfascial  region  in  the  ham  from  the  pelvis 
or  the  buttock  by  the  great  sciatic  nerve,  or 
from  the  thigh  by  the  femoral  vessels,  or 
from  the  leg  by  the  short  saphenous  vein, 
or  by  the  deeper  vessels  and  the  lymphatics. 
The  relations  of  the  fascia  and  muscles 
of  the  thigh  to  the  patella  and  the  knee- 
joint  and  to  their  injuries  and  diseases  have 
been  sufficiently  described  (Figs.  424-430, 
pages  409-418). 

The  hamstring  tendons  are  not  infre- 
quently divided,  as,  for  reasons  already 
given,  ankylosis  of  the  knee-joint  is  usu- 
ally in  the  position  of  flexion  (page  412). 
They  are  made  very  tense  when  the  pelvis  is  strongly  flexed  on  the  thigh,  the  knee 
remaining  extended.  They  may  be  ruptured  if  excessive  force  is  applied  under 
these  circumstances. 

The  biceps  tendon  is  easily  felt  on  the  outer  side  of  the  ham,  with  the  peroneal 
nerve,  also  readily  palpable,  lying  against  its  inner  and  posterior  border.  At  the  inner 
side  of  the  ham  the  semitendinosus  tendon  is  nearer  the  mid-line,  nearer  the  surface, 
more  easily  outlined,  thinner,  and  more  cord-like  than  the  semimembranosus  tendon, 
which  is  the  most  deeply  situated  of  the  three  hamstrings.  The  line  for  dividing 
these  tendons  is  preferably  a  little  above  the  level  of  the  knee-joint  and  about  opposite 
the  most  salient  parts  of  the  femoral  condyles. 

In  the  popliteal  region  there  are  several  bursse  :  (a)  the  largest  is  between  the 
inner  head  of  the  gastrocnemius  and  the  semimembranosus  and  the  inner  condyle  of 
the  femur,  extending  downward  to  the  inner  tibial  tuberosity  and  even  as  low  as  the 
upper  margin  of  the  popliteus  ;  it  communicates  with  the  joint  in  50  per  cent,  or 
more  of  cases  (Foucher,  Gruber) ;  (&)  a  smaller  bursa  is  found  between  the  semi- 
membranosus and  the  internal  tuberosity  of  the  tibia,  communicating  usually  with 
the  above-described  bursa.  Externally  there  are  :  (c)  a  bursa  between  the  lateral 
ligament  and  the  tendon  of  the  popliteus  ;  (d)  a  bursa — a  diverticulum  of  the  syno- 
vial membrane  of  the  knee  (Nancrede) — between  the  same  tendon  and  the  external 
tibial  tuberosity  ;  (e)  a  bursa  between  the  external  lateral  ligament  and  the  biceps 
tendon,  in  close  relation  to  the  external  popliteal  nerve  ;  and  (/)  a  bursa  between 
the  outer  head  of  the  gastrocnemius  and  the  external  condyle  of  the  femur. 


Ya^tu^  interims 


Fractured  surfaces 
of  patella 


fibrous  expansion 
from  patella  to  capsu- 
lar ligament  of  knee- 
joint 


Dissection  of  fracture  of  patella. 


THE   CRURAL   MUSCLES.  647 

Nancrede  says,  that  of  the  six  popliteal  bursae,  one — the  subpopliteal  (d ) — 
always  communicates  with  the  joint,  and  occasionally  with  the  upper  tibio-fibular 
joint  (Gruber)  ;  one — that  between  the  gastrocnemius  and  the  semimembranosus 
(a\ — generally  does  so  ;  and  one  (c)  occasionally  does  so. 

Enlargement  of  these  bursae  leads  to  stiffness  and  disability  in  the  use  of  the 
knee.  Extension  may  be  painful  and  may  show  the  presence  of  a  tense,  rounded, 
fluctuating  swelling.  This  will  usually  be  at  the  inner  side  of  the  popliteal  region, 
because  the  bursa  beneath  the  gastrocnemius  and  semimembranosus — the  largest  of 
the  bursa? — is  the  one  most  often  enlarged. 

It  may,  on  account  of  the  transmitted  pulsation,  be  mistaken  for  an  aneurism, 
but  should  be  distinguished  by  the  facts  that,  if  due  to  bursal  enlargement,  the  swell- 
ing— unlike  that  of  aneurism — may  (a)  lessen  or  quite  disappear  when  the  knee  is 
slightly  flexed,  the  narrow  passage  between  the  bursal  sac  and  the  joint  being  com- 
pressed when  the  posterior  ligament  is  tense  and  patulous  when  it  is  relaxed  ;  (0) 
reappear  slowly  and  not  almost  instantly  ;  (t)  become  tenser  and  more  prominent  on 
full  extension  ;  (d)  will  have  a  transmitted,  not  an  expansile  pulsation;  and  (e) 
will  be  unaffected  as  to  bulk  by  digital  compression  of  the  femoral  artery. 

A  popliteal  lipoma — the  only  other  condition  likely  to  be  confused  with  a  non- 
suppurating,  enlarged  bursa — occupies  no  definite  position  in  the  ham,  has  no  sharply 
defined  outline,  undergoes  little  or  no  increase  of  tension  when  the  leg  is  extended, 
and  is  apt  to  have  attachments  to  the  deep  surface  of  the  skin  (Nancrede). 

THE   CRURAL   MUSCLES. 

The  crural  muscles  are  primarily  inserted  into  the  bones  of  the  leg  or  into  the 
tarsus,  but,  like  the  antibrachial  muscles,  many  of  them  have  been  extended  into 
the  foot  and  act  upon  the  digits. 

The  crural  fascia  is  a  strong  aponeurotic  sheath  investing  the  muscles  of  the 
leg,  at  the  knee  being  continuous  with  the  fascia  lata  and  below  with  the  fascia  of 
the  foot.  Over  the  external  and  internal  malleoli  and  along  the  entire  inner  surface 
of  the  tibia  the  fascia  blends  with  the  subjacent  periosteum  ;  from  the  last  of  these 
attachments  a  deep  layer  is  given  off  which  passes  across  to  the  fibula,  between  the 
superficial  and  deeper  muscles  of  the  back  of  the  leg.  That  portion  of  the  fascia 
which  covers  the  muscles  of  the  front  of  the  leg  is  exceedingly  strong,  but  it  is 
thinner  over  the  calf.  The  upper  part  of  its  posterior  portion  is  somewhat  thickened, 
and  forms  part  of  the  roof  of  the  popliteal  space.  Below  the  fascia  is  strengthened 
bv  transverse  fibres  which  form  bands  that  bind  down  the  tendons  passing  over  the 
ankle-joint. 

Of  these  bands  two  are  situated  upon  the  anterior  surface  of  the  ankle-joint, 
together  forming  the  structure  termed  the  anterior  aimnlar  ligament  (Fig.  623). 
The  upper  or  vertical  portion  of  this  (ligamentum  transversum  cruris)  extends  trans- 
versely across  between  the  lower  ends  of  the  tibia  and  fibula,  a  little  above  the  ankle- 
joint.  The  space  beneath  this  band  is  divided  by  a  partition  into  two  compartments, 
the  more  lateral  of  which  contains  the  extensor  longus  hallucis  and  the  extensor 
longus  digitorum,  enclosed  by  separate  synovial  sheaths,  while  the  more  medial  one 
contains  the  tibialis  anticus.  The  lower  or  horizontal  portion  of  the  ligament  (liga- 
raentum cruciatura )  is  Y-shaped.  Externally  it  is  attached  to  the  outer  surface  of 
the  calcaneum  and  passes  inward,  enclosing  the  tendons  of  the  extensor  longus  digi- 
torum, and  then  divides  into  two  limbs,  the  upper  of  which  passes  upward  and 
inward,  over  the  tendons  of  the  extensor  longus  pollicis  and  the  tibialis  anticus,  to 
be  inserted  into  the  inner  malleolus,  just  below  the  medial  end  of  the  ligamentum 
transversum.  The' lower  limb  passes  downward  and  inward  to  be  attached  to  the 
inner  border  of  the  plantar  fascia. 

On  the  posterior  surface  three  bands  occur.  Two  of  these  serve  to  bind  down 
the  tendons  of  the  peroneus  longus  and  brevis  as  they  pass  behind  the  external  mal- 
leolus, together  forming  the  lateral  annular  ligament  (retinacula  mm.  peronaeorum). 
The  upper  band  extends  downward  and  backward  from  the  outer  malleolus  to  the 
calcaneum,  while  the  lower  one,  arising  from  the  calcaneum  at  the  point  at  which 
the  outer  end   of    the   cruciate  ligament  is   attached,   extends  backward   over  the 


64S 


HUMAN    ANATOMY. 


peroneal  tendons  to  be  attached  to  the  tuberosity  of  the  same  bone.  The  other 
band,  the  internal  annular  ligament  (ligamentum  laciniatum)  passes  downward  and 
backward  from  the  inner  malleolus  to  the  calcaneum,  bridging  over  a  groove  which 
is  divided  into  four  compartments  by  partitions  extending  from  the  ligament  to  the 
subjacent  bone.  The  innermost  of  these  compartments  is  occupied  by  the  posterior 
tibial  muscle  ;  the  second  one  contains  the  tendon  of  the  flexor  longus  digitorum  ; 
the  third,  the  posterior  tibial  vessels  and  nerve  ;  and  the  outermost,  the  tendon  of 
the  flexor  longus  hallucis. 

From  the  deep  surface  of  that  portion  of  the  crural  fascia  which   covers  the 
peroneus  longus  and  brevis  two  strong  expansions  of  connective  tissue  pass  deeply, 


Fig.  617. 


Anterior  tibial  artery 
Anterior  tibial 

Extensor  longus  digit 

Musculo-cutaneous  nerv 

Extensor  longus  halluc 

Peroneus  longu: 

Peroneus  brev 

Fibul; 

Extern,  intermuscular  sept 

Flexor  longus  hall 

Peroneal  vessels' 
Deep  fascial  septum. 

Gastrocnemius,  outer  hea> 


Tibialis  anticus 

Interosseous  1 


Tibialis  posticus 

Flexor  longus  digitorum 
Internal  saphenous  vein 
Posterior  tibial  vessels 
Internal  saphenous  nerve 
Posterior  tibial  nerve 


Tendon  of  plantaris 
Gastrocnemius,  inner  head 


Section  across  right  leg  at  junction  of  upper  and 


Superficial  fascia 
liddle  thirds,  viewed  from  belo 


one  in  front  of  and  one  behind  the  muscles,  to  be  attached  to  the  fibula.  Theseare 
the  anterior  and  posterior  intermuscular  septa  ;  they  serve  for  the  origin  of  portions 
of  the  adjacent  muscles. 

In  regions  in  which  the  crural  fascia  is  adherent  to  subjacent  bony  structures  a 
number  of  subcutaneous  bursa  occur  between  the  deep  fascia  and  the  integument. 
Thus,  over  the  patella  there  is  usually  to  be  found  a  bursa  (bursa  prepatellaris  sub- 
cutanea)  ;  occasionally  one  (bursa  prepatellaris  subfascialis )  occurs  between  the 
patella  and  the  fascia.  Another  (bursa  infrapatellaris  subcutanea)  frequently  lies  over 
the  ligamentum  patella;,  and  immediately  below  it  the  bursa  subcutanea  tuberositatis 
tibiae.  Again,  over  each  malleolus  a  bursa  often  exists  (bursae  malleoli  lateralis  et 
medialis) ;  finally,  a  bursa  frequently  occurs  over  the  tendo  Achillis  at  its  insertion 
into  the  tuberosity  of  the  calcaneum  (bursa  subcutanea  tendinis  calcanei). 


(a)  THE   PRE-AXIAL  MUSCLES. 

As  is  the  case  with  the  antibrachial  pre-axial  muscles,  those  of  the  crus ;  are 
primarily  arranged  in  three  layers,  the  most  superficial  sheet  being  attached  above 
to  the  condyles  of  the  femur,  for  the  most  part  to  the  outer  one.  A  further  simi- 
larity to  the  arrangement  in  the  forearm  is  to  be  found  in  the  continuation  of  the 
muscles  of  the  middle  layer  into  the  foot,  to  act  as  flexors  of  the  digits. 


THE   CRURAL    MUSCLES.  649 

(aa)  The  Superficial  Layer. 

1.    Gastrocnemius.  2.    Soleus. 

3.   Plantaris. 

The  main  mass  of  the  calf  of  the  leg  is  formed  by  two  muscles,  the  gastroc- 
nemius and  the  soleus,  which  unite  below  in  a  common  tendon,  the  tendo  Achillis 
(tendo  calcaneus),  inserted  into  the  posterior  surface  of  the  tuberosity  of  the  calca- 
neum,  a  bursa  (bursa  tendinis  calcanei)  intervening  between  the  tendon  and  the  upper 
part  of  the  tuberosity.  Since  the  gastrocnemius  arises  by  two  heads,  these  two 
muscles  together  are  sometimes  spoken  of  as  the  triceps  sum. 

Gastrocnemius  (Fig.  618). 

Attachments. — The  gastrocnemius  takes  origin  by  two  heads.  The  ozder 
head  arises  from  the  posterior  surface  of  the  femur,  just  above  the  lateral  condyle, 
by  a  short,  strong  tendon  which  sometimes  contains  a  sesamoid  cartilage  ;  the  imier 
head  arises  also  by  a  short  tendon  just  above  the  medial  condyle  of  the  femur. 
Above,  the  two  heads  are  separated  from  each  other  by  a  groove,  but  below  they 
unite  to  form  a  thick  belly,  the  fibres  of  which  pass  over  into  a  broad,  flat  tendon 
inserted  below  with  the  tendo  Achillis. 

Nerve-Supply. — By  the  internal  popliteal  (tibial)  division  of  the  greater  sciatic 
nerve  from  the  first  and  second  sacral  nerves. 

Action. — To  extend  the  foot  and  to  assist  in  flexing  the  knee-joint. 

Relations. — The  gastrocnemius  is  in  relation  by  its  posterior  surface  with  the 
short  saphenous  vein  and  nerve.  On  its  deep  surface  it  is  in  contact  with  the 
plantaris  and  soleus  muscles  (Fig.  617),  and  in  its  upper  part  with  the  capsule  of 
the  knee-joint,  the  popliteus,  and  the  popliteal  vessels  and  nerves. 

A  bursa  (bursa  m.  gastrocnemii  medialis)  intervenes  between  the  inner  head  and 
the  capsule  of  the  knee-joint,  with  the  synovial  cavity  of  which  it  is  frequently 
continuous;  the  bursa  m.  gastrocnemii  lateralis  frequently  presents  similar  relations  to 
the  outer  head. 

Variations. — Absence  of  the  entire  muscle  or  of  the  outer  head  has  been  observed,  but  the 
most  frequent  anomaly  is  the  occurrence  of  a  third  head  which  arises  from  some  portion  of  the 
popliteal  surface  of  the  femur. 

2.    Soleus  (Fig.  619). 

Attachments. — The  soleus  is  a  broad,  flat  muscle  which  arises  from  the  head 
and  upper  posterior  portion  of  the  fibula,  from  the  oblique  line  of  the  tibia,  and  from 
a  tendinous  arch  which  passes  across  between  the  tibial  and  fibular  origins.  Its 
fibres  pass  downward  to  a  broad  tendon  which  joins  with  the  tendo  Achillis  below. 

Nerve-Supply. — By  the  internal  popliteal  (tibial)  division  of  the  greater  sciatic 
nerve  from  the  first  and  second  sacral  nerves. 

Action. — To  extend  the  foot. 

3.    Plantaris  (Fig.   619). 

Attachments. — The  plantaris  is  a  small  spindle-shaped  muscle  which  passes 
over  into  a  long,  slender  tendon  extending  downward  between  the  gastrocnemius 
and  soleus.  The  muscle  arises  from  the  femur,  just  above  the  outer  condyle,  internal 
to  the  lateral  head  of  the  gastrocnemius,  and  from  the  adjacent  part  of  the  posterior 
ligament  of  the  knee-joint.  The  tendon  traverses  almost  the  entire  length  of  the  leg 
and  is  inserted  either  into  the  tuberosity  of  the  calcaneum  along  with,  but  to  the 
inner  side_ of,  the  tendo  Achillis,  sending  also  some  fibres  to  the  internal  annular  liga- 
ment, or  into  the  tendo  Achillis  itself. 

Nerve-Supply. — By  the  internal  popliteal  (tibial)  division  of  the  greater  sciatic 
nerve  from  the  fifth  lumbar  and  first  sacral  nerves. 


650 


HUMAN   ANATOMY. 


Fig.  618. 


-External  condyle  FlG.   619. 


Intermuscular  septum 
(to  posterior  border 
of  fibula) 


Intermuscular  septum 


Muscles  of'  P»>-f ^f^U'g- 


Superficial  dissection  of  posterior  sur-  gastrocnemius  has  beei 

.  of  right  leg,  showing  muscles  undis-  posing  plantaris  and  so.eus 


face  of  right  leg,  show 
turbed. 


THE    CRURAL    MUSCLES.  651 

Action. — To  assist  in  extending  the  foot  and  to  tense  the  crural  fascia  at  the 
ankle-joint. 

Variations. — The  plantaris  is  absent  in  about  7  per  cent,  of  cases.  Its  insertion  may  be 
into  the  calcaneum,  the  tendo  Achillis,  the  crural  fascia,  or  even  into  the  plantar  aponeurosis. 

(bb)  The  Middle  Layer. 
I.    Flexor  longus  digitorum.      2.    Flexor  longus  hallucis. 

1.    Flexor  Longus  Digitorum  (Figs.  620,  628). 

Attachments. — -The  long  flexor  of  the  toes  (m.  flexor  digitorum  longus)  arises 
from  almost  the  whole  of  the  posterior  surface  of  the  tibia  below  the  oblique  line  and 
from  the  deep  surface  of  the  deep  layer  of  the  crural  fascia.  Its  fibres  converge  in  a 
bipinnate  manner  to  a  tendon  which  passes  laterally  to  the  tendon  of  the  tibialis 
anticus  beneath  the  internal  annular  ligament,  and  so  reaches  the  plantar  region  of 
the  foot.  There  it  is  directed  somewhat  laterally,  receiving  the  insertion  of  the  flexor 
accessorius,  and  divides  into  four  tendons  which,  passing  through  the  divided  ten- 
dons of  the  flexor  brevis,  are  inserted  into  the  base  of  the  third  or  distal  phalanx  of 
the  second,  third,  fourth,  and  fifth  toes. 

Nerve-Supply. — By  the  posterior  tibial  nerve  from  the  fifth  lumbar  and  first 
sacral  nerves. 

Action. — To  flex  the  second,  third,  fourth,  and  fifth  toes  ;  continuing  its  action, 
to  extend  the  foot  and  to  cause  slight  inversion  of  the  sole. 

Relations. — In  the  leg  (Fig.  617)  the  flexor  longus  is  covered  by  the  soleus 
and  has  resting  upon  it  the  lower  portions  of  the  posterior  tibial  vessels  and  nerve. 
It  rests  upon  the  tibialis  posticus,  crossing  it  obliquely  in  the  lower  part  of  the  leg. 
In  the  foot  its  tendons  are  covered  by  the  flexor  brevis  digitorum,  and  pass  between 
the  two  terminal  slips  of  the  tendons  of  that  muscle  over  the  first  phalanges.  Its 
tendon  is  also  covered  by  the  abductor  hallucis,  and  crosses  obliquely  the  tendon  of 
the  flexor  longus  hallucis  and  the  oblique  portion  of  the  adductor  hallucis.  The 
lumbricales  take  their  origin  from  its  tendons,  and  it  receives  the  insertion  of  the 
flexor  accessorius. 

Variations. — A  flexor  digitorum  longus  accessorius  is  occasionally  found  arising  indepen- 
dently from  the  tibia  or  from  the  fibula  and  joining  the  tendon  of  the  long  flexor  below,  or  else 
uniting  with  the  flexor  accessorius. 

2.  Flexor  Longus  Hallucis  (Figs.  620,  628). 

Attachments. — The  long  flexor  of  the  great  toe  (m.  flexor  hallucis  longus)  arises 
from  the  posterior  surface  of  the  fibula,  from  the  posterior  intermuscular  septum, 
and  from  the  deep  surface  of  the  deep  layer  of  the  crural  fascia.  Its  fibres  converge 
bipinnately  to  a  tendon  which  passes  beneath  the  internal  annular  ligament,  pos- 
terior to  the  posterior  tibial  vessels  and  nerve,  and  so  enters  the  plantar  surface 
of  the  foot.  There  it  passes  beneath  the  tendon  of  the  flexor  longus  digitorum, 
to  which  it  sends  a  slip,  and  continues  distally  to  be  inserted  into  the  base  of  the 
distal  phalanx  of  the  great  toe,  passing  between  the  flexor  brevis  hallucis  and  the 
first  plantar  interosseous. 

Nerve-Supply. — By  the  posterior  tibial  nerve  from  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves. 

Action. — To  flex  the  hallux  and  extend  and  slightly  supinate  the  foot. 

Variations. — The  principal  variations  of  the  flexor  longus  hallucis  concern  its  union  with 
the  tendon  of  the  flexor  longus  digitorum.  The  passage  of  a  slip  between  the  two  tendons  is 
constant,  but  its  distribution  to  the  tendons  of  the  flexor  digitorum  varies  considerably.  Usually 
it  separates  into  two  slips  which  pass  to  the  tendons  for  the  second  and  third  toes,  but  it  may  also 
pass  to  the  tendons  for  the  second,  third,  and  fourth  toes,  to  that  of  the  second  alone,  or  even 
to  all  the  tendons  of  the  flexor  longus  digitorum.  It  may  also  completely  replace  the  tendon 
usually  passing  from  the  flexor  longus  digitorum  to  the  second  digit. 


652 


HUMAN    ANATOMY. 


These  variations  of  the  flexor  longus  hallucis  are  explicable  on  the  basis  that  its  history, 
together  with  that  of  the  flexor  longus  digitorum,  has  been  very  similar  to  that  of  the  flexor 


Fig.  620. 


Tendon  of  semimembranosus  — 


Gastrocnemius 


Plantaris,  cut 
Head  of  fibula 


Peroneus  longus 
Soleus,  cut 


Tibialis  posticus 


Wlls — Flexor  longus  hallucis 


Tendon  of  peroneus  longus 


Tendo  Achillis,  stump 
Internal  lateral  ligament 


Inner  tubercle  of  os  calcil 
Outer  tubercle  of  os  calci 


Flexor  brevis  digitorum,  stump 
minimi  digiti 


uctor  minim 
Flexor  accessorius 

Flexor  brevis  minimi  digiti 
Interosseus 


-  Tendons  of  flexor  brevis  digitorum 
Deeper  dissection  of  right  leg,  showing  flexors  passing  into  foot. 

sublimis  digitorum  and  flexor  longus  pollicis  of  the  forearm.  Tn  other  words,  these  muscles 
represent  a  layer  of  muscle-tissue  which  primarily  arose  from  the  bones  of  the  leg  and  was  in- 
serted into  the  deeper  layers  of  the  plantar  aponeurosis.     Later  tendons  differentiated  from  the 


THE   CRURAL   MUSCLES. 


653 


plantar  aponeurosis  and  the  muscles  were  continued  to  the  digits.     The  separation  of  the  flexor 
hallucis  from  the  rest  of  the  muscle  took  place  later,  and  even  yet  is  somewhat  incomplete,  the 


Internal  condyle 


Internal  latum!  ligament  — 


JJgg — Tendon  of  popliteus 
Head  of  fibula 


Anterior  tibial  artery 


Peroneus  longus 


Flexor  longus  digit- 
drawn  aside 


Tibialis  posticus 


Inner  malleolus. 


Internal  lateral  ligament 

Tibialis  anticus tij 

Abductor  hallucis,  stump_//; 
Insertion  of  tibialis  posti 


Insertion  of  tibialis  anticus 
Tendon  of  flexor  longus  hall 


Peroneus  longus 

Fibula 

Posterior  inf.  tibio-fibular  ligament 

Tendo  Achillis,  stump 


Inner  tubercle  of  os  calcis 

Outer  tubercle  of  os  calcis 

Flexor  brevis  digitorum,  stump 

Flexor  longus  digitorum  tendon 
Flexor  accessorius 
Abductor  minimi  digiti 


Deep  dissection  of  right  leg;  flexors  have  been  turned  aside  to  expose  tibial 


connections  between  its  tendon  and  that  of  the  flexor  longus  digitorum  being;  indications  of  its 
developmental  history. 


654 


HUMAN    ANATOMY. 


{cc)   The  Deep  Layer. 

i.   Tibialis  posticus.  2.    Flexor  accessorius. 

3.    Popliteus. 


1.  Tibialis  Posticus  (Fig.   621). 

Attachments. — The  posterior  tibial  (m.  tibialis  posterior)  arises  from  the  pos- 
terior surface  of  the  interosseous  membrane  and  from  the  adjacent  surface  of  both 
the  tibia  and  fibula.  Its  fibres  pass  into  a  tendon,  situated  along  its  inner  border, 
which  passes  obliquely  downward  and  inward  beneath  the  flexor  longus  digitorum. 
It  is  continued  onward  beneath  the  most  central  portion  of  the  internal  annular  liga- 
ment to  the  plantar  surface  of  the  foot,  where  it  is  inserted  into  the  tuberosity  of  the 
scaphoid  bone,  sending  prolongations  to  all  the  other  tarsal  bones,  except  the  astra- 
galus, and  to  the  bases  of  the  second,  third,  and  fourth  metatarsals. 

Nerve-Supply. — By  the  posterior  tibial  nerve  from  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves. 

Action. — To  extend  the  foot  and  to  slightly  invert  the  sole. 
Relations. — The  posterior  tibial  is  the  deepest  muscle  upon  the  posterior  sur- 
face of  the  leg.  It  is  covered  by  the  soleus  and  by  the  flexor  longus  digitorum,  and 
has  resting  upon  it  the  upper  portion  of  the  posterior  tibial  and  peroneal  vessels  (Fig. 
617).  The  anterior  tibial  vessels  pass  through  the  interosseous  membrane  immedi- 
ately above  the  origin  of  the  muscle.      A  bursa  sometimes  intervenes  between  its 

tendon  and  the  tuberosity  of 
Fig.  622.  the  scaphoid  bone,    and   the 

tendon  usually  contains  a  ses- 
amoid cartilage  or  bone  where 
it  passes  over  the  head  of  the 
astragalus. 

Variations. — A  portion  of  the 
muscle  is  sometimes  inserted  into 
the  internal  annular  ligament. 

A  muscle,  which  has  been 
called  the  peroneo-tibialis,  not  in- 
frequently extends  across  between 
the  fibula  and  tibia,  immediately 
beneath  the  tibio-fibular  articula- 
tion and  above  the  anterior  tibial 
vessels  as  they  pass  towards  the 
front  of  the  leg.  It  is  usually  ru- 
dimentary, but  may  form  a  well- 
marked  triangular  sheet. 


Vastus  extern  us 


I'V^Cut  edge  of  capsul; 
\]/        ligament 


fa — lateral  ligament 
Short  external 
lateral  ligament 


rface  of  femur 
dyle 


Interosseous  membr 


Deep  dissection  of  le 


ng  popliteus  muscle. 


2.   Flexor  Accessorius 
(Fig.  628). 

Attachments. — The  ac- 
cessory flexor  of  the  toes  (m. 
quadratus  plantae)  arises  by  two  heads  from  the  medial  and  inferior  surfaces  of  the 
calcaneum  and,  passing  distally,  is  i?iserted  into  the  tendon  of  the  flexor  longus 
digitorum. 

Nerve-Supply. — By  the  external  plantar  nerve  from  the  first  and  second  sacral 
nerves. 

Action. — By  acting  on  the  long  flexor  tendons,  to  flex  the  second,  third,  fourth, 
and  fifth  toes,  and  to  counteract  the  oblique  pull  of  the  long  flexor. 

The  flexor  accessorius,  although  apparently  located  entirely  in  the  foot,  is,  nevertheless,  a 
crural  muscle,  since  the  tendon  of  the  flexor  longus  digitorum,  into  which  it  is  inserted,  repre- 
sents, as  has  already  been  pointed  out,  a  portion  of  the  plantar  aponeurosis.  Into  this  many 
of  the  muscles  of  the  leg  were  primarily  inserted,  and  the  accessorius  represents  the  most  distal 
portion  of  the  original  deep  sheet  of  the  crural  musculature. 


THE   CRURAL   MUSCLES.  655 

3.    Popliteus   (Fig.   622). 

Attachments. — The  popliteus  arises  by  a  narrow  tendon  from  the  outer  con- 
dyle of  the  femur  and  by  a  slip  from  the  posterior  ligament  of  the  knee-joint.  It 
passes  inward  and  downward  to  be  inserted  into  the  posterior  surface  of  the  tibia 
above  the  oblique  line. 

Nerve-Supply. — By  the  internal  popliteal  (tibial)  division  of  the  greater  sciatic 
nerve  from  the  fifth  lumbar  and  first  sacral  nerves. 

Action. — To  flex  the  leg  and  rotate  it  inward. 

Relations. — On  its  posterior  surface  it  is  covered  by  the  plantaris  and  gas- 
trocnemius, and  it  is  crossed  by  the  popliteal  vessels  and  internal  popliteal  nerve. 
By  its  deep  surface  it  is  in  relation  to  the  capsule  of  the  knee-joint,  a  bursa  (bursa  in. 
poplitei)  intervening. 

Variations. — The  most  frequent  anomaly  in  connection  with  the  popliteus  is  the  occurrence 
of  a  second  head,  which  arises  from  the  sesamoid  cartilage  of  the  lateral  head  of  the  gastroc- 
nemius.    The  occurrence  of  this  head  is  frequently  associated  with  the  absence  of  the  plantaris. 

(*)    THE  POST-AXIAL  MUSCLES. 

1.  Tibialis  anticus.  4.    Extensor  longus  hallucis. 

2.  Extensor  longus  digitorum.  5.    Peroneus  longus. 

3.  Peroneus  tertius.  6.    Peroneus  brevis. 

Tibialis  Anticus  (Fig.  623). 

Attachments. — The  anterior  tibial  muscle  (m.  tibialis  anterior)  arises  from  the 
outer  tuberosity  and  surface  of  the  tibia  and  also  from  the  interosseous  membrane 
and  the  crural  fascia.  Its  fibres  extend  downward  to  a  strong  tendon  which  passes 
through  the  inner  compartment  of  the  anterior  annular  ligament  and  is  inserted 
into  the  inner  surface  of  the  internal  cuneiform  and  the  base  of  the  first  metatarsal 
bone. 

Nerve-Supply. — By  the  anterior  tibial  nerve  from  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves. 

Action. — -To  flex  the  foot  ;  to  draw  up  the  inner  border  and  hence  invert  the 
sole. 

Relations. — The  anterior  tibial  rests  upon  the  lateral  surface  of  the  tibia  and 
upon  the  interosseous  membrane,  and  is  in  contact  externally  with  the  extensor 
longus  digitorum,  the  extensor  longus  hallucis,  and  the  anterior  tibia]  vessels  and 
nerve  (Fig.  617).  A  bursa  (bursa  subtendinea  m.  tibialis  anterioris)  intervenes 
between  its  tendon  and  the  medial  cuneiform  bone. 

Variations. — Not  infrequently  a  bundle  is  detached  from  the  muscle  to  be  inserted  into  the 
anterior  annular  ligament,  into  the  dorsal  fascia  of  the  foot,  or,  in  some  cases,  into  the  astragalus. 
It  forms  what  has  been  termed  the  tibio-fascialis  anterior  or  tibio-astragalus. 

2.    Extensor  Longus  Digitorum  (Fig.  623). 

Attachments. — The  long  extensor. of  the  toes  (m.  extensor  digitorum  longus) 
arises  from  the  external  condyle  of  the  tibia,  the  upper  part  of  the  fibula,  the  in- 
terosseous membrane,  the  intermuscular  septum,  and  the  crural  fascia.  Its  fibres 
pass  downward  and  terminate  at  about  the  middle  of  the  leg  in  a  tendon  which  passes 
through  the  outer  compartment  of  the  anterior  annular  ligament  and  divides  into  four 
tendons  which  pass  to  the  second,  third,  fourth,  and  fifth  toes.  Over  the  metatarso- 
phalangeal joint  of  its  digit  each  tendon  spreads  out  into  a  membranous  expansion 
which  covers  the  dorsum  of  the  first  phalanx  and  receives  the  insertions  of  the  inter- 
os'sei  and  lumbricales,  and,  in  the  case  of  the  second,  third,  and  fourth  toes,  those  of 
the  extensor  brevis  digitorum.  Distally  each  membranous  expansion  divides  into 
three  slips,  of  which  the  middle  one  is  inserted  into  the  second  phalanx  and  the 
lateral  ones  into  the  third  phalanx  of  its  digit. 

Nerve-Supply. — From  the  anterior  tibial  nerve  from  the  fourth  and  fifth  lum- 
bar and  first  sacral  nerves. 

Action. — To  extend  the  second,  third,  fourth,  and  fifth  toes  and  to  flex  the  foot. 


656 


HUMAN   ANATOMY. 


Relations. — By  its  deep  surface  and  medially  the  muscle  is  in  relation  with 
the  extensor  longus  hallucis,  medially  with  the  tibialis  anticus,  the  anterior  tibial  ves- 
sels and  nerve,  and  deeply  with  the 
deep  peroneal  nerve  above  and  the 
ankle-joint  below.  Laterally  it  is  in 
contact  with  the  peroneus  longus 
above,  with  the  peroneus  tertius  be- 
low, and  with  the  musculo-cutaneous 
nerve,  which  passes  downward  be- 
tween it  and  the  peroneus  longus 
(Fig.  617). 


Variations. — Considerable  variation 
occurs  in  the  arrangement  of  the  terminal 
tendons,  one  of  the  most  usual  departures 
from  the  typical  condition  being  a  duplica- 
tion of  the  tendon  to  one  or  more  of  the 
toes,  the  additional  tendon  either  passing 
to  the  same  digit  as  its  fellow  or  to  an 
adjacent  one.  Occasionally  a  slip  passes 
from  the  innermost  tendon  to  that  of  the 
extensor  longus  hallucis,  and  slips  may 
pass  from  any  of  the  tendons  to  the  meta- 
tarsal bones. 

3.   Peroneus  Tertius   (Fig.  623). 

Attachments. — The  peroneus 
tertius  arises  from  the  lower  part  of 
the  anterior  surface  of  the  fibula  and 
from  the  interosseous  membrane,  the 
intermuscular  septum,  and  the  crural 
fascia.  At  about  the  level  of  the 
ankle  its  fibres  pass  over  into  a  ten- 
don which  continues  through  the 
lateral  compartment  of  the  anterior 
annular  ligament,  together  "with  the 
tendon  of  the  extensor  longus  digi-' 
torum,  and  is  inserted  into  the  base 
of  the  fifth  metatarsal  bone. 

Nerve-Supply. — By  the  ante- 
rior tibial  nerve  from  the  fourth  and 
fifth  lumbar  and  first  sacral  nerves. 

Action. — To  flex  and  evert  the 
foot.    • 

Variations. — The  peroneus  tertius  is 
quite  frequently  absent,  and  is  usually  more 
or  less  closely  united  with  the  extensor 
longus  digitorum  above.  Its  tendon  some- 
times splits  into  two  portions,  the  additional 
one  passing  either  to  the  fifth  toe  or  to  the 
fourth  metatarsal. 

Notwithstanding  its  name,  which  has 
reference  to  its  origin  from  the  fibula, 
the  peroneus  tertius  has  morphologically 
nothing  to  do  with  the  other  peroneal 
muscles,  but  is  a  separated  portion  of  the 
extensor  longus  digitorum,  whose  connec- 
tions with  the  metatarsals  are  interesting 
in  this  regard. 

4.    Extensor  Longus  Hallucis  (Fig.  624). 
Attachments. — The  long  or  proper  extensor  of  the  great  toe  (m.  extensor  hallucis 
longus)  arises  from  the  inner  surface  of  the  fibula  and  from  the  interosseous  membrane. 


THE   CRURAL   MUSCLES. 


657 


Outer  tuberos- 
ity of  tibia 
Head  of  fibula 


Tubercle  of  tibia 


Calf  muscles 


Tibialis  anticus 


Its  fibres  are  collected  into  a  tendon  which  passes  through  the  middle  compartment 
of  the  anterior  annular  ligament  and  is  continued  distally  to  the  great  toe.  Over  the 
metatarso-phalangeal    joint 

it  spreads  out  into  a  mem-  Fig.  624. 

branous  expansion  which 
receives  a  tendon  of  the 
extensor  brevis  digitorum 
and  is  then  continued  dis- 
tally to  be  inserted  into  the 
first  and  second  phalanges. 

Nerve-Supply. —  By 
the  anterior  tibial  nervefrom 
the  fourth  and  fifth  lumbar 
and  first  sacral  nerves. 

Action. — To  extend 
the  greattoeandflexthefoot. 

Relations. — The  ex- 
tensor longus  hallucis  is  cov- 
ered in  its  upper  part  by 
the  tibialis  anticus  and  the 
extensor  longus  digitorum. 
Near  the  ankle  it  crosses 
obliquely  over  the  anterior 
tibial  artery  and  passes  upon 
the  foot  between  the  ten- 
dons of  the  extensor  longus 
digitorum  and  the  tibialis 
anticus,  internal  to  the  ar- 
teria  dorsalis  pedis. 

Variations. — The  muscle 
is  occasionally  inserted  at  its 
origin  with  the  extensor  longus 
digitorum,  and,  in  addition  to 
the  connections  which  may  ex- 
ist between  its  tendon  and  that 
of  the  long  extensor,  it  may  also 
be  connected  with  one  of  the 
tendons  of  the  extensor  brevis 
digitorum. 

A  small  muscle  is  some- 
times to  be  found  passing  down- 
ward alongside  of  the  extensor 
brevis  hallucis  to  be  inserted 
into  the  base  of  the  first  meta- 
tarsal. It  may  be  termed  the 
abductor  longus  hallucis,  and 
takes  its  origin  either  from  the 
fibula  close  to  the  origin  of 
the  extensor  longus  hallucis,  or 
from  that  muscle,  or  from  the 
extensor  longus  digitorum  or 
the  tibialis  anticus. 

What  has  been  termed  an 
extensor  brevis  hallucis  is  fre- 
quently represented  by  a  slip 
from  the  extensor  longus  hal- 
lucis, the  extensor  longus  digi- 
torum, or  even  from  the  tibialis 
anticus  inserting  into  the  base  of 
the  first  phalanx  of  the  hallux. 

5.    Peroneus  Longus  (Figs.  625,  629). 
Attachments. — The  peroneus  longus  arises  from  the  upper  part  of  the  lateral 
surface  of  the  fibula  and  from  the  intermuscular  septa  and  crural  fascia. 

42 


Its  fibres 


658 


HUMAN    ANATOMY. 


extend  obliquely  downward  to  a  tendon  which  passes  behind  the  outer  malleolus  and 

then  runs  forward  in  a  groove  on  the 
Fig.  625.  calcaneum,    in    which    it    is    held    by- 

fibrous  bands  (retinacula  mm.  pero- 
naeorum).  On  the  cuboid  it  again 
changes  its  direction,  passing  upon 
the  plantar  surface  of  the  foot  in  a 
groove  upon  that  bone  which  is  cov- 
ered in  by  the  long  plantar  liga- 
ment, and  then,  running  obliquely 
across  the  foot,  it  is  inserted  into  the 
internal  cuneiform  and  the  base  of 
the  first  metatarsal  bone.  In  front 
of  the  tuberosity  of  the  cuboid  the 
tendon  usually  contains  a  sesamoid 
cartilage. 

Nerve-Supply. — By  the  mus- 
culocutaneous nerve  from  the  fourth 
and  fifth  lumbar  and  first  sacral  nerves. 

Action. — To  extend  the  foot  and 
evert  the  sole. 

Relations. — The  peroneus  lon- 
gus  occupies  the  lateral  surface  of  the 
leg  (Fig.  617).  It  is  in  contact  pos- 
teriorly with  the  soleus  and  internally 
with  the  extensor  longus  digitorum, 
being  separated  from  these  muscles  by 
the  intermuscular  septa.  The  musculo- 
cutaneous nerve  passes  through  the 
substance  of  the  upper  part  of  the  mus- 
cle and  is  continued  downward  between 
the  peroneus  longus  and  the  extensor 
longus  digitorum.  In  the  foot  the  ten- 
don of  the  peroneus  longus  is  deeply 
placed,  resting  directly  upon  the  plan- 
tar surfaces  of  the  cuboid,  the  external 
cuneiform,  and  the  bases  of  the  second 
and  third  metatarsal  bones. 

,.   Peroneus  Brevis  (Fi°\  624). 

-Peroneus  tertius 

Attachments. — The    peroneus 
brevis  lies  beneath  the  peroneus  lon- 
gus and  arises  from  the  lower  portion 
of    the   lateral    surface    of    the    fibula 
and  from  the  intermuscular  septa.    Its 
fibres  join  a  tendon  which 
passes  behind  the  external 
malleolus    and    then    dis- 
tally,  along  with  the  ten- 
don of  the  peroneus  lon- 
gus, beneath    the   fibrous 
bands  or  retinacula  to  be 
inserted  into  the  tuberos- 
ity of  the  fifth  metatarsal 

al  dissection  of  right  leg.  antero-lateral  aspect,                                    '                 o            i  r> 

showing  peroneal  muscles.  N  erve-Supply. by 

the      musculo  -  cutaneous 
nerve  from  the  fourth  and  fifth  lumbar  and  first  sacral  nerves. 


THE    MUSCLES    OF   THE    FOOT. 


659 


Action. — To  extend  and  evert  the  foot. 

Variations. — A  slip  is  very  frequently  given  off  from  the  tendon  of  the  short  peroneus 
which  is  inserted  either  into  the  tendon  of  the  extensor  longus  digitorum  passing  to  the  fifth  toe 
or  directly  into  that  digit.  In  some  cases  the  slip  arises  from  the  belly  of  the  muscle,  from  that 
of  the  peroneus  longus,  or  even  from  the  fibula  directly,  and  represents  what  has  been  termed 
the  peroneus  quintus. 

Kperoneus guartus,  where  distinctness  from  the  quintus  seems  doubtful,  sometimes  occurs  as 
a  muscle  arising  from  the  lower  part  of  the  fibula  and  inserting  into  the  calcaneum  or  the  tuber- 
osity of  the  cuboid. 

THE    MUSCLES    OF    THE    FOOT. 

The  plantar  fascia  or  aponeurosis  (  Fig.  626)  is  a  dense  sheet  of  connective 
tissue  lying  immediately  beneath  the  skin  of  the  plantar  surface  of  the  foot  and 
covering:  the  pre-axial  mus- 


cles. It  is  attached  behind 
to  the  tuberosity  of  the  cal- 
caneum, and  extends  dis- 
tally  in  a  fan-like  manner  to 
be  attached  by  five  processes 
to  the  skin  over  the  meta- 
tarso-phalangeal  joints  of 
the  digits.  The  aponeuro- 
sis is  much  thicker  in  its 
middle  portion  than  at  the 
sides,  where  it  is  continued 
dorsally  over  the  sides  of 
the  foot  to  become  continu- 
ous with  the  fascia  of  the  dor- 
sum of  the  foot  and  with  the 
crural  fascia.  Between  its 
cutaneous  insertions  trans- 
verse bands  of  fibres  stretch 
across  to  form  the  super- 
ficial transverse  metatarsal 
ligament  (fasciculi  trans- 
versi ) ;  from  its  deep  sur- 
face strong  sheets  are  given 
off  which  pass  to  the  sheaths 
of  the  flexor  tendons.  Ex- 
pansions are  also  given  off 
from  its  deep  surface  which 
invest  the  flexor  brevis  digi- 
torum and,  on  either  side, 
the  abductor  hallucis  and 
abductor  minimi  digiti. 

Between  the  aponeu- 
rosis and  the  integument 
over  the  inferior  surface  of 
the  tuberosity  of  the  calca- 
neum a  bursa  ( bursa  subcu- 
tanea  calcanea  )  is  constantly 
present. 

The   dorsal   surface   of 


Fig.  626. 


Superficial  dissection  of  sol 
on  belly),  sh 


of  right  foot  (subject  ly 
\  plantar  fascia. 


the  foot  is  covered  by  the  fascia  dorsalis  pedis,  a  rather  thin  sheet  continuous  with 
the  crural  fascia  above.      It  covers  the  long:  extensor  tendons. 


(a)   THE  PRE-AXIAL  MUSCLES. 
Like  the  pre-axial  muscles  of  the  hand,  those  of  the  foot  may  be  regarded  as 
derived  from  five  primary  layers,  which  have  undergone  a  considerable  amount  of 
modification,  including  some  fusion. 


66o 


HUMAN   ANATOMY. 


(aa)   The  Muscles  of  the  First  Layer. 
Flexor  brevis  digitorum.  3.   Abductor  hallucis. 

4.   Abductor  minimi  digiti. 


2.    Flexor  brevis  hallucis. 


1.    Flexor  Brevis  Digitorum  (Fig.  627). 
Attachments. — The  short  flexor  of  the  toes  (m.  flexor  digitorum  brevis)  arises 
from  the  inner  process  of  the  calcaneal  tuberosity  and  from  the  plantar  aponeurosis. 
It  extends  distally,  beneath  the  aponeurosis,   as  a  thick  quadrangular  muscle,   the 

fibres  of  which  are  collected 


Fig.  627. 


Abductor  hallucis 


Superficial  muscles  of  sole  of  right  foot. 


over  the  metatarsal  bones 
into  four  tendons  which  pass 
to  the  second,  third,  fourth, 
and  fifth  toes.  Over  the 
first  phalanx  of  the  toe  each 
tendon  divides  into  two  ter- 
minal slips,  between  which 
the  corresponding  tendon  of 
the  flexor  longus  digitorum 
passes  and  which  are  in- 
setted into  the  second  pha- 
lanx. 

Nerve-Supply. —  By 
the  internal  plantar  nerve 
from  the  fourth  and  fifth 
lumbar  and  first  sacral 
nerves. 

Action. — To  flex  the 
second,    third,    fourth,    and 

Flexor  brevis         fifth  toes. 


Variations. — The  most  fre- 
quent variation  in  this  muscle  is 
the  absence  of  the  tendon  to 
the  fifth  toe,  an  absence  which 
occurs  in  somewhat  over  21  per 
cent,  of  cases  examined.  Some- 
times the  tendon  is  replaced  by 
a  slip  or  muscle  which  arises 
from  the  tendon  of  the  flexor 
longus  digitorum. 

The  flexor  brevis  repre- 
sents the  middle  portion  of  the 
superficial  flexor  layer,  and  cor- 
responds, accordingly,  to  the 
terminal  portions  of  the  ten- 
dons of  the  flexor  sublimis  of 
the  hand.  Its  origin  is  primarily 
from  the  plantar  aponeurosis, 
and  hence  the  occasional  origin 
of  the  portion  for  the  fifth  toe 
becomes  intelligible,  since  the 
tendon  of  the  flexor  longus  is 
a  differentiation  of  the  deeper 
layer  of  the  aponeurosis. 


2.    Flexor  Brevis  Hallucis  (Fig.  628). 

Attachments. — The  short  flexor  of  the  great  toe  (m.  flexor  hallucis  brevis) 
arises  from  the  plantar  surface  of  the  internal  cuneiform  bone  and  the  adjacent  liga- 
mentous structures.  Its  fibres  pass  distally  to  a  tendon  which  contains  a  sesamoid 
bone,  and  is  i?iserted  into  the  inner  surface  of  the  base  of  the  first  phalanx  of  the 
great  toe. 

Nerve-Supply. — By  the  internal  plantar  nerve  from  the  fourth  lumbar  nerve. 

Action. — To  flex  the  great  toe. 


THE    MUSCLES    OF    THE    FOOT. 


66 1 


Variations. — The  flexor  brevis  hallucis  is  frequently  intimately  fused  with  the  abductor 
hallucis. 

A  portion  of  the  deeper  fibres  of  the  flexor  brevis  hallucis  is  frequently  inserted  into  the 
whole  length  of  the  first  metatarsal.  Occasionally  these  fibres  are  quite  distinct  from  the  rest 
of  the  muscle,  forming  what  has  been  termed  an  opponens  hallucis. 

In  the  description  of  the  muscle  given  above,  account  has  been  taken  only  of  what  is  usually 
described  as  the  inner  portion,  the  flexor  brevis  pollicis  being  usually  regarded  as  consisting 
of  two  bellies,  the  second  of  which  is  inserted  into  the  lateral  side  of  the  base  of  the  first 
phalanx  of  the  great  toe.  The  relations  of  this  outer  belly  and  its  nerve-supply,  however,  indi- 
cate that  it  belongs  to  an  entirely  different  layer  than  the  medial  belly.  It  will,  therefore,  be 
considered  later  in  connection  with  the  interossei  (page  663). 


Fig.  62S. 


Os  calcis,  outer  tubercle 


Abductor  hallucis,  JZ. 
calcaneal  origin        |j 
Internal  annular  ligament 

or  brevis  digitorum,  origin 

=xor  longus  hallucis  tendon 

Tibialis  posticus  tendon' 

Flexor  longus  digitorum  tend- 

Abductor  hallucis,  part  of  origin 


Abductor  halluci 


First  plantar  interosseus 
Flexor  brevis  hallucis 


Flexor  longus  hallucis  tendon 


r  brevis  digitorum 
■  longus  digitorum 


Long  and  accessory  fl 


digiti,  origin 


Long  plantar  ligament 


Peroneus  longus  tendon 

Abductor  minimi  digiti,  occasional 
insertion  (Abductor  ossis  metatarsi 
quinti) 


Flexor  accessorius 
Tubercle  of  fifth  metatarsus 
Flexor  brevis  minimi  digiti, 
part  of  its  origin 

Flexor  longus  digitorum 


nimi  digiti 


i  digiti, 


posed  by 


al  of  superficial  muscle 


3.    Abductor  Hallucis  (Fig.  627). 

Attachments. — The  abductor  hallucis  extends  along  the  inner  border  of  the 
foot,  arising  from  the  inner  tubercle  and  surface  of  the  calcaneum  and  from  the 
plantar  aponeurosis  and  being  inserted,  along  with  the  flexor  brevis  hallucis,  into  the 
inner  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

Nerve-Supply. — By  the  internal  plantar  nerve  from  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves. 

Action.— To  abduct  and  flex  the  hallux. 


662  HUMAN    ANATOMY. 

Abductor  Minimi  Digiti  (Fig.   627). 

Attachments. — The  abductor  of  the  little  toe  (m.  abductor  digiti  quinti)  is 
situated  along  the  outer  border  of  the  foot.  It  arises  from  the  under  surface  of  the 
calcaneum  and  from  the  plantar  aponeurosis,  and  extends  distally  and  laterally  to  be 
i?iserted  partly  into  the  tuberosity  of  the  fifth  metatarsal  bone  and  partly  into  the 
lateral  side  of  the  base  of  the  first  phalanx  of  the  little  toe. 

Nerve-Supply. — By  the  external  plantar  nerve  from  the  first  and  second 
sacral  nerves. 

Action. — To  abduct  and  flex  the  little  toe. 

Variations — A  portion  of  the  abductor  digiti  quinti  frequently  separates  from  the  rest  of 
the  muscle  to  form  a  fusiform  belly  which  has  been  termed  the  abductor  ossis  metatarsi  quinti. 
It  arises  from  the  lateral  part  of  the  inferior  surface  of  the  os  calcis  and  is  inserted,  either  inde- 
pendently or  in  common  with  the  abductor,  into  the  tuberosity  of  the  fifth  metatarsal. 

(bb)   The  Muscles  of  the  Second  Layer. 
I.      LUMBRICALES    (Fig.    628). 

Attachments. — -The  lumbricales  are  four  spindle-shaped  muscles  which  arise 
from  the  adjacent  borders  of  the  tendons  of  the.  flexor  longus  digitorum  and  from  the 
inner  border  of  its  first  tendon.  They  pass  distally  to  the  inner  surfaces  of  the  first 
phalanges  of  the  second,  third,  fourth,  and  fifth  digits,  where  they  are  i?iserted  into  the 
membranous  expansions  of  the  tendons  of  the  extensor  longus  digitorum. 

Nerve-Supply. — The  first  or  first  and  second  muscles,  counting  from  the  tibial 
side,  are  supplied  by  the  internal  plantar  nerve  ;  the  remaining  three  or  two  are  sup- 
plied from  the  external  plantar  from  the  fourth  and  fifth  lumbar  and  first  sacral  nerves. 

Action. — To  flex  and  draw  medially  the  second,  third,  fourth,  and  fifth  toes. 

Variations. — Absence  of  one  or  other  of  the  lumbricales  has  been  noted,  the  fourth  and  third 
being  those  most  frequently  lacking  ;  these  same  muscles  are  frequently  bifid  at  their  insertions. 
Small  bursse  may  intervene  between  the  tendons  and  the  first  phalanges. 

The  significance  of  the  lumbricales  is  similar  to  that  of  the  corresponding  muscles  of  the 
hand.  They  arise  primarily  from  the  deeper  layers  of  the  plantar  aponeurosis,  and  when  these 
differentiate  into  the  tendons  of  the  flexor  longus  digitorum  they  come  to  arise  from  those 
structures. 

(cc)    The  Muscles  of  the  Third  Layer. 

1.    Adductor  Hallucis  (Fig.  629). 

Attachments. — The  adductor  hallucis  consists  of  two  portions,  often  described 
as  two  distinct  muscles,  united  only  at  their  insertions.  The  oblique  portion  (caput 
obliquum),  or  adductor  obliquus,  arises  from  the  bases  of  the  second,  third,  and 
fourth  metatarsals  and  from  the  long  plantar  ligament  and  passes  distally  and  inward 
along  the  interval  between  the  first  and  second  metatarsals,  its  fibres  converging  to  a 
strong  tendon  which  unites  with  that  of  the  transverse  portion  (caput  transversum),  or 
adductor  transversus.  This  extends  almost  transversely,  under  cover  of  the  three 
medial  tendons  of  the  long  and  short  flexors  and  the  lumbricales,  over  the  heads  of 
the  fourth,  third,  and  second  metatarsals.  It  arises  from  the  capsules  of  the  four 
lateral  metatarso-phalangeal  joints  and  passes  medially  to  join  the  tendon  of  the 
oblique  portion.  The  common  tendon  so  formed  unites  with  the  tendon  of  the  first 
plantar  interosseous  and  is  inserted  into  the  sesamoid  bone  of  that  tendon  and  into  the 
lateral  surface  of  the  base  of  the  first  phalanx  of  the  great  toe. 

Nerve-Supply. — By  the  deep  branch  of  the  external  plantar  nerve  from  the 
fifth  lumbar  and  first  and  second  sacral  nerves. 

Action. — To  flex  and  adduct  the  hallux. 

Variations.— Some  variation  occurs  in  the  extent  of  the  origin  of  both  portions  of  the 
adductor  hallucis.  The  oblique  portion  may  be  limited  to  the  long  plantar  ligament,  or  may 
receive  an  accessory  slip  from  the  shaft  of  the  second  metatarsal,  while  the  origin  of  the  trans- 
verse portion  from  the  fifth  metatarso-phalangeal  joint  may  be  lacking. 

It  is  to  be  noted  that  in  the  foetus  the  two  portions  of  the  adductor  are  not  separated  by  a 
wide  interval  as  in  the  adult,  but  lie  in  contact  with  each  other. 


THE    MUSCLES    OF   THE    FOOT. 


663 


A  small  muscular  slip  has  occasionally  been  observed  passing  from  the  long  plantar  liga- 
ment to  the  lateral  surface  of  the  base  of  the  first  phalanx  of  the  second  toe.  It  appears  to 
represent  an  adductor  secundi  digiti. 

Fig.  629. 


Os  calcis,  outer  tubercle 


Os  calcis,  inner  tubercl 
Flexor  brevis  digiti 
Flexor  longus  hallucis  tend 


Flexor  longus  hallucis  tend' 


{dd )    The  Muscles  of  the  Fourth  and  Fifth  Layers. 

I.    Interossei  plantares.  2.    Interossei  dorsales. 

3.    Flexor  brevis  minimi  digiti. 

As  in  the  hand,  the  fourth  and  fifth  layers  of  the  pre-axial  musculature  become 
united  to  form  the  dorsal  interossei,  portions  of  the  fourth  layer  remaining  distinct  to 
form  the  plantar  interossei.  The  arrangements  in  the  hand  and  foot  differ,  however, 
in  this  respect,  that  in  the  foot  the  lateral  muscle  derived  from  the  fourth  layer  forms 
a  large,  well-developed  structure  termed  the  flexor  brevis  minimi  digiti. 

1.   Interossei  Plantares  (Fig.  630). 

Attachments. — The  plantar  interossei  are  four  spindle-shaped  muscles.  The 
first  is  very  much  stronger  than  the  others,  and  is  often  described  as  the  outer  head 
of  the  flexor  brevis  hallucis  (page  661).      It  arises,  in  common  with  the  flexor  brevis 


664 


HUMAN    ANATOMY. 


Long  plantar  ligament 


hallucis,  from  the  inner  cuneiform  bones  and  the  adjacent  ligamentous  structures. 
It  extends  distally  along  the  lateral  surface  of  the  first  metatarsal  bone  and  passes 
over  into  a  strong  tendon,  which  contains  a  sesamoid  bone,  and  is  i?iserted  into  the 
outer  surface  of  the  base  of  the  first  phalanx  of  the  great  toe,  along  with  the 
adductor  hallucis. 

The  remaining  three  muscles  are  much  smaller  and  arise  in  succession  from  the 
medial  surfaces  of  the  third,  fourth,  and  fifth  metatarsals,  and,  passing  distally,  are 

inserted  by    slender   ten- 
Fig.  630.  dons  into  the  membranous 

expansions  of  the  long  ex- 
tensor tendonsof  the  third, 
fourth,  and  fifth  toes,  on 
the  medial  sides  of  their 
first  phalanges. 

Nerve-Supply. — By 
the  external  plantar  nerve 
from  the  first  and  second 
sacral  nerves. 

Action. — To  flex  the 
first,  third,  fourth,  and  fifth 
toes  and  to  draw  the  last 
three  medially. 

Variations. — As  above 
stated,  the  first  plantar  inter- 
osseus  is  usually  described  as 
a  second  head  of  the  flexor 
brevis  hallucis.  It  is  some- 
times more  or  less  insepara- 
ble from  the  oblique  portion 
of  the  adductor  hallucis. 

2.  Interossei  Dorsales 
(Figs.  623,  630). 

Attachments. — The 

dorsal  interossei  are  also 
four  in  number.  They 
arise  from  the  adjacent 
sides  of  each  pair  of  met- 
atarsals and  pass  distally 
in  the  interspaces  between 
these  bones.  The  fibres 
of  each  muscle  converge 
to  a  narrow  tendon  which 
is  inserted  into  the  mem- 
branous expansions  of  the 
extensor  tendons  over  the 
first  phalanges  of  the  sec- 
ond, third,  and  fourth  toes. 
The  first  and  second  mus- 
cles insert  into  the  opposite  sides  of  the  second  toe  and  the  third  and  fourth  into  the 
lateral  sides  of  the  third  and  fourth  toes. 

Nerve-Supply. — By  the  external  plantar  nerve  from  the  first  and  second  sacral 
nerves. 

Action. — To  flex  the  second,  third,  and  fourth  toes  ;  the  first  also  draws  the 
second  toe  medially  and  the  rest  the  second,  third,  and  fourth  toes  laterally. 

3.   Flexor  Brevis  Minimi  Digiti  (Fig.  629). 
Attachments. — The  short  flexor  of  the  little  toe  (m.  flexor  digiti  quinti  brevis), 
which  really  represents  a  fifth  plantar  interosseus,  arises  from  the  base  of  the  fifth 


fleeted, 
ductor    and 
ductor     tend< 
showing  the  two 
sesamoid  bones 

Deep  dissection  of  sole  of  right  foot,  showing  interosseous  muscl 


PRACTICAL    CONSIDERATIONS  :    THE    LEG.  665 

metatarsal  and  passes  distally  along  the  outer  side  of  the  fourth  plantar  interosseus 
to  be  inserted  by  a  tendon  into  the  outer  surface  of  the  base  of  the  first  phalanx  of 
the  fifth  toe  and  also  into  the  distal  portion  of  the  fifth  metatarsal. 

Nerve-Supply. — From  the  external  plantar  nerve  from  the  second  sacral 
nerve. 

Action. — To  flex  the  fifth  toe  and  draw  it  lateralward. 

Variations. — The  portion  of  the  flexor  brevis  minimi  digiti  which  passes  to  the  fifth  meta- 
tarsal is  frequently  more  or  less  distinct  from  the  rest  of  the  muscle,  and  has  then  been  termed 
the  opponens  quinti  digiti. 

(b)    THE  POST-AXIAL  MUSCLES. 
1.    Extensor  Brevis  Digitorum  (Fig.  624). 

Attachments. — The  short  extensor  of  the  toes  (m.  extensor  digitorum  brevis) 
arises  from  the  lateral  and  superior  surfaces  of  the  calcaneum.  It  passes  distally 
beneath  the  tendons  of  the  extensor  longus  digitorum  and  divides  into  four  portions, 
the  outer  three  of  which  soon  become  tendinous  and  are  inserted  by  fusing  with  the 
tendons  of  the  extensor  longus  to  the  second,  third,  and  fourth  toes  over  the  first 
phalanges  of  those  toes;  the  innermost  tendon  is  inserted  into  the  base  of  the  first 
phalanx  of  the  great  toe. 

Nefve-Supply. — By  the  anterior  tibial  nerve  from  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves. 

Action. — To  extend  and  draw  laterally  the  first,  second,  third,  and  fourth  toes. 

Variations. — Occasionally  one  or  other  of  the  tendons  of  the  extensor  brevis  may  be 
doubled,  this  condition  being  most  frequent  in  the  tendon  to  the  second  toe  ;  sometimes  a  fifth 
tendon  passes  to  the  little  toe. 

The  innermost  tendon  is  nearly  always  much  stronger  than  the  others  ;  the  fibres  which 
insert  into  it  are  occasionally  separate  from  the  remainder  of  the  muscle,  then  forming  the 
extensor  brevis  hallucis. 

PRACTICAL    CONSIDERATIONS:    MUSCLES   AND    FASCIAE 
OF  THE   LEG,   ANKLE,   AND  FOOT. 

1.  The  Leg. — The  skin  over  the  leg  is  everywhere  more  adherent  to  the  un- 
derlying fascia  than  it  is  in  the  thigh.  Its  inability  at  certain  places,  as  over  the  spine 
and  antero-internal  surface  of  the  tibia,  to  glide  away  when  force  is  applied  partly 
accounts  for  the  frequency  with  which  bruising  or  laceration,  superficial  ulceration, 
or  even  periostitis  or  caries  follows  injuries  to  the  "  shin." 

The  deep  fascia  blends  with  the  periosteum  at  the  head  and  inner  and  anterior 
borders  of  the  tibia,  at  the  head  of  the  fibula,  and  at  the  two  malleoli.  It  is  thicker 
and  denser  above  and  anteriorly  than  below  and  posteriorly.  The  two  septa  (Figs. 
627,  623)  that  run  inward  from  it  on  the  outer  side  of  the  leg  and  are  attached  to  the 
anterior  and  external  borders  of  the  fibula  constitute  an  osseo-aponeurotic  space  that 
contains  the  peroneal  muscles  and  that  may,  for  a  time,  limit  the  spread  of  infection 
or  of  suppuration.  The  peronei,  in  their  compartment,  and,  farther  in,  the  bones  and 
interosseous  membrane,  separate  the  anterior  group  of  muscles — the  tibialis  anticus, 
extensor  communis,  etc. — -from  the  posterior  group.  The  fascia  over  the  anterior 
group  embraces  them  so  closely,  that  when  it  is  wounded  or  torn  the  muscle-fibres 
protrude  and  approximation  of  the  edges  of  the  fascial  wound  may  be  difficult.  In 
the  anterior  compartment  the  muscles  are  intimately  adherent  to  its  fibrous  walls,  as 
is  the  case  in  the  forearm,  but  not  in  the  arm  or  thigh  (Tillaux).  In  the  posterior 
compartment,  on  the  contrary,  a  loose  layer  of  connective  tissue  intervenes  between 
the  gastrocnemius  and  the  deep  fascia,  and  permits  the  greater  degree  of  motion 
between  the  muscle  and  the  aponeurosis  necessitated  by  the  greater  range  of  motion 
in  plantar,  as  compared  with  dorsal,  flexion  of  the  foot. 

The  difference  will  be  noted  in  dealing  with  wounds  involving  these  regions,  or 
in  some  operations,  as  amputation  of  the  leg. 

The  septum,  anteriorly,  at  the  upper  third  of  the  leg,  between  the  tibialis  anticus 
and  extensor  longus  digitorum,  is  of  variable  density,  gives  no  indication  of  its  pres- 


666 


HUMAN    ANATOMY. 


end 
upper 


ence  on  either  the  skin  or  fascial  surface,  and  although  described  as  a  guide  to  the 
anterior  tibial  artery  (q.v.),  is  untrustworthy  on  account  of  the  difficulty  of  recog- 
nizing it  (Treves). 

Posteriorly  the  deep  layer  of  fascia  that  holds  down  the  deep  muscles  to  the 
tibia  and  fibula  and  runs  transversely  beneath  the  soleusand  gastrocnemius,  is  weaker 
above,  where  it  is  covered  and  reinforced  by  the  latter 
muscles,  and  stronger  below,  where  it  loses  their  sup- 
port. It  is  continued  downward  and  separates  the 
tendo  Achillis  from  the  deeper  structures.  In  ap- 
proaching the  vessels  behind  the  malleolus,  one  finds, 
therefore,  two  layers  of  deep  fascia. 

Growths  originating  in  the  head  of  the  tibia  or 
occupying  the  interosseous  space  are  much  influenced 
by  the  resistance  of  the  deep  fascia,  which,  as  is  the 
case  with  the  fascia  lata,  may  for  a  time  determine 
their  shape  and  direction  and  alter  their  surface  ap- 
pearance and  their  apparent  density. 

Cellulitis  and  abscess  are  for  a  while  confined 
beneath  the  fascia,  but,  like  the  coloring  matter  of 
the  blood  after  fracture,  may  soon  find  their  way  to 
the  surface  by  following  the  vessels  that  perforate  it. 

Some  fibres  of  the  gastrocnemius  or,  more  fre- 
quently, the  tendo  Achillis  at  its  weakest  point,  on  a 
level  with  the  internal  malleolus,  may  be  ruptured 
during  strong  effort,  as  in  raising  the  bod)'  on  the 
toes  while  bearing  a  weight.  Sometimes,  however, 
this  accident  follows  comparatively  trifling  exertion. 

2.  The  Ankle  and  Foot. — The  skin  around 
the  ankle  and  upon  the  dorsum  of  the  foot  is  thin 
and  lax.  The  absence  of  a  fatty  or  muscular  layer 
between  it  and  the  subjacent  bones  and  the  distance 
of  the  region  from  the  centre  of  circulation  make 
gangrene  from  relatively  slight  contusion,  or  from  the 
pressure  of  splints  or  dressings,  more  common  here 
than  elsewhere. 

Over  the  sole,  especially  at  those  places  which 
normally  bear  the  weight  of  the  body, — the  heel,  the 
ball  of  the  great  toe,  the  line  of  the  heads  of  the  metatarsal  bones  (page  452),  and 
the  outer  side  of  the  foot, — the  skin  is  much  denser.  It  often  contains  callosities 
which  cause  pain  by  pressure  and  are  usually  the  result  of  friction  between  the  sole 
and  an  ill-fitting  shoe.  Its  close  connection  with  the  underlying  plantar  fascia  is 
similar  to  that  between  the  skin  of  the  palm  and  the  palmar  fascia,  and  between  the 
skin  of  the  scalp  and  the  occipito-frontalis  aponeurosis,  in  all  of  which  regions  the 
integument  is  exceptionally  thick  and  dense,  and  in  the  former  two  hairless  (page 
491).  Under  the  heel  the  thick  skin  and  the  pad  of  subcutaneous  fascia  containing 
fat  are  especially  valuable  in  lessening  the  force  of  falls  upon  that  part  of  the  foot, 
where  there  is  no  elastic  arch  composed  of  a  number  of  bones  and  joints  to  take  up 
and  distribute  the  force,  as  do  both  the  transverse  arch  and  the  anterior  pillar  of 
the  main  arch  (page  436).  This  tissue,  vertical  and  scanty  in  the  sole,  is  loose  and 
abundant  on  the  dorsum  and  around  the  tendo  Achillis,  in  which  latter  region  it 
contains  some  fat.  Its  laxity  over  the  dorsum,  while  it  somewhat  protects  the  instep 
from  the  effects  of  direct  violence,  adds  greatly  to  the  ease  with  which  swelling  or 
ced^ma  may  occur  in  cellulitis  or,  on  account  of  the  dependent  position  of  the  part 
and  its  remoteness  from  the  heart,  in  anasarca. 

The  deep  fascia  at  the  ankle  is  thickened  on  the  dorsum  and  sides  to  form  the 
annular  ligaments,  the  chief  function  of  which  is  to  hold  in  place  the  tendons  that 
move  the  foot  and  toes.  Anteriorly  this  is  done  by  two  bands,  beneath  the  upper  of 
which  the  tendon  of  the  tibialis  anticus  runs,  while  the  lower  covers  in  the  tendon  of 
the  same  muscle  and  those  of  the  extensor  proprius  pollicis  and  of  the  extensor  com- 


Dissection  of  fracture  of  left  tibi; 

showing  effect  of  muscular 

action  on  fragments. 


PRACTICAL    CONSIDERATIONS  :    ANKLE   AND    FOOT.  667 

munis  and  peroneus  tertius,  the  last  two  running  in  one  sheath.  Internally — i.e., 
between  the  heel  and  the  internal  malleolus — the  tendons  of  the  flexor  longus  pol- 
licis,  the  flexor  longus  digitorum,  and  the  tibialis  posticus  run  beneath  the  internal 
annular  ligament,  the  last  named  being  the  deepest  and  in  the  closest  proximity  to 
the  ankle-joint,  disease  of  which  may  originate  in  the  tendon.  The  relation  of  the 
flexor  longus  pollicis  tendon  to  the  posterior  ligament  is  intimate,  and  is  believed  to 
be  of  advantage  in  resisting  posterior  luxation  of   the  astragalus  (page  450). 

The  peroneus  longus  tendon  is  thought  to  be  more  frequently  displaced  than 
any  other  tendon  in  the  body.  When  this  accident  happens,  the  tendon  slips  from 
its  groove  behind  the  external  malleolus  and  over  the  thin  posterior  border  of  the 
latter  to  its  anterior  face.  This  dislocation  is  favored  by  {a)  the  length  and  slender- 
ness  of  the  tendon  ;  {b)  the  shallowness  of  the  groove  in  which  it  runs  ;  {c)  the 
relative  weakness  of  the  single  slip  of  the  external  annular  ligament  that  covers  the 
tendon;  {d)  the  fact  that  it  changes  its  direction  twice  between  the  lower  third  of  the 
leg  and  its  insertion, — i.e. ,  once  at  the  malleolus  and  once  at  the  margin  of  the  cuboid. 

Disease  of  the  sheaths  of  the  tendons  about  the  ankle-joint  is  not  rare,  is  apt  to 
be  tuberculous,  and  is  favored  by  the  frequent  strains  and  the  exposure  to  cold  and 
wet  to  which  they  are  subjected,  and  by  their  dependent  position  and  remoteness 
from  the  heart. 

Their  relation  to  disease  of  the  tarsal  bones  should  be  remembered  (page  437). 
The  approximately  vertical  direction  of  the  swelling  in  the  early  stages  is  some- 
times of  use  in  differentiating  teno-synovitis  from  ankle-joint  disease  (page  451). 

The  involvement  of  the  tendon-sheaths  in  sprain  of  the  ankle-joint  (page  450) 
adds  to  the  duration  of  the  disability  produced  by  that  accident. 

On  the  sole  of  the  foot  the  dense  plantar  fascia  is  of  importance  in  relation  to 
infection  or  suppuration  beneath  it.  Of  its  three  divisions  (page  659),  the  central 
one  is  much  the  strongest.  With  the  intermuscular  septa  that  run  from  its  lateral  bor- 
ders into  the  sole  and  separate  the  flexor  brevis  digitorum  from  the  abductor  minimi 
digiti  externally  and  from  the  abductor  hallucis  internally,  it  makes  a  compartment 
the  floor  of  which  is  rarely  penetrated  by  inflammatory  or  purulent  effusions.  An 
abscess  beginning  in  the  mid-region  of  the  sole  beneath  the  plantar  fascia  may  pass 
forward  between  the  digital  slips  or  upward  through  the  interosseous  spaces,  or 
along  the  tendon-sheaths  to  the  ankle.  More  rarely  apertures  in  the  plantar  fascia 
permit  suppuration  to  spread  through  it  to  the  subcutaneous  region  of  the  sole. 
The  abscess  cavity  then  consists  of  two  portions  connected  by  a  narrow  neck,  abces 
en  bouton  de  chemise  (Tillaux). 

The  lateral  progress  of  such  an  abscess — through  the  intermuscular  septa  above 
described — is  easier  than  penetration  of  the  strong  central  leaflet  of  the  plantar  fascia. 

It  will  be  noted  that  the  three  compartments  into  which  the  sole  is  then  divided 
are  analogous  to  the  thenar,  hypothenar,  and  central  divisions  of  the  palm.  Con- 
traction of  the  plantar  fascia,  which  aids  in  maintaining  the  curve  of  the  arch  of  the 
foot,  as  a  string  would  that  of  its  bow,  increases  that  arch,  is  often  associated  with 
the  different  forms  of  talipes,  and  is  thought  to  be  one  of  the  common  causes  of  a 
subvariety, — pes  cavns.  Relaxation  or  elongation  of  the  plantar  fascia  favors  depres- 
sion of  the  normal  arch,  and  hence  contributes  to  the  development  of  the  condition 
known  as  "flat-foot"  {pes planus)  {vide  infra). 

Club- Foot. — The  mechanics  of  the  normal  foot  have  already  been  sufficiently 
described  (pages  436,  447). 

Of  the  deformities,  either  congenital  or  acquired,  which  are  grouped  under  the 
name  club-foot,  it  is  necessary  to  describe,  from  the  anatomical  stand-point,  only  the 
chief  varieties. 

1.  Talipes  equino-varus,  when  congenital,  is  believed  to  result  from  retention 
of  the  fcetal  position, — i.e.,  from  defective  development.  The  inward  rotation  of  the 
flexed  and  crossed  limbs  in  utero,  which  in  the  later  periods  of  fcetal  life  removes  the 
pressure  from  the  fibular  side  of  the  legs  and  the  dorsum  of  the  feet  and  puts  the 
latter  in  the  position  of  extreme  flexion  with  the  soles — instead  of  the  tops — of  the 
feet  against  the  uterine  walls  (Berg),  does  not  take  place.  This  is  the  commonest 
of  all  the  forms  of  club-foot.  When  it  is  acquired,  it  may  be  due  to  paralysis  of 
those  muscles  that  oppose  the  adduction  and  extension  of  the  foot, — i.e. ,  chiefly  of 


668  HUMAN   ANATOMY. 

the  extensor  longus  digitorum  and  the  peronei.  The  muscles  that  draw  up  the  heel, 
— the  gastrocnemius  and  soleus, — the  muscles  that  elevate  the  inner  border  of  the 
foot  and  adduct  it, — the  tibalis  anticus  and  posticus  and  the  flexor  longus  digitorum, 
— are  not  resisted  ;  or,  if  the  case  is  congenital,  are  assisted  by  the  position  of  the 
foot,  which  is  therefore  found  with  {a)  the  heel  elevated  ;  (6)  the  inner  edge  of  the 
sole  drawn  upward  ;  (<r)  its  axis  turned  inward  ;  (d)  the  sole  shortened,  partly- 
through  contraction  of  the  plantar  fascia. 

In  marked  cases  the  calcaneum  will  be  almost  vertical,  as  will  the  astragalus, 
which  will  also  be  rotated  forward  so  that  its  head  may  have  two  articular  facets,  one 
of  them  projecting  on  the  dorsum;  the  scaphoid  is  atrophied  and  is  close  to  the 
inner  malleolus;  the  cuneiform  bones  accompany  it,  and  the  cuboid  becomes  the 
chief  point  of  support  of  the  weight  of  the  body. 

Corresponding  changes  occur  in  the  metatarsal  bones  and  phalanges,  which  may 
be  at  right  angles  to  the  line  of  the  inner  side  of  the  leg. 

Pure  talipes  varus,  in  which  the  elevation  of  the  heel  is  absent,  is  very  rare.  The 
other  varieties  of  club-foot  are  seldom  congenital. 

2.  Talipes  Valgus. — The  foot  is  abducted  and  the  outer  border  elevated  by  the 
peronei,  the  inner  side  being  correspondingly  depressed  and  the  arch  of  the  foot 
flattened  out. 

3.  Talipes  Equinus. — The  heel  is  drawn  up  by  the  gastrocnemius  and  soleus  ; 
the  patient  walks  on  the  balls  of  the  toes  ;  the  os  calcis  and  the  astragalus  are 
changed  in  position  as  in  equino-varus.  The  astragalo-scaphoid  and  calcaneo- 
cuboid joints  are  much  flexed,  so  that  the  scaphoid  may  even  be  in  contact  with  the 
os  calcis. 

4.  Talipes  Calcaneus. — The  extensor  longus  digitorum  and  the  extensor  pro- 
prius  pollicis  raise  the  toes  and  with  them  the  foot,  so  that  the  anterior  portion  of  the 
os  calcis  is  elevated  and  the  astragalus  is  rotated  backward  until  its  articular  sur- 
face points  in  that  direction.      The  patient  walks  on  the  heel. 

Flat-foot  results  from  weakness  or  relaxation  of  plantar  muscles,  fasciae,  and 
ligaments,  especially  the  inferior  calcaneo -scaphoid  (page  445).  When,  in  persons 
who  stand  much  of  their  time,  or  in  those  with  defective  ankles  originally,  this  liga- 
ment yields,  the  head  of  the  astragalus  is  carried  downward  and  inward  by  the  body 
weight,  which,  owing  to  the  width  of  the  pelvis,  the  obliquity  of  the  femur,  and  the 
curve  of  the  tibia,  is  transmitted  to  the  astragalus  somewhat  from  without  inward. 
This  is  associated  with  abduction  of  the  foot,  resisted  by  the  internal  lateral  and 
calcaneo-astragaloid  ligaments.  This  sinking  of  the  astragalus  and  increased  promi- 
nence of  the  internal  malleolus  may  be  seen  in  many  normal  feet  when  the  weight  of 
the  body  is  thrown  on  one  foot  (page  449).  In  well-marked  cases  of  flat-foot  the 
tibialis  posticus  fails  to  resist  this  change  effectually,  the  peronei  add  to  the  abduction 
or  shortening,  the  arch  of  the  sole  of  the  foot  entirely  disappears  or  may  even  become 
a  rounded  downward  curve,  the  deltoid  ligament  stretches,  as  do  the  long  and  short 
plantar  ligaments,  and  the  head  of  the  astragalus,  the  scaphoid  tubercle,  and  the 
sustentaculum  tali  (page  449)  become  unduly  prominent  and  may  be  the  main  points 
of  support. 

Two  bursae  about  the  foot  are  of  enough  importance  to  demand  attention. 

The  retrocalcaneal  bursa  lies  between  the  os  calcis  and  the  tendo  Achillis,  the 
depressions  at  the  sides  of  which  are  effaced  when  the  bursa  is  distended.  The  cor- 
responding obliteration  of  the  anterior  depressions  just  beneath  the  malleoli  (page 
451),  which  occurs  in  ankle-joint  disease,  does  not  take  place.  Flexion  or  extension 
of  the  foot  or  contraction  of  the  calf  muscles  is  painful. 

Bunions. — There  may  be  normally  a  bursa  over  the  metatarso-phalangeal  joint 
of  the  great  toe,  or  an  "adventitious"  bursa — formed  by  dilatation  of  lymph-spaces, 
condensation  of  connective  tissue,  and  localized  effusion — may  develop  there,  as  a 
result  of  pressure  and  friction  from  badly  fitting  shoes.  The  great  toe  is  forced  out- 
ward, the  internal  lateral  ligament  of  the  articulation  is  elongated,  the  joint  is  made 
unduly  prominent,  the  head  of  the  first  metatarsal  bone  sometimes  enlarges,  and  the 
cartilage  over  its  inner  surface  not  uncommonly  atrophies  and  disappears^  leaving  a 
communication  between  the  bursal  sac  and  the  synovial  cavity  of  the  joint.  _  Flat- 
foot  and  all  degrees  of  valgus  tend  to  produce  a  similar  condition  by  exposing  the 


SURFACE    LANDMARKS:    THE    LOWER    EXTREMITY. 


669 


inner  border  of  the  foot — and  thus  the  first  metatarsophalangeal  joint — to  excessive 
pressure. 

Adventitious  bursae  are  found  over  the  external  malleolus, — "tailor's  bursa,"  — 
over  the  cuboid  in  equino-varus,  and  at  other  points  exposed  to  pressure  in  the 
different  forms  of  club-foot. 


. Crest  of  i  1  i  1 


SURFACE    LANDMARKS    OF    THE    LOWER    EXTREMITY. 

1.  The  Buttocks  and  Hip. — The  iliac  furrow  (page  349)  indicating  the  line 
of  the  crest  of  the  ilium,  with  the  external  oblique  above  and  the  gluteus  medius 
below,  passes  forward  to  the  anterior 

superior  spine,    and    is    more    or  less  Fig.  632. 

effaced  posteriorly  where  the  crest  is 
covered  by  the  flat  tendon  of  the  erec- 
tor spinse.  The  posterior  superior 
spine  is  always  indicated  by  a  surface 
depression. 

In  women  the  continuous  layer  of 
fat  passing  from  the  loin  to  the  but- 
tock blends  the  surface  forms  of  these 
regions  into  one  uniform  curve  (Thom- 
son), and  there  is  no  such  marked  defi- 
nition of  them  as  is  seen  in  the  male. 

The  rounded  prominence  of  the 
buttock  (Fig.  632)  is  due  partly  to 
subcutaneous  fat,  partly  to  the  thick 
muscular  mass  of  the  gluteus  maximus, 
especially  developed  in  man  by  reason 
of  his  assumption  of  the  upright  po- 
sition. It  is  more  prominent  posteri- 
orly, becomes  flattened  as  it  passes 
outward,  and  ends  in  a  distinct  de- 
pression (Fig.  632)  at  the  tendinous 
insertion  of  that  muscle  just  behind 
and  below  the  greater  trochanter.  Al- 
though the  trochanter  is  on  a  plane 
external  to  that  of  the  iliac  crest,  the 
hollow  between  it  and  the  ilium  is  so 
obliterated  by  the  gluteus  medius  and 
minimus  muscles  that  it  ordinarily  does 
not  appear  as  a  surface  prominence. 
Its  upper  border — on  a  level  with  the 
centre  of  the  acetabulum — is  indistinct 
on  account  of  the  presence  of  the  glu- 
teus medius  tendon  which  passes  over 
it  to  be  inserted  into  the  outer  surface 
of  the  trochanter. 

In  front  the  muscular  eminences 
where  the  region  of  the  buttock  passes 
into  that  of  the  hip  are  due  to  the  glu- 
teus medius  above  and  more  anteriorly 
to  the  tensor  faciae  latae  (Fig.  632), 
which  shows  as  a  broad  elevation 
just    behind    a    vertical     line     drawn 

through  the  anterior  superior  spine  and  just  below  the  forepart  of  the  iliac  crest. 
It  can  be  best  seen  if  the  thigh  is  in  abduction  and  inward  rotation. 

As  the  skin  of  the  buttock  is  made  tense  when  the  thigh  is  flexed  on  the  pelvis, 
the  fold  of  the  nates  (gluteo-femoral  crease),  due  to  creasing  or  drawing  in  of  the 
skin,  is  formed  when  the  thigh  is  extended.      It  begins  just  below  the  level  of  the 


670  HUMAN    ANATOMY. 

tuberosity  of  the  ischium,  runs  horizontally  outward,  and  crosses  the  middle  of  the 
lower  edge  of  the  gluteus  maximus,  part  of  which — the  inner — is  therefore  above  it 
and  part — the  outer — below  it.  In  flexion  of  the  hip  the  gluteus  maximus  is  flattened 
and  the  skin  stretched  over  it,  and  hence  this  fold  is  more  or  less  completely  effaced. 
As  flexion  is  an  almost  constant  early  symptom  of  hip-joint  disease  (page  381),  and 
is  usually  associated  with  atrophy  of  the  muscles  moving  the  joint,  the  obliteration  of 
the  gluteo-femoral  crease,  characteristic  of  this  disease,  can  readily  be  understood. 

In  women,  on  account  of  the  thickness  of  the  supragluteal  layer  of  fat,  the  gluteo- 
femoral  crease  is  longer  and  deeper  than  in  men. 

The  various  bony  points  of  this  region  have  been  described  (pages  345,  349),  as 
have  the  different  lines  and  measurements  employed  in  the  diagnosis  of  fractures  of 
the  neck  of  the  femur  and  of  dislocation  (pages  362,  364,  367). 

2.  The  Thigh. — {a)  Anterior  crural  region.  The  hip  passes  insensibly  in 
front  and  below  into  the  region  of  the  thigh.  The  inguinal  furrow,  a  valuable  land- 
mark, separates  the  surface  of  the  abdomen  from  that  of  the  thigh  (page  1774).  It 
indicates  the  line  of  Poupart's  ligament,  which  may  be  felt,  in  the  absence  of  much 
subcutaneous  fat,  from  the  iliac  spine  to  the  pubic  spine,  more  easily  over  its  inner 
half,  and  still  more  easily  if  the  thigh  is  in  extension,  abduction,  and  outward  rotation. 
The  ligament  is  relaxed  by  flexion,  adduction,  and  inward  rotation  of  the  thigh, 
and  with  it,  to  some  extent,  the  deep  fascia?  of  the  thigh  and  abdomen  ;  therefore 
that  position  is  the  one  most  favorable  to  reduction  of  either  inguinal  or  femoral 
hernia  by  taxis  (pages  1770,  1774). 

Below  this  a  second  furrow — "  Holden's  line" — is  sometimes  seen  with  the  thigh 
in  slight  flexion,  beginning  at  the  scroto-femoral  angle  and  becoming  less  distinct  until 
it  is  lost  at  or  over  the  supratrochanteric  space.  It  runs  across  the  front  of  the  cap- 
sule of  the  hip-joint  and  is  lost  in  the  presence  of  synovitis  of  that  joint.  It  is  often 
indistinct,  and  in  some  subjects  cannot  be  made  out  at  all  (Treves). 

On  the  line  of  this  furrow,  and  just  external  to  a  vertical  line  drawn  through  the 
middle  of  Poupart's  ligament,  the  head  of  the  femur  can  sometimes  be  made  palpable 
by  extension  and  rotation  of  the  thigh,  but  this  is  rarely  possible  in  fat  or  muscular 
persons. 

The  depression  or  flattening  of  Scarpa's  triangle  (page  639)  can  usually  be  seen. 
The  tendon  of  origin  of  the  adductor  longus — made  prominent  by  abduction — and 
the  upper  portion  of  the  sartorius,  emphasized  by  flexion  and  outward  rotation  of  the 
thigh  with  the  knee  bent,  mark  its  inner  and  outer  borders  respectively.  The  sar- 
torius, continued  downward,  becomes  flattened  and  is  lost  in  the  rounded  fulness  on 
the  inner  side  of  the  knee.  Just  internal  to  a  line  bisecting  the  triangle  the  femoral 
artery  may  be  felt  and  its  pulsations  sometimes  seen.  A  very  trifling  depression  is 
occasionally  present  near  the  inner  angle  at  the  base  of  the  triangle,  and  then  indi- 
cates the  position  of  the  saphenous  opening  (page  635),  the  centre  of  which  is  from 
one  to  one  and  a  half  inches  below  and  the  same  distance  external  to  the  pubic  spine, 
which  is  on  a  transverse  line  drawn  through  the  upper  margin  of  the  greater  trochan- 
ter. From  the  apex  of  the  triangle  the  shallow  groove,  extending  towards  the  inner 
side  of  the  knee,  marks  the  course  of  the  sartorius  and  the  interval  between  the  quad- 
riceps extensor  and  the  adductors.  To  the  outer  side  of  the  triangle  the  rectus  can  be 
seen,  showing  below  the  anterior  superior  spine  in  the  interval  between  the  sartorius 
and  the  tensor  fascia?  lata?  ;  it  runs  down  the  front  of  the  thigh,  giving  it  its  convex 
fulness,  and  narrowing  to  its  ending  in  the  flattened  quadriceps  tendon,  the  edges  of 
which  stand  out  when  the  leg  is  strongly  extended  on  the  thigh.  The  obliteration 
of  Scarpa's  triangle,  in  full  extension  of  the  thigh,  is  due  to  the  thrusting  forward 
of  the  overlying  tissues  by  the  neck  and  the  upper  end  of  the  shaft  of  the  femur. 

To  the  inner  side  of  Scarpa's  triangle,  below  and  posteriorly  to  the  adductor 
longus,  the  other  adductors  and  the  gracilis  give  the  rounded  outline  to  the  inner  side 
of  the  upper  thigh.  Near  the  knee,  when  the  leg  is  flexed,  the  tendon  of  insertion  of 
the  adductor  magnus  can  be  plainly  felt  between  the  sartorius  and  vastus  internus. 
The  latter  muscle  stands  out  along  the  lower  half  of  the  thigh  and  is  still  more  promi- 
nent near  the  knee,  where  it  becomes  superficial  between  the  rectus  and  the  sartorius. 
On  the  outer  side  the  vastus  externus  gives  the  thigh  its  broad,  slightly  convex 
surface,  down  the  centre  of  which  there  is  sometimes  a  slight  vertical  groove  indi- 


SURFACE    LANDMARKS  :    THE    LOWER    EXTREMITY. 


671 


Fig.  633. 


■• 


eating  the  position  of  the  ilio-tibial  band  of  fascia  between  the  insertions  of  the  tensor 
fasciae  latas  and  gluteus  maximus  and  the  external  tibial  tuberosity.  More  pos- 
teriorly a  distinct  longitudinal  depression  corresponds  to  the  external  intermuscular 
septum,  between  the  vastus  externus  and  the  short  head  of  the  biceps.  At  the 
lower  third  of  the  thigh  this  groove  indicates  the  line  of  nearest  approach  of  the  shaft 
of  the  femur  to  the  surface.  Elsewhere  it  is 
usually  so  covered  by  muscular  masses  that 
it  is  not  to  be  felt,  even  indistinctly.  The 
corresponding  internal  septum—  between  the 
vastus  internus  and  the  adductors  and  pecti- 
neus — produces  no  surface  marking. 

(#)  Posterior  crural  region.  The  ham- 
strings, descending  from  beneath  the  lower 
edge  of  the  gluteus  maximus,  cannot  at  first 
be  separately  identified.  Lower,  a  very  slight 
depression  may  mark  the  interval  between 
the  semimembranosus  and  the  semitendino- 
sus,  and  the  biceps  tendon  becomes  a  salient 
rounded  cord. 

When  the  limbs  are  straight  with  the 
knees  together  there  should  be  but  a  slight 
interval  between  the  thighs,  and  that  only 
where  the  sartorius  muscles  curve  back  to 
lie  along  the  inner  surface  of  the  limb.  In 
women,  owing  to  the  greater  quantity  of  sub- 
cutaneous fat,  the  thighs  may  be  in  contact 
all  the  way  down  (Thomson). 

3.  The  Knee. — On  the  anterior  sur- 
face the  quadriceps  tendon  and  the  ligamen- 
tum  patellae  are  made  more  prominent  by 
strong  extension  of  the  leg,  and  on  each  side 
of  the  ligament  the  little  eminence  made  by  the 
protrusion  of  the  soft  subpatellar  fat  becomes 
visible.  The  angle  made  by  the  axes  of  the 
tendon  and  ligament  should  be  noted  (page 
418). 

The  outline  of  the  patella  is  easily  felt 
and  can  usually  be  seen.  Above  it  is  a  slight 
depression.  At  its  sides  are  two  concavities 
— the  inner  of  which  is  a  little  more  marked, 
as  the  inner  border  of  the  patella  is  the 
more  prominent — which  in  fat  persons  may 
disappear,  as  they  do,  together  with  the  su- 
prapatellar depression,  in  synovitis  of  the 
knee-joint  (page  413).  Both  anteriorly  and 
laterally  the  landmarks  have  been  sufficiently 
described  (pages  367,  390). 

Posteriorly  the  popliteal  space — the  ham 
— is  slightly  convex  during  extension  of  the 
leg  and  deeply  concave  when  it  is  flexed. 
The  boundaries,  the  relations  of  the  ham- 
string tendons,  of  the  ilio-tibial  band  externally  and  of  the  sartorius  tendon  internally 
have  been  described  (pages  409,  646).  At  the  lower  portion  of  the  space  the  con- 
verging fleshy  bellies  of  the  gastrocnemius  may  be  felt. 

4.  The  Leg. — The  landmarks  relating  to  the  tibia  (page  390)  and  fibula  (page 
396)  have  been  described.  Between  these  bones  the  belly  of  the  tibialis  anticus  causes 
a  distinct  prominence,  to  the  fibular  side  of  which  is  the  narrower  and  less-marked 
elevation  due  to  the  extensor  longus  digitorum.  Below  the  middle  third  of  the  leg 
these  muscles  are  tendinous,  but  by  dorsal  flexion  of  the  foot  and  of  the  toes  (exten- 


Tubercle  of  ubia | 


Anteromedian  surface  of  right  leg,  showing 
modelling  on  living  subject. 


672  HUMAN    ANATOMY. 

sion)  they  can  be  made  to  stand  out  with  the  tendon  of  the  extensor  proprius  hallucis 
between  them  ;  to  the  outer  side  of  the  extensor  longus  digitorum  tendon  a  slight 
groove  indicates-  the  interval  between  that  muscle  and  the  peroneus  tertius.  The 
latter — as  a  muscle  peculiar  to  man  and  probably  developing  as  a  result  of  his  assump- 
tion of  the  erect  posture — is  not  invariably  present.  Above,  between  the  extensor 
longus  digitorum  and  the  soleus,  the  peroneus  longus  makes  a  longitudinal  elevation 
shading  off  below — where  the  fleshy  fibres  become  tendinous — into  the  flatter  pero- 
neus brevis. 

Posteriorly  the  swell  of  the  calf  is  formed  by  the  gastrocnemius,  and  its  surface 
markings  are  due  to  the  peculiar  arrangement  of  the  fleshy  and  tendinous  portions  of 
that  muscle.  When  the  calf  muscles  are  in  action,  as  in  standing  on  the  toes,  it  will 
be  seen  that  the  inner  head  is  the  larger  and  descends  somewhat  lower  than  the  outer 
head  ;  and  the  lateral  borders  of  the  soleus  will  be  seen  coming  to  the  surface  beyond 
the  lower  part  of  the  gastrocnemius  and  the  tendo  Achillis  and  showing  as  curved 
eminences,  of  which  the  outer  is  the  longer. 

5.   The  Ankle  and  Foot. — The  bony  landmarks  have  been  described  (pages 

390-  396,  437>  449.  453)- 

At  the  front  of  the  ankle  the  extensor  tendons  are  easily  recognized.  The 
largest  and  most  internal  is  that  of  the  tibialis  anticus  ;  then,  in  order,  the  extensor 
proprius  hallucis,  extensor  longus  digitorum,  and — when  present — the  peroneus  ter- 
tius. Beneath  the  tendons  of  the  long  extensor  and  just  below  the  external  mal- 
leolus, the  fleshy  belly  of  the  short  extensor  of  the  toes,  filling  the  space  between  the 
os  calcis  and  astragalus,  can  easily  be  felt  as  a  soft  swelling  over  the  outer  part  of  the 
tarsal  region,  and  is  distinctly  visible  when  in  action.  On  either  side  of  the  tendi- 
nous elevation,  on  a  level  with  the  line  of  the  ankle-joint  and  in  front  of  each 
malleolus,  is  a  little  depression.  This  is  effaced  when  the  capsule  is  distended 
by  effusion  (page  451).  The  two  fleshy  masses  on  the  inner  and  outer  border  of 
the  foot  are  due  respectively  to  the  abductor  and  flexor  brevis  hallucis  and  the  ab- 
ductor and  flexor  brevis  minimi  digiti.  The  dorsal  interossei  project  upward  slightly 
between  the  metatarsal  bones.  The  lines  on  the  dorsum  of  the  foot  corresponding 
to  the  various  joints  have  been  described  (page  453). 

Behind  the  ankle  and  at  the  sides  of  the  tendo  Achillis — between  it  and  the  pos- 
terior surfaces  of  the  malleoli — are  two  concavities,  of  which  the  outer  is  the  deeper. 
In  it  the  tendons  of  the  peroneus  longus  and  brevis  may  be  felt,  the  latter  the  nearer 
to  the  fibula.  In  the  inner  concavity  lie,  in  order  from  the  malleolus  backward,  the 
tendons  of  the  tibialis  posticus,  the  flexor  longus  digitorum,  and  the  flexor  longus 
pollicis. 

On  the  sole  of  the  foot  the  abductors  of  the  great  and  little  toes  show  somewhat 
on  the  surface,  but  the  chief  outlines  are  determined  by  the  arch  of  the  foot,  the 
strong  plantar  fascia,  and  the  thick  integument.  The  digital  creases  have  but  little 
practical  value. 

As  the  foot,  taken  as  a  whole,  acts  as  a  lever,  and  as  the  calf  muscles  are 
attached  to  the  heel, — the  short  end  of  such  a  lever, — it  follows  that  the  develop- 
ment of  these  muscles  will  stand  in  some  relation  to  the  length  or  projection  of  the 
heel.  As  a  short  lever  will  require  the  application  of  a  greater  force  to  produce 
the  same  result  than  will  a  long  lever,  we  find  the  most  marked  muscular  develop- 
ment of  the  calf  associated  with  a  short  foot  and  a  short  heel,  while  a  long  foot  and 
a  long  heel  are  the  usual  concomitants  of  a  poorly  developed  calf  (Thomson).  The 
athletic  feats  of  some  runners  with  poorly  developed  calves  may  sometimes  be 
explained  by  observing  the  unusual  length  and  projection  of  the  heel. 


THE  VASCULAR  SYSTEM. 

The  vascular  system  is  composed  of  the  organs  immediately  concerned  in  the 
circulation  throughout  the  body  of  the  fluids  which  convey  to  the  tissues  the  nutritive 
substances  and  oxygen  necessary  for  their  metabolism  and  carry  from  them  to  the 
excretory  organs  the  waste  products  formed  during  metabolism. 

The  system  is  usually  regarded  as  being  composed  of  two  portions,  the  one  con- 
sisting of  organs  in  which  circulates  the  red  fluid  which  we  term  blood,  while  the 
organs  of  the  other  contain  a  colorless  or  white  fluid  known  as  lymph  or  chyle  ;  the 
former  of  these  subsystems  is  the  blood-vascular  system  and  the  latter  is  the  lymphatic 
system.  It  must  be  recognized,  however,  that  the  two  systems  communicate,  and  that 
the  lymphatic  system  develops  as  an  outgrowth  from  the  blood-vascular  system  ;  so 
that  while  it  proves  convenient  for  descriptive  purposes  to  regard  the  two  systems  as 
distinct,  nevertheless,  they  are  intimately  associated  both  anatomically  and  embryo- 
logically. 

THE  BLOOD-VASCULAR  SYSTEM. 

The  blood-vascular  system  consists  of  ( I )  a  system  of  canals  known  as  blood- 
vessels, traversing  practically  all  parts  of  the  body,  and  (2)  of  a  contractile  organ,  the 
heart,  by  whose  pulsations  the  blood  is  forced  through  the  vessels.  The  vessels  are 
again  divisible  into  ( 1 )  vessels  which  carry  the  blood  from  the  heart  to  the  tissues 
and  are  known  as  arteries,  (  2 )  exceedingly  fine  vessels  which  form  a  net-work  in  the 
tissues  and  are  termed  capillaries,  and  (3)  vessels  which  return  the  blood  from  the 
tissues  to  the  heart  and  are  known  as  veins. 

THE    STRUCTURE   OF    BLOOD-VESSELS. 

Although  passing  into  one  another  insensibly  and  without  sharp  demarcation, 
where  typically  represented  the  arteries,  capillaries,  and  veins  present  such  character- 
istic histological  pictures  that  they  are  readily  distinguished  from  one  another. 

All  blood-vessels,  including  the  heart,  possess  an  endothelial  lining  which  may 
constitute  a  distinct  inner  coat,  the  tunica  intima,  or,  as  in  the  capillaries,  even  the 
entire  wall  of  the  vessel.  Usually,  however,  the  intima  consists  of  the  endothelium 
reinforced  by  a  variable  amount  of  fibro-elastic  tissue  in  which  the  elastica  predomi- 
nates. Except  within  the  walls  of  capillaries,  external  to  the  intima  lies  a  thick 
middle  coat,  the  tunica  media,  which  typically  is  composed  of  intermingled  lamella? 
of  involuntary  muscle  and  elastica  and  fine  fibrillae  of  fibrous  tissue.  Outside  the  media 
follows  the  tunica  externa  or  adventitia,  which,  although  usually  thinner  than  the 
middle  coat,  is  of  exceptional  strength  and  toughness — characteristics  conferred  by 
its  fibro-elastic  tissue  and  upon  which  the  integrity  of  a  ligature  often  depends. 

It  should  be  noted  that  the  endothelial  tube  is  the  fundamental  and  primary 
structure  in  all  cases,  the  other  coats  being  secondary  and  variable  according  to  the 
size  and  character  that  the  vessel  attains.  The  customary  division  into  the  three 
coats  is  more  or  less  artificial  and  in  the  larger  vessels  is  often  uncertain.  The 
recognition  of  an  inner  endothelial  and  an  outer  musculo-elastic  coat  often  more  closely 
corresponds  to  the  actual  arrangement  of  the  tissues  than  the  conventional  subdivision 
into  three  tunics. 

The  endothelial  lining  of  the  arteries  consists  of  elongated  spindle-shaped 
plates  united  by  narrow  sinuous  lines  of  cement  substance  which,  after  silver-staining. 
map  out  the  irregular  contours  of  the  cells  with  diagrammatic  clearness  (Fig.  634). 
At  the  junction  of  the  plates,  occasional  accumulations  of  the  cement  substance  mark 
minute  intercellular  areas,  the  stigmata,  that  indicate  points  of  less  accurate  apposi- 
tion. Within  the  veins,  the  endothelial  plates  are  shorter  and  broader  than  in  the 
arteries,  approaching  somewhat  irregular  polygons  in  outline.      The  demarcation  of 

43  6r> 


674 


HUMAN   ANATOMY. 


the  endothelium  into  distinct  cells  is  less  evident  in  the  capillaries  than  in  the  larger 
vessels,  in  some  cases  a  continuous  syncytial  sheet  replacing  the  definitely  outlined 
plates.  The  presence  of  a  relatively  small  oval  nucleus  is  readily  demonstrated  by 
suitable  stains. 

The  involuntary  muscle  varies  in  amount,  from  the  imperfect  single  layer  of 
muscle-cells  found  in  the  arterioles,  to  the  robust  muscular  coat  of  many  lamellae  in 
the  larger  arteries.  It  is  relatively  best  developed  in  arteries  of  medium  size,  where 
the  muscle  occurs  in  distinct  broad  or  sheet-like  bundles  between  the  strands  of  elastic 
tissue.  The  component  fibre-cells  are  short  and  often  branched  and,  for  the  most 
part,  circularly  disposed.  The  distribution  of  the  muscular  tissue  is  much  less 
regular  and  constant  in  the  veins  than  in  the  arteries,  since  in  many  it  is  scanty, 
in  some  entirely  wanting,  and  in  a  few  veins  excessive,  occurring  in  both  circular  and 
longitudinal  layers.  The  striated  muscle  found  in  the  large  vessels  communicating 
with  the  heart  resembles  that  of  the  cardiac  wall  from  which  it  is  derived. 

Connective-tissue  is  represented  in  the  arteries  and  veins  by  both  fibrous  and 
elastic  tissue.  The  former  is  present  as  delicate  or  coarser  bundles  of  fibrillae  that 
extend  between  the  other  components  of  the  vascular  wall. 

Fig.  634. 


lteriole  after  silver-staining  ;  X  200 
more  highly  magnified.     X  500. 


B  endothelial  cells 


The  elastic  tissue  is  very  conspicuous  in  all  arteries  save  the  smallest,  and  in 
many  veins.  It  presents  all  variations  in  amount  and  arrangement  from  loose  net- 
works of  delicate  fibres  in  the  smaller  vessels  to  robust  plates  and  membranes  in  the 
largest  arteries.  Within  the  intima  of  the  latter,  the  elastica  often  occurs  as  sheets 
broken  by  pits  and  perforations,  which  are,  therefore,  known  as  fe?iest?-ated  mem- 
branes. 

Nutrient  blood-vessels  are  present  within  the  walls  of  all  the  larger  vessels, 
down  to  those  of.  i  mm.  in  diameter,  and  provide  nourishment  for  the  tissues  com- 
posing the  tubes.  These  vasa  vasorum,  as  they  are  called,  are  usually  branches  from 
some  neighboring  artery,  their  favorite  situation  being  the  external  coat  within  which 
they  ramify,  breaking  up  into  capillaries  that,  in  the  larger  vessels,  invade  the  adja- 
cent media.  The  blood  from  the  vascular  wall  is  collected  by  small  veins  that  accom- 
pany the  nutrient  arteries,  or,  as  in  the  case  of  the  veins,  empty  directly  into  the 
venous  trunk  in  whose  walls  they  course. 

Lymphatics  are  represented  by  spaces  both  within  the  muscular  tissue  and 
beneath  the  endothelium.  In  certain  situations,  conspicuously  in  the  brain  and  the 
retina,  the  blood-vessels  are  enclosed  within  lymph-channels,  the  perivascular  lymph- 
sheaths,  that  occupy  the  adventitia. 

The  nerves  distributed  to  the  walls  of  blood-vessels,  especially  to  the  arteries, 
are  numerous  and  include  both  sympathetic  and  spinal  fibres.      The  former  are  des- 


STRUCTURE   OF    BLOOD-VESSELS 


675 


tined  particularly  for  the  muscular  tissue  and,  therefore,  are  directed  to  the  media, 
although  vessels  in  which  muscle  is  wanting,  as  in  certain  veins  and  the  capillaries, 
are  not  without  nerves.  From  the  plexus  that  surrounds  the  vessel,  notably  rich 
about  the  arteries,  nerve-fibrilke  penetrate  the  media  and  end  among  the  muscle- 
fibres  in  the  manner  usual  in  such  tissue  (page  10 15).  Special  sensory  nerve- 
endings  have  been  described  in  both  the  external  and  internal  tunics. 

The  Arteries. — Since  the  arrangement  of  the  component  tissues  is  most 
typical  in  arteries  of  medium  size  (from  4-6  mm.  in  diameter),  the  radial  artery  may 
appropriately  serve  for  description.  Seen  in  cross-section  (Fig.  635),  after  the  usual 
methods  of  preservation  and  staining,  the  intima  presents  a  plicated  contour  as  it 
follows  the  foldings  of  the  internal  elastic  membrane  that  appears  as  a  conspicuous 
corrugated  light  band  marking  the  outer  boundary  of  the  inner  tunic.  The  lining 
endothelial  cells  are  so  thin  that  in  profile  their  presence  is  indicated  chiefly  by  the 
slightly  projecting  nuclei.     .Between  the  endothelium  and  the  elastic  membrane  the 


oluntary  muscle 


intima  includes  a  thin  layer  of  fibrous  and  elastic  fibriHee.  The  media,  thick  and 
conspicuous,  consists  of  circularly  disposed  flat  bundles  of  involuntary  muscle  sepa- 
rated by  membranous  plates  of  elastic  tissue,  that  in  the  section  appear  light  and 
unstained.  After  the  action  of  selective  dyes,  as  orcein,  the  elastica  is  very  con- 
spicuous (Fig.  636).  Delicate  fibrillae  of  fibrous  tissue  course  among  the  musculo- 
elastic  strands.  Beneath  the  outer  coat,  the  elastica  becomes  condensed  into  a  more 
or  less  distinct  external  elastic  membra7ie  that  marks  the  outer  boundary  of  the  media. 
The  adventitia  varies  in  thickness,  in  the  medium-sized  arteries  being  relatively  better 
developed  than  in  the  larger  ones.  It  consists  of  bundles  of  fibrous  tissue  intermingled 
with  elastic  fibres  of  varying  thickness.  The  adventitia  contains  the  vasa  vasorum 
and  chief  lymph-channels  of  the  vascular  wall. 

Followed  towards  the  capillaries,  the  coats  of  the  artery  gradually  diminish  in 
thickness,  the  endothelium  resting  directly  upon  the  internal  elastic  membrane  so 
longas  the  latter  persists,  and  afterwards  upon  the  rapidly  attenuating  media.  The 
elastica  becomes  progressively  reduced  until  it  entirely  disappears  from  the  middle 


676 


HUMAN    ANATOMY. 


coat,  which  then  becomes  a  purely  muscular  tunic  and,  before  the  capillary  is  reached, 
is  reduced  to  a  single  layer  of  muscle-cells.  In  the  precapillary  arterioles  the  muscle 
no  longer  forms  a  continuous  layer,  but  is  represented  by  groups  of  fibre-cells  that 


Transverse  section  of  artery  of  mediun 


,  stained  to  show  elastic  tissue.     X  : 


partially  wrap  around  the  vessel,  and  at  last  are  replaced  by  isolated  elements.  After 
the  disappearance  of  the  muscle-cells,  the  blood-vessel  has  become  a  true  capillary. 
The  adventitia  shares  in  the  general  reduction  and  gradually  diminishes  in  thickness 
until,  in  the  smallest  arteries,  it  consists  of  only  a  few  fibro-elastic  strands  outside  the 
muscle-cells. 

In  the  large  arteries,  on  the  other  hand,  the  intima  and  media  chiefly  undergo 
augmentation.  Although  the  inner  coat  gready  thickens  and  contains  a  large 
amount  of  fibrous  tissue  and  elastica,  a  conspicuous  internal  elastic  membrane,  as 
seen  in  the  smaller  vessels,  is  lacking,  since  the  elastic  plates  and  membranes  are 
now  so  abundant  that  the  local  accumulation  is  no  longer  striking,  the  boundary 
between  the  inner  and  middle 

coats     being,      therefore,     less  ^IG-  6->7- 

sharply  defined.  The  character 
of  the  thickened  media  also 
changes,  the  muscular  tissue  be- 
ing relatively  reduced  and  over- 
shadowed by  the  excessive  de- 
velopment of  the  fibro-elastic 
tissue,  which  is  arranged  in  reg- 
ularly disposed  lamellae  separa- 
ting the  muscle-bundles  and 
conferring  a  more  compact  and 
denser  character  to  the  wall  of 
the  vessel.  The  adventitia, 
while  relatively  thinner  than  in 
arteries  of  medium  size,  is  also 
increased  and  consists  of  robust 
fibres  and  plates  of  elastica,  many  of  which  are  longitudinally  disposed  and  irreg- 
ular, although  strong,  bundles  of  fibrous  tissue.  Exceptionally,  longitudinal  strands 
of  muscle  appear  in  the  outer  coat  next  the  media.     In  the  roots  of  the  aorta  and 


;  reduced  to  single 


STRUCTURE   OF   BLOOD-VESSELS. 


677 


pulmonary  artery,  the  media  consists  chiefly  of  striated  muscle  which  resembles  that 
of  the  myocardium  with  which  it  is  continuous,  both  vessels  having  been  derived  from 
a  common  trunk,  the  bulbus  arteriosus,  the  anterior  segment  of  the  primary  heart -tube. 

The  Veins. — The  walls  of  the  veins  are  always  thinner  than  those  of  corre- 
sponding arteries  and  are  more  flaccid  and  less  contractile  in  consequence  of  the 
smaller  amount  of  elastic  and  muscular  tissue  that  they  contain. 

In  veins  of  medium  size  (from  4-8  mm.  in  diameter),  the  intima  consists  of  the 
lining  endothelium,  the  cells  of  which  are  relatively  broad  and  short,  a  thin  layer  of 
fibrous  connective  tissue  and   net-works  of  fine  elastic  fibres.      A  distinct  internal 
elastic  membrane  is  seldom  pres- 
ent,   at    most   a    condensation    of  Fig.  63S. 
elastic  fibrillar  marking  the  outer    ____^  ^^^^-^-=^=^=^^^7^^-— —-— ==^--_ 
limit  of  the  inner  coat.      In  some    -^  -  K[-  .- r.>-~I. :V=y  ~L     '.--  :~~ -^-^  />^-  intima 
veins,     as     the     cephalic,     basilic,      V- /S^^""/^-"-  -■■<-'-- Z~ 7C'--  ■  ""-i""v^"^ 
femoral,  long  saphenous,  and  pop-      ~-^"~.~^_""-';" "":?— "~.  -'■" ~ "-  ~  :'^_~  ~~.'^~  ~~il~J'- 
liteal,    bundles   of    smooth    muscle       _:  ".  r-\-  ^;;^~"        Vr_    ""■.--    J-~-_    ~3g|§ 
occur  within   the  intima.      In  ad-           vjv  y:»^r-    -  ® -i- "•■-  >-_-'■- _---- '-"~J2--  J 
dition    to   the   circularly  disposed         _  I--'^ _  \^"L' *;•_*-;_=  ■-'.'.-^". r^-V.J    ~vr    - 
thin  sheets  of  muscular  and  fibro-        . : :  -"-~"-_~~  r.-X  ■■'  ~  ■"■-'"- ~~-..~'  ~~-l:;  :~    - 
elastic  tissue,   the  media  contains       .    ^'--~_  - 1~  J^  2   1     -    -^         ~~        ^r::? 
fibro-elastic     plates,     sometimes       ~~*"^  ./^ -~-  ~.-.^ -""-■-  -Vt_-    . 
mingled    with    a   few    bundles    of           ~2"2?  ~~  —  '-.-'"  ~- '  --  --"""-■•""'"-'   •>'"-■  .7.  NK',1,a 
muscle-cells,    that    extend    longi-           ~:-~~_ '---.-'-- '  I-V -■-  —  .!:—"  ' -t7— -KSii: 
tudinally.      In  certain  veins     is  111         ...--_..       -_~      .      ..  .-■■      j-..      ■■:-,,,,, 
the  saphenous,  deep  femoral,  and        ~~-  -'■'■      -     ■        ""  -.■:■-••■-■■.■ r- 
popliteal,    the    longitudinal    fibres        ..- -2"  Z   ~'-\    ~is~-   [■'     I.   ,  .  .~     .  :;     - 
may  constitute  a  zone  beneath  the        [-~  -  -  -    :.-   - ;  ;  "-_:    _  ~  _-.J ',  :~~.    ~~  ~    : 
intima  to  the  exclusion  of  the  mus-         ,'ir  "V  ■  ~V.  .  "J      --"  -~:/  ;     -7    :7~-- 
cular    tissue.       The    adventitia    is         "  J_->    __        -      \^_.  r    _-'      """_"• --"-- ~ 
often  thicker  than  the  media,  and         S|g  _                    ".._"•■         7      .    ;-- ■-■_ 
consists  of  interlacing  fibres   and         =—>'.?.,  l-~  "  "~   "-V    '"     i'~  -=~-~     "T 
net-works  of  fibro-elastic  strands,        jgj        '_  ~   '-,,.  -    ~ -,    .-  3="=^=^;      ■ 
the  general  direction  of  which  is        -a^i,    J  ,,-s^.^v,-^.      ':-;-— -^waa^-"-1'.-   Adventma 
lengthwise.      In   many  veins,  par-         ..-*.-<■.>  ^?~-~-  '^ -,v~%  ~-  '"'■  -  "~^~     -■'      _    ~- 
ticularly  in  those  of  the  lower  ex-        Ip5~             .'     0- "-"     __         .  .'__,"_.. 
tremity,    the    outer   coat    contains                   - ~  }•-  -"^w;  ~~— -„  "       ~  _-~-~    x^SL 
bundles  of  longitudinally  disposed         "-.  u"\  -      '•/  .  _  :.~  -           ■-         £    v---"-.  :-^| 
muscle-cells.                                                n^^    ,       ,    -- ;v  '■-'*'-.  - 

The  valves  with  which  many         ^  -. "--  ~---^~_       "i?5?-"' 

veins     are     provided     consist    of         ~SQ~- •      ~~~  '     ~"  ■    ■   -  -..-.- 

paired  crescentic  folds  (Fig.  641)  =.--     .  -  - 

of  the  intima,  covered  on  both 
sides  with  endothelium,  containing 
a  small  amount  of  fibro-elastic  tis- 
sue. The  attached  border  of  the 
leaflets  ends  in  narrow  prolonga- 
tions that  extend  beyond  the  free 
margin  of  the  valve.  Between  the 
leaflets  of  the  valve  and  the  wall 
of  the  vein  lie  the  pocket-like  si- 
nuses, which  the  blood  distends  when  the  valve  is  closed.  In  the  structure  of  their 
walls,  the  large  veins  present  many  deviations  from  the  typical  arrangement.  While 
the  intima  is  only  exceptionally  increased,  as  in  the  hepatic  part  of  the  inferior  vena 
cava  and  the  beginning  of  the  portal  vein,  the  media  is  often  markedly  thickened. 
This  increase  is  chiefly  due  to  augmentation  of  the  elastic  and  fibrous  tissue,  the  mus- 
cle remaining  comparatively  scanty.  The  splenic  and  portal  veins,  however,  are 
particularly  rich  in  muscular  tissue  ;  on  the  other  hand,  the  media  may  be 
almost  wanting,  as  in  the  greater  part  of  the  inferior  vena  cava  and  the  larger 
hepatic  veins. 


Transverse  section  of  abdominal  aorta.    X  90. 


678 


HUMAN   ANATOMY. 


Lack  of  muscle  within  the  media  is  often  compensated  by  an  unusual  develop- 
ment of  such  tissue  in  the  adventitia;  in  some  large  veins,  as  in  the  hepatic  portion  of 

the    inferior   cava,   su- 
Fig.  639.  perior    mesenteric,    or 

external  iliac,  the  in- 
ner half  or  two-thirds 
of  the  outer  coat  is 
occupied  by  robust 
bundles  of  longitudi- 
nally arranged  muscle. 
In  some  cases,  how- 
ever, as  in  the  renal 
and  portal  veins, .  the 
longitudinal  muscle  in- 
vades the  entire  thick- 
ness of  the  adventitia, 
or,  as  in  the  supra- 
renal vein,  the  muscle 
of  the  outer  tunic  may 
include  both  circular 
and  longitudinal  layers. 
The  walls  of  the 
small  veins  (less  than 
.4  mm.  in  diameter) 
consist  of  only  endo- 
thelium and  connective 
tissue.  The  latter  rep- 
resents a  relatively  ro- 
bust adventitia  and  a 
feebly  developed  me- 
dia, muscle-fibres  being 
wanting.  Traced  tow- 
ards the  capillaries,  the  connective  tissue  gradually  diminishes  until  the  endothelial 
coat  alone  remains.  In  passing  into  veins  of  medium  size,  at  first  the  muscle-cells  are 
short  and  scattered  and  only 

partly  encircle  the  tube.     Far-  Fig.  640. 

ther  along  the  elastica  appears 
in  the  form  of  delicate  fibres 
and  net-works  that  increase  in 
size  and  density  as  the  muscu- 
lar tissue  becomes  more  pro- 
nounced. It  is  worthy  of 
mention  that  certain  veins,  no- 
tably those  of  the  brain  and  pia 
mater,  the  dural  sinuses,  and 
the  blood-spaces  of  cavernous 
tissue,  are  usually  entirely 
devoid  of  muscle,  although 
in  the  walls  of  some  of  the 
larger  cerebral  veins,  small 
strands  of  such  tissue  occur. 

The  Capillaries. — The 
most  favorable  arrangement 
for  efficient  nutrition  is  mani-  A 
festly  one  insuring  the  passage 
of  the  blood-stream  at  a  re- 
duced rate  of  speed  in  inti- 
mate relations  with  the  tissue-elements.  These  requirements  are  met  in  the  capil- 
laries whose  collectively  increased  calibre  and  thin  walls  favor  slowing  of  the  blood- 


Transverse  section  of  pulmonary  artery  near  its  root, 
showing  striated  muscle.     X  I5°- 


A  ■ 


iii 


& 


v 


* 


STRUCTURE   OF    BLOOD-VESSELS. 


679 


Fig.  641. 


stream  and  the  passage  of  the  plasma  and  oxygen  into  the  surrounding  tissues. 
The  walls  of  the  capillaries  consist  of  only  the  lining  plates,  the  entire  vessel  being  in 
fact  a  delicate  endothelial  tube.  The  cells  composing  the  latter  are 
elongated  lanceolate  plates,  possessing  oval  nuclei,  united  by  nar- 
row lines  of  cement  substance.  Although  the  transition  from  the 
arterioles  is  gradual,  the  final  disappearance  of  the  muscle-cells  marks 
the  beginning  of  the  true  capillaries  ;  the  passage  of  the  latter  into 
the  veins  is  less  certain,  since  muscular  tissue  is  wanting  in  those 
of  small  size.  In  the  smallest  capillaries  two  endothelial  plates  may 
suffice  to  encircle  the  entire  lumen ;  in  the  larger  three  or  four  cells 
may  be  required  to  complete  the  vessel.  Preformed  openings  (sto- 
mata)  in  the  walls  of  the  capillaries  do  not  exist,  the  passage  of  the 
leucocytes  and,  under  certain  conditions,  also  of  the  red  blood-cells 
(diapedesis)  and  of  small  particles  of  foreign  substances,  being  effected 
between  the  endothelial  plates.  In  some  capillaries,  as  in  those  of 
the  choroid,  liver,  or  renal  glomeruli,  the  usual  demarcation  of  the 
wall  into  distinct  cells  is  wanting,  the  individual  endothelial  plates 
being  replaced  by  a  continuous  nucleated  sheet  or  syncytial  layer. 
Where  the  capillaries  course  within  fibrous  tissue,  not  uncommonly  the 
vessel  is  accompanied  by  delicate  strands  of  connective  tissue  (adventitia  capillaris) 
that  suggest  an  external  sheath. 

The  capillaries  are  usually  arranged  as  net-works,  of  which  the  channels  are  of 
fairly  constant  size  within  the  tissue  to  which  they  are  distributed.  During  life  it  is  prob- 
able that  none  are  too  small  to  permit  the  passage  of  the  red  blood-cells,  while  many 
admit  two  or  even  three  such  elements  abreast.  Their  usual  diameter  varies  between 
.008  and  .020  mm.  The  capillary  net-works  in  various  parts  of  the  body  differ  in  the 
form  and  closeness  of  their  meshes,  since  these  details  are  influenced  by  the  arrange- 
ment of  the  component  elements  and  by  the  function  of  the  structures  supplied.  Thus, 
in  muscles,  tendons,  and  nerves  the  meshes  are  elongated  and  narrow;  in  glands,  the 
lungs,  and  adipose  tissue  they  are  irregularly  polygonal;  in  the  liver-lobules  converg- 
ingly  or  radially  disposed;  while  in  the  subepithelial  papillae  of  the  mucous  membranes 
and  the  skin  the  capillaries  commonly  form  loops.      In  general,  it  may  be  assumed  that 


Portion  of  fem- 
oral vein,  opened 
to  show  bicuspid 


■:£*: 


10 


Capillaries  arising  from  arteriole  and  ending  in  small  vein  in  omentum.    X  2c 


the  greater  the  functional  activity  of  an  organ,  the  closer  is  its  capillary  net-work. 
Organs  actively  engaged  in  excretion,  as  the  kidneys,  or  the  elimination  of  substances 


680  HUMAN   ANATOMY. 

from  the  blood,  as  the  lungs  or  liver,  as  well  as  those  producing  substances  directly 
entering  the  circulation  (organs  of  internal  secretion),  as  the  thyroid  gland,  are  pro- 
vided with  exceptionally  rich  and  close  net-works.  The  mesh-works  within  the  walls 
of  the  pulmonary  alveoli  are  of  remarkable  closeness  and  are  often  narrower  than  the 
capillaries  surrounding  them. 

Under  the  name,  sinusoids,  Minot1  has  grouped  the  circulation  occurring  in 
certain  organs,  as  the  liver,  in  which  the  capillaries  are  formed  by  the  invasion  and 
subdivision  of  the  large  original  blood-channel  by  the  tissue-cords.  The  resulting 
sinusoids  differ  from  ordinary  capillaries,  therefore,  in  connecting  afferent  and  efferent 
vessels  of  the  same  nature,  both  being  either  venous'  or  arterial.  Capillaries,  on  the 
contrary,  form  communications  between  arteries  and  veins.  In  consequence  of  the 
invagination  of  the  original  vessel,  its  endothelium  bears  an  unusually  intimate  rela- 
tion to  the  tissue-trabeculse,  little  or  no  connective  tissue  intervening.  F.  T.  Lewis 2 
has  shown  that  the  Wolffian  body  and  the  developing  heart  also  present  examples  of 
sinusoidal  formation,  and  suggests  the  significance  of  sinusoids  as  representing  a 
primitive  type  of  circulation. 

THE   BLOOD. 

The  fluid  circulating  within  all  parts  of  the  blood-vascular  system  consists  of  a 
clear,  almost  colorless  plasma  or  liquor  sanguinis  in  which  are  suspended  vast 
numbers  of  small  free  corpuscular  elements,  the  blood-cells.  The  latter  are  of  two 
chief  kinds,  the  colored  cells,  or  erythrocytes,  and  the  colorless  or  leucocytes.  The 
characteristic  appearance  of  the  blood  is  due  to  the  presence  of  hemoglobin  con- 
tained within  the  erythrocytes  which,  while  individually  only  faintly  tinted,  collect- 
ively impart  the  familiar  hue  as  well  as  a  certain  degree  of  opacity.  That  the 
characteristic  pigment  is  limited  to  the  cells  is  shown  by  the  lack  of  color  and  the 
transparency  of  the  plasma  when  examined  under  the  microscope,-  although  to  the 
unaided  eye  the  blood  appears  uniformly  red  and  somewhat  opaque.  The  most  im- 
portant property  of  hemoglobin  is  its  great  affinity  for  oxygen  which,  taken  up  from 
the  air  during  respiration  and  combined  as  oxyhemoglobin,  is  carried  by  the  red 
cells  to  all  parts  of  the  body.  When  rich  in  oxygen  (containing  about  twenty  vol- 
umes) the  blood  possesses  the  bright  scarlet  hue  characteristic  of  arterial  blood;  after 
losing  approximately  one-half  of  its  oxygen  and  acquiring  about  an  equal  volume  of 
carbon  dioxide  during  its  intimate  relations  with  the  tissues,  the  blood  returned  by 
the  veins  is  dark  purplish-blue  in  color.  If  the  hemoglobin  escapes  from  the  eryth- 
rocytes into  the  plasma,  the  latter  becomes  deeply  tinged  and  the  blood  loses  its 
opacity  and  becomes  transparent  or  ' '  laked. ' ' 

The  specific  gravity  of  normal  blood  is  about  1060;  its  reaction  is  alkaline  and 
due  chiefly  to  the  presence  of  sodium  carbonate.  Immediately  after  withdrawal  from 
the  body  the  blood  possesses  a  characteristic  odor  that  probably  depends  upon  cer- 
tain volatile  fatty  acids.  When  fresh  it  is  slippery  to  the  feel,  but  after  exposure 
to  air  becomes  sticky.  Upon  standing  it  undergoes  coagulation,  whereby  the  cor- 
puscles become  entangled  among  the  innumerable  delicate  filaments  of  fibrin,  a  pro- 
teid  substance  that  appears  in  the  plasma  after  withdrawal  of  the  blood  from  the 
body.  As  the  result  of  this  entanglement  the  corpuscles  are  collected  into  a  dark- 
colored,  jelly-like  mass,  the  blood-clot  or  crassamentum ,  that  separates  from  the  sur- 
rounding clear  straw-colored  serum.  The  latter  possesses  an  alkaline  reaction  and 
a  specific  gravity  of  1028.  The  serum  closely  resembles  the  liquor  sanguinis,  con- 
taining about  ten  per  cent,  of  solid  substances,  of  which  about  three-fourths  are  pro- 
teids — serum-albumin,  serum-globulin,  and  fibrin-ferment,  the  latter  replacing  the 
fibrinogen  present  in  the  plasma  before  coagulation  occurs. 

Blood-Crystals. — The  chief  constituent  of  the  red  cells,  the  hemoglobin,  prob- 
ably exists  within  the  corpuscles  as  an  amorphous  mass  in  combination  with  other 
substances  (Hoppe-Seyler)  from  which  it  must  be  freed  by  solution  before  crystal- 
lization can  occur.  After  laking,  the  coloring  matter  of  the  blood,  in  the  form  of 
oxyhemoglobin,  separates  into  microscopic  crystals  that  belong  to  the  rhombic  sys- 
tem,  usually  appearing   as    elongated    rhombic  or    rectangular    plates   (Fig.    643). 

1  Proceedings  Boston  Soc.  Nat.  History,  vol.  xxix,  1900. 

2  Anatomischer  Anzeiger,  Bd.  xxv.,  1904. 


THE    BLOOD.  681 

When  unusually  large  or  superimposed  they  exhibit  the  characteristic  crimson  hue, 
but  when  single  and  small  the  hemoglobin  crystals  are  colorless  or  of  a  faint  greenish- 
yellow  tint.  On  mixing  dried  blood  with  a  few  grains  of  sodium  chloride  and  a  small 
quantity  of  acetic  acid  and  heating  until  bubbles  appear,  minute  brown  crystals  are 
formed  in  large  numbers.  These  are  known  as  TeichmanrC  s  or  hemin  crystals  and  re- 
present one  of  the  products  derived  from  the 

reduction    of   hemoglobin.      Being  yielded  by  Fig.  643. 

blood  from  various  sources,  they  are  indica- 
tive only  of  the  presence  of  blood  and  are 
valueless  in  differentiating  the  blood  of  man 
from  that  of  other  animals.  In  blood-clots 
of  long  standing  minute  hematoidin  crystals 
often  appear  as  yellowish-red  plates.  This 
substance  is  likewise  a  reduction-product  of 
hemoglobin. 

The  Colored  Blood-Cells.— The  ma- 
ture colored  blood -cells,  erythrocytes,  or  red 
corpuscles,  of  man  and  other  mammals  (ex- 
cept those  of  the  camel  family,  which  are 
elliptical  in  outline)  are  small,  biconcave, 
circular,  nonnucleated  discs,  with  smooth 
contour  and  rounded  edges.  When  viewed 
by  transmitted  light,  the  individual  ' '  red  ' ' 
cells  possess  a  pale  greenish-yellow  tint,  and 
only  when  they  are  collected  in  masses  or 
superimposed  in  several  layers  is  the  distinc- 
tive blood-color  evident.  The  peculiar  form 
of  the  corpuscle — biconcave  in  the  centre  and  biconvex  at  the  periphery — 
renders  accurate  focussing  of  all  parts  of  its  broader  surface  in  one  plane  impossible  ; 
hence  under  the  high  amplification  necessary  for  their  satisfactory  examination, 
the  entire  cells  are  never  sharply  defined  and,  according  to  focal  adjustment, 
appear  either  as  light  rings  enclosing  dark  centres  or  vice  versa.  Viewed  in 
profile,  the  thicker  convex  marginal  areas  are  connected  by  the  thinner 
concave  centre,  the  corpuscle  presenting  a  general  figure  somewhat  resembling 
a  dumb-bell. 

After  fresh  blood  has  been  distributed  as  a  thin  layer  and  allowed  to  remain 

unshaken  for  some  time,  the  red  cells  exhibit  a  peculiar  tendency  to  become  arranged 

in  columns,  with  their  broad  surfaces  in  contact,  similar 

Fig.  644.  to  piles  or  rouleaus  of  coin   (Fig.  646).      Agitation  dis- 

-^\__  -^  perses  the  corpuscles,  which,  however,  may  resume  their 

/        ^^  former  grouping  when  again  undisturbed.      The  columns 

^  S     A     ^  may  join,    one  another  until  a  net-work    of   rouleaus    is 

.*»     "      &      ^,.  formed.      If  the  stratum  of  blood  be  thin,   the  red  cells 

I  I    4*       J  '        j)      usually  later  separate,  but  they  may  retain  their  columnar 

"f        ^       %  J      '    srouPin£- 
\      /  y  **    \ 

<*  4»,        s  The  long-accepted  biconcave  discoidal  form  of   the  mam- 

^  ^     0s,  ^^  •  malian  erythrocytes   has  been  questioned  by  Dekhuyzen  1  and, 

•»  <m^  more  recently,  by  Weidenreich  2  and  by  F.  T.  Lewis,3  who  be- 

lieve that  the  normal  form  of  the  red  blood-cells  is  cup-shaped, 
Hemin  crystals  from  human         similar  to  a  sphere  more  or  less  deeply  indented,  thus  reviving 
blood,     x  250.  tne  conCeption  held  by  Leeuwenhoek  nearly  two  centuries  ago. 

Although  such  cupped  corpuscles  are  familiar,  they  are  generally 
regarded  as  changed  cells  resulting  from  modification  of  the  density  of  the  plasma.  The  posi- 
tive testimony  of  so  careful  an  observer  as  Lewis  as  to  the  occurrence  of  the  cup-shaped  red  cells 
within  the  circulation  during  life  entitle  these  views  to  consideration.4 

1  Anatomischer  Anzeiger,  Bd.  xv.,  1899. 

2  Archiv.  f.  mikros.  Anatom.,  Bd.  lxi.,  1902. 

3  Journal  of  Medical  Research,  vol.  x.,  1904. 

1  A  critical  review  concerning  the  form  and  structure  of  the  red  cells  is  given  by  Weiden- 
reich in  Ergebnisse  d.  Anat.  u.  Entuick.,  Bd.  xiii.,  1904. 


682 


HUMAN    ANATOMY. 


Dresbach1  has  recorded  the  presence  of  elliptical  red  cells  in  the  blood  of  an  apparently 
healthy  mulatto.     The  oval  corpuscles,  which  measured  .010  mm.  by  .004  mm.,  were  approxi- 
mately constant  in  size,  slightly  biconcave,  and  constituted  ninety  per  cent,  of  all  the  red  cells. 
They  were  observed  over  a  period  of  four  months,  during  which  time  the  number  of  erythro- 
cytes and  leucocytes  and  the  amount  of 
Fig.  645. 


£>, 


o 


6 


9* 


hemoglobin  were  normal.  Dresbach  con- 
cludes that  the  oval  form  was  not  an  arti- 
fact, but  probably  due  to  developmental 
variation. 


Red  cells  from  human  blood  ;  leucocyte  seen 
near  centre  of  field.     X  865. 


The  average  diameter  of  the  red 
\      /"~^{ "^1      )V_/'^~\V_ii>''     )    s-  blood-cells    of    man    is    .0078    mm. 

ftff^f    )  P=<     C    Js~^X  v        (irsVu-  in0>   some    corpuscles   meas- 

uring as  little  as  .0045  mm.  and 
others  as  much  as  .0095  mm.  Their 
average  thickness  is  about  .0018  mm. 
It  is  probable  that  the  average  diam- 
eter is  uninfluenced  by  sex  and  is 
constant  for  all  races,  although  ac- 
W         /"ijv^^7  ^-T">  /T^j^Ji  cording  to  Gram,  the  size  of  the  cor- 

/  /""Y<JW;  f  {  ^\  <*~^t*^    \^/x^/     ^  puscles  is  somewhat    greater  in   the 

inhabitants  of  northern  countries. 
The  number  of  red  cells  normally 
contained  in  one  cubic  millimeter  of 
blood  is  approximately  5,000,000  in 
the  male  and  something  less  (4,500,- 
000)  in  the  female.  The  number  of 
corpuscles  is  practically  the  same 
whether  the  blood  be  taken  from  the  arteries,  capillaries,  or  veins,  but  is  lower  in  the 
blood  from  the  vessels  of  the  lower  extremity  than  of  the  upper,  probably  owing  to 
the  greater  proportion  of  plasma  in  the  more  dependent  parts  of  the  body.  Within 
the  first  day  after  birth,  the  number  of  erythrocytes  is  normally  very  high;  in  ad- 
vanced old  age  it  is  usually  diminished. 

In  general,  the  red  blood-cells  of  mammals  are  small  and  their  size,  which  greatly  varies  in 
different  orders,  bears  no  relation  to  that  of  the  animal.  The  corpuscles  of  man,  which  are  among 
the  largest  and  exceeded  by  only  those  of  the  elephant  (.0094  mm.)  and  the  two-toed  sloth 
(.0091  mm. ),  are  approximated  by  those  of  the 

guinea-pig  (.0075  mm.),  dog  (.0073  mm.),  rab-  Fig.  646. 

bit  (.0069  mm.),  and  cat  (.0065  mm.).     Those 
of     many    familiar     mammals    are    distinctly       r 
smaller,  as  the  hog  (.006  mm.),  horse  (.0056  .-  _ '. 

mm.),  sheep  (.005  mm.)  and  goat  (.004  mm. ). 
The  smallest  mammalian  corpuscles  are  those  of 
the  musk-ox,  with  a  diameter  of  only  .0025  mm. 

It  is  obvious  that  a  positive  differentiation 
of  human  blood  from  that  of  some  of  the  do- 
mestic animals,  based  on  the  measurement  of 
the  red  cells,  is  uncertain  and  often  impossible. 
The  application  of  the  "biological"  test  has 
placed  a  much  more  reliable  and  even  specific 
means  in  the  hands  of  the  medico-legal  expert. 
This  test  depends  upon  the  fact,  demonstrated 
by  Bordet,  Uhlenmuth,  and  others,  that  the 
blood-serum  of  an  animal  that  has  been  repeat- 
edly injected  with  small  quantities  of  human 
blood  will  produce  a  distinct  cloudy  precipitate 
or  turbidity  when  added  to  a  dilute  solution 
of  human  blood,  but  will  yield  no  result  when 

added  to  similar  solutions  of  blood  from  other  animals.     An  important  advantage  of  this  test 
is  that  even  when  the  blood  is  putrid,  contaminated,  or  derived  from  old  dried  clots,  the  char- 
acteristic changes  occur.     Certain  exceptional  disturbing  conditions,  such  as  the  presence  of 
1  Science,  March  18,  1904,  and  March  24,  1905. 


"&'' 


% 


Human  blood  corpuscles 
seen  among  the  red  cells, 
grouped  in  rouleaus.    X  625. 


THE   BLOOD. 


683 


monkey's  blood,  human   lachrymal  or  nasal   secretion,  being  eliminated,  a  positive  reaction 
with  the  serum-test  is  strong  evidence  of  the  presence  of  human  blood. 

The  nonnucleated  condition  of  the  mature  erythrocytes  is  the  distinguishing  characteristic 
of  mammalian  blood  as  contrasted  with  the  colored  corpuscles  of  other  vertebrates,  since  even 
in  the  exceptional  oval  red  cell  of  the  camel  family  the  nucleus  is  wanting.  The  mammalian 
red  corpuscles,  however,  must  be  regarded  as  a  secondary  deviation  from  the  fundamental  type 
represented  by  the  oval  nucleated  erythrocyte  of  the  other  vertebrates,  the  nucleated  embryonic 
red  cell  losin°-  its  nucleus  as  maturity  is  acquired.  In  general,  the  oval  nucleated  red  cells  are 
larger  than  the  mammalian  nonnucleated  discs.  The  largest  erythrocytes  are  found  in  the 
tailed  amphibians,  those  of  the  amphiuma,  the  largest  known,  attain  the  gigantic  length  of  .080 
mm.,  and  are  approximately  ten  times  as  large  as  the  human  red  blood-cell. 

The  structure  of  the  red  blood-cell  has  long  been  and  still  is  a  subject  of  dis- 
cussion, two  opposed  views  finding  ardent  supporters.  According  to  the  one,  held 
by  Schaefer,1  Weidenreich,  and  others,  the  erythrocyte  consists  of  a  membranous 
external  envelope  inclosing  the  colored  fluid  contents.  On  the  other  hand,  Rollett 
and  many  others  regard  the  corpuscle  as  composed  of  an  insoluble  uniform  spongy 
stroma  of  great  delicacy,  occupied  by  the  coloring  matter  or  hemoglobin.  Although 
no  definite  envelope  is  present,  in  the  sense  of  a  distinct  cell-membrane,  it  is  highly 
probable  that  a  peripheral  condensation  of   the  stroma  exists.      The  fact  that  the 

Fig.  647. 


Nucleated  amphibian  red  blood-cells;  A,  from  newt ;  i?,  from  amphiuma.     X  750. 


fragments  into  which  the  red  blood-cells  may  be  broken  up  after  certain  treatment, 
as  by  heating,  retain  the  appearance  and  structure  identical  with  the  larger  original 
cell,  is  strong  evidence  that  the  hemoglobin  has  not  escaped  and,  therefore,  does 
not  exist  in  a  fluid  condition  within  the  cell,  notwithstanding  the  ingenious  but 
scarcely  convincing  explanations  of  the  phenomena  advanced  by  the  supporters  of 
the  vesicular  structure  of  these  cells.  The  further  evidence  afforded  by  those 
parts  of  the  corpuscles  that  remain  after  abstraction  of  the  hemoglobin  by  water, 
ether,  and  other  reagents,  points  to  the  existence  of  a  distinct  stroma,  the  thicker 
edges  of  which  appear  in  profile  as  outlines  of  the  "ghosts"  that  then  represent 
the  former  colored  cells. 

The  erythrocytes  are  extremely  sensitive  to  a  wide  range  of  reagents  and  conditions  and, 
therefore,  require  great  care  in  their  collection  and  examination  if  distortions  are  to  be  avoided. 
Exposure  to  even  a  current  of  air  often  suffices  to  produce  conspicuous  changes  in  the  red  blood- 
cells.  Alterations  in  form  may  be  grouped  into  those  resulting  from  the  action  of  solutions  of 
lower  and  of  higher  density  than  that  of  the  normal  plasma.  The  latter  is  conveniently  sub- 
stituted by  an  .85  per  cent,  solution  of  sodium  chloride.  If  the  proportion  of  salt  be  grad- 
ually reduced,  the  corpuscles  show  evidences  of  swelling,  at  first  by  losing  their  concavity  on 
one  side  and  later,  as  the  density  of  the  reagent  approached  that  of  water,  assuming  the 
spherical  form  and  parting  with  the  hemoglobin  and  becoming  colorless.  On  the  other  hand, 
1  Anatomischer  Anzeiger,  Bd.  xxvi.,  1905. 


684  HUMAN    ANATOMY. 

when  subjected  to  saline  solutions  stronger  than  the  "normal,"  the  exterior  of  the  corpuscles 
becomes  irregular  and  beset  with  knob-like  projections  or  spines.  When  the  concentration 
of  the  medium  is  increased,  the  "crenation"  gives  place  to  marked  shrinkage  and  distortion 
until  the  cells  lose  all  resemblance  to  their  normal  form. 

Upon  treatment  with  water,  aqueous  dilutions  of  acetic  acid,  ether,  and  other  reagents,  the 
erythrocytes  are  promptly  decolorized  by  the  extraction  of  the  hemoglobin.  An  interesting 
modification  of  the  phenomenon  may  be  produced  by  solutions  of  tannic  acid  or  potassium 
bichromate  of  varying  strength.  When  the  reaction  is  vigorous,  the  decomposed  hemoglobin 
is  caught  within  the  cell  and  appears  as  a  mass  somewhat  resembling  a  nucleus.  When  the 
reaction  is  feeble,  as  with  very  weak  solutions,  the  hemoglobin  is  less  suddenly  precipitated,  and 
appears  as  a  minute  projection  attached  to  one  part  of  the  exterior  of  the  decolorized  corpuscle. 
Alkaline  solutions  effect  the  complete  destruction  of  the  red  cells.  Among  the  reagents 
employed  in  histological  investigations,  osmic  acid  (i  per  cent.)  deserves  especial  confidence  as 
preserving  the  form  of  the  red  corpuscles.  Fixation  by  heat,  so  commonly  used  in  the  prepara- 
tion of  blood  specimens  for  clinical  examinations,  produces  alterations  and  often  marked  changes 
in  the  red  cells,  and,  therefore,  is  unsuitable  for  histological  study  of  these  elements.  Attenua- 
tion of  the  central  parts  of  the  cells  produces  appearances  that  have  been  mistaken  for  a  nucle- 
ated condition  of  the  erythrocytes.  Upon  cautious  application  of  heat,  with  precautions  against 
evaporation  and  drying,  the  corpuscles  extrude  portions  of  their  substance  which,  after  separation, 
resemble  miniature  red  cells. 

The  Colorless  Blood-cells. — It  may 
at  once  be  emphasized  that  the  colorless  cells 
observed  within  the  blood  are  only  incident- 
ally related  to  the  red  cells  and,  further,  that 
they,  in  part  at  least,  primarily  circulate  within 
the  lymph-vascular  system,  from  which  they 
are  poured  into  the  blood. 

When  examined  in  fresh  and  unstained 
preparations,  the  colorless  cells  or  leuco- 
cytes appear  as  pale  nucleated  elements 
which,  by  their  pearly  tint  and  refracting 
properties,  are  readily  distinguished  from  the 
much  more  numerous  surrounding  erythro- 
cytes. Their  shape  is  very  variable,  but 
when  first  withdrawn  from  the  body  is  usually 
no nSftaS^bSSd!^  smaitfymphlcytej"      irregularly  spherical  or  oval.      When  placed 

b,  large  lymphocyte  or  mononuclear  leucocyte;      on  a  vvarmed    slide  and    maintained   at    the 

c,  transitional  leucocyte ;    a,  polymorphonuclear  r     i       i        1  r     i  n 

leucocytes ;  e,  eosinophiie ;  /,  red  cells,    x  900.        temperature  of  the  body,  many  01  these  cells 

soon  exhibit  amoeboid  motion,  whereby  are 
produced  not  only  alterations  in  their  form,  but  often  also  changes  in  their  actual 
position. 

A  nucleus  is  always  present,  but  may  be  obscured  in  the  contracted  spherical 
condition  of  the  cell  by  the  overlying  granular  cytoplasm.  In  the  expanded  con- 
dition, as  when  the  cell  is  undergoing  amoeboid  change,  the  nucleus  is  very  evi- 
dent and  the  cytoplasm  often  differentiated  into  a  homogeneous  peripheral  zone 
(exoplasm)  and  a  central  granular  area  (endop/asm)  surrounding  the  nucleus.  A 
distinct  cell-wall  is  absent,  although  it  is  probable  that  a  slight  peripheral  condensa- 
tion serves  to  outline  the  corpuscle.  That  such  condensation  does  not  constitute  a 
definite  envelope  is  shown  by  the  readiness  with  which  foreign  particles  may  be  taken 
into  the  body  of  the  cell. 

Although  the  size  of  the  colorless  corpuscles  varies  with  the  type  of  the  cell,  as 
presently  described,  in  general  the  diameter  of  these  elements  is  larger  than  that  of 
the  erythrocytes,  and  is  commonly  from  .010-012  mm.  Their  number  is  much  less 
than  that  of  the  red  corpuscles,  the  usual  ratio  between  the  white  and  red  cells  being 
about  1 :  600.  Even  within  physiological  limits  this  ratio  varies  considerably,  from 
5000  to  10,000,  with  an  average  of  7500,  white  cells  being  normally  found  in  one 
cubic  millimeter  of  blood. 

Critical  examination  of  the  colorless  cells,  after  fixation  and  staining,  has  shown  that  among 
the  elements  collectively  designated  as  the  "white  cells"  or  "leucocytes,"  five  varieties  are 
usually  present  in  normal  blood.     Since  the  recognition  of  these  forms  is  sometimes  of  practical 


THE   BLOOD.  685 

importance,  a  brief  resume^  of  their  characteristics,  based  on  the  descriptions  of  Ehrlich  and  of 
Da  Costa,1  may  appropriately  here  find  place. 

It  should  be  noted  that  the  differentiation  of  these  cells  is  founded  upon  not  only  their 
morphological  characters,  but  also  the  behavior  of  the  granules  embedded  within  their  cyto- 
plasm when  subjected  to  certain  combination  stains.  A  generation  ago  Ehrlich  divided  the 
aniline  dyes  into  three  groups — acid,  basic,  and  neutral.  The  first  includes  such  dyes  as  acid 
fuchsin,  orange  G  or  eosin,  in  which  the  coloring  principle  acts  or  exists  as  an  acid  and  exhibits 
an  especial  affinity  for  the  cytoplasm.  The  second  group,  the  basic  stains,  includes  dyes,  as 
hematoxylin,  methylene-blue,  methyl-violet,  methyl-green  or  thionin,  in  which  the  coloring  prin- 
ciple exists  chemically  as  a  base  in  combination  with  a  colorless  acid  and  particularly  affects  the 
chromatin  ;  hence,  such  are  nuclear  stains.  Neutral  dyes,  produced  by  mixture  of  solutions  of 
an  acid  and  a  basic  stain,  have  a  selective  affinity  for  certain  so-called  neutrophilic  granules. 

Assuming  that  the  blood-film  has  been  fixed  by  heat  and  tinged  with  Ehrlich's  "triacid 
stain"  (a  combination  of  solutions  of  acid  fuchsin,  orange  G,  and  methyl-green)  the  following 
varieties  of  colorless  cells  are  distinguishable  in  normal  blood  : 

1.  Small  Lymphocytes. — These  are  non-granular  cells,  with  an  average  diameter  of  .0075 
mm.  or  about  that  of  the  erythrocytes,  distinguished  by  a  large  deeply  staining  nucleus  that 
occupies  almost  the  entire  cell.  The  meagre  cytoplasm  is  reduced  to  a  narrow  peripheral  zone, 
so  inconspicuous  that  it  may  be  overlooked.  The  small  lymphocytes,  which  constitute  from 
20-30  per  cent,  of  all  the  white  corpuscles,  are  the  most  common  derivative  from  the  lymphoid 
tissues. 

2.  Large  Lymphocytes,  or  Mononuclear  Leucocytes. — These  elements,  about  .012  mm.  in 
diameter,  possess  a  relatively  small  round  or  oval  nucleus,  which  is  usually  eccentrically  placed 
and  so  poor  in  chromatin  that  it  stains  faintly.  The  cytoplasm  is  non-granular  and  comparatively 
large  in  amount. 

3.  Transitional  Leucocytes. — Assuming  that  the  lymphocytes  and  leucocytes  are  related 
and  not  distinct  elements,  the  transitional  forms  represent  the  developmental  stage  linking  the 
large  lymphocytes  with  the  mature  leucocytes.  Their  distinguishing  feature  is  the  indented  or 
kidney-shaped  nucleus  which  usually  occupies  an  eccentric  position  within  the  non-granular 
cytoplasm.  The  latter,  as  well  as  the  diameter  of  the  transitional  forms,  corresponds  with  that 
of  the  large  mononuclear  leucocyte. 

4.  Polymorphonuclear  Leucocytes. — These  represent  by  far  the  most  common  type  of 
white  cells,  of  which  they  constitute  about  70  per  cent.  Their  diameter  is  approximately  .010 
mm.,  hence  they  are  somewhat  smaller  than  the  transitional  forms,  but  larger  than  the  red  cells. 
Their  cytoplasm  is  relatively  large  in  amount  and  contains  fine  neutrophilic  granules.  On 
account  of  the  great  diversity  of  the  forms  that  they  assume,  the  nuclei  are  very  conspicuous 
features  of  this  type  of  leucocyte.  At  first  sight  the  nuclei  appear  multiple;  closer  examination, 
however,  shows  the  seemingly  distinct  nuclei  to  be  connected  by  delicate  processes,  so  that, 
although  exceptionally  two  or  more  isolated  nuclei  exist  and  the  cells  are  truly  polynuclear, 
their  actual  condition  is  appropriately  designated  as  polymorphonuclear. 

5.  Eosinophils. — Leucocytes  of  this  type  are  conspicuously  distinguished  by  the  coarse, 
highly  refractive  granules  within  the  cytoplasm  that  display  an  especial  affinity  for  acid  dyes, 
particularly  for  eosin.  These  resemble  the  polymorphonuclear  leucocytes  in  size  (.010  mm.) 
and  in  the  character  of  their  nuclei,  the  latter,  however,  in  general  being  less  distorted  and 
commonly  eccentrically  placed.  The  eosinophiles  are  prone  to  rupture,  after  which  the  pale 
nucleus  lies  in  the  midst  of  a  swarm  of  brightly  tinged  Granules. 

Although  other  types  of  colorless  cells,  as  myelocytes  and  mast  cells,  are  of  clinical  interest, 
they  do  not  occur  in  normal  blood  and,  hence,  need  not  be  here  discussed.  An  occasional  addi- 
tional type  of  leucocyte,  the  basophile  cells,  is  rarely  present  in  normal  blood.  These  elements 
resemble  the  polymorphonuclear  leucocytes,  but  are  distinguished  from  the  latter  by  the  presence 
within  the  cytoplasm  of  closely  packed  fine  granules  that  possess  a  strong  affinity  for  basic  dyes. 

In  the  foregoing  grouping  the  varieties  of  white  cells  are  regarded  as  different  stages  of 
elements  genetically  related  and  derived  from  the  same  sources— a  view  supported  by  the  early 
development  of  the  leucocytes.  It  should  be  mentioned,  however,  that  Ehrlich  and  many  other 
hematologists  consider  the  lymphocytes  and  the  leucocytes  as  entirely  distinct  elements,  believing 
the  former  to  be  derived  from  lymphoid  tissues  and  the  leucocytes  exclusively  from  bone-marrow. 
Accordingly,  the  large  lymphocytes  and  the  large  mononuclear  leucocytes  are  of  different  nature, 
although,  as  universally  admitted,  their  assumed  differentiation  is  at  best  uncertain.  The  presence 
of  all  forms  of  white  cells  in  the  circulation  of  the  embryo  long  before  the  appearance  of  bone- 
marrow  (Ebner)  seems  conclusive  evidence  that  the  origin  of  the  leucocytes  is  not  limited  to  the 
marrow  tissue. 

The   Blood   Plaques. — In  addition  to  the  erythrocytes  and  leucocytes,    the 
blood  of  man  and  other  mammals  regularly  contains  small  bodies,  the  blood  plaques 
1  Clinical  Hematology.     Phila.,  1901. 


686  HUMAN    ANATOMY. 

or  blood  platelets.  As  they  are  extraordinarily  sensitive  to  exposure,  even  to  entire 
disappearance,  special  precautions  are  necessary  to  insure  their  presence  in  an  unal- 
tered condition  in  preparations  examined.  If  blood  be  drawn  directly  into  and  mixed 
with  a  drop  of  .7  per  cent,  salt  solution,  or,  still  better,  into  one  of  weak  osmic  acid 
solution,  the  blood  plaques  appear  as  round  or  oval  discs,  from  .002-. 004  mm.  in 
diameter,  usually  somewhat  less  than  one-third  of  the  size  of  the  red  cells.  From 
these  they  further  differ  in  being  colorless  and  devoid  of  hemoglobin  and  in  staining 
readily  in  very  dilute  solutions  of  methyl-violet.  The  blood  plaques  are  homogeneous 
or  faintly  granular,  nonnucleated,  never  exhibit  amoeboid  movement,  and  may  be 
directly  observed  as  free  bodies  circulating  within  the  vessels.  On  withdrawal  from 
the  latter,  without  precautions  for  their  preservation,  they  at  once  collect  in  irregular 
masses  and  undergo  disintegration,  their  remains  usually  being  centres  from  which 
radiate  the  fibrillar  of  the  fibrin  net-works.  Notwithstanding  the  attention  bestowed 
upon  these  bodies,  the  source  and  significance  of  the  blood  plaques  are  still  unde- 
termined, although  numerous  theories  have  been  advanced.      Their  source  has  been 

variously  attributed    to    disintegration    of   the 
Fig.  649.  .  leucocytes,    to  extrusion    from    the  red    cells, 

to  precipitation  of  globulin  or  to  destruction 
of  the  endothelial  lining  of  the  vessels.  None 
of  these  assumptions  can  be  regarded  as  es- 
tablished, or  even  probable,  in  view  of  their 
;     ■!  constant  presence  and  large  normal  quota — 

^  an  average   of    300,000  plaques  in  one  cubic 

millimeter  of  blood. 
.■-" ■".>  Granules. — In   addition   to   the   corpus- 

'  W  cles  and  the  plaques,  extremely  minute  gran- 

(S®  @  ules    occur    in    varying    numbers    in    normal 

O®©  human  blood.     The  nature  of  these  particles 

differs.  Some  are  undoubtedly  finely  divided 
fat;  others,  described  by  H.  F.  M  tiller  under 
the  name,  hemoconia,  are  of  uncertain  compo- 
sition,   but  not  fatty;  while  a  certain  propor- 

Human  blood,  showmerred  cells  and  •        •  i     11  '    i      •        i  r  .1        t   •  - 

blood  plaques,    x  625.  tion  is  probably  derived  from  the  disintegration 

of  endothelial  and  blood-cells.  The  destruc- 
tion of  the  latter  is  accountable  for  the  minute  particles  of  pigment  that  are  constant, 
if  not  numerous,  constituents  of  the  circulation. 

DEVELOPMENT  OF  THE  BLOOD-VESSELS  AND  CORPUSCLES. 

The  earliest  blood-vessels  appear  within  the  extra  embryonic  mesoblast  covering 
the  vitelline  sac  and,  therefore,  beyond  the  limits  of  the  embryo  proper  and  entirely 
independent  of  the  heart  and  axial  trunks.  In  the  lower  mammals,  the  formation 
of  the  primary  vessels  takes  place  towards  the  periphery  of  a  limited  field,  known  as 
the  vascular  area,  that  encircles  only  a  portion  of  the  vitelline  sac;  in  man  the 
limited  proportions  of  the  latter  enable  the  net-work  of  developing  blood-channels  to 
extend  completely  over  the  vesicle,  so  that  the  vascular  area  becomes  coextensive 
with  the  yolk  sac.  Although  the  earliest  stages  in  the  formation  of  the  primary 
blood-vessels  have  never  been  observed  in  man,  since  the  vessels  were  already 
present  over  the  vitelline  sac  in  the  youngest  embryo  so  far  examined,  it  is  probable 
that  the  development  of  the  human  vascular  tissues  is  essentially  the  same  as  that 
seen  in  other  mammals. 

In  the  rabbit,  the  first  indications  of  the  developing  blood-vessels  are  cords  or 
groups  of  spherical  cells  that  appear  within  the  deeper,  later  splanchnic,  layer  of  the 
mesoblast  covering  the  vitelline  sac.  These  tracts  become  larger  in  consequence 
not  only  of  proliferation,  but  also  of  separation  of  the  component  cells.  The  meso- 
blastic  elements  surrounding  the  tracts  soon  become  disposed  as  enclosing  walls, 
within  which  the  separated  cells,  now  suspended  in  a  clear  fluid  that  has  meanwhile 
appeared,  represent  the  earliest  blood-cells. 

The  channels  thus  established  unite  into  a  net-work  of  primary  blood-vessels  that 
at  first  occupies  the  periphery  of  the  vascular  area,  but  later  extends  towards  the 


DEVELOPMENT  OF  BLOOD-VESSELS  AND  CORPUSCLES.       687 


embryo  and,  after  the  appearance  of  the  large  converging  trunks,  the  vitelline  veins 
and  arteries,  joins  the  intra-embryonic  trunks  that  coincidently  have  been  formed. 

Although  the  generally  accepted  current  views  relating  to  the  independent  origin 
of  the  primary  blood-vessels  within  the  vascular  area  have  not  escaped  challenge,  it 
may  be  regarded  as  established  that  the  development  of  subsequent  blood-vessels 
proceeds  from  the  cells  constituting  the  walls  of  pre-existing  channels.  The  walls 
of  the  growing  capillaries  consist  of  delicate  endothelial  plates  from  which  pointed 
sprouts  grow  into  the  surrounding  tissue  (Fig.  651).  These  outgrowths,  direct  pro- 
longations of  the  cytoplasm  of  the  endothelial  cells,  are  at  first  solid,  but  later  become 
hollowed  out  by  the  gradual  extension  of  the  lumen  of  the  capillary.  Vascular  loops 
are  often  formed  by  the  meeting  and  fusion  of  the  outgrowths  proceeding  in  opposite 
directions,  the  communication  being  established  by  the  final  disappearance  of  the  sep- 
tum in  consequence  of  the  extension  of  the  lumen  of  the  parent  vessels.  At  first  rep- 
resented by  only  a  single  layer  of 

endothelial  cells,  the  walls  of  the  Fig.  650. 

larger  blood-vessels  become  rein- 
forced by  the  additional  layers 
derived  from  the  surrounding 
mesoblast. 

Development  of  the 
Erythrocytes. — The  first,  and 
for  a  time  the  only,  blood-cells 
present  within  the  embryo  are 
the  primary  nucleated  erythro- 
cytes derived  probably  directly 
from  the  mesoblastic  elements 
within  the  angioblastic  areas  in 
which  the  earliest  vessels  appear. 
These  cells,  separated  by  the 
colorless  plasma  which  appears 
between  them  and  in  which  they 
henceforth  float,  undergo  mitotic 
division,  producing  nucleated 
elements  that,  in  turn,  give  rise 
to  other  corpuscles.  The  pri- 
mary erythrocytes  are  spherical, 
nucleated,  and  larger  (about  .012 
mm.  in  diameter)  than  the  adult 
red  cells.  At  first  their  cyto- 
plasm is  colorless  and  slightly 
granular,  but  soon  becomes  ho- 
mogeneous and  tinged  with 
hemoglobin. 

After  the  earlier  fcetal 
months,  during  which  prolifera- 
tion of  the  blood-cells  occurs 
in  all  parts  of  the  circulation,  the  corpuscles  engaged  in  division  withdraw  to 
localities  in  which  the  blood-current  is  sluggish  and,"  therefore,  favorable  for  mitosis. 
Such  localities  are  particularly  the  liver,  spleen,  and  bone-marrow,  the  large  capil- 
laries and  tissues  of  which  afford  temporary  resting  places  during  proliferation.  After 
a  time  the  primary  erythrocytes  lose  their  nuclei,  diminish  in  size,  and  assume  their 
definite  form.  These  changes  begin  during  the  second  fcetal  month,  more  and  more 
nonnucleated  discoidal  red  cells  appearing  as  gestation  advances,  so  that  at  birth 
almost  all  the  nucleated  erythrocytes  have  disappeared  from  the  circulation. 

Since  the  red  cells  possess  only  a  limited  vitality,  their  constantly  occurring 
death  requires  the  production  of  new  corpuscles.  Preceding  the  development  of  the 
spleen  and  bone-marrow,  the  liver  is  the  principal  centre  of  blood-formation.  Later 
the  splenic  and  marrow  tissues  share  this  function,  while  after  birth  the  red  bone- 
marrow  is  the  chief  seat  in  which  the  continual  additions  of  new  erythrocytes  necessary 


Surface  view  of  vascular  area  of  chick  embryo  with  twelv 
somites  (29  hours)  ;  net-work  of  developing  blood-vessels,  mos 
distinct  in  periphery  of  area,  is  connected  with  vitelline  vein 
from  embryo  by  faint  channels  ;  cephalic  segment  of  neura 
tube  shows  brain-vesicles  and  eye-buds  ;  caudal  segment  stil 
widely  open.     X  16. 


688  HUMAN   ANATOMY. 

to  maintain  the  normal  quota  are  made.      The  production  of  the  new  red  cells  within 
the  marrow  proceeds  from  colorless  nucleated  elements,   the  erythroblasts,  that  by 
division  give  rise  to  the  nucleated  erythrocytes  or  normoblasts  which,  upon  the  appear- 
ance of    hemoglobin  and  the 
Fig.  651.  disappearance  of  their  nuclei, 

are  transformed  into  the  usual 
red  cells,  and  as  such  enter 
the  circulation. 

The  disappearance  of  the 
nucleus  of  the  normoblasts  has 
long  been  a  subject  of  discus- 
sion and  speculation.  Accord- 
ing to  the  older  view  —  still, 
however,  accepted  by  many — 
the  nucleus  is  extruded  from 
the  erythrocyte  and  under- 
goes disintegration,  thus,  in 
the  opinion  of  some,  supply- 
ing the  source  of  the  blood 
plaques.  According  to  the 
more  recent   views,    held  by 

Developing  blood-vessels  in  embryonal  subcutaneous  tissue ;  Neumann,     K611iker,    Pappen- 

a,   larger  capillary;    b.  young  capillaries;  c,  solid   protoplasmic  1     •        t         i    t-i  j     fi 

outgrowths  forming  new  vessels,   x  300.  heim,  lsra;l,  Ebner,  and  others, 

the  disappearance  of  the  nu- 
cleus is  due  to  its  solution  and  absorption  within  the  erythrocyte.  Under  normal 
conditions  nucleated  red  cells  or  normoblasts  do  not  occur  in  the  circulation.  After 
severe  hemorrhage  or  in  other  conditions  requiring  unusual  activity  of  the  blood- 
forming  processes,  they  may  be  present  in  large  numbers  until  the  normal  quota  of 
erythrocytes  has  been  once  more  established.  In  view  of  the  constant  presence  of 
erythroblasts  and  nucleated  erythrocytes  within  the  splenic  pulp,  the  spleen  must  be 
regarded  as  an  additional,  although  under  usual  conditions  limited,  source  of  the  red 
blood-cells.  When,  however,  the  necessity  for  rapidly  augmenting  the  number  of 
red  cells  arises,  the  spleen  may  assume  the  role  of  an  active  blood-producing  tissue. 
Since  such  cells  are  found  also  in  the  thymus,  this  body  probably  must  be  included 
among  the  blood-forming  organs  of  early  life.  There  is  no  satisfactory  evidence  that 
the  erythrocytes  are  derived  from  the  colorless  cells  or  from  the  blood  plaques. 

Development  of  the  Leucocytes. — During  the  first  weeks  succeeding  the 
appearance  of  the  primary  red  cells,  the  latter  are  the  only  elements  within  the  circu- 
lation.     In   the  second  fcetal  month,   however,   leuco- 
cytes   appear,   and  henceforth  are  companions  of  the  Fig.  652. 
erythrocytes.      As    already  noted,   the  white  cells  are 
elements  that  primarily  belong   to  the   lymphatic  sys 

tern,    from   which    they    are   poured    into    the   blood-  -_     -=^.®.:-- 

channels.       Genetically    the    red   and   white    cells    are  *?."',©) 

entirely  distinct  and  unrelated.  ■■©       _       £|TC 

Concerning  the  origin  of  the  first  leucocytes  much  (E£        gj       ^U—*/-- 

uncertainty  exists,  although  it  is  generally  assumed  that  j^£  <  ©;.© 

they  arise  from  mesoblastic  cells,  and,  therefore,  to  that  ■©_  V-"  f& 

extent,  share  with  the  erythrocytes  a  common  source.  8 

Suggestive  as  are  the  views  of  Beard,1  Retterer,  Nus- 
baum  and  Prymak,2  and  others,  supporting  the  origin 
of  leucocytes  within  the  early  thymus  in  loco  and  not,  Nucieai 

as  generally  held,  by  invasion  from  the  surrounding  mito'tic  figu 
mesoblast,  they  cannot  be  regarded  as  established.  The 
conclusion  of  Beard,  that  the  first  leucocytes  to  appear  within  the  embryo  owe  their 
production  to  the  metamorphosis  of  the  entoblastic  epithelium  of  the  primary  thymus, 
and  that  the  subsequent  migration  of  the  leucocytes  so  derived  establishes  foci  from 

1  Anatom.  Anzeiger,  Bd.  xviii.,  1900. 

2  Anatom.  Anzeiger,  Bd.  xix.,  1901. 


THE    HEART. 


689 


which  are  developed  the  various  masses  of  lymphoid  tissue  occurring  throughout  the 
body,  has  been  challenged  by  Hammar, '  who  found  leucocytes  in  the  blood  and  con- 
nective tissues  of  the  human  foetus  before  they  appear  in  the  thymus.  In  any  event 
it  is  probable  that  the  first  leucocyte's  originate  as  amoeboid  cells  outside  the  ves- 
sels, which  they  later  enter,  aided  by  their  migratory  powers.  Their  subsequent 
multiplication  is  effected  by  division,  for  the  most  part  mitotic,  of  the  pre-existing 
cells.  This  proliferation  occurs  chiefly  within  the  lymphoid  tissue  throughout  the 
body,  the  lymph-nodules,  spleen  and  bone-marrow  being  the  most  important  local- 
ities. The  germ-centres  of  the  lymph-nodules  (page  936)  are  seats  of  especial 
activity  for  the  formation  of  the  types  of  colorless  cell  known  as  the  mononuclear 
lymphocyte,  although  whether  the  proliferating  cells  originate  within  the  germ- 
centres,  or  only  complete  their  division  in  these  situations  after  being  carried  from 
other  points  (Stbhr),  is  still  unsettled. 

From  the  developmental  standpoint,  the  sharp  separation  of  the  colorless  blood- 
cells  into  lymphocytes  and  leucocytes,  as  insisted  upon  by  Ehrlich  and  his  supporters, 
based  on  the  assumption  that  the  leucocytes  originate  exclusively  within  bone-marrow, 
is  not  well  founded  in  view  of  the  presence  of  all  the  typical  forms  of  white  cells,  in- 
cluding the  polymorphonuclear  leucocytes,  shortly  after  the  first  appearance  of  the 
white  corpuscles  and  long  before 

the  advent  of   the  earliest    bone-  Fig.  653. 

marrow  (Ebner).  For  the  pres- 
ent, at  least,  it  seems  most  reason- 
able to  regard  the  various  forms 
of  the  white  cells  as  constituting 
a  genetic  sequence  in  which  the 
lymphocyte,  leucocyte,  and  eosin- 
ophile  represent  different  stages  in 
the  development  of  elements  hav- 
ing a  common  origin. 

In  addition  to  the  red  blood- 
cells  in  various  stages  of  develop- 
ment and  the  different  types  of 
leucocytes,  peculiar  huge  elements 
early  appear  in  the  embryonic 
blood-forming  organs,  and  after 
birth  in  bone-marrow.  These 
giant  cells,  or  megakaryocytes 
(Howell),  are  distinguished  by 
their  large,  irregularly  lobulated 
but  single  nucleus  from  the  osteo- 
clasts, since  the  nuclei  of  the  latter  are  usually  oval  and  multiple.  The  megakaryo- 
cytes are  often  observed  containing  within  their  substance  the  remains  of  both  white 
and  red  cells;  they  are,  therefore,  regarded  as  phagocytes  upon  which  devolves  the 
removal  of  effete  blood-corpuscles.  Their  origin  is  uncertain,  by  some  (Howell,  van 
der  Stricht,  Heidenhain)  being  referred  to  the  leucocytes,  and  by  others  (Kolliker, 
Kuborn)  to  the  endothelium  of  the  vessels,  while  Ebner  regards  those  within  the  bone- 
marrow  as  probably  derived  from  fixed  connective-tissue  cells  of  the  reticulum.  Nei- 
ther form  of  these  giant  marrow-cells  is  normally  found  within  the  post-natal  circulation. 


Section  of  embryonal  bone-marrow,  showing 
nucleated  erythrocytes,  leucocytes  and  mega- 
karyocyte.    X  625. 


THE  HEART. 

General  Description. — The  heart  is  a  hollow,  muscular  organ  of  a  somewhat 
conical  shape,  situated  in  the  lower  part  of  the  thoracic  cavity,  behind  the  lower  two- 
thirds  of  the  sternum.  It  is  enclosed  within  a  double-walled  serous  sac,  ihepen'car- 
dium,  and  has  a  somewhat  oblique  position  in  the  thorax,  its  base  (basis  cordis)  looking 
upward,  dorsally,  and  to  the  right,  while  its  apex  (apex  cordis)  points  downward,  ven- 
trally,  and  to  the  left.  In  consequence  of  this  obliquity  about  two-thirds  of  the  organ 
lies  to  the  left  and  one-third  to  the  right  of  the  median  plane  of  the  body. 
1  Anatom.  Anzeiger,  Bd.  xxvii.,  1905. 
44 


690 


HUMAN   ANATOMY. 


It  may  be  regarded  as  possessing  two  surfaces,  which  are  not,  however,  distinctly 
separated,  but  pass  into  each  other  with  rounded  edges,  especially  upon  the  left  side. 
One  of  these  surfaces  looks  forward  and  somewhat  upward,  and  is  separated  by  the  peri- 
cardium and  some  loose  areolar  tissue  from  contact  with  the  sternum  and  the  lower 
costal  cartilages,  the  thin  anterior  edges  of  the  lungs  and  pleurae  also  intervening  to 
a  considerable  extent;  this  is  the  ajitero-superior  surface  (facies  sternocostalis),  and 
for  convenience  it  may  be  more  briefly  termed  the  anterior  surface.  The  other,  the 
postero-inferior  or  posterior  surface  (facies  diaphragmatica),  rests  directly  upon  the 
upper  surface  of  the  diaphragm. 

At  about  one-third  of  the  distance  from  the  base  to  the  apex  a  deep  circular 
groove,  more  distinct  upon  the  posterior  surface,  surrounds  the  heart,  separating  an 


Fig.  654. 


Superior  vena  cava 


Systemic  aorta  (aorta) 


Right  auricular 
appendage 


Auriculo-ventricular 
groove 


Line  of  reflection  of 
pericardium 


Ductus  arteriosus 


Pulmonary  aorta 
(pulmonary  artery) 


Conus  arteriosus 


Left  ventricle 


Anterior  aspect  of  heart  hardened  in  situ  ;  probe  1 


sinus  of  pericardium. 


upper  thin-walled  auricular  portion  of  the  organ  from  a  lower  thick-walled  ventricular 
one  ;  this  groove  is  termed  the  auriculo-ventricular  groove  (sulcus  coronarius),  and 
contains  the  proximal  portions  of  the  coronary  vessels  which  supply  the  heart's  sub- 
stance. Extending  towards  the  apex  from  this  groove,  two  other  shallower  grooves 
are  to  be  observed,  one  situated  towards  the  right  side  of  the  anterior  surface  and  the 
other  upon  the  posterior  surface.  These  grooves,  which  also  lodge  portions  of  the 
coronary  vessels,  are  the  anterior  and  posterior  interventricular  grooves  (sulci  longi- 
tudinales),  and  mark  the  line  of  separation  of  the  ventricular  portion  of  the  heart  into 
two  chambers  known  as  the  right  and  left  ve?itricles.  From  the  base  of  the  right  ven- 
tricle a  large  blood-vessel,  thepulmonary  aorta  or  pulmonary  artery,  arises,  while  from 
the  base  of  the  left  ventricle,  and  almost  immediately  posterior  to  the  root  of  the  pul- 
monary aorta,  the  systemic  aorta  takes  its  origin.     The  orifices  by  which  each  of  these 


THE    HEART. 


691 


great  vessels  communicates  with  its  ventricle  are  guarded  by  special  valves  known  as 
the  semilunar  valves. 

The  auricular  portion  of  the  heart  rests  upon  the  posterior  part  of  the  base  of  the 
ventricular  portion,  and  is  best  viewed  from  the  posterior  surface  (Fig.  655),  since 
it  is  almost  completely  hidden  anteriorly  by  the  two  aortas.  Like  the  ventricular 
portion,  it  is  composed  of  two  separate  chambers,  which  are  not,  however,  very 
apparent  on  surface  view.  These  chambers  are  the  right  and  left  auricles,  and  com- 
municate with  the  corresponding  ventricles  by  auriculo-ventricular  orifices  guarded 
by  special  auriculo-ventricular  valves.  From  the  lateral  part  of  the  anterior  sur- 
face of  each  auricle  a  process,  the  aut  icular  appendix,  arises.      These  appendices  are 


Fig.  655. 


Left  common  carotid  artery 
Left  subclavian  artery 


Vestigial  fold 

Sup.  left  pulm.  vein 
Left  auricular 
appendix 


Inf.  left  pulm.  vein 


Coronary  sinus— j& 


Left  ventricle 


Posterior  aspect  of  heart  hardened  in  situ  ;  showing  lines  of  reflection  of  pericardi' 


slightly  flattened  prolongations  of  the  auricles,  and  bend  forward  around  the  bases  of 
the  aortse,  which  they  slightly  overlap  in  front;  they  are  the  only  portions  of  the 
auricles  visible  upon  the  anterior  surface  of  the  heart.  Upon  its  superior  surface  the 
right  auricle  receives  the  termination  of  a  large  venous  trunk,  the  ve?ia  cava 
superior,  which  returns  to  the  heart  blood  from  "the  head,  neck,  upper  extremities, 
and  walls  of  the  thorax  ;  while  upon  its  posterior  surface  is  the  opening  of  another 
large  vessel,  the  vena  cava  inferior,  which  returns  blood  from  the  abdominal  and 
pelvic  walls  and  viscera  and  from  the  lower  limbs.  The  left  auricle  receives  upon 
its  surface  the  four  pulmonary  veins  arranged  in  pairs,  one  pair  situated  towards  the 
left  portion  of  the  auricle  and  the  other  towards  the  right. 


69s 


HUMAN   ANATOMY. 


Position. — The  heart,  may  vary  considerably  in  position  without  being  regarded 
as  abnormal,  but  what  may  be  considered  its  typical  position  with  reference  to  the 
anterior  thoracic  wall  may  be  stated  about  as  follows  :  The  apex  is  situated  behind 
the  fifth  intercostal  space,  about  8  cm.  (3^  in.)  from  the  median  line,  this  position 
being  median  to  and  slightly  below  the  junction  of  the  fifth  costal  cartilage  with  its 
rib.  The  level  of  the  base  may  be  approximately  indicated  by  a  line  drawn  from  a 
point  slightly  above  the  upper  border  of  the  third  costal  cartilage  of  the  left  side, 
about  4.5  cm.  (i3/(  in.)  from  the  median  line  of  the  sternum,  to  a  point  upon  the 
upper  border  of  the  third  costal  cartilage  of  the  right  side,  about  3  cm.  (ij{  in.) 
from  the  middle  line.  If  now  the  left  end  of  the  base-line  be  united  to  the  apex 
point  by  a  line  which  is  slightly  convex  towards  the  left,  and  a  line,  markedly  convex 
towards  the  right,  be  drawn  from  the  right  end  of  the  base-line  to  the  junction  of 
the  seventh  costal  cartilage  of  the  right  side  with  the  sternum  and  thence  to  the 

apex  point,  a  heart-area  will  be  en- 


Fig.  656. 


closed  which  corresponds  to  the  out- 
line of  the  organ  as  seen  from  in 
front. 

Considerable  importance  at- 
taches to  the  location  of  the  auriculo- 
ventricular  and  aortic  orifices  with 
reference  to  the  anterior  thoracic  wall. 
The  right  auriculo-ventricular  ori- 
fice in  a  typical  heart  lies  on  a  level 
with  the  attachment  of  the  fifth  costal 
cartilages  to  the  sternum,  almost  be- 
hind the  median  line  of  that  bone  and 
opposite  the  fourth  intercostal  space, 
while  the  left  auriculo-ventricular 
orifice  is  opposite  the  sternal  end  of 
the  left  third  intercostal  space.  In 
other  words  these  openings  lie  along 
a  line  which  corresponds  with  the 
auriculo-ventricular  groove,  and  this 
may  be  represented  by  a  line  drawn 
from  the  upper  border  of  the  junc- 
tion of  the  seventh  costal  cartilage  of 
the  right  side  with  the  sternum  to  the 
sternal  end  of  the  third  left  costal 
cartilage.  The  right  orifice  is  lo- 
cated upon  the  line  where  it  is  inter- 
sected by  a  line  joining  the  sternal 
ends  of  the  fifth  costal  cartilages, 
while  the  left  one  is  situated  at  its 
upper  end. 

The  systemic  and  pulmonary 
aortic  orifices  are  situated  at  about 
the  level  of  the  attachment  of  the  third  costal  cartilages  to  the  sternum,  the  pulmon- 
ary orifice  being  behind  the  sternal  end  of  the  third  left  cartilage,  while  the  aortic 
orifice  is  behind  the  left  half  of  the  sternum,  a  little  below  and  to  the  right  of  the  pul- 
monary one,  the  two  orifices  overlapping  for  about  one-quarter  of  their  diameters. 
It  is  to  be  noted,  however,  that  the  pulmonary  aorta  is  directed  upward  and  to  the 
left,  while  the  systemic  aorta  inclines  decidedly  towards  the  right  in  the  first  part  of 
its  course;  and  since  the  sounds  caused  by  the  valves  which  guard  the  orifices  are 
carried  in  the  direction  of  the  blood-stream,  auscultation  of  the  pulmonary  semilunar 
valves  may  be  practised  over  the  sternal  end  of  the  second  left  intercostal  space, 
while  that  of  the  systemic  valves  is  best  performed  over  the  sternal  end  of  the  second 
right  space. 

Similarly  the  close  proximity  of  the  areas  of  the  left  auriculo-ventricular  and 
systemic  aortic  orifices,  as  projected  upon  the  thoracic  wall,  might  lead  to  confusion, 


Position  of  heart  and  valves  in  relatioi 
wall.    A,  aortic  valve ;  P,  valve  of  pulmonary 
cuspid  valve  ;  M,  mitral  valve. 


THE    CHAMBERS    OF    THE    HEART.  693 

were  it  not  that  the  course  of  the  blood  passing  through  the  two  orifices  is  in  opposite 
directions,  and  the  auscultation  oi  the  auriculo-ventricular  orifice  is  consequently 
satisfactorily  performed  towards  the  apex  of  the  heart. 

Considerable  variation  from  the  position  of  the  heart  indicated  above  may  be  found.  Thus, 
the  apex  may  be  situated  behind  the  fifth  costal  cartilage,  or  more  rarely  the  sixth,  and  the  pul- 
monary aortic  orifice  may  occur  as  high  up  as  the  second  intercostal  space,  or  as  low  as  the  level 
of  the  fourth  costal  cartilage. 

The  heart  naturally  has  its  position  altered  somewhat  during  its  contraction  and  during  the 
respiratory  acts,  and  the  position  of  the  body  will  also  have  some  effect  in  modifying  its  location. 
Resting,  as  it  does,  upon  the  diaphragm,  the  heart  will  alter  its  position  somewhat  with  altera- 
tions of  that  muscle  ;  and  since  in  the  child  the  diaphragm  is  somewhat  higher  and  in  the  aged 
somewhat  lower  than  in  the  middle  period  of  life,  corresponding  changes  according  to  age  will 
be  found  in  the  position  of  the  heart.  It  may  be  noted,  furthermore,  that  the  position  of  the 
heart  as  determined  in  the  cadaver  will,  as  a  rule,  be  slightly  higher  than  in  the  living  body, 
owing  to  post-mortem  tissue  changes  which  allow  the  diaphragm  to  assume  a  more  vaulted  form 
than  is  usual  in  life. 

Relations. — As  regards  its  relations  the  heart  is  completely  enclosed  within  the 
pericardium,  with  which  alone  surrounding  organs  come  into  contact.  In  what  fol- 
lows it  is  really  the  relations  of  the  pericardium  that  will  be  described,  although  of 
necessity  these  relations  are  indirectly  those  of  the  heart  and  will  be  spoken  of  as 
such. 

Anteriorly  the  greater  part  of  the  heart  is  covered  by  the  anterior  borders  of 
the  lungs  and  pleurae,  which  separate  it  from  contact  with  the  anterior  thoracic  wall. 
As  a  rule,  the  anterior  borders  of  the  pleurae  are  in  contact  from  the  level  of  the 
second  costal  cartilage  to  that  of  the  fourth,  but  below  the  latter  level  they  separate, 
the  border  of  the  left  pleura  diverging  from  the  median  line  more  rapidly  than  that 
of  the  right.  In  consequence,  throughout  an  irregularly  triangular  area  (Fig.  1580), 
whose  vertical  diameter  extends  from  the  level  of  the  fourth  to  that  of  the  sixth 
costal  cartilages,  the  heart  is  uncovered  by  the  pleurae  and  lies  directly  behind  the 
thoracic  wall.  This  area  forms  what  is  termed  by  clinicians  the  area  of  absolute  dul- 
ness.  Laterally  the  heart  is  in  relation  with  the  lungs,  the  phrenic  nerves  passing 
downward  on  either  side  between  the  pericardium  and  the  pleura.  Posteriorly  the 
relations  are  again  with  the  lungs  and  with  the  oesophagus  and  the  thoracic  aorta. 
Inferiorly  the  heart  rests  directly  upon  the  diaphragm,  beneath  which  is  the 
stomach. 

Size  and  Weight. — There  is  considerable  individual  variation  in  the  size  of 
the  heart,  and  marked  discrepancies  exist  in  the  observations  that  have  been  re- 
corded. It  may  be  said  that  in  the  adult  the  heart,  on  an  average,  will  possess  a 
length  of  from  12-15  cm.  (4-^-6  in.),  a  greatest  breadth  of  from  9-1 1  cm. 
(3^-4^  in.)  and  a  thickness  of  from  5-8  cm.   (2-3^  in.). 

Its  weight  has  been  given  at  from  266-346  gm.  (9^-12^  oz. )  for  males  and 
from  230-340  gm.  (8^-12  oz. )  for  females,  the  average  of  a  series  of  observations  by 
different  authors  giving  312  gm.  (  1 1  oz.  )  for  the  male  and  274  gm.  (9%  oz.  )  for  the 
female.  The  proportion  of  heart  to  the  weight  of  the  entire  body,  according  to  an 
average  drawn  from  several  observers,  is  1  :  169  in  the  male  and  1  :  162  in  the  female. 
It  must  be  remembered,  however,  that  the  weight  of  the  heart  increases  with  age  up 
to  about  the  seventieth  year,  probably  a  slight  diminution  taking  place  after  that 
period. 

THE  CHAMBERS  OF  THE  HEART. 

It  has  already  been  noted  .that  the  heart  is  composed  of  four  chambers,  a  right 
and  left  auricle  and  a  right  and  left  ventricle.  As  the  heart  lies  in  position,  little  of 
the  auricles,  with  the  exception  of  the  auricular  appendices,  can  be  seen,  since  they 
have  in  front  of  them  the  roots  of  the  aortae.  In  the  ventricular  portion  the  greater 
part  of  the  anterior  surface  is  formed  by  the  right  ventricle,  a  small  portion  only 
of  the  left  ventricle  showing  to  the  left  and  at  the  apex,  the  whole  of  which  is  formed 
by  the  left  ventricle.  The  four  chambers  will  now  be  considered  in  succession,  begin- 
ning with  the  auricles. 

The  Right  Auricle. — The  right  auricle  ("atrium  dextrum')  is  a  relatively  thin- 
walled  chamber  having  in  cross-section  a  roughly  triangular  form,  the  various  sur- 


694 


HUMAN   ANATOMY. 


faces,  however,  passing  into  one  another  almost  insensibly  without  forming  distinct 
angles.  Viewed  externally,  the  roof  of  the  chamber  is  directed  upward,  backward 
and  somewhat  to  the  right,  and  near  its  junction  with  what  may  be  termed  the  poste- 
rior wall  receives  the  superior  vena  cava.  The  posterior  wall,  also  smooth  and 
rounded,  receives,  near  its  junction  with  the  median  wall,  the  inferior  vena  cava  and 
below  and  to  the  left  of  this,  in  the  posterior  auriculo-ventricular  groove,  is  the  ter- 
minal portion  of  a  vein  which  winds  around  the  heart  from  the  left  and  is  termed  the 
coronary  sinus.  The  antero-lateral  wall  is  prolonged  into  a  somewhat  triangular 
diverticulum  with  crenulated  edges,  which  winds  anteriorly  around  the  proximaf por- 
tion of  the  systemic  aorta  and  is  known  as  the  right  auricular  appendix  (auricula 
dextra).  The  median  wall  is  not  visible  on  surface  view,  and  is  formed  by  a  rather 
thin  muscular  partition,  the  auricular  septum  (septum  atriorum),  which  is  common  to 
both  auricles  ;  and  the  floor,  also  invisible  from  the  exterior,  corresponds  to  the  base 
of  the  right  ventricle,  and  is  perforated  by  an  oval  aperture,  the  right  auriculo-ven- 
tricular orifice,  which  places  the  cavity  of  the  auricle  in  communication  with  that  of 
the  right  ventricle. 

Fig.  657. 


Systemic  aorta 
Pulmonary  aorta  or  artery 


Right  pulmo- 
nary artery 


Right  auricular  appendage 


Fossa  ovalis, 
surrounded 
by  annulus 
Inferior 
vena  cavp 


Orifice  of  coronary  sinus,  guarded  by  Thebesian  valv 
Depression  receiving  Thebesian  veins 


1  of  part  of  heart  1 


When  the  interior  of  the  right  auricle  is  examined  (Figs.  657,  661),  the 
surface  is  found  to  be  for  the  most  part  smooth,  being  lined  throughout  by  a  delicate 
shining  membrane  covered  by  flattened  cells  and  termed  the  endocardium.  The 
general  smoothness  of  the  surface  is,  however,  interrupted  here  and  there  by  minute 
depressions  (foramina  venarum  minimarunO  into  some  of  which  open  the  orifices  of 
Thebesian  veins  that  traverse  the  walls  of  the  heart.  The  cavity  of  the  auricular 
appendix  is  crossed  by  a  net-work  of  anastomosing  fibro-muscular  trabecular,  the 
muscuh  pectinati,  which  are  everywhere  lined  upon  their  free  surfaces  by  endocardium 
and  give  to  the  appendix  a  somewhat  spongy  texture.  In  the  roof  of  the  auricle  is 
seen  the  circular  orifice  of  the  superior  vena  cava,  unguarded  by  valves  and  having  a 
diameter  of  from  18-22  mm.,  and  on  the  posterior  wall  is  the  somewhat  oblique 
opem?2g  of  the  inferior  ve?ia  cava,  somewhat  larger  than  that  of  the  superior  one, 
measuring  from  27-36  mm.  in  diameter.  The  lower  and  lateral  margins  of  this 
orifice  are  guarded  by  a  crescentic  fold,  the  Eustachian  valve  (valvula  venae  cavae 
inferioris),  which  tends  to  direct  the  blood  entering  by  the  vein  upward  and  medially, 
and  is  the  remains  of  a  structure  of  considerable  importance  during  fcetal  life  (page 


THE    CHAMBERS    OF   THE    HEART. 


695 


Pulmonary  aorta 


Right  auricular 
.ppendage 


708).  Between  the  superior  and  inferior  venae  cavae  there  may  sometimes  be  seen 
a  more  or  less  marked  prominence  of  the  posterior  wall,  the  tubercle  of  Lower 
(tuberculum  intervenosum),  the  remains  of  a  structure  "also  of  importance  in  the  foetal 
circulation.  Below  and  somewhat  median  to  the  opening  of  the  inferior  vena  cava 
is  the  circular  orifice  of  the  coronary  sinus,  measuring  about  12  mm.  in  diameter, 
and  guarded,  like  the  inferior  caval  orifice,  by  a  crescentic  valve  which  surrounds  its 
lateral  margin  and  is  termed  the  Thebesian  valve  (valvula  sinus  coronarii). 

The  median  wall,  in  addition  to  a  number  of  Thebesian  orifices,  presents  at  about 
its  centre  an  oval  depression,  the  fossa  ovalis,  whose  superior  and  anterior  borders 
are  surrounded  by  a  thickening  or  slight  fold  termed  the  annulus  ovalis  (limbus  fossae 
ovalis). 

The  fossa  ovalis  indicates  the  position  of  what  was  in  fcetal  life  the  foramen  ovale,  through 
which  the  blood  entering  the  right  auricle  from  the  inferior  vena  cava  passed  directly  into  the 
left  auricle  and  so  joined  at  once  the  systemic  circulation  (page  929).  This  foramen  traversed 
the  auricular  septum  obliquely,  the  septum  really  consisting  of  two  folds,  one  of  which  projected 
backward  from  the  anterior  wall  of  the  auricular  portion  of  the  heart,  and  the  other  forward  from 
the  posterior  wall,  the  plane  of  the  latter  fold  lying  slightly  to  the  left  of  that  of  the  former  one. 
After  birth  these  two  folds  increase  in  size  so  that  their  free  margins  overlap  and  event- 
ually fuse,  closing  the  foramen,  and 

the  original  free  edge  of  the  ante-  Fig.  658. 

rior  fold  becomes  the  annulus  of 
Vieussens,  while  the  floor  of  the 
fossa  ovalis  is  formed  by  the  pos- 
terior fold. 

It  occasionally  happens  that 
the  foramen  ovale  fails  to  close 
after  birth,  remaining  sufficiently 
open  to  permit  of  serious  disturb- 
ances of  the  circulation  which  are 
usually,  although  not  always,  early 
fatal.  Very  frequently,  however, 
the  fusion  of  the  overlapping  sur- 
faces of  the  two  folds  is  not  quite 
complete,  and  a  small,  oblique,  slit- 
like opening  persists  between  the 
two  auricles.  In  such  cases  during 
the  contraction  of  the  auricles  the 
pressure  of  the  blood  on  the  over- 
lapping walls  of  the  slit  brings 
them  into  close  apposition  and  effectually  closes  the  slit,  so  that  no  disturbances  of  the  circula- 
tion result  from  its  presence.  This  slit-like  opening  has  been  found  to  be  present  in  somewhat 
over  30  per  cent,  of  the  adult  hearts  examined. 

The  Left  Auricle. — The  left  auricle  (atrium  sinistrum)  has  the  same  general 
external  form  as  the  right  one,  and,  as  in  the  latter,  its  antero-lateral  wall  is  prolonged 
into  an  auricular  appendix  which  curves  forward  around  the  left  side  of  the  proximal 
portion  of  the  pulmonary  aorta.  Upon  its  posterior  surface  the  auricle  receives  the  four 
pulmonary  veins  arranged  in  pairs,  one  of  which  is  situated  nearer  the  medial  and  the 
other  towards  the  lateral  edge  of  the  surface,  and  passing  obliquely  over  this  surface 
towards  the  coronary  sinus  is  a  small  vein,  known  as  the  oblique  vein  of  the  left 
auricle  (vena  obliqua  atrii  sinistri  [Marshall!]),  which  represents  the  proximal  end  of 
the  left  vena  cava  superior  present  during  early  embryonic  life  (page  927). 

Viewed  from  the  interior,  the  walls  of  the  left  auricle,  like  those  of  the  right  one, 
are  everywhere  lined  by  a  smooth,  shining  endocardium  ;  in  the  appendix  the  spongy 
structure  due  to  the  existence  of  anastomosing  musculi  pccti?iati  also  occurs,  and 
occasional  depressions  of  the  surface  mark  the  openings  of  vena  Thebcsii,  which  are, 
however,  much  less  abundant  than  in  the  right  auricle.  The  openings  of  the  pul- 
monary veins  on  the  posterior  wall  are  circular,  and  each  measures  from  14-15  mm. 
in  diameter  ;  they  are  unguarded  by  valves,  although  a  slight  horizontal  fold  sepa- 
rates the  portion  of  the  auricular  cavity  into  which  the  left  veins  open  from  the 
entrance  into  the  auricular  appendix. 

Upon  the  median  wall,  over  the  area  occupied  by  the  fossa  ovalis  of  the  right 
auricle,  a  slight  depression  is  frequently  to  be  observed,  and  immediately  anterior  to 
it  there  is  usually  a  small  crescentic  fold,  the  semilunar  fold,  whose  concavity  is 


Heart  of  fcetus  just  before  birth  ;  wall  of  right  auricle 
has  been  cut  away,  showing  foramen  ovale. 


6a6 


HUMAN    ANATOMY. 


directed  forward,  and  which  represents  the  free  edge  of  the  posterior  segment  or  fold 
of  the  auricular  septum  (page  708J.  In  the  floor  is  situated  the  large  circular 
auriculo-ventricular  orifice  by  which  the  cavity  of  the  auricle  communicates  with  that 
of  the  left  ventricle. 

The  Ventricles. — The  two  ventricles  present  many  features  in  common  and 
may  be  described  together,  such  differences  as  exist  between  them  being  pointed  out 
as  the  description  proceeds.  Each  has  a  form  which  may  be  likened  to  a  three-sided 
pyramid  whose  base  is  directed  upward  and  the  apex  downward.  The  edges  of  the 
left  ventricle  are,  however,  somewhat  more  rounded  than  those  of  the  right,  so  that 
its  form  approaches  more  nearly  that  of  a  cone  ;  and,  furthermore,  it  is  somewhat 


Fig.  659. 


Left  pulmonary  artery 


Superior  left  pulmonary 
Left 


append 


Part  of  posterior 

leaflet  of  mitral 

valve 


Left  ventricle 


Interior  of  left  auricle  and  ventricle,  seen  from  behind  ;  posterior  wall  of  heart 
has  been  partially  removed  by  frontal  section. 

longer  than  the  right,  its  apex  alone  forming  the  apex  of  the  heart.  The  surfaces 
presented  by  each  ventricle  may  be  termed  antero-lateral,  posterior,  and  median,  but 
in  using  these  terms  the  heart  is  to  be  regarded  as  placed  so  that  its  long  axis  is  ver- 
tical ;  in  situ  the  antero-lateral  surfaces  look  largely  upward  and  the  posterior  sur- 
faces downward.  The  median  wall  is  a  partition,  the  interventricular  septum  (septum 
ventrkulorum),  common  to  the  two  ventricles,  and  completely  separates  their  cavities. 
Throughout  the  greater  part  of  its  extent  this  septum  is  muscular,  but  towards  its 
upper  border  it  becomes  fibrous  {pars  membrancea)  and  is  continuous  with  the 
septum  of  the  auricles  ;  the  position  of  its  edges  are  indicated  upon  the  external  sur- 
face of  the  heart  by  the  anterior  and  posterior  interventricular  grooves.      The  bases  of 


THE  CHAMBERS  OF  THE  HEART. 


697 


the  ventricles  are  directed  upward,  backward,  and  to  the  right,  and  each  is  perforated 
by  two  orifices.  One  of  these  in  each  ventricle  is  the  auriculo-ventricular  orifice, 
while  the  other,  in  the  case  of  the  right  ventricle,  is  the  opening  of  the  pulmonary 
aorta,  and  is  placed  in  front  and  a  little  to  the  left  of  the  auriculo-ventricular  orifice 
upon  the  summit  of  a  slight  conical  elevation  of  the  base  of  the  ventricle,  termed 
the  conus  arteriosus  or  infundibulum.  The  second  orifice  of  the  left  ventricle  is  the 
opening  of  the  systemic  aorta,  and  is  situated  in  front  and  a  little  to  the  right  of  the 
corresponding  auriculo-ventricular  orifice,  immediately  adjoining  it. 

Compared  with  those  of  the  auricles,  the  walls  of  both  ventricles  are  very  thick, 
that  of  the  left  especially  so,  being  from  two  and  a  half  to  three  times  as  thick  as  the 
right  one.      Unlike  the  auricles  in  another  way,  the  inner  surfaces  of  the  ventricles. 


Superior  vena 


—  Pulmonary  aorta 

(pulmonary  artery) 


Left  coronary  artery 


Leaflet  of  aortic  valve 


Inferior  vena  cava 
Eustachian  valve 

Pectinate  muscles 

Thebesian  valve 
guarding  opening; 
of  coronary  sinus 
Posterior  leaflet  of 

tricuspid  valve 


branous  part 
of  interventricu- 
lar septum 


Septal  papillary  muscles' 
Posterior  papillary 


Posterior  portion  of  heart,  hardened  in  situ  and  sectioned 
parallel  to  posterior  surface ;  viewed  from  before. 


instead  of  being  even,  are  very  irregular,  being  everywhere  covered  by  muscular 
ridges  or  columns,  over  and  around  which  the  endocardium  is  folded.  These  mus- 
cular elevations  are  usually  regarded  as  consisting  of  three  varieties  :  ( 1 )  ridges 
which  are  attached  throughout  their  entire  length  to  the  wall  of  the  ventricle,  upon 
which  they  stand  out  like  bas-reliefs  ;  (2)  columns  which  are  attached  at  either 
extremity  to  the  wall  of  the  ventricle,  but  are  free  from  it  throughout  the  intervening- 
portion  of  their  length  ;  and  (3)  columns  which  are  attached  only  by  one  extremity 
to  the  ventricular  wall  and  by  their  other  extremity  give  attachment  to  slender  ten- 
dons, chorda  tendinece,  which  pass  to  the  edges  of  the  valves  guarding  the  auriculo- 
ventricular  orifices.  To  the  columns  belonging  to  the  first  and  second  of  these 
groups  the  term  columns  carnece  is  applied,  while  those  of  the  third  group  are  known 


698  HUMAN   ANATOMY. 

as  the  musculi papillares.  Quite  frequently  in  the  right  ventricle  and  more  rarely  in 
the  left,  a  muscular  band  occurs,  which  passes  across  the  cavity  from  one  wall  to  the 
other  near  the  apex  ;  such  a  structure  constitutes  what  has  been  termed  a  moderator 
band.  Here  and  there  between  the  columnar  carnea;  of  both  ventricles  minute  orifices 
of  the  Thebesian  vessels  occur. 

Around  the  orifices  situated  at  the  bases  of  the  ventricles  the  muscular  sub- 
stance of  the  heart's  walls  passes  over  into  dense  fibrous  tissue,  of  which  the  portion 

Fig.  661. 


Pulmonary  aorta  (pulmonary  artery) 


Corpus  Arantii  on  posterior  leaflet 
Anterior  leaflet  of 
aortic  valve,  cut- 


Interventricular 


Muiicrat'  >r  baud 


Superior  vena  cava 


Svstemic  aorta 


Right  coronary 


Right  auricular 
appendage 


Pectinate  muscles 


Anterior  leaflet  of 
tricuspid  valve 

Margin  of  tricuspid 
valve 


Chordse  tendineae 


Anterior  wall  of  heart  hardened  in  situ  and  sectioned  parallel  to  posterior  surface, 
viewed  from  behind  ;  only  very  small  part  of  left  ventricle  is  seen  ;  probe  passes  from 
pulmonary  aorta  (artery)  into  right  ventricle. 


surrounding  the  auriculo-ventricular  orifices  serves  to  connect  the  auricles  and  ven- 
tricles. If  the  auricles  and  the  proximal  portions  of  the  aorta;  be  removed,  the 
fibrous  tissue  will  be  seen  to  form  four  rings  (annuli  fibrosi),  one  corresponding  to 
each  of  the  basal  orifices  of  the  ventricles;  and,  furthermore,  three  of  the  rings — 
those  surrounding  the  two  auriculo-ventricular  orifices  and  that  of  the  systemic  aorta 
— will  be  seen  to  be  directly  in  contact,  while  the  fourth — that  surrounding  the  pul- 
monary aortic  orifice — is  separate  from  the  others,  although  connected  with  the  right 
auriculo-ventricular  ring  by  a  narrow  fibrous  band  which  descends  in  the  posterior 


THE    CHAMBERS    OF    THE    HEART.  699 

wall  of  the  conus  arteriosus.  The  ring  surrounding  the  left  auriculo-ventricular 
orifice  is  somewhat  thicker  than  that  of  the  right,  and  is  fused  with  the  systemic  aortic 
ring  throughout  about  the  medial  third  of  its  circumference,  whereas  the  correspond- 
ing fusion  of  the  right  ring  is  of  much  less  extent.  In  the  angle  formed  by  the 
junction  of  the  right  auriculo-ventricular  ring  at  the  side  with  the  systemic  aortic 
ring  in  front  a  special  thickening  of  the  fibrous  tissue  occurs,  so  that  it  becomes  of 
almost  cartilaginous  consistency,  and  a  similar,  although  smaller,  thickening  also 
occurs  in  the  angle  formed  by  the  junction  of  the  anterior  walls  of  the  left  auriculo- 
ventricular  and  systemic  aortic  rings.  These  thickenings  form  what  are  termed  the 
right  and  left  auriculo-ventricular  nodes  (trigona  fibrosa),  and  they  are  of  interest  as 
being  occasionally  the  seat  of  a  calcareous  deposit  or  of  a  fatty  infiltration,  a  condi- 
tion which  may  be  shared  by  fibre-like  prolongations  of  the  nodes  (_/?/«  coronaria) 
which  extend  into  adjacent  portions  of  the  auriculo-ventricular  rings. 

The  Auriculo-Ventricular  Valves. — Attached  by  its  base  to  each  auriculo- 
ventricular  fibrous  ring,  and  projecting  downward  into  the  cavity  of  the  correspond- 
ing ventricle,  is  a  valve  having  the  general  form  of  a  membranous  cone,  whose  walls 
are  of  thin  but  strong  fibrous  tissue  covered  on  both  sides  by  the  endocardium.  Each 
cone,  however,  is  divided  by  deep  incisions  into  triangular  segments,  of  which  there 
are  three  in  the  valve  of  the  right  ventricle,  whence  it  is  usually  termed  the  tricuspid 
valve,  while  two  incisions  divide  the  left  valve  into  two  segments  and  procure  for  it 
the  name  of  the  bicuspid  or  mitral  valve,  the  latter  term  being  suggested  by  its 
resemblance  to  a  bishop's  mitre.  Of  the  three  segments  of  the  tricuspid  valve, 
one  (cuspis  anterior),  larger  than  the  others  and  also  known  as  the  infundibular 
cusp  is  attached  to  the  anterior  border  of  the  auriculo-ventricular  orifice  ;  a  second 
one  (cuspis  posterior)  is  attached  to  the  posterior  border  ;  while  the  third  or  septal 
(cuspis  medialis)  occupies  the  interval  between  the  medial  edges  of  the  other  two, 
and  is  attached  to  that  portion  of  the  auriculo-ventricular  fibrous  ring  which  is 
united  to  the  right  auriculo-ventricular  node  and  to  the  upper  part  of  the  ventricular 
septum.  In  the  mitral  valve  one  segment  (cuspis  posterior)  is  attached  to  the 
posterior  border  of  the  auriculo-ventricular  fibrous  ring,  while  the  other  (cuspis 
anterior)  or  aortic  cusp  is  situated  anteriorly,  and  depends  from  that  portion  of 
the  ring  which  is  united  to  the  ring  surrounding  the  systemic  aortic  orifice,  and 
consequently  appears  to  be  a  downward  prolongation  from  the  posterior  border  of 
that  orifice.  It  is  to  be  noted  that  the  depths  of  the  incisions  separating  the  seg- 
ments of  both  valves  vary  considerably,  and  additional  incisions  may  occur,  resulting 
in  the  formation  of  additional  segments.  Not  infrequently  a  small  accessory  segment 
occupies  the  apex  of  one  or  more  of  the  incisions. 

These  valves,  while  permitting  the  free  passage  of  blood  from  the  auricles  into  the 
ventricles,  prevent  its  passage  in  the  reverse  direction  during  the  contraction  of  the 
ventricles  ;  for  the  pressure  of  the  blood  within  the  ventricles  forces  the  segments  up- 
ward so  that  they  completely  occlude  the  auriculo-ventricular  orifices,  the  chorda; 
tendineae  which  are  attached  to  them,  and  which  are  rendered  taut  by  the  contraction 
of  the  papillary  muscles,  preventing  them  from  being  forced  back  into  the  auricles. 
The  musculi  papillares  of  each  ventricle  are  arranged  in  two  groups,  one  consisting 
of  small  papilla?,  situated  near  the  upper  portion  of  the  ventricle  behind  the  segments 
of  the  valves,  and  the  other,  composed  of  larger  conical  muscles,  situated  nearer  the 
apex.  The  chordae  tendineae  which  arise  from  the  upper  group  are  short,  and  are 
attached  to  the  ventricular  surface  of  the  valve  near  its  base  ;  those  which  arise  from 
the  lower  group  are  much  larger,  and  are  attached  to  the  edges  of  the  valve  and  to 
its  ventricular  surface  near  its  free  edge.  The  papillary  muscles  belonging  to  this 
lower  group  tend  to  be  arranged  in  sets  corresponding  in  position  with  the  incisions 
which  separate  the  segments  of  the  valves,  and  there  are,  accordingly,  three  sets  in 
the  right  ventricle  and  two  in  the  left  ;  but  this  arrangement  is  not  quite  definite,  and 
there  is  also  considerable  variation  in  the  number  of  papillary  muscles  in  each  set, 
only  one  being  present  in  some  cases  and  several  in  others.  However  that  may  be,  / 
the  chorda?  tendineae  arising  from  the  apices  of  the  muscles  of  each  set  diverge  as  ' 
they  pass  upward  and  are  attached  to  both  the  adjacent  segments  of  the  valve.  When 
distinct  accessory  segments  occur,  they  also  receive  the  insertion  of  some  of  the 
chordae  tendineae. 


7oo 


HUMAN    ANATOMY. 


The  Semilunar  Valves. — Although  really  belonging  to  the  pulmonary  and 
systemic  aortae,  it  is  convenient  to  consider  these  valves  along  with  the  heart,  since 
they  prevent  the  regurgitation  of  the  blood  contained  in  the  aortae  into  the  ventricles 
at  the  completion  of  their  contraction. 

The  segments  guarding  these  valves  are  three  in  number  in  each  aorta  and  are 
attached  to  the  fibrous  ring  of  the  aortic  orifices.  Each  segment  is  a  crescentic 
pouch-like  structure,  whose  cavity  is  directed  away  from  the  heart,  so  that  any  ten- 
dency for  the  blood  to  return  from  the  aortae  into  the  ventricles  will  result  in  the  fill- 
ing of  the  pouches  so  that  the  three  are  brought  into  apposition  and  effectually  close 
the  orifice.  Their  efficiency  is  increased  by  ( I )  the  occurrence  at  the  middle  of  the 
free  edge  of  each  segment  of  a  small  fibro-cartilaginous  nodule,  the  nodule  of  Aran- 
tiics,  which  fills  the  small  gap  which  might  otherwise  be  left  at  the  point  of  meeting  of 
the  free  edges  of  all  three  segments  ;  and  by  (2)  the  aorta  being  pouched  out  behind 
each  segment  to  form  a  small  pocket,  a  sinus  of  Valsalva,  greater  opportunity  being 
thus  allowed  for  the  blood  to  enter  the  cavities  of  the  valves  and  so  force  their  free 
edges  together. 

The  segments  of  the  semilunar  valves  of  the  systemic  aorta  (valvulae  semilunares 
aortae)  are  somewhat  stronger  than  those  of  the  pulmonary  aorta  (valvulae  semilu- 

Fig.  662. 


Post,  leaflet  of  pul 


Right  posterior  leaflet  of 
aortic  valve 

riculo-ventricular  valve  1 


Anterior  cusp  of  right 


Medial  cusp 


Fibrous  ring  surrounding 
tricuspid  valve 


Valves  of  heart  viewed  from  above,  after  removal  of  auricles  and  greater  part  of  aortae. 


nares  a  pulmonalis),  and  are  arranged,  if  considered  with  reference  to  the  planes  of 
the  body,  the  heart  being  in  situ,  so  that  one  is  situated  anteriorly  and  the  other 
two  right  and  left  posteriorly.  In  the  pulmonary  aorta  one  valve  segment  will  be 
posterior  and  the  others  right  and  left  anteriorly.  If,  however,  the  heart  be  held 
so  that  its  ventricular  septum  lies  in  the  sagittal  plane,  then  the  valve  segments  differ 
by  6o°  from  the  relative  position  given  above,  those  of  the  pulmonary  artery  being 
arranged  so  that  one  lies  anteriorly  and  the  other  two  right  and  left  posteriorly, 
while  in  the  systemic  aorta  one  is  posterior  and  the  other  two  right  and  left  anter- 
iorly, an  arrangement  to  be  expected  from  the  manner  of  development  of  the 
valves  (page  710). 

The  Architecture  of  the  Heart  Muscle. — The  musculature  of  the  walls 
of  the  auricles  is  relatively  very  thin,  and  it  is  difficult  to  distinguish  any  definite 
arrangement  of  its  fibres  in  layers.  Groups  of  fibers  can,  however,  be  distin- 
guished, and  of  these  certain  are  confined  to  each  auricle,  while  others  are  common 
to  the  two. 

Of  the  fasciculi  proper  to  each  auricle  two  principal  groups  can  be  recognized. 

I.  Annular  fasciculi,  which  surround  the  orifices  of  the  veins  entering  the 
auricles,  and  represent  the  continuation  of  the  circular  muscle  layer  of  the  veins  into 
the  auricular  walls. 


THE   CHAMBERS    OF   THE    HEART. 


701 


Fig.  663. 

Anterior  cusp  of  aortic  valve 


Portion  of  left  ventricle,  showing  position  (  +  ) 
turiculo-ventricular  muscle  bundle  in  membran- 
i  part  of  interventricular  septum.     [Rttzer.) 


2.  Ansiform  fasciculi,  which  take  their  origin  from  the  auriculo-ventricular 
fibrous  ring  anteriorly  and  extend  over  the  auricle  to  insert  into  the  fibrous  ring 
posteriorly.  These  bundles  are  situated  as  a  rule  more  deeply  than  the  annular 
fasciculi  and  produce  the  pectinate  mus- 
cles of  the  auricular  appendage,  as  well 
as  certain  columnar  elevations,  covered 
by  endocardium,  which  occur  upon  the 
inner  surfaces  of  the  walls  of  the  auricles. 
The  fasciculi  common  to  both  auri- 
cles are  developed  only  in  the  neighbor- 
hood of  the  auriculo-ventricular  groove, 
and  constitute  thin  superficial  bands, 
which  run  parallel  to  the  groove.  The 
anterior  fasciculus  is  broader  and  more 
highly  developed  than  the  posterior  one. 
The  auriculo-ventricular  fibrous  ring 
forms  an  almost  complete  separation  be- 
tween the  musculature  of  the  auricles  and 
that  of  the  ventricles,  the  only  direct  con- 
nection between  the  two  being  formed 
by  a  slender  auriculo-ventricular  fasci- 
culus. This  takes  its  origin  in  the  pos- 
terior wall  of  the  right  auricle  close  to 
the  auricular  septum  (His,  Jr.)  and  passes 
downward  towards  the  upper  border  of 
the  muscular  portion  of  the  ventricular 
septum  (Fig.  663).  Here  it  bends  forward  and  runs  across  the  septum  in  the  line 
of  junction  of  its  membranous  and  muscular  portions,  and  is  lost  anteriorly  in  the 
musculature  of  the  ventricles.  The  existence  of  this  auriculo-ventricular  fasciculus 
is  of  considerable  importance  in  connection  with  transmission  of  the  contraction  wave 
from  the  auricles  to  the  ventricles,  the  application  of  a  clamp  to  the  bundle  having 
been  shown  to  produce  heart-block  (Erlanger). 

It  can  readily  be  perceived  that  the  muscle-fibres  of  which  the  walls  of  the 
ventricles  are  composed  are  arranged  in  more  or  less  definite  layers,  and  that  the 
direction  of  the  fibres  in  the  deeper  layers  is  different  from  that  of  the  more  super- 
ficial ones.  The  descriptions  of  the  various  layers  and  of  their  relations  to  one 
another  vary  greatly  in  different  authors;  in  that  given  here  the  results  obtained  by 

MacCallum,    by  the    application 
Fig,  664.  0f    more  suitable  methods  than 

were  available  to  the  earlier  ob- 
servers, will  be  followed. 

The  fibres  of  the  ventricles 
can  start  only  from  the  fibrous 
rings  surrounding  the  ventricu- 
lar orifices  or  else  from  the  sum- 
mits of  the  musculi  papillares,  to 
which  a  certain  amount  of  fixa- 
tion is  afforded  by  the  chorda; 
tendinea;  and  their  attachment 
to  the  auriculo-ventricular  valves. 
It  will  be  convenient  to  regard 
the  fibrous  rings  as  the  principal 
points  of  origin,  and  the  most 
superficial  layer  of  the  muscula- 
ture may  be  said  to  arise  from 
them  and  from  the  tendinous 
band  which  descends  upon  the  posterior  surface  of  the  conus  arteriosus  towards  the 
right  auriculo-ventricular  ring.  Those  fibres  which  take  their  origin  from  this  ten- 
dinous band  and  the  right  ring  wind  in  a  left-handed  spiral  over  the  surface  of  the 


1  of  course  of  superficial  muscle  layers  originating 
nd  left  auriculo-ventricular  rings  and  in  posterior 
half  of  tendon  of  conus  arteriosus.     {MacCallum.) 


HUMAN    ANATOMY. 


Left 

auriculo- 

ventricular 

orifice- 


ventricles,   and  when   they  reach  the  apex,   they  bend   upon  themselves  and  pass 
deeply  and  upward  to  terminate  in  the  papillary  muscles  of  the  left  ventricle.     Those 
fibres  which  arise  from  the  left  auriculo-ventricular  fibrous  ring  cross  the  posterior  in- 
terventricular groove  and,  pass- 
ive 6^5  ing  beneath  the  fibres  from  the 
Tendon  of             right  ring,  encircle  the  right  ven- 
conus  arteriosus     tricle  and  finally  terminate  in  the 
venn'icuiaronfice   papillary    muscles    of   that    ven- 
tricle. 

On    the    removal    of    these 

superficial  fibres  a  deeper  set  is 

papii-      seen,   which  seem   to  form   two 

luscles  ,  ,  , 

ior  muscular  cones,  each  surround- 

•ry  ing   one   of   the    ventricles.      In 

the  adult  heart  it  is  difficult  to 
perceive  the  true  relations  of  the 
two  cones,  but  in  the  hearts  of 
young  individuals  up  to  two  or 
three  years  of  age  it  has  been 

anterior    {ound     that     both    thg    CQnes    are 

formed  by  the  curving  of  a  con- 
tinuous sheet  of  fibres  in  an  S-shaped  manner.  This  deep  sheet  of  fibres  takes  its 
origin  principally  from  the  right  auriculo-ventricular  fibrous  ring  and  from  the  ten- 
dinous band  of  the  conus  arteriosus,  and  encircles  the  right  ventricle,  lying  beneath 
the  superficial  layer.  When  it  reaches  the  posterior  border  of  the  ventricular  sep- 
tum, it  passes  forward  in  that  structure,  and  then  encircles  the  left  ventricle,  termi- 
nating finally  in  the  papillary  muscles  of  that  ventricle.  The  deep  fibres  which  arise 
from  the  left  fibrous  ring  are  entirely  confined  to  the  left  ventricle,  forming  a  circular 
band  surrounding  its  basal  portion. 

Structure. — The  heart  muscle,  the  myocardium,  is  both  covered  and  lined 
with  serous  membrane,  the  epicardium,  as  the  visceral  layer  of  the  pericardium  is 
often  called,  investing  it  externally  and  the  endocardium,  continuous  with  the  intima 
of  the  large  blood-vessels,  clothing  all  parts  of  its  elaborately  modelled  inner  surface. 

The  epicardium  corresponds  in  its  general  structure  with  other  parts  of  the 
pericardium,  consisting,  as  do  other  serous  membranes,  of  a  single  layer  of  endothelial 
cells  that  covers  its  free  surface  and  rests  upon  a  stratum  of  fibro-elastic  connective 
tissue.  The  elastic  fibrillar  are  very  fine  and  numerous  and,  immediately  beneath  the 
endothelium,  form  a  dense  net-work.  When  not  separated  from  the  muscle  by 
subserous  fat,  as  it  con- 
spicuously is  in  the  in-  Fig.  666. 

terventricular  and  auric-        ,h^"f°'  ~— — ^^  <n — r— -^__ rr^jg; 

ulo-ventricular  grooves, 
the  epicardium  is  inti- 
mately attached  to  the 
subjacent  muscular  tis- 
sue.    The  numerous 

branches   of  the   coron-         Deepest— -  ~~'~'".       ..-    -~  ...  .   •-*.   "~-T'_ 

ary  vessels,   as   well   as  -->r--    -     -TV     -•-.■,  T~':  .  -.  >5Vv 

the    nerve    trunks  and  "'\- ■-i  -;    V  '  ■' "  •  - W> 

the  microscopic  ganglia  '"•"■>.?;.-     y  :        -  •  ■. .     .  .  .  ;T\ 

connected  with  the  car-  '"'""'         J  '    S" 

diac    plexuses,    lie    be-  Heart  muscle  .■'•':'  *\   >._■>■■ 

neath  the  epicardium  or  -y;~-,.. -;■      •"- '-.  m-  \    \)\) 

within  its  deepest  layer.  Blood-vessel  jSSg   \^»v  P-" 

Theendocardium  Section  of  endocardium.^    32s 

follows  all  the  irregular- 
ities of  the  interior  of  the  heart,  lining  every  recess  and  covering  the  free  surfaces  of 
the  valves,  tendinous  cords  and  papillary  muscles.      It  consists  of  the  endothelium 
and  the  underlying  connective  tissue.      The  latter  is  differentiated  by  the  distribution 


Subendo-  - 
thelial 

stratum 
Layer  rich  - 
in  elastica 


VESSELS    OF    THE    HEART. 


7°3 


Muscular  tissue 


of  the  elastica  into  two  strata,  a  thin  subendothelial  layer  practically  free  from  elastic 
fibres  and  a  broad  layer  in  which  the  elastica  predominates.  The  deepest  stratum 
of  the  endocardium  is  continuous  with  the  endomysium  that  penetrates  between  the 
fibres  of  the  heart  muscle. 

The  valves  consist  of  duplicatures  of  the  endocardium,  in  their  thicker  parts 
strengthened  by  an  intermediate  middle  layer  of  fibro-elastic  tissue  prolonged  from 
the  fibrous  rings  of  attachment.      Towards  the  free  margins  of  the  valves  all  three 
layers  are  blended  and  reduced  to  a  thin  fibrous  stratum  covered  by  endothelium. 
In  the  auriculo-ventricular  leaflets,  the  fibro-elastic  tissue  of  the  chorda;  tendineae  is 
continuous  with  the  middle  layer,  while  meagre  peripheral  bundles  of  muscle  may  be 
present  beneath  the  endocardium.    Al- 
though   thinner    than    the    auriculo-  F'G-  667 
ventricular,  the  pulmonary  and  aortic  jL. , 
semilunar  valves  possess  essentially  the                                                        V         *. 
same  structure,  the  endocardial  layer, 
however,  being  thickened  to  produce 
the  noduli  Aurantii. 

In  addition  to  the  structural  de- 
tails of  the  fibres  composing  the  myo- 
cardium already  described  in  connec- 
tion with  the  general  histology  of 
muscle  (page  462),  it  may  be  noted 
that  in  the  immediate  vicinity  of  their 
nuclei  the  fibres  of  the  heart-muscle 
constantly  contain  accumulations  of 
undifferentiated  sarcoplasm  in  which 
lie  groups  of  highly  refracting  brown- 
ish granules  that,  under  moderate 
magnification,  appear  as  pigment  at 
the  poles  of  the  nuclei.  The  muscle- 
fibres,  branching  into  net-works  with 
long  narrow  meshes,  are  held  together 
by  delicate  lamellae  of  connective  tis- 
sue, the  endomysium,  which,  together 
with  the  more  robust  septa  that  as  the 
perimysium  invest  the  muscular  bun- 
dles, support  the  blood-vessels.  The 
relation  of  the  capillaries  to  the  muscle- 
substance  is  unusually  intimate,  the 
capillary  loops  often  modelling  the  sur- 
face of  the  fibres,  lying  in  deep  grooves 
almost  completely  enclosed  by  the  sur- 
rounding sarcous  tissue  (Meigs).  Al- 
though much  less  constant  and  typical 
than  in  the  ventricular  myocardium  of 
many  of  the  lower  animals,  as  the 
sheep,  goat,  and  ox,  the  imperfectly 
differentiated  fibres,  known  as  fibres 
of  Purkinje,  are  represented  in  the 
human  heart-muscle  by  subendocardial  fibres.  There  is  reason  to  believe  that  these 
fibres  are  related  to  the  co-ordinating  auriculo-ventricular  bundle  of  His  (page  701.) 

The  Blood-Vessels  and  Lymphatics  of  the  Heart. — The  heart  receives 
its  blood-supply  through  the  two  coronary  arteries  which  arise  from  the  systemic 
aorta  immediately  above  its  origin,  the  return  flow  being  by  the  coronary  veins  which 
open  into  the  right  auricle  by  the  coronary  sinus.  Both  these  sets  of  vessels  will  be 
described  later  (page  728),  but  it  may  be  pointed  out  here  that  the  branches  of  the 
coronary  artery  upon  the  surface  of  the  heart  are,  as  a  rule,  all  end-arteries, — that  is, 
arteries  which  form  no  direct  anastomoses  with  their  neighbors.  Practically  no 
blood  can  be  carried  directly,  therefore,  by  the  left  coronary  artery  into  the  territory 


Longitudinal  section  of  leaflet  of 
tricuspid  valve.     X  20. 


704  HUMAN    ANATOMY. 

supplied  by  the  right  one,  or  vice  versa,  and  sudden  occlusion  of  either  of  the  arteries 
will  produce  serious  disturbances  or,  in  some  cases,  complete  arrest  of  the  contrac- 
tions of  the  heart.  Since,  however,  the  capillaries  of  the  heart's  substance,  into 
which  each  artery  is  continued,  form  a  continuous  net-work,  a  passage-way  for  the 
blood  of  one  artery  into  the  territory  normally  supplied  by  the  other  may  be  formed 
by  their  enlargement,  opportunity  for  which  may  be  afforded  in  cases  in  which  the 
occlusion  of  an  artery  has  been  very  gradual  in  its  development. 

There  is,  however,  another  way  by  which  the  tissue  of  the  heart  may  receive  nutrition  in 
cases  of  gradual  occlusion  of  the  coronary  arteries,  namely,  through  the  Thebesian  orifices  in 
the  walls  of  the  auricles  and  ventricles.  These  openings  communicate  by  means  of  capillaries 
with  the  coronary  vessels,  and  it  has  been  shown  experimentally  that  the  heart  can  be  effectively 
nourished  by  blood  passing  from  the  chambers  of  the  heart  through  the  Thebesian  vessels  and 
back  into  the  coronary  veins. 

The  lymphatic  vessels  of  the  heart  form  a  net-work  beneath  the  visceral  layer 
of  the  pericardium,  and  a  second  less  distinct  net-work  has  also  been  described  as 
occurring  beneath  the  endocardium.  These  net-works  communicate  with  two  sets  of 
principal  vessels  which  lie  in  the  anterior  and  posterior  portions  of  the  auriculo-ven- 
tricular  groove.  The  anterior  set  passes  from  the  right  to  the  left,  and,  on  reaching 
the  pulmonary  aorta,  passes  around  its  left  surface  to  reach  the  systemic  aorta,  upon 
which  it  ascends  to  terminate  in  a  lymphatic  node  situated  to  the  left  of  the  trachea. 
The  posterior  set  opens  in  part  into  the  anterior  one  and  in  part  ascends  along  the 
right  side  of  the  pulmonary  aorta  to  terminate  in  one  of  the  nodes  situated  beneath 
the  bifurcation  of  the  trachea. 

The  Nerves  of  the  Heart. — The  nerves  of  the  heart  are  derived  from  the 
cardiac  plexuses  and,  passing  downward  along  the  aorte,  are  distributed  partly  to  the 
auricles  and  partly  accompany  the  coronary  arteries  along  the  auriculo-ventricular 
groove,  where  they  form  the  coronary  plexus,  from  which  branches  are  distributed 
to  the  ventricles.  Over  the  surfaces  of  the  auricles  and  ventricles  the  branches  form 
a  fine  plexus  situated  beneath  the  visceral  layer  of  the  pericardium,  and  from  this 
plexus  branches  pass  into  the  substance  of  the  heart  to  terminate  upon  the  muscle- 
fibres.  Some  nerve-fibres  are  also  distributed  to  the  pericardium  and  endocardium, 
and  these  are  regarded  as  being  afferent  in  function,  as  are  also  certain  fibres  which 
terminate  in  the  connective  tissue  of  the  heart's  walls. 

Scattered  in  the  superficial  plexuses  there  are  numerous  ganglion-cells,  some- 
times occurring  singly  and  sometimes  collected  into  small  ganglia.  They  tend  to  be 
especially  numerous  around  the  orifices  of  the  great  veins  opening  into  the  auricles, 
in  the  coronary  plexuses,  and  over  the  upper  portions  of  the  ventricles.  It  has  been 
asserted  that  ganglion-cells  also  occur  embedded  in  the  walls  of  the  ventricles,  but  at 
present  this  requires  confirmation. 

Much  has  yet  to  be  learned  concerning  the  qualities  of  the  various  nerve-fibres  which  pass  to 
the  heart  in  man,  but  it  is  presumable  that  they  resemble  in  general  those  which  have  been  deter- 
mined experimentally  for  those  of  the  lower  mammals.  In  the  latter  it  has  been  shown  that  the 
cardiac  plexuses  contain  both  afferent  and  efferent  nerve-fibres.  The  cardiac  plexuses  are  formed 
by  branches  from  the  pneumogastric  and  sympathetic  nerves,  and  among  the  fibres  from  the  former 
nerve  are  some  which,  when  stimulated,  cause  a  cessation  of  the  heart's  contractions,  whence 
they  are  termed  the  inhibitory  nerves.  Stimulation  of  sympathetic  fibres,  which,  in  the  dog,  for 
example,  pass  to  the  cardiac  plexus  from  the  first  thoracic  ganglion  of  the  ganglionated  cord, 
produces  an  increase  in  either  the  rapidity  or  the  intensity  of  the  heart-beat,  and  these  fibres  are 
consequently  termed  the  accelerator  or  augmentor  fibres.  Both  the  inhibitory  and  augmentor 
fibres  are  efferent, — i.e.,  they  carry  impulses  from  the  nerve-centres  out  to  the  heart ;  in  addi- 
tion, the  existence  of  afferent  fibres  has  been  determined  among  the  pneumogastric  constituents 
of  the  plexuses.  These  are  the  depressor  fibres,  so  called  because  their  stimulation  produces  a 
marked  fall  in  the  blood-pressure,  not  on  account  of  any  action  upon  the  heart-beat,  since  they 
lead  the  stimulus  away  from  the  heart,  but  by  acting  reflexly  upon  the  intestinal  vessels  so  as  to 
produce  their  dilatation  and,  by  thus  lessening  the  peripheral  resistance  against  which  the  heart 
must  contend,  lessen  the  work  which  the  organ  has  to  do. 

Whether  the  various  efferent  fibres  pass  directly  to  the  muscular  tissue  of  the  heart  or  ter- 
minate upon  cardiac  ganglion-cells  which  transmit  the  impulse  to  the  muscle-fibres  is  a  point 
which  remains  to  be  determined,  although,  from  analogy  with  what  is  known  as  to  the  relation 
of  the  cerebro-spinal  fibres  to  other  portions  of  the  involuntary  muscular  tissue,  it  would  seem 
probable  that  the  pneumogastric  efferent  fibres  terminate  primarily  upon  the  cardiac  ganglion- 
cells. 


THE    PRIMITIVE    HEART. 


705 


DEVELOPMENT  OF  THE  HEART. 

In  the  mammals  in  which  the  earliest  stages  in  the  development  of  the  heart  have 
been  observed,  this  organ  arises  as  two  separate  tubes  that  are  formed  by  folding  of 
the  visceral  mesoblast  near  the  margin  of  the  embryonic  area.  This  folding  occurs 
while  the  embryo  is  still  spread  out  upon  the  surface  of  the  yolk-sac  and  produces  on 
each  side  an  elevation,  a  heart-tube,  that  projects  into  the  primitive  body-cavity 
(Fig.  668).  Each  heart-fold  differentiates  into  a  thicker  outer  or  inyocardial  layer, 
which  gives  rise  to  a  portion  of  the  cardiac  muscle,  and  a  very  thin  inner  endocardial 
layer,  from  which  the  serous  lining  of  the  heart  is  derived.  The  latter  consists  of  a 
single  stratum  of  mesoblastic  cells  surrounded  by  the  muscle-layer,  but  separated  by 
a  distinct  space,  as  a  shrunken  cast  lies  within  its  mould. 

With  the  beginning  constriction  of  the  gut-tube  from  the  vitelline  sac  and  the 
associated  approximation  of  the  splanchnopleura  of  the  two  sides,  the  heart-tubes,  at 
first  widely  apart,  gradually  approach  the  mid-line  until  they  meet  beneath  the  ventral 
surface  of  the  primitive  pharynx,  in  advance  of  the  yolk-sac.  Upon  coming  into 
contact,  the  cavities  of  the  two  heart-tubes  for  a  brief  period  remain  separated  by  the 
partition  formed  by  the  opposed  portions  of  the  myocardial  layers.  Very  soon,  how- 
ever, solution  of  this  septum  occurs  and  the  two  sacs  become  a  single  heart.  The 
endothelial  tubes  are  last  to  fuse,  retaining  their  independence  after  the  myocardial 
walls  have  blended.  Upon  fusion  of  the  endothelial  layers  the  conversion  of  the  double 
tubes  into  a  single  heart  is 
complete.  Fig.  668. 

The  early  venous  trunks 
— the  body-stems  (cardinals 
and  jugulars)  within  the  em- 
bryo and  the  vitelline  and 
allantoic  (later umbilical)  veins 
from  the  extra  embryonic  vas- 
cular net-works — converge  to- 
wards a  common  sac,  the 
sinus  venosus,  which  joins  the 
caudal  end  of  the  cylindrical 
primitive  heart.  The  slightly 
tapering  cephalic  extremity  of 
the  latter  becomes  the  truncus 
arteriosus,  from  which  two  trunks,  the  ve?itral  aorttz,  are  prolonged  forward  beneath 
the  primitive  pharynx,  giving  off  the  aortic  bows  that  traverse  in  pairs  the  series  of 
visceral  arches.  The  primitive  heart  consists,  therefore,  of  a  cylinder,  somewhat 
contracted  at  its  anterior  end,  that  occupies  the  ventral  mid-line  in  the  later  cervical 
region.  The  blood  poured  into  the  sinus  venosus  by  the  veins  enters  its  posterior 
extremity  and  escapes  anteriorly  through  the  truncus  arteriosus. 

Although  for  a  brief  period  the  heart-tube  retains  its  median  position  and 
straight  cylindrical  form,  its  increasing  length  soon  causes  it  to  become  bent  upon 
itself  and  to  assume  the  S-like  contour  shown  in  Fig.  672  A,  from  an  embryo  of  2.15 
mm.  in  length,  in  which  the  venous  end  of  the  tube  lies  below  and  to  the  left  and 
the  arterial  trunk  above  and  to  the  right.  The  intermediate  portion  of  the  tube, 
extending  at  first  downward  and  then  obliquely  upward  and  towards  the  left,  is  the 
primitive  ventricle,  the  early  sigmoid  heart-tube  already  suggesting  the  recognition 
of  an  arterial,  ventricular,  and  venous  segment. 

During  the  further  development  of  the  heart  a  rearrangement  of  these  three 
divisions  takes  place,  since  the  venous  segment,  orginally  below,  gradually  acquires 
a  position  above  and  behind,  while  the  primitive  ventricle  comes  to  lie  in  front  and 
below  (Fig.  672).  With  the  completion  of  this  rotation,  a  deep  external  groove 
appears  between  the  ventricular  and  venous  chamber,  now  the  primitive  auricle,  that 
indicates  the  position  of  a  contracted  passage,  the  auricular  canal  (Fig.  672,  C),  as 
the  common  auriculo-ventricular  opening  is. termed.  Coincidently  with  the  upward 
migration  of  the  venous  segment,  a  lateral  outpouching  of  the  auricular  chamber 
appears  on  each  side  of  the  truncus  arteriosus.      These  expansions,  the  primary  au- 

45 


Transverse  sectic 
bryo,  showing  two  hi 
unclosed  digestive  tul 


ii  of  very  young  rabbit  em- 
art-tubes  widely  separated  by 
e.    X  150- 


706 


HUMAN   ANATOMY. 


ricular  appendages,  rapidly  increase,  until  they  form  the  most  conspicuous  part  of  the 
young  heart  (Fig.  673,  C),  embracing  the  upper  part  of  the  truncus  arteriosus  and 
overlying  the  ventricle. 

Meanwhile  the  ventricular  segment  has  assumed  the  most  dependent  and  ventral 
position,  for  a  time  appearing  as  a  transversely  expanding  sac  (Fig.  672,  £)  that  in 
form  recalls  a  greatly  dilated  stomach,  the  truncus  arteriosus  joining  the  "  pylorus," 
and  the  contracted  auricular  canal  suggesting  the  oesophagus.  Soon,  however,  the 
higher  right  end  of  the  ventricular  segment  sinks  to  the  level  and  gains  the  ventral 
plane  of  the  left  end,  the  ventricle  in  consequence  losing  in  width  but  gaining  in 
height.  A  shallow  longitudinal  crescentic  furrow,  the  later  interventricular  g?vove, 
now  appears  on  the  surface  of  the  ventricle  and  suggests  the  subdivision  of  this  seg- 
ment into  right  and  left 
Fig.  669.  chambers,     at     the     same 

time   indicating    the   posi- 
tion of  the  growing  inter- 
|W  nal  partition  that  leads  to 

this  separation. 

Sections  of  the  young 
heart    ( Fig.    670 )    show 
the  venous  and  ventricular 
segments    as   widely  com- 
municating portions  of  the 
sigmoid  tube,  the  walls  of 
which  are  composed  of  the 
myocardial    and    endothe- 
lial   layers.      In   somewhat 
older  embryos  (Fig.  671), 
the  communication  between 
these  divisions  of  the  heart- 
tube  exhibits  a  slight  con- 
traction, marking  the  posi- 
tion of   the  later  auricular 
canal,  which  becomes  a  nar- 
row   transverse    cleft    that 
connects  the  primitive  ven- 
tricle   with    the    auricular 
chamber.        The    myocar- 
dial   layer    of    the    heart- 
wall,     particularly    in    the 
ventricle,    also    shows    the 
beginning  of  the  trabecular 
that  invaginate  the  endo- 
thelial   lining    and    event- 
ually lead  to  the  conspicu- 
ous   modelling    of     the 
interior  of  the  adult  heart. 
Frontal  sections  of  the 
young  human  heart  (Fig.  674,  A)  show  the  commencing  separation  of  the  ventricular 
and  auricular  chambers  into  right  and  left  halves.      This  division  is  effected  by  the 
formation  of  a  vertical  partition  consisting  of  an  upper  auricular,  a  middle  valvular, 
and  a  lower  ventricular  part,  supplemented  by  the  aortic  septum  that  appears  in  the 
truncus  arteriosus  and  subdivides  the  latter  into  the  pulmonary  and  systemic  aortas 
The  subdivision  of  the  auricle,  which  anticipates  that  of  the  ventricle,  begins  in 
the  fourth  week  with  the  downward  extension  of  a  crescentic  fold,  the  auricular  sep- 
tum, or  septum  primum,  that  gradually  grows  from  the  postero-superior  wall  of  the 
auricle  towards  the  auricular  canal  and  fuses  with  the  partition  that,  as  the  septum 
intermedmm,  is  formed  within  the  canal  by  local  thickening  of  its  anterior  and  pos- 
terior lips.      In  this  manner  not  only  the  common  auricular  chamber,  but  also  the 
transversely  elongated  auriculo-ventricular  opening,  is  separated  into  a  right  and  a 


Posterior 
cardinal 
vein 


Right  umbilical  ve 

Right  vitell 


Reconstruction  of  upper  part  of  human  embryo  of  third 
week  (3.2  mm.),  showing  relation  of  heart  and  blood-vessels. 
X  50.     (Drawn  from  His  model.) 


DEVELOPMENT  OF  THE  HEART. 


707 


Neural  canal 


left  half.  The  interauricular  partition,  however,  is  not  complete,  since  an  opening 
appears  in  its  upper  part  even  before  it  has  finished  its  downward  growth  and  union 
with  the  valvular  septum.  This  opening  enlarges  and  remains  as  the  foramen  ovale 
that  persists  until  birth  as  a  direct  passage  for  the  blood  from  the  right  into  the  left 
auricle  during  the  continuance  of  the  fcetal  circulation  (page  929). 

The  subdivision  of  the  ventricular  chamber,  which  commences  a  little  later 
than  that  of  the  auricle,  is  accomplished  chiefly  by  the  formation  of  the  ventricular 
septum.  The  latter  grows  from  the  postero-inferior  wall  of  the  ventricle  as  a  cres- 
centic  projection  that  continues  inward,  a  thickening  of  the  ventricular  wall  corre- 
sponding in  position  with  the  external  interventricular  groove.  The  partition  thus 
formed  extends  towards  the  auriculo-ventricular  opening,  where  it  meets  and  fuses 
with  the  septum  intermedium,  in  this  manner  insuring  the  communication  of  the 
right  and  left  auricles  with  the  corresponding  ventricles  through  the  intervening 
respective  portions  of  the  valvular  opening. 

The  isolation  of  the  two  ventricles  from  each  other,  however,  is  not  at  first  com- 
plete, owing  to  the  ventricular  partition  being  imperfect  above  and  in  front.      This 
deficiency  is    overcome   by  the    down- 
ward   extension    of    the   aortic   septum  Fig.  670. 
within    the    bulbus    arteriosus    (as   the 
somewhat  dilated  lower  end  of  the  trun- 
cus    arteriosus    is     now    appropriately 
called)  until  it  meets  and  fuses  with  the 
ventricular    partition,    thus    completing 
the  separation  of  the  cardiac  chambers 
into  a  right  and  left  heart.      The  part 
of  the  ventricular  partition  contributed 
by  the  aortic  septum    always   remains 
thin  and  constitutes  the  pars  membran- 
acea  of  the  adult  organ. 

Coincidently  with  the  foregoing 
changes,  the  auricles  undergo  impor- 
tant modifications  in  their  relations  with 
the  blood-vessels  opening  into  them. 
During  the  development  of  the  auricles, 
the  oval  sinus  venosus,  into  which  is 
conveyed  the  blood  returned  by  the  vi- 
telline, allantoic  (umbilical)  and  body- 
veins,  elongates  transversely  into  a 
crescentic  sac,  the  convexity  of  which  is 
in  contact  with  the  back  of  the  auricles, 
its  opening  into  the  latter  having  shifted 
so  that  it  is  in  relation  with  only  the 
right  half  of  the  auricular  chamber.  With  the  expanded  body  and  right  horn  of 
the  venous  crescent  communicate  the  vessels  that  later  are  represented  by  "the  superior 
and  inferior  vena?  cavae,  while  the  elongated  and  smaller  left  horn  receives  the  left 
duct  of  Cuvier  that  becomes  the  coronary  sinus. 

For  a  time  the  opening  of  the  sinus  venosus,  or  sinus  reuniens  (His),  into  the 
heart  occupies  the  posterior  wall  of  the  right  half  of  the  auricle.  It  is  guarded  by 
the  venous  valve,  consisting  of  a  right  and  left  leaflet,  that  is  prolonged  forward 
along  the  roof  of  the  auricle  as  a  crescentic  ridge,  the  septum  spurium  (Fig.  674,  A). 
With  the  continued  appropriation  of  the  venous  sinus  by  the  expanding  auricle,  the 
single  aperture  of  the  sinus  disappears  as  the  sac  becomes  part  of  the  auricular 
chamber,  thereupon  the  two  venae  cavae  and  the  coronary  sinus  open  directly  into  the 
right  auricle  by  an  independent  orifice.  That  of  the  superior  cava  lies  in  the  upper 
posterior  part  of  the  auricle,  that  of  the  inferior  cava  being  lower  and  more  lateral, 
with  the  smaller  orifice  of  the  coronary  sinu,s  slightly  below.  The  septum  spurium, 
the  greater  part  of  the  left,  and  the  upper  part  of  the  right  segment  of  the  arching 
fold  that  originally  surrounds  the  opening  of  the  sinus  venosus  disappear  during  the 
appropriation  of  the  venous  sac  by  the  auricle.      The  lower  part  of  the  right  leaflet, 


Endocardial 
layer 


Myocardial 
layer 


Transverse  section. of  early  rabbit  em- 
bryo passing  througb  young  heart,  showing 
venous  segment  behind  and  arterial  in 
front.    X  75- 


708 


HUMAN   ANATOMY. 


on  the  contrary,  persists  and  differentiates  into  the  larger  Eustachian  valve,  that 
guards  the  lower  margin  of  the  inferior  vena  cava  and  directs  its  blood-stream  towards 
the  foramen  ovale,  and  the  smaller  Thebesian  valve,  that  protects  the  orifice  of  the 
coronary  sinus. 

As  above  noted,  the  separation  of  the  two  auricles  is  incomplete  on  account  of 
the  existence  of  the  foramen  ovale  within  the  interauricular  partition.  From  the  roof 
and  anterior  wall  of  the  right  auricle  an  additional  and  relatively  thick  crescentic  ridge, 
the  septum  secundum,  arches  around  the  foramen  ovale  of  which  it  forms  the  anterior 
or  ventral  boundary.  It  lies  close  to  and  parallel  with  the  auricular  septum  and 
fuses  below  with  the  lower  part  of  the  left  segment  of  the  venous  valve  to  form  the 
limbtis  Vietissenii  that  later  limits  the  fossa  ovalis,  marking  the  former  position  of  the 
foramen  ovale.  The  latter,  therefore,  is  included  between  two  partially  overlapping 
crescentic  margins,  that  contributed  by  the  septum  auriculum  lying  behind  and  to  the 
left,  and  that  by  the  septum  secundum  in  front  and  to  the  right,  a  narrow  sagittal 

cleft  intervening  so  that  the  surfaces  of 
Fig.  671.  the  lunate  borders  are  not  in  contact. 

Since  the  division  of  the  heart  into 
a  right  and  left  side  is  inseparably  con- 
■:.■■•  nected   with    the   development    of    the 

il -.' '■'  -  .    'v.'\  lungs  and  the  consequent  necessity  for 

.  .'  '         .'i'\  a  distinct  pulmonary  circulation,  provis- 

x—l4~ Aorta  ion  for  the  return  of  the  blood  from  the 

lungs  to  the  heart  is  made  by  the  early 
formation  of  the  ptclmotiary  veins. 
These  arise  in  pairs,  one  pair  for  each 
lung;  close  to  the  heart  each  pair  unites 
into  a  single  right  or  left  stem  that,  in 
turn,  joins  with  its  fellow  <5f  the  oppo- 
site side  to  form  one  short  common 
trunk.  For  a  time  none  of  these  ves- 
sels communicate  with  the  heart,  but 
later  the  common  single  pulmonary  vein 
opens  into  the  left  auricle  close  to  the 
septum.  With  the  subsequent  growth 
and  expansion  of  the  auricles  an  appro- 
priation occurs  on  the  left  side  similar  to 
that  affecting  the  sinus  venosus  on  the 
right,  in  consequence  of  which  the  short 
common  pulmonary  vein  is  first  drawn 
into  the  heart,  to  be  followed  next  by 
the  two  secondary  and,  finally,  by  the 
four  primary  pulmonary  veins,  all  of 
which  then  open  by  separate  orifices 
into  the  enlarging  left  auricle.  The  fre- 
quent variations  in  the  number  of  the  pulmonary  veins  and  in  their  relations  to  the 
heart  are  usually  to  be  referred  to  arrest  or  modification  of  this  foetal  appropriation. 

The  differentiation  of  a  right  and  left  auriculo-ventricular  valve  proceeds  from  the 
subdivision  of  the  auricular  canal  by  the  septum  intermedium.  The  latter  is  formed 
by  the  approximation  and  union  of  the  median  cushion-like  projections  upon  the 
ventral  and  dorsal  walls  of  the  common  auriculo-ventricular  opening.  The  unob- 
literated  lateral  portions  of  the  latter  are  triangular  in  outline  and  guarded  by  pro- 
liferations of  the  endocardium.  Those  of  the  lower  margins  of  the  valves  elongate 
and  project  into  the  ventricles  on  the  right  side,  giving  rise  to  two  leaflets,  and  on  the 
left  to  a  single  flap.  An  additional  prolongation  from  the  partition  contributes  a 
septal  leaflet  on  each  side.  In  this  manner  the  complement  of  flaps  for  the  tricuspid 
and  bicuspid  (mitral)  valves  is  early  provided.  The  close  relation  between  the  leaf- 
lets and  the  attached  restraining  bands,  the  chordae  tendinese,  results  from  the 
secondary  union  of  the  immature  flaps  with  the  trabecular  of  the  spongy  myocardium 
of  the  young  heart.      The  loose  muscular  walls  undergo  partial  consolidation,  so  that 


Truncus  arteriosus 


Transverse  section  of  somewhat  older  er 
bryo,  showing  differentiation  into  auricle 
ventricle  and  truncus  arteriosus.    X  75. 


DEVELOPMENT   OF    THE    HEART. 


709 


the  outer  strata  of  the  ventricular  muscle  become  compact  while  the  inner  layers  for 
a  time  retain  their  characteristic  trabecular.  Those  attached  to  the  valves  undergo 
thickening  and  consolidation  and  become  the  papillary  muscles;  a  few  persist  as  ties 

Fig.  672. 


Reconstructions  of  developing  hearts;  A,  from  human  embryo  of  about  14  days  (2. 
(4.2  mm.)  ;  C,  of  23  days  (4.3  mm.)  ;  la,  truncus  arteriosus:  pv,  primitive  ventricle; 
right  and  left  auricular  appendages  ;  avc,  auriculo-ventricular  canal.     X  20.     (Drawn ft 

Fig.  673. 


Reconstructions  of  developing  hearts;  A,  from  human  embryo  of  25  days  (5  mm.  greatest  length);  i?.  endo- 
thelial heart  from  same;  C,  of  35  days  (13.7  mm.);  ra,  la,  right  and  left  auricles  represented  by  large  auricular 
appendages ;  rv,  Iv,  right  and  left  ventricles  ;  la,  truncus  arteriosus ;  e,  endothelial  tube  ;  ac,  auriculo-ventricular 
canal;  ag,  interventricular  groove.     X  20.     (Drawn  from  His  models.) 


Fig.  674. 


Reconstructions  of  developing  hearts;  .4,  posterior  half  of  heart  of  human  embryo  of  30  days  (10  mm.)  seen 
from  in  front ;  B,  same  from  embryo  of  35  days  (Cm  preceding  figure);  C,  same  heart  opened  on  right  side  showing 
imperfect  septa  ;  as,  auricular  septum  ;  vs,  ventricular  septum;  jj,  septum  spurtum  ;  sr,  sinus  reuniens;  vv,  venous 
valve ;  si,  septum  intermedium  ;  rv,  Iv,  right  and  left  ventricles  ;  la,  left  auricle  :  rav,  lav,  right  and  left  auriculo- 
ventricular  valves  ;  fo,  foramen  ovale,  occupied  in  A  and  B  by  arrow ;  sse,  septum  secundum  ;  Ivv,  left  leaflet  of 
venous  valve;  scic,  superior  and  inferior  vena  cava ;  cs,  coronary  sinus;  Idc,  left  duct  of  Cuvier;  aos,  aortic 
septum  in  truncus  arteriosus.     X  20.     (Drawn from  His  models.) 


or  moderator  bands;  while  the  majority  retain  their  freedom  to  a  lesser  degree  and,  as 
the  columnar  carnea;,  produce  the  conspicuous  modelling  of  the  interior  of  the  ven- 
tricles.     The  muscular  tissue,  which  at  first  extended  to  and  even  within  the  valve- 


7io  HUMAN    ANATOMY. 

leaflets,  subsequently  undergoes  partial  atrophy  and  disappears  from  the  flaps  and 
adjoining  parts  of  the  attached  bands,  the  latter  thereby  being  converted  into  the 
fibrous  chorda?  tendineae. 

Even  before  the  longitudinal  subdivision  of  the  bulbus  arteriosus  occurs,  the 
junction  of  this  tube  with  the  primary  ventricle  is  marked  by  four  cushion-like  thick- 
enings that  project  from  the  interior  of  the  bulb.  These  elevations,  which  consist  of 
immature  connective  tissue  covered  by  endothelium,  furnish  the  leaflets  of  the  aortic 
and  pulmonary  semilunar  valves.  The  formation  of  the  aortic  septum  within  the 
bulbus  arteriosus  begins  some  distance  above  the  valve  and  immediately  below  the 
origin  of  the  right  and  left  pulmonary  arteries.  From  this  point  the  partition  gradu- 
ally grows  downward  until  it  encounters  the  elongated  lateral  pair  of  the  original  four 
valve-cushions,  of  which  one  lies  in  front,  one  behind,  and  two  at  the  sides  of  the  bulb. 
With  the  completion  of  the  division  of  the  bulbus  arteriosus  into  the  systemic  and 
pulmonary  aortae,  the  septum  cleaves  the  two  lateral  cushions,  each  of  the  resulting 
valves  being  guarded  by  three  leaflets  so  disposed  that  the  original  and  undivided 
flap  of  the  pulmonary  artery  lies  in  front,  and  that  of  the  aorta  behind.  The  partial 
rotation  that  later  places  the  aortic  valve  behind  and  to  the  left  of  the  pulmonary 
brings  about  the  disposition  observed  in  the  adult  (page  700),  in  which  the  single 
leaflet  of  the  aortic  semilunar  valve  lies  in  front  and  that  within  the  pulmonary  artery 
is  behind.  At  first  comparatively  thick,  the  leaflets  suffer  partial  absorption,  whereby 
they  are  converted  into  the  membranous  cusps  that  bound  crescentic  pouches,  the 
sinuses  of  Valsalva,  which  lie  between  the  leaflets  and  the  wall  of  the  vessels. 

PRACTICAL    CONSIDERATIONS  :    THE    HEART. 

It  is  possible  here  only  to  indicate  with  great  brevity  certain  changes  in  the 
position  of  the  heart  which  should  be  studied  in  connection  with  its  relations. 

The  apex  beat,  normally  to  be  found  about  one  inch  below  and  two  inches  to  the 
sternal  side  of  the  left  nipple,  is  due  to  the  recoil  of  the  left  ventricle  as  it  empties  its 
contents  into  the  aorta,  to  the  lengthening  of  that  vessel  as  the  blood  enters  it,  to  the 
consequent  straightening  of  the  arch  (carrying  the  heart  forward),  and  to  the  absence 
of  any  interposed  lung-tissue  over  the  '  'area  of  absolute  dulness. ' ' 

The  apex  beat  (and  usually  the  heart  itself)  is  («)  raised  in  cases  of  ascites, 
tympanites,  large  abdominal  tumors,  and  atrophic  pulmonary  conditions  ;  (&)  de- 
pressed in  aortic  aneurism,  mediastinal  growths,  pulmonary  emphysema,  pleural 
effusion,  and  hypertrophy  or 'dilatation  of  the  left  ventricle  ;  (c)  displaced  laterally 
to  the  right  by  left  pleural  effusion,  splenic  tumors,  hypertrophy  of  the  right  ventri- 
cle, to  the  left  by  hepatic  tumors,  right  pleural  effusion,  hypertrophy  of  the  left  ven- 
tricle. The  heart  may  be  drawn  to  either  side  by  contracting  pleural  adhesions. 
As  the  area  of  absolute  dulness — "superficial  cardiac  area" — corresponds  to  that 
portion  of  the  cardiac  substance  which  is  not  separated  by  pulmonary  tissue  from 
the  thoracic  wall,  it  follows  that  its  extent  varies  inversely  with  the  size  or  expansion 
of  the  lungs.  In  emphysema  the  area  of  cardiac  dulness  may  quite  disappear  ;  in 
the  later  stages  of  fibroid  phthisis  it  may  be  much  larger  than  normal. 

In  relation  to  the  anatomy  of  the  valves  and  cavities  of  the  heart,  the  sounds 
produced  by  the  passage  of  blood  through  them  should  be  considered  in  connection 
with  at  least  a  few  of  the  modifications  caused  by  the  chief  pathological  changes  that 
affect  that  organ.  It  may  be  said  here,  for  the  sake  of  clearness,  that  the  first  sound 
occurs  during  the  contraction  of  the  ventricles,  when  the  auriculo-ventricular  open- 
ings should  be  closed  by  the  mitral  and  tricuspid  valves  and  the  aortic  and  pul- 
monary orifices  should  be  open,  and  that  it  is  due  to  (a)  the  shutting  of  the  valves, 
and  (b)  the  impulse  of  the  apex  against  the  thoracic  wall,  with  possibly  some  addi- 
tion from  (c)  the  contraction  of  the  walls  of  the  ventricles,  although  this  latter  factor 
is  doubtful. 

The  second  sound  occurs  during  the  auriculo-ventricular  dilatation,  and  is  due  to 
the  closure  of  the  pulmonary  and  aortic  semilunar  valves  caused  by  the  recoil  of  the 
blood-current  brought  about  by  the  elastic  coats  of  the  aorta  and  pulmonary  arteries. 

If  a  murmur  heard  over  the  chest  is  synchronous  with  the  radial  pulse  (systolic), 
it  occurs  during  ventricular  contraction,  and  is  usually  due  either  {a)  to  regurgita- 


PRACTICAL   CONSIDERATIONS:    THE   HEART.  711 

tion  of  blood  through  an  auriculo-ventricular  valve  that  does  not  accurately  close  the 
corresponding  opening  or  (^)  to  an  obstruction  to  the  exit  of  blood  from  the  ven- 
tricle at  the  aortic  or  at  the  pulmonary  orifice. 

If  a  heart  murmur  is  not  synchronous  with  the  radial  pulse  (diastolic  or  pre- 
systolic), it  may  be  caused  by  («)  obstruction  to  the  passage  of  blood  from  an 
auricle  into  a  ventricle  (mitral  or  tricuspid  stenosis);  or  (b)  regurgitation  from  the 
pulmonary  artery  or  aorta  into  the  right  or  left  ventricle  (pulmonary  or  aortic  insuf- 
ficiency). 

Of  these  various  murmurs  those  due  to  mitral  and  aortic  insufficiency  are  by  far 
the  most  frequent. 

Valvular  disease  of  the  left  side  of  the  heart  (90  per  cent,  of  all  cases)  is  more 
frequent  on  account  of  the  greater  work  required  of  this  side  and  the  associated 
greater  liability  to  strain,  rarely  sudden,  usually  trifling  but  oft  repeated. 

1.  Mitral  insufficiency — an  imperfect  closure  of  the  segments  of  the  left  auriculo- 
ventricular  valve — causes  a  systolic  murmur,  heard  best  (a)  over  the  apex  and  super- 
ficial cardiac  area  because  there  the  ear  can  most  nearly  approach  the  left  ventricle 
without  the  interposition  of  pulmonary  tissue  or  of  the  right  ventricle  ;  ($)  in  the 
axilla,  because  it  is  transmitted  in  the  direction  of  the  arterial  blood-current  ;  and  (c) 
at  the  angle  of  the  left  scapula,  or  between  the  fifth  and  eighth  thoracic  vertebra?,  for 
the  same  reason,  and  because  at  that  point  the  left  ventricle  is  posterior.  In  addi- 
tion, the  pulmonary  second  sound  is  louder  and  sharper  than  natural  (accentuated) 
because  of  the  following  series  of  occurrences  which  should  be  studied  in  connection 
with  the  structures  and  cavities  involved  :  over-filling  and  distention  of  the  left 
auricle,  imperfect  emptying  of  the  pulmonary  veins,  pulmonary  congestion  and  re- 
sistance to  the  systole  of  the  right  ventricle,  increased  fulness  of  the  pulmonary  arter- 
ies, and  corresponding  increase  of  the  backward  pressure  upon  the  pulmonary 
valves,  shutting  them  more  sharply  and  forcibly  (accentuation). 

Furthermore,  as  the  distention  of  both  ventricles  results  in  hypertrophy,  the 
transverse  diameter  of  the  area  of  cardiac  dulness  is  distinctly  increased. 

2.  In  mitral  stenosis  (often  associated  with  some  degree  of  mitral  insufficiency) 
a  murmur  is  usually  heard,  preceding  the  pulse-beat  (presystolic), — corresponding, 
that  is,  to  the  auricular  systole,  and,  as  the  left  auricle  is  distended — from  imperfect 
emptying — and  hence  the  pulmonary  veins  and  arteries  and  the  right  heart  are 
in  the  same  condition,  there  is  again  a  loud  accentuation  of  the  second  sound. 

3.  Aortic  insufficiency  is  characterized  by  a  murmur  that  follows  the  radial 
pulse  (diastolic),  occurs  as  the  blood  is  being  driven  back  into  the  ventricle  by  the 
elastic  aorta,  is  heard  best  over  the  sternal  end  of  the  second  right  intercostal  space 
(vide  supra'),  is  often  propagated  towards  the  xiphoid  cartilage  or  down  the  left  side 
of  the  sternum,  and  is  more  rarely  heard  in  the  carotid  or  axillary  vessels, — i.e. ,  as 
it  is  a  murmur  primarily  due  to  the  reflux  of  blood  from  the  aorta  into  the  ventricle, 
it  is,  in  accordance  with  well-known  laws  of  physics,  transmitted  in  the  direction  of 
the  current  causing  it. 

The  great  distention  and  subsequent  hypertrophy  of  the  left  ventricle  caused  by 
its  inability  to  empty  itself  result  in  a  marked  increase  of  percussion  dulness.  As 
the  aortic  valves  do  not  come  together  normally,  the  aortic  second  sound  is  feeble  or 
absent. 

4.  Aortic  stenosis  (much  less  frequent  than  insufficiency)  is  usually  accompanied 
by  a  systolic  murmur  heard  at  the  aortic  cartilage  and  transmitted  along  the  great 
vessels  to  the  axilla,  to  the  neck,  and  along  the  spine,  but  difficult  to  distinguish  from 
similar  murmurs  caused  by  disease  of  the  inner  coat  of  the  aorta  or  by  mere 
roughening  of  the  valves.  As  the  aorta  receives  a  diminished  quantity  of  blood, 
one  factor  in  the  production  of  the  apex  beat  is  lessened  in  effectiveness  and  the 
cardiac  impulse  is  often  also  lessened.  Dilatation  and  hypertrophy  of  the  left  ven- 
tricle with  subsequent  secondary  changes  in  the  other  cavities  may  follow,  but  are 
not  nearly  so  marked  as  in  aortic  insufficiency. 

Valvular  disease  of  the  right  side  of  the  heart  may,  on  account  of  its  relative 
infrequency  and  to  avoid  repetition,  be  even  more  briefly  summarized  : 

1.  Tricuspid  insufficiency — -often  following  pulmonary  conditions  obstructing  the 
circulation — is  characterized  by   (a)   a   low  systolic   murmur   heard  well  over  the 


712  HUMAN    ANATOMY. 

lower  sternum  on  account  of  the  relation  of  the  right  auriculo-ventricular  orifice  to 
the  middle  of  that  bone  ;  (b)  increase  of  percussion  area  to  the  right  of  the  sternum 
because  of  the  distention  and  dilatation  of  the  right  auricle  that  follow  ;  and,  (c)  from 
the  same  cause  and  the  resultant  backward  pressure  on  the  systemic  veins,  a  venous 
pulse-wave,  seen  best  in  the  internal  and  external  jugular  on  the  right  side,  but  not 
infrequently  recognizable  on  both  sides,  in  the  subclavian  and  axillary  veins  also,  or 
as  a  systolic  expansile  impulse  in  the  liver  transmitted  through  the  inferior  cava  and 
hepatic  veins. 

2.  Tricuspid  stenosis,  like  that  of  the  mitral  valve,  is  apt  to  cause  a  presystolic 
murmur,  and  for  the  same  physical  reasons. 

3  and  4.  Pulmonary  insufficiency  and  stenosis  (disease  of  the  pulmonary  valves) 
are  so  rare  and  so  uncertain  in  their  physical  signs  as  to  require  mention  merely  to 
complete  the  survey  of  the  group. 

The  various  forms  and  degrees  of  hypertrophy  or  dilatation  of  the  heart  which 
are  associated  with  the  foregoing  conditions  can  be  readily  understood  by  con- 
sidering the  increased  resistance  and  correspondingly  increased  exertion  which  are 
brought  about  by  the  valvular  changes.  The  essential  cause  of  hypertrophy  in  the 
heart,  as  in  other  muscles,  is  increased  work.  The  etiological  factors  which  neces- 
sitate this  should  be  studied  in  connection  with  the  anatomy  of  the  heart  and  have 
been  well  summarized  by  Osier. 

Hypertrophy  of  the  left  ventricle  alone,  or  with  general  enlargement  of  the  heart, 
is  brought  about  by — 

(a)  Conditions  affecting  the  heart  itself  :  (1)  Disease  of  the  aortic  valve  ;  (2) 
mitral  insufficiency;  (3)  pericardial  adhesions  ;  (4)  sclerotic  myocarditis  ;  (5)  dis- 
turbed innervation  with  overaction,  as  in  exophthalmic  goitre,  in  long-continued 
nervous  palpitation,  or  as  a  result  of  the  action  of  certain  articles,  such  as  tea,  alcohol, 
and  tobacco.  In  all  of  these  conditions  the  work  of  the  heart  is  increased.  In  the 
case  of  the  valve  lesions  the  increase  is  due  to  the  increased  intraventricular  pressure  ; 
in  the  case  of  the  adherent  pericardium,  or  the  myocarditis,  to  direct  interference  with 
the  symmetrical  and  orderly  contraction  of  the  chambers. 

(b)  Conditions  acting  upon  the  blood-vessels  :  (1)  General  arterio-sclerosis, 
with  or  without  renal  disease  ;  (2)  all  states  of  increased  arterial  tension  induced  by 
the  contraction  of  the  smaller  arteries  under  the  influence  of  certain  toxic  substances  ; 
(3)  prolonged  muscular  exertion,  which  enormously  increases  the  blood-pressure  in 
the  arteries  ;   (4)  narrowing  of  the  aorta,  as  in  congenital  stenosis. 

Hypertrophy  of  the  right  ventricle  is  met  with  under  the  following  conditions  : 

(1)  Lesions  of  the  mitral  valve,  either  incompetence  or  stenosis,  which  act  by  in- 
creasing the  resistance  in  the  pulmonary  vessels  ;  (2)  pulmonary  lesions  with  obliter- 
ation of  any  considerable  number  of  blood-vessels  within  the  lungs,  such  as  occurs 
in  emphysema  or  cirrhosis  ;  (3)  valvular  lesions  on  the  right  side  occasionally,  and 
not  infrequently  in  the  fcetus  ;  (4)  chronic  valvular  disease  of  the  left  heart  and 
pericardial  adhesions. 

In  the  auricles  simple  hypertrophy  is  never  seen  ;  it  is  always  dilatation  with 
hypertrophy.  In  the  left  auricle  the  condition  develops  in  lesions  at  the  mitral  orifice, 
particularly  stenosis.  The  right  auricle  hypertrophies  when  there  is  greatly  increased 
blood-pressure  in  the  lesser  circulation,  whether  duetto  mitral  stenosis  or  to  pulmo- 
nary lesions.   Narrowing  of  the  tricuspid  orifice  is  a  less  frequent  cause. 

Hypertrophy  or  dilatation  of  the  cardiac  chambers  may  cause  pressure,  some- 
times injurious,  on  surrounding  structures. 

Great  enlargements  of  the  left  ventricle,  as  seen  in  the  bovine  heart  of  valvular 
disease,  may  occasion  compression  of  the  lower  portion  of  the  left  lung  when  a  devi- 
ation of  the  mediastinum  towards  the  right  is  prevented.  As  a  rule,  such  enlarge- 
ment compresses  the  lower  part  of  the  left  lung  comparatively  little.  Enlargement 
of  the  right  ventricle  frequently  causes  a  depression  and  forward  displacement  of  the 
left  lobe  of  the  liver  and  the  appearance  of  a  pulsating  mass  in  the  epigastrium. 

Dilatation  of  the  auricles  is  more  likely  to  produce  serious  compression  of  sur- 
rounding structures  than  is  that  of  the  ventricles  because  of  the  greater  fixation  of  the 
heart  at  its  upper  portion  where  the  auricles  are  placed.  Enlargement  of  the  left 
auricle  has  in  some  cases  produced  compression  of  the  left  bronchus  with  consequent 


PRACTICAL    CONSIDERATIONS:    THE    HEART.  713 

collapse  of  the  lung.  Enlargement  of  the  right  auricle  seems  to  be  the  basis  of  the 
frequently  occurring  right-sided  hydrothorax  of  valvular  heart  disease.  Compression 
of  the  azygos  vein  and  perhaps  of  the  veins  and  lymphatics  at  the  root  of  the  right 
lung  by  the  enlarged  auricle  accounts  for  the  occurrence  of  one-sided  hydrothorax 
(Stengel). 

Rupture  of  the  heart  is  usually  secondary  to  fatty  degeneration  of  the  cardiac 
muscles.  It  may  follow  a  complete  embolic  obstruction  of  one  of  the  branches  of 
the  coronary  arteries.  Arterio-sclerosis  with  slow  obliteration  of  one  or  both  of 
these  arteries  may  result  in  such  atrophy  of  the  myocardium  as  to  favor  rupture,  and 
this  atrophy  is  hastened  by  the  fact  that  there  is  no  direct  anastomosis  between  the 
branches  of  these  vessels  (page  703).  With  any  of  these  predisposing  conditions 
present,  rupture  may  follow  unusual  exertion,  or  a  heavy  fall,  or  direct  violence  to 
the  precordium,  or  may  occur  spontaneously.  The  right  side  of  the  heart  is  the 
more  frequently  involved,  the  right  auricle  especially  ;  but  the  cavities  implicated,  in 
order  of  frequency,  are  the  right  auricle,  left  ventricle,  left  auricle,  right  ventricle. 
This  order  probably  results  from  the  facts  that  (a)  the  right  auricle  is  the  weakest 
part  of  the  heart ;  (6)  the  left  ventricle,  though  normally  the  strongest  part,  stands 
second  because  it  is  specially  liable  to  the  myocardial  degenerations  that  result  from 
coronary  arterio-sclerosis  ;  (c)  the  left  auricle  and  the  right  ventricle,  though  weaker 
than  the  left  ventricle,  are  less  frequently  affected  because  they  are  not  so  liable  to 
such  degeneration. 

Woicnd  of  the  heart  is  not  necessarily  fatal.  A  stab  wound  may  be  followed  by 
little  or  no  hemorrhage  owing  to  the  anatomical  arrangement  of  the  muscular  fibres, 
some  of  which,  whatever  the  direction  of  the  wound,  escape  division.  The  thicker 
the  cardiac  wall  at  the  site  of  the  wound  the  more  numerous  the  fibres  and  the 
more  effective  their  action  in  preventing  hemorrhage  ;  hence  wounds  of  the  auricles 
are  more  certainly  and  more  rapidly  fatal  than  wounds  of  the  ventricles,  and  wounds 
of  the  right  ventricle  are  graver  than  those  of  the  left.  Pain  and  syncopal  attacks 
are  almost  always  present.  Hemorrhage  into  the  pericardium  will  be  attended  by 
great  precordial  oppression,  there  will  be  increase  of  the  area  of  cardiac  dulness, 
and  indistinctness  or  feebleness  of  all  the  heart  sounds. 

The  anterior  surface  of  the  heart  is  most  frequently  wounded.  The  overlapping 
of  the  pleura  (page  i860)  leads  to  its  usual  involvement  in  wounds  of  the  heart  or  peri- 
cardium, except  those  that  reach  the  latter  through  those  areas  of  the  sternum  with 
which  they  are  in  direct  relation.  Accordingly,  in  most  heart  wounds  a  pleural  cavity 
— commonly  the  left — is  found  to  contain  blood.  As  the  anterior  margin  of  the  lung 
is  also  apt  to  be  involved,  except  when  the  wound  is  within  the  bounds  of  the  area 
of  cardiac  dulness,  the  blood  in  both  the  pleural  and  pericardial  cavities  may  be  frothy. 
The  right  auricle  and  ventricle  and  the  left  coronary  vessels — running  in  the 
anterior  interventricular  groove — are  most  frequently  wounded  ;  the  right  auricle  if 
the  wound  passes  through  the  inner  end  of  the  right  third,  fourth,  or  fifth  intercostal 
space  ;  the  right  ventricle  if  it  passes  through  a  corresponding  space  to  the  left  of  the 
sternum. 

As  40  per  cent,  of  the  reported  cases  operated  upon  for  heart-wounds  have 
recovered,  it  may  be  well  to  associate  the  study  of  the  normal  heart  with  that  of  the 
best  method  of  gaining  access  to  it  for  surgical  purposes. 

The  heart  should  be  exposed  by  a  flap,  the  lower  border  of  which  corresponds 
to  the  sixth  interspace,  the  inner  border  to  the  left  border  of  the  sternum,  and  the 
upper  border  to  the  third  or,  if  the  wound  is  high  up,  to  the  second  interspace. 
The  cartilages  of  the  corresponding  ribs  are  divided  and  the  flap  is  raised,  separated 
if  possible  from  the  pleura,  and  turned  outward  by  fracturing  the  ribs.  The  pleura 
is  separated  from  the  pericardium,  to  which  it  does  not  adhere  very  closely, 
beginning  towards  the  middle  line.  The  pericardium  is  then  incised  and  the  accu- 
mulated blood  evacuated,  which  is  often  a  great  relief  to  the  heart,  to  which  the  pulse 
quickly  responds.  Two  fingers  are  now  inserted  below  and  behind  the  apex  and 
the  heart  tilted  forward  and  sutured.  If  a  second  wound — that  of  exit — is  suspected, 
it  may  be  found  by  twisting  the  heart  gently  to  the  right  or  left.  The  sutures  should 
go  down  to  the  endocardium,  but  should  not  enter  the  cavities  of  the  heart.  The 
pericardium  is  then  closed,  the  pleura  replaced,  and  the  flaps  sutured  in  position. 


7H 


HUMAN  ANATOMY. 


The  same  incision — or  an  extension  downward  of  this  one — will  permit  of  suffi- 
cient exposure  of  the  heart  for  cardiac  massage,  a  method  of  resuscitation  in  des- 
perate cases  of  syncope  during  anaesthesia  which  has  been  recently  employed,  but 
the  value  of  which,  if  it  has  any,  cannot  now  be  estimated. 

THE    PERICARDIUM. 

The  pericardium  is  the  serous  sac  which  encloses  the  heart  and  the  proximal  por- 
tions of  the  great  vessels.  Like  other  serous  sacs,  it  consists  of  two  layers,  one  of 
which,  the  visceral  layer,  closely  invests  the  heart  and  at  its  base  becomes  continuous 
with  the  parietal  layer,  within  which  it  is  invaginated. 

The  visceral  layer,  sometimes  termed  the  epicardium,  is  an  exceedingly  thin 
membrane,  and  is  throughout  the  greater  part  of  its  extent  so  closely  adherent  to  the 
outer  surface  of  the  heart  that  any  attempt  to  detach  it  results  in  injury  to  the  super- 
ficial layers  of  the  heart  musculature.  Over  the  right  side  and  the  anterior  surface 
of  the  ventricular  portion  of  the  heart,  however,  a  certain  amount  of  fat,  even  in  thin 
persons,  occurs  between  the  muscular  tissue  and  the  epicardium. 


Fig 


Vena  azygos 

VIII.  thoracic  vertebra 


Thoracic  aorta' 


i  of  cross-section  of  body  at  level  of  eighth  thoracic  vertebra, 
showing  heart  enclosed  by  pericardium. 


ed  from  above. 


The  parietal  layer,  much  stronger  than  the  visceral,  forms  a  somewhat 
conical  sac,  the  base  of  which  rests  upon  and  is  attached  to  the  diaphragm,  while  its 
apex  surrounds  the  roots  of  the  aorta;.  Notwithstanding  its  greater  size,  no  cavity 
exists  normally  between  this  and  the  visceral  layer,  the  two  being  in  contact 
throughout,  except  below,  where,  towards  the  periphery  of  the  base  of  the  parietal 
cone,  a  slight  space  occurs  which  is  normally  occupied  by  a  quantity  of  pericardial 
fluid  {liquor pericardii). 

At  the  sides,  and  to  a  considerable  extent  on  its  anterior  surface,  the  parietal 
layer  of-  the  pericardium  is  united  to  or  is  in  close  contact  with  the  adjacent  pleurae. 
At  the  upper  part  of  its  anterior  surface  where  it  covers  the  aorta  it  is  free  from  such 
contact,  and  over  a  triangular  area  near  the  base  of  the  cone  the  anterior  surface 
rests  upon  the  posterior  surface  of  the  lower  part  of  the  sternum,  to  which  it  is 
united  by  some  loose  areolar  tissue.  Posteriorly  it  is  free  to  a  considerable  extent 
from  the  pleura;,  that  portion  of  it  which  covers  the  posterior  surface  of  the  left 
auricle  resting  upon  the  cesophagus  and  the  thoracic  aorta.  The  base  of  the  cone 
is  firmly  united  to  the  upper  surface  of  the  diaphragm  throughout  its  entire  extent, 
the  area  of  attachment  corresponding  to  the  anterior  and  a  portion  of  the  left  lobe  of 
the  central  tendon. 


THE    PERICARDIUM. 


715' 


Above,  as  has  been  stated,  the  parietal  layer  extends  upward  some  distance  upon 
the  proximal  portions  of  the  systemic  and  pulmonary  aortae  before  passing  over  into  the 
visceral  layer,  but  the  amount  to  which  the  two  vessels  are  invested  differs  considerably. 
If  the  parietal  layer  be  cut  away  along  the  line  at  which  it  becomes  continuous  with 
the  visceral  layer,  two  distinct  lines  will  be  found  indicating  its  attachments.  One  of 
these  surrounds  the  two  aortse  (Fig.  654),  which  are  united  by  connective  tissue,  and 
extends  upward  upon  the  systemic  aorta  to  a  point  a  little  below  the  origin  of  the 
innominate  artery,  a  level  which  corresponds  very  nearly  with  the  upper  border 
of  the  second  costal  cartilage;  upon  the  pulmonary  aorta  (artery)  the  line  does  no*-, 
rise  quite  so  high,  reaching  to  a  point  a  little  below  where  the  vessel  divides  into 
the  right  and  left  pulmonary  arteries.  The  other  line  of  attachment  is  much  more 
extensive  and  complicated   (Fig.  655).      Starting  from   its  attachment  to   the  left 

Fig.  676. 


Stemo-thyroid  muscle 

Sterno-hyoid  muscle 

Steru.1-.  Mdo-iii.iMnkl  muscle 
Right  subclavian  artery 


I.  costal  cartilag 


Anterior  thoracic  wall  has  been  partly  removed,  leaving  left  half  of  sternum  and  some 
ribs  in  place  ;  lungs  have  been  drawn  aside  to  expose  pericardial  sac. 


pulmonary  veins,  upon  which  it  ascends  for  a  short  distance,  it  passes  directly  across 
the  posterior  surface  of  the  left  auricle  to  the  base  of  the  right  pulmonary  veins,  and 
is  thence  continued  downward  to  surround  the  vena  cava  inferior  close  to  its  entrance 
into  the  right  auricle.  Thence  it  passes  upward  to  regain  the  right  pulmonary  veins, 
and  is  then  continued  around  the  vena  cava  superior,  upon  which  it  rises  to  a  height 
of  about  3  cm.  It  then  passes  towards  the  left  over  the  posterior  surface  of  the 
auricles  to  reach  the  starting-point  at  the  left  pulmonary  veins. 

The  existence  of  these  two  separate  lines  of  attachment  is  due  to  a  difference  in 
the  arrangement  of  the  visceral  and  parietal  layers  in  the  interval  between  the  aortse 
and  the  anterior  surface  of  the  auricles.  The  parietal  layer  passes  directly  across 
from  the  aortas  to  the  auricles,  while  the  visceral  layer  forms  an  investment  for  the 
vessels,    extending    downward    to   their   origin   from   the   ventricles,    and   is   thence 


?I6  HUMAN    ANATOMY. 

reflected  upward  over  the  anterior  surface  of  the  auricles  until  it  again  meets  the 
parietal  layer.  There  is  thus  produced,  between  the  aortse  in  front  and  the  auricles 
behind,  a  cavity  or  cleft,  known  as  the  transverse  sinus  of  the  pericardium  (Fig.  654), 
which  is  continuous  at  either  extremity  with  the  general  pericardial  cavity,  and  is 
roofed  in  by  the  parietal  layer,  while  its  walls  and  floor  are  formed  by  the  visceral 
layer. 

In  the  roof  of  the  sinus  transversus  a  slight  fold  is  to  be  found  towards  the  left,  which 
passes  backward  to  the  line  of  attachment  of  the  roof  to  the  left  auricle  and  thence  obliquely 
downward  in  the  visceral  layer  covering  the  posterior  surface  of  the  auricle  towards  the  coro- 
nary sinus.  This  duplicature,  known  as  the  vestigial  fold  of  the  pericardium  ( ligamentum  v. 
cavae  sinistrae),  contains  in  its  upper  part  a  fibrous  cord  and  in  its  lower  part  the  oblique  vein  of 
the  left  auricle  ;  these  two  structures,  the  vein  and  fibrous  cord,  together  with  the  coronary 
sinus,  representing  the  remains  of  an  original  left  superior  vena  cava. 

It  may  be  noted  that  the  line  of  attachment  of  the  parietal  layer  between  the  left  pul- 
monary veins  and  the  inferior  vena  cava  extends  high  up  on  the  posterior  surface  of  the  auricles, 
and  there  is  thus  formed  in  this  region  a  pouch-like  diverticulum  of  the  pericardium  whose 
mouth  looks  downward.  This  is  what  has  been  termed  the  oblique  sinus  of  the  pericardium. 
Its  parietal  wall  rests  upon  the  oesophagus  posteriorly,  and  in  case  of  extensive  effusion  into  the 
pericardial  cavity,  compression  of  the  oesophagus  sufficient  to  interfere  with  the  act  of  swallow- 
ing may  result. 

The  Ligaments  of  the  Pericardium. — The  parietal  layer  of  the  pericardium 
is  united  to  the  surrounding  structures  by  areolar  tissue  which  may  condense  to  definite 
bands  termed  pericardial  ligaments.  Thus  the  tissue  between  the  pericardium  and 
the  sternum  may  condense  to  form  a  superior  and  an  inferior pericardio-sternal  liga- 
ment, the  former  passing  to  the  posterior  surface  of  the  manubrium  sterni  and  the 
latter  to  the  lower  part  of  the  gladiolus.  Similarly,  bundles  of  fibres  are  attached  to 
the  apex  of  the  pericardial  cone  and  to  the  great  vessels  of  the  heart,  taking  their 
origin  from  the  prevertebral  layer  of  the  cervical  fascia  which  is  prolonged  downward 
into  the  thorax  ;  these  are  the  pericardio-vertebral  ligaments.  And,  finally,  a  band 
has  been  described  as  extending  from  the  posterior  surface  of  the  pericardium  to  the 
upper  surface  of  the  diaphragm  on  either  side  of  the  vena  cava  inferior  ;  these  form 
what  are  termed  the pericardio-plwenic  ligaments. 

The  Vessels. — The  arteries  which  supply  the  posterior  surface  of  the  parietal 
layer  of  the  pericardium  arise  from  the  thoracic  aorta,  and  those  of  the  anterior  sur- 
face are  given  off  by  the  internal  mammary  artery.  The  veins  of  the  parietal  layer 
pursue  courses  parallel  with  those  of  the  arteries,  and  open  into  the  vena  azygos 
behind  and  the  superior  phrenic  or  superior  vena  cava  anteriorly. 

The  lymphatics  pass  to  the  nodes  lying  in  the  bifurcation  of  the  trachea.  The  vas- 
cular supply  of  the  visceral  layer  is  the  same  as  that  of  the  muscular  tissue  of  the  heart. 

The  nerves  distributed  to  the  pericardium  include  fibres  from  the  phrenic  nerve, 
especially  the  left  one,  and  also  probably  from  the  cardiac  plexus. 

PRACTICAL  CONSIDERATIONS  :  THE  PERICARDIUM. 

The  visceral  layer  of  the  pericardium  is  closely  attached  to  and  practically  insep- 
arable from  the  heart  muscle.  It  is  continuous  with  the  parietal  layer  at  the  base  of 
the  heart  where  the  two  layers  ensheathe  the  great  vessels,  covering  in  especially 
the  first  inch  and  a  half  of  the  aorta  and  pulmonary  artery  and  leaving,  between 
those  vessels  in  front  and  the  auricles  behind,  an  open  space — the  transverse  sinus — 
which  may  be  the  seat  of  an  effusion  walled  off  by  adhesions  from  the  general  peri- 
cardial cavity.  The  least  resistant  important  structure  in  immediate  relation  to  this 
sinus  is  the  superior  vena  cava, — also  intrapericardial  at  its  lowermost  portion, — and 
such  effusion  might  therefore  cause  fulness  of  the  veins  of  the  neck  or  even  cyanosis 
without  the  evidence  of  a  general  pericardial  dropsy  large  enough  to  give  the  usual 
concomitant  physical  signs  {vide  infra').  In  artificial  distention  of  the  pericardium 
the  sac  tends  to  assume  the  shape  of  two  irregular  spheres,  the  upper  or  smaller  one 
containing  the  great  vessels  just  mentioned,  the  lower  embracing  the  heart,  the 
ascending  cava,  and  the, pulmonary  veins.  At  the  apex  of  the  heart,  where  the  peri- 
cardium is  reflected  from  the  diaphragm,  unimportant  sinuses,  analogous  to  the 
costo-phrenic  sinus  of  the  pleura,  may  exist. 


PRACTICAL  CONSIDERATIONS:    PERICARDIUM.  717 

The  parietal  layer  of  the  pericardium  is  in  relation  with  an  external  fibrous  layer 
which  extends  beyond  the  serous  investment  of  the  roots  of  the  great  vessels,  blends 
with  their  outer  coats,  and  is  directly  continuous  with  the  deep  cervical  fascia,  thus 
connecting  the  pericardium  with  two  respiratory  agents,  the  diaphragm  below  and 
the  cervical  muscles  (omohyoid)  above.  When  these  act  conjointly,  as  in  a  full 
inspiration,  they  render  the  pericardium  tense  and  resisting,  and  minimize  the  pressure 
upon  the  heart  by  the  inflated  lungs  (page  551). 

Pericarditis — probably  more  often  overlooked  than  any  other  serious  disease 
(Osier) — may  arise  from  wound  from  without,  as  in  ordinary  penetrating  wounds 
of  the  chest,  or  from  within,  as  from  the  passage  of  a  foreign  body  from  the  oesoph- 
agus into  the  pericardium  (page  1614);  or  it  may  follow  extension  of  disease  from 
contiguous  organs,  as  in  pleuro-pneumonia.  The  anatomical  relations  of  the  peri- 
cardium explain  these  occurrences.  The  more  usual  causes,  as  rheumatism,  septi- 
caemia, gout,  and  nephritis,  have  no  anatomical  bearing. 

Pericarditis  is  attended  by  certain  symptoms — well  detailed  by  Sibson — which 
should  be  studied  in  connection  with  the  anatomy  of  the  heart  and  pericardium. 

1.  Pain — (a)  spontaneous  and  directly  over  the  heart,  the  pleurae  often  being 
•involved,  both  these  serous  membranes — like  the  peritoneum — becoming  painful 
when  inflamed,  although  normally  insensitive  ;  (b)  elicited  by  pressure  (tenderness), 
the  skin  over  the  precordium  sometimes  participating  on  account  of  the  connection 
between  the  upper  intercostal  nerves  and  the  ganglia  and  nerves  of  the  cardiac  plexus  ; 
(c)  over  the  epigastric  region  and  increased  by  pressure,  because,  although  normally 
the  pericardium  below  is  in  direct  relation  with  the  thoracic  parietes  over  only  a  small 
area  behind  the  xiphoid  cartilage,  distention  of  the  pericardial  sac,  as  in  effusion 
from  pericarditis,  carries  it  downward  so  that  it  may  be  well  below  the  tip  of  the 
xiphoid  ;  (d  )  between  the  scapulae  or  deep  in  the  chest,  increased  by  swallowing  or 
by  eructations,  and  worse  when  the  patient  is  supine,  due  to  the  relation  between  the 
oesophagus  and  pericardium  just  below  the  aortic  arch  ;  (e)  in  the  side,  usually 
pleuritic  (from  extension),  and  more  common  on  the  left  side  on  account  of  the 
greater. extent  to  which  the  inflamed  pericardium  occupies  the  left  side  of  the  chest 
than  the  right  side,  to  the  marked  backward  displacement  of  the  lower  lobe  of  the 
left  lung  by  the  distended  pericardial  sac,  and  possibly  (Sibson)  to  the  pressure 
of  the  latter  on  the  left  bronchus  increasing  in  the  left  lung  the  tendency  to  intercur- 
rent pneumonia.  2.  Feeble  or  irregular  heart  action,  due  to  (a)  direct  extension 
of  the  inflammation  from  the  visceral  layer  of  the  pericardium  to  the  heart  muscle 
(myocarditis);  (b)  implication  of  the  cardiac  nerves  ;  (c)  pressure  by  the  pericardial 
effusion  on  the  vena?  cavae  and  pulmonary  veins,  impeding  the  blood-supply  to  both 
auricles  ;  direct  pressure  upon  the  auricles  interfering  with  the  ventricular  supply  ;  and 
pressure  upon  the  whole  organ  both  directly  from  the  effusion  and  indirectly  from 
the  compressed  and  displaced  lungs  and  the  other  contiguous  structures,  embarrass- 
ing its  action,  especially  in  diastole.  3.  Dyspnosa,  due  to  the  pulmonary  congestion 
produced  by  the  previous  causes  ;  sometimes  the  result  of  a  pleurisy  or  pleuro- 
pneumonia by  extension  ;  or  perhaps,  as  Hilton  has  suggested,  partly  from  fixation 
or  irregular  action  of  the  diaphragm  through  irritation  of  the  pericardiac  filament 
of  the  phrenic  (ramus  pericardiacus),  usually  given  off  on  the  right  side.  4.  Dys- 
phagia (page  1 6 14)  from  compression  of  the  oesophagus  between  the  pericardium 
and  the  vertebral  column,  usually  relieved  when  the  patient  is  put  in  an  approximately 
vertical  position.  5.  Aphonia,  from  involvement  of  the  left  recurrent  laryngeal 
nerve  by  contiguity,  or  of  both  nerves  through  their  cardiac  branches.  6.  Fulness 
of  the  cervical  veins  and  flushing  or  cyanosis  of  the  face,  due  to  pressure  upon  the 
thin  walls  of  the  right  auricle  and  of  the  superior  vena  cava.  Compression  of  the 
left  auricle  is  better  resisted  on  account  of  the  greater  thickness  of  its  walls  ;  when 
it  occurs,  it  tends  to  produce  pulmonary  congestion  or  apoplexy. 

The  physical  signs  of  pericarditis  are,  of  course,  influenced  by  the  attachment, 
surroundings,  and  physical  qualities  of  the  pericardium. 

1.  As  it  is  in  two  layers  normally  movable  upon  each  other,  the  roughening  caused 
by  inflammation  produces  a  friction-sound  which,  when  typical,  is  (a)  heard  best  over 
the  middle  and  the  lower  half  of  the  sternum,  and  over  the  adjoining  left  costal 
cartilages  or  their  interspaces,  because  there  a  greater  extent  of  the  pericardium  is 


718  HUMAN   ANATOMY. 

closer  to  the  ear,  with  fewer  intervening  structures  than  elsewhere  ;  {b)  preceded  or 
accompanied  by  pain  {vide  supra) ;  {c)  usually  increased  by  pressure  with  the  stetho- 
scope, which  brings  the  two  roughened  pericardial  layers  into  closer  apposition  ;  (d ) 
accompanied  by  an  extension  of  the  area  of  cardiac  dulness  {vide  infra);  (<?)  is 
double, — that  is,  corresponding,  although  not  altogether  synchronously,  to  both 
systole  and  diastole  ;  and  {/)  may  disappear  when  effusion  occurs, — separating  the 
two  layers, — or  may  persist  over  a  small  area  near  either  the  diaphragmatic  attach- 
ment or  the  pericardial  reflection  at  the  base. 

2.  As  the  pericardium  is  markedly  elastic,  when  effusion  takes  place  the  parietal 
layer  may  stretch  so  that  the  pericardial  cavity  may  hold  ten  or  twelve  ounces  instead 
of  a  few  grammes,  or  in  chronic  cases  may  contain  several  pints.  As  its  cavity  is  in  the 
shape  of  that  of  a  hollow  cone  or  pear,  the  apex  corresponding  to  the  fixed  portion  of 
the  heart — held  in  place  by  the  great  vessels — and  the  base — enlarged  to  permit  the 
considerable  degree  of  motion  of  the  heart's  apex — to  the  upper  surface  of  the  dia- 
phragm, pericardial  effusions  also  take  this  general  shape,  and  the  area  of  percussion- 
dulness  will  be  found  to  have  its  base — about  on  a  level  with  the  fifth  or  sixth 
interspace — inferior,  and  its  apex — about  on  a  level  with  the  second  interspace — 
directed  upward  towards  the  first  segment  of  the  sternum.  It  is  more  marked  to  the 
left  of  the  sternum  on  account  of  the  larger  area  of  heart  and  pericardium  on  that 
side,  but  may  be  found  to  the  right  of  the  sternum,  especially  about  the  fifth  intercostal 
space  (Rotch),  because  on  the  right  side  (owing  to  the  presence  of  the  right  lobe  of 
the  liver)  the  lower  border  of  the  distended  sac  is  somewhat  higher  than  on  the  left. 

3.  As  such  enlargement  must  affect  the  contiguous  organs  and  the  overlying 
parietes,  there  will  be  found  in  full  distention  :  {a)  prominence  of  the  intercostal 
spaces,  especially  on  the  left  side,  or  of  the  left  antero-lateral  thoracic  walls,  of  the 
epigastrium  (from  depression  of  the  diaphragm  and  left  lobe  of  the  liver),  of  the 
lower  two-thirds  of  the  sternum,  or,  in  children  with  yielding  thoracic  walls,  of  the 
whole  precordia  ;  {b)  compression  of  the  left  lung,  sometimes  causing  a  tympanitic 
percussion-note  in  the  left  axillary  region  ;  {c)  compression,  between  the  relatively 
unyielding  sternum  and  the  dorsal  spine,  of  the  trachea  and  left  bronchus  (irritative 
cough),  the  oesophagus  (dysphagia),  and  the  aorta  (affecting  the  systemic  blood- 
supply);  {d)  a  backward  curve  of  the  dorsal  spine  has  been  described  (Sibson)  as 
resulting  from  the  necessity  of  limiting  pressure  on  these  important  structures  ;  {e) 
compression  or  irritation  of  the  recurrent  laryngeal  nerve  (aphonia)  and  the  superior 
vena  cava  (venous  engorgement  of  neck  and  face)  have  been  noted  {vide  supra). 

4.  The  upward  displacement  of  the  heart  itself,  due  to  {a)  its  attachments  to 
the  great  vessels  fixing  its  upper  portion  ;  and  {b)  the  effect  of  gravity  upon  the 
effusion  which  distends  the  lower  part  of  the  sac,  separates  to  an  extent  the  chest- 
walls  and  the  inferior  portion  of  the  right  ventricle,  and  occupying  the  space  between 
the  lower  surface  of  the  heart  and  the  tendinous  centre  of  the  diaphragm,  forces  the 
former  organ  into  the  upper  part  of  the  pericardial  sac,  causes  a  corresponding 
alteration  in  the  cardiac  impulse,  which  is  diminished  or  obliterated,  and  a  change  z'« 
the  position  of  the  apex  beat,  which  may  be  found  at  the  third  or  fourth  interspace 
instead  of  at  the  fifth  ;  as  the  upper  portion  of  the  chest  is  the  narrower,  and  as  the 
left  lung  has  been  pushed  aside  by  the  distended  sac,  the  apex  beat  may  also  be 
found  much  nearer  a  vertical  line  drawn  through  the  nipple  than  is  normally  the  case. 

Either  paracentesis  pericardii  or  incision  of  the  pericardium  for  the  purpose  of 
tapping  or  of  draining  the  sac  in  cases  of  purulent  effusion  may  be  done  in  the  fifth 
or  sixth  intercostal  space  on  the  left  side  about  one  inch  from  the  sternum.  The 
internal  mammary  artery  descends  vertically  about  a  half  inch  from  the  margin  of 
the  sternum.  ■  The  pleura  is  often  pushed  by  the  distended  sac  beyond  the  point 
mentioned.  If  not,  the  trocar  would  penetrate  its  two  layers  if  inserted  one  inch  from 
the  sternal  border.  In  the  sixth  interspace  there  is  somewhat  less  danger  of  wound- 
ing the  heart.  Incision  close  to  the  edge  of  the  sternum  will  usually  avoid  both  of 
these  risks.  Incision  or  puncture  in  the  fifth  space  on  the  right  side  has  been  ad- 
vised as  minimizing  the  danger  to  the  heart.  Deguy  (quoted  by  Treves)  advises  sub- 
periosteal resection  of  the  xiphoid  cartilage  by  a  median  incision,  downward  detach- 
ment of  the  diaphragmatic  muscle-fibres,  and  dissection  through  the  loose  cellular 
tissue  to  the  pericardium,  which  is  seized,  drawn  down  and  forward,  and  incised. 


THE   ARTERIES.  719 


THE    GENERAL    PLAN    OF   THE   CIRCULATION. 

The  blood  which  enters  the  right  auricle  of  the  heart  by  way  of  the  superior  and 
inferior  venae  cavae  and  the  coronary  sinus  is  blood  which  has  come  from  the  tissues, 
to  which  it  has  delivered  the  oxygen  and  nutritive  material  and  from  which  it  has  re- 
ceived carbon  dioxide  and  other  waste  products.  From  the  right  auricle  this  blood 
passes  through  the  right  auriculo-ventricular  orifice  into  the  right  ventricle,  and  on 
the  contraction  of  this,  which  follows  immediately  upon  the  contraction  of  the  auricle, 
it  is  forced  into  the  pulmonary  aorta  (pulmonary  artery),  the  tricuspid  valve  pre- 
venting regurgitation  into  the  auricle.  Upon  the  completion  of  the  contraction  of  the 
ventricle,  the  blood  which  has  been  forced  into  the  pulmonary  aorta  and  is  distend- 
ing its  walls  forces  together  the  pulmonary  semilunar  valves  and,  consequently,  by  the 
contraction  of  the  walls  of  the  vessel  and  by  subsequent  contractions  of  the  ventricle, 
sending  new  blood  into  the  vessel,  is  forced  onward  towards  the  lungs.  In  the  sub- 
stance of  these  organs  the  pulmonary  vessels  divide  repeatedly,  and  finally  form  a 
dense  net-work  of  capillaries,  through  the  walls  of  which  an  interchange  of  gases  be- 
tween the  blood  and  the  air  contained  in  the  cavities  of  the  lungs  takes  place.  From 
the  pulmonary  capillaries  the  pulmonary  veins  arise  and  carry  the  purified  blood  back 
to  the  heart,  emptying  it  into  the  left  auricle. 

In  this  course  the  blood  has  passed  from  the  heart  through  a  set  of  capillaries 
back  to  the  heart,  and  in  one  sense  it  has  completed  a  circuit,  which  is  termed  the  mi?ior 
or  pulmonary  circulation.  In  reality,  however,  it  is  not  a  perfect  circuit,  since,  while 
beginning  in  the  right  side  of  the  heart,  it  terminates  in  the  left  side.  In  order  to 
reach  again  the  right  side,  it  is  necessary  for  it  to  pass  through  the  major  or  systemic 
circulation,  the  general  course  of  which  is  as  follows. 

From  the  left  auricle  the  blood  passes  through  the  left  auriculo-ventricular  orifice 
into  the  left  ventricle,  and  by  the  contraction  of  this  is  forced  into  the  systemic  aorta, 
or,  as  it  is  more  frequently  termed,  the  aorta,  the  bicuspid  valve  preventing  its  pas- 
sage back  into  the  auricle.  The  aorta  curves  backward  and  to  the  left  and  passes 
down  the  body  lying  upon  the  left  side  of  the  vertebral  column,  and  in  its  course 
gives  off  branches  which  distribute  the  blood  to  all  parts  of  the  body.  In  the  vari- 
ous organs  these  branches  break  up  into  a  net-work  of  capillaries,  from  which  veins 
lead  the  blood  into  either  the  superior  or  the  inferior  vena  cava  or  into  the  coronary 
sinus,  from  which  it  passes  to  the  right  auricle. 

In  the  systemic,  as  in  the  pulmonary  circulation,  the  blood  passes  from  the  heart, 
through  one  set  of  capillaries,  and  back  to  the  heart.  In  the  case  of  the  blood  which 
traverses  the  vessels  passing  to  the  stomach,  the  intestines  (with  the  exception  of 
the  lower  portion  of  the  rectum),  the  pancreas,  and  the  spleen,  however,  a  modifi- 
cation of  this  arrangement  occurs,  in  that  before  returning  to  the  heart  the  blood 
is  required  to  pass  through  two  sets  of  capillaries.  The  first  set  is  in  the  substance  of 
the  organs  named,  and  after  passing  through  this  the  blood  is  collected  into  a  vein, 
the  vena  porta,  which  conveys  it  to  the  liver.  Here  the  portal  vein  breaks  up  into 
the  second  set  of  capillaries,  through  which  the  blood  passes  to  the  hepatic  veins, 
which  open  into  the  vena  cava  inferior,  and  thus  return  the  blood  to  the  right 
auricle.    This  portion  of  the  major  circuit  forms  what  is  termed  the  portal  circulation. 

THE  ARTERIES. 

The  arteries  are  those  vessels  which  conduct  the  blood  away  from  the  heart. 
Since  the  blood  is  forced  into  the  arteries  under  considerable  pressure  by  the  con- 
traction of  the  ventricles,  it  is  necessary  that  the  walls  of  these  vessels  should  be  suffi- 
ciently strong  to  withstand  pressure,  and  at  the  same  time  elastic  so  as  to  yield  to 
each  successive  injection  of  blood  from  the  heart  and  to  return  to  the  normal  calibre 
when  the  wave  has  passed.  As  the  blood  courses  from  the  main  vessels  to  the  capil- 
laries, it  passes  through  channels  of  progressively  decreasing  calibre,  and  is,  there- 
fore, constantly  encountering  increased  resistance,  whereby  the  arterial  pressure  is 
diminished,  until  finally,  when  the  capillaries  are  reached,  the  pressure  is  practically 
nothing.      As  the  pressure  is  reduced,  the  thickness  of  the  arterial  walls  diminishes, 


72o  HUMAN   ANATOMY. 

so  that,  as  a  rule,  it  may  be  stated  that  the  thickness  of  the  wall  of  an  artery  is 
directly  proportional  to  the  calibre  of  the  vessel.  Exceptions  to  the  rule  exist,  how- 
ever, and  the  thickness  of  the  wall  is  not  necessarily  the  same  in  vessels  of  identical 
calibre. 

Another  general  rule,  to  which  there  are  also  exceptions,  is  to  the  effect  that  the 
calibre  of  an  artery  is  proportional  to  the  extent  of  territory  which  it  supplies.  At 
each  point  where  a  branch  is  given  off  from  an  artery  a  diminution  of  the  calibre 
occurs,  but  throughout  the  interval  between  successive  branches  the  size  of  the  vessel 
usually  remains  unchanged.  Where,  however,  a  marked  alteration  in  the  direction 
of  an  artery  occurs,  its  diameter  undergoes  a  slight  diminution,  but  is  re-established, 
or,  indeed,  increased  for  a  short  distance,  so  soon  as  the  change  of  direction  is 
accomplished.  These  constrictions,  which  are  especially  noticeable  in  large  arteries, 
such  as  the  aortic  arch  or  the  subclavian,  are  termed  arterial  isthmuses,  and  the 
enlargements  which  succeed  are  known  as  arterial  spindles. 

The  area  of  the  transverse  section  of  a  left  subclavian  artery  before  any  branches  were  given 
off  was  found  to  be  27.6  sq.  mm.,  that  of  a  section  of  the  isthmus  was  15.6  sq.  mm.,  while  that 
of  a  section  taken  about  2  cm.  beyond  the  isthmus  was  20  sq.  mm.  In  the  case  of  an  aorta  in 
which  the  spindle  was  well  marked,  the  area  of  a  transverse  section  of  the  isthmus  was  found  to 
be  46  sq.  mm.,  that  of  a  section  through  the  spindle  was  65  sq.  mm.,  and  that  of  a  section  of  the 
thoracic  aorta  a  little  below  the  spindle  was  again  46  sq.  mm.  (Stahel). 

THE  GENERAL  PLAN  OF  THE  ARTERIAL  SYSTEM. 

An  idea  of  the  general  plan  of  the  arterial  system  may  be  most  readily  obtained 
by  reference  to  the  arrangement  occurring  in  the  fishes  (Fig.  677),  in  which  respira- 
tion is  performed  by  gills  borne  upon  a  series  of  branchial  bars  which  form  the 
lateral  walls  of  the  pharynx.  In  these  forms  the  heart  consists  of  but  two  cham- 
bers, an  atrium  which  receives  the  great  veins  and  a  ventricle  from  which  a  single 
aortic  trunk,  the  truncus  arteriosus,  arises.  The  heart  contains  only  venous  blood, 
and  its  function  is  to  drive  the  blood  through  the  gills,  where  it  becomes  oxygen- 
ated, and  whence  it  passes  to  the  various  organs  of  the  body.  The  heart  is  situated 
far  forward,  beneath  the  posterior  portion  of  the  pharynx,  and  the  aorta  passes  forward 
from  it  along  the  floor  of  the  pharynx,  sometimes  dividing  early  into  two  parallel 
stems,  the  ventral  aortce.  From  these,  and  from  the  aorta  before  its  division, 
branches  pass  off  to  each  of  the  gill-arches  and,  breaking  up  into  capillaries,  traverse 
the  gill-filaments  borne  by  the  arches.  After  being  oxygenated  in  the  gill-filaments, 
the  blood  from  each  gill  is  collected  again  into  a  stem  which  joins  with  those  coming 
from  the  other  gills  of  the  same  side  of  the  body  to  form  a  longitudinal  trunk  situated 
on  the  roof  of  the  pharynx,  and  this  trunk,  passing  backward,  unites  with  its  fellow 
of  the  opposite  side  to  form  a  dorsal  aorta,  which  is  continued  throughout  the  entire 
length  of  the  body  immediately  beneath  the  vertebral  column. 

From  the  forward  part  of  each  of  the  dorsal  longitudinal  stems  branches  are 
continued  forward  into  the  head  region,  and  throughout  the  entire  trunk  region  the 
dorsal  aorta  gives  off  laterally  paired  branches  corresponding  to  each  of  the  seg- 
ments of  the  trunk,  and  from  its  ventral  surface  one  or  two  series  of  visceral  branches 
which  are  also  arranged  segmentally. 

At  one  stage  in  the  development  of  the  human  embryo  the  arrangement  of  the 
arterial  system  is  essentially  the  same  as  that  which  has  just  been  described,  except 
that,  since  there  are  no  longer  any  gill-filaments,  the  capillaries  of  the  branchial 
vessels  are  lacking.  By  a  series  of  important  changes,  later  to  be  described  (page 
846),  this  arrangement  is  converted  into  that  found  in  the  adult,  the  relation  between 
the  human  arrangement  and  that  occurring  in  the  fishes  being  shown  by  a  comparison 
of  the  preceding  diagram  with  Fig.  678.  It  will  be  seen  that  the  fourth  branchial 
arch  of  the  left  side  is  represented  by  the  arch  of  the  aorta,  the  anterior  portion 
of  the  dorsal  aorta  becomes  what  is  termed  the  internal  carotid  artery,  the  forward 
prolongation  of  the  ventral  aorta  becomes  the  external  carotid  artery,  and  the  con- 
necting link  between  these  two  vessels  represents  the  third  branchial  vessel.  And, 
finally,  the  last  pair  of  branchial  vessels  is  represented  by  the  pulmonary  arteries. 

While  the  arteries  have  their  primary  embryonic  arrangement,  the  heart  lies  far 
forward  beneath  the  posterior  portion  of  the  pharynx.      Later,  however,  it  undergoes 


GENERAL    PLAN    OF   THE   ARTERIAL   SYSTEM. 


721- 


a  regression  whereby  it  becomes  situated  in  the  thorax,  and  in  this  migration  it 
carries  backward  (downward)  with  it  the  pulmonary  arteries  and  the  arch  of  the 
aorta  and  produces  an  elongation  of  the  carotids.  As  a  result  of  the  regression  of 
the  aortic  arch,  the  lateral  branches  which  arose  from  the  anterior  portions  of  the 
dorsal  aorta  and  were  distributed  to  the  cervical  segments  of  the  body  become  sepa- 


Fig.  677. 

Dorsal  aortic  trunks 


Ventral  aortas  Third  aortic  (gill)  bow 


Diagram  showing  fundamental  arrangement  or  arteries  in  fish,  supposed  to  be  viewed 
from  the  side  and  above;  shaded  tube  represents  digestive  canal  with  its  gill-clefts  in  front 
surrounded  by  series  of  six  aortic  bows  and  behind  by  segmental  arteries. 

rated  from  their  origins  as  far  down  as  the  branch  to  the  seventh  cervical  segment, 
which  becomes  the  adult  subclavian  artery,  but  having  developed  anastomoses  with 
one  another,  so  that  a  longitudinal  stem,  running  parallel  with  the  internal  carotid 
and  attached  below  to  the  subclavian,  is  formed,  they  appear  in  the  adult  as  lateral 
branches  of  that  stem  which  is  termed  the  vertebral  artery.  Primarily  there  are  no 
longitudinal  arteries  in  the  body,  with  the  exception  of  the  carotids  and  the  dorsal 
aorta  ;  but  just  as  the  vertebral  artery  is  formed  in  the  neck  by  the  anastomosis  of 
upwardly  and  downwardly  directed  branches  from  lateral  vessels,  so,  too,  in  other 
regions,  such  as  the  thoracic  and  abdominal  walls,  other  longitudinal  stems  are 
secondarily  developed. 

The  dorsal  aorta  throughout  its  course  gives  off  with  almost  segmental  regular- 
ity lateral  branches  to  the  body-walls  which  form  the  intercostal  and  lumbar  arteries, 
the  fifth  lumbar  branches  becoming  greatly  enlarged  to  supply  the  lower  limb,  and 
being  termed  the  iliac  arteries.  Below  the  origin  of  these  the  aorta  is  represented 
only  by  a  comparatively  slender  vessel,  the  middle  sacral  artery,  which  is  continued 
to  the  tip  of  the  coccyx,  giving  off  lateral  branches  with  a  more  or  less  distinct  seg- 
mental arrangement.  The  visceral  branches  which  arise  from  the  aorta  do  not  retain 
their  original  segmental  arrangement  as  perfectly  as  do  the  branches  to  the  body- 
walls,  but  fuse  to  a  very  considerable  extent,  especially  in  the  abdomen,  to  form  a 
small  number  of  vessels  which  ramify  to  the  various  portions  of  the  digestive  tract 
and  to  the  genito-urinary  abdominal  organs. 


Left  subclavian 
Aorta 


Internal  carotids 


Pulmonary  artery 


External  carotids 


Ventral  aortae 

in  preceding  pla 


It  will  be  seen,  therefore,  that  the  arterial  system  consists  of  two  fundamental 
portions,  a  branchial  and  a  dorsal  aortic  portion.  A  classification  of  the  vessels  of 
the  adult  according  to  such  a  plan  would,  however,  result  in  considerable  confusion, 
since,  owing  to  the  secondary  modifications  which  have  occurred,  it  would  necessi- 
tate the  separation  into  different  groups  of  arteries  which  are  closely  related,  and, 

46 


722 


HUMAN    ANATOMY. 


conversely,  would  associate  quite  distinct  vessels.  It  will  be  more  convenient,  there- 
fore, to  employ  a  topographic  classification,  according  to  which  two  main  subdivi- 
sions of  the  system — that  of  the  pulmonary  aorta  and  that  of  the  systemic  aorta — may 
be  recognized,  the  systemic  subdivision  being  again  divided  into  the  aortic  arch,  the 
thoracic,  and  the  abdominal  portions. 

THE    PULMONARY    AORTA. 

The  pulmonary  aorta,  most  frequently  termed  the  pulmonary  artery  (a.  pul- 
monalis)  takes  its  origin  from  the  summit  of  the  conus  arteriosus  of  the  right 
ventricle.  It  is  from  4.5-5  cm.  (about  2  in.)  in  length,  and.  is  directed  upward, 
backward,  and  slightly  towards  the  left,  and  beneath  the  arch  of  the  aorta  it  divides 
into  the  right  and  left  pulmonary  arteries  (Fig.  679). 

Fig.  679. 


Ri^ht  innominate  v 


I-eft  pulmonary  artery 


Aorta,  s\ Memic 
Left 
Right  coronary  vessels 


Injected  heart  and  great  vessels,  viewed  from  before  ;  part  of  superior  vena  cava  and  aorta 
have  been  removed  to  show  right  pulmonary  artery. 

Relations. — Throughout  the  greater  portion  of  its  length  the  pulmonary  aorta 
is  invested  by  that  part  of  the  visceral  layer  of  the  pericardium  which  surrounds  it 
and  the  basal  portion  of  the  systemic  aorta.  At  its  origin  it  is  partly  overlapped  in 
front  by  the  tip  of  the  right  auricular  appendix,  and  posteriorly  it  is  in  relation  with 
the  base  of  the  systemic  aorta  and  the  proximal  portion  of  the  right  coronary  artery. 
More  distally  it  lies  to  the  left  of  the  systemic  aorta  and  rests  upon  the  anterior  sur- 
face of  the  left  auricle. 

Branches. — The  right  pulmonary  artery  (ramus  dexter)  has  an  almost  transverse  course 
from  its  origin  towards  the  base  of  the  right  lung.  It  passes  outward  above  the  right  auricle, 
behind  the  ascending  portion  of  the  systemic  aorta  and  the  superior  vena  cava  and  in  front  of 
the  right  bronchus.  At  the  root  of  the  lung  it  divides  into  three  branches  which  are  distributed 
to  the  three  lobes  of  the  lung. 

The  left  pulmonary  artery  (ramus  sinister")  is  somewhat  shorter  than  the  right,  and  passes 
outward  in  front  of  the  descending  portion  of  the  aortic  arch  and  the  left  bronchus  to  the  root 


THE    AORTIC    ARCH.  723 

of  the  left  lung,  where  it  divides  into  two  branches  to  be  distributed  to  the  lobes  of  the  lung. 
From  the  upper  border  of  the  artery  a  short  cylindrical  cord  passes  to  the  under  surface  of  the 
transverse  portion  of  the  aortic  arch,  a  little  beyond  the  point  at  which  the  left  subclavian  artery 
arises  from  its  upper  convex  surface.  This  cord  is  the  remains  of  a  communication  between 
the  pulmonary  and  systemic  aorta;  which  exists  in  fcetal  life,  when  the  lungs  are  not  functional, 
and  is  termed  the  ductus  arteriosus.  It  represents  the  outer  portion  of  the  vessel  of  the  sixth 
branchial  arch  of  the  left  side,  and  its  lumen  usually  becomes  occluded  during  the  first  few 
months  after  birth,  so  that,  as  a  rule,  the  cord  is  solid  in  the  adult. 

Variations. — The  majority  of  the  variations  that  have  been  observed  in  the  pulmonary 
aorta  are  associated  with  serious  malformations  of  the  heart  which  usually  result  in  early  death, 
and  are  consequently  to  be  classed  as  pathological  rather  than  as  merely  anomalous  conditions. 
A  precocious  division  of  the  main  stem  of  the  pulmonary  aorta  occasionally  occurs,  absence  of 
the  right  pulmonary  artery  has  been  observed,  and  an  accessory  coronary  artery  has  been  noted 
arising  from  the  pulmonary  aorta. 

Failure  of  the  ductus  arteriosus  to  undergo  complete  occlusion  is  a  not  infrequent  occur- 
rence, and  is  often  associated  with  a  persistence  of  the  foramen  ovale.  The  ductus  has  also 
been  observed  to  arise  directly  from  the  right  ventricle. 

THE    SYSTEMIC    AORTA. 

The  systemic  aorta,  or,  as  it  is  more  commonly  and  more  simply  termed,  the 
aorta,  is  the  main  arterial  stem  for  the  supply  of  the  tissues  of  the  body.  It  arises 
from  the  base  of  the  left  ventricle  and  curves  in  an  arch-like  manner  to  the  left  side  of 
the  vertebral  column,  along  which  it  runs  to  the  level  of  the  fourth  lumbar  vertebra. 
There  it  gives  off  a  pair  of  large  common  iliac  arteries,  and  is  continued  onward,  much 
reduced  in  size,  along  the  ventral  surface  of  the  sacrum  and  coccyx,  being  termed  in 
this  portion  of  its  course  the  middle  sacral  artery. 

It  may  be  regarded,  for  the  purpose  of  description,  as  being  composed  of  three 
portions  :  (1)  the  aortic  arch,  which  extends  from  the  heart  to  the  left  side  of  the 
body  of  the  fourth  thoracic  vertebra  ;  (2)  the  thoracic  aorta,  extending  from  the 
lower  end  of  the  aortic  arch  to  the  diaphragm  ;  and  (3)  the  abdominal  aorta,  extend- 
ing from  the  diaphragm  to  the  fourth  lumbar  vertebra.  The  middle  sacral  artery 
may  most  conveniently  be  treated  as  a  branch  of  the  abdominal  aorta. 

THE   AORTIC    ARCH. 

The  aortic  arch  arises  from  the  base  of  the  left  ventricle  (Figs.  679,  690),  and 
in  the  first  or  ascending  portion  (aorta  ascendens)  of  its  course  is  directed  upward  and 
somewhat  forward  and  to  the  right.  It  then  curves  to  the  left  and  backward  as  the 
transverse  poi-tion  (arcus  aortae),  and  finally  bends  downward  as  the  descending 
portion  along  the  left  side  of  the  body  of  the  fourth  thoracic  vertebra,  to  become 
continuous  with  the  thoracic  aorta. 

At  its  origin  the  aortic  arch  presents  three  rounded  swellings,  one  anterior  and  the 
other  two  postero-lateral,  marking  the  position  of  the  sinuses  of  Valsalva  (sinus  aortae). 
The  diameter  of  the  ascending  portion  is  about  2. 7  cm.  and  that  of  the  descending 
portion  about  2  cm. ,  the  diminution  appearing  rather  suddenly  below  the  origin  of 
the  left  subclavian  artery  and  forming  what  has  been  termed  the  aortic  isthmus. 
Where  the  ascending  portion  passes  over  into  the  transverse  an  enlargement  of  the 
diameter  occurs  which  is  especially  well  marked  in  older  individuals,  and  is  presuma- 
bly due  to  the  impact  of  the  blood  forced  out  of  the  ventricle  by  its  contractions. 

At  about  the  junction  of  its  transverse  and  descending  portions  the  arch  has 
attached  to  its  under  surface  the  fibrous  cord  which  represents  the  fcetal  ductus 
arteriosus. 

Relations. — The  ascending  portion  of  the  arch  is  enclosed  throughout 
almost  its  entire  length  (about  5  cm.,  or  2  in.  )  in  the  sheath,  formed  by  the  visceral 
layer  of  the  pericardium,  which  it  shares  with  the  pulmonary  aorta.  At  its  origin 
it  lies  behind  and  somewhat  to  the  left  of  that  vessel,  but  higher  up  crosses  it 
obliquely,  so  that  it  comes  to  lie  upon  its  right  side  ;  to  the  right  and  left  it  is  in 
relation  with  the  corresponding  auricles,  and  anteriorly  its  upper  portion  is  separ- 
ated from  contact  with  the  sternum  by  a  more  or  less  abundant  fatty  tissue  in  which 
are  the  remains  of  the  thymus  gland.  Posteriorly  it  is  in  relation  with  the  anterior 
surface  of  the  auricles. 


724 


HUMAN    ANATOMY. 


The  transverse  portion  is  crossed  on  its  anterior  surface  by  the  left  phrenic, 
cardiac,  and  pneumogastric  nerves,  arranged  in  that  order  from  right  to  left,  the 
pneumogastric  crossing  it  on  a  level  with  the  origin  of  the  left  subclavian  artery. 


Remains  of  thymus 
II.  costal  cartilage  \ 


680. 

/Stern  u 


Pericardial  sac 


Ascending  portion 

Bronchial  lvmph-nod 
Pleural 

Transverse  port 

Left  pneumogastric  ne 

Left  recurrent  laryngeal  n 

Descending  portion 


CEsophagus 
Thoracic  duct 


Bronchial  lymph-node 


Bifurcation  of  trachea 
Right  pneumogastric  nerve 


IV.  thoracic  vertebra 


j-section  of  body  at  level  of  fourth  thoracic  vertebra, 
upper  part  of  aortic  arch  has  been  removed. 


ved  from  above ; 


Fig.  6S1. 


Fig.  682. 


More  posteriorly  the  anterior  surface  is  in  contact  with  the  left  pleura.  Behind  it  is 
in  relation  from  right  to  left  with  the  superior  vena  cava,  the  trachea,  the  oesoph- 
agus, and  the  body  of  the  fourth  thoracic  vertebra,  and  below  it  are  the  right  pul- 
monary artery,  the  left  recurrent  laryngeal  nerve,  and  the  left  bronchus,  the  arch 
crossing  this  last  structure  obliquely  from  above  downward  and  outward. 

The  descending  portion  of  the   arch   has  in  front  of  it  a  portion  of  the  left 
pleura  and  the  root  of  the  left  lung.      Behind,  it  rests  upon  the  fourth  thoracic  ver- 
tebra; to  the  right  of  it  are  the 

oesophagus  and  the  thoracic  duct 

and  also  the  body  of  the  fourth 

thoracic  vertebra,  and  to  the  left 

are  the  left  pleura  and  lung. 

Branches. — Just  above  its 

origin   the  aortic  arch  gives  off 
.  (1)  the  right  and  left  coronary 

arteries,  and  from  the  upper  or 

convex  surface  of  the  transverse 

portion  there  arise  in  succession, 

from  right  to  left,  (2)  the  ijinom- 

inate  or  brachio-cephalic,  (3)  the 

left  common  carotid,  and  (4)  the 

left  subclavian  artery. 

Variations. — Owing  to  the  com- 
plexity of  the  changes  by  which  the 
primary  arrangement  of  the  branchial 
arch  vessels  is  transformed  into  the 
adult  arrangement  (Figs.  6S1,  682), 
and  owing  also  to  the  possibility  of 
some  of  the  normal  changes  remaining 
uncompleted,  the  variations  which  oc- 
cur in  connection  with  the  arch  of  the 
aorta  are  rather  numerous.  They  may 
be  conveniently  classed  in  five  groups. 
Group  I. — In  the  normal  development  (Fig.  6S2)  the  distal  portion  of  the  right  aortic  arch 
degenerates  as  far  up  as  the  right  subclavian  arterj',  indications  of  it  persisting  as  a  more  or 
less  rudimentary  vas  aberrans  arising  from  the  thoracic  aorta.      This  degeneration  may  not 
occur,  both  the  right  and  left  aortic  arches  persisting  in  their  entirety  (Fig.  683 ) ;  and,  since  in 


Diagram  showing  primary 
arrangement  of  longitudinal 
stems  and  series  of  six  aortic 
bows  ;  TA,  truncus  arteriosus  ; 
VA,  DA,  ventral  and  dorsal 
aortas;  A,  unpaired  dorsal 
aorta  ;  /-  VI,  aortic  bows,  of 
which  Kis  rudimentary. 


Diagrai 
derivations 
vessels  by 
ceding  plan 


vmg 


of  primary 
lodification  of  pre- 
j-3, aorta;  AA, aortic 
/,  innominate  artery ;  CC, 
ion  carotids;  EC.  IC,  exter- 
id  internal  carotids  ;  6",  sub- 
in  artery;  P,  pulmonary  art- 
DA,  ductus  arteriosus. 


THE   AORTIC    ARCH. 


725 


such  cases  the  descending  aorta  usually  retains  its  normal  position  to  the  left  of  the  spinal 
column,  a  condition  is  produced  in  which  the  aortic  arch  appears  to  be  split  lengthwise  into 
two  portions,  one  of  which,  the  left  arch,  passes  in  front  of  the  trachea  and  oesophagus  and 
gives  origin  to  the  left  common  carotid  and  the  left  subclavian  arteries,  while  the  other  passes 


Fig.  683. 


Fig.  6S4. 


Developmental  variations  of 
Group  I,  giving  rise  to  anomaly 
shown  in  next  figure.  PAA,LAA, 
right  and  left  aortic  arches ;  PS, 
LS.  subclavian  arteries;  A,  aorta; 
P,  pulmonary  artery. 


Pulmonary  artery 


Double  aortic  arch  through  which  trachea 
and  oesophagus  pass.     {Hommel). 


behind  the  structures  named  and  gives  origin  to  a  right  common  carotid  and  a  right  subclavian 
(Fig.  684). 

The  relative  diameters  of  the  two  portions  of  the  aortic  arch  so  formed  may  vary  con- 
siderably, that  passing  in  front  of  the  trachea  (the  true  left  arch)  being  sometimes  larger  and  at 
other  times  smaller  than  the  other  one.  In  the  latter  case  an  obliteration  of  the  distal  portion  of 
the  left  arch  may  occur,  and  the  left  common  carotid  and  left  subclavian  arteries  will  then 
appear  to  arise  close  to  the  innominate  stem,  from  a  common  trunk,  the  aortic  arch  passing 
to  the  left  behind  the  trachea. 

Group  II. — A  more  frequent  anomaly  is  the  complete  persistence  of  the  distal  portion  of 
the  right  aortic  arch  (Fig.  6S5)  associated  with  the  disappearance  of  a  greater  or  less  portion  of 


Fig.  6S5. 


Fig.  6S6. 


Right  common 
carotid 
Right 
vertebral 


Developmental  variations  of 
Group  II,  giving  rise  to  anomaly 
shown  in  next  figure.  A,  aorta; 
P.  pulmonary  artery  ;  PS.  LS.  right 
and  left  subclavian  arteries;  PV. 
right  vertebral  artery. 


,CEsophagus 

^  Left  c 

ammon  carotid 

-  Left  vertebral 

§1     J^SSu 

-Left 

subclavian 

-^Ci 

-Right 

subclavian 

1  of  right  subclavian  artery  from  descending  aorta. 


its  proximal  part,  the  result  being  the  apparent  origin  of  the  right  subclavian  artery  from  the 
descending  aorta,  whence  it  passes  to  the  right  behind  the  trachea  and  resophagus.  Variations  of 
this  condition,  depending  upon  the  location  and  extent  of  the  disappearing  portion  of  the  right 
arch,  may  modify  the  relations  of  the  right  vertebral  and  subclavian  arteries.     Thus,  in  some 


726 


HUMAN    ANATOMY. 


Fig.  687. 


cases  the  vertebral  may  arise  as  in  the  normal  arrangement  from  the  subclavian,  or  it  may,  as  it 
were,  exchange  positions  with  the  subclavian,  arising  from  the  descending  aorta,  while  the  sub- 
clavian arises,  in  common  with  the  right  common  carotid,  from  an  innominate  stem  ;  or  the 
vertebral  may  arise  with  the  right  common  carotid  from  the  innominate  stem,  the  subclavian 
alone  coming  from  the  descending  aorta  ( Fig.  6S6) . 

Group  III. — A  third  group  of  anomalies  depends  upon  the  complete  persistence  of  the 
right  aortic  arch,  associated  with  the  disappearance  of  the 
distal  portion  of  the  left  one  (Fig.  687).  In  such  cases  the 
result  is  a  complete  reversal  of  the  aortic  arch  and  its 
branches,  unaccompanied,  however,  by  a  reversal  of  any  of 
the  other  organs  of  the  body,  and  thus  differing  from  a 
true  situs  inversus  viscerum.  The  arch  is  directed'from  left 
to  right,  and  gives  rise  to  an  innominate  stem,  from  which 
the  left  common  carotid  and  left  subclavian  arteries  arise,  a 
right  common  carotid  and  a  right  subclavian,  the  descend- 
ing aorta  lying  upon  the  right  side  of  the  vertebral  column. 
Variations  of  these  anomalies  concern  principally  the  rela- 
tions of  the  ductus  arteriosus  or  the  cord  which  represents 
it.  It  may  unite  with  the  descending  aorta,  in  which  case 
it  is  the  persistent  right  sixth  branchial  vessel,  or  it  may  be 
formed,  as  usual,  from  the  left  sixth  branchial  vessel,  com- 
municating distally  with  the  left  subclavian,  this  artery,  in 
cases  where  the  ductus  remains  patent,  appearing  to  arise  by- 
two  roots,  one  from  the  innominate  stem  and  one  from  the 
pulmonary  aorta. 

Group  IV. — In  the  fourth  group  there  is  a  complete 
persistence  of  the  right  aortic  arch  associated  with  a  dis- 
appearance of  the  proximal  portion  of  the  left  arch  (Fig.  688), 
the  resulting  arrangement  being  the  reverse  of  that  seen 
in  cases  belonging  to  the  second  group.  The  left  sub- 
clavian artery  appears  to  arise  from  the  descending  aorta, 
which  lies  upon  the  right  side  of  the  vertebral  column,  and 
passes  to  the]  left  behind  the  trachea  and  oesophagus.  Varia- 
tions in  the  relations  of  the  ductus  arteriosus,  similar  to  those  mentioned  as  occurring  in  the 
third  group,  may  be  found. 

Group  V.— A  fifth  group  includes  those  cases  in  which 
the  arch  itself  is  normal,  but  in  which  there  are  variations  in  the 
vessels  that  arise  from  it.  These  variations  may  be  either  a 
diminution  or  an  increase  of  the  normal  number' of  vessels  or 
an  abnormal  arrangement  of  a  normal  number.  The  diminu- 
tion and  altered  arrangement  of  the  vessels  depend  upon  a 
shifting  of  more  or  fewer  of  them,  so  that,  for  example,  the  left 
common  carotid  and  left  subclavian  arteries  may  arise  from  a 
common  left  innominate  stem,  all  the  vessels  may  arise  from 
a  common  stem,  the  two  common  carotids  may  have  a  com- 
mon origin,  while  the  two  subclavians  arise  independently,  or, 
what  is  the  most  frequent  of  these  variations,  the  left  com- 
mon carotid  may  arise  from  the  innominate  stem  and  pass 
upward  and  to  the  left  obliquely  across  the  front  of  the 
trachea. 

An  increase  in  the  number  of  vessels  may  be  brought 
about  by  the  independent  origin  from  the  arch  of  both  the 
right  common  carotid  and  the  right  subclavian,  the  innominate 
being  absent.  In  other  cases,  vessels  which  normally  do  not 
come   into  relation  with  the  arch  may  take  origin  from  it,  this 

being  most  frequently  the  case  with  the  vertebral  arteries  and  Developmental  variations 

less  frequently  with  the  internal  mammaries  ;  and,  finallv,  an  of  Group  IV.  A,  aorta:  P, 
additonal  branch  to  the  thyroid  gland,  the  art.  thyroidea"  ima,  pulmonary  artery;  PS  LS, 
occasionally  takes  origin  from  the  arch.  "rferies  subclavan 


Developmental  variations 
of  Group  III.  A,  aorta;  P, 
pulmonary  artery;  RAA, 
right  aortic  arch;  DA,  duc- 
tus arteriosus  ;  PS,  LS,  right 
and  left  subclavian  arteries. 


Practical  Considerations. — The  Aortic  Arch  and  Thoracic  Aorta. — 
Surface  Relatio?is. — The  ascending  aorta  begins  beneath  the  sternum  just  to  the 
right  of  the  inner  end  of  the  third  left  costal  cartilage.  It  ascends  obliquely  and 
towards  the  upper  border  of  the  second  right  costal  cartilage.  The  second  (trans- 
verse) part  passes  backward  and  to  the  left,  crossing  the  mid-line  about  an  inch 
froin  the  suprasternal  notch,  the  lower  (concave)  border  corresponding  in  level  with 
the  ridge  between  the  manubrium  and  the  gladiolus,  the  upper  (convex)  border  to  the 
level  of  the  third  thoracic  spinous  process,  to  the  middle  of  the  manubrium,  and  the 
middle  of  the  first  costal  cartilage.  This  border  is  about  one  inch  below  the  supra- 
sternal notch.      The  surface  relations  of  this  portion  vary  with  the  development  of 


PRACTICAL    CONSIDERATIONS:    THE   AORTIC    ARCH.         727 

the  thorax.  In  persons  with  small  chests  the  upper  border  may  almost  reach  the 
level  of  the  top  of  the  manubrium,  while  in  those  with  large  chests  it  may  be  no 
higher  than  the  junction  of  the  first  and  second  pieces  of  the  sternum  {angulus 
Ludovici).  The  transverse  portion  reaches  the  left  side  of  the  vertebral  column  at 
a  level  just  above  the  fourth  thoracic  spine.  The  third  (descending)  portion  and 
the  thoracic  aorta  lie  at  first  a  little  to  the  left  of  the  body  of  the  fourth  thoracic 
vertebra  and  gradually  incline  to  the  mid-line,  passing  through  the  diaphragm  at  the 
level  of  the  twelfth  thoracic  vertebra. 

Aneurisms  of  the  aorta  are  more  frequent  than  are  those  of  any  other  vessel,  on 
account  of  the  great  strains  to  which  the  aorta  is  subject.  They  may  most  con- 
veniently be  considered  here  by  following  the  anatomical  subdivisions  of  the  vessel, 
premising,  however,  that  the  symptoms  thus  described  frequently  commingle  and 
overlap. 

A.  The  ascending  portion  is  more  subject  to  aneurism  than  are  the  remaining 
portions,  because  it  receives  the  first  and  most  vigorous  impulse  of  the  heart's  stroke, 
and  because  it  is  within — enclosed  by — the  pericardium,  and  its  walls  are  not  rein- 
forced by  blending  with  the  fibrous  pericardial  layer,  as  is  the  case  in  the  second 
and  third  portions.  Aneurism  most  frequently  involves  the  region  of  the  anterior 
sinus  of  Valsalva,  where  regurgitation  of  blood  chiefly  takes  place  ;  or,  if  higher,  the 
anterior  wall  of  the  aorta  in  the  vicinity  of  the  normal  dilatation,  probably  due  to  the 
impact  of  the  blood-current  leaving  the  heart.  The  symptoms  are  :  1.  Venous  con- 
gestion, causing  (a)  lividity  of  the  face  from  pressure  on  the  descending  cava,  the 
left  innominate,  and  the  internal  jugular  veins  ;  (£)  dizziness  and  headache  from  the 
same  cause  ;  {c)  swelling  and  oedema  of  the  right  arm  from  pressure  on  the  sub- 
clavian vein  ;  (d)  swelling  and  oedema  of  the  anterior  thoracic  wall  from  pressure  on  the 
internal  mammary,  azygos,  or  hemiazygos  veins.  2.  Dyspncea  with  altered  breath 
sounds  over  the  right  chest,  from  pressure  on  the  root  of  the  right  lung.  3.  Dys- 
phoria or  aphonia,  with  croupy  or  stridulous  respiration,  from  pressure  on  the  right 
recurrent  laryngeal  nerve  ;  sometimes  from  venous  congestion  due  to  pressure  on 
the  internal  jugular  and  innominate  acting  through  the  superior  thyroid  and  inferior 
thyroid  veins  on  the  corresponding  laryngeal  veins.  4.  Swelling  or  tumor,  often 
first  seen  at  or  about  the  sternal  end  of  the  third  right  intercostal  space.  5.  Dis- 
placement of  the  heart,  occasionally  occurring  when  the  aneurism  involves  especially 
the  concave  side  of  the  vessel  and  pushes  the  heart  downward  and  to  the  left.  6. 
Ascites  and  oedema  of  the  legs  and  feet  from  compression  of  the  ascending  cava  when 
the  aneurism  occupies  the  same  situation.  7.  Pain  in  the  sternum,  the  ribs,  or  the 
spine  from  direct  pressure  ;  encircling  the  upper  part  of  the  chest  from  pressure  on 
the  intercostal  nerves  ;  running  down  the  side  of  the  thorax  and  the  inner  surface  of 
the  arm  from  pressure  on  fibres  distributed  by  the  intercosto-humeral  nerve. 

B.  Aneurism  of  the  transverse  portion  may  cause  :  1.  Dyspnoea  and  dysphonia 
or  aphonia  from  direct  pressure  on  the  trachea  or  bronchi,  or  from  involvement  of 
the  left  recurrent  laryngeal  nerve  in  its  course  around  the  arch.  2.  Dilatation  of 
the  pupil  followed  by  contraction  from,  first,  irritation  and  then  paralysis  of  the 
sympathetic.  3.  Inanition  from  pressure  on  the  thoracic  duct.  4.  Swelling,  begin- 
ning in  the  mid-line,  then  extending  to  the  right  (only  four  left-sided  cases  out  of 
thirty-five  aneurisms,  Browne,  quoted  by  Osier),  and  sometimes  simulating  innomi- 
nate or  common  carotid  aneurism.  5.  Venous  congestion  of  the  head,  neck,  left  arm, 
etc. ,  often  more  marked  on  the  left  side  from  the  greater  exposure  to  pressure  of  the 
left  innominate  vein.  6.  Weakness  or  absence  of  radial  or  temporal  pulse — espe- 
cially on  the  left  side — due  to  pressure  on  or  involvement  of  the  innominate,  left  sub- 
clavian, or  left  carotid  artery. 

C.  Aneurism  of  the  descending  portion  of  the  arch  and  of  the  thoracic  aorta 
may  cause  :  1.  Dysphagia,  which  is  common  and  apt  to  appear  earlier  on  account 
of  the  more  direct  relation  with  the  oesophagus.  2.  Great  pain  in  the  spine,  some- 
times followed  by  paralysis,  from  erosion  of  the  vertebrae  and  compression  of  the 
cord.  3.  Swelling  in  the  left  scapular  region  or  at  the  vertebral  ends  of  the  middle 
ribs  on  the  left  side.  4.  Bronchiectasis,  with  cough  and  expectoration,  from  press- 
ure on  the  left  bronchus,  or  asthmatic  attacks  from  involvement  of  the  left  pulmo- 
nary plexus. 


728 


HUMAN  ANATOMY. 


THE  CORONARY  ARTERIES. 

The  coronary  arteries,  which  supply  the  heart,  are  two  in  number,  and  arise  from 
the  right  and  left  "prominences  at  the  base  of  the  aorta  which  mark  the  corresponding 
sinuses  of  Valsalva. 

The  left  coronary  artery  (a.  coronaria  sinistra)  lies  at  its  origin  (Fig.  679) 
behind  the  base  of  the  pulmonary  aorta,  and  passes  forward  between  that  vessel  and 
the  left  auricular  appendix  to  reach  the  anterior  interventricular  groove,  in  which  it 
divides  into  two  branches.  The  larger  of  these  (ramus  descendens  anterior)  descends 
in  the  groove  to  the  apex  of  the  heart,  giving  off  branches  which  supply  the  anterior 
surface  of  both  ventricles,  while  the  smaller  one  (ramus  circumflexus)  passes  backward 
in  the  left  portion  of  the  auriculo-ventricular  groove  and  gives  off  branches  to  the 
left  auricle  and  ventricle.  Branches  to  the  left  auricle  also  arise  from  the  main  stem 
of  the  artery,  as  well  as  twigs  to  the  walls  of  the  aortae. 


Fig.  6S9. 


Left  pulmonary  artery 


Superior  left  pulmonary  vein 

Inferior  left  pulmonary  vein 

Termination  of  left 
coronary  vein 
Transverse  branch  of  left 
coronary  artery 


Superior  right  pulmonary  * 
Right  pulmonary  artery 


Inferior  right  pulmonary 


Inferior  vena  cava 


Coronary  sinus 

Right  coronary  vein 
Transverse  branch  of  right 

coronary  artery 
Posterior  descending  branch 
of  right  coronary  artery 


Middle  cardiac  ' 


Right  ventricle 


Postero-inferior  surface  of  injected  heart. 


ed  from  below  and  behind. 


The  right  coronary  artery  (a.  coronaria  dextra)  passes  outward  from  its  origin 
in  the  right  portion  of  the  auriculo-ventricular  groove,  in  which  it  lies,  until  it  reaches 
the  posterior  interventricular  groove,  down  which  it  (ramus  descendens  posterior)  is 
continued  towards  the  apex  of  the  heart  (Fig.  689).  In  its  course  it  gives  off  num- 
erous branches,  which  are  distributed  to  the  right  auricle  and  ventricle  and  to  the 
portion  of  the  left  ventricle  which  adjoins  the  posterior  interventricular  groove. 
Usually  a  large  branch,  the  marginal  artery,  descends  along  the  right  border  of.  the 
heart  (Fig.  679)  and  gives  branches  to  both  surfaces  of  the  right  ventricle. 

The  peculiarities  of  the  ultimate  distribution  of  these  arteries  have  been  described 
in  connection  with  the  heart  (page  703). 

Variations. — The  two  coronary  arteries  may  arise  by  a  common  stem  ;  one  of  them  may 
be  wanting,  or  supernumerary  vessels  may  occur. 


THE    INNOMINATE   ARTERY.  729 


THE  INNOMINATE  ARTERY. 

The  innominate  artery  (a.  anonyma)  (Figs.  679,  690),  also  known  as'  the 
brachiocephalic,  is  the  first  as  well  as  the  largest  of  the  three  vessels  which  arise 
from  the  arch  of  the  aorta.  It  passes  directly  upward  to  the  level  of  the  right 
sterno-clavicular  articulation,  where  it  divides  into  the  right  common  carotid  and 
the  right  subclavian,  but  gives  rise  to  no  other  branches. 

Relations. — Anteriorly  it  is  separated  from  the  sternum  and  from  the  origins  of 
the  right  sterno-hyoid  and  sterno-thyroid  muscles  by  the  left  innominate  vein  and 
by  some  fatty  tissue  which  contains  the  remains  of  the  thymus  gland.  Posteriorly 
it  is  in  relation  with  the  trachea  and  the  sympathetic  cardiac  nerves  ;  on  the  right 
it  is  in  contact  with  the  right  pleura  and  on  the  left  of  it  is  the  left  common 
carotid  artery. 

Variations. — The  variations  of  the  innominate  artery  have  already  been  discussed  in 
connection  with  the  variations  of  the  aortic  arch,  since  the  vessel  represents  the  proximal 
portion  of  the  right  arch.  It  shows  considerable  variation  in  length,  measuring  between  2.8 
and  4.5  cm.,  although  occasionally  reaching  a  length  of  5  or  even  7  cm.  Occasionally  it  is 
absent,  the  right  common  carotid  and  the  right  subclavian  arteries  arising  directly  from  the 
aortic  arch. 

Although  the  innominate  artery  does  not,  as  a  rule,  give  origin  to  any  branches  except 
the  two  terminal  ones,  yet  in  about  10  per  cent,  of  cases  there  arises  from  it  a  vessel  which  is 
termed  the  arteria  thyroidea  ima.  This  takes  its  origin  usually  from  near  the  base  of  the 
innominate,  upon  its  medial  surface,  and  passes  directly  upward  upon  the  anterior  surface  of  the 
trachea  to  terminate  in  branches  which  are  distributed  to  the  isthmus  and  the  lower  portions  of 
the  lobes  of  the  thyroid  body.  The  presence  of  this  thyroidea  ima  is  frequently  associated  with 
a  more  or  less  extensive  reduction  of  the  size  of  one  or  other  of  the  inferior  thyroid  arteries,  and, 
indeed,  these  arteries  may  be  entirely  supplanted  by  it.  It  is  somewhat  variable  in  its  origin, 
for,  instead  of  arising  from  the  innominate,  it  may  be  given  off  by  the  aortic  arch,  by  the  right 
common  carotid,  by  either  the  right  or  left  subclavian,  or,  in  rare  cases,  by  one  of  the  branches 
of  the  subclavians. 

Practical  Considerations. — The  line  of  the  innominate  artery  is  from  the 
middle  of  the  manubrium  to  the  right  sterno-clavicular  joint.  Its  point  of  bifurca- 
tion would  be  crossed  by  a  line  drawn  backward,  just  above  the  clavicle,  through 
the  interval  between  the  sternal  and  clavicular  portions  of  the  sterno-mastoid  muscle. 

Aneurism  of  the  innominate  artery,  often  associated  with  aneurism  of  the  aortic 
arch,  causes  pressure-symptoms  easily  explained  by  the  chief  relations  of  the  vessel. 
They  may  be  summarized  as  follows  :  1.  Vascular,  (a)  arterial,  weakness  or  irregu- 
larity of  the  right  radical  pulse  or  of  the  right  carotid  or  temporal  pulse  from  inter- 
ruption of  the  direct  blood-current  ;  (d)  venous,  duskiness  of  the  face  and  neck, 
especially  of  the  right  side,  oedema  of  the  eyelids,  protrusion  of  the  eyeballs,  lividity 
of  the  lips,  from  pressure  on  the  left  innominate,  deep  jugular,  and  transverse 
veins  lying  between  the  vessel  and  the  thoracic  wall  ;  oedema  of  the  right  arm  from 
subclavian  pressure.  2.  Nervous,  cough  and  hoarseness  or  aphonia  from  involve- 
ment of  the  right  recurrent  laryngeal  :  dilatation  or  contraction  of  the  pupil  from 
pressure  on  the  sympathetic  ;  hiccough  from  irritation  of  the  phrenic  ;  pain,  particu- 
larly severe  on  the  right  side  of  the  neck  and  head,  the  same  side  of  the  chest,  and 
down  the  right  arm  from  pressure  on  the  branches  of  the  cervical  and  brachial 
plexuses.  In  addition,  dyspnoea  and  dysphagia  from  compression  of  the  trachea 
and  oesophagus,  and  the  appearance  of  a  swelling  at  and  above  the  right  sterno- 
clavicular articulation,  often  obliterating  the  suprasternal  depression,  are  character- 
istic symptoms. 

In  endeavoring  to  differentiate  these  aneurisms  from  those  of  the  arch  of  the 
aorta  it  may  be  well  to  remember  that  the  position  of  the  innominate  is  above,  to 
the  right,  and,  in  a  way,  cervico-thoracic,  while  that  of  the  arch  is  on  a  lower  level, 
is  median  or  to  the  left,  and  is  wholly  thoracic. 

Ligation.  — Two  skin  incisions,  each  three  inches  in  length,  are  made  along  the 
anterior  edge  of  the  sterno-mastoid  muscle  and  the  upper  border  of  the  inner  third 
of  the  clavicle,  uniting  at  an  acute  angle  near  the  right-sterno-clavicular  articulation. 
The  sternal  portion  and  the  greater  part  of  the  clavicular  portion  of  the  sterno-mas- 


73o  HUMAN    ANATOMY. 

toid  muscle  are  divided  just  above  their  origin.  The  anterior  jugular  vein  runs 
behind  the  sternal  head,  and  is  to  be  avoided  or  tied.  The  thyroid  plexus  of  veins 
may  appear  in  the  wound,  and  should  be  tied  or  drawn  out  of  the  way.  The 
sterno-hyoid  and  sterno-thyroid  muscles  are  divided  close  to  the  sternum.  The  deep 
cervical  fascia  is  divided  in  the  line  of  the  superficial  wound.  The  common  carotid 
artery  should  be  found,  its  sheath  opened,  and  the  vessel  traced  down  to  the  innomi- 
nate bifurcation.  The  internal  jugular  vein  may  be  much  engorged  and  should  be 
drawn  outward.  The  innominate  vein  may  protrude  into  the  wound.  Osteoplastic 
resection  of  the  manubrium  (Bardenheuer),  or  a  median  longitudinal  division  of  that 
bone  (Woolsey)  with  retraction  of  the  edges,  will  facilitate  the  exposure  of  the 
vessel.  The  most  important  relations  are  to  the  outer  side,— viz. ,  the  vagus,  the 
pleura,  and  the  right  innominate  vein.  The  left  common  carotid  and  trachea  lie  to 
the  inner  side.  The  needle  should  be  passed  from  without  inward.  The  ligature 
should  be  placed  as  high  as  possible,  to  leave  room  between  it  and  the  aorta  for  the 
formation  of  a  satisfactory  clot.  It  is  well  to  ligate  the  common  carotid  and  the 
vertebral  at  the  same  time,  to  lessen  the  risk  of  secondary  hemorrhage  on  the  distal 
side  of  the  ligature. 

The  collateral  circulation  is  carried  on  from  the  proximal  or  cardiac  side  of  the 
ligature  by  (a)  the  first  aortic  intercostal  ;  (6)  the  upper  aortic  intercostals  ;  (c)  the 
inferior  phrenic  branch  of  the  abdominal  aorta  (within  the  diaphragm);  (d)  the 
deep  epigastric  (within  the  rectus  sheath) ;  (e)  the  vertebrals  and  internal  carotids 
of  the  left  side  (within  the  cranium — circle  of  Willis)  ;  and  (_/)  the  branches  of  the 
left  external  carotid  ;  anastomosing  respectively  with  (a)  the  superior  intercostal  of 
the  subclavian  ;  (6)  the  intercostals  of  the  internal  mammary  and  the  thoracic 
branches  of  the  axillary  ;  (c)  the  musculo-phrenic  branch  of  the  internal  mammary  ; 
{d  )  the  superior  epigastric  branch  of  the  internal  mammary  ;  (<?)  the  vessels  in  the 
right  half  of  the  circle  of  Willis  ;  and  (_/)  the  branches  of  the  right  external  carotid, 
all  receiving  their  blood-supply  from  beyond — or  to  the  distal  side  of — the  ligature. 

THE   COMMON   CAROTID    ARTERIES. 

The  right  common  carotid  artery  arises  from  the  innominate  and  the  left  one  from 
the  arch  of  the  aorta  (Fig.  690).  Both  pass  directly  upward  in  the  neck,  along  the 
side  of  the  trachea  and  larynx,  and  terminate  opposite  the  upper  border  of  the  thyroid 
cartilage  by  dividing  into  the  external  and  internal  carotid  arteries,  their  course  being 
represented  by  a  line  drawn  from  a  point  midway  between  the  angle  of  the  jaw  and 
the  mastoid  process  to  the  sterno-clavicular  articulation.  Throughout  its  course 
neither  of  the  common  carotids  gives  off  any  branches,  and  they  consequently  have 
an  almost  uniform  calibre,  except  towards  their  point  of  division,  where  they  present 
a  dilatation  frequently  continued  into  the  internal  carotid  and  usually  becoming  more 
marked  with  advancing  age. 

Relations. — The  left  common  carotid  lies  in  the  thoracic  cavity  during  the 
first  part  of  its  course,  and  in  this  respect  differs  from  the  right  artery,  whose  origin 
from  the  brachio-cephalic  is  at  the  level  of  the  sterno-clavicular  articulation.  This 
thoracic  portion  of  the  left  common  carotid  is  usually  about  3  cm.  (1^  in.)  in 
length,  and  is  crossed  obliquely  in  front,  near  its  root,  by  the  left  innominate 
(brachio-cephalic)  vein  and  by  the  cardiac  branches  of  the  pneumogastric  nerve.  It 
is  separated  from  the  sternum  and  the  origin  of  the  sterno-thyroid  muscle  by  some 
fatty  tissue  which  contains  the  remains  of  the  thymus  gland,  and  posteriorly  it  is  in 
relation  with  the  trachea  below  and  higher  up  with  the  left  recurrent  laryngeal  nerve. 
Below,  to  its  right  side  and  a  short  distance  away,  is  the  innominate  artery  ;  above 
it  is  in  close  relation  with  the  trachea,  while  to  its  left  and  somewhat  posteriorly  are 
the  left  subclavian  artery  and  the  left  pneumogastric  nerve. 

Throughout  their  cervical  portions  the  relations  of  both  arteries  are  iden- 
tical. Each  is  enclosed  within  a  fibrous  sheath  formed  by  the  deep  cervical  fascia 
(page  550),  the  sheath  also  containing  the  internal  jugular  vein  and  the  pneumo- 
gastric nerve,  the  vein  lying  lateral  to  the  artery  and  the  nerve  between  the  two 
vessels,  but  in  a  plane  slightly  posterior  to  them.  Extending  downward  for  a  vari- 
able distance  upon  the  anterior  surface  of  the  sheath  is  the  descending  hypoglossal 


THE    COMMON    CAROTID    ARTERIES. 


73i 


nerve,  and  overlapping  it  to  a  certain  extent  is  the  stemo-cleido-mastoid  muscle 
and,  below,  the  sterno-hyoid  and  sterno-thyroid.  At  about  -the  level  of  the  cricoid 
cartilao-e  of  the  larynx  the  artery  is  crossed  obliquely  by  the  omo-hyoid  muscle,  and 
higher  up  by  the  middle  and  superior  thyroid,  the  lingual  and  sometimes  the  facial 
veins,  and  the  sterno-mastoid  branch  of  the  superior  thyroid  artery. 

Posteriorly  the  sheath  rests  upon  the  prevertebral  fascia  covering  the  longus  colli 
and  the  rectus  capitis  anticus  major  muscles,  and  is  in  relation  with  the  ganglionated 
cord  of  the  sympathetic  nervous  system  and  its  superior  and  middle  cardiac 
branches.      Lower  down,  opposite  the  sixth  cervical  vertebra,  the  branches  of  the 


Fig.  690. 


ertebral  arteries 
/  Inferior  thyroid  artery 


kiiOit  pel 


Right  pulmonary  artery 
Branch  of  right  bronchus 
Right  pul 
Rightauricular  appendage 


/ 


Dissection  showing  aortic  arch  and  its  branche 


:  been  pulled  aside 


inferior  thyroid  artery  pass  behind  it.  Medially  are  the  trachea  and  the  oesophagus, 
together  with  the  recurrent  laryngeal  nerve,  the  lobe  of  the  thyroid  gland,  and, 
above,  the  larynx  and  the  pharynx. 

Variations. — The  variations  of  the  common  carotid  arteries  have  been  sufficiently  discussed 
in  connection  with  the  anomalies  of  the  aortic  arch  (page  724). 

Practical  Considerations. — Aneurism  of  the  common  carotid  artery  is  not 
very  frequent.  It  most  commonly  occurs  near  the  bifurcation  (a)  because  of  the 
slight  dilatation  normally  existing  there  ;   (b~)  because  there  the  vessel  is  more  super- 


732  HUMAN   ANATOMY. 

ficial, — i.e.,  least  supported  by  overlying  muscle  ;  and  (c)  because  of  the  increased 
resistance  to  the  blood-current  at  that  point.  It  is  seen  oftener  in  the  right  carotid 
than  in  the  left.  Pressure-symptoms :  pain  in  the  side  of  the  neck,  face,  and  head 
in  the  distribution  of  the  superficial  cervical  plexus  of  nerves  ;  duskiness  or  mottling 
of  the  skin  from  pressure  on  the  sympathetic  ;  dyspncea  and  cough  from  lateral 
deflection  of  the  larynx  and  trachea  ;  defective  vision,  vertigo,  or  stupor  from  press- 
ure on  the  internal  jugular  ;  hoarseness  or  aphonia  from  implication  of  the  recurrent 
laryngeal  nerve  ;  dysphagia  from  direct  pressure  on  the  oesophagus,  or — possibly, 
together  with  irregular  heart  action,  vomiting,  or  asthmatic  respiration — from  press- 
ure on  the  pneumogastric. 

Digital  compression  may  be  used  in  a  case  of  stab  wound  or  in  the  treatment 
of  aneurism  (a)  by  making  pressure  backward  and  outward  beneath  the  anterior 
edge  of  the  sterno-mastoid  muscle  at  the  level  of  the  cricoid  cartilage,  so  as  to  flatten 
out  the  artery  against  the  transverse  process  of  the  sixth  cervical  vertebra  (carotid 
tubercle)  about  two  and  a  half  inches  above  the  clavicle.  As  the  vertebral  artery  at 
this  level  enters  its  canal  in  the  foramina  of  the  transverse  processes,  it  will  probably 
escape  pressure.  The  internal  jugular  vein  is  usually  displaced  laterally.  The 
common  carotid  artery  may  also  be  effectually  compressed  in  cases  of  wound  (3)  by 
grasping  the  anterior  edge  of  the  sterno-mastoid  and  the  artery  together  between 
the  thumb  and  fingers,  or  (<r)  by  placing  the  thumb  beneath  the  artery  and  the 
anterior  edge  of  the  muscle,  and  the  fingers  along  its  posterior  edge.  In  all  three  of 
these  methods  it  is  necessary  to  flex  the  head  and  turn  it  a  little  towards  the  affected 
side  so  as  fully  to  relax  the  sterno-mastoid. 

Ligation. — It  may  be  necessary  to  tie  the  common  carotid  in  cases  of  (a)  aneu- 
rism, including  certain  pulsating  tumors  of  the  orbit  or  scalp  or  within  the  cranium  ; 
(b)  hemorrhage  from  wound  of  the  neck,  or  from  pharyngeal  wound  or  ulceration  ; 
or  (c)  for  the  prevention  of  bleeding  during  some  operations.  Whenever  ligation 
of  the  external  carotid  satisfactorily  meets  the  indications,  it  is  better  to  tie  that 
vessel  (q.v.),  as  the  cerebral  circulation  is  not  thereby  interfered  with. 

The  lower  portions  of  the  common  carotids  on  both  sides  of  the  neck  are  deeply 
seated  ;  they  are  covered  by  three  planes  of  muscles  (the  sterno-mastoid,  sterno- 
hyoid, and  sterno-thyroid)  ;  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve 
run  behind  them  on  each  side,  and  on  the  left  side  the  internal  jugular  vein  usually 
passes  from  without  inward  in  front  of  the  artery,  which  is  also  in  close  relation  to 
the  thoracic  duct,  the  innominate  artery,  and  the  left  innominate  vein. 

Two  operations  for  ligation  of  the  common  carotid  may  be  described  :  I.  The 
place  of  election  for  the  application  of  a  ligature  is  just  above  the  omo-hyoid  muscle, 
where  the  artery  has  become  more  superficial  and  is  covered  only  by  the  skin,  the 
platysma,  the  fasciae,  and  the  anterior  edge  of  the  sterno-mastoid.  The  skin  incision 
— three  inches  in  length — is  made  in  the  line  of  the  vessel,  the  centre  being  placed 
opposite  the  anterior  arch  of  the  cricoid  cartilage.  It  divides  also  the  platysma. 
The  deep  fascia  is  divided,  and  the  anterior  edge  of  the  sterno-mastoid  is  exposed 
and  followed  downward  to  the  angle  between  it  and  the  upper  edge  of  the  omo- 
hyoid muscle.  The  former  muscle  is  then  drawn  outward,  the  latter  downward,  the 
descendens  hypoglossi  nerve  avoided,  the  sterno-mastoid  branch  of  the  superior 
thyroid  artery  and  the  superior — and  sometimes  the  middle — thyroid  vein  held  aside 
or  tied,  and  the  sheath  opened  over  the  carotid  compartment, — i.e.,  well  to  the 
inner  side, — so  as  to  avoid  injury  to  the  larger  internal  jugular  vein,  which  some- 
times— as  in  cases  of  embarrassed  respiration — bulges  over  the  artery  so  as  com- 
pletely to  obscure  it.  The  needle  should  be  passed  from  without  inward  to  avoid 
injury  to  the  vein,  care,  of  course,  being  taken  not  to  include  the  vagus. 

2.  Below  the  omo-hyoid  muscle  the  skin  incision — three  inches  in  length — still 
follows  the  anterior  border  of  the  sterno-mastoid,  beginning  now  a  little  below  the 
lower  border  of  the  cricoid  cartilage  and  ending  just  above  the  sterno- clavicular 
articulation.  A  second  incision  along  the  upper  border  of  the  clavicle  is  often  advis- 
able. The  sterno-mastoid  is  drawn  outward  and  the  outer  edge  of  the  sterno-hyoid 
muscle  exposed,  and  that  muscle,  with  the  sterno-thyroid,  drawn  downward  and. 
inward.  Frequently  the  sternal  portion  of  the  sterno-mastoid,  and  occasionally  the 
sterno-hyoid  and  sterno-thyroid  muscles  also,  will  require  division  if  the  ligature  has 


THE    EXTERNAL    CAROTID    ARTERY.  733 

to  be  placed  as  near  the  root  of  the  neck  as  possible.  The  internal  jugular  vein  — 
especially  on  the  left  side— the  inferior  thyroid  artery,  and  the  recurrent  laryngeal 
nerve  must  be  avoided.      The  needle  is  passed  from  without  inward. 

The  collateral  circulation  is  carried  on  from  the  proximal  or  cardiac  side  through 
(a)  the  branches  of  the  external  carotid  on  the  opposite  side,  (6)  the  inferior  thy- 
roid, (c)  the  profunda  cervicis  (from  the  superior  intercostal  and  thus  from  the  sub- 
clavian), (d)  the  internal  carotid  and  the  vessels  of  the  opposite  segment  of  the 
circle  of  Willis,  and  (<?)  the  vertebral,  by  anastomosing  respectively  with  (a)  the 
external  carotid  branches,  (6)  the  superior  thyroid,  (c)  the  princeps  cervicis  (from 
the  occipital),  and  (d  )  and  (<?)  the  vessels  of  the  circle  of  Willis  on  the  affected  side. 

THE  EXTERNAL  CAROTID  ARTERY. 

The  external  carotid  artery  (a  carotis  externa)  (Figs.  692,  693)  arises  from  the 
common  carotid  at  about  the  level  of  the  upper  border  of  the  thyroid  cartilage — a 
level  which  corresponds  to  the  body  of  the  fourth  cervical  vertebra.  Thence  it  is 
directed  upward  and  slightly  backward  towards  the  angle  of  the  jaw,  where  it  enters 
the  substance  of  the  parotid  gland  and  continues  upward  in  that  structure  to  just 
below  the  root  of  the  zygoma.  Here  it  gives  rise  to  a  large  branch,  the  internal 
maxillary,  and  is  then  continued  upward  over  the  root  of  the  zygoma  upon  the  side 
of  the  skull,  this  terminal  portion  of  it  being  termed  the  superficial  temporal  artery. 

Relations. —  In  the  first  portion  of  its  course  the  external  carotid  lies  in  the 
superior  carotid  triangle  (page  548),  and  is  there  crossed  by  the  hypoglossal  nerve 
and  the  facial  vein.  Higher  up  it  passes  beneath  the  posterior  belly  of  the  digastric 
and  the  stylo-hyoid  muscles  and  also  beneath  the  temporo-maxillary  vein,  and  enters 
the  substance  of  the  parotid  gland.  Posteriorly  it  is  separated  from  the  internal 
carotid  artery  by  the  stylo-glossus  and  stylo-pharyngeus  muscles  and  the  glosso- 
pharyngeal nerve  ;  the  internal  carotid  artery  lies  laterally  to  it  at  its  origin  ; 
internally  it  is  in  relation  with  the  inferior  and  middle  constrictors  of  the  pharynx 
and  the  superior  laryngeal  nerve. 

Branches. — From  the  anterior  surface  of  the  external  carotid  arise,  from 
below  upward,  (1)  the  superior  thyroid,  (2)  the  lingual,  (3)  the  facial,  and  (4) 
the  internal  maxillary  arteries.  Erom  its  posterior  surface,  in  the  same  order  of 
succession,  arise  (5)  the  ascending  pharyngeal,  (6)  the  sterno-mastoid,  (7)  the 
occipital,  (8)  the  posterior  auricular  arteries.  Finally,  (9)  the  superficial  temporal 
artery  is  to  be  regarded  as  a  branch  which  is  the  continuation  upward  of  the 
main  stem. 

Variations. — Occasionally  the  external  carotid  artery  is  absent,  its  branches  arising  from 
the  common  carotid,  which  is  continued  directly  into  the  internal  carotid.  The  number  of  its 
branches  may  be  reduced  by  certain  of  them,  the  lingual  and  facial,  for  instance,  arising  by  a 
common  stem,  or  they  may  be  increased  by  the  occurrence  of  various  accessory  branches  pass- 
ing to  regions  supplied  by  the  regular  ones. 

Practical  Considerations. — The  external  carotid  is  rarely  the  subject  of 
aneurism,  except  as  a  result  of  trauma.  The  tumor  is  situated  below  the  angle  of 
the  jaw.  Pressure  on  the  hypoglossal  and  glosso-pharyngeal  nerves  and  on  the 
internal  jugular  vein  causes  various  symptoms  which  are  not  usually  definitely  diag- 
nostic. In  one  case  there  was  unilateral  atrophy  of  the  tongue  (Heath)  probably 
from  involvement  of  the  hypoglossal.  If  the  aneurism  is  situated  near  the  origin  of 
the  vessel,  it  may  be  indistinguishable  from  aneurism  of  the  common  carotid  at  its 
usual  location,  just  below  the  bifurcation.  The  vessel  is  not  infrequently  tied  for 
wound  of  the  neck,  for  aneurism  of  one  of  its  branches,  and  occasionally  as  a  pre- 
liminary to  certain  operations,  as  excision  of  the  superior  maxilla  or  removal,  of  a 
malignant  tonsillar  or  parotid  tumor.  In  cases  of  stab  or  cut-throat  wound  it  is 
better,  when  possible,  to  find  and  tie  both  ends  of  the  bleeding  vessel,  as  the  free 
anastomosis  between  the  branches  of  the  two  external  carotids  renders  a  recurrence 
of  hemorrhage  probable  after  ligation  of  the  main  trunk. 

Ligation. — That  part  of  the  line  for  the  common  carotid  extending  from  the 
level  of  the  angle  of  the  lower  jaw  to  that  of  the  middle  of  the  thyroid  cartilage  is  the 


734  HUMAN   ANATOMY. 

line  for  the  skin  incision.  The  artery  is  usually  tied  below  the  digastric  muscle — 
i.e.,  in  the  superior  carotid  triangle  (page  548) — and  between  the  origins  of  the  supe- 
rior thyroid  and  the  lingual  arteries — because  that  is  the  longest  interval  without 
branches.  After  the  skin,  superficial  fascia,  platysma,  and  deep  fascia  have  been 
divided,  the  anterior  edge  of  the  sterno-mastoid  cleared  and  drawn  outward  at  the 
lower  portion  of  the  wound,  and  the  facial,  lingual,  or  superior  thyroid  veins — if  they 
present — drawn  aside  or  tied  and  cut,  the  posterior  belly  of  the  digastric  muscle 
above  should  be  identified.  Just  beneath  it  the  hypoglossal  nerve  crosses  the  artery, 
and  a  little  lower — about  the  middle  of  the  incision — the  tip  of  the  greater  cornu  of 
the  hyoid  bone  may  be  felt.  At  this  level — above  the  origin  of  the  superior  thyroid 
and  below  that  of  the  lingual — the  artery  lies  just  to  the  inner  side  of  the  internal 
carotid  (but  somewhat  superficial  to  it)  and  of  the  internal  jugular  vein,  and  has  the 
superior  laryngeal  nerve  in  close  relation  behind  it. 

The  internal  carotid  has  been  tied  at  this  level  by  mistake  for  the  external 
carotid.  To  avoid  this  it  should  be  remembered  that  the  external  carotid  (a)  is 
more  anterior  ;  ( b)  is  more  superficial  ;  (c)  is  usually  smaller,  especially  in  the 
young  ;  (d  )  gives  off  branches  ;  (e)  is  close  to  the  tip  of  the  hyoid  bone  ;  (_/")  is  in 
contact  with  the  hypoglossal  nerve  ;  and  (  g)  that  compression  of  the  isolated  vessel 
arrests  the  temporal  and  facial  pulses.  The  needle  is  passed  from  without  inward  to 
avoid  the  internal  jugular. 

The  ligature  has  been  applied  just  below  the  parotid  gland — i.e.,  above  the 
digastric  muscle.  The  incision  (on  the  same  line)  should  extend  from  the  lobe  of 
the  ear  to  the  hyoid  bone,  the  sterno-mastoid  should  be  drawn  outward,  the  poste- 
rior belly  of  the  digastric  and  the  stylo-hyoid  muscle  downward,  and  the  parotid 
upward  and  inward. 

The  collateral  circulation  is  carried  on  from  the  cardiac  side  through  (a)  the 
branches  of  the  opposite  external  carotid  ;  (b)  the  inferior  thyroid  on  the  affected 
side  ;  (c)  the  branches  of  the  ophthalmic  of  the  same  side  ;  and  (d )  the  profunda 
cervicis,  anastomosing  respectively  with  (a)  the  branches  of  the  ligated  external 
carotid  ;  (b)  the  superior  thyroid  ;  (c)  the  facial  (from  the  same  vessel — the  external 
carotid)  ;  and  (d )  the  princeps  cervicis. 

1.  The  Superior  Thyroid  Artery. — The  superior  thyroid  artery  (a.  ttay- 
roidea  superior)  (Fig.  692)  arises  from  the  anterior  surface  of  the  external  carotid,  a 
short  distance  above  its  origin,  and  is  at  first  directed  almost  horizontally  anteriorly, 
but  soon  turns  downward  and,  passing  over  the  superior  laryngeal  nerve  and  beneath 
the  omo-hyoid  and  thyro-hyoid  muscles,  breaks  up  into  a  number  of  branches  which 
enter  the  substance  of  the  thyroid  gland.  It  possesses  always  a  calibre  of  consider- 
able size,  but  varies  directly  according  to  the  size  of  the  gland,  and  inversely 
according  to  the  amount  of  blood  reaching  the  gland  from  other  sources.  It  anas- 
tomoses abundantly  with  its  fellow  of  the  opposite  side  and  with  the  inferior  thyroid 
branch  of  the  subclavian. 

Branches. — From  its  horizontal  portion  are  given  off — 

(a)  An  infrahyoid  branch  ( ramus  byoideus),  which  passes  along  the  lower  border  of  the 
hyoid  bone,  supplying  the  muscles  inserting  into  that  bone. 

(5)  A  sterno-mastoid  branch  (ramus  sternocleidomastoideus),  always  small  and  occasionally 
wanting,  which  passes  downward  and  backward  across  the  sheath  enclosing  the  common 
carotid  to  enter  the  substance  of  the  sterno-cleido-mastoid  muscle. 

(c)  A  superior  laryngeal  branch  (a  laryngea  superior),  which  passes  forward  and  downward 
beneath  the  thyro-hyoid  muscle  and,  piercing  the  thyro-hyoid  membrane  along  with  the  superior 
laryngeal  nerve,  is  distributed  to  the  intrinsic  muscles  and  mucous  membrane  of  the  larynx. 

From  its  descending  portion  it  gives  off — 

(d )  The  crico-thyroid  branch  (ramus  cricothyroideus),  usually  of  small  size,  which  passes 
horizontally  forward  over  the  crico-thyroid  membrane  and  anastomoses  with  its  fellow  of  the 
opposite  side,  giving  off  branches  which  perforate  the  membrane  and  are  distributed  to  the 
muscles  and  mucous  membrane  of  the  lower  part  of  the  larynx. 

Variations. — The  superior  thyroid  may  give  origin  to  both  the  ascending  pharyngeal  and 
the  ascending  palatine.  The  crico-thyroid  not  infrequently  arises  from  the  superior  laryngeal, 
and  may  appear  to  be  the  main  stem  of  that  artery,  and  the  superior  laryngeal  may  arise  directly 
from  the  external  carotid. 


THE    LINGUAL    ARTERY. 


735 


Practical  Considerations. — The  superior  thyroid  artery  or  one  of  its  branches 
is  frequently  divided  in  cut- throat  wounds.  The  sterno-mastoid  branch  may  have 
to  be  tied  in  the  operation  of  ligation  of  the  common  carotid  at  the  place  of  election 
and  the  crico-thyroid  branch  during-  the  performance  of  laryngotomy. 

Ligation. — The  skin  incision,  two  inches  in  length,  with  its  centre  opposite  the 
thyro-hyoid  space,  is  made  along  the  carotid  line.  After  the  superior  thyroid  veins 
have  been  dealt  with  and  the  external  carotid  has  been  recognized,  the  vessel  may 
most  easily  be  found  in  the  sulcus  between  the  upper  border  of  the  thyroid  cartilage 

Fig.  691. 


Posterior  branch  of  temporal 
Anterior  branch  of  temporal 


iverse  facial  artery 
Superficial  temporal  artery 
Great  occipital  nerve 


tal  artery 

Angular  artery 
Facial  vein 
Lateral  nasal  artery 


Internal  carotid  artery 

Branch  of  ascending  cervical 

External  carotid  artery 

Levator  anguli  scapula? 


Transverse 
Posterior  scapul; 


Subclavian  vein 
Superficial  dissection,  showing  arteries  of  neck,  face  and  scalp. 


and  the  great  vessels,  where  for  a  short  distance  it  is  superficial  and  runs  almost 
horizontally. 

The  needle  should  be  passed  from  above  downward  with  the  point  directed  some- 
what towards  the  mid-line.  The  close  proximity  posteriorly  of  the  superior  laryngeal 
nerve  should  be  remembered. 


2.  The  Lingual  Artery. — The  lingual  artery  fa.  lingualis)  (Fig.  692)  usually 
arise- from  the  anterior  surface  of  the  external  carotid,  between  the  origins  of  the 
superior  thyroid  and   the  facial,   although  it  is  sometimes   given  off  from  a  trunk 


736  .  HUMAN    ANATOMY. 

common  to  it  and  one  or  other  of  these  arteries,  especially  the  facial.  In  the  first  part 
of  its  course  it  passes  forward  and  slightly  upward  and  inward  towards  the  tip  of  the 
lesser  cornu  of  the  hyoid  bone,  and  is  crossed  by  the  posterior  belly  of  the  digastric 
and  the  stylo-hyoid  muscles  and  by  the  hypoglossal  nerve.  On  reaching  the  pos- 
terior border  of  the  hyo-glossus,  it  passes  beneath  that  muscle  and  is  continued 
almost  directly  forward  beneath  the  mucous  membrane  covering  the  under  surface  of 
the  tongue  and  between  the  genio-hyo-glossus  and  the  inferior  lingualis  muscles.  In 
this  terminal  portion  it  has  a  sinuous  course,  and  is  frequently  termed  the  ranine 
artery  ( a.  profunda  linguae) ;  it  gives  branches  to  the  adjacent  muscular  substance 
and  mucous  membrane  of  the  tongue,  and  near  its  termination  anastomoses  with  its 
fellow  of  the  opposite  side. 

Branches. — (a)  The  suprahyoid  branch  (ramus  hyoideus),  given  off  from  the  first  portion, 
passes  horizontally  forward  over  the  hyoid  bone,  sending  branches  to  the  muscles  which  are 
inserted  into  that  bone  from  below. 

(6)  The  dorsal  lingual  branch  (rami  dorsales  linguae),  from  the  second  portion,  arises 
under  cover  of  the  posterior  border  of  the  hyo-glossus  and,  passing  upward  medial  to  the  stylo- 
glossus, breaks  up  into  branches  which  are  distributed  to  the  mucous  membrane  of  the  dorsum 
of  the  tongue,  as  far  back  as  the  epiglottis,  and  also  to  the  tonsil.  Occasionally  a  branch  unites 
with  a  corresponding  one  from  the  artery  of  the  opposite  side,  immediately  in  front  of  the  fora- 
men cascum,  and  is  continued  forward  in  the  median  line,  immediately  beneath  the  mucous 
membrane  of  the  dorsum  of  the  tongue,  as  far  as  the  tip. 

(c)  The  sublingual  branch  (a.  sublingualis)  is  given  off  near  the  anterior  border  of  the  hyo- 
glossus  muscle  and  runs  forward  in  the  same  plane  as  the  ranine  artery,  but  on  a  lower  level, 
resting  upon  the  mylo-hyoid  muscle  and  lying  between  the  genio-hyoid  laterally  and  the  genio- 
hyo-glossus  medially.  It  is  accompanied  by  the  submaxillary  (Wharton's)  duct,  which  lies  upon 
its  medial  side,  and  it  terminates  in  the  sublingual  gland,  also  sending  branches  to  the  neighbor- 
ing muscles  and  to  the  alveolar  border  of  the  mandible. 

Anastomoses. — The  various  branches  of  the  lingual  artery  anastomose  exten- 
sively with  their  fellows  of  the  opposite  side.  The  anastomoses  of  the  two  aa.  dor- 
sales  linguae  take  place,  however,  only  through  exceedingly  fine  twigs,  so  that  the 
tongue  may  be  divided  longitudinally  in  the  median  line  without  any  great  loss  of 
blood,  except  towards  the  tip,  where  a  larger  anastomosis  of  the  ranine  arteries  occurs. 
In  addition  to  these  contra-lateral  anastomoses,  the  lingual  also  anastomoses  through 
its  suprahyoid  branch  with  the  infrahyoid  of  the  superior  thyroid  artery,  through 
its  sublingual  branch  with  the  submental  branch  of  the  facial,  and  through  the  a. 
dorsalis  lingua?  with  the  various  tonsillar  arteries. 

Variations. — The  lingual  artery  sometimes  arises  from  a  common  trunk  with  the  facial, 
and  it  has  been  observed  to  terminate  at  the  root  of  the  tongue,  being  replaced  in  the  rest  of  its 
course  by  branches  from  the  internal  maxillary  or  by  the  submental  branch  of  the  facial.  The 
sublingual  branches  are  not  infrequently  lacking,  being  replaced  by  branches  of  the  submental, 
and,  in  addition  to  its  normal  branches,  the  main  artery  may  give  rise  to  a  superior  laryngeal  and 
an  accessory  superior  thyroid  branch. 

Practical  Considerations. — The  lingual  artery  is  tied  most  frequently  as  a 
preliminary  to  excision  of  the  whole  or  part  of  the  tongue,  but  one  or  both  arteries 
may  be  ligated  to  stop  bleeding  following  wound  or  malignant  ulceration  of  that 
organ,  or  in  an  effort  to  arrest  growth  by  cutting  off  blood-supply,  as  in  cases  of 
cancer  of  the  tongue  or  of  macroglossia. 

Ligation. — The  artery  is  for  convenience  divided  into  three  portions,  the  first 
between  its  origin — about  opposite  the  greater  cornu  of  the  hyoid — and  the  posterior 
edge  of  the  hyo-glossus  muscle,  lying  upon  the  middle  constrictor  of  the  pharynx  ; 
the  second  beneath  the  hyo-glossus  muscle,  lying  upon  the  genio-glossus  ;  the  third, 
(ranine)  from  the  anterior  border  of  the  hyo-glossus  along  the  under  surface  of  the 
tongue  to  its  termination. 

The  place  of  election  is  in  the  second  part.  The  skin  incision,  two  inches  in 
length,  curved,  with  the  concavity  upward,  begins  a  half-inch  below  and  external  to 
the  mandibular  symphysis  and  ends  a  little  below  and  internal  to  the  point  where 
the  facial  artery  crosses  the  lower  edge  of  the  inferior  maxilla  ;  its  centre  \z  just 
above  the  greater  cornu  of  the  hyoid.      If  the  incision  is  carried  too  far  backward. 


THE    FACIAL   ARTERY.  737 

the  facial  vein  may  be  cut.  The  remainder  of  the  operation  may  be  described  as  if 
it  were  done  in  four  stages.  1.  That  portion  of  the  deep  fascia-  constituting  the 
anterior  layer  of  the  capsule  of  the  submaxillary  gland  is  divided  in  the  line  of  the 
incision,  the  lower  edge  of  the  gland  exposed,  and  the  gland  itself  cleared  and  ele- 
vated over  the  lower  jaw,  with  due  care  to  avoid  injury  to  the  facial  artery  which 
passes  through  its  substance  and  the  facial  vein  which  runs  upon  its  surface.  2. 
The  thin  posterior  leaf  of  the  capsule  of  the  gland  being  divided,  the  white,  shining 
aponeurotic  loop  attaching  the  digastric  tendon  to  the  greater' cornu  of  the  hyoid 
will  be  seen.  The  tendon  near  the  bone  or  the  digastric  aponeurosis  should  be  fixed 
by  a  blunt  hook  or  tenaculum  and  drawn  downward  and  towards  the  surface.  3. 
After  the  division  of  the  posterior  layer  of  the  capsule  of  the  submaxillary  gland,  the 
posterior  edge  of  the  mylo-hyoid  muscle,  the  fibres  running  upward  and  slightly 
backward,  can  be  recognized  at  the  anterior  angle  of  the  wound  and  should  be 
clearly  defined.  4.  The  hypoglossal  nerve  separates  from  the  artery  at  the  poste- 
rior border  of  the  hyo-glossus  muscle,  where  the  vessel  disappears  to  run  between 
that  muscle  and  the  middle  constrictor.  The  nerve,  accompanied  by  the  ranine 
vein,  runs  almost  horizontally  across  the  surface  of  the  hyo-glossus,  and  in  its  turn 
disappears  under  the  edge  of  the  mylo-hyoid  muscle.  It  will  have  been  brought 
into  view  when  the  submaxillary  gland  has  been  raised,  the  posterior  layer  of  its 
capsule  divided,  and  a  little  fatty  connective  tissue  picked  away.  In  the  irregular 
triangle  formed  by  the  nerve  above,  the  mylo-hyoid  anteriorly,  and  the  posterior 
belly  and  tendon  of  the  digastric  posteriorly,  the  lingual  artery  runs  beneath  the 
hyo-glossus  muscle  and  near  the  apex  of  the  triangle — i.  e. ,  near  the  hyoid  bone. 
The  nerve  and  vein,  which  are  on  a  slightly  higher  level — a  few  millimetres — 
having  been  raised  and  the  fibres  of  the  hyo-glossus  divided  parallel  with  the  hyoid 
and  just  above  it,  the  artery  will  be  brought  into  view. 

In  ligation  of  the  lingual  for  carcinoma  of  the  tongue,  the  state  of  the  salivary 
gland,  which  varies  in  size,  in  density,  and  in  the  closeness  of  its  attachments,  is  the 
main  element  of  uncertainty  (Treves). 

3.  The  Facial  Artery. — The  facial  artery  (a.  maxillaris  externa)  (Fig.  691) 
arises  usually  a  short  distance  above  the  lingual,  from  the  anterior  surface  of  the 
external  carotid.  It  passes  at  first  forward  and  slightly  upward,  lying  beneath  the 
posterior  belly  of  the  digastric  and  the  stylo-hyoid  muscles  and  the  hypoglossal  nerve, 
and  is  then  continued  almost  horizontally  forward  in  a  groove  in  the  submaxillary 
gland.  When  it  reaches  the  level  of  the  anterior  border  of  the  masseter  muscle,  it 
assumes  a  vertical  direction  and  passes  over  the  ramus  of  the  mandible,  and  is  then 
continued  in  a  sinuous  course  obliquely  across  the  face  towards  the  naso-labial  angle, 
resting  upon  the  buccinator  and  levator  anguli  oris  muscles,  and  being  crossed  by  the 
risorius  and  zygomatic  muscles  and  by  some  branches  of  the  facial  nerve.  Arrived  at 
the  naso-labial  angle,  it  again  takes  an  almost  vertical  course,  passing  upward  beneath 
(or  sometimes  over)  the  levator  labii  superioris  and  the  levator  labii  superioris  alseque 
nasi  towards  the  inner  angle  of  the  orbit,  where  it  terminates  by  anastomosing  with 
the  nasal  branch  of  the  ophthalmic  artery.  This  terminal  vertical  portion  of  the 
vessel  is  usually  termed  the  angular  artery  (a.  angularis). 

Branches.— The  branches  of  the  facial  artery  (  Figs.  691,  693)  may  be  arranged  in  two 
groups  according  to  their  origin  from  the  cervical  or  facial  portions  of  the  artery. 

From  the  cervical  portion  arise  :  {a)  The  ascending  palatine  branch  (a.  palatina  ascen- 
dens),  a  small  artery  which  passes  upward  between  the  stylo-glossus  and  stylo-pharyngeus  mus- 
cles, to  which  it  sends  branches,  and  then  comes  to  lie  upon  the  outer  surface  of  the  superior 
constrictor  of  the  pharynx.  It  terminates  by  sending  branches  to  the  soft  palate,  the  tonsil, 
and  the  Eustachian  tube. 

{b)  The  tonsillar  branch  (ramus  tonsillaris)  is  another  small  branch  which  passes  verti- 
cally upward.  It  arises  close  to  the  ascending  palatine  and,  passing  over  the  stylo-glossus 
muscle,  pierces  the  superior  constrictor  of  the  pharynx  to  be  distributed  to  the  tonsil. 

(c)  The  glandular  branches  (rami  glandularis),  two  or  three  in  number,  are  distributed  to 
the  submaxillary  gland. 

(rf)  The  submental  branch  (a.  submentalis)  arises  just  before  the  artery  bends  upward 
over  the  mandible,  and  continues  onward  in  the  horizontal  course  followed  by  the  facial, 

47 


738  HUMAN    ANATOMY. 

through  the  submaxillary  gland.  It  passes  forward  upon  the  mylohyoid  muscle,  close  to  its 
origin,  until  it  reaches  the  insertion  of  the  anterior  belly  of  the  digastric,  when  it  passes  upward 
upon  the  ramus  of  the  mandible  to  supply  the  depressor  labii  inferioris  and  to  anastomose  with 
the  mental  branches  of  the  inferior  dental  artery  and  with  the  inferior  labial  branches  of  the 
facial.  It  sends  branches  to  the  muscles  in  its  vicinity  and  also  to  the  integument,  and  branches 
perforate  the  mylo-hyoid  muscle  to  anastomose  with  the  sublingual  branches  of  the  lingual. 

From  the  facial  portion,  (e)  The  masseteric  branches  arise  from  the  posterior  surface  of 
the  artery — and  are  directed  upward  to  supply  the  masseter  muscle  and  to  anastomose  with 
branches  of  the  internal  maxillary  and  transverse  facial  arteries. 

(/)  The  inferior  labial  branch  (a.  labialis  inferior)  passes  forward  along  the  outer  surface 
of  the  horizontal  ramus  of  the  mandible,  supplying  the  depressor  anguli  oris,  the  depressor 
labii  inferioris,  and  the  integument,  and  anastomosing  with  the  mental  branches  of  the  inferior 
dental  and  submental  arteries. 

(g)  The  inferior  coronary  artery  passes  forward  in  the  substance  of  the  lower  lip  between 
the  mucous  membrane  and  orbicularis  oris,  supplying  the  latter,  and  terminates  by  anastomosing 
with  its  fellow  of  the  opposite  side. 

(A)  The  superior  coronary  artery  (a.  labialis  superior)  has  the  same  course  and  relations  in 
the  upper  lip  that  the  inferior  coronary  has  in  the  lower  one.  It  anastomoses  with  its  fellow  of 
the  opposite  side,  and  near  its  termination  usually  sends  a  small  branch  upward  to  the  septum 
of  the  nose,  the  a.  septi  narium. 

(i)  The  lateral  nasal  takes  its  origin  just  as  the  artery  reaches  the  naso-labial  angle  ;  it 
passes  forward  over  the  ala  of  the  nose,  supplying  its  muscles  and  integument. 

(j)  The  angular  artery  (a.  angularis)  is  the  terminal  portion  of  the  facial  artery  beyond 
the  naso-labial  angle.  It  passes  directly  upward  in  the  angle  between  the  nose  and  the  cheek, 
and  gives  branches  to  the  adjacent  muscles,  the  lachrymal  sac,  and  the  orbicularis  palpebrarum, 
anastomosing  with  the  nasal  branch  of  the  ophthalmic  artery  and  with  the  infra-orbital  branch 
of  the  internal  maxillary. 

Anastomoses. — The  facial  artery,  by  means  of  its  facial  branches  and  the  sub- 
mental arteries,  makes  abundant  anastomoses  with  its  fellow  of  the  opposite  side. 
In  addition,  it  is  connected  with  other  branches  of  the  external  carotid;  with  the 
dorsalis  lingua;  and  submental  branches  of  the  lingual  by  its  tonsillar  and  inferior 
labial  branches  respectively;  with  the  descending  palatine,  infra-orbital  branches,  and 
mental  branches  of  the  internal  maxillary  by  its  tonsillar,  angular,  and  inferior  labial 
branches;  and  with  the  transverse  facial  branch  of  the  superficial  temporal  by  its 
masseteric  branches.  Finally,  it  is  connected  with  the  ophthalmic  branch  of  the 
internal  carotid  by  the  angular  artery. 

Variations. — The  facial  artery  may  arise  by  a  trunk  common  to  it  and  the  lingual,  or  it 
may  arise  above  the  level  of  the  angle  of  the  jaw.  Quite  frequently  it  does  not  extend  upon  the 
face  beyond  the  angle  of  the  mouth,  being  replaced  in  the  upper  part  of  its  course  by  branches 
from  the  transverse  facial  or  internal  maxillary  artery. 

The  ascending  palatine  branch  frequently  arises  directly  from  the  external  carotid,  or  it 
may  take  its  origin  from  the  ascending  pharyngeal  or  from  the  occipital,  and  the  tonsillar  is 
frequently  a  branch  of  it.  The  submental  branch  may  be  greatly  reduced  in  size  or  even 
absent,  being  replaced  in  whole  or  in  part  by  the  sublingual,  these  two  arteries  being  inversely 
proportionate  to  each  other  so  fat  as  their  development  is  concerned. 

Practical  Considerations. — The  facial  artery  may  require  ligation  on  account 
of  division  of  one  of  its  branches,  as  the  coronary,  but  whenever  direct  ligation 
of  the  wounded  vessel  is  possible,  it  is  preferable  on  account  of  the  very  free 
anastomosis  between  the  branches  of  opposite  sides,  leading  usually,  after  ligation 
of  the  main  trunk,  to  recurrence  of  the  hemorrhage.  In  bleeding  after  tonsillotomy 
(page  1608),  either  the  tonsillar  branch  of  the  facial  or  the  main  vessel  (where  it  runs 
between  the  posterior  belly  of  the  digastric  and  the  stylo-glossus  muscles)  may  be 
involved  ;  but  as  the  blood  may  also  be  furnished  by  the  ascending  pharyngeal, 
ligation  of  the  external  carotid  itself  rather  than  of  the  facial  would  be  more  likely  to 
be  efficient. 

Ligation. — (a)  The  cervical  portion  of  the  vessel  may  be  reached  through  an 
incision  like  that  for  the  lingual,  placed  a  little  higher,  and  not  extending  so  far 
anteriorly.  When  the  submaxillary  gland  is  drawn  upward,  the  artery  will  be  drawn 
with  it  and  made  prominent.  This  portion  may  also  be  reached  near  its  origin  by 
uncovering  the   external   carotid  (q.v.*)   and   identifying  the  vessel  where   it  runs 


THE    INTERNAL    MAXILLARY    ARTERY. 


739 


between  the  posterior  belly  of  the  digastric  above  and  the  hypoglossal  nerve  below. 
(b)  The  facial  portion  is  easily  exposed  where  it  crosses  the  mandible  at  the  ante- 
rior border  of  the  masseter,  either  by  a  vertical  cut  parallel  with  that  muscle  and  the 
artery  or  by  a  horizontal  cut  crossing  the  vessel  and  placed  under  the  inferior  margin 
of  the  jaw  so  as  to  leave  the  scar  in  an  inconspicuous  position.  Beneath  the  skin 
and  the  superficial  fascia  the  platysma  and  deep  fascia  are  the  only  structures  that 
require  division.  The  vein  lies  in  the  groove  between  the  artery  and  the  edge  of  the 
masseter. 

4.   The   Internal   Maxillary  Artery. — The  internal  maxillary   (a.  maxillaris 
interna)  (Fig.  692)  is  a  large  branch  which  arises  from  the  anterior  surface  of  the 

Fig.  692. 


Small  meningeal  branch 
Middle  meningeal 


Deep  temporal  branches 


Inferior  dental  artery 

Buccal  branch 

Internal  pterygoid  muscle 


external  carotid,  opposite  the  neck  of  the  mandible.  It  passes  forward  with  a  flexuous 
course,  lying  at  first  between  the  neck  of  the  mandible  and  the  spleno-mandibular 
ligament,  and  then  passing  either  between  the  two  pterygoid  muscles,  in  which  case  it 
crosses  the  inferior  dental  and  lingual  nerves,  or  else  over  the  external  surface  of  the 
external  pterygoid,  between  that  muscle  and  the  temporal.  It  then  passes  between 
the  two  heads  of  the  external  pterygoid,  in  the  one  case  passing  from  below  upward 
and  in  the  other  from  without  inward,  and  enters  the  spheno-maxillary  fossa,  in 
which  it  is  directed  upward  and  inward  towards  the  spheno-palatine  foramen,  which 
it  traverses  under  the  name  of  the  spheno-palatine  artery. 

Branches. — For  convenience  in  description  it  is  customary  to  regard  the  internal  maxillary 
artery  as  consisting  of  three  portions.     Its  first,  or  mandibular  portion,  is  that  which  lies  inter- 


74o  HUMAN   ANATOMY. 

nal  to  the  neck  of  the  mandible  ;  the  second,  or  pterygoid  portion,  is  that  which  traverses  the 
pterygoid  fossa,  and  is  in  relation  with  the  pterygoid  muscles  ;  and  the  third,  or  spheno-maxil- 
lary portion,  extends  from  where  it  passes  between  the  two  heads  of  the  external  pterygoid  mus- 
cle to  its  entrance  into  the  spheno-palatine  foramen.  Of  the  sixteen  named  branches  arising  from 
the  internal  maxillary  artery,  five  arise  from  the  first  portion,  five  from  the  second,  and  six  from 
the  third. 

From  the  first  or  mandibular  portion  arise  (i)  the  deep  auricular,  (2)  the  tympanic,  (3) 
the  middle  meningeal,  (4)  the  small  meningeal,  and  (5)  the  inferior  dental  arteries. 

(a)  The  deep  auricular  (a.  auricularis  profunda)  is  a  small  branch  which  passes  behind  the 
temporo-mandibular  articulation,  to  which  it  sends  branches,  and  perforates  the  anterior  wall  of 
the  external  auditory  meatus  to  supply  the  skin  lining  that  passage  and  the  outer  surface  of  the 
tympanic  membrane. 

(b)  The  tympanic  (a.  tympanica  anterior),  also  a  small  branch,  passes  upward,  giving  off 
branches  to  the  temporo-mandibular  articulation,  and  enters  the  Glaserian  fissure.  Thence  it 
traverses  the  iter  chorda;  anterius  along  with  the  chorda  tympani,  and  reaches  the  middle  ear,  to 
whose  mucous  membrane  it  is  distributed,  anastomosing  with  the  tympanic  branches  of  the  stylo- 
mastoid artery. 

(c)  The  middle  meningeal  (a.  meningea  media)  is  the  largest  of  all  the  branches.  It  as- 
cends vertically  towards  the  base  of  the  skull  and  enters  the  cranium  by  the  foramen  spinosum, 
and,  after  passing  outward  and  upward  for  a  short  distance  upon  the  great  wing  of  the  sphenoid, 
divides  into  an  anterior  and  a  posterior  terminal  branch,  which  ramify  over  the  surface  of  the 
dura  and  supply  nearly  the  whole  of  its  lateral  and  superior  surfaces,  making  abundant  anasto- 
moses with  the  vessel  of  the  opposite  side.  The  anterior  branch,  the  larger  of  the  two  terminal 
branches,  passes  obliquely  forward  over  the  greater  wing  of  the  sphenoid,  crosses  the  anterior 
inferior  angle  of  the  parietal,  and  then  ascends  along  the  anterior  border  of  that  bone  almost  to 
the  superior  longitudinal  sinus,  sending  off  numerous  branches.  The  posterior  branch  passes 
backward  and  upward  over  the  squamous  portion  of  the  temporal  bone,  and  then  over  the  pos- 
terior part  of  the  parietal  bone,  giving  off  numerous  branches  which  pass  upward  as  far  as  the 
superior  longitudinal  sinus  and  backward  as  far  as  the  lateral  sinus.  In  addition  to  these  ter- 
minal branches,  the  main  stem  within  the  cranium  also  gives  origin  to  (aa)  a  petrosal  branch 
(a.  petrosus  superficialis)  which  enters  the  hiatus  Fallopii  and  anastomoses  with  the  terminal  por- 
tion of  the  stylo-mastoid  arteries  ;  to  (bb)  Gasserian  branches,  minute  twigs  which  pass  to  the 
Gasserian  ganglion  and  the  fifth  nerve  ;  to  (cc)  a  tympanic  branch  (a.  tympanica  superior)  which 
descends  through  the  petro-squamous  suture  to  the  mucous  membrane  of  the  middle  ear  and  the 
mastoid  cells  ;  and,  finally,  to  (dd  )  an  orbital  branch,  a  small  vessel  that  passes  into  the  orbit 
through  the  outermost  portion  of  the  sphenoidal  fissure  and  anastomoses  with  the  lachrymal 
branch  of  the  ophthalmic. 

(d)  The  small  meningeal  (r.  meningeus  accessorius)  is  an  inconstant  branch,  sometimes 
arising  from  the  middle  meningeal.  It  passes  upward  along  the  mandibular  division  of  the  fifth 
nerve,  and  enters  the  cranium  through  the  foramen  ovale  to  be  distributed  to  the  Gasserian 
ganglion  and  the  dura  mater  in  its  neighborhood. 

(e)  The  inferior  dental  (a.  alveolaris  inferior)  is  given  off  from  the  lower  surface  of  the  artery 
and  descends  along  with  the  inferior  dental  nerve  to  the  mandibular  foramen.  Before  reaching 
the  foramen  it  gives  off  (aa)  a  lingual  branch,  which  accompanies  the  lingual  nerve  to  the 
tongue,  and  (bb)  a  mylo-hyoid  branch  (ramus  mylohyoideus),  accompanying  the  mylo-hyoid 
nerve  to  the  muscle  of  that  name.  Entering  the  mandibular  foramen,  it  traverses  the  man- 
dibular canal,  giving  off  branches  to  the  roots  of  the  lower  teeth  as  it  passes  them,  and  finally 
emerges  at  the  mental  foramen  as  (cc)  the  mental  artery  (a.  mentalis),  supplying  the  neighboring 
muscles  and  integument  and  anastomosing  with  the  submental  and  inferior  labial  branches  of  the 
facial.  Just  before  issuing  from  the  mental  foramen  it  gives  off  (dd)  an  incisive  branch  which 
distributes  twigs  to  the  incisor  teeth. 

From  the  second,  or  pterygoid  portion,  arise  branches  distributed  chiefly  to  the  adjacent 
muscles;  they  are  (1)  the  masseteric,  (2)  the  deep  temporal,  (3  and  4)  the  internal  and  exter- 
nal pterygoid,  and  (5)  the  buccal,  artery. 

(/)  The  masseteric  branch  (a.  masseterica)  passes  with  the  corresponding  nerve  through 
the  sigmoid  notch  of  the  mandible  to  enter  the  deep  surface  of  the  masseter. 

(g)  The  deep  temporal  branches  are  two  in  number,  the  anterior  and  the  posterior.  The 
posterior  branch  (a.  temporalis  profunda  posterior)  arises  close  to  or  in  common  with  the  mas- 
seteric, while  the  anterior  owe  (a.  temporalis  profunda  anterior)  is  given  off  near  the  termination 
of  the  pterygoid  portion  of  the  artery.  They  both  pass  upward  between  the  temporal  muscle 
and  the  bone,  supplying  the  muscle  and  anastomosing  with  the  middle  temporal  branch  of  the 
temporal  artery. 

(h  and?)  The  internal  and  external  pterygoid  branches  (rami  pterygoidei)  are  short  and 
variable  in  number.     They  pass  directly  into  the  muscles  of  the  same  names. 


THE    INTERNAL    MAXILLARY    ARTERY. 


74i 


(J)  The  buccal  branch  (a.  buccinatoria)  passes  downward  and  forward  with  the  buccal 
nerve  along  the  anterior  border  of  the  tendon  of  the  temporal  muscle,  and  supplies  the  bucci- 
nator muscle  and  the  mucous  membrane  of  the  mouth. 

From  the  third  or  spheno-maxillary  portion  arise  (1)  the  alveolar,  (2)  the  infraorbital, 
(3)  the  descending  palatine,  (4)  the  Vidian,  (5)  the  pterygopalatine •,  and  (6)  the  spheno- 
palatine. 

{k)  The  alveolar  branch  (a.  alveolaris  superior  posterior)  descends  upon  the  tuberosity  of 
the  maxilla,  giving  off  branches  which  penetrate  small  foramina  in  that  bone  and  are  distributed 
to  the  molar  and  premolar  teeth  and  the  gums  of  the  upper  jaw  and  to  the  mucous  membrane 
lining  the  antrum  of  Highmore.  The  main  stem  terminates  upon  the  tuberosity  of  the  maxilla 
by  breaking  up  into  a  plexus  with  which  branches  from  the  buccal  artery  unite. 

Fig.  693. 


Anterior  temporal 
Posterior  temporal 

Middle  temporal 


Coronoid  process 
of  mandible  with 
insertion  of  tem- 
poral muscle 

Buccinator 

Superior  coro- 
nary artery 

Inferior  coro- 
nary artery 

Inferior  labial 
artery 

Mental  branch  of 
facial  emerging 
from  mental  for- 

Submental  artery 


Genio-hyoid 

muscle 
Lingual  artery 
Hyoglossus  mus- 
cle, cut 
Mvlo-hvoid   nms 

cleof  left  side 
Superior  laryn- 
geal artery 
Thyro-hyoid 
muscle 


Tra 

Great  meningeal 
Superficial  temporal 

Small  meningeal 

Tympanic 

Internal  maxillary 

Inferior  dental  artery 

Mylo-hyoid  artery 

Posterior  auricular 

Inferior  dental  nerve 

Sterno-mastoid  artery 

Occipital  artery 

Tonsillar  artery 

Ascending  palatine 

Hypoglossal  nerve 

Facial  artery 

Internal  carotid 

External  carotid 

Superior  thyroid 

Common  carotid 

Sterno-mastoid  artery 


External  carotid,  internal  it 
outer  table 


Lxillary  and  inferior  dental  arteries  ; 
sf  mandible  have  been  removed. 


ndyle  and 


(/)  The  infraorbital  artery  (a.  infraorbitalis)  frequently  arises  in  common  with  the  alveolar. 
It  passes  forward  and  upward  through  the  spheno-maxillary  fossa  and  the  spheno-maxillary 
foramen  to  traverse  the  infraorbital  groove  and  canal  along  with  the  infraorbital  nerve.  In  this 
part  of  its  course  it  gives  off  (act)  orbital  branches,  distributed  to  the  adipose  tissue  of  the  orbit 
and  to  the  neighboring  muscles  of  the  eye,  and  (bb)  anterior  dental  branches  (aa.  alveolares 
superiores  anteriores)  which  pass  down  the  anterior  wall  of  the  antrum  of  Highmore,  along  with 
the  anterior  and  middle  superior  dental  nerves,  to  supply  the  mucous  membrane  lining  the 
antrum  and  the  canine  and  incisor  teeth  of  the  upper  jaw.  The  main  stem  emerges  upon  the 
face  at  the  infraorbital  foramen  and  divides  into  (cc)  palpebral,  (dd)  nasal,  and  fee)  labial 
branches,  whose  distribution  is  indicated  by  their  names,  and  which  anastomose  with  the  nasal 
and  lachrymal  branches  of  the  ophthalmic  artery,  the  transverse  facial  branch  of  the  superficial 
temporal,  and  the  superior  coronary  and  angular  branches  of  the  facial. 

(m)  The  descending  palatine  artery  (a.  palatina  descendens)  accompanies  the  anterior  pala- 
tine nerve  from  the  spheno-palatine  ganglion  through  the  posterior  palatine  canal,  and,  on  its 


742  HUMAN   ANATOMY. 

emergence  from  the  posterior  palatine  foramen,  divides  into  an  anterior  and  a  posterior  branch. 
The  former  passes  forward  beneath  the  mucous  membrane  of  the  hard  palate,  which  it  supplies, 
and  at  the  anterior  palatine  foramen  anastomoses  with  the  spheno-palatine  artery  ;  the  latter 
passes  backward  to  supply  the  soft  palate  and  the  tonsil,  anastomosing  with  the  ascending 
palatine  branch  of  the  facial. 

(n)  The  Vidian  artery  (a.  canalis  pterygoidei )  is  a  small  branch  which  passes  backward  along 
the  Vidian  nerve  through  the  Vidian  canal,  and  sends  branches  to  the  roof  of  the  pharynx  and 
to  the  Eustachian  tube. 

(o)  The  pterygo-palatine  artery  (a.  palatina  major)  is  also  a  somewhat  slender  branch.  It 
passes  backward  through  the  pterygo-palatine  foramen  along  with  the  pharyngeal  nerve  from 
the  spheno-palatine  ganglion,  and  supplies  the  roof  of  the  pharynx,  the  Eustachian  tube,  and 
the  mucous  membrane  lining  the  sphenoidal  cells. 

(p)  The  spheno-palatine  artery  (a.  sphenopalatina)  is  the  terminal  branch  of  the  internal 
maxillary.  It  passes  into  the  nasal  cavity  through  the  spheno-palatine  foramen  along  with  the 
spheno-palatine  nerve  from  the  spheno-palatine  ganglion.  Shortly  after  traversing  the  foramen 
it  divides  into  an  internal  and  an  external  branch.  The  internal  branch,  sometimes  termed  the 
naso-palatine,  passes  transversely  across  the  roof  of  the  nasal  cavity  to  reach  the  septum,  upon 
which  it  passes  downward  and  forward,' giving  off  numerous  branches  which  anastomose  to  form 
a  rich  net-work  beneath  the  mucous  membrane  of  the  septum.  It  finally  reaches  the  anterior 
palatine  foramen,  where  it  anastomoses  with  the  anterior  branch  of  the  descending  palatine. 
Throughout  its  course  it  is  accompanied  by  the  naso-palatine  nerve.  The  external  branch 
ramifies  downward  and  forward  over  the  lateral  wall  of  the  nasal  fossa,  forming  a  rich  plexus 
beneath  the  mucous  membrane  lining  the  meatuses  and  the  turbinate  bones. 

It  will  be  observed  that  all  the  branches  arising  from  the  first  and  third  portions  of  the 
internal  maxillary  artery  traverse  bony  canals  or  foramina,  while  those  of  the  second  portion 
do  not,  but  are  distributed  directly  to  muscles. 

Anastomoses. — The  communications  of  the  internal  maxillary  artery  are  with 
the  branches  of  the  artery  of  the  opposite  side,  with  other  branches  of  the  artery  of  the 
same  side,  with  other  branches  of  the  external  carotid,  and  with  branches  of  the 
internal  carotid.  The  most  abundant  anastomoses  with  the  artery  of  the  opposite 
side  are  made  through  the  branches  of  the  middle  meningeal;  the  alveolar  branch 
anastomoses  with  the  dental  branches  of  the  infraorbital  of  the  same  side  and  with 
the  buccal  artery,  and  the  anterior  branch  of  the  descending  palatine  makes  a  large 
anastomosis  with  the  naso-palatine  branch  of  the  spheno-palatine  at  the  anterior 
palatine  foramen.  The  other  branches  of  the  external  carotid  with  which  anastomoses 
are  made  are  the  facial,  the  temporal,  and  the  posterior  auricular;  the  facial  com- 
municates by  means  of  its  submental  and  inferior  labial  branches  with  the  mental 
branch  of  the  inferior  dental,  by  its  superior  coronary  and  angular  branches  with  the 
terminal  branches  of  the  infraorbital,  by  its  superior  coronary  with  branches  of  the 
naso-palatine,  and  by  its  ascending  palatine  with  branches  of  the  descending  palatine. 
The  deep  temporal  arteries  anastomose  with  branches  of  the  superficial  temporal  and 
the  infraorbital  with  the  transverse  facial  branch  of  the  same  artery;  while  the 
posterior  auricular  communicates  by  means  of  its  stylo-mastoid  branch  with  the 
tympanic  branch  and  with  the  petrosal  branch  of  the  middle  meningeal. 

Of  the  anastomoses  with  the  internal  carotid  arteries  the  most  important  are 
those  between  the  orbital  branch  of  the  middle  meningeal  and  the  lachrymal  artery, 
between  the  terminal  branches  of  the  infraorbital  and  the  terminal  branches  of  the 
ophthalmic,  and  between  the  spheno-palatine  branches  and  the  ethmoidal  arteries. 

Variations. — In  the  early  stages  of  development  the  main  portion  of  the  internal  maxillary 
is  represented  by  a  stem  which  arises  from  the  internal  carotid  (Tandler).  This  is  known  as 
the  a.  stapedia  (Eig.  694,  Ast) ,  since  it  traverses  the  middle  ear,  passing  through  the  foramen 
of  the  stapes  (si);  it  makes  its  exit  from  the  middle  ear  by  the  Glaserian  fissure  and  divides  into 
two  stems,  one  of  which  (Rs)  passes  through  the  foramen  spinosum  (fsp)  and  is  distributed  to 
the  supraorbital  region,  while  the  other  divides  into  two  branches  which,  from  their  distribution, 
are  termed  the  infraorbital  (Ri)  and  the  mandibular  (inferior  dental)  (Rm).  A  branch  (Ras) 
arises  later  from  the  external  carotid  which  anastomoses  with  the  lower  stem  where  it  divides 
into  the  two  branches  just  mentioned,  and  the  main  stem  of  the  stapedius  disappears,  except 
in  its  distal  portion,  which  persists  as  the  tympanic  branch  of  the  internal  maxillary,  which  fre- 
quently arises  in  the  adult  from  the  middle  meningeal  instead  of  directly  from  the  internal  max- 
illary. By  these  changes,  as  may  be  seen  from  the  accompanying:  diagrams,  the  adult  internal 
maxillary  is  formed,  the  supraorbital  branch  becoming  the  middle  meningeal  (Mm)  and  the 
mandibular  branch  the  inferior  dental,  while  the  infraorbital  branch  (Ri)  becomes  the  main 
stem  of  the  artery  from  which  the  remaining  branches  gradually  develop. 


THE    OCCIPITAL    ARTERY. 


743 


In  correspondence  with  this  history,  a  persistence  of  the  stapedial  artery  is  occasionally 
found  ;  but  the  majority  of  the  usual  variations  of  the  internal  maxillary  are  due  to  the  second- 
ary anastomoses  which  its  branches  make  with  other  vessels.  Thus,  by  an  enlargement  of 
the  anastomoses  between  the  middle  meningeal  and  the  branches  of  the  ophthalmic  artery,  that 
vessel  or  some  of  its  branches,  notably 


the  lachrymal,  may  come  to  arise  from 
the  middle  meningeal  (page  749).  And, 
similarly,  by  the  anastomoses  with  the 
facial  or  transverse  facial  arteries,  the 
terminal  branches  of  the  infraorbital 
may  be  transferred  to  those  vessels,  the 
infraorbital  itself  stopping  in  the  middle 
of  the  infraorbital  groove. 

5.  The  Ascending  Pharyn- 
geal Artery.  — The  ascending 
pharyngeal  artery  (a.  pharyngea 
ascendens)  (Fig.  695)  differs  from 
all  the  other  branches  of  the  external 
carotid  by  its  vertical  course.  It 
is  a  comparatively  small  stem  which 
arises  close  to  or  immediately  at  the 
origin  of  the  external  carotid  and 
passes  upward,  at  first  between  that 
vessel  and  the  internal  carotid,  and 
later  between  the  internal  carotid 
and  the  internal  jugular  vein. 


Fig.  694. 


Diagrams  illustrating  development  of  internal  mi 
illary  artery;  A,  early  stage  ;  B,  later  stage;  C,  comm 
carotid;  O,  Ci,  external  and  internal  carotid.  For  < 
planation  of  other  letters,  see  text.     (  Tandler.) 


Branches. — (a)  A  prevertebral  branch  which  supplies  the  prevertebral  muscles  of  the  neck 
and  anastomoses  with  the  ascending  cervical  branch  of  the  inferior  thyroid  artery. 

(b)  Pharyngeal  branches  (rami  pharyngei),  two  or  three  in  number,  which  supply  the  con- 
strictor muscles  and  the  mucous  membrane  of  the  pharynx. 

(c)  Meningeal  Branches. — A  number  of  small  twigs,  into  which  the  artery  breaks  up  as  it 
approaches  the  base  of  the  skull,  pass  through  the  jugular  and  anterior  condyloid  foramina  to 
supply  the  dura  mater  of  the  posterior  fossa  of  the  skull,  and  through  the  cartilage  of  the  middle 
lacerated  foramen  to  supply  the  dura  of  the  middle  fossa. 

Variations. — The  ascending  pharyngeal  frequently  gives  origin  to  the  ascending  palatine 
and  more  rarely  to  the  superior  laryngeal  artery.  It  is  very  variable  in  its  origin,  not  infre- 
quently being  given  off  front  one  or  other  of  the  neighboring  branches  of  the  external  carotid. 

6.  The  Sterno- Mastoid  Artery. — The  sterno-mastoid  artery  (a.  sterno- 
cleidomastoidea)  arises  from  the  posterior  surface  of  the  external  carotid,  near  its  origin, 
and  passes  downward  and  backward  to  enter  the  sterno-cleido-mastoid  muscle  along 
with  the  spinal  accessory  nerve.  It  is  a  comparatively  small  vessel  and  is  not  infre- 
quently absent,  being  replaced  by  branches  passing  to  the  muscle  from  other  arteries. 
When  it  is  present,  the  hypoglossal  nerve  bends  around  to  it  to  pass  forward  to  the 
lingual  muscles. 

7.  The  Occipital  Artery. — The  occipital  artery  (a.  occipitalis)  (Figs.  691, 
692)  arises  from  the  posterior  surface  of  the  carotid,  opposite  or  a  little  below  the 
facial.  It  passes  upward  and  backward,  and  is  at  first  partly  covered  by  the  posterior 
belly  of  the  digastric  and  the  stylo-hyoid  muscles,  the  parotid  gland,  and  the  temporo- 
maxillary  vein.  It  crosses  in  succession,  from  before  backward,  the  hypoglossal 
nerve,  which,  when  the  sterno-mastoid  artery  is  wanting,  winds  around  it  to  pass  for- 
ward to  the  tongue,  the  pneumogastric  nerve,  the  internal  jugular  vein,  and  the  spinal 
accessory  nerve.  It  then  passes  more  deeply,  lying  in  a  groove  on  the  posterior  sur- 
face of  the  mastoid  process  and  beneath  the  origin  of  the  posterior  belly  of  the 
digastric,  the  sterno-cleido-mastoid,  and  the  splenius  capitis.  Emerging  from  beneath 
these  muscles,  it  reappears  in  the  upper  part  of  the  occipital  triangle,  and  then  ascends 
in  a  tortuous  course  over  the  back  of  the  skull,  sometimes  perforating  the  trapezius 
near  its  origin,  and  breaks  up  into  numerous  branches  which  anastomose  writh 
branches  from  the  artery  of  the  opposite  side  and  with  those  of  the  posterior  auricular 
and  superficial  temporal.      In  this  last  part  of  its  course  it  is  superficial,  lying  beneath 


744  HUMAN   ANATOMY. 

the  integument  upon  the  aponeurosis  of  the  occipito-frontalis.  The  artery  pierces 
the  deeper  structures,  accompanied  by  the  great  occipital  nerve,  a  short  distance 
lateral  to  and  a  little  below  the  external  occipital  protuberance. 

Branches.— In  addition  to  its  terminal  branches,  the  occipital  artery  gives  off  : 

(a)  A  superior  sterno-mastoid  branch  which  supplies  the  upper  part  of  the  sterno-cleido- 

mastoid. 

'(b)  Posterior  meningeal  branches,  one  or  more  slender  vessels  which  pass  upward  along 

the  internal  jugular  vein  and,  entering  the  skull  by  the  jugular  foramen,  are  supplied  to  the 

dura  mater  of  the  posterior  fossa. 

(c)  An  auricular  branch  (ramus  auricularis)  which  passes  upward  over  the  mastoid  process 
to  supply  the  pinna  of  the  ear. 

(d)  A  mastoid  branch  (ramus  mastoideus)  which  enters  the  skull  by  the  mastoid  foramen 
and  supplies  the  mucous  membrane  lining  the  mastoid  cells,  the  diploe,  and  the  dura  mater. 

(e)  An  arteria  princeps  cervicis  (ramus  descendens)  which  arises  from  the  artery,  just  as  it 
passes  out  from  beneath  the  splenius  and  descends  the  neck,  supplying  the  adjacent  muscles  and 
anastomosing  with  the  superficial  cervical  branch  of  the  transversalis  colli  and  with  the  pro- 
funda cervicis  from  the  superior  intercostal. 

(/)  Muscular  branches  (rami  musculares)  which  are  given  off  all  along  the  course  of  the 
artery  to  the  neighboring  muscles. 

Anastomoses. — The  occipital  artery  makes  comparatively  large  and  abundant 
anastomoses  in  the  scalp  with  the  stylo-mastoid  and  temporal  arteries,  and  also, 
by  means  of  its  art.  princeps  cervicis,  with  branches  of  the  transversalis  colli  and 
superior  profunda  arteries,  which  arise  from  the  subclavian.  These  latter  anastomoses 
are  of  considerable  importance  in  the  development  of  a  collateral  circulation  after 
ligation  of  either  the  common  carotid  or  the  subclavian  arteries. 

Variations. — The  occipital  artery  occasionally  passes  superficial  to  the  sterno-cleido-mas- 
toid  muscle  instead  of  beneath  it,  and  it  not  infrequently  gives  origin  to  the  ascending  pharyn- 
geal artery  or  to  the  stylo-mastoid. 

Practical  Considerations. — The  occipital  artery  is  rarely  formally  ligated. 
The  cervical  portion  may  be  reached  through  an  incision  along  the  anterior  border 
of  the  sterno-mastoid,  beginning  midway  between  the  ramus  of  the  mandible  and  the 
lobe  of  the  ear  and  extending  downward  two  and  a  half  inches.  The  deep  fascia  at 
the  upper  angle  of  the  wound  (parotid  fascia)  is  spared  on  account  of  the  risk  of 
salivary  fistula.  At  the  lower  angle  it  is  divided,  the  parotid  and  sterno-mastoid 
are  separated,  and  the  digastric  and  stylo-hyoid  muscles  recognized  and  drawn 
upward.  The  occipital  artery,  near  its  origin,  will  then  be  seen  crossing  the  internal 
carotid  artery  and  internal  jugular  vein  and  in  contact  with  the  curve  of  the  hypo- 
glossal nerve  where  it  turns  to  cross  the  neck.  The  artery  may  be  ligated  close 
behind  the  nerve,  the  needle  being  passed  from  without  inward  to  avoid  the  jugular 
vein.  The  occipital  portion  is  approached  through  an  almost  horizontal  incision  two 
inches  in  length,  beginning  at  the  tip  of  the  mastoid  apophysis  and  extending  back- 
ward and  a  little  upward.  The  outer  fibres  of  the  sterno-mastoid  and  its  aponeu- 
rotic expansion,  the  splenius,  and  often  the  complexus,  must  then  be  divided  and 
the  pulsation  of  the  artery  sought  for  in  the  space  between  the  mastoid  and  the 
transverse  process  of  the  atlas,  whence  the  vessel  may  be  traced  outward.  If  it  is 
isolated  near  to  the  mastoid,  great  care  must  be  taken  not  to  injure  the  important 
mastoid  venous  tributaries  of  the  occipital  vein  which  in  this  region  connect  it  with 
the  lateral  sinus. 

8.  The  Posterior  Auricular  Artery. — The  posterior  auricular  artery  (a. 
auricularis  posterior)  (Fig.  693)  arises  from  the  external  carotid  after  it  has  passed 
beneath  the  posterior  belly  of  the  digastric.  It  passes  upward  and  backward,  cov- 
ered at  first  by  the  parotid  gland,  which  it  supplies,  and  divides  in  the  angle  between 
the  pinna  and  the  mastoid  process  into  terminal  branches,  some  of  which  supply  the 
pinna,  while  others  anastomose  with  branches  from  the  occipital  and  superficial 
temporal. 


THE    SUPERFICIAL    TEMPORAL   ARTERY.  745 

Branches. — In  addition  to  branches  to  the  parotid  gland  and  to  neighboring  muscles,  it 
gives  rise  to  the  stylo-mastoid  artery  (a.  stylomastoidea).  This  vessel  enters  the  stylo-mastoid 
foramen  and  traverses  the  facial  canal  ( aqueduct  of  Fallopius )  as  far  as  the  point  at  which  the 
hiatus  Fallopii  passes  off  from  it.  During  its  course  through  the  canal  it  gives  off  branches  to 
the  mucous  membrane  lining  the  mastoid  cells,  to  the  stapedius  muscle,  and  to  the  mucous 
membrane  of  the  middle  ear,  those  twigs  which  pass  to  the  inner  surface  of  the  tympanic  mem- 
brane anastomosing  with  the  tympanic  branch  of  the  internal  maxillary.  Arrived  at  the  hiatus 
Fallopii,  the  artery  accompanies  the  great  superficial  petrosal  nerve  through  that  canal  and 
enters  the  cranium,  supplying  the  dura  mater  and  anastomosing  with  branches  of  the  middle 
meningeal  artery. 

Variations.— The  stylo-mastoid  artery  may  arise  from  the  occipital  or  its  place  may  be 
taken  by  the  petrosal  branch  of  the  middle  meningeal,  with  which  the  stylo-mastoid  normally 
anastomoses. 

9.  The  Superficial  Temporal  Artery. — The  superficial  temporal  artery- 
fa.  temporalis  superficialis)  (  Fig.  693)  is  the  continuation  of  the  external  carotid  after, 
it  has  given  off  the  internal  maxillary.  At  its  origin  it  is  embedded  in  the  substance 
of  the  parotid  gland,  and  is  directed  upward  over  the  root  of  the  zygoma  and  imme- 
diately in  front  of  the  pinna.  After  ascending  a  short  distance,  usually  about  2  cm. , 
upon  the  aponeurosis  covering  the  temporal  muscle,  it  divides  into  an  anterior  and  a 
posterior  branch,  which,  diverging  and  branching  repeatedly,  pass  upward  over  the 
temporal  and  occipito-frontal  aponeuroses  almost  to  the  vertex  of  the  skull,  anasto- 
mosing with  the  supra-orbital  branches  of  the  ophthalmic  branch  of  the  internal 
carotid,  with  the  posterior  auricular  and  occipital  branches  of  the  external  carotid, 
and  with  the  artery  of  the  opposite  side. 

Branches. — 

{a)  Parotid  branches  (rami  parotidei),  small  branches  to  the  parotid  gland. 

(6)  Articular  branches  to  the  temporo-mandibular  articulation. 

(c)  Muscular  branches  to  the  masseter  muscle. 

(d)  The  anterior  auricular  branches  ( rami  auriculares  anteriores)  supply  the  outer  surface 
of  the  pinna  and  the  outer  portion  of  the  external  auditory  meatus. 

(e)  The  transverse  facial  artery  (a.  transversa  faciei)  arises  just  below  the  main  stem  of  the 
artery,  crosses  the  zygoma,  and  is  directed  forward  parallel  with  the  zygoma  and  between  it 
and  the  parotid  duct.  It  gives  off  branches  to  neighboring  muscles  and  to  the  integument  of 
the  cheek,  and  anastomoses  with  the  masseteric  branches  of  the  facial  and  with  the  buccal, 
alveolar,  and  infra-orbital  branches  of  the  internal  maxillary. 

{/)  The  middle  deep  temporal  (a.  temporalis  media)  arises  just  above  the  zygoma,  and 
after  perforating  the  temporal  aponeurosis  and  muscle,  it  ascends  upon  the  surface  of  the  skull 
to  anastomose  with  the  deep  temporal  branches  of  the  internal  maxillary  artery. 

{g)  The  orbital  branch  (a.  zygomaticoorbitalis)  runs  forward  along  the  upper  border  of  the 
zygoma,  supplying  the  orbicularis  palpebrarum  and  also  sending  branches  into  the  cavity  of 
the  orbit. 

Anastomoses. — The  superficial  temporal  artery  makes  extensive  anastomoses 
in  the  scalp  with  its  fellow  of  the  opposite  side,  with  the  occipital  and  posterior  auricu- 
lar branches  of  the  external  carotid,  and  with  the  supra-orbital  branch  of  the  oph- 
thalmic. By  means  of  the  transverse  facial  it  makes  anastomoses  with  the  facial  and 
internal  maxillary  arteries. 

Variations. — The  principal  variations  of  the  superficial  temporal  are  its  division  into  the 
terminal  branches  below  the  level  of  the  zygomatic  arch  and  the  absence  of  its  posterior  ter- 
minal branch  ;  in  the  latter  case  the  area  of  distribution  of  the  posterior  branch  is  supplied  by 
the  posterior  auricular  or  the  occipital  artery. 

Practical  Considerations. — The  superficial  temporal  artery  may  require 
ligation  on  account  of  wound  of  the  vessel,  or  of  one  of  its  branches,  or  in  cases  of 
aneurism.  It  or  one  of  its  chief  subdivisions  used  frequently  to  be  selected  for  the 
now  rare  operation  of  arteriotomy.  The  vessel  never  becomes  very  superficial  imme- 
diately after  emerging  from  beneath  the  upper  part  of  the  parotid.  In  the  first  por- 
tion of  its  track  of  ascent  its  pulsations  are  difficult  to  perceive.  In  the  presence  of 
the  least  swelling  of  the  region  they  become  incapable  of  serving  as  a  guide  for  the 
incision  (Farabeuf). 


746 


HUMAN    ANATOMY. 


Ligation. — The  skin,  superficial  fascia,  and  some  fibres  of  the  attrahens  aurem 
muscle  are  divided  for  an  inch  on  a  vertical  line  between  the  tragus  and  the  condyle 
of  the  mandible,  a  little  nearer  the  latter.  The  artery  will  be  found  closely  bound  by 
connective-tissue  bands  to  the  temporal  aponeurosis. 

THE  INTERNAL  CAROTID  ARTERY. 

The  internal  carotid  (Figs.  693,  695)  is  the  second  terminal  branch  of  the  com- 
mon carotid,  from  which  it  arises  on  a  level  with  the  upper  border  of  the  thyroid 

Fig.  695. 


Deep  dissection,  showing  internal  carotid,  vertebral  and  superior  intercostal  arteries. 

cartilage.  In  the  first  or  cervical  portion  of  its  course  it  lies  upon  the  outer  side  of  the 
external  carotid,  but,  as  it  passes  upward,  it  comes  to  lie  behind  and  then  internal 
to  that  vessel,  from  which  it  is  separated  by  the  stylo-hyoid,  digastric,  and  stylo- 
pharyngeus  muscles.  It  passes  almost  vertically  up  the  neck  to  the  entrance  to  the 
carotid  canal,  resting  posteriorly  on  the  prevertebral  fascia  covering  the  rectus  capitis 


THE    INTERNAL    CAROTID    ARTERY.  747 

anticus  major,  and  having  upon  its  median  side  the  wall  of  the  pharynx  and  laterally 
the  internal  jugular  vein,  between  which  and  the  artery,  and  on  a  plane  slightly  pos- 
terior to  both,  is  the  pneumogastric  nerve.  It  is  also  in  relation  in  the  upper  part 
of  this  cervical  portion  of  its  course  with  the  glosso-pharyngeal  nerve,  which  lies  at 
first  behind  it,  but  crosses  its  external  surface  lower  down  as  it  bends  forward  towards 
the  tongue,  and  with  the  superior  sympathetic  ganglion,  whose  cardiac  branch 
descends  along  its  internal  surface,  while  the  pharyngeal  branches  cross  it  and 
the  carotid  branch  ascends  with  the  artery  to  the  carotid  canal,  in  which  it  breaks 
up  to  form  the  carotid  plexus. 

In  the  second  or  petrosal  portion  of  its  course  the  internal  carotid  traverses  the 
carotid  canal,  to  whose  direction  it  conforms,  passing  at  first  vertically  upward  and 
then  bending  so  as  to  run  forward  and  inward  to  enter  the  cranial  cavity  at  the 
foramen  lacerum  medium. 

It  then  enters  upon  the  third  or  intracranial  portion  of  its  course,  ascending  at 
first  towards  the  posterior  clinoid  process,  but  soon  bending  forward  and  entering  the 
outer  wall  of  the  cavernous  sinus.  In  this  it  passes  forward,  accompanied  by  the 
sixth  nerve  (abducens),  and  at  the  level  of  the  anterior  clinoid  process  bends  upward, 
pierces  the  dura  mater,  and  quickly  divides  into  its  terminal  branches. 

Branches. — Throughout  its  cervical  portion  the  internal  carotid  normally  gives 
off  no  branches;  in  its  petrosal  portion,  in  addition  to  some  small  twigs  to  the  peri- 
osteum lining  the  carotid  canal,  it  gives  Origin  to  (1)  a  tympanic  branch.  In  its 
intracranial  portion,  in  addition  to  small  branches  to  the  walls  of  the  cavernous  sinus 
and  the  related  cranial  nerves,  to  the  Gasserian  ganglion,  and  to  the  pituitary  body, 
there  arise  (2)  anterior  meningeal  branches,  (3)  the  ophthalmic,  (4) posterior  commu- 
nicating', (5)  anterior  choroid  arteries.  And,  finally,  its  terminal  branches,  (6)  the 
middle  and  (7)  the  anterior  cerebral  arteries. 

Variations. — In  its  cervical  portion  the  internal  carotid  occasionally  takes  a  somewhat 
sinuous  course,  and,  especially  in  its  upper  part,  may  be  thrown  into  a  pronounced  horseshoe- 
shaped  curve.  It  may  give  rise  to  branches  which  normally  spring  from  the  external  carotid, 
as,  for  example,  the  ascending  pharyngeal  and  the  lingual,  and  accessory  branches  may  arise 
from  its  intracranial  portion. 

Practical  Considerations. — The  internal  carotid  artery,  on  account  of  its 
deeper  position,  is  not  so  often  wounded  as  the  external  carotid.  It  has  been  punc- 
tured through  the  pharynx  and  has  been  wounded  in  tonsillotomy  (page  1608). 

Aneurism  of  the  internal  carotid  is  not  common.  When  it  involves  the  petrosal 
or  i?itracra?iial  portio?i  of  the  vessel  it  causes  symptoms  referrible  to  those  regions 
and  better  dealt  with  after  the  venous  system  has  been  described  (page  873).  In 
its  cervical  portion  it  shows  a  tendency  to  become  tortuous  in  elderly  persons, 
owing  doubtless  to  its  fixity  above,  where  it  enters  the  carotid  canal,  and  to  the  rela- 
tive lack  of  fixation  below  (Taylor). 

As  the  artery  is  crossed  externally  by  the  dense  layers  of  the  deep  cervical 
fascia,  and  by  the  stylo-hyoid,  stylo-glossus,  stylo-pharyngeus,  and  digastric  mus- 
cles, the  progress  of  a  swelling  in  this  direction  is  strongly  resisted.  Internally  the 
middle  constrictor  and  mucous  membrane  of  the  pharynx  offer  far  less  obstruction  to 
the  extension  of  the  aneurism,  and  in  many  of  the  recorded  cases  a  pulsating  pha- 
ryngeal protrusion  has  been  the  chief  symptom.  The  effects  of  pressure  on  surround- 
ing structures,  the  internal  jugular  vein,  and  the  pneumogastric  and  sympathetic 
nerves,  for  example,  are  not  unlike  those  observed  in  other  carotid  aneurisms.  The 
direct  interference  with  cerebral  circulation  is  greater  in  aneurism  of  the  internal 
carotid,  and  vertigo,  headache,  drowsiness,  etc. ,  are  apt  to  be  more  conspicuous  as 
early  symptoms. 

Ligation.  — The  vessel  may  be  reached  close  to  its  origin  and  tied  through  the 
same  incision  as  that  used  in  ligating  the  external  carotid  (page  733).  The  sterno- 
mastoid  muscle  is  drawn  outward,  the  digastric  muscle  and  hypoglossal  nerve 
(which  are  usually  seen)  upward,  and  the  external  carotid  artery  inward.  The  two 
vessels  should  be  carefully  distinguished.      The  needle  should  be  passed  from  with- 


74S 


HUMAN    ANATOMY. 


out  inward,  avoiding  the  internal  jugular  vein,  the  pneumogastric  and  sympathetic 
nerves,  and  the  ascending  pharyngeal  and  external  carotid  arteries. 

The  collateral  circulation  is  carried  on  through  the  vertebrals  and  the  vessels  of 
the  circle  of  Willis  and  is  freely  re-established. 

i.  The  Tympanic  Artery. — The  tympanic  artery  (ramus  caroticotympani- 
cus)  is  a  small  vessel  which  arises  from  the  petrosal  portion  of  the  internal  carotid. 
It  passes  through  a  foramen  in  the  wall  of  the  carotid  canal  to  supply  the  mucous 
membrane  of  the  middle  ear,  anastomosing  with  the  tympanic  branches  of  the  stylo- 
mastoid and  internal  maxillary  arteries.     • 

Fig.  696. 


Nasal  artery 
Supraorbital  artery 


Inferior  palpebral 

branch 

Frontal  artery 

Nasal  artery 

Anterior  ethmoidal 

branch 

Supraorbital  artery 

Posterior  ethmoidal  -^ 
branch 

Superior  obliqu 


Optic 


Internal  carotid  artery 
Posterior  clinoid  process 


Internal  carotid, 


Branches  of  right  ophthalmic  artery,  seen  from  above  after 


1  of  roof  of  orbit. 


2.  The  Anterior  Meningeal  Arteries. — The  anterior  meningeal  arteries 
are  a  number  of  small  branches  which  arise  from  the  intracranial  portion  of  the  inter- 
nal carotid  and  are  supplied  to  the  neighboring  dura  mater,  anastomosing  with  the 
branches  of  the  anterior  ramus  of  the  middle  meningeal  artery. 

3.  The  Ophthalmic  Artery.— The  ophthalmic  artery  (a.  ophthalmica)  (Figs. 
696,  697)  arises  from  the  internal  carotid  immediately  after  it  has  issued  from  the  roof 
of  the  cavernous  sinus.  It  passes  forward  beneath  the  optic  nerve  and  traverses  the 
optic  foramen  with  that  structure.  In  the  orbit  it  ascends  to  the  outer  side  of  the 
optic  nerve  and,  crossing  over  it,  passes  in  a  sinuous  course  towards  the  inner  wall 


THE    OPHTHALMIC   ARTERY.  749 

of  the  orbit,  along  which  it  runs  between  the  superior  oblique  and  internal  rectus 
muscles  to  the  inner  angle,  where  it  terminates  by  dividing  into  palpebral,  frontal, 
and  nasal  branches. 

Branches. — (a)  The  arteria  centralis  retinae  arises  from  the  ophthalmic  while  that  vessel 
is  still  below  the  optic  nerve.  It  runs  forward  along  the  under  surface  of  the  nerve  to  a  point 
about  15  mm.  from  the  posterior  surface  of  the  eye,  where  it  passes  into  the  substance  of  the 
nerve  and  continues  its  course  forward  in  the  centre  of  that  structure.  Arrived  at  the  retina, 
the  artery  divides  into  two  main  branches,  one  ascending  and  the  other  descending,  and  these, 
branching  repeatedly,  form  an  arterial  net-work-  upon  the  surface  of  the  retina.  The  finer 
branches  of  the  net-work  extend  deeply  into  the  substance  Of  the  retina,  although  none  reach 
the  layer  of  visual  cells.  They  pass  over  directly  into  the  corresponding  veins  without  making 
connections  with  any  of  the  other  arteries  supplied  to  the  eyeball.  Just  after  its  entrance  into 
the  eyeball,  however,  the  main  stem  of  the  artery  anastomoses  with  the  short  ciliary  vessels. 

(b)  The  ciliary  arteries,  which  are  distributed  to  the  choroid  coat,  the  ciliary  processes,  and 
the  iris,  are  somewhat  variable  in  their  number  and  origin.  Two  sets  are  distinguishable,  and 
are  named  from  their  relative  position  the  posterior  and  anterior  ciliary  arteries. 

(aa)  The  posterior  ciliary  arteries  (aa.  ciliares  posteriores)  arise  from  the  ophthalmic  artery 
as  it  crosses  over  the  optic  nerve,  either  as  two  trunks  which  pass  forward,  the  one  on  the  inner 
and  the  other  on  the  outer  side  of  the  optic  nerve,  or  else  as  a  variable  number  of  small  vessels. 
Eventually  the  vessels  break  up  into  from  ten  to  twenty  branches,  which  surround  the  distal 
portion  of  the  optic  nerve,  and,  piercing  the  sclerotic,  are  distributed  to  the  choroid  coat  of  the 
eye.  Two  of  the  vessels,  lying  one  on  either  side  of  the  optic  nerve,  are  usually  stronger  than 
the  others,  pierce  the  sclerotic  some  distance  '  nearer  the  equator  of  the  eyeball,  and  are 
termed  the  long  posterior  ciliary  arteries  (aa.  ciliares  posteriores  longae).  They  pass  forward 
between  the  sclerotic  and  choroid  coats,  send  branches  to  the  ciliary  muscle,  and  divide  at  the 
peripheral  border  of  the  iris  into  two  stems,  which,  passing  around  the  iris,  unite  with  their 
fellows  of  the  opposite  side  and  with  branches  of  the  anterior  ciliary  arteries  to  form  the 
circulus  arteriosus  iridis,  from  which  branches  radiate  to  the  iris  and  the  ciliary  processes. 

(bb)  The  anterior  ciliary  arteries  (aa.  ciliares  anteriores)  usually  take  their  origin  from  the 
muscular  branches  of  the  ophthalmic  and  accompany  the  tendons  of  the  recti  muscles  (two 
arteries  being  associated  with  each  muscle,  except  in  the  case  of  the  external  rectus,  where 
there  is  only  one)  to  the  sclerotic,  where  they  send  off  perforating  branches  which,  after 
piercing  the  sclerotic,  unite  with  the  long  ciliaries  to  form  the  arterial  circle  of  the  iris.  The 
main  stems  are  continued  onward  towards  the  margin  of  the  cornea,  where  they  divide  and 
anastomose  to  form  a  narrow  net-work  surrounding  that  portion  of  the  eyeball  and  also  give 
branches  to  the  conjunctiva.  An  anterior  ciliary  vessel  is  frequently  contributed  by  the 
lachrymal  artery. 

(c)  The  lachrymal  artery  (a  lacrimalis)  arises  from  the  ophthalmic  as  it  passes  upward  over 
the  external  surface  of  the  optic  nerve  and  passes  forward  and  outward,  in  company  with  the 
lachrymal  nerve,  along  the  upper  border  of  the  external  rectus  muscle.  It  traverses  the  substance 
of  the  lachrymal  gland,  to  which  it  gives  branches,  and  terminates  in  small  branches  to  the  eye- 
lids'. In  its  course  it  gives  off  a  number  of  small  twigs  to  the  external  rectus  muscle  ;  a  menin- 
geal branch,  which  passes  back  into  the  cranium  through  the  sphenoidal  fissure  and  anasto- 
moses with  the  middle  meningeal ;  and  a  malar  branch,  which  passes  to  the  temporal  fossa 
through  a  small  canal  in  the  malar  bone  and  anastomoses  with  the  anterior  deep  temporal  and 
the  transverse  facial  arteries. 

(d)  The  muscular  branches  ( rami  musculares)  are  somewhat  irregular  in  their  number  and 
origin.  Usually  there  are  two  principal  stems  and  a  variable  number  of  small  twigs,  but  occa- 
sionally the  two  principal  stems  arise  by  a  common  trunk.  When  the  two. are  distinct,  the  in- 
ferior one  arises  close  to  the  lachrymal,  and  is  distributed  to  the  inferior  and  internal  recti  and 
the  inferior  oblique  muscles  ;  while  the  superior,  smaller  and  less  constant,  arises  after  the  oph- 
thalmic has  crossed  over  the  optic  nerve,  and  is  distributed  to  the  superior  and  external  muscles 
of  the  orbit.  In  addition  to  branches  to  the  muscles,  these  arteries  also  give  origin  to  the 
anterior  ciliary  arteries  described  above. 

(e)  The  supraorbital  artery  (a.  supraorbitalis)  arises  as  the  ophthalmic  passes  over  the  optic 
nerve.  It  is  at  first  directed  upward,  and  then  passes  forward  between  the  periosteum  of  the 
roof  of  the  orbit  and  the  levator  palpebral  superioris,  and,  making  its  exit  from  the  orbit  through 
the  supraorbital  notch  or  foramen,  terminates  in  branches  which  ascend  over  the  frontal  bone 
towards  the  vertex  of  the  skull,  supplying  the  integument  and  periosteum  and  anastomosing 
with  the  superficial  temporal  artery.  In  its  course  through  the  orbit  it  gives  off  periosteal, 
diploic,  and  muscular  twigs,  and,  after  its  exit  from  the  supraorbital  notch,  a  palpebral  branch 
to  the  upper  eyelid. 

(f)  The  ethmoidal  arteries  are  two  in  number,  and  arise  from  the  ophthalmic  as  it  passes 
along  the  inner  wall  of  the  orbit.     The  posterior  ethmoidal  (a.  ethnioidalis  posterior) ,  which  is  the 


75Q 


HUMAN    ANATOMY. 


smaller  and  less  constant  of  the  two,  passes  through  the  posterior  ethmoidal  foramen  and  is 
distributed  to  the  mucous  membrane  lining  the  posterior  ethmoidal  cells  and  the  upper  poste- 
rior part  of  the  nasal  septum,  where  it  anastomoses  with  the  spheno-palatine  branch  of  the 
internal  maxillary.  It  sometimes  arises  from  the  supraorbital  artery.  The  anterior  ethmoidal 
(a.  ethmoidals  anterior)  passes  through  the  anterior  ethmoidal  foramen  along  with  the  nasal 
nerve,  and,  entering  the  cranium,  passes  forward  over  the  cribriform  plate  of  the  ethmoid  to  the 
nasal  slit  at  the  side  of  the  crista  galli.  Through  this  slit  it  enters  the  nasal  cavity  and  passes 
downward  in  a  groove  upon  the  under  surface  of  the  nasal  bone,  supplying  the  nasal  mucous 
membrane.  While  within  the  cranium  it  gives  off  a  small  meningeal  branch  to  the  dura  mater 
of  the  anterior  portion  of  the  cranium,  and  it  also  sends  branches  to  the  mucous  membrane 
lining  the  anterior  and  middle  ethmoidal  cells  and  the  frontal  sinuses. 

(  g)  The  palpebral  branches  (aa.  palpebrals  mediates)  are' two  in  number,  and  are  distrib- 
uted to  the  upper  and  lower  eyelids  respectively.  They  arise  opposite  the  pulley  of  the  superior 
oblique  muscle  and  descend  towards  the  inner  canthus  of  the  eye.  Each  artery  then  bends  out- 
ward towards  the  outer  canthus  along  the  free  border  of  the  lid,  between  the  tarsal  cartilage 
and  the  orbicularis  muscle,  forming  the  palpebral  arches  (arcus  tarseus  superior  et  inferior), 

Fig.  697. 


Lacrimal  artery 
Anterior  ethmoidal 


Posterior  ethmoid 
Ophthalmic  artery 
Opt! 


Internal  carotid  artery 
Posterior  clinoid 
process 
Int.  carotid  artery, 
cavernous  portion     . 


Arteria  centralis  retinas 
Long  posterior  ciliary  artery 
Short  posterior  ciliary  arteries 

Internal  maxillary  artery 


Supraorbital 
artery 
Frontal  artery 

Nasal  artery 
Superior  and  in- 
ferior palpebral 
arteries 
Angular  artery 
Anterior  cilian 
arteries 


Infraorbital 
artery 
Facial  artery 


Branches  of  ophthalmic  artery, 


,  from  side  after  removal  of  lateral  orbital  1 


from  which  branches  pass  upward  or  downward,  as  the  case  may  be,  to  supply  the  orbicularis, 
the  Meibomian  glands,  and  the  integument  of  the  lid.  As  they  approach  the  outer  canthus,  the 
arches  anastomose  with  the  palpebral  branches  of  the  lachrymal  artery. 

(h)  The  frontal  branch  (a.  frontalis)  is  usually  small,  and  is  distributed  to  the  integument 
over  the  glabella  and  to  the  pyramidalis  nasi  and  frontalis  muscles.  It  also  sends  some  twigs 
to  the  eyelids. 

(i)  The  nasal  artery  (a.  dorsalis  nasi)  is  the  true  terminal  branch  of  the  ophthalmic.  It 
passes  downward  in  the  angle  formed  by  the  nose  and  the  lower  eyelid  and  becomes  directly 
continuous  with  the  angular  portion  of  the  facial  artery.  In  its  course  it  gives  branches  to  the 
walls  of  the  lachrymal  sac  and  to  the  integument  of  the  root  of  the  nose. 

Anastomoses. — The  principal  communications  of  the  ophthalmic  artery  are 
with  the  superficial  temporal,  internal  maxillary,  and  facial  branches  of  the  external 
carotid.  With  the  first  of  these  it  communicates  extensively  by  means  of  the  supra- 
orbital branch  and  less  importantly  through  the  anastomosis  of  the  malar  branch  of 
the   lachrymal  with  the  transverse  facial  artery.      It  makes  a  very  important   anasto- 


THE    POSTERIOR    COMMUNICATING    ARTERY. 


751 


mosis  with  the  middle  meningeal  branch  of  the  internal  maxillary  through  the  lachry- 
mal branch,  and  communicates  also  with  the  spheno-palatine  artery  by  means  of  the 
ethmoidal  branches.      The  anastomosis 


Fig  69S. 


of  the  nasal  branch  with  the  angular  ar- 
tery from  the  facial  is  also  a  large  one,  the 
two  vessels  being  practically  continuous. 

Variations. — In  addition  to  the  varia- 
tions in  the  number  and  origins  of  its 
branches,  the  ophthalmic  artery  also  presents 
variations  in  its  course,  in  that,  instead  of  pass- 
ing to  the  inner  wall  of  the  orbit  above  the  op- 
tic nerve,  it  sometimes  passes  below  that 
structure.  The  most  striking  variation  which 
it  presents,  however,  is  associated  with  the 
development  of  the  branch  of  the  lachrymal 
artery,  which  passes  back  through  the  sphe- 
noidal fissure  to  anastomose  with  the  middle 
meningeal  (Fig.  69S).  Occasionally  this 
branch  becomes  exceptionally  large  and  forms 
the  main  stem  of  the  lachrymaf  artery,  the 
connection  of  that  vessel  with  the  ophthalmic 
vanishing,  so  that  it  seems  to  be  a  branch  of 
the  middle  meningeal.  A  further  step  in  this 
process  which  sometimes  occurs  results  in  the 
origin  of  the  entire  ophthalmic  system  of  ves- 
sels from  the  middle  meningeal  artery. 

4.   The  Posterior  Communicating  Artery. — The  posterior  communicating 
artery  (a.  comraunicans  posterior)  (Fig.  702)  arises  from  the  posterior  surface  of  the 


Variations  of  ophthalmic  artery  ;  lachrymal  coming 
chiefly  from  middle  meningeal.     (Meyer.) 


Fig.  699. 


Branch  of  ascending  frontal  artery 
Parietal  artery 

2  of  Rolando 


Precentral  sulcus 

Ascending  frontal  artery 


Branches 
>f  anterior 
erebral 
f     \  artery 
jBRr      External 
^^ orbital  artery 


Inferior  frontal  artery 


Middle  cerebral 
artery 


Parieto-temporal  arteries 


artery 


Anterior  inferior 
cerebellar  artery 


Basila 
Pons 
Left  vertebral  artery 
Middle  cerebellar  pedu 

Right  vertebral  artery 


Lateral  surface  of  brain,  showing  cortical  branches  of  middle  cerebral  artery  ;  those  of  anterior  and  posterior 
cerebral  arteries  are  seen  curving  over  supero-mesial  border  of  "cerebral  hemisphere. 

internal  carotid,   opposite    the  sella  turcica.      It   is  directed  backward  beneath  the 
optic  tract  and  the  inner  border  of  the  crus  cerebri,  and  terminates  posteriorly  by 


752 


HUMAN    ANATOMY. 


opening  directly  into  the  posterior  cerebral  artery.      In  its  course  it  gives  off  twigs 
to  the  tuber  cinereum,  the  corpora  albicantia,  and  the  crus  cerebri. 

5.  The  Anterior  Choroid  Artery. — The  anterior  choroid  artery  (a.  choroi- 
dea)  (Fig.  702)  arises  from  the  posterior  surface  of  the  internal  carotid,  slightly 
distal  to  the  posterior  communicating  artery.  It  is  directed  outward  and  backward 
at  first,  and  then,  curving  upward  between  the  brain-stem  and  the  temporal  lobe,  it 
gives  branches  to  the  hippocampus  major.  It  is  then  continued  upward  and  for- 
ward as  the  artery  of  the  choroid  plexus  of  the  lateral  ventricle,  and  anastomoses  at 
the  foramen  of  Monro  with  the  artery  of  the  choroid  plexus  of  the  third  ventricle, 
which  comes  from  the  superior  cerebellar  branch  of  the  basilar  artery. 

6.  The  Middle  Cerebral  Artery. — The  middle  cerebral  artery  (a.  cerebri 
media)  (Figs.  699,  702)  is  one  of  the  terminal  branches  of  the  internal  carotid.  It 
passes  at  first  outward  to  the  lower  end  of  the  Sylvian  fissure,  and  is  then  directed 
backward  and  upward,  lying  at  first  deeply  in  the  fissure  close  to  the  surface  of  the 

Fig.  700. 

Middle  internal  frontal  artery 


External  orbital  artery 

Middle  cerebral  artery 
From  temporal  branch  of  middle  cerebral 

nunicatin^  artery 


Posterior  cerebral  artery 


Mesial  surface  of  cerebral  hemisphere,  showing  cortical  blanches  of  anterior 
and  posterior  cerebral  arteries. 


island  of  Reil,  but  gradually  becoming  more  superficial  until  at  the  posterior  ex- 
tremity of  the  horizontal  limb  of  the  fissure  it  reaches  the  surface  and  divides  into 
branches  which  ramify  over  the  lateral  surface  of  the  cerebral  hemisphere. 

Branches. — In  its  course  outward  to  enter  the  Sylvian  fissure  it  gives  off  a  number  of  small 
central  branches  which  penetrate  the  substance  of  the  cerebral  hemisphere  at  the  anterior  per- 
forated space,  and,  as  the  striate  arteries,  supply  the  corpus  striatum.  These  antero-lateral 
ganglionic  branches,  as  they  are  often  called,  are  arranged  as  two  groups  :  (a)  the  internal 
striate  arteries,  which  pass  upward  through  the  lenticular  nucleus  (globus  pallidus)  and  the 
internal  capsule  and  end  in  the  caudate  nucleus,  supplying  the  anterior  part  of  the  structures 
traversed  ;  (6)  the  external  striate  arteries,  which  after  traversing  the  putamen  and  the  internal 
capsule  terminate  in  either  the  caudate  nucleus  or  the  optic  thalamus.  One  of  the  former 
(lenticulo-striate)  vessels,  which  passes  around  the  outer  border  of  the  lenticular  nucleus  before 
traversing  its  substance,  is  larger  than  the  others  and,  since  it  frequently  ruptures,  is  known  as 
the  arteiy  of  cerebral  hemorrhage.  While  in  the  Sylvian  fissure  the  middle  cerebral  artery 
gives  off  numerous  branches  to  the  cortex  of  the  island  of  Reil  and  continues  into  the  cortical 
branches,  which  are  distributed  to  the  lateral  surface  of  the  hemisphere  and  are  usually  four  in 


THE    SUBCLAVIAN    ARTERY.  753 

number,  (a)  The  inferior  frontal  is  distributed  to  the  inferior  frontal  convolutions,  (b)  the 
ascending  frontal  passes  to  the  lower  portion  of  the  ascending  frontal  convolution,  (c)  the 
parietal  supplies  the  whole  of  the  ascending  parietal  convolution  and  the  neighboring  portions 
of  the  inferior  parietal,  and  (d)  the  parietotemporal  passes  to  all  the  convolutions  around  the 
posterior  limb  of  the  fissure  of  Sylvius. 

7.  The  Anterior  Cerebral  Artery. — The  anterior  cerebral  artery  (a.  cerebri 
anterior)  (Fig.  700)  is  the  smaller  of  the  terminal  branches  of  the  internal  carotid. 
It  passes  forward  above  the  optic  chiasma  to  the  anterior  end  of  the  great  longitudi- 
nal fissure,  and,  bending  upward  around  the  rostrum  of  the  corpus  callosum,  is  con- 
tinued backward  along  the  medial  surface  of  the  cerebral  hemisphere  to  the  posterior 
portion  of  the  parietal  lobe.  At  its  entrance  into  the  great  longitudinal  fissure  it  is 
connected  with  its  fellow  of  the  opposite  side  by  a  short  transverse  vessel  termed 
the  anterior  communicating  artery  (Fig.  702). 

Branches.— Immediately  after  it  has  crossed  the  optic  chiasma  the  anterior  cerebral  artery 
gives  off  a  number  of  small  central  branches  (antero-mesial  ganglionic) ,  which  penetrate  the 
base  of  the  brain  and  are  distributed  to  the  lamina  cinerea,  the  rostrum  of  the  corpus  callosum, 
the  septum  lucidum,  and  the  tip  of  the  caudate  nucleus.  Throughout  its  course  in  the  great 
longitudinal  fissure  it  gives  branches  to  the  corpus  callosum  and  also  cortical  branches  to  the 
medial  and  lateral  surfaces  of  the  cerebral  hemisphere.  These  branches  are  (a)  the  orbital, 
which  vary  in  number  and  are  distributed  to  the  orbital  surface  of  the  frontal  lobe,  also  sup- 
plying the  olfactory  bulb  ;  (b)  the  anterior  internal  frontal,  which  supplies  the  anterior  and 
lower  part  of  the  marginal  convolution  and  sends  branches  to  the  lateral  surface  of  the  hemis- 
phere supplying  the  superior  and  middle  frontal  convolutions  ;  (c)  the  middle  internal  frontal, 
which  is  distributed  to  the  middle  and  posterior  parts  of  the  marginal  convolution  and  to  the 
adjacent  portions  of  the  superior  and  ascending  frontal  and  ascending  parietal  convolutions  ; 
and  (d)  the  posterior  internal  frontal  or  quadrate,  which,  in  addition  to  sending  branches  to  the 
corpus  callosum,  supplies  the  quadrate  lobe  and  the  upper  part  of  the  superior  parietal  convo- 
lution. These  branches  anastomose  upon  the  inferior  and  lateral  surfaces  of  the  hemisphere 
with  the  branches  of  the  middle  cerebral  artery,  the  main  stem  of  the  artery  anastomosing 
posteriorly  with  branches  of  the  posterior  cerebral. 

Anastomoses  of  the  Carotid  System. — Although  the  majority  of  the 
anastomoses  of  the  branches  of  the  carotid  arteries  are  with  one  another,  yet  there  is 
a  sufficient  amount  of  communication  with  other  vessels  to  allow  of  the  establishment 
of  a  collateral  circulation  after  ligation  of  the  common  carotid  of  one  side.  The  con- 
nections which  are  available  for  the  circulation  in  such  a  case  are  as  follows.  ( 1 ) 
There  is  abundant  communication  between  the  branches  of  the  right  and  left  external 
carotids  across  the  median  line;  (2)  the  anterior,  communicating  artery  forms  an 
important  communication  between  the  internal  carotids  of  opposite  sides  ;  (3) 
anastomoses  exist  between  the  ascending  cervical  branch  of  the  inferior  thyroid,  the 
superficial  cervical  branch  of  the  transversalis  colli,  and  the  deep  cervical  branch  of 
the  superior  intercostal,  on  the  one  hand,  all  of  these  being  branches  of  the  sub- 
clavian artery,  and  the  a.  princeps  cervicis,  a  branch  of  the  occipital  artery  ;  (4) 
abundant  communications  exist  between  the  terminal  branches  of  the  inferior  thyroid 
from  the  subclavian  and  the  superior  thyroid  from  the  external  carotid  ;  and,  finally, 
(5)  by  means  of  the  posterior  communicating  artery  the  internal  carotid  may 
receive  blood  from  the  posterior  cerebral  artery,  which,  through  the  basilar  and 
vertebral  arteries,  belongs  to  the  subclavian  system. 

THE  SUBCLAVIAN  ARTERY. 

In  the  primary  arrangement  of  the  branchial  blood-vessels,  while  there  are  two 
aortic  arches  (Fig.  678),  the  two  subclavian  arteries  arise  symmetrically  from  these 
arches  as  lateral  segmental  branches  corresponding  to  the  seventh  cervical  segment. 
With  the  disappearance  of  the  lower  portion  of  the  right  arch,  however,  an  apparent 
lack  of  symmetry  in  their  origin  supervenes,  the  vessel  of  the  right  side  arising  from 
the  innominate  stem,  while  that  of  the  left  side  springs  directly  from  the  persist- 
ing aortic  arch.  As  a  matter  of  fact,  however,  the  proximal  portion  of  the  right  aortic 
arch _ is  represented  by  the  innominate  stem,  together  with  a  small  portion  of  the 
proximal  end  of  the  right  subclavian  artery,  so  that  the  original  morphological  sym- 


754 


HUMAN   ANATOMY. 


metry  is  retained  ;  but,  since  a  portion  of  the  original  right  aortic  arch  is  included  in 
the  adult  right  subclavian,  this  vessel  is  a  little  more  than  equivalent  to  its  fellow 
of  the  opposite  side.  Furthermore,  since  the  innominate  stem  ascends  directly 
upward  from  its  origin,  a  topographical  asymmetry  of  the  two  vessels  results. 

The  origin  of  the  right  subclavian  is  opposite  the  right  sterno-clavicular  articula- 
tion, and  from  that  point  the  artery  ascends  upward  and  outward  in  a  gentle  curve 
over  the  dome  of  the  pleura  to  the  inner  border  of  the  scalenus  anticus.  The  origin 
of  the  left  subclavian  is  from  the  termination  of  the  transverse  portion  of  the  aortic 
arch,  and  is  consequently  much  deeper  in  the  thorax  (Fig.  690).  From  its  origin 
it  ascends  at  first  almost  vertically  and  then  curves  outward  and  slightly  forward  to 
reach  the  inner  border  of  the  scalenus  anticus.  From  this  point  onward  the  course  of 
the  two  arteries  is  the  same.  Passing  behind  the  anterior  scalene  muscle,  each  artery 
continues  its  course  outward  across  the  root  of  the  neck,  curving  downward  to  the 
outer  border  of  the  first  rib,  at  which  point  it  becomes  known  as  the  axillary  artery. 

Fig.  701. 


Descending 
branches  of 

vical  plexus  — 


Brachial  plexus 
Suprascapular 

vessels 


Subclavian  artery" 

Subclavian  ve: 


External  jugular  vein 

Anterior  scalene  muscle 
Phrenic  nerve 

Internal  jugular  vein 
Sternal  portion  of 

sterno-mastoid 
Common  carotid  artery 
Sterno-hyoid  muscle 

First  rib 


od-vessels  and  i 


In  consequence  of  the  difference  in  origin,  the  right  subclavian  artery  is  usually 
approximately  7.5  cm.  (3  in.)  in  length,  or  about  one  inch  shorter  than  the  left. 
In  its  course  across  the  root  of  the  neck  the  height  which  the  subclavian  artery 
may  reach  varies  considerably  in  different  individuals  ;  in  some  it  never  rises  above 
the  clavicle,  while  in  others  its  highest  point  may  be  from  2. 5-3  cm.  ( 1-1  y2  in. ) 
above  that  bone.  Most  frequently  it  reaches  a  point  about  1 . 5  cm.  (S/%  in. )  above  the 
clavicle,  this  highest  point  being  reached  as  it  passes  beneath  the  scalenus  muscle. 
As  it  commences  its  downward  course  towards  the  first  rib,  the  artery  undergoes  a 
more  or  less  pronounced  diminution  in  diameter,  which  persists  for  a  distance  of  from 
0.5-1  cm.,  and  is  followed  by  an  enlargement  to  about  its  original  size,  what  has 
been  termed  an  arterial  isthmus  and  spindle  thus  resulting  (page  720). 

Relations. — For  convenience  in  description,  the  subclavian  artery  is  usually 
regarded  as  consisting  of  three  portions.  The  first  portion  extends  from  its  origin 
to  the  inner  edge  of  the  scalenus  anticus,  the  second  portion  lies  behind  that  muscle, 


THE   SUBCLAVIAN    ARTERY.  755 

while  the  third  portion  extends  from  the  outer  border  of  the  scalenus  to  the  con- 
ventional termination  of  the  artery  at  the  lower  border  of  the  first  rib.  On  account 
of  the  difference  in  their  origins,  the  relations  of  the  first  portions  of  the  right  and 
left  vessels  differ  somewhat. 

The  first  portion  of  the  right  subclavian  artery  lies  behind  the  clavicular 
portion -of  the  sterno-cleido-mastoid,  and  is  crossed  in  front  by  the  internal  jugular 
and  vertebral  veins  and  by  the  right  pneumogastric,  phrenic,  and  superior  sympa- 
thetic cardiac  nerves.  Behind,  it  is  in  relation  with  the  transverse  process  of.  the 
seventh  cervical  vertebra,  with  the  inferior  cervical  sympathetic  ganglion,  and  with 
the  right  recurrent  laryngeal  nerve,  which  winds  around  its  under  surface  from  in 
front.      Below,  it  is  in  contact  with  the  dome  of  the  right  pleura. 

The  first  portion  of  the  left  subclavian  artery,  at  its  origin,  is  deeply  seated 
in  the  thoracic  cavity  and  ascends  almost  vertically  through  the  superior  mediastinum. 
Behind,  and  somewhat  medial  to  it,  are  the  cesophagus,  the  thoracic  duct,  and  the 
longus  colli  muscle,  and  at  its  emergence  from  the  thorax  the  lower  cervical  sympa- 
thetic ganglion.  Medial,  or  internal  to  it,  are  the  trachea  and  the  left  recurrent  laryn- 
geal nerve,  and  lateral  to  it,  on  its  left  side,  are  the  left  pleura  and  lung,  which  also 
overlap  it  in  front.  Near  its  origin  it  is  o-ossed  by  the  left  innominate  (brachio- ceph- 
alic) vein,  and,  shortly  before  it  passes  over  into  the  second  portion,  it  is  crossed  by  the 
internal  jugular,  vertebral,  and  subclavian  veins,  as  well  as  by  the  phrenic  nerve  and 
the  thoracic  duct,  the  latter  arching  over  it  to  reach  its  termination  in  the  subclavian 
vein.  The  left  pneumogastric  and  cardiac  sympathetic  nerves  descend  into  the 
thorax  in  front  of  it,  the  pneumogastric,  before  passing  over  the  aortic  arch,  coming 
into  contact  with  the  anterior  surface  of  the  vessel.  As  it  emerges  from  the  thorax 
the  subclavian  lies  behind  the  clavicular  portion  of  the  sterno-cleido-mastoid.  In  the 
neck  it  rests  below  upon  the  dome  of  the  left  pleura. 

The  second  portion  of  the  subclavian  artery,  the  relations  of  which 
and  of  the  succeeding  portion  of  the  vessel  are  the  same  on  both  sides,  in  front 
is  covered  by  the  scalenus  anticus  muscle,  anterior  to  which  and  on  a  slightly  lower 
plane  is  the  subclavian  vein.  Behind  and  above  it  are  the  trunks  of  the  brachial 
plexus,  which  separate  it  from  the  scalenus  medius,  and  below  it  is  in  contact  with 
the  pleura. 

The  third  portion  of  the  subclavian  artery  lies  in  the  supraclavicular  fossa, 
and  is  covered  only  by  the  skin,  the  platysma,  and  that  part  of  the  deep  cervical 
fascia  which  contains  the  external  jugular  vein  and  the  supraclavicular  branches  of 
the  cervical  plexus,  and  encloses  a  quantity  of  fatty  tissue,  in  which  the  suprascapular 
artery  passes  outward.  Behind,  it  is  in  contact  with  the  scalenus  medius  and  the 
brachial  plexus,  and  above  it  are  the  brachial  plexus  and  the  posterior  belly  of  the 
omo-hyoid.  Below,  it  rests  upon  the  first  rib,  at  the  lower  border  of  which  the  vessel 
becomes  the  axillary  artery. 

Branches. — Considerable  variation  exists  in  the  arrangement  of  the  branches 
of  the  subclavian,  but  in  what  is  probably  the  most  frequent  arrangement  the 
branches  are  as  follows  : 

From  the  first  portion  arise  (1)  the  vertebral,  (2)  the  internal  mammary,  (3) 
the  superior  intercostal,  and  (4)  the  thyroid  axis  ;  from  the  second  portion  no 
branches  are  given  off  ;  from  the  third  portion  (5)  the  transverse  cervical. 

Variations.  —The  variations  in  the  origin  of  the  subclavian  artery  have  already  been  consid- 
ered in  describing  the  variations  of  the  aortic  arch  (page  725).  Other  anomalies  occur  in  its 
relation  to  the  scalenus  anticus,  in  front  of  which  it  sometimes  passes,  and  it  may  also  traverse 
the  substance  of  the  muscle  obliquely.  More  rarely  the  artery  divides  at  the  inner  border  of  the 
muscle,  the  two  branches  so  formed  continuing  onward  through  the  axilla  and  down  the  arm 
to  become  the  radial  and  ulnar  arteries. 

Numerous  supernumerary  branches  may  arise  from  the  subclavian.  These  may  be  either 
(1)  accessory  to  the  branches  normally  arising  from  the  artery,  such  as  an  accessory  vertebral, 
an  accessory  internal  mammary,  or  an  accessory  inferior  thyroid  ;  (2)  they  may  be  branches, 
such  as  the  long  thoracic,  dorsal  scapular,  subscapular,  and  the  anterior  and  posterior  circum- 
flexes, which  normally  arise  from  the  axillary  artery,  but  have,  secondarily  shifted  to  the  sub- 
clavian as  the  result  of  the  enlargement  of  anastomoses  which  they  make  with  branches  of  that 
vessel  ;  or  (3)  they  may  be  branches  to  neighboring  organs,  such  as  a  bronchial  or  a  pericar- 
dial branch,  or  occasionally  the  thyroidea  ima  (page  729). 


756  HUMAN   ANATOMY. 

Practical  Considerations. — The  subclavian  artery  may  require  ligation,  on 
account  of  stab  wounds,  as  a  preliminary  to  the  removal  of  growths — axillary  or 
scapular — or  to  an  interscapulo-thoracic  amputation,  or  in  cases  of  axillary  or  sub- 
clavian aneurism,  or,  together  with  the  common  carotid  artery,  in  aortic  or 
innominate  aneurism. 

On  the  surface  of  the  neck  the  subclavian  artery  is  represented  by  a  curve, 
convex  upward,  beginning  at  the  sterno-clavicular  articulation  and  ending  beneath 
the  middle  of  the  clavicle,  its  highest  point  being  on  an  average  about  five-eighths 
of  an  inch  above  that  bone.  The  vein  is  lower,  is  in  front  of  the  artery  (separated 
from  it  by  the  scalenus  anticus  muscle),  and  is  usually  nearly  or  quite  under  cover 
of  the  clavicle. 

Aneurism  of  the  subclavian  is  more  frequent  on  the  right  side,  probably  because 
of  the  greater  use  and  consequent  greater  exposure  to  strain  of  the  right  upper 
extremity.  It  may  affect  any  portion  of  the  vessel,  but  the  third  portion — external 
to  the  scaleni,  where  it  is  least  supported  by  surrounding  muscles — is  most  com- 
monly involved  either  primarily  or  by  extension  of  an  aneurismal  dilatation  upward 
from  the  axillary  or  downward  from  the  arch  of  the  subclavian.  The  thoracic 
portion  of  the  left  subclavian  is  never  the  primary  seat  of  aneurism. 

The  symptoms  are:  (a)  pain  or  numbness  and  loss  of  power  in  the  arm  and 
hand  from  pressure  on  the  brachial  plexus  ;  (b~)  swelling  and  oedema  of  the  arm  and 
hand  from  pressure  on  the  subclavian  vein  ;  (c)  hiccough  or  irregular,  jerky  res- 
piration from  pressure  on  the  phrenic  nerve  :  (d)  vertigo,  somnolence,  defective 
vision,  from  compression  of  the  internal  jugular  ;  (e)  tumor,  usually  appearing  in 
the  posterior  inferior  cervical  triangle,  with  its  long  diameter  approximately  parallel 
with  the  clavicle,  and  extending  upward  and  outward  ;  exceptionally  it  grows  down- 
ward, but  this  is  rare  on  account  of  the  resistance  offered  by  the  clavicle,  the  first 
rib,  and  the  structures  filling  the  costo-clavicular  space. 

Digital  comp?-ession  of  the  first  and  second  portions  of  the  artery  is  practically 
impossible.  The  third  portion  may  be  imperfectly  occluded  by  making  strong 
pressure  directly  backward  just  above  the  clavicle,  a  little  external  to  its  middle,  so 
that  the  artery  may  be  flattened  out  or  narrowed  against  the  scalenus  medius  muscle 
and  the  seventh  cervical  transverse  process.  Much  more  effectual  pressure  may  be 
made  at  the  same  point,  especially  if  the  tip  of  the  shoulder  can  be  lowered  so  as  to 
carry  the  clavicle  downward  and  make  the  upper  surface  of  the  first  rib  more 
accessible,  in  a  direction  downward,  backward,  and  inward, — i.e.,  in  a  line  nearly  or 
quite  perpendicular  to  the  plane  of  that  surface.  The  vessel  is  thus  compressed 
against  it,  and  is  not  pushed  off  of  it.  It  will  be  useful  to  recall  that  the  outer  border 
of  the  scalenus  anticus  and  the  posterior  border  of  the  sterno-mastoid' — the  latter 
palpable  and  often  visible — are  approximately  on  the  same  line,  immediately  outside 
of  which  is  the  third  portion  of  the  vessel.  The  scalene  tubercle — the  elevation  or 
roughening  on  the  upper  surface  of  the  first  rib  between  the  shallow  depression  for 
the  subclavian  vein  and  the  deeper  groove  for  the  subclavian  artery — gives  attach- 
ment to  the  scalenus  anticus  and,  when  recognized,  serves  as  a  valuable  guide  to  the 
vessel. 

Ligation. — The  first  portion — between  the  origin  of  the  vessel  and  the  inner  side 
of  the  scalenus  anticus — has  been  ligated  with  uniformly  fatal  results.  On  the  left 
side  it  is  so  situated  as  to  depth,  origin  of  branches — the  vertebral,  internal  mammary, 
thyroid  axis,  and  superior  intercostal — and  contiguity  of  important  structures — the 
heart,  the  aorta,  the  pleura,  the  innominate  vein,  the  thoracic  duct,  the  pneumogastric, 
cardiac,  recurrent  laryngeal  and  phrenic  nerves — that  its  ligation  has  only  once 
been  accomplished  (Rodgers).  On  the  right  side  the  operative  procedure  is  some- 
what less  difficult,  but  many  of  the  relations  are  identical  {vide  sztpra),  and  the 
procedure  is  still  so  formidable  that  its  description  is  included  in  some  works  on 
operative  surgery  only  because  the  ligation  ' '  affords  good  practice  on  the  dead 
subject"  (Jacobson). 

The  steps  of  the  operation  are  the  same  as  those  in  ligation  of  the  innominate 
(page  729)  until  the  carotid  sheath  is  reached  and  opened.  The  internal  jugular 
vein  and  pneumogastric  nerve  should  be  drawn  aside  (inward,  Agnew  ;  outward, 
Barwell)  and  the  subclavian  recognized,  springing  from  the  bifurcation  of  the  innom- 


PRACTICAL  CONSIDERATIONS:    SUBCLAVIAN  ARTERY.        757 

inate  at  an  acute  angle  with  the  carotid  and  deeper  by  the  full  diameter  of  the 
latter.  The  needle  should  be  passed  from  below  upward,  while  the  pleura  is  gently 
depressed  with  the  finger. 

The  second  portion — behind  the  scalenus  anticus — has  in  a  few  cases  been  suc- 
cessfully ligated  for  aneurism  external  tp  it,  but  the  operation  does  not  require 
special  description.  It  is  identical  with  that  for  tying  the  third  portion,  with  the 
addition  of  more  extensive  division  of  the  clavicular  portion  of  the  sterno-mastoid 
and  a  partial  division  of  the  scalenus  anticus,  having  due  regard  to  the  position  of 
the  phrenic  nerve  on  the  inner  part  of  the  anterior  surface  of  that  muscle. 

The  third  portion — from  the  outer  edge  of  the  scalenus  anticus  to  the  lower 
border  of  the  first  rib — has  been  frequently  and  successfully  ligated.  Three  methods 
may  be  described  : 

1.  By  the  first  and  usual  one  it  is  approached  by  a  transverse  incision,  parallel 
with  the  clavicle  and  extending  along  the  base  of  the  posterior  cervical  triangle  from 
the  middle  of  the  clavicular  head  of  the  sterno-mastoid  to  the  anterior  border  of  the 
trapezius.  This  is  best  made  by  drawing  the  skin  down  and  incising  it  directly 
upon  the  bone,  in  this  way  easily  avoiding  the  external  jugular  vein.  The  platysma 
muscle  and  the  supraclavicular  nerves  are  divided  at  the  same  time.  On  releasing  the 
skin  the  wound  will  be  placed  about  a  half-inch  above  the  clavicle.  The  shoulder  is 
then  well  depressed  so  as  to  lower  this  bone  and  increase  the  supraclavicular  space. 
The  deep  fascia,  which,  as  it  is  attached  to  the  superior  border  of  the  clavicle,  is  not 
pulled  down  with  the  skin  and  platysma,  is  then  divided,  the  external  jugular  vein 
drawn  aside  or  tied  and  cut,  the  loose  cellular  tissue,  and  possibly  the  omo-hyoid 
aponeurosis,  scratched  through  or  cut,  and  one  or  the  other  of  four  landmarks  iden- 
tified :  (<z)  the  tense  outer  edge  of  the  anterior  scalene  muscle  or  (6)  the  scalene 
tubercle  at  the  insertion  of  that  muscle  into  the  first  rib,  the  artery  lying  just 
outside  these  on  the  rib;  (V)  the  first  rib  itself  traced  inward  with  the  finger  from  the 
outer  angle  of  the  wound  until  the  artery  is  reached  ;  (d)  the  lowest  cord  of  the 
brachial  plexus,  lying  immediately  above,  or  sometimes  slightly  overlapping  the  artery. 
The  cord  has  been  mistaken  for  the  vessel,  but  compression  between  the  finger  and 
the  rib  does  not  flatten  it  out,  as  in  the  case  of  the  artery,  and,  of  course,  does  not 
arrest  the  radial  pulse.  The  tubercle  is  often  poorly  developed,  and  has  a  less  close 
relation  to  the  vessel  when  the  latter  rises  high  above  the  clavicle.  The  process  of 
cervical  fascia  reaching  from  the  posterior  border  of  the  scalenus  to  the  sheath  of  the 
artery  may  be  so  tense  as  to  obscure  to  both  sight  and  touch  the  line  of  the  outer 
edge  of  the  muscle 

The  artery  is  cautiously  denuded,  care  being  taken  to  avoid  injury  to  the 
pleura  or  to  the  subclavian  vein.  The  transverse  cervical  artery  is  usually  above 
and  the  suprascapular  artery  below  the  line  of  incision.  The  phrenic  nerve  has 
been  known  to  pass  directly  over  the  third  portion  of  the  subclavian  (Agnew), 
and  the  possibility  of  the  presence  of  this  rare  anomaly  should  be  remembered. 
The  needle,  the  tip  kept  between  the  artery  and  the  rib,  is  passed  from  above  down- 
ward, and  from  behind  forward  and  a  little  inward.  In  the  case  of  a  high  arch  of  the 
subclavian  the  third  portion  is  nearly  vertical,  and  it  would  then  be  more  correct  to 
speak  of  passing  the  needle  from  without  inward. 

2.  The  middle  of  the  clavicle  for  two  or  more  inches,  or  the  whole  clavicle;  may 
be  resected  subperiosteally,  as  in  interscapulo-thoracic  amputations,  and  the  ap- 
proach to  the  artery  greatly  facilitated. 

3.  By  strongly  elevating — instead  of  depressing — the  shoulder  and  clavicle, 
using  the  arm  as  a  tractor,  the  artery  may  be  exposed  by  an  incision  just  beloiv  and 
parallel  with  the  middle  of  the  clavicle.  A  portion  of  the  outer  edge  of  the  pec- 
toralis  major  and  some  of  the  inner  deltoid  fibres  will  usually  have  to  be  divided, 
although  it  may  be  possible  to  gain  sufficient  room  by  drawing  the  margin  of  the 
former  muscle  inward  and  that  of  the  latter  outward.  The  cephalic  vein  dipping  in 
through  this  intermuscular  depression  (Mohrenheim's  fossa)  to  join  the  axillary 
vein  must  be  avoided.  The  artery  is  found  lying  between  the  vein  internally  and 
the  close  bundle  of  the  cords  of  the  brachial  plexus  externally.  The  point  at  which 
the  vessel  is  tied  is  said  to  be  identical  with  that  at  which  it  is  ligated  through  the 
usual  incision  (Dawbarn). 


758  HUMAN    ANATOMY. 

The  collateral  circulation  after  ligation  of  the  third  portion  of  the  subclavian 
artery  is  carried  on  from  the  proximal  or  cardiac  side  of  the  ligature  by  (a)  the 
suprascapular  and  posterior  scapular  ;  (b)  the  aortic  intercostals,  the  superior  inter- 
costals,  and  the  internal  mammary  ;  and  (c)  numerous  subdivisions  of  subclavian 
branches  running  through  the  axilla,  anastomosing  respectively  with  (a)  the  sub- 
scapular, and  the  acromio-thoracic  ;  (6),  the  subscapular,  long  thoracic,  infrascap- 
ular,  and  dorsalis  scapula?  ;   (c)  the  axillary  trunk  or  its  branches. 

i.  The  Vertebral  Artery. — The  vertebral  artery  (a.  vertebralis)  (Figs.  695, 
704),  the  first  and  largest  branch  of  the  subclavian  artery,  is  destined  chiefly  for  the 
supply  of  the  spinal  cord  and  the  brain,  joining  with  the  internal  carotid  arteries  to 
form  the  remarkable  intracranial  anastomotic  circle  of  Willis.  In  view  of  its  peculiar 
course,  the  vertebral  artery  may  be  conveniently  divided  into  four  parts. 

The  first  portion  arises  from  the  upper  surface  of  the  first  part  of  the  sub- 
clavian artery,  opposite  the  interval  between  the  longus  colli  and  scalenus  anticus, 
and  courses  upward  and  somewhat  backward,  between  these  muscles  and  in  front 
of  the  transverse  process  of  the  seventh  cervical  vertebra,  to  the  foramen  in  the 
transverse  process  of  the  sixth  cervical  vertebra,  which  it  enters.  The  artery  is 
surrounded  by  a  plexus  of  sympathetic  nerve-fibres,  and  in  front  is  crossed  by  the 
inferior  thyroid  artery  and  covered  by  the  vertebral  and  internal  jugular  veins. 
The  second  portion  includes  the  ascent  of  the  artery  through  the  foramina  in  the 
transverse  process  of  the  upper  six  cervical  vertebrse,  surrounded  by  plexiform  net- 
works of  sympathetic  nerve-fibers  and  of  veins,  and  lying  in  front  of  the  trunks  of 
the  cervical  nerves.  As  the  artery  traverses  the  foramen  in  the  axis  it  abandons  its 
previous  almost  vertical  course  and  passes  upward  and  outward  to  reach  the  foramen 
in  the  atlas.  As  the  artery  emerges  from  this  opening,  between  the  suboccipital 
nerve  and  the  rectus  capitis  lateralis  muscle,  the  third  portion  begins,  which  winds 
horizontally  to  the  outer  side  and  back  of  the  superior  articular  surface  of  the  atlas 
to  enter  the  suboccipital  triangle  (Fig.  522)  where  the  artery  rests  in  the  vertebral 
groove  upon  the  posterior  arch  of  the  atlas,  separated  from  the  bone,  however,  by 
the  suboccipital  nerve.  The  artery  then  perforates  the  lower  border  of  the  posterior 
occipito-atlantoid  ligament  and  enters  the  spinal  canal.  The  fourth  portion  of 
the  artery  pierces  the  spinal  dura  mater,  passes  between  the  roots  of  the  hypoglossal 
nerve  and  the  dentate  ligament  and  enters  the  cranial  cavity  by  traversing  the  fora- 
men magnum.  Passing  forward  along  the  medulla  oblongata  and  gradually  inclin- 
ing towards  the  mid-ventral  line,  at  the  posterior  border  of  the  pons  the  vertebral 
artery  unites  with  its  fellow  of  the  opposite  side  to  form  the  basilar  artery  (a.  basi- 
laris),  which  extends  forward  along  the  median  line  of  the  pons  to  the  anterior 
border  of  that  structure,  where  it  terminates  by  dividing  into  the  two  posterior 
cerebral  arteries. 

Branches. — In  its  course  up  the  neck  the  vertebral  artery  gives  off,  opposite  each  inter- 
vertebral space  which  it  passes,  lateral  and  medial  branches  which  represent  the  original  seg- 
mental arteries  by  the  anastomoses  of  whose  branches  the  vertebral  was  formed  (page  721). 

(a)  The  lateral  or  muscular  branches  pass  to  the  muscles  of  the  neck  and  form  anasto- 
moses with  the  ascending  and  deep  cervical  branches  of  the  subclavian  and  with  the  arteria 
princeps  cervicis  of  the  occipital. 

(b)  The  medial  or  spinal  branches  (  rami  spinales)  pass  through  the  intervertebral  foramina 
into  the  spinal  canal,  accompanying  the  spinal  nerves,  and  are  distributed  to  the  bodies  of  the 
vertebrae  and  to  the  membranes  and  substance  of  the  spinal  cord.  Each  branch  gives  off  an 
ascending  and  a  descending  ramus  upon  the  posterior  surface  of  the  spinal  cord,  and  these, 
anastomosing  with  each  other  and  with  twigs  from  the  spinal  branches  of  the  intercostal,  lum- 
bar, and  lateral  sacral  arteries  below  and  with  the  posterior  spinal  branches  of  the  upper  part 
of  the  vertebral,  assist  in  the  formation  of  the  posterior  spinal  arteries,  which  run  the  entire 
length  of  the  spinal  cord  upon  its  posterior  surface  on  each  side  of  the  median  line.  Ante- 
riorly the  spinal  branches  of  the  vertebral  unite  with  the  anterior  spinal  artery,  reinforcing 
that  vessel. 

(c)  The  posterior  meningeal  artery  (ramus  meningeus)  arises  from  the  vertebral,  just  after 
it  has  pierced  the  dura  mater,  and  supplies  the  portion  of  that  membrane  which  lines  the  pos- 
terior portion  of  the  posterior  fossa  of  the  skull. 


THE    VERTEBRAL    ARTERY. 


759 


(d)  The  posterior  spinal  artery  (a  spinalis  posterior)  is  a  slender  vessel  which  anasto- 
moses below  with  the  posterior  ascending  ramus  of  the  uppermost  spinal  branch  from  the 
cervical    portion  of  the  vertebral  and  forms  the  uppermost  part  of  the  posterior  spinal  artery. 

(<?)  The  anterior  spinal  artery  (a.  spinalis  anterior),  much  larger  than  the  preceding,  arises 
from  the  inner  surface  of  the  vertebral,  a  short  distance  before  the  latter  unites  with  its  fellow 
to  form  the  basilar.  It  passes  downward  and  towards  the  ventral  median  line,  and  unites  with 
its  fellow  to  form  a  single  median  longitudinal  stem  which  extends  the  entire  length  of  the 
spinal  cord  along  the  line  of  the  anterior  median  fissure,  receiving  reinforcing  branches  from 
the  various  spinal  branches  of  the  vertebral,  intercostal,  lumbar,  and  lateral  sacral  arteries. 

(/)  The  posterior  inferior  cerebellar  artery  (a.  cerebelli  inferior  posterior)  arises  at  about  the 
same  level  as  the  preceding  vessel,  but  from  the  outer  surface  of  the  vertebral.  It  passes 
upward  over  the  sides  of  the  medulla  oblongata  to  supply  the  lower  surface  of  the  cerebellum, 


Fig.  702. 


Olfactory 
Anterior  cerebral 


Anterior  cerebral  £ 


Internal  carotid  artery 
Middle  cerebral  artery 

Antero  lateral  gang- 


Ociilom 

Posterior  cerebral  artery 

Sup.  cerebellar  artery  "js 

Basilar  artery 

Pons 


Anterior  spinal  artery 
Medulla  oblongata 

Posterior  inferior  eere- 

bellar  artery 
Vertebral  artery 


Inferior  surface  of  b 
Willis;  ape: 


giving  branches  to  the  medulla  and  to  the  choroid  plexus  of  the  fourth  ventricle  and  anasto- 
mosing with  the  superior  cerebellar  artery. 

From  the  basilar  artery,  (Fig.  702)  the  anterior  median  continuation  of  the  vertebrals. 

( .?")  Numerous  transverse  arteries  are  given  off  and  pass  outward  over  the  pons  to  supply 
that  structure  and  the  adjacent  portions  of  the  brain. 

(// )  The  internal  auditory  arteries  (aa.  auditivae  internae),  one  on  each  side,  are  additionally 
given  off,  and  accompany  the  auditory  nerve  through  the  internal  auditory  meatus  to  supply  the 
internal  ear. 

(z)  The  anterior  inferior  cerebellar  arteries  (aa.  cerebelli  inferiores  anteriores),  pass  out- 
ward on  either  side  over  the  surface  of  the  pons  to  the  lower  surface  of  the  anterior  portion  of  the 
cerebellum,  supplying  that  structure  and  anastomosing  with  the  superior  cerebellar  arteries. 

[j  )  The  superior  cerebellar  arteries  (aa.  cerebelli  superiores).  These  arise  from  the  basilar, 
immediately  behind  its  division  into  the  posterior  cerebral  arteries.  They  pass  outward  and 
backward  over  the  pons  and  the  crura  cerebri,  immediately  behind  the  roots  of  the  oculo-motor 


76o  HUMAN   ANATOMY. 

nerves,  and,  curving  upward  in  the  tentorial  fissure  almost  parallel  with  the  trochlear  nerves, 
are  distributed  to  the  upper  surface  of  the  cerebellum  and  anastomose  with  the  inferior  cere- 
bellar arteries. 

(k)  The  posterior  cerebral  arteries  (aa.  cerebri  posteriores)  (Fig.  702)  are  the  terminal 
branches  of  the  basilar.  From  its  origin  at  the  anterior  border  of  the  pons  each  artery  passes 
outward  and  slightly  forward,  curving  around  the  crus  cerebri,  immediately  in  front  of  the  root 
of  the  oculomotor  nerve,  which  separates  it  from  the  superior  cerebellar  artery.  It  then 
passes  upon  the  inferior  surface  of  the  cerebral  hemisphere,  where  it  breaks  up  into  cortical 
branches  which  ramify  over  the  surface  of  the  temporal  and  occipital  lobes,  anastomosing  with 
one  another  and  with  the  branches  of  the  anterior  and  middle  cerebrals.  The  cortical  branches 
(Fig.  700)  include  the  anterior  temporal,  which  supplies  the  anterior  parts  of  the  uncinate  and 
occipito-temporal  convolutions;  the  posterior  temporal,  distributed  to  the  posterior  part  of  the 
uncinate  and  the  occipito-temporal  convolutions  and  the  adjoining  gyrus  lingualis  ;  the  calca- 
tine,  the  continuation  of  the  posterior  cerebral  along  the  calcarine  fissure,  which  passes  to  the 
cuneus  and  the  gyrus  lingualis,  and  winds  to  the  outer  surface  ;  and  the parieto-occipital,  which 
follows  the  parieto-occipital  fissure  to  the  cuneus  and  the  quadrate  lobe. 

Immediately  at  their  origin  the  posterior  cerebrals  give  rise. to  a  number  of  small  central 
branches  (poslero-mesial  and  posterolateral  ganglionic)  which  dip  down  into  the  substance 
of  the  posterior  perforated  space  to  supply  the  optic  thalamus  and  the  adjacent  parts  of  the 
brain-stem,  and  somewhat  more  laterally  each  gives  off  a  posterior  choroidal  branch,  which 
passes  forward  in  the  transverse  fissure  to  the  choroid  plexus  of  the  third  ventricle.  Near 
where  it  passes  in  front  of  the  oculo-motor  nerve,  each  posterior  cerebral  receives  the  posterior 
communicating  artery  which  passes  back  to  it  from  the  internal  carotid,  and, more  laterally  it 
gives  off  some  small  branches  which  are  distributed  to  the  corpora  quadrigemina  and  the 
posterior  part  of  the  optic  thalamus. 

Variations. — The  vertebral  artery  may  arise  from  a  trunk  common  to  it  and  one  of  the 
other  branches  of  the  subclavian,  and  sometimes  it  arises  directly  from  the  arch  of  the  aorta  or, 
on  the  right  side,  from  the  innominate  artery  or  the  common  carotid.  It  may  traverse  a  foramen 
in  the  transverse  process  of  the  seventh  cervical  vertebra,  or  the  lowest  vertebrarterial  foramen 
through  which  it  passes  may  be  the  fifth,  fourth,  third,  or  even  the  second.  Very  rarely  the  two 
vertebrals  fail  to  unite  to  form  a  single  median  basilar,  that  artery  being  thus  represented  by  two 
longitudinal  trunks  united  by  transverse  anastomoses.  Occasionally  the  basilar  divides  into  two 
longitudinal  stems  which  reunite  farther  forward,  and  its  formation  by  the  fusion  of  two  parallel 
vessels  is  frequently  indicated  by  the  presence  in  its  interior  of  a  more  or  less  perfect  median 
sagittal  partition. 

The  vertebral  may  give  origin  to  an  inferior  thyroid  artery  or  to  the  deep  cervical,  and  oc- 
casionally, in  its  upper  part,  to  a  branch  which  anastomoses  with  the  occipital.  One  of  the  pos- 
terior inferior  cerebellar  arteries  may  be  wanting,  as  is  also  not  infrequently  the  case  with  one 
of  the  anterior  inferior  cerebellars,  or  these  latter  vessels  may  arise  from  the  posterior  cerebral. 
Occasionally  the  proximal  portion  of  one  or  other  of  the  posterior  cerebral  arteries  is  reduced  to 
a  mere  thread,  the  blood  reaching  the  terminal  portions  of  the  vessel  from  the  internal  carotid, 
through  the  posterior  communicating  artery. 

The  Circle  of  Willis.—  The  circle  or,  as  it  is  more  properly  called,  the 
polygon  of  Willis  (circulus  arteriosus)  is  a  continuous  anastomosis  at  the  base  of  the 
brain  (Fig.  702)  between  branches  of  the  internal  carotids  and  subclavians  (verte- 
brals). It  surrounds  the  posterior  perforated  space  and  the  floor  of  the  thalamen- 
cephalon.  Posteriorly  it  is  formed  by  the  proximal  portions  of  the  posterior  cerebral 
arteries,  at  the  sides  by  the  posterior  communicating  and  internal  carotid  arteries 
behind,  and  by  the  proximal  portions  of  the  anterior  cerebrals  in  front,  and  it  is 
completed  anteriorly  by  the  anterior  communicating  artery  which  unites  the  two 
anterior  cerebrals. 

By  means  of  these  connections  free  communication  is  established  at  the  base  of 
the  brain  between  the  two  internal  carotids  and  also  between  these  vessels  and  the 
vertebrals.  It  may  be  noted  that  a  further  communication  between  these  sets  of 
vessels  exists  upon  the  lateral  surfaces  of  the  cerebral  hemispheres  where  branches 
of  the  posterior  cerebral  arteries  anastomose  with  branches  of  both  the  middle  and 
anterior  cerebrals. 

In  marked  contrast  to  this  abundant  anastomosis  of  the  larger  vessels  upon  the 
surface  of  the  cerebrum  is  the  lack  of  direct  communication  between  the  small  vessels 
which  penetrate  its  substance.  These  are  all  terminal  or  end-arteries, — that  is, 
vessels  which  have  no  communication  with  others  except  through  the  general  capil- 
lary net-work,  which  offers  but  little  opportunity  for  the  establishment  of  an  efficient 
collateral  circulation  in  the  case  of  occlusion  of  one  of  the  arteries. 


PRACTICAL  CONSIDERATIONS:    VERTEBRAL  ARTERY.         761 

Practical  Considerations. — The  vertebral  artery  may  require  ligation  on 
account  of  wounds,  or  of  traumatic  aneurism  of  the  vessel  itself,  or  (in  addition  to  the 
ligation  of  other  vessels)  in  aortic  or  innominate  aneurism,  or  to  prevent  or  arrest 
secondary  hemorrhage  after  ligation  of  the  innominate. 

Aneurism — except  from  wound — is  excessively  rare,  the  vessel  being  well  sup- 
ported, first  between  the  scalenus  anticus  and  the  longus  colli  muscles  and  then  in  the 
bony  canal  in  the  transverse  processes.  Only  one  case  of  spontaneous  aneurism  of 
the  cervical  portion  of  the  artery  has  been  reported  (Hufschmidt). 

Traumatic  aneurism  is  more  frequent,  but,  on  account  of  the  vessel' s  depth,  is  rare. 

Paralysis  of  some  of  the  tongue  muscles  has  been  attributed  to  pressure  on  the 
hypoglossal  nerve  by  a  vertebral  aneurism  and  severe  occipital  headache  to  pressure 
on  the  suboccipital  nerve. 

Digital  compression  of  the  vertebral  is  possible  below  Chassaignac's  carotid 
tubercle  (q.v.), — i.e. ,  below  the  level  of  the  cricoid  cartilage,  if  pressure  is  made  in 
the  line  of  the  great  vessels.  Alternating  pressure  above  and  below  this  level  is  of 
great  diagnostic  value  in  distinguishing  the  source  of  the  bleeding,  or  of  the  supply  of 
blood  to  a  pulsating  tumor,  after  a  deep  wound  of  the  neck.  Pressure  along  the  line 
of  the  common  carotid  below  the  tubercle — i.e. ,  for  from  two  to  two  and  a  half  inches 
above  the  clavicle — will  usually  arrest  such  bleeding  and  pulsation,  no  matter  whether 
the  vertebral  or  either  of  the  carotids  is  involved.  Pressure  above  the  tubercle  will 
affect  only  the  carotids  and  their  branches,  but — except  in  the  presence  of  an  anomaly 
— will  leave  unchanged  a  flow  of  blood  or  an  aneurismal  pulsation  proceeding  from 
the  vertebral.  Furthermore,  as  in  one  of  the  not  infrequent  vertebral  variations 
(vide  supra),  the  artery  may  not  enter  its  vertebrarterial  foramen  until  it  reaches  the 
fifth,  fourth,  third,  or  even  the  second  transverse  process,  and  as,  in  such  a  case,  it 
would  be  effectually  compressed  when  pressure  was  applied  higher  than  the  carotid 
tubercle,  it  would  be  well  always  to  supplement  the  above  test  by  the  method  of 
"lateral  compression"  (Rouge), — i.e.,  by  pressing  together  between  the  thumb  and 
fingers  the  anterior  portion  of  the  relaxed  sterno-mastoid  muscle  and  the  carotid 
sheath  and  its  contents.  This  avoids  all  risk  of  coincident  compression  of  the  verte- 
bral, and  if  it  arrests  the  temporal  pulse  without  affecting  materially  the  bleeding  or 
the  pulsation  on  account  of  which  the  examination  is  made,  it  greatly  increases  the 
probability  that  the  latter  are  of  vertebral  origin  (Matas).  The  importance  of  making 
the  diagnosis  is  shown  by  the  fact  that  in  sixteen  out  of  thirty-six  cases  of  injuries  to 
the  vertebral  artery  the  common  carotid  had  been  ligated,  aggravating  the  hemor- 
rhage by  increasing  the  strain  on  the  vertebral  circulation  and,  of  course,  also  increas- 
ing the  risk  from  shock,  and  later  from  cerebral  complications  (Matas). 

Ligation  of  the  vertebral  has  been  effected  through  variously  placed  incisions  : 
1.  Low  in  the  neck,  one  of  three  inches  in  length  along  the  posterior  border  of  the 
sterno-mastoid  and  with  its  lower  end  at  the  clavicle,  with  division  of  some  of  the  clav- 
icular fibres  of  that  muscle  and  of  the  deep  fascia,  will  permit  the  recognition  of  the 
carotid  tubercle,  the  displacement  inward  of  the  sterno-mastoid  and  internal  jugular 
vein,  the  definition  of  the  space  between  the  scalenus  anticus  and  the  longus  colli, 
and  the  identification  of  the  artery  by  its  pulsation.  The  vertebral  vein  lies  in  front 
of  the  artery.  The  pleura,  the  inferior  thyroid  vessels,  the  phrenic  nerve,  and  on  the 
left  side  the  thoracic  duct  must  be  avoided.  The  fibres  of  the  cervical  sympathetic 
will  be  almost  necessarily  disturbed,  and  may  be  included  in  the  ligature.  Contrac- 
tion of  the  corresponding  pupil,  through  the  then  unopposed  action  of  the  oculo- 
motor, will  indicate  that  the  vessel  has  been  secured;  it  will  be  only  temporary. 

2.  For  a  ligation  in  continuity,  as  for  wound  or  aneurism  in  the  suboccipital 
region,  the  artery  may  be  much  more  easily  reached  through  an  incision  identical 
with  that  used  for  ligating  the  common  carotid  above  the  omo-hyoid  (page  732). 
When  the  carotid  sheath  is  well  exposed  it  is  drawn  outward  with  its  contents. 
Chassaignac's  tubercle  is  felt  (on  the  cricoid  level  or  one  centimetre  above  it)  and 
the  longus  colli  fibres  below,  overlying  the  artery,  are  seen.  A  transverse  division 
of  that  muscle  exposes  the  vertebral  artery  in  a  much  safer  region  than  below  and  at 
a  less  depth  (Dawbarn). 

The  collateral  circulation  is  very  freely  re-established  through  the  vessels  of  the 
circle  of  Willis. 


762 


HUMAN   ANATOMY. 
Fig.  703. 


I.  chondro-sterna!  articulation. 

Internal  mammary  artery 

I.  ant.  perf.  artery  of  left  side 

-Anterior  intercostal  arteries  of 
II.,  III..  IV.  and  V.  interspaces 


Cephali 
Humeral  branch  of 
acromial  thoracic  artery 


intercostal  artery 
Lower  branch  of  III.  aortic  intercostal 

Internal  intercostal  muscle 
Musculophrenic  artery 


Superior  epigastric  artery 


.Semilunar  fold  of  Douglas 


Superficial  external  pudic  artery 


Deep  external  pudic  artery 
Dorsalis  penis  a 


Internal  mammary  and  deep  epigastric  arteries. 


THE    INTERNAL    MAMMARY  ARTERY.  763 

2.  The  Internal  Mammary  Artery. — The  internal  mammary  artery  (a.  mam- 
raaria  interna)  (Figs.  692,  703)  arises  from  the  lower  surface  of  the  subclavian, 
usually  a  few  millimetres  lateral  to  the  origin  of  the  vertebral.  It  is  at  first  directed 
downward,  inward  and  slightly  forward  to  reach  the  posterior  surface  of  the  first 
costal  cartilage,  about  half-an-inch  lateral  to  the  border  of  the  sternum,  and  is  thence 
continued  vertically  downward  upon  the  inner  surface  of  the  anterior  thoracic  wall 
to  the  sixth  intercostal  space,  opposite  which  it  terminates  by  dividing  into  the 
musculo-phrenic  and  superior  epigastric  arteries. 

In  the  upper  part  of  its  course  the  artery  rests  upon  the  dome  of  the  pleura, 
crosses  the  posterior  surface  of  the  subclavian  vein,  and  is  crossed  obliquely  from 
above  downward  and  inward  by  the  phrenic  nerve.  In  the  thorax  it  is  in  con- 
tact behind  with  the  parietal  layer  of  the  pleura  as  far  down  as  the  third  costal  carti- 
lage, and  below  that  with  the  triangularis  sterni  muscle.  Anteriorly  it  rests  upon 
the  posterior  surfaces  of  the  upper  five  costal  cartilages,  and,  in  the  intercostal 
spaces,  upon  the  anterior  portions  of  the  internal  intercostal  muscles. 

Branches.— The  internal  mammary  gives  off  the  following  branches  :  ( 1 )  the  superior 
phrenic,  or  comes  nervi  phrenici,  (2)  the  mediastinal  branches.  (3)  the  anterior  intcrcostals, 
(4)  the  anterior  perforati7ig  branches  and  the  two  terminal  branches,  (5)  the  musculo-phrenic, 
and  (6)  the  superior  epigastric. 

(a)  The  superior  phrenic  artery  or  comes  nervi  phrenici  (a.  pericanliacoplirenica)  arises  from 
the  upper  part  of  the  internal  mammary,  and  is  a  long,  slender  branch  which  accompanies  the 
phrenic  nerve  to  the  diaphragm,  where  it  anastomoses  with  the  inferior  phrenic  and  musculo- 
phrenic vessels.  In  its  course  it  gives  off  numerous  small  branches  to  the  pleura  and  peri- 
cardium, which  anastomose  with  the  mediastinal  branches  and  the  bronchial  vessels  from  the 
thoracic  aorta. 

(b)  The  mediastinal  branches  (aa.  mediastinales  anteriores)  area  number  of  small  vessels 
which  are  distributed  to  the  sternum,  the  remains  of  the  thymus  gland,  the  pericardium,  and  the 
adipose  tissue  of  the  anterior  mediastinum. 

(c)  The  anterior  intercostal  arteries  (rami  intercostales)  arise  from  the  internal  mammary 
opposite  each  of  the  five  upper  intercostal  spaces,  and  are  two  in  number  for  each  space.  They 
pass  outward  and  slightly  downward  upon  the  posterior  surface  of  the  intercostal  muscles,  one 
along  the  upper  border  of  each  of  the  intercostal  spaces  concerned  and  the  other  along  its  lower 
border,  and  after  having  pierced  the  internal  intercostal  muscles,  they  terminate  by  becoming 
continuous  with  the  upper  and  lower  divisions  respectively  of  the  intercostal  branches  of  the 
superior  intercostal  artery  and  of  the  three  uppermost  aortic  intercostals.  These  branches  really 
represent  ventral  prolongations  of  the  aortic  intercostal  arteries  from  which  arose  the  upward 
and  downward  branches  whose  anastomosis  resulted  in  the  formation  of  the  internal  mammary 
(compare  page  84S). 

(d)  The  anterior  perforating  branches  (rami  perforantes)  arise  from  the  internal  mam- 
mary, one  opposite  each  intercostal  space  that  it  crosses,  and  represent  the  ventral  ends  of  the 
original  aortic  intercostal.  They  pierce  the  internal  intercostal  muscles,  the  anterior  intercostal 
membrane,  and  the  pectoralis  major,  to  supply  branches  to  the  sternum  and  to  the  integument. 
The  arteries  of  the  third  and  fourth  intercostal  spaces  are  larger  than  the  others  and  send 
branches  to  the  mammary  gland. 

(1?)  The  musculo-phrenic  artery  (a.  musculophrenica)  is  the  lateral  terminal  branch  of  the 
internal  mammary.  It  arises  opposite  the  anterior  end  of  the  sixth  intercostal  space  and  passes 
downward  and  outward  along  the  attachments  of  the  diaphragm  to  the  seventh  and  eighth  costal 
cartilages,  and  then,  piercing  the  diaphragm,  is  continued  onward  upon  the  under  surface  of  that 
muscle  to  the  level  of  the  tenth  or  eleventh  rib.  where  it  terminates  by  anastomosing  with  the 
inferior  phrenic  arteries  and  with  the  ascending  branch  of  the  deep  circumflex  iliac.  In  addition 
to  branches  to  the  diaphragm,  it  gives  off  two  anterior  intercostal  branches  opposite  each  of  the 
intercostal  spaces  that  it  crosses  as  far  down  as  the  ninth  ;  these  branches  have  the  same 
arrangement  and  significance  as  the  anterior  intercostal  branches  of  the  internal  mammary. 

(/)  The  superior  epigastric  artery  (a  cpigastrica  superior)  is  the  medial  terminal  branch 
of  the  internal  mammary.  It  continues  the  course  of  that  artery  downward,  and  passes  through 
the  diaphragm  in  the  interval  between  its  costal  and  sternal  origins  and  enters  the  sheath  of 
the  rectus  abdominis.  Lower  down  it  passes  into  the  substance  of  that  muscle,  where  it  termi- 
nates by  anastomosing  with  branches  of  the  deep  epigastric  artery. 

Anastomoses. — By  means  of  its  terminal  branches  the  internal  mammary 
makes  a  double  anastomosis  in  the  anterior  abdominal  walls  with  branches  from  the 
iliac  vessels,— -namely,  with  the  deep  epigastric  and  deep  circumflex  iliac  branches  of 


764  HUMAN   ANATOMY. 

the  external  iliac,  and  thus  connects  the  superior  and  inferior  portions  of  the  aortic 
system  of  vessels.  In  addition,  by  means  of  the  anterior  intercostals,  it  makes 
extensive  connections  with  the  thoracic  aorta  through  the  aortic  intercostals. 

Variations. — The  internal  mammary  may  arise  from  the  second  or  even  the  third  portion 
of  the  subclavian,  or  it  may  take  its  origin  from  the  thyroid  axis  or  from  the  superior  intercostal. 
In  its  course  down  the  anterior  thoracic  wall  it  varies  considerably  in  its  relation  to  the  lateral 
border  of  the  sternum,  its  distance  from  it  varying  in  different  cases  from  5-20  mm. 

Of  the  supernumerary  branches  to  which  it  may  give  rise,  one  of  the  most  important  is  the 
lateral  internal  mammary  (ramus  costalis  lateralis).  This  arises  from  the  internal  mammary 
above  the  first  rib,  or  in  some  cases  directly  from  the  subclavian,  and  descends  upon  the  inner 
surfaces  of  the  upper  four  or  six  ribs  and  the  intervening  intercostal  spaces,  parallel  with  the 
internal  mammary,  but  some  distance  lateral  to  it.  It  gives  off  branches  in  each  intercostal 
space,  which  anastomose  ventrally  with  the  anterior  intercostal  branches  of  the  internal 
mammary  and  dorsally  with  the  aortic  intercostals. 

Practical  Considerations. — The  internal  mammary  is  not  infrequently 
involved  in  stab  wounds  of  the  chest,  and  this  accident  may  be  suspected  if  after  such 
a  wound  there  are  threatening  symptoms  of  internal  hemorrhage  with  no  evidence  of 
injury  to  the  lung  itself.  The  bleeding  may  take  place  into  the  pleural  cavity,  causing 
the  characteristic  symptoms  of  haemothorax  (page  1866). 

Compression. — In  emergencies  the  bleeding  may  sometimes  be  arrested  by 
pushing  through  the  wound  into  the  intrathoracic  space  or  pleural  cavity  a  pouch  of 
antiseptic  gauze,  packing  it  with  other  strips  of  gauze  so  as  to  distend  the  portion 
within  the  ribs,  and  then  making  traction  upon  it  so  as  to  compress  the  wounded 
vessel  against  the  costal  cartilages  and  the  chest-wall. 

This  same  method  is  applicable  in  some  cases  of  intercostal  hemorrhage  when  it 
is  not  possible  or  desirable  to  approach  the  vessel  directly  in  its  groove  on  the  under 
and  inner  border  of  the  rib  by  incision  or  by  resection  of  a  portion  of  the  rib. 

Ligation. — In  some  cases  it  may  be  necessary  to  ligate  the  vessel  in  its  con- 
tinuity, although  its  free  anastomoses  make  it  very  desirable  to  find  and  tie  it  on  both 
sides  of  the  wound.  It  may  be  reached  through  an  incision  parallel  with  the  sternum 
and  a  half-inch  from  its  margin  or  through  a  transverse  incision  extending  outward 
along  an  intercostal  space.  In  either  event,  the  skin,  superficial  fascia,  sternal  fibres 
of  the  great  pectoral  muscle,  the  external  intercostal  aponeurosis  (connecting  the 
external  intercostal  muscle  with  the  sternum),  and  the  internal  intercostal  muscle 
must  be  divided.  The  artery  with  its  accompanying  veins  will  be  found  in  loose 
cellular  tissue  lying,  in  the  first  two  spaces,  upon  the  endothoracic  fascia,  which  sepa- 
rates it  from  the  pleura  ;  in  the  lower  spaces  the  vessel  rests  upon  the  triangularis 
sterni  muscle.  Below  the  third  or  fourth  space  resection  of  a  cartilage  will  usually 
be  necessary  for  the  purpose  of  gaining  room,  and  at  any  level  is  often  resorted  to 
to  permit  direct  access  to  the  bleeding  ends. 

3.  The  Superior  Intercostal  Artery. — The  superior  intercostal  artery 
(truncus  costocervicalis)  (Fig.  695)  arises  from  the  upper  posterior  surface  of  the 
subclavian  artery,  usually  about  opposite  the  origin  of  the  internal  mammary,  but  quite 
frequently,  and  especially  upon  the  right  side,  under  cover  of  the  scalenus  anticus. 
It  passes  at  first  upward  and  medially,  and  then  curves  backward  and  downward  over 
the  dome  of  the  pleura  to  reach  the  anterior  surface  of  the  neck  of  the  first  rib, 
where  it  divides  into  two  terminal  branches  which  pass  laterally  in  the  first  and 
second  intercostal  spaces.  As  it  enters  the  thorax,  the  superior  intercostal  lies  be- 
tween the  first  thoracic  sympathetic  ganglion  and  the  first  thoracic  spinal  nerve. 

Branches. — The  superior  intercostal  gives  rise  to  (1)  the  deep  cervical  artery,  and  to 
two  terminal  branches,  (2)  the  first  and  (3)  the  second  intercostal  arteries. 

(a)  The  deep  cervical  artery  (a.  cervicalis  profunda)  arises  just  as  the  superior  intercostal 
reaches  the  upper  border  of  the  neck  of  the  first  rib,  although  occasionally  it  takes  origin 
directly  from  the  subclavian.  It  is  directed  upward  and  backward,  passing  between  the  last 
cervical  and  first  thoracic  nerves  and  beneath  the  transverse  process  of  the  last  cervical  verte- 
bra, and  ascends  the  neck  between  the  complexus  and  the  semispinalis  colli,  to  which  it  sends 
branches.  It  anastomoses  with  branches  of  the  ascending  cervical,  vertebral,  and  princeps  cer- 
vicis  arteries,  and  gives  off  a  spinal  branch  which  passes  along  the  eighth  cervical  nerve  to  the 


THE   THYROID    AXIS. 


765 


spinal  canal,  where  it  anastomoses  upon  the  surface  of  the  spinal  cord  with  the  spinal  branches 
of  the  vertebral  and  of  the  intercostal  arteries. 

In  all  its  relations  the  deep  cervical  is  comparable  to  a  posterior  branch  of  an  intercostal 
artery,  and  is  to  be  regarded  as  the  posterior  branch  of  the  seventh  cervical  segmental  artery, 
which  is  the  subclavian. 

(6)  The  first  intercostal  artery  passes  outward  and  forward  in  the  first  intercostal  space, 
and  resembles  in  its  course  and  distribution  an  aortic  intercostal  (page  792). 

(c)  The  second  intercostal  artery  arises  at  the  bifurcation  of  the  superior  intercostal  and 
passes  downward  over  the  neck  of  the  second  rib  to  the  second  intercostal  space,  in  which  it 

Fig.  704. 


j  S       Common  carotid 
Suprascapular 


Inferior  thyroid 
Thyroid  axis 

Vertebral 
Thyroid  body 
Common  carotid 
Trachea 

Subclavian  artery 
Clavicular  facet 
of  sternum 


Biceps,  long  head 

Anterior  circumflex 
Biceps,  short  head 
Axillary  artery 
Posterior 


First  rib 
Superior  thoracic 

Alar  thoracic 
Pectoralis  minor, 


Deep  dissection  exposing  subclavian  and  axillary  arteries  and  their  branches. 

courses  similarly  to  an  aortic  intercostal  (page  792).  It  usually  receives  an  anastomosing  branch 
from  the  third  intercostal  artery  or  else  directly  from  the  thoracic  aorta,  and  may  be  replaced 
by  it. 

Variations.— The  superior  intercostal  may  arise  from  the  vertebral  artery  and  may  termi- 
nate in  the  first  intercostal  alone,  the  second  arising  from  the  third  or  from  the  thoracic  aorta. 
Anastomoses  occur  between  the  first  and  second  intercostals  and  the  arteria  aberrans  (Dage 
792),  when  that  vessel  is  present. 

4.  The  Thyroid  Axis. — The  thyroid  axis  (truncus  thyreocervicalis)  (Fig.  704) 
arises  from  the  upper  border  of  the  subclavian,  usually  just  medial  to  the  medial 
border  of  the  scalenus  anticus.      It  ascends  vertically  upward  for  from  2-10  mm., 


766  HUMAN    ANATOMY. 

and  terminates  by  dividing  into  three  branches  :   (i)   the  inferior  thyroid,  (2)  the 
superficial  cervical,  and  (3)  the  suprascapular. 

(a)  The  inferior  thyroid  artery  (a,  thyreoidea  inferior)  (Fig.  692)  is  the 
largest  of  the  branches  which  arise  from  the  thyroid  axis.  It  passes  at  first  verti- 
cally upward  to  about  the  level  of  the  transverse  process  of  the  sixth  cervical 
vertebra,  and  then  bends  medially.  It  passes  behind  the  common  carotid  artery, 
the  internal  jugular  vein,  and  the  pneumogastric  nerve,  either  behind  or  in  front  of 
the  recurrent  laryngeal  nerve  and  in  front  of  the  vertebral  artery,  and  finally  breaks 
up  into  branches  which  supply  the  lower  part  of  the  thyroid  gland  and  anastomose 
with  their  fellows  of  the  opposite  side  and  with  the  superior  thyroid  artery. 

Branches. — In  addition  to  these  terminal  branches,  the  inferior  thyroid  gives  origin  to  the 
following  arteries  : 

(aa)  Muscular  branches  to  the  scalenus  anticus  and  the  inferior  constrictor  of  the  pharynx. 

(66)  The  ascending  cervical  artery  (a.  cemcalis  ascendens)  frequently  arises  directly  from 
the  thyroid  axis  and  passes  vertically  upward,  parallel  to  the  phrenic  nerve,  in  the  interval  be- 
tween the  scalenus  anticus  and  the  rectus  capitis  anticus  major.  It  supplies  the  deep  muscles 
of  the  neck,  sends  branches  through  the  spinal  foramina  which  accompany  the  spinal  branches 
of  the  vertebral  artery,  and  anastomoses  with  the  vertebral,  the  occipital,  the  ascending  pharyn- 
geal, and  the  deep  cervical  arteries. 

(cc)  The  inferior  laryngeal  artery  (a.  laryngea  inferior)  passes  upward  in  the  groove  be- 
tween the  trachea  and  cesophagus  in  company  with  the  recurrent  laryngeal  nerve.  It  passes 
beneath  the  lower  border  of  the  inferior  constrictor  of  the  pharynx  and  enters  the  larynx,  to 
whose  mucous  membrane  and  muscles  it  is  distributed.  It  anastomoses  with  the  superior 
laryngeal  branch  of  the  superior  thyroid. 

Finally,  it  gives  off  small  branches  to  the  pharynx,  oesophagus,  and  trachea,  one  of  those 
to  the  last-named  structure  extending  down  upon  its  lateral  surface  to  anastomose  below  with 
the  bronchial  arteries. 

The  anastomoses  which  the  inferior  thyroid  makes  by  its  thyroid  branches  with  the  supe- 
rior thyroid  and  by  its  ascending  cervical  branch  with  the  occipital  constitute  important  connec- 
tions between  the  subclavian  and  carotid  systems  and  play  an  important  part  in  the  establish- 
ment of  the  collateral  circulation  after  ligation  of  the  common  carotid  artery. 

Variations. — The  thyroid  axis  occasionally  arises  under  cover  of  or  even  lateral  to  the 
scalenus  anticus,  and  it  may  be  entirely  wanting,  its  branches  arising  directly  from  the  subcla- 
vian. The  inferior  thyroid  may  be  absent  on  one  side  or  on  both,  and  its  size  varies  inversely 
to  the  development  of  its  fellow  of  the  opposite  side  or  to  that  of  the  superior  thyroid  arteries. 

Practical  Considerations. — The  inferior  thyroid  may  be  tied  for  a  wound  or 
during  the  operation  of  thyroidectomy.  It  has  been  frequently  tied,  in  conjunction 
with  the  superior  thyroid,  in  various  forms  of  goitre,  but  the  procedure  has  been 
abandoned.  It  may  be  reached  through  the  incision  for  tying  the  carotid  below  the 
omo-hyoid  (page  732).  The  sterno-mastoid  and  the  carotid  sheath  and  its  contents 
are  drawn  outward.  The  carotid  tubercle  being  found,  the  inferior  thyroid  should 
be  sought  for  at  a  slightly  lower  level, — opposite  the  body  of  the  sixth  cervical  ver- 
tebra or  about  the  level  of  the  omo-hyoid  crossing, — coming  out  from  behind  the 
sheath  of  the  great  vessels  and  running  in  front  of  the  vertebral  artery  obliquely 
upward  and  inward  towards  the  gland.  It  should  be  remembered  that  before  enter- 
ing the  gland  it  lies  for  a  short  distance  close  to  its  posterior  surface,  and  that  the 
recurrent  laryngeal  nerve  is  in  intimate  relation  to  this  part  of  the  vessel  or  to  its 
terminal  branches.  It  should  therefore  be  tied  in  the  fissure  between  the  cesophagus 
and  the  great  vessels,  as  close  to  the  carotid  sheath — i.e. ,  as  far  from  the  inferior 
angle  of  the  gland — as  possible,  to  avoid  inclusion  of  this  nerve.  The  middle  cer- 
vical ganglion  of  the  sympathetic,  the  phrenic  and  the  descendens  hypoglossi  nerves, 
and,  on  the  left  side,  the  thoracic  duct  should  be  carefully  avoided. 

(6)  The  superficial  cervical  artery  (a.  cervicalis  superficialis)  (Fig.  705) 
passes  almost  directly  laterally  from  the  thyroid  axis,  passing  in  front  of  the  scalenus 
anticus  and  then  across  the  lower  part  of  the  posterior  triangle  of  the  neck  at  a  level 
of  about  25  cm.  above  the  clavicle.  Arrived  at  the  anterior  border  of  the  trapezius, 
it  passes  beneath  that  muscle  and  breaks  up  into  ascending  and  descending  branches 
which  supply  the  trapezius,    the  levator  anguli  scapulae,  the  rhomboidei,  and  the 


THE   AXILLARY  ARTERY.  767 

splenii.  The  ascending  branches  anastomose  with  the  deep  and  ascending  cervical 
arteries,  and  with  the  princeps  cervicis  of  the  occipital  and  the  descending  branches 
with  the  suprascapular  and  transverse  cervical. 

(c)  The  suprascapular  artery  (a.  transversa  scapula)  (Fig.  704),  like  the 
superficial  cervical,  passes  almost  directly  laterally  across  the  lower  part  of  the  pos- 
terior triangle  of  the  neck.  It  lies,  however,  on  a  somewhat  lower  level  than,  and 
anterior  to,  the  superficial  cervical,  lying  usually  behind  the  clavicle,  in  front  of  the 
subclavian  artery,  and  resting  below  upon  the  subclavian  vein.  It  is  continued  later- 
ally beneath  the  trapezius,  to  which  it  sends  branches,  and,  having  reached  the 
upper  border  of  the  scapula,  it  passes  over  the  transverse  ligament  of  that  bone, 
or  occasionally  through  the  suprascapular  notch,  into  the  supraspinous  fossa.  Here 
it  gives  branches  to  the  supraspinatus  muscle,  and,  winding  around  the  lateral 
border  of  the  spine,  passes  through  the  scapular  notch  into  the  infraspinous  fossa, 
where  it  breaks  up  into  branches  supplying  the  infraspinatus  muscle  and  anastomos- 
ing abundantly  and  widely  with  the  branches  of  the  dorsal  scapular  artery. 

5.  The  Transverse  Cervical. — The  transverse  cervical  (a.  transversa  colli) 
is  the  only  branch  which  arises  from  the  third  portion  of  the  subclavian.  It  also  is 
directed  laterally,  parallel  with  the  superficial  cervical  and  suprascapular  arteries, 
about  midway  between  them,  but  on  a  much  deeper  level.  It  rests  upon  the  anterior 
surface  of  the  scalenus  medius  muscle,  and  upon  the  trunks  of  the  brachial  plexus, 
and,  passing  beneath  the  posterior  belly  of  the  omo-hyoid,  reaches  the  lower  portion 
of  the  levator  anguli  scapulae,  beneath  which  it  terminates  by  dividing  into  ascending 
and  posterior  scapular  branches. 

Branches. — In  addition  to  the  two  terminal  branches,  the  transverse  cervical  gives  off 
branches  to  the  trapezius,  the  supraspinatus,  and  the  levator  anguli  scapulas  muscles. 

(a)  The  ascending  terminal  branch  (ramus  ascendens)  passes  upward  to  supply  the  splenitis 
muscles,  and  forms  anastomoses  with  the  superficial  cervical. 

( b )  The  posterior  scapular  artery  ( ramus  descendens )  descends  along  the  entire  length  of  the 
vertebral  border  of  the  scapula  beneath  the  rhomboid  muscles.  It  supplies  these  muscles  and 
the  serratus  posticus  superior,  and  sends  branches  laterally  upon  both  the  dorsal  and  ventral 
surfaces  of  the  scapula,  supplying  the  infraspinatus  and  subscapular  muscles  and  anastomosing 
with  the  dorsal  scapular  and  subscapular  arteries 

Anastomoses. — The  anastomoses  which  the  suprascapular  and  transverse  cer- 
vical arteries  make  with  the  branches  of  the  subscapular  artery  from  the  axillary  are 
of  considerable  importance  in  the  establishment  of  the  collateral  circulation  from  the 
arm  after  ligation  of  the  third  portion  of  the  subclavian.  Additional  paths  which 
may  be  employed  for  the  same  purpose  are  afforded  by  the  anastomoses  which 
occur  between  the  thoracic  branches  of  the  axillary  artery  and  the  intercostal 
branches  of  the  superior  intercostal,  and  more  especially  the  perforating  branches  of 
the  internal  mammary. 

Variations.— Very  frequently  indeed  the  anastomosis  which  exists  between  the  ascending 
branch  of  the  transverse  and  the  superficial  cervical  develops  to  such  an  extent  that  it  forms 
the  principal  channel  by  which  the  blood  reaches  the  posterior  scapular  from  the  subclavian, 
and  in  such  cases  the  main  stem  of  the  transverse  cervical  disappears,  the  posterior  scapular 
then  becoming  a  terminal  branch  of  the  superficial  cervical.  This  arrangement  (Fig.  705)  is  of 
such  frequent  occurrence  that  it  is  regarded  as  the  normal  one  by  many  authors.  When  this  is 
done,  the  name,  transverse  cervical,  is  applied  to  the  main  stem  of  the  superficial  cervical,  the 
latter  term  being  retained  for  and  limited  to  the  ascending  branch  of  the  original  artery.  When 
this  arrangement  obtains,  there  is  no  branch  from  the  third  portion  of  the  subclavian  artery. 

THE   AXILLARY  ARTERY. 

The  axillary  artery  (a.  axillaris)  (Figs.  704,  705)  is  the  continuation  of  the 
subclavian  through  the  axillary  space.  It  begins  at  the  lower  border  of  the  first 
rib,  at  the  apex  of  the  axillary  space,  and  passes  downward  along  the  outer 
wall  of  the  space  to  the  lower  border  of  the  teres  major,  where  it  becomes  the 
brachial  artery.  When  the  arm  is  abducted  to  a  position  at  right  angles  to  the 
axis  of  the  trunk,  the  artery  has  an  almost  straight  course,  which  may  be  repre- 
sented by  a  line  drawn  from  the  middle  of  the  clavicle  to  a  point  midway  between 


768 


HUMAN    ANATOMY. 


the  two  condyles  of  the  humerus.  When,  however,  the  arm  hangs  vertically,  the 
vessel  is  slightly  curved,  the  convexity  of  the  curve  looking  upward  and  outward. 

Relations. — For  convenience  in  description  it  is  customary  to  regard  the  axil- 
lary artery  as  consisting  of  three  portions,  the  first  of  which  is  above  the  upper 
border  of  the  pectoralis  minor,  the  second  behind  that  muscle,  and  the  third  below 
its  lower  border. 

The  first  portion  of  die  artery  is  covered  anteriorly  by  the  clavicular  portion 
of  the  pectoralis  major,  by  the  costo-coracoid  membrane  which  separates  it  from  the 
cephalic  vein  and  the  branches  of  the  acromio-thoracic  artery,  and  by  the  subclavius 
muscle.     The  artery  is  enclosed  along  with  its  accompanying  vein  and  the  cords  of 


Pectoralis  major, 
Deltoid 


Long  thoracic 
Serratus  magnus 


Subclavian  and  axillary  arteries,  pectoralis  minor  still  in  place. 

the  brachial  plexus  in  a  downward  prolongation  of  the  cervical  fascia  known  as  the 
axillary  sheath,  and  rests  behind  upon  the  upper  serration  of  the  serratus  magnus  and 
upon  the  first  intercostal  space.  The  internal  anterior  thoracic  and  the  posterior 
thoracic  nerves  cross  it  obliquely  behind,  the  latter  nerve  intervening  between  _  it 
and  the  serratus  magnus.  Above,  at  the  outer  side,  afe  the  cords  of  the  brachial 
plexus  and  the  external  anterior  thoracic  nerve,  and  below  and  to  the  inner  side  is 
the  axillary  vein,  between  which  and  the  artery  is  the  internal  anterior  thoracic  nerve. 
In  its  second  portion  the  artery  is  covered  anteriorly  by  both  the  pectoralis 
major  and  the  pectoralis  minor.  Posteriorly  it  lies  in  contact  with  the  posterior  cord 
of  the  brachial  plexus,  and  is  separated  by  a  quantity  of  areolar  and  fatty  tissue  from 


PRACTICAL  CONSIDERATIONS:    AXILLARY  ARTERY.  769 

the  anterior  surface  of  the  subscapularis  muscle.  External  to  it  is  the  outer  cord  of  the 
brachial  plexus,  and  internally  the  inner  cord,  which  separates  it  from  the  axillary  vein. 
In  its  third  portion  the  artery  is  covered  in  its  upper  half  by  the  lower  part  of 
the  pectoralis  major,  but  in  its  lower  half  only  by  the  integument  and  the  superficial 
and  deep  fascise.  The  inner  head  of  the  median  nerve  passes  obliquely  across  its 
anterior  surface.  Posteriorly  it  is  in  relation  with  the  subscapularis,  latissimus  dorsi, 
and  teres  major,  in  that  order  from  above  downward,  a  considerable  amount  of  areolar 
tissue,  in  which  run  the  circumflex  and  musculo-spiral  nerves,  intervening,  however, 
between  the  artery  and  the  muscles.  To  the  outer  side  are  the  median  and  musculo- 
cutaneous nerves  and  the  coraco-brachialis  muscle,  while  internally  are  the  internal 
cutaneous  and  ulnar  nerves  and  the  axillary  vein. 

Branches. — Much  variation  occurs  in  the  arrangement  of  the  branches  of  the 
axillary  artery.  It  is  customary  to  recognize  seven  branches,  but  one  or  more  of 
them  is  frequently  absent  as  a  distinct  branch  arising  directly  from  the  artery. 
These  branches  are  arranged  as  follows  :  from  the  first  part  are  given  off  (1)  the 
superior  thoracic  and  (2)  the  acromial  thoracic  ;  from  the  second  part  (3)  the  lo?ig 
thoracic  and  (4)  the  alar  thoracic  ;  and  from  the  third  part  (5)  the  subscapular, 
(6)  the  anterior  circumflex,  and  (7)  the  posterior  circumflex. 

Variations. — As  stated  in  the  description  of  the  variations  of  the  subclavian,  the  axillary 
artery  may  be  represented  by  two  parallel  vessels  which  arise  from  the  first  portion  of  the  sub- 
clavian and  are  continued  below  into  the  radial  and  ulnar  arteries.  The  more  frequent  varia- 
tions, however,  concern  the  occurrence  of  additional  branches  from  the  axillary,  and  of  these 
there  may  be  mentioned  the  occurrence  of  the  superior  profunda,  normally  a  branch  of  the 
brachial,  but  not  infrequently  arising  from  the  axillary  in  common  with  the  subscapular. 

Practical  Considerations. — The  axillary  artery  may  require  to  be  ligated  on 
account  of  wounds,  of  rupture,  of  high  aneurism  of  the  brachial,  or,  rarely,  in  distal 
ligation  for  subclavian  aneurism. 

Wounds  of  the  axillary  are  not  uncommon  when  the  vulnerating  body — a  knife- 
blade,  a  bullet,  etc. — is  directed  from  within  outward,  the  artery  in  all  positions  of 
the  arm  maintaining  a  much  closer  relation  to  the  outer,  or  humeral,  wall  of  the 
axilla  than  to  the  inner,  or  thoracic,  wall,  which  is  therefore  known  as  the  wall  of 
safety.  It  is  always  well  in  such  cases  to  expose  the  artery  and  to  tie  both  ends,  as 
the  exact  source  of  the  bleeding  is  often  necessarily  in  doubt  and  the  free  anastomosis 
of  its  branches  is  likely  to  lead  to  secondary  hemorrhage  from  the  wound  if  the  vessel 
is  tied  in  continuity. 

Rupture  of  the  axillary  artery  has  occurred  in  a  considerable  number  of  cases  as 
an  accident  due  to  the  movements  employed  in  attempted  reduction  of  old  dislocations 
of  the  shoulder.  The  preponderance  of  arterial  as  compared  with  venous  rupture 
(twenty-six  out  of  twenty-eight  cases,  Stimson  ;  or  forty  out  of  forty -four,  Korte) 
is  striking,  the  greater  thinness  of  the  vein  and  its  attachment  to  the  costo-coracoid 
membrane — circumstances  that  would'  seem  to  favor  its  rupture — being  more  than 
counterbalanced  by  the  greater  frequency  and  extent  of  atheromatous  degeneration 
and  consequent  loss  of  elasticity  in  the  artery,  and  possibly  by  the  greater  liability 
of  the  latter  to  undergo  tension  during  the  movements  of  abduction,  elevation,  and 
circumduction  (which  are  those  chiefly  associated  with  the  accident  in  question),  and 
— as  the  outermost  or  rather  uppermost  vessel — to  contract  adhesion  to  the  displaced 
humeral  head. 

Aneurism  of  the  axillary  is  comparatively  frequent,  as  might  be  expected  from 
the  number,  variety,  and  range  of  the  movements  of  the  shoulder-joint,  during  which 
the  vessel  is  subjected  to  strains  and  to  a  variety  of  flexures.  It  is  more  common  on 
the  right  side  on  account  of  the  more  general  use  of  the  right  arm,  and  affects  oftenest 
the  third  portion  of  the  vessel,  or  that  least  supported  by  surrounding  structures  and 
most  subjected  to  changes  in  tension  and  position  and  to  certain  injuries,  as  those 
which  occur  during  luxation  of  the  shoulder  or  during  efforts  at  reduction  {vide 
supra).  On  account  of  the  looseness  of  the  tissue  in  which  it  lies,  such  an  aneurism 
rapidly  attains  a  large  size  and,  by  reason  of  the  minor  traumatisms  inflicted  during 
the  shoulder  movements,  is  especially  prone  to  inflammation. 

49 


77o 


HUMAN    ANATOMY. 


The  symptoms  are  (a)  swelling  showing  immediately  below  the  clavicle  (in 
Mohrenheim's  fossa)  and  pushing  that  bone  upward  if  the  first  portion  is  involved, 
or  pushing  the  pectoral  muscles  forward  if  the  aneurism  is  lower,  or  appearing  as  a 
pulsating  tumor  in  the  axilla  if  the  third  portion  is  involved  ;  (b)osdema  of  the  arm 
and  hand  from  pressure  on  the  axillary  vein  ;  (c)  pain  down  the  arm,  in  the  shoulder 
and  neck,  and  down  the  side  of  the  chest,  and  feebleness  and  limitation  of  shoulder 
and  arm  movements  from,  first,  spasm,  then  paresis  of  the  associated  muscles,  all  due 
to  pressure  on  the  brachial  plexus  and  its  branches. 

Digital  compression  of  the  axillary  artery  is  only  effectively  possible  in  the  lower 
part  of  the  third  portion,  where,  with  the  fingers  beneath  the  anterior  axillary  fold, 

Fig.  706. 


Cut  fibres 
of  pectoralis 

major    Clavicle    Subclavius    Axillary  artery 

Brachial  plexus 


First  intercostal  space 


Subclavian  vein     Pectoralis 
major,  cut 

Second  rib 

Dissection  showing  relations  of  axillary  artery  in  first  part  of  its  course. 

the  vessel,  if  the  effort  is  made  with  due  care  and  gentleness,  may  be  flattened  against 
the  humerus  just  within  the  edge  of  the  coraco-brachialis  and  biceps. 

Ligation  of  the  first  portion  may  be  effected  in  two  ways  :  1 .  With  the  arm 
abducted  to  a  right  angle,  an  incision  three  inches  long,  slightly  convex  downward, 
and  with  its  centre  about  an  inch  below  the  middle  of  the  clavicle,  is  made  through 
the  skin,  superficial  fascia,  and  platysma.  The  cephalic  vein  and  the  descending 
branch  of  the  acromial  thoracic  artery  will  be  seen,  just  beneath  the  fascia,  in  the 
groove  between  the  deltoid  and  greater  pectoral  muscles.  The  outer  clavicular  fibres 
of  the  pectoralis  major  are  then  divided  close  to  the  clavicle  ;  the  interpectoral  and 
axillary  fascia  and  some  loose  connective  tissue  are  broken  up  ;  the  upper  border  of 
the  pectoralis  minor  is  identified  and  traced  to  the  coracoid  process  ;  the  costo-cora- 
coid  membrane  is  cautiously  cut  through  by  a  vertical  incision  close  to  the  coracoid  ; 
the  artery  is  then  sought  for,  lying  between  the  brachial  plexus  of  nerves  externally  and. 


AXILLARY    ARTERY:    BRANCHES.  771 

the  vein  internally.  The  internal  anterior  thoracic  nerve  is  sometimes  seen  coming 
out  between  the  vein  and  the  artery.  The  arm  should  be  brought  to  the  side  to 
relieve  tension  on  the  vessels,  especially  the  vein,  which  in  that  position  will  be  least 
prominent.     The  needle  should  be  passed  from  within  and  below  outward  and  upward. 

2.  With  the  arm  abducted,  so  as  to  make  evident  the  fissure  between  the  sternal 
and  clavicular  portions  of  the  pectoralis  major,  an  oblique  incision  is  made  over  this 
space  and  will  usually  begin  about  a  half-inch  from  the  sterno-clavicular  joint.  The 
muscular  interspace  having  been  exposed,  its  sides  are  separated,  not  directly  back- 
ward, but  backward  and  upward  towards  the  clavicle.  The  arm  is  brought  to  the 
side  to  relax  the  pectoral  fibres.  The  pectoralis  minor  and  the  space  between  it  and 
the  clavicle  are  reachedt  and  if  the  latter  is  too  contracted,  the  muscle  may  be  divided 
close  to  the  coracoid  process.  The  artery  is  then  exposed  and  secured  as  in  the 
method  above  given. 

The  second  portion  is  not  formally  ligated,  but  may  have  a  ligature  applied  when- 
ever, as  in  the  last-mentioned  method,  the  lesser  pectoral  has  been  divided. 

Ligation  of  the  third  portion  of  the  subclavian  artery  is,  on  account  of  its  ease 
of  performance,  almost  invariably  preferred  to  any  of  these  operations. 

The  third  po7'tion  of  the  axillary  is  that  almost  always  selected  for  ligation  of 
that  vessel,  for  a  similar  reason. 

The  line  of  the  vessel,  the  arm  being  at  right  angles  to  the  trunk,  is  from  the 
junction  of  the  anterior  and  middle  thirds  of  the  summit  of  the  axilla  to  the  middle  of 
the  bend  of  the  arm  at  the  elbow.  This  line  will  be  found  to  follow  the  inner  margin 
of  the  coraco-brachialis  muscle,  the  prominence  of  which  may  be  seen  just  internal  to 
the  swell  of  the  biceps  where  it  emerges  from  beneath  the  anterior  axillary  fold.  An 
incision  is  made  on  this  line  through  the  skin  and  superficial  and  deep  fascise,  and  the 
fibres  of  the  coraco-brachialis  margin  are  exposed  and  cleared.  Internally  to  them 
lies  the  vessel,  the  median  and  musculo-cutaneous  nerves  external  to  it,  and  the  inter- 
nal cutaneous  nerve  and  axillary  vein  on  its  inner  side. 

The  needle  should  be  passed  from  within  outward. 

The  collateral  cii-culation  is  established  after  ligation  of  the  first  portion  above 
the  origin  of  the  acromial  thoracic  precisely  as  after  ligation  of  the  third  portion  of 
the  subclavian  (page  757).  After  ligation  of  the  third  portion  above  the  origin  of 
the  subscapular  the  anastomoses  take  place  between  (a)  the  intercostals,  long  thoracic, 
posterior  scapular,  and  suprascapular,  and  (&)  the  acromial  thoracic,  on  the  cardiac 
side  of  the  ligature  ;  and  («)  the  subscapular,  and  (3)  the  posterior  circumflex  on 
the  distal  side. 

When  the  vessel  has  been  tied  between  the  origins  of  the  subscapular  and  the 
two  circumflex  arteries — probably  the  point  of  election  (Taylor) — the  anastomoses 
occur  between  the  branches  of  the  axillary  and  those  of  the  thyroid  axis, — i.e. ,  the 
suprascapular  and  acromial  thoracic  above  and  the  posterior  circumflex  below.  Still 
lower, — i.e.,  below  the  circumflex  arteries — the  collateral  circulation  is  established 
just  as  after  ligation  of  the  brachial  above  the  superior  profunda  (q.v.~). 

1.  The    Superior    Thoracic    Artery. — The   superior  or  short  thoracic   (a.  «5ALAa>. 
thoracalis  suprema)  (Fig.  704)  arises  just  after  the  axillary  has  emerged  from  beneath 

the  subclavius  muscle,  and  is  directed  downward  and  forward  to  the  first  intercostal 
space,  the  muscles  of  which  it  supplies.  Not  infrequently  it  gives  off  a  branch  which 
supplies  the  muscles  of  the  second  intercostal  space  also.  Its  branches  anastomose 
with  those  of  the  internal  mammary  and  acromial  thoracic,  and  occasionally  its  place 
is  caken  by  a  branch  from  the  latter  vessel. 

2.  The  Acromial  Thoracic  Artery. — The  acromial  thoracic  (a.  thoraco- 
acromialis)  (Fig.  705)  is  a  very  constant  branch  which  arises  from  the  front  of  the 
axillary  artery,  a  short  distance  below  the  superior  thoracic.  It  is  directed  forward 
for  a  short  distance,  but  soon  divides  into  thoracic,  clavicular,  and  acromio-humeral 
branches. 

Branches. — (a)  The  thoracic  branches  (rami  pectorales)  pass  downward  and  forward  to  the 
side  of  the  thorax,  supplying  the  muscles  of  the  second  and  third,  and  sometimes  of  the  fourth 
and  fifth  intercostal  spaces,  and  also  giving  branches  to  the  pectoralis  major  and  the  pectoralis 
minor.     It  anastomoses  with  the  intercostal  arteries  and  the  superior  and  long  thoracics. 


772 


HUMAN    ANATOMY. 


(6)  The  clavicular  branch,  which  is  the  smallest  of  the  three,  passes  upward  to  supply  the 
subclavius  muscle,  and  anastomoses  with  the  suprascapular  artery. 

(c)  The  acromio-humeral  branch  passes  upward  and  outward  across  the  costo-coracoid 
membrane  and  over  the  coracoid  process  of  the  scapula,  and  then  divides  into  an  acromial  and 
a  humeral  branch.  The  former  (ramus  acromialis)  passes  upward  towards  the  acromial  process 
to  supply  the  deltoid  muscle,  while  the  latter  (ramus  deltoideus)  turns  downward  in  the  groove 
between  the  deltoid  and  the  clavicular  portion  of  the  pectoralis  major,  accompanying  the  cephalic 
vein.  It  sends  branches  to  the  two  adjacent  muscles  and  to  the  integument,  and  anastomoses 
with  the  anterior  circumflex  artery. 

3.  The  Long  Thoracic  Artery. — The  long  thoracic  (a.  thoracica  lateralis) 
(Fig.  704)  is  a  somewhat  inconstant  branch,  whose  place  is  very  frequently  taken  by 
the  thoracic  branch  of  the  acromial  thoracic  or  by  a  branch  from  the  subscapular.  It 
passes  downward  and  forward  upon  the  serratus  magnus,  sending  branches  to  that 
muscle,  the  pectoralis  minor,  and  the  muscles  of  the  third,  fourth,  and  fifth  intercostal 


Infraspinatus 
riceps,  scapular  head 


Arteries  of  posterior  aspect  of  shoulder. 


spaces.  It  also  sends  branches  to  the  mammary  gland  (rami  mammarii  externi), 
whence  it  has  been  termed  the  external  mammary  artery.  It  anastomoses  with  the 
thoracic  branch  of  the  acromial  thoracic,  with  the  subscapular  and  the  intercostals, 
and  with  the  perforating  branches  of  the  internal  mammary. 

4.  The  Alar  Thoracic  Artery. — The  alar  thoracic  (Fig.  704)  is  a  very  incon- 
stant small  branch  which  passes  to  the  fascia  and  lymphatic  glands  of  the  axillary 
space.  Its  place  may  be  taken  by  branches  from  the  subscapular,  the  long  thoracic, 
or  the  thoracic  branch  of  the  acromial  thoracic. 

5.  The  Subscapular  Artery. — The  subscapular  (a.  subscapularis)  (Fig. 
704)  is  the  largest  branch  of  the  axillary  and  arises  just  as  that  artery  crosses  the 
lower  border  of  the  subscapularis  muscle.  It  passes  downward  and  inward,  accom- 
panied by  the  long  subscapular  nerve,  along  the  lower  border  of  the,  subscapular 
muscle  as  far  as  the  lower  angle  of  the  scapula,  and  distributes  branches  through- 
out its  course  to  the  subscapularis  and  teres  major  and  to  the  latissimus  dorsi.  It 
also  gives  off — 


THE    BRACHIAL    ARTERY.  773 

(a)  Thoracic  branches  (rami  thoracodorsals) ,  which  supply  the  serratus  magnus  and  the 
muscles  of  some  of  the  intercostal  spaces,  and  not  far  from  its  origin  it  gives  off — 

(6)  The  dorsal  scapular  (a.  circumflex  scapulae).  This  vessel,  of  large  size,  winds  around 
the  axillary  border  of  the  scapula  in  the  triangular  space  bounded  by  the  teres  major,  the  teres 
minor,  and  the  long  head  of  the  triceps,  and  is  distributed  to  the  infraspinatus  and  the  teres 
minor. 

The  subscapular  artery  anastomoses  through  its  thoracic  branches  with  the  intercostals  and 
with  the  long  thoracic,  and  through  the  dorsal  scapular  with  the  suprascapular  and  posterior 
scapular  arteries. 

Variations. — The  subscapular  artery  varies  somewhat  in  its  origin.  Occasionally  it  springs 
from  the  second  portion  of  the  axillary,  and  may  also  arise  from  the  brachial.  Quite  frequently 
it  arises  from  a  trunk  common  to  it  and  one  or  other  or  both  circumflex  arteries,  and  the  supe- 
rior profunda  brachii,  normally  a  branch  of  the  brachial  artery,  may  also  arise  from  this  common 
trunk. 

The  subscapular  has  been  observed  to  give  rise  to  an  aberrant  artery  which  passes  down 
the  arm  and  either  unites  with  the  brachial  or  else  becomes  the  ulnar,  or  may  even  extend  to 
the  neighborhood  of  the  wrist,  where  it  unites  with  a  branch  of  the  anterior  interosseous  artery 
to  form  the  radial. 

6.  The  Anterior  Circumflex  Artery. — The  anterior  circumflex  (a.  circum- 
tlexa  humeri  anterior)  (Fig.  704)  is  the  smallest  of  the  three  branches  of  the  third 
portion  of  the  axillary,  and  arises  either  directly  from  the  artery  or  from  a  common 
trunk  with  the  posterior  circumflex  ;  more  rarely  it  arises  from  the  subscapular.  It 
passes  outward  beneath  the  coraco-brachialis  and  the  heads  of  the  biceps,  and  winds 
around  the  surgical  neck  of  the  humerus,  lying  close  to  the  bone.  Opposite  the 
bicipital  groove  it  gives  off  a  branch  which  ascends  along  the  groove  to  be  distributed 
to  the  capsule  of  the  shoulder-joint,  and  it  also  sends  branches  to  the  coraco- 
brachialis  and  biceps.  It  terminates  by  anastomosing  with  the  posterior  circumflex 
and  with  the  humeral  branch  of  the  acromial  thoracic. 

7.  The  Posterior  Circumflex  Artery. — The  posterior  circumflex  (a.  cir- 
cumflexa  humeri  posterior)  (Fig.  704)  arises  from  the  axillary,  almost  opposite  the 
anterior  circumflex,  or  from  a  common  trunk  with  that  vessel  or  with  the  subscap- 
ular. More  rarely  it  may  arise  from  the  upper  part  of  the  brachial  artery.  It  passes 
backward  and  outward  through  the  quadrilateral  space  bounded  by  the  subscapularis 
above,  the  teres  major  below,  the  long  head  of  the  triceps  internally,  and  the 
humerus  externally,  and  winds  around  the  posterior  surface  of  that  bone  at  the  level 
of  its  surgical  neck.  Passing  under  the  deltoid  muscle  externally,  it  divides  into 
a  number  of  branches,  most  of  which  pass  into  the  muscle  to  supply  it,  while  some 
pass  to  the  shoulder-joint.  It  anastomoses  with  the  acromial  branch  of  the  acromial 
thoracic,  with  the  anterior  circumflex,  and  with  the  superior  profunda  branch  of  the 
brachial. 

THE    BRACHIAL    ARTERY. 

The  brachial  artery  (a,  brachialis)  (Figs.  708,  709)  is  the  continuation  of  the 
axillary  down  the  arm.  It  begins  at  the  lower  border  of  the  teres  major  and  termi- 
nates a  little  below  the  bend  of  the  elbow  by  dividing  into  the  radial  and  ulnar 
arteries.  In  the  upper  part  of  its  course  the  vessel  lies  along  the  inner  side  of  the 
arm,  but  as  it  passes  downward  it  inclines  somewhat  outward,  so  that  in  its  lower 
part  it  is  on  the  anterior  surface  of  the  brachium.  Its  course  may  be  indicated  by  a 
line  drawn  from  the  junction  of  the  outer  and  middle  thirds  of  the  folds  of  the  axilla 
to  a  point  midway  between  the  condyles  of  the  humerus. 

Relations. — Anteriorly  the  brachial  artery  is  covered  throughout  the  greater 
part  of  its  course  by  only  the  deep  and  superficial  fascia;  and  the  integument.  About 
the  middle  of  its  length  it  is  crossed  obliquely,  from  without  inward,  by  the  median 
nerve,  and  at  the  bend  of  the  elbow  it  passes  beneath  the  aponeurotic  slip,  the 
so-called  bicipital  fascia  (lacertus  fibrosus)  from  the  tendon  of  the  biceps,  and  is 
separated  by  it  from  the  median  basilic  vein.  Posteriorly  it  rests  in  succession,  from 
above  downward,  upon  the  long  head  of  the  triceps,  the  inner  head  of  the  triceps, 
the  insertion  of  the  coraco-brachialis,  and  the  brachialis  anticus.  The  musculo-spiral 
nerve  and  the  superior  profunda  artery  pass  downward  and  inward  between  the 
vessel  and  the  long  head  of  the  triceps.     Externally  to  it,  above,  is  the  median  nerve 


774 


HUMAN    ANATOMY. 


and  the  coraco-brachialis  muscle,  and,  lower  down,  the  biceps  and  its  tendon. 
Internally  it  is  in  relation,  above,  with  the  ulnar,  internal  cutaneous,  and  lesser 
internal  cutaneous  nerves,  and,  in  its  lower  third,  with  the  median  nerve.  The  basilic 
vein  is  somewhat  superficial  to  it  and  to  its  inner  side. 

Two  venae  comites  accompany  the  artery,  lying  respectively  upon  its  inner  and 
outer  sides,  and  cross  branches  pass  between  the  two.  It  is  also  accompanied  by  two 
lymphatic  vessels  which  have  in  their  course  three  or  four  lymphatic  nodes,  usually 
of  small  size. 

Branches. — The  brachial  artery  gives  off  muscular  branches  to  the  biceps, 
coraco-brachialis,   brachialis  anticus,  triceps,  and  pronator  radii  teres,   and  a  small 


Fig.  70S. 


Humeral  branch  of 


■  condyle 
Olecranon 


Brachial  artery  in  relation  to  nerves  of  J 


nutrient  artery  for  the  humerus  (a.  nutriciae  humeri)  arises  either  directly  from  the 
brachial  or  from  one  of  its  muscular  branches  or  from  the  inferior  profunda.  It 
enters  the  nutrient  foramen  upon  the  inner  surface  of  the  shaft  of  the  humerus.  In 
addition,  there  arise  from  the  brachial  (1)  the  superior  prof imda,  (2)  the  inferior 
profunda,  and  (3)  the  anastomotica  magna. 

Variations. — The  variations  which  the  brachial  artery  presents  are  both  numerous  and 
important,  in  that  they  affect  materially  the  origin  of  the  two  terminal  branches,  the  radial 
and  ulnar. 

In  cases  in  which  there  is  a  well-developed  supracondyloid  process  on  the  humerus  (page 
268),  the  brachial  artery  accompanies  the  median  nerve  behind  it,  and  only  passes  upon  the  an- 
terior surface  of  the  arm  after  it  has  passed  it.  In  such  cases  there  generally  arises  from  the 
upper  part  of  the  brachial,  or  even  from  the  axillary,  a  vessel  which  descends  upon  the  anterior 
surface  of  the  arm,  lying  superficially  and  sending  branches  to  the  biceps  and  brachialis  anticus 


THE  BRACHIAL  ARTERY:  BRANCHES. 


775 


muscles.  This  has  been  variously  termed  the  vas  aberrans,  the  a.  brachialis  superficia/is,  or  the 
a.  radialis  superficial™,  and  it  appears  to  be  normally  present,  but  much  reduced  in  size  and 
included  among  the  muscular  branches. 

The  majority  of  the  modifications  of  the  brachial  artery  are  due  to  an  extraordinary  devel- 
opment of  the  superficial  brachial.  Thus  it  may  enlarge  and  become  continuous  below  with 
the  radial  artery,  giving  rise  to  a  condition  usually  termed  a  "  high"  origin  of  the  radial  ;  more 

Fig.  709. 


Humeral  branch  of  acromial  thoracic  artery  - 
Pectoralis  minor,  stump  ^ 


Biceps  and  coraco-brachialis,  stump 
Axillary  artery *» 


Anterior  circumflex  artery 
Tendon  of  long  head  of  biceps 


Insertion  of  pectoralis  major 
Deltoid 


Brachialis  anticus 
Tendon  of  biceps 


Iff)        Superior  profunda  artery 
Brachial  artery 


Inferior  profunda  artery 


Anastomotic  artery 


Origin  of  superficial  flexors 
—  Anterior  ulnar  recurrent  artery 
Posterior  ulnar  recurrent  artery 


■  Radial  artery 


Brachial  artery  and  its  branches. 


rarely  it  may  unite  with  the  ulnar  artery,  producing  a  "  high"  origin  for  that  vessel  ;  occasion- 
ally it  gives  rise  to  both  the  radial  and  ulnar,  the  true  brachial  being  continuous  below  with  the 
common  interosseous  ;  or,  finally,  it  may  unite  with  the  lower  part  of  the  brachial  artery  proper, 
the  portion  of  the  latter  between  the  origin  and  anastomosis  of  the  superficial  brachial  disap- 
pearing, so  that  what  is  termed  a  brachial  artery  is  formed,  which  passes  behind  instead  of  in 
front  of  the  median  nerve. 


776  HUMAN    ANATOMY. 

Comparative  anatomy  and  embryology  both  indicate  that  the  occurrence  of  a  well-devel- 
oped superficial  brachial,  continuous  below  with  the  radial,  is  the  primary  condition,  and  that 
the  origin  of  the  radial  as  a  terminal  branch  of  the  brachial  proper  is  a  secondary  condition, 
due  to  an  anastomosis  between  the  lower  part  of  the  original  superficial  stem  and  the  brachial 
and  to  the  subsequent  diminution  or  partial  obliteration  of  the  former  above  this  anastomosis 
(Fig.  748  E). 

Another  branch,  normally  present  but  usually  insignificant,  which  may  reach  an  extraor- 
dinary development,  is  the  a.  pliccz  cubiti  superficialis.  It  arises  from  the  lower  portion  of  the 
brachial  and,  passing  inward  and  downward  beneath  the  tendon  of  the  biceps,  is  distributed  to 
the  flexor  carpi  radialis  and  the  palmaris  longus.  When  abnormally  developed,  it  forms  what 
has  been  termed  the  accessory  ulnar  artery,  and  passes  down  the  forearm,  immediately  beneath 
the  deep  fascia  and  between  the  two  muscles  just  mentioned,  and  terminates  by  anasto- 
mosing with  the  ulnar,  or  in  some  cases  replaces  it  and  enters  into  the  formation  of  the  palmar 
arches. 

Supernumerary  branches  accessory  to  the  branches  usually  present  may  also  occur,  and, 
in  addition,  the  brachial  may  give  rise,  in  its  upper  part,  to  the  subscapular  and  the  posterior 
circumflex,  normally  branches  of  the  axillary  ;  in  its  lower  part,  to  the  radial  recurrent;  and,  at 
its  bifurcation,  to  the  interosseous  artery  or  to  the  median,  which  is  usually  a  branch  of  the 
interosseous. 

Practical  Considerations. — Spontaneous  aneurism  of  the  brachial  artery  is 
rare,  and  is  usually  associated  with  marked  arterio-sclerosis  or  with  cardiac  disease. 
Wounds  and  traumatic  aneurism  are  common,  though  lessened  in  frequency  by  the 
protected  position  of  the  upper  two-thirds  of  the  artery  on  the  inner  side  of  the  arm. 
Aneurism  has,  however,  followed  a  stab-wound  from  the  outer  side,  which,  after 
passing  through  the  biceps,  involved  the  vessel.  Arterio-venous  aneurism  just 
above  the  bend  of  the  elbow  was  formerly  often  met  with  as  a  result  of  the  accidental 
wounding  of  the  artery  during  phlebotomy  of  the  median  basilic  vein,  parallel  with 
the  vessel  at  that  point  and  separated  from  it  only  by  the  lacertus  fibrosus. 

The  line  of  the  artery  is  from  the  junction  of  the  anterior  and  middle  thirds  of 
the  axilla  to  the  middle  of  the  bend  of  the  elbow  when  the  arm  is  abducted  and  the 
forearm  extended  and  supinated. 

The  artery  in  the  upper  two-thirds  of  its  course  may  be  compj-essed  against  the 
inner  side  of  the  humerus  by  pressure  directed  outward  and  a  very  little  backward 
along  the  internal  border  of  the  coraco-brachialis  and  biceps.  This  muscular  border 
may  be  visible,  or  maybe  recognized  by  picking  it  up  between  the  thumb  and  finger. 
The  artery  may  be  overlapped  by  this  inner  edge  of  the  biceps,  especially  in  mus- 
cular subjects.  At  the  middle  of  the  arm,  over  the  insertion  of  the  coraco-brachialis 
into  the  flat  surface  above  the  beginning  of  the  internal  supracondyloid  ridge,  it  may 
most  easily  be  subjected  to  compression.  In  the  lower  third  the  pressure  must  be 
directed  backward,  as  the  humerus — separated  from  it  by  the  brachialis  anticus 
muscle — then  lies  behind  it. 

Ligation  of  the  vessel  at  its  upper  third  is  effected  through  an  incision  made 
along  the  inner  border  of  the  muscular  ridge  of  the  coraco-brachialis  muscle,  the 
fibres  of  which  may  with  advantage  be  exposed  and  identified.  Nothing  lies  between 
the  artery  and  the  muscle  except  the  median  nerve.  The  basilic  vein  is  to  the  inner 
side  of  the  vessel  and  may,  before  the  incision  is  made,  be  identified  and  avoided  by 
compression  of  the  axillary  vein  above.  The  ulnar  nerve  also  lies  to  the  inner  side. 
The  needle  may  be  passed  in  either  direction. 

In  ligation  at  the  middle  of  the  arm,  the  limb  should  be  abducted  with  the  elbow 
slightly  flexed,  and  should  be  supported  by  an  assistant.  If  the  arm  is  allowed  to 
rest  upon  a  flat  surface,  the  triceps  is  pushed  upward  and  may  be  mistaken  for 
the  biceps,  and  the  dissection  may  bring  into  view  the  inferior  profunda  artery 
and  the  ulnar  nerve  instead  of  the  brachial  and  the  median  (Heath).  It  is  well 
to  see  and  identify  the  innermost  fibres  of  the  biceps.  After  they  are  displaced 
outward,  the  median  nerve  (beginning  to  bear  to  the  inner  side)  should  be  separated 
from  the  vessel,  the  sheath  opened,  the  vense  comites  (the  inner  of  which  is  usually 
the  larger)  drawn  aside,  and  the  needle  passed  from  the  nerve.  Jacobson  calls 
attention  to  the  fact  that  this  usually  easy  ligation  may  be  difficult  when  the  artery 
is  concealed  by  the  median  nerve  at  the  point  at  which  it  is  sought,  and  when  its 
calibre  is  small  and  its  beat  feeble  as  the  result  of  hemorrhage.  The  median  nerve 
(from  transmitted  pulsation),  the  inferior  profunda  artery,  and  even  the  basilic  vein 
have  been  mistaken  for  the  brachial. 


THE    BRACHIAL    ARTERY:    BRANCHES.  777 

In  ligation  at  the  lower  third — -above  the  bend  of  the  elbow — the  inner  edge 
of  the  biceps  tendon  should  be  distinctly  recognized,  and  the  position  of  the 
superficial  veins,  especially  the  median  basilic,  should  be  made  apparent  by  com- 
pression above. 

The  incision  should  lie  just  within  the  edge  of  the  tendon  and  should  be  parallel 
with  it,  running  therefore  obliquely  from  within  outward.  It  will  usually  be  just 
outside  of  the  median  basilic  vein.  Its  centre  is  about  on  a  level  with  the  transverse 
fold  of  the  bend  of  the  elbow.  The  fibres  of  the  bicipital  fascia  are  divided  in  the 
line  of  the  skin  incision, — i.e. ,  diagonally,  as  they  run  downward  and  inward.  The 
needle  may  be  passed  from  within  outward  so  as  to  avoid  the  median  nerve,  which, 
however,  is  here  some  distance  to  the  inner  side.  In  all  ligations  of  the  brachial,  its 
frequent  variations  {vide  supra)  should  be  remembered,  and  the  possibility  of  the 
presence  of  a  "  vas  aberrans' '  or  an  "  accessory  ulnar' '  should  be  borne  in  mind,  as 
should  the  occasional  occurrence  of  a  muscular  slip  crossing  the  vessel  and  derived 
from  the  pectoralis  major  or  from  one  of  the  humeral  muscles. 

The  collateral  circulation  is  carried  on  after  ligation  above  the  superior  profunda 
between  the  ascending  or  recurrent  branches  of  that  vessel  and  the  circumflex  (espe- 
cially the  posterior)  and  subscapular  arteries.  After  ligation  below  the  origin  of  the 
inferior  profunda,  the  circulation  is  carried  on  through  the  anastomosis  between  the 
branches  of  the  profunda  from  above  and  those  of  the  anastomotic  and  the  recurrents 
from  the  radial,  ulnar,  and  posterior  interosseous  from  below.  After  ligation  below 
the  anastomotic,  the  branches  of  that  vessel,  as  well  as  those  of  the  profunda;,  carry 
the  blood  to  the  recurrents. 

1.  The  Superior  Profunda  Artery. — The  superior  profunda  (a.  profunda 
brachii)  (Fig.  709)  arises  from  the  upper  part  of  the  brachial,  on  its  posterior  surface, 
and  is  directed  downward  and  outward,  between  the  inner  and  long  heads  of  the 
triceps,  to  reach  the  posterior  surface  of  the  humerus.  Accompanied  by  the  musculo- 
spiral  nerve,  it  curves  around  to  the  outer  surface  of  the  bone,  lying  in  the  musculo- 
spiral  groove,  and  having  arrived  at  the  external  supracondylar  ridge,  it  pierces  the 
external  intermuscular  septum  and  continues  downward  between  the  brachialis  anticus 
and  the  supinator  longus,  to  terminate  by  anastomosing  in  front  of  the  external 
condyle  with  the  radial  recurrent  artery. 

Branches.— In  its  course  the  superior  profunda  gives  off  a  number  of  branches,  among 
which  may  be  mentioned  : 

(a)  A  deltoid  branch  (ramus  deltoideus),  which  passes  transversely  outward  to  the  inser- 
tion of  the  deltoid,  and  then  bends  upward  in  the  substance  of  that  muscle. 

(6)  Muscular  branches  to  the  triceps. 

(c)  A  median  collateral  branch  (a,  collateralis  media),  which  passes  downward  in  the  sub- 
stance of  the  inner  head  of  the  triceps  to  the  olecranon  process,  where  it  anastomoses  with  the 
posterior  ulnar  recurrent,  the  posterior  interosseous  recurrent,  and  the  anastomotica  magna. 

( d )  An  articular  branch,  which  is  given  off  from  the  lower  portion  of  the  artery,  just  before 
it  pierces  the  external  intermuscular  septum,  and  is  distributed  to  the  elbow-joint. 

(e)  Cutaneous  branches,  which  accompany  the  external  cutaneous  branches  of  the  mus- 
culo-spiral  nerve. 

Variations.— The  superior  profunda  occasionally  arises  from  the  axillary  artery  either 
directly  or  in  common  with  the  posterior  circumflex.  That  portion  of  its  main  stem  which 
traverses  the  musculo-spiral  groove  beyond  the  point  where  the  medial  collateral  branch  is  o-iven 
off  is  sometimes  termed  the  radial  collateral,  the  profunda  being  regarded  as  dividino-^after 
a  short  course,  into  the  two  collateral  branches.  The  deltoid  artery  not  infrequently"arises 
directly  from  the  brachial  artery  or  else  from  the  inferior  profunda. 

2.  The  Inferior  Profunda  Artery.— The  inferior  profunda  (a.  collateralis 
ulnaris  superior)  (  Fig.  709)  arises  from  the  inner  surface  of  the  brachial,  at  about  the 
middle  of  its  course.  It  passes  downward  and  backward,  accompanying  the  ulnar 
nerve,  through  the  internal  intermuscular  septum,  and  then  downward"  along  the 
anterior  surface  of  the  inner  head  of  the  triceps  to  the  back  of  the  internal  condyle, 
where  it  terminates  by  anastomosing  with  the  anastomotica  magna  and  the  posterior 
ulnar  recurrent.      It  gives  branches  to  the  triceps  and  to  the  brachialis  anticus. 


778  HUMAN    ANATOMY. 

3.  The  Anastomotica  Magna. — The  anastomotica  magna  (a.  collateral^ 
ulnaris  inferior)  (Fig.  709 J  arises  from  the  inner  surface  of  the  brachial  artery,  about 
4  cm.  ( 1  Y%  in. )  above  its  termination.  It  passes  inward  over  the  brachialis  anticus 
and  beneath  the  median  nerve,  and,  piercing  the  internal  intermuscular  septum,  winds 
around  the  inner  border  of  the  humerus  and  passes  transversely  across  its  posterior 
surface,  just  above  the  olecranal  fossa.  It  anastomoses  with  the  posterior  ulnar  recur- 
rent and  with  both  the  superior  and  inferior  profunda  arteries,  and  also,  by  means  of  a 
branch  given  off  before  it  pierces  the  intermuscular  septum,  with  the  anterior  ulnar 
recurrent. 

Anastomoses  around  the  Elbow. — The  brachial  artery  forms  rich  anasto- 
moses around  the  elbow-joint  with  both  the  radial  and  ulnar  arteries  by  means  of  its 
superior  and  inferior  profunda  branches  and  the  anastomotica  magna,  abundant 
opportunity  being  thus  afforded  for  a  collateral  circulation  to  the  forearm  after  ligation 
of  the  brachial.  Thus,  the  superior  profunda  anastomoses  in  front  of  the  external 
condyle  of  the  humerus  with  the  radial  recurrent,  and  its  medial  collateral  branch 
anastomoses  in  the  neighborhood  of  the  olecranon  process  with  the  posterior  inter- 
osseous and  the  posterior  ulnar  recurrents.  The  inferior  profunda  also  anastomoses 
with  the  posterior  ulnar  recurrent  behind  the  internal  condyle,  while  the  anastomotica 
magna  makes  connections  in  front  of  the  internal  condyle  with  the  anterior  ulnar 
recurrent;  and  posteriorly,  with  the  posterior  ulnar  and  the  posterior  interosseous 
recurrents. 

THE  ULNAR   ARTERY. 

The  ulnar  artery  (a.  ulnaris)  (  Figs.  710,  712)  is  the  larger  of  the  two  terminal 
branches  of  the  brachial.  It  arises  just  below  the  bend  of  the  elbow  and  passes  at 
first  distally  and  inward,  in  a  gentle  curve,  beneath  the  muscles  which  arise  from  the 
internal  condyle  of  the  humerus,  and  at  the  junction  of  the  upper  and  middle  thirds 
of  the  forearm  assumes  a  more  vertical  direction.  Arrived  at  the  wrist,  it  passes  over 
the  anterior  annular  ligament  to  the  radial  side  of  the  pisiform  bone  and  then  passes 
across  the  palmar  surface  of  the  hand,  forming  the  superficial  palmar  arch  (arcus 
volaris  superficialis),  whose  convexity  looks  distally,  and  terminates  opposite  the 
second  intermetacarpal  space  by  anastomosing  with  the  superficial  volar  branch  of 
the  radial. 

For  convenience  in  description,  the  ulnar  artery  may  be  regarded  as  consisting 
of  three  parts  :  ( 1  )  an  antebrachial  portion  extending  from  the  origin  of  the  vessel  to 
the  upper  border  of  the  anterior  annular  ligament,  (2)  a  carpal  portion  resting  upon 
the  annular  ligament,  and  (3)  a  palmar  portion  in  the  hand.  The  course  of  the 
lower  two-thirds  of  the  antibrachial  portion  may  be  represented  by  a  line  drawn  from 
the  front  of  the  internal  condyle  of  the  humerus  to  a  point  immediately  to  the  radial 
side  of  the  pisiform  bone,  while  the  course  of  the  upper  third  may  be  indicated  by  a 
line  drawn  from  the  middle  of  the  bend  of  the  elbow  to  meet  the  first  line  at  the 
junction  of  its  upper  and  middle  thirds.  The  superficial  palmar  arch  is  on  a  level 
with  the  thumb  when  the  digit  is  abducted  to  a  position  at  right  angles  to  the  axis 
of  the  hand. 

Relations. — The  antibrachial  portion  of  the  ulnar  in  its  upper  third  is  cov- 
ered by  the  pronator  radii  teres,  the  flexor  carpi  radialis,  the  palmaris  longus,  and  the 
flexor  sublimis  digitorum,  and  is  crossed  obliquely  by  the  median  nerve.  Behind,  it 
rests  upon  the  tendons  of  the  brachialis  anticus  and  upon  the  flexor  profundus  digi- 
torum. In  its  lower  two-thirds  it  is  overlapped  above  by  the  flexor  carpi  ulnaris,  but 
below  it  lies  entirely  to  the  radial  side  of  the  tendon  of  that  muscle,  and  is  covered 
only  by  the  skin  and  fascia?.  It  rests  upon  the  flexor  profundus  digitorum,  and  to  its 
radial  side  is  the  tendon  of  the  flexor  sublimis  digitorum,  while  to  its  ulnar  side  it  is  in 
close  relation  with  the  ulnar  nerve,  as  well  as  with  the  tendon  of  the  flexor  carpi  ulnaris. 

In  its  carpal  portion  it  rests  upon  the  anterior  surface  of  the  anterior  annular 
ligament,  immediately  to  the  radial  side  of  the  pisiform  bone,  and  is  covered  by  an 
expansion  from  the  tendon  of  the  flexor  carpi  ulnaris. 

The  palmar  portion,  in  the  upper  part  of  its  course,  is  covered  by  the  palmaris 
brevis  and  rests  upon  the  flexor  brevis  minimi  digiti.  The  superficial  palmar  arch, 
as  it  passes  radialwards,  is  crossed  successively  by  the  palmar  branch  of  the  ulnar 


THE    ULNAR   ARTERY. 


779 


nerve,  the  palmar  fascia,  and  the  palmar  branch  of  the  median  nerve.  It  rests  upon 
the  digital  branches  of  the  ulnar  nerve,  the  long  flexor  tendons,  and  the  digital 
branches  of  the  median  nerve. 

Branches. — From  its  antibrachial  portion  the  ulnar  artery  gives  rise  to 
numerous  muscular  branches  supplying  the  muscles  of  the  forearm,  and,  in  addition, 
to  ( i )  the  anterior  ulnar 

recurrent,    (2)   the  pos-  Fig.  710. 

terior  ulnar  recurrent, 
(3)  the  common  interos- 
seous,    (4)     a    nutrient 

branch,   (5)   the  poster-  ',,■     :        .i,*; 

ior  ulnar  carpal,  and 
(6)  the  anterior  ulnar 
carpal. 

From    the    carpal   superficial 

.  branch  of 

portion    arise    no 


sup.  profundi 


Musculo- 

spiral  nerve 


Radial  artery 
Flexor 

longus  pollicis 


branches    of    considera- 
ble size. 

From  the  palmar 
portion  arise  (7)  the 
superior  and  (  8  )  the  in- 
ferior deep  palmar 
branches  and  (9)  the 
digital  branches,  and,  in 

addition,    muscular       Brachio-radialis 

branches    to    superficial    Brachialis  amicus 
muscles  of  the  palm  and 
cutaneous  branches. 


Va  r  i  a  t  i  o  n  s . — From 
the  developmental  stand- 
point the  ulnar  artery  (page 
848),  although  earlier  in  its 
appearance  than  the  radial, 
is,  nevertheless,  preceded 
as  the  principal  artery  of 
the  forearm  by  two  others. 
In  the  most  primitive  con- 
dition the  brachial  is  con- 
tinued down  the  forearm, 
resting  upon  the  interos- 
seous membrane  and  giving 
rise  at  the  base  of  the  hand 
to  a  leash  of  digital 
branches.  Later  there  de- 
velops from  the  brachial  a 
second  artery,  which  passes 
distally  in  a  plane  superfi- 
cial to  the  original  vessel, 
accompanying  the  median 
nerve  through  the  interval 
between  the  flexor  sublimis 
digitorum  and  the  flexor 
profundus  digitorum.  This 
median  artery,  near  the 
wrist  anastomoses  with  the 
original  one,  and  the  latter 
then  begins  to  diminish  in 
size  and  separates  from  the 


Inferior  profunda  artery- 
Origin  of  superficial  flexors 
Median  nerve 
Brachial  artery 
Tendon  of  biceps 

Brachialis  anticus 
Origin  of  superficial  flexors 
Ant.  ulnar  recurrent  artery 
Post,  ulnar  recurrent  artery 

interosseous  artery 


Anterior 

carpal  artery. 


Radial  and  ulnar  arteries  :  superficial  dissection. 


median  above  the  point  of  its  anastomosis,  forming  the  anterior  interosseous  artery.  In  this 
condition  it  is  the  median  artery  which  gives  origin  to  the  digital  branches.  Finally,  the  ulnar 
arises  as  another  distinct  branch  from  the  brachial  and  gradually  supplants  the  median,  which 
now  appears  as  a  branch  of  the  interosseous  known  as  the  a.  comes  nervi  mediani. 

As  is  frequently  the  case  where  the  development  passes  through  a  series  of  well-marked 
stages,  its  arrest  may  occur  at  any  one  of  these,  and  consequently'an  anomaly  may  occur  in 
which  the  ulnar  artery  is  represented  only  by  some  muscular  branches,  its  place  being  taken  by 


780 


HUMAN    ANATOMY. 


a  persistent  median  or  interosseous  artery, — a  condition  of  which  indications  are  to  be  seen  in 
the  participation  of  the  interosseous  or  median  artery  in  the  formation  of  the  superficial  palmar 
arch  (page  7S5 J .  An  interesting  condition  in  which  indications  are  clearly  retained  of  all  the 
stages  which  the  forearm  arteries  pass  through  in  their  evolution  is  shown  in  Fig.  711.  An 
artery  which  is  the  superficial  brachial,  and  which  arose  from  the  axillary,  descends  the  arm 
parallel  to  the  brachial  proper  and  terminates  by  becoming  the  radial.  A  distinct  ulnar  has 
developed  and  the  anterior  interosseous  has  acquired  its  typical  arrangement,  but  there  is  a 
well-developed  median  artery  which  sends  a  strong  branch  across  to  the  radial  and  termi- 
nates by  anastomosing  with  the  superficial  palmar  branch  of  the  ulnar  to  form  the  superficial 
palmar  arch. 

Another  variation  may  occur  in  the  form  of  a  "high  origin"  of  the  ulnar  artery,  a  condi- 
tion which  results  from  the  anastomosis  of  the  superficial  brachial  artery  (page  774)  with  the 
ulnar.     In  such  cases  the  ulnar  frequently  passes  down  the  forearm  in  a  much  more  superficial 

position  than  usual,  passing  over,  instead  of  under, 
Fig.  711.  the  muscles    arising    from  the    internal   condyle. 

Such  a  superficial  course  may  also  be  followed  when 
the  artery  has  a  normal  origin,  and  occasionally 
it  passes  to  the  ulnar  border  of  the  forearm  be- 
tween the  palmaris  longus  and  the  flexor  sublimis 
digitorum. 

Practical  Considerations. — The  ul- 
nar artery  may  be  ligated  for  wound  or  for 
aneurism — of  which  it  is  rarely  the  subject — 
either  (1)  about  the  middle  of  the  forearm  or 
(2)  just  above  the  wrist. 

1.  With  the  forearm  supinated,  an  in- 
cision on  the  line  indicated  {vide  supra) 
through  the  skin  and  the  thin  deep  fascia 
should  expose  either  a  white  line — the  ten- 
dinous edge  of  the  flexor  carpi  ulnaris — which 
is  not  always  present  (Treves),  or  a  yellow 
(fatty)  interspace  (Farabeuf)  between  that 
muscle  and  the  flexor  sublimis  digitorum.  It 
is  best  marked  at  the  lower  part  of  the  wound. 
If  more  than  one  white  line  should  be  present, 
the  one  sought  for  would  be  nearer  the  ulnar 
margin  of  the  limb.  At  the  bottom  of  the 
interspace  thus  identified,  which  runs  oblique- 
ly inward  towards  the  ulna,  the  artery  will  be 
found  lying  on  the  flexor  profundus  digitorum, 
with  the  ulnar  nerve  to  its  inner  side.  It 
is  often  overlapped  by  the  inner  deep  edge 
of  the  flexor  sublimis,  so  that  that  muscle 
must  be  lifted  up  and  drawn  outward  before 
the  vessel  can  be  fully  exposed.  In  sepa- 
rating the  muscles  care  must  be  taken  not  to 
go  beyond  the  vessel  and  nerve — pushing 
them  to  the  radial  side — and  open  up  the  in- 
terspace between  the  flexor  carpi  ulnaris  and 
the  flexor  profundus.  The  space  between 
the  flexor  sublimis  and  the  palmaris  longus 
lies  to  the  outer  side  of  the  proper  space,  but  is  much  more  shallow  and  even 
less  well  marked. 

2.  Forcibly  extend  the  hand  so  as  to  bring  into  prominence  the  fleshy  swell  of 
the  flexor  sublimis  muscle  and  tendons,  just  to  the  ulnar  side  of  the  palmaris  longus 
(page  620).  The  incision,  beginning  about  one  inch  above  the  flexure  of  the  wrist, 
should  be  made  in  the  groove  to  the  inner  side  of  this  prominence,  and  is  immedi- 
ately in  line  with  the  pisiform  bone.  After  the  deep  fascia  is  divided  the  tendon  of 
the  flexor  carpi  ulnaris  is  seen  and,  after  it  is  relaxed  by  flexion  of  the  wrist,  is  drawn 
a  little  inward,  when  the  artery  will  be  found  still  lying  upon  the  flexor  profundus 
and  bound  to  it  by  a  definite  layer  of  fascia,  which  must  be  carefully  divided 
(Treves).      The  ulnar  nerve  lies  in  close  proximity  to  the  vessel  on  the  ulnar  side. 


Deep 
palmar 


Variation  of  arteries  of  left  a 
retention  of  developmental  < 


THE    ULNAR    ARTERY.  781 

The  venae  comites  of  the  ulnar  are  closely  attached  to  it,  but  may  be  included  in 
the  ligature  without  danger,  as  the  other  venous  channels  of  the  forearm  are  amply 
sufficient  to  carry  on  the  circulation. 

The  collateral  circulation  is  maintained  by  means  of  the  free  anastomosis  between 
the  branches  of  the  radial  and  ulnar,  those  of  the  interosseous  vessels,  and  those  of 
the  carpal  and  palmar  arches. 

1.  The  Anterior  Ulnar  Recurrent  Artery. — The  anterior  ulnar  recurrent 
(a.  recurrens  ulnaris  anterior  J  (Fig.  712J  arises  from  the  upper  part  of  the  ulnar 
artery,  frequently  in  common  with  the  posterior  recurrent.  It  is  usually  a  rather 
slender  branch,  and  is  directed  upward  in  the  groove  between  the  brachialis  anticus 
and  the  pronator  radii  teres  towards  the  internal  condyle,  over  which  it  terminates 
in  branches  which  anastomose  with  the  inferior  profunda  and  anastomotica  magna  of 
the  brachial.  It  gives  off  branches  to  the  neighboring  muscles  and  a  branch  to  the 
anterior  inner  portion  of  the  capsular  ligament  of  the  elbow-joint. 

2.  The  Posterior  Ulnar  Recurrent  Artery. — The  posterior  ulnar  recurrent 
(a.  recurrens  ulnaris  posterior)  (Fig.  712)  arises  either  immediately  below  the  anterior 
recurrent  or  by  a  common  trunk  with  it.  It  is  usually  considerably  larger  than  the 
anterior  recurrent,  and  passes  at  first  almost  horizontally  inward  and  backward  be- 
tween the  flexor  sublimis  and  the  flexor  profundus  digitorum,  and  then  bends  upward 
along  the  side  of  the  ulnar  nerve  between  the  two  heads  of  the  flexor  carpi  ulnaris.  It 
terminates  upon  the  posterior  surface  of  the  internal  condyle  of  the  humerus  in 
branches  which  anastomose  with  the  posterior  branch  of  the  inferior  profunda  and 
with  the  anastomotica  magna  of  the  brachial. 

It  gives  branches  to  the  adjacent  muscles,  to  the  skin,  and  to  the  posterior  in- 
ternal portion  of  the  capsule  of  the  elbow-joint. 

3.  The  Common  Interosseous  Artery. — The  common  interosseous  (a. 
interossea  communis)  (Fig.  710)  arises  from  the  outer  and  back  part  of  the  ulnar 
artery,  a  short  distance  below  the  posterior  ulnar  recurrent.  It  is  a  short,  stout 
trunk  which  passes  downward  and  outward  and,  having  reached  the  upper  border 
of  the  interosseous  ligament,  divides  into  the  anterior  and  posterior  interosseous 
arteries. 

Variations. — In  cases  in  which  a  superficial  brachial  artery  (page  774)  exists,  the  true 
brachial  may  be  directly  continuous  below  with  the  common  interosseous,  the  radial  and  ulnar 
arteries  arising  by  the  bifurcation  of  the  superficial  brachial.  Such  cases  form  what  are  usually 
termed  "  high"  origins  of  the  common  interosseous  ;  and,  since  the  superficial  brachial  may  arise 
from  the  axillary,  owing  to  the  anastomosis  with  it  of  the  aberrant  branch  of  that  artery,  the 
common  interosseous  may  also  appear  to  arise  from  the  axillary. 

In  cases  of  high  origin  of  the  radial  the  common  interosseous  may  arise  from  that  vessel 
and  give  origin  to  the  recurrent  ulnar  branches,  and  it  may  also  give  rise  to  these  branches  when 
it  has  a  normal  origin.  When  it  has  a  high  origin,  it  may  give  off  both  the  radial  and  ulnar 
recurrent  branches. 

a.  The  Anterior  Interosseous  Artery. — The  anterior  interosseous  (a.  inter- 
ossea volaris)  (Fig.  712)  descends  from  the  point  of  bifurcation  of  the  common  inter- 
osseous artery,  along  the  anterior  surface  of  the  interosseous  membrane,  between  the 
adjacent  edges  of  the  flexor  profundus  digitorum  and  the  flexor  longus  pollicis,  and 
divides  at  the  upper  border  of  the  pronator  quadratus  into  an  anterior  and  a  pos- 
terior terminal  branch  (Fig.  715). 

Branches. — In  addition  to  muscular  branches  to  the  adjacent  muscles  and  to  the  ex- 
tensor muscles  of  the  thumb, — the  latter  perforating  the  interosseous  membrane  to  reach  their 
destinations, — the  anterior  interosseous  artery  gives  off  a  number  of  more  or  less  important 
branches. 

{aa)  The  median  artery  (a.  comes  nervi  mediani)  arises  from  the  anterior  surface  of  the  ante- 
rior interosseous,  immediately  below  the  origin  of  that  vessel.  It  passes  forward  to  join  the 
median  nerve,  which  it  accompanies  down  the  arm,  and  in  whose  substance  it  is  frequently 
embedded.  It  continues  its  course  with  the  nerve  beneath  the  anterior  annular  ligament,  and, 
when  well  developed,  may  terminate  by  anastomosing  directly  with  the  superficial  palmar 
arch. 

(bb)  A  nutrient  branch  is  usually  given  off  to  the  radius  and  occasionally  also  to  the  ulna. 


782  HUMAN    ANATOMY. 

(cc)  The  anterior  terminal  branch  passes  either  over  or  beneath  the  pronator  quadratus, 
and  terminates  usually  by  anastomosing  with  branches  of  the  anterior  radial  and  ulnar  carpal 
and  with  the  palmar  recurrent  arteries.  Occasionally  it  anastomoses  directly  with  the  super- 
ficial palmar  arch. 

(dd )  The  posterior  terminal  branch  is  larger  than  the  anterior.  It  perforates  the  inter- 
osseous membrane,  anastomoses  with  the  posterior  interrosseous  artery,  and  terminates  in 
branches  which  anastomose  with  the  posterior  radial  and  ulnar  carpals  to  form  the  dorsal  carpal 
net-work. 

Variations. — The  anterior  interosseous  artery  may  arise  from  the  radial,  and  it  may  form 
anastomoses  below  with  the  radial  or  with  both  the  radial  and  ulnar.  The  relations  which  it 
sometimes  possesses  with  the  superficial  palmar  arch  will  be  considered  later, 

The  median  artery  is  occasionally  of  considerable  size  and  frequently  arises  from  the 
common  interosseous.  Its  relations  to  the  superficial  palmar  arch  will  also  be  considered 
later  (page  7S5J. 

b.  The  Posterior  Interosseous  Artery. — The  posterior  interosseous  (a.  inter- 
ossea  dorsalis)  (Fig.  715)  passes  backward  between  the  radius  and  ulna,  above  the 
concave  upper  margin  of  the  interrosseous  membrane.  It  thus  reaches  the  posterior 
portion  of  the  forearm  and  turns  abruptly  downward  between  the  superficial  and  deep 
layers  of  the  extensor  muscles,  and  breaks  up  at  the  wrist  into  branches  which  anas- 
tomose with  the  posterior  radial  and  ulnar  carpals  and  with  the  posterior  terminal 
branch  of  the  anterior  interosseous,  assisting  in  the  formation  of  the  dorsal  carpal 
net-work. 

Just  as  it  reaches  the  posterior  surface  of  the  forearm  it  gives  off  a  posterior 
interosseous  recurrent  branch  (a.  interossea  recurrens),  which  ascends  between  the 
anconeus  and  the  supinator  brevis  to  the  posterior  surface  of  the  external  condyle  of 
the  humerus,  where  it  anastomoses  with  the  superior  profunda  and  the  anastomotica 
magna.  In  its  course  down  the  arm  the  posterior  interosseous  gives  branches  to  the 
extensor  muscles,  and,  through  the  dorsal  carpal  net-work,  it  takes  part  in  the  supply 
of  the  articulations  of  the  wrist  and  carpus. 

4.  The  Ulnar  Nutrient  Artery. — The  nutrient  branch  for  the  ulna  arises 
from  the  upper  third  of  the  ulnar  artery  or  from  one  of  its  muscular  branches,  or 
from  the  anterior  interosseous.  It  enters  the  nutrient  foramen  situated  upon  the 
anterior  surface  of  the  bone,  near  its  outer  border. 

5.  The  Posterior  Ulnar  Carpal  Artery. — The  posterior  ulnar  carpal  (ramus 
carpeus  dorsalis)  (Fig.  715)  is  small.  It  arises  from  the  inner  surface  of  the  ulnar 
artery,  just  above  the  pisiform  bone,  and  winds  inward  beneath  the  tendon  of  the 
flexor  carpi  ulnaris  to  the  back  of  the  carpus,  where  it  anastomoses  with  the  posterior 
radial  carpal  and  the  posterior  interosseous  to  form  the  dorsal  carpal  net-work. 

6.  The  Anterior  Ulnar  Carpal  Artery. — The  anterior  ulnar  carpal  (ramus 
carpeus  volaris)  (Fig.  712)  is  also  small.  It  arises  from  the  ulnar  artery,  just  above 
the  upper  border  of  the  anterior  annular  ligament,  and  passes  outward  upon  the  car- 
pal ligaments  and  beneath  the  long  flexor  tendons  to  anastomose  with  the  anterior 
radial  carpal  and  anterior  interosseous  to  form  the  anterior  carpal  net-work. 

7  and  8.  The  Deep  Palmar  Arteries. — The  deep  palmar  branches  (rami 
volares  profundi)  (Fig.  712)  are  given  off  from  the  ulnar  artery,  just  after  it  has 
entered  the  palm.  The  superior  branch  arises  just  after  the  ulnar  artery  has  passed 
the  pisiform  bone,  and  passes  dorsally  in  the  interval  between  the  flexor  brevis  minimi 
digiti  and  the  abductor  minimi  digiti.  It  then  perforates  the  opponens  minimi  digiti. 
and  terminates  by  inosculating  with  the  deep  palmar  arch. 

The  inferior  branch  arises  just  as  the  ulnar  artery  is  bending  to  pass  trans- 
versely across  the  palm.  It  passes  dorsally  between  the  flexor  brevis  minimi  digiti 
and  the  long  flexor  tendon  for  the  little  finger,  and  terminates  by  inosculating  with 
the  deep  palmar  arch,  near  the  superior  branch. 

Frequently  one  or  other  of  these  branches,  more  usually  the  superior  one,  is 
lacking,  and  only  one  communication  between  the  ulnar  and  the  deep  palmar  arch 
exists.  In  their  passage  dorsally,  both  arteries  give  off  branches  to  the  adjacent 
muscles. 


THE    ULNAR    ARTERY. 


783 


Fig.  712. 


Musculo-spiral  nerve 

:ial  branch  of  superior  prof unda 

Tendon  of  biceps 

Radial  nerve. 
Posterior  interosseous  nerve 
Supinator  brevis 
Radial  recurrent  artery 

he'--    :■'■  ~- 
Radial  artery 
Posterior  interosseous  artery 
Pronator  radii  teres 

Extensor  carpi  radialis  longior ,.- 

Brachio-radialis  frlfl 


Flexor  longus  pollicis 


Anterior  radial  carpal  artery 


Radial  artery — 
Princeps  poll 

Branch  to  superficial  palmar  arch 


Radialis  indicis 


Median  nerve 

Brachial  artery 
Inferior  profunda  artery 


Brachialis  anticus 

Anterior  ulnar  recurrent  artery 


Posterior  ulnar  recurrent  artery 
Ulnar  artery 


Common  interosseous  artery 


rtery 
Anterior  interosseous  artery 

Anterior  interosseous  nerve 


Pronator  quadratus 


Anterior  ulnar  carpal  artery 
Wrist  joint 


Deep  branch  of  ulnar  artery 
Ulnar  artery 
Deep  palmar  arch 
Palmar  interosseous  arteries 


Deep  arteries  of  right  forearm  and  hand  ;   flexor  surface. 


784 


HUMAN    ANATOMY. 


9.  The  Digital  Arteries. — The  digital  branches  (aa.  digitales  volares  com- 
munes) arise  from  the  portion  of  the  ulnar  artery  which  passes  transversely  across 
the  palm  of  the  hand  and  is  termed  the  superficial  palmar  arch  (arcus  volaris 
superficialis).  They  are  four  in  number;  the  first  of  the  four,  starting  from  the 
ulnar  border  of  the  hand,  passes  obliquely  downward  and  inward  across  the  hypoth- 
enar  muscles  and  continues  distally  along  the  ulnar  border  of  the  little  finger.      The 

Fig.  713. 


Radial  artery 
Superficial  volar  artery 


Ulnar  artery 
Pisiform  bone 


Anterior  annular  ligament 
Deep  branch  of  ulnar  artery 
Digital  branches  of  median  11 


ni  digiti 


—  Digital  arteries 


Superficial  palmar  arch  and  its  branches. 

remaining  three  pass  downward  in  the  second,  third,  and  fourth  intermetacarpal 
spaces  resting  upon  the  lumbrical  muscles,  and,  just  before  reaching  the  clefts  of  the 
fingers,  each  receives  the  corresponding  palmar  interosseous  artery  and  then  divides 
into  two  branches,  the  collateral  digital  branches  ( aa.  digitales  volares  propriae). 
which  extend  distally  upon  the  adjacent  sides  of  the  neighboring  digits.  These  col- 
lateral branches  make  numerous  transverse  anastomoses  with  one  another,  especially 
in  the  neighborhood  of  the  interphalangeal  joints,  and  terminate  in  fine  branches 
which  supply  the  bulb  of  the  finger  and  the  bed  of  the  nail. 


Variations. — The  variations  of  the  digital  arteries  depend  principally  (1)  upon  their  pro- 
portional development  with  regard  to  the  palmar  interosseous  vessels  from  the  deep  palmar 
arch,  and  (2)  upon  variations  in  the  mode  of  formation  of  the  superficial  palmar  arch. 

The  palmar  interosseous  branches  of  the  radial  anastomose  with  the  digitals  just  before 
the  division  of  the  latter  into  their  collateral  branches,  and  if  the  interossea;  are  strongly  devel- 
oped, the  digitals  are  apt  to  be  of  small  calibre,  and  may  be  so  much  reduced  in  size  that  the 
collaterals  of  one  or  more  of  them  may  be  regarded  as  continuations  of  the  corresponding 
palmar  interossea;.  Conversely,  although  normally  the  supply  for  the  radial  side  of  the  index- 
finger  and  the  thumb  is  from  the  deep  palmar  arch,  yet  occasionally  it  is  derived  from  the 
superficial  arch,  the  princeps  pollicis  and  the  radialis  indicis,  the  branches  from  the  deep 
palmar  arch,  being  much  reduced  in  size. 


THE    RADIAL    ARTERY. 


735 


The  variations  in  the  formation  of  the  superficial  palmar  arch  are  frequent  and  numerous, 
and  may  be  grouped  in  two  classes  :  ( I )  those  in  which  additional  branches  from  the  forearm 
participate  in  the  formation  of  the  arch  or  replace  the  radial  in  its  composition,  and  (2)  those  in 
which  there  is  no  true  arch,  the  arteries  which  should  participate  in  its  formation,  and  in  some 
cases  additional  ones  also,  failing  to  anastomose  and  each  giving  rise  independently  to  a  certain 
number  of  digital  branches.  To  the  first  of  these  classes  belong  the  cases  in  which  the  median 
or  anterior  interosseous  artery  anastomoses  directly  with  the  arch  formed  by  the  superficial 
volar  and  the  ulnar,  and  also  those  in  which  the  superficial  volar  fails  to  reach  the  ulnar,  the  arch 
being  formed  by  the  union  of  the  latter  vessel  with  the  median  or  the  anterior  interosseous. 
And,  finally,  the  arch  may  be  formed  by  the  ulnar  artery  alone,  no  direct  communication  taking 
place  between  it  and  the  arteries  mentioned. 

In  the  second  class  of  cases— that  in  which  there  is  no  true  arch — the  ulnar  and  the  super- 
ficial volar,  on  reaching  the  palm,  divide  in  a  somewhat  fan-like  manner  to  give  rise  to  the  digital 
branches.     The  superficial  volar  may  contribute  the  fourth  digital,  as  well  as  the  vessels  to  the 

Fig.  714. 


Variations  of  palmar  arteries  replacing  superficial  arch.     (  Jaschtsckinski). 


thumb  and  radial  side  of  the  index  (Fig.  714,  A  ),  or  it  may  be  limited  to  the  latter  vessels,  all 
four  normal  digitals  being  derived  from  the  ulnar.  With  the  absence  of  the  arch  there  may  be 
associated  an  extra  development  of  the  median  artery,  which  continues  distally  into  the  palm 
as  the  fourth  digital  vessel,  the  remaining  digitals  and  the  radialis  indicis  and  princeps  pollicis 
being  supplied  by  the  ulnar  and  radial  respectively  (  C).  Or,  finally,  with  the  extra  development 
of  the  median  there  is  associated  an  absence,  more  or  less  complete,  of  the  superficial  volar, 
the  median  giving  off  the  branches  to  the  radial  digit  as  well  as  the  fourth  digital  (B ) . 


THE    RADIAL   ARTERY. 

The  radial  artery  (a.  radialis)  (Figs.  710,  712)  is  the  smaller  of  the  two  terminal 
branches  of  the  brachial,  whose  course  it  continues  downward  through  the  forearm. 
It  arises  at  the  bend  of  the  elbow  and  passes  down  the  outer  border  of  the  forearm  to 
the  level  of  the  styloid  process  of  the  radius,  where  it  bends  outward,  curving  around 
the  external  lateral  ligament  of  the  wrist.  It  then  extends  downward  over  the  pos- 
terior surface  of  the  trapezium  until  it  reaches  the  interval  between  the  first  and  second 
metacarpal  bones,  and  here  it  again  changes  its  direction  and  passes  forward  into  the 
palmar  surface  of  the  hand,  across  which  it  is  continued  inward  over  the  anterior  sur- 
faces of  the  second,  third,  and  fourth  metacarpals,  forming  what  is  termed  the  deep 
palmar  arch  (arcus  volaris  profundus).  It  terminates  opposite  the  proximal  part 
of  the  fourth  metacarpal  interspace  by  anastomosing  w^ith  the  deep  palmar  branch  of 
the  ulnar. 

In  accordance  with  its  position  with  reference  to  the  bony  axis  of  the  forearm 
and  hand,  the  radial  artery  may  be  regarded  as  consisting  of  three  parts.  In  its  first 
or  antibrachial  portion  it  is  preaxial  in  position,  in  the  second  qr  carpal  portion  it  is 
postaxial,  and  in  the  third  or  palmar  poiiioti  it  is  again  preaxial. 

Relations. — In  its  antibrachial  portion  the  course  of  the  artery  may  be  indi- 
cated by  a  line  drawn  from  a  point  midway  between  the  two  condyles  of  the  humerus 
to  a  point  about  1  cm.  internal  to  the  styloid  process  of  the  radius.  In  its  upper 
half  it  is  overlapped  in  front  by  the  inner  border  of  the  brachio-radialis  (supinator 
longus)  muscle,  but  lower  down  it  is  covered  only  by  the  deep  and  superficial  fasciae 

50 


786  HUMAN    ANATOMY. 

and  the  skin.  Posteriorly  it  rests  successively,  from  above  downward,  upon  the 
tendon  of  the  biceps,  the  supinator  brevis,  the  pronator  radii  teres,  the  radial  portion 
of  the  flexor  sublimis  digitorum,  the  flexor  longus  pollicis,  the  outer  border  of  the 
pronator  quadratus,  and  the  anterior  surface  of  the  lower  end  of  the  radius.  Inter- 
nally it  is  in  contact  with  the  pronator  radii  teres  in  its  upper  third,  and  throughout 
the  rest  of  its  course  with  the  outer  border  of  the  flexor  carpi  radialis.  Externally  it 
is  in  relation  throughout  its  entire  length  with  the  brachio-radialis,  and  in  the  middle 
third  of  its  course  it  is  in  contact  with  the  radial  nerve.  Two  venae  comites  accom- 
pany the  artery,  lying  to  its  inner  and  outer  sides. 

In  its  carpal  portion  the  radial  artery  rests  at  first  upon  the  external  lateral 
ligament  of  the  wrist  and  then  upon  the  posterior  surface  of  the  trapezium.  It  passes 
beneath,  successively,  the  tendons  of  the  extensor  ossis  metacarpi  pollicis,  the  exten- 
sor brevis  pollicis,  and  the  extensor  longus  pollicis,  being  covered  in  the  interval 
between  the  last  two  and  to  the  ulnar  side  of  the  extensor  longus  pollicis  only  by  the 
skin  and  fasciae,  in  which  are  some  branches  of  the  radial  nerve  and  tributaries  of  the 
radial  vein. 

In  its  palmar  portion,  as  it  passes  forward  through  the  proximal  portion  of  the 
first  intermetacarpal  space,  the  artery  lies  between  the  two  heads  of  the  first  dorsal 
interosseous  muscle.  It  then  bends  inward  beneath  the  oblique  head  of  the  adductor 
pollicis,  and,  either  penetrating  that  muscle  or  passing  between  it  and  the  transverse 
head  of  the  same  muscle,  is  continued  ulnarward  beneath  the  tendons  of  the  long 
flexors,  resting  upon  the  bases  of  the  metacarpal  bones  and  upon  the  interosseous 
muscles. 

Branches. — From  its  antibrachial  portion  the  radial  artery  gives  off  numer- 
ous muscular  branches  to  the  muscles  on  the  radial  side  of  the  forearm,  and,  in 
addition,  gives  origin  to  (i)  the  radial  recurrent,  (2)  the  anterior  radial  carpal,  and 
(3)  the  superficial  volar. 

From  its  carpal  portion  it  gives  rise  to  (4)  the  posterior  radial  carpal,  (5)  the 
dorsalis pollicis,  and  (6)  the  dorsalis  indicis. 

From  its  palmar  portion  its  branches  are  (7)  the  princeps  pollicis,  (8)  the 
palmar  interosseous  (of  which  there  are  three),  and  (9)  the  recurre?it  carpals. 

Variations. — The  high  origin  of  the  radial  has  already  been  considered  in  discussing  the 
variations  of  the  brachial  artery  (page  774).  It  is  the  last  of  the  forearm  arteries  to  be  devel- 
oped in  the  comparative  series,  and  its  relations  with  the  arterial  supply  to  the  hand  is  due  to 
secondary  anastomoses  which  it  makes  with  vessels  originally  present,  whereby  it  has  come  to 
give  origin  to  many  branches  formed  before  its  appearance.  Thus  the  dorsalis  indicis  and  the 
dorsalis  pollicis  are  primarily  digital  branches  from  the  dorsal  interosseous  artery  of  the  first 
intermetacarpal  space,  and  this  artery  arose  from  the  posterior  carpal  arch  and  has  become  a 
portion  of  the  radial  by  the  anastomosis  of  that  artery  with  the  arch.  Similarly  the  portion  of 
the  radial  which  passes  forward  between  the  first  and  second  metacarpals  to  join  the  deep 
palmar  arch  is  primarily  the  first  posterior  perforating  vessel,  which  has  secondarily  become  the 
deep  palmar  apparent  continuation  of  the  radial,  and  has  brought  that  vessel  into  direct  con- 
tinuity with  the  arch  and  given  it  the  branches  which  originally  arose  from  that  vessel. 

The  secondary  anastomoses  of  the  original  radial  with  pre-existing  vessels  have,  however, 
become  well  established,  and  variations  of  the  radial,  other  than  its  high  origin,  are  rather 
uncommon.  It  has  been  observed  to  terminate  in  an  anastomosis  with  an  enlarged  posterior 
carpal  arch,  or  in  the  lower  part  of  the  forearm  by  anastomosis  with  the  anterior  interosseous 
artery.  Its  absence  below  the  point  where  the  radial  recurrent  is  given  off  has  also  been  ob- 
served, its  territory  in  such  cases  being  supplied  bv  the  interosseous. 

Occasionally  it  passes  to  the  dorsal  surface  of  the  arm  much  higher  up  than  usual,  and  in 
such  cases  the  superficial  volar  branch  also  arises  at  a  much  higher  level  than  usual  and  passes 
downward  along  the  line  usually  occupied  by  the  radial  artery.  It  is  an  exceedingly  slender  ves- 
sel, and,  being  felt  at  the  place  where  the  pulse  is  usually  examined,  may  give  rise  to  erroneous 
conclusions  as  to  the  quality  of  that  phenomenon. 

Practical  Considerations. — The  radial  artery,  like  the  ulnar,  is  the  subject 
of  idiopathic  aneurism  only  with  great  rarity,  but  a  stab-wound  may  result  in  a  trau- 
matic aneurism,  or  may  necessitate  immediate  ligation  for  control  of  hemorrhage. 
The  vessel  may  be  tied  in  any  part  of  its  course. 

1.  At  the  upper  third  of  its  antibrachial  portion  it  is  reached  through  an  incision 
made  on  the  line  described  (vide  supra),  which,  after  the  deep  fascia  is  opened  up, 
should  disclose  the  interspace  between  the  brachio-radialis  and  the  pronator  radii 


THE    RADIAL   ARTERY.  787 

teres.  This  is  often  indicated  by  a  yellowish  (cellulo-fatty)  line.  The  fibres  of  the 
former  muscle  are  almost  parallel  with  the  long  axis  of  the  forearm  and  overlie  the 
artery  ;  those  of  the  latter  are  oblique  and  lie  close  to  the  inner  side  of  the  vessel. 
The  nerve  is  so  far  external  that  it  is  not  likely  to  be  seen.  The  artery,  with  its 
venae  comites,  lies  on  the  supinator  brevis. 

2.  At  the  middle  of  the  forearm  the  incision  is  made  on  the  same  line.  The 
same  relations  exist,  except  that  there  the  nerve  is  usually  very  near  to  the  outer  side 
of  the  artery,  which  now  lies  on  the  tendon  of  insertion  of  the  pronator  radii  teres. 

As  the  brachio-radialis  is  not  very  wide  at  this  part  (especially  if  the  artery  is 
sought  for  at  the  lower  end  of  the  middle  third),  it  is  very  easy  to  expose  the  outer 
instead  of  the  inner  border  of  the  muscle,  in  which  case  the  muscle  is  apt  to  be  drawn 
inward,  and  when  the  depths  of  the  wound  are  opened  up  the  radial  nerve  is  reached. 
This  is  the  common  error  of  beginners. 

The  tendon  of  the  brachio-radialis,  as  a  rule,  first  makes  its  appearance  at  the 
outer  border  of  the  muscle,  so  that  if  this  tendinous  edge  is  exposed  the  operator 
will  know  that  he  has  laid  bare  the  wrong  side  of  the  muscle.  The  inner  border 
of  the  latter  remains  muscular,  until  it  ends  somewhat  abruptly  in  the  tendon 
(Treves). 

3.  At  the  lower  third  the  incision  should  be  made  midway  between  the  tendon 
of  the  brachio-radialis  and  that  of  the  flexor  carpi  radialis,  the  latter  of  which  may 
be  made  prominent  by  strongly  extending  the  hand.  The  vessel  is  very  superficial, 
and  is  disclosed  as  soon  as  the  thin  fascia  is  divided.  The  nerve  has  left  the 
vessel  altogether  (at  a  level  of  from  three  inches  above  the  wrist  to  the  middle 
of  the  forearm)  and  has  passed  under  the  brachio-radialis  tendon  to  the  dorsum 
of  the  hand. 

4.  In  the  triangular  fossa  between  the  lower  end  of  the  radius  and  the  root  of  the 
thumb  (tadatiere  anatomique),  bounded  externally  by  the  tendon  of  the  extensor 
longus  pollicis,  internally  by  the  tendons  of  the  extensor  brevis  pollicis  and  the 
extensor  ossis  metacarpi  pollicis,  and  superiorly  by  the  inferior  margin  of  the  posterior 
annular  ligament  (Fig.  716),  the  radial  artery  may  occasionally  require  ligation  on 
account  of  wound  or  of  aneurism.  An  incision  one  inch  and  a  half  long  should  be 
made  obliquely  across  the  fossa,  observing  to  avoid  one  of  the  chief  radicles  of  the 
radial  vein,  which  lies  in  the  superficial  fascia  immediately  in  the  course  of  the  wound. 
After  opening  the  fascia,  and  displacing  some  loose  adipose  tissue,  the  artery  will  be 
reached  at  the  bottom  of  the  depression  between  the  tendons  of  the  thumb.  It  is 
desirable  to  avoid  opening  the  sheaths  of  the  tendons  or  the  joint  between  the  scaph- 
oid and  trapezium  ;  these  bones  together  with  the  base  of  the  first  metacarpal  form 
the  floor  of  the  space. 

The  collateral  circulation  after  ligation  of  the  radial  is  carried  on  as  after  ligation 
of  the  ulnar,  q.v. 

Wounds  of  a  palmar  or  cart>al  arch  are  apt  to  be  troublesome  on  account  of  the 
occasional  difficulty  in  finding  and  securing  both  ends  of  the  divided  vessel,  and 
because  of  the  very  free  anastomosis  between  the  palmar  and  carpal  arches  and  the 
interosseous  vessels,  which  leads  to  recurrent  hemorrhage,  even  after  ligation  of  both 
radial  and  ulnar.  Compression  over  the  wound,  firm  bandaging  from  the  finger-tips 
to  the  axilla,  and  elevation  of  the  limb,  are,  for  these  reasons,  the  methods  usually 
first  employed,  and  if  applied  thoroughly  will  generally  be  effectual.  Ligation  of  the 
brachial  is  indicated  when  these  have  failed,  on  account  of  the  necessity  for  getting 
above  the  interosseous  anastomotic  supply  {vide  sicpra). 

1.  The  Radial  Recurrent  Artery. — The  radial  recurrent  (a.  recurrens  radialis) 
(Fig.  712)  arises  from  the  outer  surface  of  the  radial,  shortly  below  its  origin.  It  is 
at  first  directed  downward  upon  the  surface  of  the  supinator  brevis,  but  quickly 
bends  upward  towards  the  external  condyle  of  the  humerus,  passing  between  the 
radial  and  posterior  interosseous  nerves  and  lying  beneath  the  supinator  longus. 
It  gives  numerous  branches  to  the  supinator  longus  and  brevis  and  to  the  extensor 
carpi  radialis  longior  and  the  extensor  carpi  radialis  brevior,  and  terminates  at  the 
external  condyle  by  anastomosing  with  the  superior  profunda  from  the  brachial 
artery. 


788 


HUMAN    ANATOMY. 


2.   The  Anterior  Radial  Carpal  Artery. — 
carpea  volaris)  (Fig.  712;  is  usually  a  small  branch 

Fig.  715. 


l Superior  profunda 

.rtery 
"Biachio-radialis 


Olecranon  process 


Interosseous 

recurrent  artery 
Extensor  carpi 

ulnaris,  cut 


Extensor 

longus  poll 


Extensor  ind 


The  anterior  radial  carpal  ("ramus 
which  arises  from  near  the  lower 
end  of  the  antibrachial  portion 
of  the  radial.  It  passes  inward 
beneath  the  flexor  tendons  at 
about  the  lower  border  of  the 
pronator  quadratus,  and  breaks 
up  into  a  number  of  small 
branches  which  anastomose 
with  branches  from  the  anterior 
ulnar  carpal,  the  anterior  inter- 
osseous, and  the  recurrent  car- 
pals  to  form  an  anterior  carpal 
net-work.  From  this  net -work 
branches  pass  to  the  wrist  and 
to  the  carpal  articulations. 

3.  The  Superficial  Vo- 
lar Artery. — The  superficial 
volar  (ramus  volaris  superfici- 
alis)  (Fig.  713)  arises  usually 
just  where  the  radial  bends  out- 
ward and  backward  to  reach  the 
posterior  surface  of  the  wrist. 
It  is  usually  rather  slender, 
although  variable  in  size,  and 
is  directed  downward,  passing 
either  over,  through,  or  beneath 
the  adductor  pollicis,  supplying 
that  and  the  other  muscles  of  the 
thenar  eminence,  and  terminates 
usually  by  anastomosing  with 
the  superficial  palmar  branch  of 
the  ulnar  to  form  the  superficial 
palmar  arch. 

Variations.  —  The  superficial 
volar  is  somewhat  variable  both  as 
to  size,  origin,  and  mode  of  termina- 
tion. It  occasionally  arises  high  up 
upon  the  radial,  and  in  such  cases 
that  vessel  passes  to  the  posterior 
surface  of  the  arm  at  a  much  higher 
level  than  usual.  Not  infrequently 
it  takes  no  part  in  the  formation  of 
the  superficial  palmar  arch,  and 
may  terminate  in  the  muscles  of 
the  thenar  eminence,  the  digital 
branches  being  all  given  off  by  the 
superficial  palmar  branch  of  the 
ulnar  ;  or,  on  the  contrary,  appear- 
ing as  a  well-developed  stem,  it 
may  divide  distally  into  from  one 
to  four  digital  arteries,  the  remain- 
ing ones  arising  directly  from  the 
superficial  palmar  branch  of  the 
ulnar  or  partly  from  that  and  partly 
from  the  median  artery  (page  784). 

4.  The  Posterior  Ra- 
dial   Carpal    Artery. — The 

posterior  radial  carpal    ( ramus 

carpeus  dorsalis)  (Fig.  715)  is  a 

small  branch  which  is  given  off  from  the  radial  just  as  that  vessel  passes  beneath  the 

tendon  of  the  extensor  ossis  metacarpi  pollicis.      It  passes  horizontally  inward  beneath 


Posterior  ulnar 

carpal  artery 


Dorsal 

interosseous 

arteries 


Arteries  of  extensor  surface  of  forearm  and  hand. 


THE    RADIAL    ARTERY. 


789 


the  tendons  of  the  extensor  carpi  radialis  longior  and  the  extensor  carpi  radialis 
brevior,  and  anastomoses,  either  directly  or  by  means  of  a  number  of  small  branches, 
with  the  posterior  ulnar  carpal,  forming  a  posterior  carpal  at ch  or  net-work. 

Branches. — From  the  posterior  carpal  arch  or  net-work  a  longitudinal  stem  passes  distally 
in  each  of  the  three  inner  intermetacarpal  spaces.  These  are  the  dorsal  interosseous  arteries 
(aa.  metacarpeae  dorsales).  At  the  upper  extremity  of  its  intermetacarpal  space  each  interosseous 
artery  receives  the  corresponding  perforating  branch  from  the  palmar  interosseous  artery, 
and  when  it  reaches  the  interval  between  the  bases  of  the  proximal  phalanges,  it  divides  into ' 
two  branches,  which  run  forward  upon  the  inner  and  outer  surfaces  respectively  of  the  proximal 
phalanges  of  the  adjacent  digits  and  terminate  in  small  branches  upon  these  phalanges. 

A  slender  branch,  which  arises  either  directly  from  the  dorsal  carpal  arch  or  from  the  in- 
terosseous artery  of  the  fourth  intermetacarpal  space,  passes  along  the  inner  border  of  the  metacar- 
pal and  proximal  phalanx  of  the  little  finger.     It  terminates  upon  the  proximal  phalanx  of  its  digit. 

Variations. — Considerable  variation  occurs  in  the  size  of  the  dorsal  interosseous  arteries. 
That  which  traverses  the  fourth  intermetacarpal  space  is  sometimes  wanting,  while  that  of  the 
second  space  is  sometimes  of  considerable  size  and  may  arise  directly  from  the  radial  artery. 
Occasionally  each  artery  undergoes  a  sudden  increase  of  calibre  at  the  point  where  it  is  joined 
by  the  perforating  branch  from  the  deep  palmar  arch,  and  may  appear  to  be  the  continuation  of 
the  perforating  branch.  Where  it  divides  into  its  two  terminal  branches,  each  interosseous  gives 
off  an  inferior  perforating  branch,  which  passes  forward  to  communicate  with  the  corresponding 
palmar  digital  artery  ;  but  these  perforating  branches  are  frequently  wanting,  with  the  exception 
of  that  given  off  from  the  artery  of  the  second  intermetacarpal  space. 

5.  The  Dorsalis  Pollicis  Artery. — The  dorsalis  pollicis  (Fig.  715)  is  a 
slender  artery  which  arises  from  the  radial  just  before  it  passes  beneath  the  tendon  of 
the  extensor  longus  pollicis.  It  passes  distally  along  the  dorsal  surface  of  the  first 
metacarpal  and  terminates  upon  the  dorsum  of  the  first  phalanx  of  the  thumb. 

6.  The  Dorsalis  Indicis  Artery. — The  dorsalis  indicis  (Fig.  715)  arises 
from  the  radial  just  as  it  passes  between  the  two  heads  of  the  first  dorsal  interosseous 
muscle  to  enter  the  palm  of  the  hand.  It  passes  distally  along  the  radial  border  of  the 
second  metacarpal,  resting  upon  the  first  dorsal  interosseous  muscle,  and  terminates 


Extensor  carpi  radialis  longior 
Lower  extremity  of  radii 
Radial  artery 


Fig.  716. 


Extensor  ossis  metacarpi  poll 

Extensor  brevis  poll 


Dissection  showing  relation  of  radial  artery  to  extensor  tendo 


upon  the  first  phalanx  of  the  index-finger.     It  frequently  gives  off  a  small  branch  which 
passes  along  the  inner  border  of  the  metacarpal  and  first  phalanx  of  the  thumb. 

Variations— The  dorsalis  indicis,  together  with  the  carpal,  portion  of  the  radial  distal  to 
the  point  at  which  the  posterior  radial  carpal  is  given  off,  represents  the  dorsal  interosseous 
artery  of  the  first  intermetacarpal  space.  The  branch  to  the  inner  border  of  the  thumb  repre- 
sents one  of  the  terminal  branches  of  that  artery,  and  frequently  arises  directly  from  the  radial 
opposite  the  main  stem  of  the  dorsalis  indicis. 

7.  The  Princeps  Pollicis  Artery. — The  a.  princeps  pollicis  (Fig.  717)  arises 
from  the  radial  just  as  it  emerges  from  between  the  two  heads  of  the  first  dorsal  inter- 
osseous muscle  and  is  bending  horizontally  inward  to  form  the  deep  palmar  arch.  The 
artery  passes  directly  distally,  resting  upon  the  palmar  surface  of  the  first  dorsal  inter- 
osseous muscle  and  being  covered  by  the  adductor  pollicis.      While  still  beneath  the 


790 


HUMAN   ANATOMY. 


caput  obliquum  of  the  adductor,  the  vessel  frequently  divides  into  two  branches,  one  of 
which  is  continued  distally  along  the  radial  border  of  the  index-finger,  forming  what 
has  been  termed  the  a.  radialis  indicis  (a.  volaris  indicis  radialis),  while  the  other 
extends  along  the  first  metacarpal  and,  passing  between  the  two  heads  of  the  adductor, 
divides  beneath  the  tendon  of  the  flexor  longus  pollicis  into  two  branches,  which 
pass  distally  along  the  palmar  surface  of  the  thumb,  one  along  the  inner  and  the 
other  along  the  outer  border,  anastomosing  with  the  branches  of  the  dorsalis  pollicis. 

Variations. — The  a.  princeps  pollicis  is  in  reality  the  palmar  interosseous  artery  of  the  first 
intermetacarpal  space,  and,  when  developed  as  described,  corresponds  in  the  arrangement  of 
its  branches  with  the  dorsalis  indicis,  together  with  the  dorsalis  pollicis.  Frequently,  however, 
the  branch  to  the  radial  border  of  the  index-finger  is  lacking,  or,  on  the  other  hand,  it  may  be 
well  developed  and  arise  directly  from  the  deep  palmar  arch,  or  sometimes  both  it  and  the 
princeps  pollicis  are  derived  from  the  superficial  palmar  arch  (page  784). 

8.  The  Palmar  Interosseous  Arteries. — The  palmar  interosseous  arteries 
(aa,  metacarpeae  volares )  are  three  in  number,  and  arise  from  the  deep  palmar  arch  as 

Fig.  .717- 


Anterior  carpal  branch 
Superficial  volar 

Posterior  carpal  bi 

Metacarpal 
Dorsales  poll 
Radial  artery 

Princeps  pollicis^ ^HE 

Radialis  ind 

Dorsalis  ind 

Branch  from  radialis 

dicis  for  superficial  a 


Ulnar  artery 

Anterior  carpal  branch 


osterior  carpal  branch 


Posterior  carpal  branch 


Posterior  carpal  arch 

Deep  branch  of  ulnar 
A  perforating  branch  of 

deep  palmar  arch 
Superficial  palmar  arch 
Dorsal  interosseous 
rteries 
interosseous 
arteries 


Digital  arteries 


Semidiagrammatic  reconstruction  of  right  hand,  viewed  from  palm,  showing  relations  of  arteries 
to  surface  and  to  bones;  vessels  on  dorsal  surface  are  represented  in  outline. 

it  crosses  the  second,  third,  and  fourth  intermetacarpal  spaces.      Each  artery  passes 
distally   in  its   intermetacarpal   space,    resting  upon  the  interosseous   muscles,    and 


THE   THORACIC   AORTA.  791 

nates  by  anastomosing  with  the  corresponding  digital  artery  from  the  superficial  palmar 
arch  just  before  the  digital  divides  into  its  two  terminal  branches.  Immediately  at 
its  origin  each  palmar  interosseous  gives  off  a  perforating  branch  (  ramus  perforans ) 
which  passes  dorsally  between  the  adjacent  metacarpals  to  communicate  directly  with 
'  the  corresponding  dorsal  interosseous  artery. 

Variations. — The  palmar  interosseous  arteries  vary  considerably  in  size,  according  as  the 
digital  branches  from  the  superficial  palmar  arch  are  well  or  poorly  developed  (page  784). 
When  the  ulnar  palmar  digital  is  small,  an  extra  branch  may  arise  from  the  deep  palmar  arch, 
passing  along  the  ulnar  border  of  the  little  finger. 

9.  The  Radial  Recurrent  Arteries. — -The  radial  recurrent  arteries  (Fig.  717) 
are  two  or  three  small  branches  which  arise  from  the  concave  surface  of  the  deep 
palmar  arch  and  pass  proximally  over  the  carpus  to  anastomose  with  the  terminal 
branches  of  the  anterior  interosseous  and  of  the  anterior  radial  and  ulnar  carpal 
arteries.  By  the  anastomosis  of  these  various  arteries  there  is  formed  upon  the 
anterior  surface  of  the  carpus  a  net- work,  the  rete  carpale  volare,  from  which  branches 
are  distributed  to  the  wrist  and  to  the  carpal  articulations. 

The  Collateral  Circulation  in  the  Forearm. — The  brachial  artery,  after 
being  ligated,  will  convey  blood  to  the  forearm  arteries  by  means  of  its  superior  and 
inferior  profunda  branches  and  by  the  anastomotica  magna,  which  form  a  rich  anas- 
tomosis at  the  elbow-joint  with  the  radial  recurrent,  the  anterior  and  posterior  ulnar 
recurrent,  and  the  posterior  interosseous  recurrent.  The  collateral  circulation  in  the 
parts  supplied  by  the  ulnar  and  radial  arteries,  after  ligation  of  one  or  other  of  these 
vessels,  will  be  carried  on  by  means  of  the  direct  anastomoses  between  the  two 
arteries  in  the  superficial  and  deep  palmar  arches  and  also  by  way  of  the  anterior  and 
posterior  carpal  net-works.  To  the  former  of  these  net-works  the  radial  artery  sends 
contributions  from  its  posterior  carpal  branch  and  the  ulnar  from  its  posterior  carpal 
and  anterior  and  posterior  interosseous  branches,  while  to  the  latter  the  radial  sends 
its  anterior  carpal  branch  and  the  ulnar  its  anterior  carpal  and  anterior  interosseous 
branches. 

THE   THORACIC    AORTA. 

The  thoracic  aorta  (aorta  thoracalis)  (Fig.  718)  is  the  continuation  of  the 
descending  limb  of  the  aortic  arch,  and  begins  upon  the  left  side  of  the  body 
of  the  fourth  thoracic  vertebra.  It  passes  downward  through  the  thorax  in  the 
posterior  mediastinum  and  terminates  below  at  the  diaphragm,  behind  which  it 
passes  to  become  continuous  with  the  abdominal  aorta.  In  the  upper  part  of  its 
course  it  lies  a  little  to  the  left  of  the  median  line,  but  it  tends  slightly  to  the  right 
as  it  descends,  and  eventually  occupies  the  median  line  just  before  it  reaches  the 
diaphragm. 

Relations. — Anteriorly  it  is  in  relation  with  the  left  bronchus  and  the  root  of 
the  left  lung  in  its  upper  part,  and  it  is  crossed  very  obliquely  by  the  oesophagus, 
which  separates  it  from  the  pericardium  and  the  posterior  surface  of  the  left  auricle 
of  the  heart.  Posteriorly  it  rests  upon  the  bodies  of  the  eight  lower  thoracic  ver- 
tebra?, or  rather  throughout  the  greater  part  of  its  extent  upon  the  anterior  common 
ligament  of  the  thoracic  vertebrae,  and  at  about  the  level  of  the  fifth  vertebra  has 
passing  obliquely  upward  behind  it  the  thoracic  duct  and,  at  the  level  of  the  eighth 
vertebra,  the  vena  hemi-azygos. 

Upon  the  right  side  are,  above,  the  oesophagus  and  lower  down  the  right  pleura. 
The  thoracic  duct  passes  upward  upon  its  right  side  and  slightly  behind  it  as  far  as 
the  fifth  thoracic  vertebra,  and  the  vena  azygos  also  lies  upon  its  right  side,  but  on  a 
plane  slightly  posterior  to  it.  On  the  left  side  are  the  left  lung  and  pleura  above, 
and  below,  the  oesophagus,  while  the  vena  hemi-azygos  also  lies  upon  its  left  side,  but 
on  a  somewhat  posterior  plane. 

Branches. — The  branches  which  arise  from  the  thoracic  aorta  may  be  divided 
into  two  groups,  according  as  they  are  distributed  to  the  thoracic  viscera  or  to  the 
parietes.  The  visceral  branches  are  (1)  the  bronchial,  (2)  the  oesophageal,  and  (3) 
the  mediastinal .  The  parietal  branches  are  (4)  the  aortic  intercostal  arteries,  and 
(5)  the  diaphragmatic  branches. 


792  HUMAN   ANATOMY. 

Variations. — The  passage  of  the  thoracic  aorta  down  the  right  side  of  the  vertebral  column 
in  the  upper  part  of  its  course  and  the  origin  from  it  of  the  right  subclavian  artery  have  already 
been  discussed  in  connection  with  the  variations  of  the  aortic  arch  (page  724).  It  was  there 
pointed  out  that  both  these  abnormalities  depend  upon  the  more  or  less  perfect  persistence  of  the 
lower  portion  of  the  right  primitive  aortic  arch.  Not  infrequently  a  modification  of  this  condi- 
tion is  to  be  seen  in  the  existence  of  a  small  branch  arising  from  the  upper  part  of  the  thoracic  ' 
aorta  and  passing  obliquely  upward  and  to  the  right  behind  the  oesophagus.  This  is  the  arteria 
aberrans,  and  it  is  to  be  regarded  as  a  persistence  in  a  rudimentary  condition  of  the  distal  por- 
tion of  the  right  primitive  aortic  arch.  It  is  regarded  by  some  authors  as  a  normal  branch  of  the 
thoracic  aorta,  but  it  is  somewhat  inconstant  in  its  occurrence.  Occasionally  it  anastomoses 
with  the  first  or  second  intercostal  branches  of  the  superior  intercostal  artery  (page  765). 

1.  The  Bronchial  Arteries. — The  bronchial  arteries  (aa.  bronctaiales)  (Fig. 
718)  are  somewhat  variable  in  number;  while  three  are  usually  described,  they 
may  be  reduced  to  two  or  increased  to  four.  They  arise  from  the  upper  portion 
of  the  thoracic  aorta  and  pass  to  the  right  and  left  bronchi,  and  are  continued  along 
these  to  supply  the  tissue  of  the  lungs.  The  right  bronchial  artery,  which  very 
frequently  arises  from  the  first  right  aortic  intercostal,  passes  to  the  right  in  front 
of  the  cesophagus  and  applies  itself  to  the  posterior  surface  of  the  right  bronchus, 
along  which  it  passes  to  the  lung.  In  its  course  it  gives  off  minute  branches  to 
the  cesophagus,  bronchus,  and  pericardium,  and  to  the  lymphatic  nodes  in  its  neigh- 
borhood. 

The  left  bronchial  arteries,  which  are  usually  two  in  number,  apply  them- 
selves at  once  to  the  posterior  surface  of  the  left  bronchus  as  it  passes  in  front  of  the 
aorta  and  are  continued  along  this  to  the  lung.  They  give  off  small  branches  to  the 
cesophagus  and  to  neighboring  lymphatic  nodes.  The  upper  of  the  two  vessels  fre- 
quently arises  by  a  common  stem  with  the  right  bronchial,  and  may  be  the  only  one 
that  is  present. 

2.  The  Oesophageal  Arteries. — The  cesophageal  branches  (aa.  oesophageae) 
(Fig.  718)  of  the  thoracic  aorta  are  also  variable  in  number,  forming  a  series  of  four  or 
sometimes  five  or  six  small  vessels  which  arise  in  succession  from  above  downward 
from  the  anterior  surface  of  the  aorta.  After  a  short  but  somewhat  tortuous  course, 
they  reach  the  cesophagus,  in  the  wall  of  which  they  branch  to  form  a  net-work  which 
receives  branches  from  the  bronchial  arteries,  from  the  inferior  thyroid  above  and  the 
gastric  artery  below. 

3.  The  Mediastinal  Arteries. — The  mediastinal  arteries  (rami  pericardiac!) 
are  a  number  of  small  vessels  which  arise  from  the  anterior  surface  of  the  thoracic 
aorta  and  are  distributed  to  the  mediastinal  lymph-nodes  and  the  posterior  surface  of 
the  pericardium. 

4.  The  Aortic  Intercostal  Arteries. — The  aortic  intercostals  (aa.  inter- 
costales)  (Fig.  718)  supplying  the  tissues  of  the  lower  intercostal  spaces,  are  usually 
nine  in  number  on  each  side,  while  a  tenth,  sometimes  termed  the  subcostal  artery, 
runs  along  the  lower  border  of  the  last  rib,  supplying  the  upper  part  of  the  abdom- 
inal wall.  The  arteries  arise  in  pairs  from  the  posterior  surface  of  the  thoracic  aorta 
and  pass  outward  over  the  bodies  of  the  vertebra?  to  the  intercostal  spaces,  those  of 
the  right  side  being,  for  the  most  part,  somewhat  longer  than  those  of  the  left, 
pwing  to  the  position  of  the  thoracic  aorta  to  the  left  of  the  vertebral  column  through- 
out the  greater  portion  of  its  length.  Arrived  at  the  intercostal  space,  each  artery 
passes  obliquely  outward  and  upward  across  the  space  towards  the  angle  of  the  rib 
next  above,  resting  upon  the  internal  intercostal  fascia,  and  covered  by  pleura.  It 
then  pierces  the  intercostal  fascia  and,  as  far  as  the  angle  of  the  rib,  runs  between  the 
fascia  and  the  external  intercostal  muscle.  On  reaching  the  angle  of  the  rib  the  artery 
passes  beneath  the  internal  intercostal  muscle  and  is  continued  around  the  thoracic 
wall  in  the  subcostal  groove  of  the  rib,  and  between  the  two  intercostal  muscles,  to 
terminate  usually  by  inosculating  in  front  with  the  upper  of  the  two  anterior  inter- 
costal arteries  given  off  by  the  internal  mammary  or  the  musculo-phrenic  to  each 
intercostal  space.  The  arteries  which  pass  to  the  tenth  and  eleventh  intercostal 
spaces  continue  onward  beyond  the  extremities  of  their  corresponding  ribs,  and, 
passing  _  between  the  oblique  muscles  of  the  abdomen,  anastomose  with  the  deep 
epigastric  artery.  The  same  arrangement  occurs  in  the  case  of  each  of  the  tenth 
aortic  intercostal  (subcostal)  arteries.      These,  however,  throughout  that  portion  of 


THE  THORACIC   AORTA.  793 

their  course  in  which  they  are  in  relation  to  the  twelfth  ribs,  rest  upon  the  quadratus 
lumb.orum  muscles,  beneath  the  transversalis  fascia,  and  at  the  outer  border  of  that 
muscle  pass  beneath  the  fibres  of  the  transversalis  abdominis,  and,  more  laterally, 
perforating  the  internal  oblique,  come  to  lie  between  that  muscle  and  the  external 
oblique. 

Relations. — In  the  first  portion  of  their  course,  while  passing  over  the  bodies 
of  the  vertebrae,  the  right  aortic  intercostals  are  crossed  by  the  thoracic  duct  and  by 
the  vena  azygos,  and  the  upper  ones  are  also  crossed  by  the  oesophagus.  Those 
of  the  left  side  are  crossed  by  the  vena  hemiazygos,  and  both  sets  are  covered 
by  the  pleura.  Opposite  the  heads  of  the  ribs  they  are  crossed  by  the  ganglionated 
cord  of  the  sympathetic  nervous  system,  the  lower  ones  also  by  the  splanchnic  nerves, 
and  in  their  course  through  the  intercostal  spaces  they  are  in  relation  to  the  inter- 
costal veins  and  nerves,  each  artery  lying  below  its  corresponding  vein  and  above  the 
nerve,  but  on  a  plane  slightly  posterior  to  both.  The  arteries  of  the  upper  spaces  lie 
at  first  below  the  corresponding  nerves,  but  as  they  approach  the  lower  borders  of 
their  ribs  they  cross  the  nerves  obliquely,  and  throughout  the  greater  part  of  their 
course  possess  the  relation  described. 

Branches. — Each  artery  gives  off  small  branches  to  the  bodies  of  the  vertebra  and  to  the 
pleura,  and  throughout  its  course  through  the  intercostal  space  numerous. 

(a)  Muscular  branches,  which  supply  the  intercostal  muscles,  the  serratus  magnus,  and 
the  pectorales  major  and  minor,  anastomosing  with  the  thoracic  branches  from  the  axillary 
artery.  The  vessels  of  the  lower  spaces  and  the  subcostal  also  supply  the  upper  portions  of 
the  abdominal  muscles,  the  subcostal  anastomosing  with  branches  of  the  uppermost  lumbar 
artery  and  with  the  ascending  branch  of  the  superficial  circumflex  iliac  ;  the  lower  vessels  also 
give  off  numerous  branches  to  the  diaphragm  which  anastomose  with  the  phrenic  arteries 
from  the  abdominal  aorta.  Some  of  the  muscular  branches  which  arise  from  the  vessels  of  the 
third,  fourth,  and  fifth  spaces  send  branches  to  the  mammary  gland,  assisting  the  perforating 
branches  of  the  internal  mammary  and  the  long  thoracic  branch  of  the  axillary  in  the  supply  of 
that  structure.  These  intercostal  mammary  branches  (rami  mammarii  laterales)  may  become 
greatly  enlarged  during  lactation,  and  may  give  rise  to  considerable  hemorrhage  in  the  operation 
for  removal  of  the  gland. 

In  addition,  each  aortic  intercostal  gives  off  a  dorsal,  a  lateral  cutaneous,  and  a  collateral 
branch. 

(6)  The  dorsal  branch  (ramus  posterior)  arises  from  each  artery,  just  as  it  enters  its  inter- 
costal space,  and  passes  directly  backward,  in  company  with  the  posterior  division  of  the 
corresponding  spinal  nerve,  between  the  necks  of  the  adjacent  ribs  and  internal  to  the  superior 
costo-transverse  ligament.  Having  reached  the  vertebral  groove,  it  divides  into  a  spinal  and  a 
muscular  branch.  The  former  (ramus  spinalis)  passes  through  the  intervertebral  foramen  in 
company  with  the  root  of  the  spinal  nerve,  and,  within  the  spinal  canal,  gives  off  branches  to 
the  body  of  the  vertebra  and  its  neural  arches  and  to  the  dura  mater,  and  also  branches  which 
pass  to  the  spinal  cord  and  anastomose  with  the  anterior  and  posterior  spinal  arteries.  The 
muscular  branch  (ramus  muscularis)  continues  posteriorly  in  the  direction  of  the  main  stem  of 
the  vessel  and  divides  into  an  external  and  an  internal  branch  which  pass  between  the  principal 
masses  of  the  dorsal  musculature,  supplying  these  and  terminating  in  branches  to  the  integu- 
ment of  the  back. 

(c)  The  lateral  cutaneous  branch  (ramus  cutaneus  lateralis)  arises  at  about  the  axillary  line 
and  perforates  the  external  intercostal  muscle  in  company  with  the  lateral  cutaneous  branch  of 
the  corresponding  intercostal  nerve.  It  is  distributed  with  the  nerve  to  the  integument  of  the 
lateral  portions  of  the  thorax,  also  supplying  the  serratus  magnus  and  the  pectoral  muscles 
and  anastomosing  with  the  perforating  branches  of  the  internal  mammary  and  with  the  thoracic 
branches  of  the  axillary  artery. 

(d)  The  collateral  branch  arises  as  the  intercostal  approaches  the  angle  of  its  rib.  It 
passes  obliquely  outward  and  downward  to  the  upper  border  of  the  rib  next  below,  along  which 
it  runs  to  terminate  by  anastomosing  with  the  lower  of  the  two  anterior  intercostal  branches 
given  off  by  the  internal  mammary  or  the  musculo-phrenic  to  each  intercostal  space.  The 
collateral  branches  of  the  three  lower  intercostals  are  small  and  inconstant  and,  when  present, 
terminate  in  the  abdominal  wall. 

Variations.— The  intercostal  arteries  of  the  first  and  second  spaces  usually  arise  from  the 
superior  intercostal  branch  of  the  subclavian,  but  occasionally  the  artery  of  the  second  space, 
and  more  rarely  that  of  the  first,  may  arise  from  the  thoracic  aorta.  Or,  conversely,  the  arteries 
of  the  third  and  fourth  intercostal  spaces,  as  well  as  those  of  the  first  and  second,  mav  arise 
from  the  superior  intercostal,  the  aortic  intercostals  being  correspondingly  reduced  in  number. 


794  HUMAN    ANATOMY. 

Occasionally  the  second  intercostal  is  formed  by  a  branch  from  the  first  aortic  intercostal 
which  runs  upward  to  the  second  space  over  the  neck  of  the  third  rib,  and  a  similar  condition 
may  be  met  with  in  the  lower  arteries,  two  or  more  intercostal  spaces  being  supplied  from  a 
common  stem.  Finally,  the  right  and  left  arteries  of  one  or  all  of  the  pairs  may  arise  from  a 
common  stem,  springing  from  the  posterior  median  line  of  the  aorta. 

Practical  considerations  of  the  thoracic  aorta  are  discussed  with  those  of  the  aortic  arch 
on  page  726. 

THE  ABDOMINAL   AORTA. 

The  abdominal  aorta  is  the  continuation  below  the  diaphragm  of  the  thoracic 
aorta.  It  may  be  said  to  begin,  therefore,  at  the  lower  border  of  the  twelfth  thoracic 
vertebra,  and  passes  downward  upon  the  bodies  of  the  four  upper  lumbar  vertebrae 
lying  almost  in  the  median  line.  It  is  usually  described  as  terminating  opposite  the 
fourth  lumbar  vertebra  by  dividing  into  the  right  and  left  common  iliac  arteries, 
although  it  is  really  continued  onward  beyond  that  point  as  a  relatively  feeble  vessel 
which  is  termed  the  middle  sacral  artery.  It  seems  advisable,  however,  to  adhere  to 
the  classic  definitions  of  the  artery,  and  to  regard  the  middle  sacral,  for  purposes  of 
description,  as  one  of  its  branches. 

Relations. — Posteriorly,  the  abdominal  aorta  rests  upon  the  anterior  com- 
mon ligament  of  the  four  upper  lumbar  vertebrae  and  crosses  the  left  lumbar  veins. 
Anteriorly,  in  its  uppermost  part,  it  is  invested  by  the  sympathetic  solar  plexus,  from 
which  branches  pass  downward  along  the  vessel,  forming  the  aortic  plexus.  A  little 
lower  it  is  crossed  by  the  splenic  vein,  the  pancreas,  the  left  renal  vein,  and  the 
third  portion  of  the  duodenum,  and  still  lower  it  is  in  relation  with  the  coils  of 
the  small  intestine,  from  which,  however,  it  is  separated  by  the  peritoneum.  Upon 
a  more  anterior  plane  there  are,  above,  the  left  lobe  of  the  liver,  and  the  stomach 
and  transverse  colon.  To  the  right,  it  is  in  contact,  in  its  upper  part,  with  the 
thoracic  duct  and  the  receptaculum  chyli,  which  lie  partly  covered  by  it,  and  with 
the  right  crus  of  the  diaphragm,  which  separates  it  from  the  inferior  vena  cava  ; 
lower  down  it  is  in  direct  contact  with  the  vena  cava.  To  the  left,  is  the  left  crus 
of  the  diaphragm  and  the  fourth  portion  of  the  duodenum  above,  while  below  it 
is  separated  by  the  peritoneum  from  coils  of  the  small  intestine,  and  has  running 
alongside  the  left  spermatic  (ovarian)  artery  and  vein,  and  still  more  laterally  the 
left  ureter. 

Branches. — The  branches  of  the  abdominal  aorta,  like  those  of  the  thoracic, 
may  be  divided  into  two  sets,  visceral  and  parietal. 

The  visceral  branches  are  (1)  the  coeliac  axis,  (2)  the  superior  mesenteric, 
and  (3)  the  infe?'ior  mesenteric  artery.  These  are  median  unpaired  branches  which 
arise  from  the  anterior  surface  of  the  aorta;  in  addition,  there  are  a  number  of  paired 
visceral  branches:  (4)  the  itiferior  phrenic,  (5)  the  suprarenal,  (6)  the  renal,  and  (7) 
the  spermatic  or  ovaria?i  arteries. 

The  parietal  branches  are  (8)  the  lumbar  arteries,  of  which  there  are  four 
pairs,  (9)  the  middle  sacral,  and  (10)  the  common  iliac  arteries.  With  the  excep- 
tion of  the  middle  sacral,  the  parietal  branches  are  all  paired. 

Considered  in  the  order  of  their  origin  from  the  aorta,  the  branches  are  ar- 
ranged thus:  (1)  The  inferior  phrenics,  (2)  the  cceliac  axis,  (3)  the  suprarenals, 
(4)  the  superior  mesenteric,  (5)  the  first  pair  of  lumbar  arteries,  (6)  the  renals, 
(7)  the  spermatics  or  ovarians,  (8)  the  second  pair  of  lumbars,  (9)  the  inferior 
mesenteric,  ( 10  and  1 1 )  the  third  and  fourth  pairs  of  lumbars,  ( 1 2)  the  middle  sacral, 
and  (13)  the  co>mno7i  iliacs. 

Variations  of  the  abdominal  aorta  are  not  common.  In  cases  in  which  the  aortic  arch 
bends  to  the  right,  the  abdominal  aorta  may  lie  somewhat  to  the  right  of  the  median  line,  and  it 
has  been  observed  to  pass  downward  upon  the  right  of  the  inferior" vena  cava.  Variations  also 
occur  in  the  level  at  which  the  aorta  bifurcates  into  the  common  iliacs.  In  the  majoritv  of  cases 
the  bifurcation  is  opposite  the  middle  of  the  fourth  lumbar  vertebra,  but  it  is  not  infrequently 
lower,  taking  place  opposite  the  lower  half  of  that  vertebra,  opposite  the  succeeding  interver- 
tebral disc,  or,  in  rare  cases,  opposite  the  upper  portion  of  the  fifth  vertebra.  Bifurcation  at  a 
higher  level  than  usual  is  less  frequent,  but  it  has  been  observed  as  high  as  opposite  the  inter- 
vertebral disc  between  the  third  and  fourth  vertebras,  and,  in  very  rare  cases,  the  artery  has 
been  found  to  divide  as  high  as  the  second  lumbar  vertebra. 


THE   ABDOMINAL    AORTA 


795 


Fig.  718. 


Vertebral  artery 
1  carotid  artery 

Superior  intercostal  artery '/     Yjfc. 

Subclavian  artery"  ^v*"-^'     i 

Innominate  artery 
I.  aortic  intercostal  artery 


Aorta  and  its  branches  ;  ten  intercostal  arteries  are  present,  first  supplvi 
side  internal  intercostal  muscles  are  in  position,  on  left  they  ha 


796  HUMAN   ANATOMY. 

Although  the  abdominal  aortic  stem  is  very  constant  in  its  relations,  considerable  variation 
occurs  in  the  origin  of  its  branches.  Most  of  these  will  be  considered  in  connection  with  the 
description  of  the  branches  concerned,  but  it  may  be  noted  here  that  very  frequently  a  number 
of  small  branches,  terminating  in  the  neighboring  organs  or  connective  tissue  and  lymph-nodes, 
arise  from  the  abdominal  aorta,  in  addition  to  the  branches  which  have  already  been  named. 
These  small  branches  are  rather  inconstant,  and  may  arise  from  either  the  anterior  surface  of 
the  aorta,  in  which  case  they  are  unpaired  vessels,  or  in  pairs  from  its  sides: 

Their  existence  seems  to  indicate  the  occurrence  of  a  primitively  strictly  segmental  arrange- 
ment of  the  branches  of  the  abdominal  aorta,  and  a  type-condition  has  been  supposed  to  occur 
in  which  the  aorta  gives  off,  opposite  each  segmental  interval  that  it  passes,  three  pairs  of  ves- 
sels, which  arrange  themselves  in  three  distinct  sets 
pIG   _Tq  (Fig.  719).     One  set  arises  from  the  anterior  surface  of 

the  aorta,  and  is  usually  reduced,  either  by  fusion  or 
by  the  degeneration  of  one  or  other  of  each  pair,  to  a 
single  unpaired  vessel  for  each  segment ;  a  second  set 
arises  from  the  sides  of  the  aorta  and,  like  the  first  set, 
is  distributed  to  the  abdominal  viscera;  and  a  third  set 
arises  from  the  posterior  surface  of  the  aorta  and  is  dis- 
tributed to  the  abdominal  parietes. 

Of  the  unpaired  set  of  vessels,  only  three  persist 
until  adult  life,  becoming  the  coeliac  axis  and  the  sup- 
erior and  inferior  mesenteric  arteries,  the  position  oc- 
cupied by  these  vessels  in  the  adult  being  due  to  a 
downward  migration  which  they  undergo,  the  coeliac 
axis  representing  the  ventral  visceral  branch  of  the 
fourth  thoracic  or  possibly  a  higher  segment,  the  sup- 
erior mesenteric  that  of  the  seventh  thoracic,  and  the 
inferior  mesenteric  that  of  the  twelfth  thoracic.  The 
paired  visceral  branches  are  developed  mainly  in  con- 
nection with  the  embryonic  kidney,  and  on  the  replace- 
menPXLncht^'SfdSihS'S.  Tmffn  ment  of  this  by  the  adult  organ  the  majority  of  them 
body-trunk  (aorta) ;  B,  somatic  branch  to  body-  disappear,  the  suprarenal,  renal,  and  spermatic  arteries 
walls;  c,  paired  visceral  branches;  .D, unpaired  ancj  certain  inconstant  branches  which  are  lost  in  the 
v.sceral  branch ;  £,  pentoneum.  neighboring  connective  tissue  representing  them  in  the 

adult.  Of  the  parietal  paired  set,  the  four  pairs  of 
lumbar  arteries  correspond  to  the  four  upper  lumbar  segments,  while  the  common  iliacs  are 
the  branches  of  the  fifth  lumbar  segment.  The  lumbar  arteries  are  evidently  serially  homolo- 
gous with  the  thoracic  intercostals  and  present  many  similarities  to  the  lower  members  of  that 
series,  but  the  common  iliacs  are  peculiar  in  that  they  give  rise  to  branches  which  pass  to  the 
pelvic  viscera,  a  condition  which  may  be  explained  by  the  fact  that  the  paired  visceral  branches 
of  the  third  lumbar  segment  unite  with  them  and  are  represented  by  the  hypogastric  artery 
and  its  branches. 

Practical  Considerations. — The  abdominal  aorta  is  the  subject  of  aneurism 
much  more  rarely  than  is  the  thoracic  aorta,  because  of  the  relatively  less  powerful 
cardiac  impulse  which  reaches  it.  The  sac  is  most  often  situated  in  the  neighbor- 
hood of  the  cceliac  axis  because  («)  in  this  region  the  artery  has  lost  the  support 
afforded  by  the  tendinous  arch  of  the  diaphragm,  which  produces  a  constriction  in 
its  walls  at  each  ventricular  systole  ;  (&)  it  rather  suddenly  contracts  about  one  and 
a  half  inches  below  this  level  (after  having  given  off  a  number  of  large  branches), 
so  that  the  intervening  portion  is  somewhat  fusiform  or  pouched  (Agnew)  ;  (c)  the 
pressure  on  this  aortic  segment  is  increased  by  the  sudden  alteration  in  the  direction 
of  the  blood-current  caused  by  the  presence  of  these  branches  (the  inferior  phrenics, 
the  cceliac  axis,  the  suprarenals,  superior  mesenteric,  etc.);  and  (d)  the  walls  at 
this  point  are  said  to  be  intrinsically  weak,  often  giving  way  (Woolsey)  during  injec- 
tions of  the  cadaver.  The  aneurism  may  occupy  any  aspect  of  the  vessel,  but  is 
more  commonly  on  the  anterior  wall,  which  receives  less  support.  As  it  enlarges  it 
will  cause  some  or  all  of  the  following  symptoms  : 

1.  Tumor  in^  the  epigastric  or  hypochondriac  region  (usually  the  left  because 
there  is  less  resistance  from  surrounding  organs  and  because  the  artery  inclines  in 
that  direction),  having  the  characteristic  bruit  and  expansile  pulsation,  commonly 
capable  of  being  outlined  by  palpation  or  grasped  (distinguishing  it  from  a  "  throb- 
bing aorta' ' ) ,  and  unchanged  as  to  pulsation  and  impulse  when  the  patient  is  put  in 
the  knee-elbow  position  (eliminating  growths  of  the  left  lobe  of  the  liver,  the  pylorus, 
or  the  pancreas,  in  which  the  tumor  falls  forward — i.e,  downward — and  the  impulse 
lessens  or  disappears)  (Osier).  2.  Dyspnoea  from  interference  with  the  descent  of 
the  diaphragm.      3.   Dysphagia  from  pressure  on  the  oesophageal  opening.      4.  Dys- 


THE   VISCERAL    BRANCHES.  797 

pepsia  and  vomiting  directly  from  pressure  upon  the  stomach,  and  indirectly  from 
involvement  of  the  solar  plexus.  5.  Jaundice  from  compression  of  the  common 
duct  and  duodenum.  6.  Polyuria  followed  by  albuminuria  and  hematuria  or  anuria 
from  pressure  on  the  renal  nerves.  7.  CEdema  of  the  legs  and  feet  from  pressure  on 
the  ascending  cava.  If  the  tumor  enlarges  posteriorly  there  is  apt  to  be  also  : 
8.  Pain  in  the  buttocks,  thighs,  and  loins  from  pressure  on  the  lumbar  nerves,  and 
in  the  back  from  pressure  on  the  solar  plexus  and  splanchnics,  or  from  erosion  of  the 
vertebra  ;  and  rarely  there  may  be  :  9.  Weakness  or  paralysis  of  the  lower  extremities 
from  involvement  of  the  cord.  As  a  rule,  the  pain,  distress,  and  disability  are  not  so 
great  in  abdominal  as  in  thoracic  aneurism,  because  of  the  greater  mobility  of  the 
abdominal  contents,  which  can  be  much  more  easily  displaced  than  those  of  the 
middle  or  posterior  mediastinum  and  with  consequences  not  so  directly  threatening  life. 

Abdominal  aneurisms  rupture  into  the  retroperitoneal  space,  the  peritoneal 
cavity,  the  intestines  (most  often  the  duodenum),  or — after  ulcerating  through  the 
diaphragm — into  the  pleura. 

Compression  of  the  abdominal  aorta  may  be  effected  by  special  tourniquets,  the 
intestines  being  first  well  emptied  and  then  got  out  of  the  way,  as  far  as  possible, 
by  rolling  the  patient  on  the  right  side  before  applying  the  pad,  between  which  and 
the  skin  a  soft  sponge  should  be  interposed.  The  pad  is  placed  a  little  to  the  left 
of  the  umbilicus,  or,  better — as  the  aorta  may  be  median  in  position — directly  over 
the  pulsation  of  the  vessel.  Macewen  has  effectively  controlled  the  abdominal  aorta 
by  throwing  the  weight  of  the  body  on  the  aorta  through  the  closed  right  hand  placed 
a  little  to  the  left  of  the  middle  line,  the  knuckle  of  the  index-finger  just  touching 
the  upper  border  of  the  umbilicus.  With  the  left  hand  the  arrest  of  the  blood-cur- 
rent is  ascertained  by  feeling  the  femoral  at  the  brim  of  the  pelvis.  Only  enough 
weight  to  arrest  the  femoral  pulse  Is  required.  If  the  patient  vomits  or  coughs,  the 
pressure  must  be  increased,  lest  the  hand  be  lifted  from  the  aorta  by  the  abdominal 
muscles. 

Of  course  these  methods  would  be  applicable  only  to  aneurisms  situated  near 
the  bifurcation.  Compression  has  cured  at  least  one  such  case.  They  have,  how- 
ever, been  applied  in  iliac  and  common  femoral  aneurism  and  to  control  hemorrhage 
during  inter-ilio-abdominal  or  hip-joint  amputation. 

Ligation  of  the  abdominal  aorta  has  been  done  in  about  a  dozen  cases  with 
uniformly  fatal  results.  The  ligature  has  been  applied  between  the  bifurcation  and  the 
origin  of  the  inferior  mesenteric  artery — one  and  a  half  to  two  inches  higher.  A  median 
incision  with  its  centre  at  the  umbilicus  is  made,  the  peritoneal  cavity  opened,  and 
the  intestines  displaced.  The  layer  of  peritoneum  over  the  artery  is  carefully  divided 
— or  scratched  through — and  the  vessel  isolated,  avoiding  the  sympathetic  fibres 
connecting  the  aortic  plexus  (lying  above  the  origin  of  the  inferior  mesenteric) 
with  the  hypogastric  plexus  (lying  between  the  common  iliacs)  (Astley  Cooper, 
Jacobson).  The  dense  areolar  tissue  surrounding  the  vessel  is  penetrated  and  the 
aneurism  needle  is  passed  through  it  from  right  to  left  to  avoid  injury  to  the  vena 
cava.  The  extraperitoneal  operation  closely  resembles  that  for  ligation  of  the  common 
iliac  (page  808). 

THE   VISCERAL    BRANCHES. 

1.  The  Cceliac  Axis. — The  cceliac  axis  (a.  coeliaca)  (Figs.  720,  721)  arises 
from  the  anterior  surface  of  the  abdominal  aorta,  a  short  distance  below  the  aortic 
opening  of  the  diaphragm,  and  is  a  short,  stout  trunk  from  1-1.5  cm.  in  length, 
which  projects  forward  above  the  upper  border  of  the  pancreas.  It  terminates  by 
dividing  simultaneously  into  (1)  the  g astric,  (2)  hepatic,  and  (3)  splenic  arteries. 

Variations. — The  cceliac  axis  may  be  wanting,  the  three  branches  to  which  normally  it 
gives  origin  arising  independently  from  the  aorta.  Occasionally  it  gives  rise  to  but  two  terminal 
branches,  usually  the  hepatic  and  splenic,  although  more  rarely  they  may  be  the  gastric  and 
splenic  ;  or,  while  dividing  into  three  terminal  branches,  these  may  be  the  gastric,  hepatic,  and 
a  common  stem  from  the  two  inferior  phrenics  ;  the  gastric,  splenic,  and  the  right  suprarenal ; 
or  the  gastric,  splenic,  and  the  right  gastro-epiploic.  It  may  also  give  rise  to  additional  branches, 
such  as  one  or  both  of  the  inferior  phrenics,  a  gastro-duodenal,  the  superior  mesenteric,  the 
colica  media,  or  the  pancreatica  magna,  this  last  being  normally  a  branch  of  the  splenic  artery. 


798 


HUMAN    ANATOMY. 


(a)  The  Gastric  Artery. — The  gastric  artery  (a  gastrica  sinistra)  (Fig.  720)  is 
the  smallest  of  the  three  branches  given  off  from  the  coeliac  axis.  In  the  first  portion 
of  its  course  it  passes  to  the  left  and  slightly  upward,  across  the  left  crus  of  the 
diaphragm,  lying  behind  the  posterior  layer  of  the  lesser  sac  of  peritoneum.  It  reaches 
the  lesser  curvature  of  the  stomach  near  the  opening  of  the  oesophagus  into  that 
viscus,  where  the  upper  part  of  the  posterior  wall  of  the  lesser  sac  of  peritoneum  passes 
over  upon  the  stomach  to  become  continuous  with  the  posterior  layer  of  the  lesser 

Fig  720. 


Gall  bladder 
Common  bile  duct 

Gasrro-duodenal  artery 
Right  kidney 
Pyloric  branch 


Coeliac  axis  and  ils  branches. 

(gastro-hepatic)  omentum.  It  then  curves  forward,  downward,  and  to  the  right 
along  the  lesser  curvature  of  the  stomach,  lying  between  the  two  layers  of  the  lesser 
omentum,  frequently  dividing  into  two  parallel  stems  in  this  portion  of  its  course, 
and  terminates  near  the  pyloric  end  of  the  stomach  by  anastomosing  with  the  pyloric 
branch  of  the  hepatic  artery. 

Branches.— Just  at  the  point  where  the  gastric  artery  reaches  the  stomach  it  gives  off— 
_  (aa)  (Esophageal  branches   (rami  cesophagei)  which  pass  upward   to  supply  the   lower 
portion  of  the  oesophagus,  anastomosing  with  the  oesophageal  branches  of  the  thoracic  aorta 
and  with  branches  of  the  inferior  phrenic  arteries.     Throughout  the  entire  length  of  its  course 
along  the  lesser  curvature  of  the  stomach  the  gastric  artery  gives  rise  to— 


THE    VISCERAL    BRANCHES.  799 

(bb)  Gastric  branches  which  pass  downward  over  both  surfaces  of  the  stomach,  anasto- 
mosing with  the  short  gastric  branches  from  the  splenic  artery  and  with  the  gastric  branches 
which  pass  upward  from  the  gastro-epiploic  arch  which  passes  along  the  greater  curvature  of 
the  stomach.  Some  of  the  branches  which  arise  from  the  more  proximal  portion  of  the  artery 
and  ramify  over  the  cardiac  portion  of  the  stomach  are  frequently  described  as  the  cardiac 
branches. 

(cc)  A  small  hepatic  branch  passes  upward  between  the  two  layers  of  the  lesser  omentum 
towards  the  left  end  of  the  transverse  fissure  of  the  liver,  where  it  anastomoses  with  the  left 
branch  of  the  hepatic  artery. 

Variations. — The  gastric  artery  occasionally  arises  directly  from  the  abdominal  aorta,  in 
which  case  it  may  give  rise  to  one  or  both  of  the  inferior  phrenic  arteries.  Its  hepatic  branch  is 
not  infrequently  enlarged,  and  then  constitutes  the  main  stem  of  the  left  branch  of  the  hepatic 
artery,  which  thus  seems  to  arise  from  the  gastric 

(b)  The  Hepatic  Artery. — In  the  first  portion  of  its  course  the  hepatic  artery 
(a.  hepatica)  (Figs.  720,  721)  passes  from  left  to  right  and  slightly  forward,  over  the 
right  crus  of  the  diaphragm,  lying  beneath  the  posterior  wall  of  the  lesser  sac  of  perito- 
neum. Where  this  passes  over  into  the  posterior  layer  of  the  lesser  (gastro-hepatic) 
omentum  towards  the  right,  the  artery  bends  upward  and  ascends,  in  the  free  edge  of 
the  lesser  omentum,  towards  the  transverse  fissure  of  the  liver,  where  it  divides  into 
two  terminal  branches. 

Relations. — In  the  first  portion  of  its  course  the  hepatic  artery  rests  below 
upon  the  upper  border  of  the  head  of  the  pancreas  and  is  in  contact  above  with  the 
lower  surface  of  the  Spigelian  lobe  of  the  liver,  upon  which  it  frequently  makes  a 
distinct  impression.  It  lies  at  first  upon  a  plane  posterior  to  the  portal  vein,  but 
later  it  crosses  the  left  surface  of  the  vein  and  comes  to  lie  in  front  of  it.  In  its 
course  upward  in  the  free  edge  of  the  lesser  omentum  the  artery  lies  anteriorly  to  the 
portal  vein  and  upon  the  left  side  of  the  common  bile-duct. 

Branches. — As  the  hepatic  artery  passes  between  the  two  layers  of  the  lesser  omentum  it 
gives  origin  to  two  branches,  the  pyloric  and  the  gastro-duodenal. 

(aa)  The  pyloric  branch  (a  gastrica  dextra)  is  the  smaller  of  the  two.  It  descends  to  the 
pyloric  end  of  the  stomach  and  then  bending  to  the  left,  runs  along  the  lesser  curvature  of  the 
stomach,  between  the  two  layers  of  the  lesser  omentum,  and  terminates  by  anastomosing  with 
the  gastric  artery.  It  gives  branches  to  either  side  of  the  pyloric  extremity  of  the  stomach  and, 
like  the  gastric  artery,  is  frequently  represented  by  two  parallel  vessels. 

(bb)  The  gastro-duodenal  (a  gastroduodenalis),  the  larger  branch,  descends  behind  the 
first  portion  of  the  duodenum  and  terminates  at  its  lower  border  by  dividing  into  two  branches, 
the  superior  pancreatico-duodenal  and  the  right  gastro-epiploic 

(aaa)  The  superior  pancreatico-duodenal  branch  (a  pancreaticoduodenalis  superior)  descends 
to  the  head  of  the  pancreas,  upon  the  surface  of  which  it  anastomoses  with  branches  of  the 
inferior  pancreatico-duodenal  branch  of  the  superior  mesenteric  artery.  It  sends  branches  into 
the  substance  of  the  gland  and  to  the  walls  of  the  duodenum. 

(bbb)  The  right  gastro-epiploic  artery  (a.  gastroepiploica  dextra)  passes  to  the  left  along  the 
greater  curvature  of  the  stomach,  between  the  folds  of  the  greater  omentum,  and  inosculates 
with  the  left  gastro-epiploic  branch  of  the  splenic  artery.  It  sends  branches  upward  upon  both 
surfaces  of  the  stomach,  which  anastomose  with  branches  from  the  gastric  artery  and  from  the 
pyloric  branch  of  the  hepatic,  and  other  branches  pass  downward  into  the  greater  omentum 
(epiploon). 

(cc)  The  terminal  branches  are  two  in  number  and  pass  the  one  to  the  right  and  the  other 
to  the  left  lobe  of  the  liver  The  right  branch  (  ramus  dexter)  passes  towards  the  right  extremity 
of  the  transverse  fissure  of  the  liver,  its  course  lying  either  in  front  of  the  hepatic  and  cystic 
ducts  or  between  these  two  structures.  At  the  extremity  of  the  fissure  it  divides  into  a  number 
of  branches  which  enter  the  substance  of  the  right  lobe  of  the  liver.  As  it  passes  across  the 
hepatic  duct  it  gives  off  a  cystic  branch  (a  cystica)  which  runs  downward  and  forward  along 
the  cystic  duct  to  the  gall-bladder,  whose  walls  it  supplies,  also  giving  some  small  branches  to 
the  liver.  The  left  branch  (ramus  sinister)  is  directed  towards  the  left  end  of  the  transverse 
fissure,  and,  after  giving  off  one  or  two  branches  which  enter  the  substance  of  the  Spigelian 
lobe,  terminates  by  dividing  into  a  number  of  branches  which  enter  the  left  lobe  of  the  liver. 

Variations— Variations  of  the  hepatic  artery  are  exceedingly  frequent.  The  artery  itself 
may  arise  directly  from  the  aorta  instead  of  from  the  cceliac  axis.  or.  by  the  enlargement  of  its 
anastomoses  and  the  diminution  of  the  normal  main  stem,  it  may  appear  to  be  a  branch  of  the 


8oo 


HUMAN    ANATOMY. 


gastric  or  more  frequently  of  the  superior  mesenteric  artery.  It  has  also  been  described  as 
arising  from  the  right  renal  artery.  Further,  by  the  enlargement  of  anastomoses,  associated 
with  a  persistence  of  the  normal  main  stern,  accessory  hepatic  arteries  from  the  gastric  or 
superior  mesenteric,  or  both,  may  be  present,  and  an  accessory  stem  may  arise  from  the  aorta. 
.  Great  variation  occurs  in  the  point  at  which  the  artery  divides  into  its  two  terminal 
branches.  This  division  may  occur  as  low  down  as  the  origin  of  the  gastro-duodenal  branch, 
so  that  in  its  course  up  the  free  edge  of  the  lesser  omentum  the  artery  may  be  represented  by 
two  parallel  stems  which  pass  respectively  to  the  right  and  left  lobes  of  the  liver.  Indeed,  not 
only  may  there  be  a  precocious  division  into  the  two  terminal  branches,  but  each  of  these  may 
again  divide,  almost  at  their  origin,  into  two  or  more  stems,  so  that  a  number  of  parallel  vessels, 
one  of  which  usually  represents  the  cystic  branch,  ascend  to  the  liver.  Occasionally  the  cystic 
branch  or  an  accessory  cystic  branch  arises  from  the  gastro-duodenal,  and  this  latter  vessel  may 
arise  from  the  cceliac  axis,  while  the  liver  and  gall-bladder  are  supplied  by  a  stem  which  arises 
from  the  superior  mesenteric  (Brewer). 

(Y)  The  Splenic  Artery. — The  splenic  artery  (a.  lienalis)  (Figs.  720,  721) 
is  the  largest  branch  of  the  cceliac  axis.  It  passes  in  a  more  or  less  tortuous  course 
over  the  left  crus  of  the  diaphragm  and  along  the  upper  border  of  the  pancreas,  lying 
behind  the  posterior  wall  of  the  lesser  sac  of  the  peritoneum.     It  crosses  the  anterior 


Fig.  721. 

Under  surface  of  left  lobe  of  livi 
(Esophageal  branches 


S'lieriT  mesenteric  artery 
"  plenic  artery 

Transverse  colon,  turned  up 

Left  kidney 


Inferior  pancreatico- 
duodenal artery 

Ascending  colon 
Middle  colic 


Coeliac  axis  and  its  branches  :  stomach  has  been  removed  ; 
transverse  colon  turned  up. 


surface  of  the  left  suprarenal  capsule  and  the  upper  part  of  the  left  kidney,  and, 
passing  between  the  two  layers  of  the  lieno-renal  ligament,  reaches  the  hilum  of  the 
spleen,  where  it  breaks  up  into  a  number  of  branches  which  pass  to  the  substance  of 
that  organ. 

Branches. —  ( aa )  Pancreatic  branches  ( rami  pancreatici )  are  given  off  from  the  splenic  artery 
throughout  the  entire  extent  of  its  course  along  the  upper  border  of  the  pancreas,  and  supply 
that  organ.  One  branch,  much  larger  than  the  others  (a.  pancreatica  magna),  arises  at  about 
the  junction  of  the  middle  and  left  thirds  of  the  artery  and.  entering  the  substance  of  the  gland 
obliquely,  passes  from  left  to  right  along  with  the  pancreatic  duct. 

(66)  Short  gastric  branches  (aa.  gastricae  breves),  variable  in  number,  are  given  off  either 
from  the  terminal  portion  of  the  artery  or  from  some  of  its  terminal  branches.  They  pass 
between  the  layers  of  the  gastro-splenic  omentum  to  the  left  end  of  the  greater  curvature  of  the 
stomach,  and.  passing  upon  the  surfaces  of  that  organ,  supply  it,  and  anastomose  with  the  cardiac 
branches  of  the  gastric  artery  and  with  the  branches  of  the  left  gastro-epiploic. 


THE    VISCERAL    BRANCHES 


801 


(cc)  The  left  gastro-epiploic  artery  (a-  gastroepiploicu  sinistra)  arises  close  to  the  termination 
of  the  splenic  and  passes  between  the  layers  of  the  gastro-splenic  omentum  to  the  greater  curvature 
of  the  stomach,  along  which  it  runs  between  the  layers  of  the  greater  omentum,  and  terminates  by 
inosculating  with  the  right  gastro-epiploic  branch  of  the  hepatic  artery.  Throughout  its  course  it 
gives  off  numerous  branches  which  pass,  on  the  one  hand,  upward  upon  both  surfaces  of  the 
stomach  to  anastomose  with  branches  of  the  gastric  artery,  and,  on  the  other  hand,  downward 
into  the  greater  omentum. 

Variations. — The  splenic  is  remarkably  constant  in  its  course  and  branches.  It  may  arise 
directly  from  the  aorta,  and  it  has  been  observed  to  give  off  the  gastric  artery,  a  large  branch 
to  the  left  lobe  of  the  liver,  and  the  middle  colic  artery. 

2.  The  Superior  Mesenteric  Artery. — The  superior  mesenteric  artery 
(a.  mesenterica  superior)  (Figs.  721,  722)  arises  from  the  anterior  surface  of  the 
abdominal  aorta,  about  1.5  cm.  below  the  cceliac  axis.  It  lies  at  first  behind  the 
pancreas,  but,  passing  downward  and  forward,  it  emerges  between  that  organ  and 
the  upper  border  of  the  third  portion  of  the  duodenum  and  enters  the  mesentery. 


Transverse  colon  — 


Pancreas 
Superior  mesenteric 

artery 

Middle  colic  artery 

Duodenum 


Ileo-colic  artery 


Left  colic  artery 
Duodenum 


Crest  of  ilium 


—  Part  of  jejunun 


-  Parts  of  ileum 


It  passes  downward  between  the  two  layers  of  the  mesentery,  gradually  curving 
towards  the  right,  and  terminates  near  the  junction  of  the  ileum  with  the  caecum  by 
anastomosing  with  its  own  ileo-colic  branch. 

Branches.— The  superior  mesenteric  artery  supplies  the  whole  length  of  the  small  intestine, 
with  the  exception  of  the  upper  part  of  the  duodenum,  and  also  a  considerable  portion  of  the 
large  intestine,  including  the  caecum  and  appendix,  the  ascending  colon,  and  about  half  the 

51 


8o2  HUMAN    ANATOMY. 

transverse  colon.  The  lower  portions  of  the  duodenum  and  ileum  and  the  large  intestine  are 
supplied  by  branches  given  off  from  the  concave  surface  of  the  artery,  while  the  rest  of  the  small 
intestine  receives  its  supply  from  a  somewhat  variable  number  of  branches  which  arise  from 
the  convex  surface. 

(a)  The  inferior  pancreatico-duodenal  (a.  pancreaticoduodenalis  inferior)  is  a  small  vessel 
which  usually  arises  from  the  superior  mesenteric  just  as  it  emerges  from  beneath  the  pancreas, 
although  it  occasionally  is  given  off  by  the  uppermost  of  the  intestinal  branches.  It  passes  towards 
the  right  along  the  upper  border  of  the  third  portion  of  the  duodenum,  and  supplies  that  portion 
of  the  intestine,  as  well  as  the  neighboring  portions  of  the  pancreas,  and  anastomoses  with  the 
superior  pancreatico-duodenal  branch  of  the  hepatic  artery. 

(6)  The  intestinal  branches  (rami  intestinales),  also  called  vasa  intesiini  tenuis,  are  from 
ten  to  sixteen  in  number,  and  arise  from  the  convex  surface  of  the  artery,  those  branches  which 
arise  from  the  upper  portion  of  the  parent  stem  being,  in  general,  larger  than  the  lower  ones. 
The  first  two  or  three  branches,  as  they  pass  towards  the  intestine  between  the  two  layers  of 
the  mesentery,  divide  into  an  ascending  and  a  descending  branch,  and  these  branches  inosculate 
to  form  a  series  of  primary  arches,  which  run,  in  a  general  way,  parallel  with  the  intestine. 
Lower  down,  in  addition  to  these  primary  arches,  secondary  ones  are  formed  by  the  inosculation 
of  branches  given  off  proximally  to  those  which  form  the  primary  arches  ;  still  later,  tertiary  arches 
make  their  appearance,  and  finally  the  arrangement  becomes  so  complicated  as  to  resemble 
a  net-work  rather  than  a  definite  series  of  arches.  From  the  convex  surfaces  of  the  primary 
arches  a  large  number  of  parallel  straight  branches  pass  to  the  intestine  and  are  distributed  to 
its  walls.  They  rarely  branch  in  their  course  through  the  mesentery,  and  are  usually  distributed 
to  one  side  of  the  intestine  and  then  to  the  other  alternately.  The  rich  anastomosis  which 
occurs  between  the  various  intestinal  branches,  and  which  varies  greatly  in  its  complexity,  serves 
to  equalize  the  supply  of  blood  to  the  entire  length  of  the  intestine  and  to  permit  of  abundant 
and  rapidly  collateral  circulation  to  any  portion  of  the  tract  from  which  the  direct  supply  may 
be  cut  off  by  pressure  exerted  during  peristalsis. 

(r)  The  ileo-colic  artery  (a.  ileocolica)  arises  about  half-way  down  the  concave  surface  of 
the  superior  mesenteric  either  independently  or  in  common  with  the  right  colic  branch.  It 
passes  downward  and  outward,  beneath  the  peritoneum,  towards  the  ileo-ca^cal  junction,  giving 
off  branches  which  inosculate  with  the  right  colic  above,  with  the  terminal  portion  of  the  supe- 
rior mesenteric  below,  and,  in  the  interval,  with  one  another  to  form  a  series  of  arches  from 
which  branches  are  supplied  to  the  terminal  portion  of  the  ileum,  to  the  Cfficum  and  the  vermi- 
form appendix  (a.  appendicularis)  and  to  the  lower  third  of  the  ascending  colon. 

(d  )  The  right  colic  artery  (a.  colica  dextra)  arises  from  the  concave  surface  of  the  superior 
mesenteric  either  a  short  distance  above  or  in  common  with  the  ileo-colic.  It  runs  towards  the 
right,  behind  the  peritoneum,  passing  over  the  right  psoas  muscle,  the  ureter,  and  the  spermatic 
(or  ovarian)  vessels,  and  as  it  approaches  the  ascending  colon  it  divides  into  an  ascending  and 
a  descending  branch.  These  inosculate  respectively  with  the  middle  colic  and  the  ileo-colic  to 
form  arches,  from  which  branches  pass  to  the  upper  two-thirds  of  the  ascending  and  to  a  portion 
of  the  transverse  colon. 

{e )  The  middle  colic  artery  (a.  colica  media)  arises  from  the  concave  surface  of  the  superior 
mesenteric  a  little  below  the  origin  of  the  inferior  pancreatico-duodenal  branch.  It  passes  for- 
ward and  downward  between  the  two  layers  of  the  transverse  mesocolon,  and  divides  into  a 
right  and  left  branch  which  inosculate  respectively  with  the  right  colic  and  with  the  left  colic 
branch  of  the  inferior  mesenteric  to  form  arches,  from  which  branches  pass  to  the  transverse 
colon. 

Variations. — Considerable  variation  occurs  in  the  number  and  position  of  the  branches  of 
the  superior  mesenteric  artery  and  also  in  the  complexity  of  the  anastomoses  which  occur 
between  these.  In  addition  to  those  usually  present,  branches  may  be  sent  to  any  of  the  neigh- 
boring organs,  such  as  the  liver,  stomach,  and  spleen,  and  the  artery  may  give  rise  to  the  hepatic, 
as  already  pointed  out,  or  to  the  gastro- duodenal,  or  even  the  gastric  or  renal  artery.  It  has 
been  observed  to  supply  the  place  of  the  inferior  mesenteric  artery  when  that  vessel  was  lacking, 
giving  off  left  colic,  sigmoid,  and  superior  hemorrhoidal  branches. 

From  the  embryological  stand-point  the  superior  mesenteric  represents  the  intestinal 
branch  of  the  omphalo-mesenteric  artery,  which,  during  the  early  months  of  fcetal  life,  passes 
outward  through  the  umbilicus  to  be  distributed  upon  the  surface  of  the  yolk-sac.  Usually  this 
artery  disappears,  except  in  so  far  as  it  is  concerned  in  the  formation  of  the  superior  mesenteric 
artery;  but  it  has  been  observed  to  persist,  appearing  as  a  branch  of  the  superior  mesenteric 
which  is  continued  forward  in  a  strand  of  connective  tissue  from  the  ileum  to  the  umbilicus, 
where  it  anastomoses  with  the  epigastric  artery  and  sends  a  branch  upward  along  with  the 
round  ligament  of  the  liver. 

3.  The  Inferior  Mesenteric  Artery. — The  inferior  mesenteric  artery  (a. 
mesenterica  inferior)  (Fig.  723)  arises  from  the  anterior  surface  of  the  abdominal 
aorta  from  3-4  cm.  above  the  bifurcation  of  that  vessel  into  the  two  common  iliacs. 


THE    VISCERAL    BRANCHES. 


803 


It  passes  downward  and  to  the  left,  beneath  the  peritoneum  and  resting  upon  the 
left  psoas  muscle,  and,  after  having  crossed  the  left  common  iliac,  it  terminates  upon 
the  upper  portion  of  the  rectum,  this  terminal  portion  being  called  the  superior  /iem- 
orrhoidal  artery. 

Branches. — {a)  The  left  colic  artery  (a.  colica  sinistra)  arises  shortly  below  the  origin  of 
the  artery  and  passes  upward  and  to  the  left.  It  divides  into  an  ascending  and  a  descending 
branch,  the  former  of  which  passes  between  the  two  layers  of  the  transverse  mesocolon  to  inos- 
culate with  the  middle  colic  branch  of  the  superior  mesenteric,  while  the  descending  branch, 
entering  the  sigmoid  mesocolon,  anastomoses  with  the  sigmoid  arteries.  From  the  arches  thus 
formed  branches  pass  to  the  left  portion  of  the  transverse  colon  and  to  the  whole  of  the  descend- 
ing colon. 

(b)  The  sigmoid  branches  (aa.  sigmoideae),  two  or  three  in  number,  are  given  off  as  the 
inferior  mesenteric  crosses  the  left  common  iliac.     They  run  downward  and  to  the  left  over  the 

Fig.  723. 


Superior  and  inferior  mesenteric  arteries ; 


ved. 


left  psoas  muscle  and,  passing  between  the  two  layers  of  the  sigmoid  mesocolon,  give  off  as- 
cending and  descending  branches  which  anastomose  with  one  another  and  with  the  left  colic 
and  superior  hemorrhoidal  arteries,  forming  with  them  arches  from  which  branches  pass  to  the 
sigmoid  colon. 

(c)  The  superior  hemorrhoidal  artery  (a.  haemorrhoidalis  superior)  is  the  terminal  portion 
of  the  inferior  mesenteric.  It  descends  into  the  pelvis  lying  between  the  folds  of  the  mesentery 
of  the  pelvic  portion  of  the  colon,  and  at  the  junction  of  the  colon  and  rectum  divides  into  two 
branches  which  continue  down  the  sides  of  the  rectum,  supplying  that  viscus  and  making  anas- 
tomoses with  the  middle  hemorrhoidal  from  the  internal  iliac  and  with  the  inferior  hemorrhoidal 
from  the  internal  pudic. 


804  HUMAN    ANATOMY. 

Variations.— The  inferior  mesenteric  artery  may  be  wanting,  its  place  being  supplied  by- 
branches  from  the  superior  mesenteric.  It  occasionally  gives  rise  to  the  middle  colic  artery  or 
to  an  accessory  renal  vessel. 

4.  The  Inferior  Phrenic  Arteries. — The  inferior  phrenic  arteries  (aa. 
phrenicae  inferiores)  (Fig.  718;  most  frequently  arise  from  the  abdominal  aorta,  either 
singly  or  by  a  common  trunk,  immediately  beneath  the  aortic  opening  of  the  dia- 
phragm and  above  the  cceliac  axis.  They  are  directed  upward  and  laterally  over 
the  crura  of  the  diaphragm,  to  which  they  supply  branches,  and  in  this  portion  of 
their  course  they  also  give  off  superior  suprarenal  branches  (rami  suprarenales 
superiores )  to  the  suprarenal  bodies.  Over  the  region  where  the  crura  pass  into  the 
diaphragm  proper,  each  inferior  phrenic  divides  into  an  internal  and  an  external 
branch.  The  former  is  the  smaller  of  the  two,  and  passes  inward  towards  the  oeso- 
phageal opening  of  the  diaphragm,  where  it  anastomoses  with  its  fellow  of  the  oppo- 
site side  to  form  an  arterial  ring  from  which  branches  descend  upon  the  oesophagus, 
supplying  the  lower  portion  of  that  structure  and  anastomosing  with  the  oesophageal 
branches  of  the  gastric  artery. 

The  external  branches  are  directed  laterally  upon  the  under  surface  of  the  dia- 
phragm, supplying  it.  They  pass  as  far  forward  as  the  costal  and  sternal  origins  of 
the  diaphragm,  anastomosing  with  the  musculo-phrenic,  superior  epigastric,  and 
superior  phrenic  branches  of  the  internal  mammary  arteries,  while  other  branches 
ramify  over  the  lateral  portions  of  the  diaphragm,  anastomosing  with  the  lower  inter- 
costals  and  perforating  the  central  tendon  to  anastomose  with  the  pericardial  arteries 
and  with  the  diaphragmatic  branches  of  the  thoracic  aorta. 

Variations. — The  inferior  phrenic  arteries  are  very  variable  in  their  origin.  One  fre- 
quently takes  its  origin  from  the  cceliac  axis  or  from  one  of  its  branches,  or  both  may  arise  from 
the  axis.  They  have  also  been  observed  to  arise  from  the  superior  mesenteric  or  the  renal,  or 
from  the  abdominal  aorta  below  the  superior  mesenteric.     They  also  vary  considerably  in  volume. 

5.  The  Suprarenal  Arteries. — The  suprarenal  arteries,  sometimes  termed  the 
middle  suprarenals  (aa  suprarenales  mediae)  (Fig.  718)  to  distinguish  them  from  the 
suprarenal  branches  of  the  inferior  phrenic  and  renal  arteries,  are  a  pair  of  small 
but  constant  branches  which  arise  from  the  sides  of  the  abdominal  aorta,  almost  oppo- 
site the  origin  of  the  superior  mesenteric  artery.  They  pass  outward  and  slightly 
upward  over  the  crura  of  the  diaphragm  to  the  suprarenal  bodies,  where  they  anasto- 
mose with  the  other  suprarenal  branches. 

6.  The  Renal  Arteries. — The  renal  arteries  (aa.  renales)  (Figs.  718,  1591) 
are  two  large  stems  which  arise  from  the  sides  of  the  abdominal  aorta  a  little  below 
the  origin  of  the  superior  mesenteric.  Usually  the  two  arteries  are  opposite  each 
other,  but  frequently  that  of  the  right  side  arises  a  little  lower  down  than  that  of 
the  left  side.  They  are  directed  outward  and  slightly  downward  towards  the  kidneys, 
each  artery,  before  reaching  the  hilum,  dividing  into  from  three  to  five  branches, 
which  enter  the  substance  of  the  kidney  independently  at  the  hilum. 

Relations. — In  their  course  towards  the  kidneys  the  renal  arteries  rest  upon  the 
lower  portions  of  the  crura  of  the  diaphragm  and  more  laterally  upon  the  upper  part  of 
the  psoas  muscles.  The  right  artery  is  somewhat  longer  than  the  left,  owing  to  the 
position  of  the  abdominal  aorta  a  little  to  the  left  of  the  median  line,  and  it  passes  behind 
the  inferior  vena  cava.  Both  vessels  are  almost  concealed  beneath  the  corresponding 
renal  veins,  and  at  the  hilum  of  the  kidney  the  majority  of  the  terminal  branches  pass 
in  front  of  the  upper  portion  of  the  ureter,  only  one  or  two  passing  behind  it. 

Branches. — Near  its  termination  each  artery  gives  off  branches  which  pass  to  the  adipose 
tissue  surrounding  the  kidney,  and  a  ureteral  branch  which  supplies  the  upper  part  of  the  ureter, 
anastomosing  with  the  ureteral  branch  of  the  spermatic  (or  ovarian)  artery.  More  proximally 
it  gives  origin  to  an  inferior  suprarenal  branch  (a  suprarenalis  inferior)  which  passes  upward  to 
the  lower  part  of  the  suprarenal  body  and  anastomoses  with  the  other  branches  which  go  to 
that  structure. 

Variations.— Not  infrequently  the  division  of  the  renal  arteries  into  their  terminal  branches 
takes  place  early,  sometimes  immediatelv  at  their  origin,  several  stems  arising  directly  from  the 
aorta  and  passing  outward  to  the  kidney.     Accessory  renal  branches  may  arise  from  the  abdomi- 


THE    VISCERAL    BRANCHES.  805 

nal  aorta  or  from  the  middle  sacral,  the  common  iliac,  the  internal  iliac,  or  the  inferior  mesen- 
teric, and  occasionally  the  renal  artery  proper  may  be  lacking  and  its  place  taken  by  a  vessel 
from  one  or  other  of  these  origins.  These  accessory  arteries  frequently  enter  the  substance  of 
tile  kidney  elsewhere  than  at  the  hilum. 

The  two  renal  arteries  may  arise  by  a  common  trunk  from  the  anterior  surface  of  the  aorta, 
and  they  occasionally  give  off  branches  which  are  either  accessory  to  or  replace  vessels  normally 
arising  elsewhere.  Thus  they  have  been  observed  to  give  rise  to  the  inferior  phrenics,  the  right 
branch  of  the  hepatic,  the  spermatics.  branches  to  the  pancreas  and  colon,  and  one  or  more  of 
the  lumbar  arteries. 

■ja.  The  Spermatic  Arteries. — The  spermatic  arteries  (aa.  spei  maticae  internal*) 
(Figs.  718,  1591)  are  two  slender  vessels  which  arise  from  the  anterior  surface  of  the 
aorta  a  little  below  the  renals.  They  are  directed  downward,  and  slightly  outward  and 
forward,  towards  the  lower  part  of  the  anterior  abdominal  wall,  and  as  they  approach 
this  each  vessel  curves  inward  towards  the  median  line  to  reach  the  internal  abdominal 
ring.  Here  it  comes  into  relation  with  the  vas  deferens  and  becomes  enclosed  with 
it  in  the  spermatic  cord.  Embedded  in  this  structure,  it  traverses  the  inguinal  canal 
and  passes  into  the  scrotum,  terminating  just  above  the  testis  by  dividing  into 
branches  which  pass  to  that  organ  and  to  the  epididymis. 

Relations. — In  its  course  through  the  abdomen  the  left  spermatic  artery  lies 
behind  the  peritoneum  and  rests  upon  the  psoas  muscle.  About  the  middle  of  this 
portion  of  its  course  it  crosses  obliquely  in  front  of  the  ureter,  and  lower  down  has 
resting  upon  it  the  sigmoid  colon.  The  right  artery  at  first  lies  in  the  root  of  the 
mesentery  ;  it  descends  obliquely  upon  the  anterior  surface  of  the  inferior  vena  cava 
and  then,  crossing  the  ureter  obliquely,  comes  to  lie  behind  the  terminal  portion  of 
the  ileum  and  frequently  behind  the  vermiform  appendix. 

In  the  pelvic  and  inguinal  portions  of  their  course  the  relations  of  both  arteries 
are  the  same.  The  vessels  rest  upon  the  psoas  muscle  to  the  outer  side  of  the  ex- 
ternal iliac  artery,  and  cross  the  lower  part  of  that  vessel  and  the  accompanying  vein 
to  reach  the  internal  abdominal  ring.  In  their  course  down  the  spermatic  cord  the 
arteries  lie  behind  the  anterior  group  of  the  spermatic  veins  and  in  front  of  the  vas 
deferens. 

Branches. — In  addition  to  the  terminal  (a)  testicular  and  (b)  epididymal  branches,  each 
spermatic  artery  gives  off — 

(c)  An  ureteral  branch  which  is  distributed  to  the  middle  portion  of  that  duct,  anastomosing 
with  the  ureteral  branch  of  the  renal  artery  above  and  with  branches  from  the  inferior  vesical 
artery  below. 

(d )  Cremasteric  branches  are  given  off  in  the  course  through  the  spermatic  cord  and  sup- 
ply the  cremaster  muscle,  anastomosing  with  the  cremasteric  branch  of  the  deep  epigastric 
artery. 

Variations. — The  spermatic  arteries  occasionally  arise  by  a  common  trunk,  or,  on  the 
other  hand,  they  may  arise  at  different  levels.  They  have  been  observed  to  arise  from  the 
renals,  especially  the  left  one,  from  the  suprarenals,  or  from  the  superior  mesenteric  artery. 

-jb.  The  Ovarian  Arteries. — The  ovarian  arteries  (aa.  ovaricae)  (Fig.  726") 
correspond  in  the  female  to  the  spermatic  arteries  of  the  male,  and  have  a  similar 
origin  and  similar  relations  in  the  abdominal  portion  of  their  course.  Arrived  at 
the  pelvis,  however,  they  cross  the  common  iliac  arteries  and  veins  and,  traversing 
the  suspensory  ligament  of  the  ovary,  pass  inward  between  the  folds  of  the  broad 
ligament  of  the  uterus,  terminating  beneath  the  ovary  by  inosculating  with  the  uterine 
artery. 

Branches. — Like  the  spermatic  arteries,  the  ovarian  give  off  (a)  ureteral  branches.  In  ad- 
dition, they  give  rise  to  (b)  tubal  branches,  which  pass  to  the  distal  portions  of  the  Fallopian 
tubes  ;  (c )  ligamentous  branches,  which  accompany  and  supply  the  round  ligament  of  the 
uterus  ;  and  (d  )  ovarian  branches,  which  enter  the  hilum  of  the  ovary  and  are  distributed  to  its 
substance. 

8.  The  Lumbar  Arteries. — The  lumbar  arteries  (aa.  lumbales)  (Fig.  718)  are 
arranged  in  four  pairs,  and  take  origin  from  the  sides  of  the  abdominal  aorta,  opposite 
the  four  upper  lumbar  vertebrae.  They  are  directed  outward  upon  the  bodies  of  the 
vertebrae,  the  lumbar  portion  of  the  sympathetic  cord  descending  in  front  of  them,  and 


8o6  HUMAN    ANATOMY. 

those  of  the  right  side  also  pass  beneath  the  inferior  vena  cava,  while  the  two  upper 
ones  of  the  same  side  pass  beneath  the  receptaculum  chyli.  They  then  pass  beneath 
the  psoas  muscle  and  the  branches  of  the  lumbar  plexus,  the  two  upper  ones  also 
passing  beneath  the  crura  of  the  diaphragm  ;  and  then,  farther  out,  they  pass  beneath 
the  quadratus  lumborum,  except  in  the  case  of  the  last  pair,  which  lies  upon  the  ante- 
rior surface  of  that  muscle.  At  the  outer  border  of  the  quadratus  they  pass  between 
the  transversalis  and  the  internal  oblique  muscles  of  the  abdomen,  and  are  continued 
onward  in  the  abdominal  wall,  eventually  piercing  the  internal  oblique  and  reaching 
the  rectus  muscle. 

Branches. — The  lumbar  arteries  are  to  be  regarded  as  continuations  of  the  series  of  inter- 
costal vessels,  and,  like  the  thoracic  members  of  the  series,  each  gives  off  a  dorsal  branch  ( ramus 
dorsalis).  This  arises  when  the  vessel  lies  behind  the  psoas  muscle  and  is  directed  posteriorly, 
soon  dividing  into  (a)  a  spinal  branch  (ramus  spinalis),  which  enters  the  spinal  canal  through 
the  intervertebral  foramen  and  anastomoses  with  the  anterior  and  posterior  spinal  arteries  ;  and 
(6)  a  muscular  branch,  which  is  distributed  to  the  muscles  and  skin  of  the  back.  In  addition, 
each  lumbar  artery  gives  off  numerous  branches  to  the  muscles  with  which  it  comes  into  relation. 

Variations. — One  or  more  of  the  lumbar  arteries  may  be  wanting  and  two  or  more  of  them 
may  arise  by  a  common  stem 

9.  The  Middle  Sacral  Artery. — The  middle  sacral  artery  (a.  sacralis  media ) 
(Fig.  718),  which  is  to  be  regarded  as  the  continuation  of  the  abdominal  aorta,  is 
a  small  vessel  arising  from  the  posterior  surface  of  the  aorta  immediately  above  its 
bifurcation  into  the  two  common  iliacs.  It  passes  downward  in  the  median  line  over 
the  last  two  lumbar,  the  sacral  and  the  coccygeal  vertebrae,  and  terminates  opposite 
the  tip  of  the  coccyx  by  sending  branches  to  the  coccygeal  body  or  Luschka'  s  gland 
(glomus  coccygeum). 

Branches. — Tt  sometimes  gives  rise  to  a  fifth  pair  of  lumbar  arteries  (aa.  lumbales  imae),  and 
lower  down  it  sends  off  small  lateral  branches  which  send  branches  inward  to  the  spinal  canal 
through  the  anterior  sacral  foramina  and  anastomose  with  the  lateral  sacral  branches  of  the 
internal  iliac  artery.  These  lateral  branches  appear  to  represent  a  continuation  of  the  inter- 
costal and  lumbar  series  of  arteries,  the  branches  which  enter  the  anterior  sacral  foramina  cor- 
responding to  the  dorsal  branches  of  those  vessels. 

Variations. — The  middle  sacral  occasionally  arises  from  one  or  other  of  the  common  iliac 
arteries,  and  it  may  give  origin  to  an  accessory  renal  artery. 

Practical  Considerations. — Some  of  the  branches  of  the  abdominal  aorta, 
including  the  splenic,  hepatic,  renal,  superior  and  inferior  mesenteric,  and  the  ovarian, 
have  been  the  subject  of  aneurism. 

These  aneurisms  do  not  usually  attain  any  great  bulk,  seldom  exceeding  the 
size  of  a  hen's  egg.  They  are  apt  to  be  round  or  oval  in  shape.  Occasionally— espe- 
cially in  the  aneurisms  of  the  renal  artery — they  may  almost  fill  the  abdominal 
cavity.  Except  when  connected  with  the  hepatic,  the  renal,  or  the  cceliac  axis,  they 
are  movable,  changing  their  position  in  the  various  movements  of  the  body.  They 
may  possess  also  the  characteristics  of  pulsation  and  bruit.  When  the  cceliac 
artery  is  affected  the  disease  cannot  be  distinguished  from  aneurism  of  the  parent 
trunk. 

In  cases  of  implication  of  the  hepatic  artery,  the  pressure-effects  of  the  tumor 
give  rise  to  pain  in  the  right  side  and  to  jaundice  from  obstruction  of  the  hepatic, 
cystic,  and  common  bile-ducts  (Agnew). 

The  renal  artery  has  been  found  to  be  aneurismal  in  a  small  number  of  instances, 
the  majority  being  of  traumatic  origin.  The  chief  symptoms  have  been:  (a)  tumor, 
varying  in  size,  situated  in  the  region  of  the  kidney,  immovable  with  respiration  or 
with  change  of  posture,  and  almost  always  without  impulse  or  bruit,  on  account  prob- 
ably of  the  usual  disproportion,  in  renal  aneurisms,  between  the  large  aneurismal 
cavity  and  the  size  of  _  the  vessel  involved  ;  (b)  hematuria  often  but  not  invariably 
present  ;  (t)  pain  elicited  by  pressure,  or  felt  in  the  loin  or  extending  to  the  genitalia, 
and  sometimes  accompanied  by  retraction  of  the  testis. 


THE    COMMON    ILIAC    ARTERIES.  807 

These  abdominal  aneurisms  are  not  uncommonly  unsuspected  until  they  have 
reached  a  late  stage,  and  may  even  rupture  and  cause  death  from  hemorrhage  with- 
out having  caused  more  than  trifling  inconvenience.  In  a  number  of  cases  the  pain 
— especially  apt  to  be  felt  in  the  back — has  been  the  only  symptom  complained  of. 
If  a  pulsating  tumor,  or  one  with  a  bruit,  can  be  felt,  it  would  be  proper  to  approach 
the  region  by  an  intraperitoneal  or — in  the  case  of  the  renals — possibly  an  extra- 
peritoneal incision,  and  ligate  the  artery  on  the  cardiac  and  distal  sides  of  the  sac. 

THE    COMMON    ILIAC    ARTERIES. 

The  common  iliac  arteries  (aa.  iliacae  communes)  (Figs.  724,  726)  are  usually 
regarded  as  the  terminal  branches  of  the  abdominal  aorta,  although  in  reality  the 
middle  sacral  artery  forms  the  morphological  continuation  of  that  vessel,  the  common 
iliacs  being  lateral  segmental  branches  comparable  to  a  pair  of  lumbar  or  intercostal 
arteries.  They  arise  opposite  the  body  of  the  fourth  lumbar  vertebra  and  pass 
obliquely  outward,  downward,  and  forward  to  about  the  level  of  the  sacro-iliac  articu- 
lation, where  they  terminate  by  dividing  into  the  internal  and  external  iliac  arteries. 

The  two  common  iliacs  diverge  from  each  other  at  an  angle  of  from  6o°-65°  in 
the  male  and  somewhat  more  (68°— 750)  in  the  female.  On  account  of  the  position  of 
the  abdominal  aorta  being  slightly  to  the  left  of  the  median  line,  the  right  artery  is 
slightly  longer  than  the  left,  and  is  inclined  to  the  median  line  at  a  slightly  greater  angle. 

Relations. — The  common  iliac  arteries  are  covered  by  peritoneum,  which  sepa- 
rates them  on  the  right  from  the  terminal  portion  of  the  ileum  and  on  the  left  from 
the  sigmoid  colon.  Anteriorly,  each  artery  is  crossed  by  the  ureter,  and  in  the  female 
by  the  ovarian  artery  and  vein,  and  by  the  branches  of  the  sympathetic  cord  which 
pass  downward  to  the  hypogastric  plexus.  The  left  common  iliac  is,  in  addition, 
crossed  by  the  superior  hemorrhoidal  branch  of  the  inferior  mesenteric  artery. 
Behind,  the  vessel  of  the  left  side  rests  upon  the  bodies  of  the  fourth  and  fifth 
lumbar  vertebrae,  that  of  the  right  side  being  separated  from  them  by  the  right 
common  iliac  vein  and  by  the  upper  end  of  the  corresponding  vein  of  the  left  side. 
Lower  both  vessels  rest  upon  the  psoas  muscle.  Laterally,  they  are  also  in  relation 
with  the  psoas  and  with  the  spermatic  artery  in  the  male  and,  in  the  case  of  the 
vessel  of  the  right  side,  with  the  upper  part  of  the  right  common  iliac  vein. 
Medially,  are  the  common  iliac  veins  and  the  hypogastric  plexus. 

Branches. — The  common  iliac  arteries  terminate  by  dividing  into  the  external 
and  internal  iliac  arteries.  In  addition,  they  give  rise  only  to  small  vessels  which 
pass  to  the  subjacent  psoas  muscles  and  to  the  neighboring  peritoneum  and  lymph- 
nodes  and  the  ureters. 

Variations. — A  certain  amount  of  variation  occurs  in  the  length  of  the  common  iliac  arte- 
ries, depending  largely  upon  the  level  at  which  the  bifurcation  of  the  abdominal  aorta  occurs. 
One  or  other  vessel  may  give  rise  to  the  middle  sacral  artery  or  to  an  accessory  renal  artery. 

Practical  Considerations. — The  common  iliac  artery  is  very  rarely  the  sub- 
ject of  aneurism.  Direct  compression  of  the  artery  may  be  made  by  either  of  the 
plans  described  as  applicable  to  the  abdominal  aorta,  and  should  be  applied  about 
one  inch  below  and  a  half  inch  to  the  right  or  left  of  the  umbilicus.  While  it  is 
easier  to  get  rid  of  the  intestines,  as  the  vessel  is  placed  more  laterally,  it  is  not 
always  easy  to  avoid  compression  of  the  aorta  itself. 

Ligation  of  the  common  iliac  may  be  required  for  aneurism  lower  down,  espe- 
cially of  the  upper  part  of  the  external  iliac,  or  for  wound,  or  as  a  preliminary  to  or. 
part  of  the  procedure  in  the  removal  of  pelvic  growths. 

It  may  be  effected  by  either  :  (1)  The  transperitoneal  method,  or  (2)  the  extra- 
peritoneal method.  1.  A  median  incision  from  umbilicus  to  symphysis,  opening  the 
peritoneal  cavity,  the  intestines  being  kept  in  the  upper  segment  of  the  abdomen  by 
pads  or  by  placing  the  patient  in  the  Trendelenburg  position,  will  give  easy  access 
to  the  vessel.  On  each  side  it  lies  directly  beneath  the  peritoneum,  but  there  are 
anatomical  differences  to  which  Makins  has  called  attention.  On  the  right  side 
the  vessel  is  uncovered  by  any  structure  of  importance,  and  may  be  reached  by 
dividing  the    peritoneum  directly  over  it  vertically.      On  this  side  the  vena  cava 


8o8  HUMAN    ANATOMY. 

and  both  common  iliac  veins  are  in  close  relation  with  the  artery,  the  latter  two 
passing  beneath  it.  On  the  left  side,  the  inferior  mesenteric  vessels  as  they  enter 
the  sigmoid  mesocolon  and  pass  downward  to  the  rectum  cover  practically  the 
whole  of  the  artery,  and  to  reach  the  common  iliac  comfortably  and  safely  the 
peritoneum  would  need  to  be  divided  close  to  the  left  of  the  median  line  of  the 
sacrum  and  be  displaced  outward.  The  vein  usually  lies  on  the  inner  side  of 
and  somewhat  behind  the  artery.  This  manoeuvre  has  the  disadvantage  of  ex- 
posing the  vein  freely,  but  this  would  probably  give  far  less  trouble  than  would  the 
numerous  mesenteric  vessels  when  swollen  by  reason  of  the  loss  of  their  peritoneal 
support. 

2.  By  the  extraperitoneal  method  the  vessel  is  approached  through  various 
incisions  ;  the  best  (Crampton)  (especially  if  it  is  desirable  to  apply  the  ligature  at 
the  highest  possible  point)  begins  at  the  tip  of  the  last  rib  and  extends  downward  to 
the  ilium  and  forward  to  the  anterior  superior  spinous  process.  The  abdominal 
muscles  and  transversalis  fascia  are  divided  at  the  lower  extremity  of  the  wound,  the 
peritoneum  separated  with  the  finger  from  the  iliac  fascia  in  a  direction  corresponding 
to  the  line  of  the  crista  ilii,  the  abdominal  muscles  severed  on  the  same  line,  and  the 
separation  of  the  peritoneum  continued  until  it  is  pushed  off  the  psoas  and  the  iliac 
vessels,  which  lie  on  the  inner  aspect  of  that  muscle.  The  ureter  is  raised  with  the 
peritoneum  and  remains  attached  to  it. 

The  artery  may  be  similarly  approached  through  an  incision  placed  just  above 
Poupart's  ligament  and  very  like  that  used  for  the  exposure  of  the  external  iliac.  The 
needle  is  passed  from  the  vein — i.  e. ,  from  left  to  right — in  ligating  the  right  common 
iliac,  and  from  right  to  left  if  the  vessel  of  the  left  side  is  the  subject  of  operation. 

The  collateral  circulation  is  carried  on  from  above  the  ligature  by  (a)  the  inter- 
nal mammary;  (<5)  the  superior  hemorrhoidal;  (Y)  the  lumbar;  (d)  the  middle 
sacral  ;  and  (e)  the  pudic  and  obturator  of  the  opposite  side,  anastomosing  respect- 
ively with  (a)  the  deep  epigastric  ;  (£)  the  middle  hemorrhoidal  (internal  iliac)  ;  (c) 
the  deep  circumflex  iliac  ;  and  (<?)  the  pudic  and  obturator  of  the  other  side  (i.e., 
the  side  of  the  ligature)  from  below. 

THE    INTERNAL    ILIAC   ARTERY. 

The  internal  iliac  artery  (a.  hypogastrica)  (Fig.  724)  arises  from  the  common 
iliac  and  passes  almost  directiy  downward  in  front  of  the  sacro-iliac  articulation  into 
the  pelvis.  Opposite  the  upper  border  of  the  great  sacro-sciatic  foramen  it  divides 
into  two  main  stems,  the  anterior  and  posterior  divisions,  from  which  branches  of 
distribution  are  given  off. 

Relations. — Posteriorly  the  internal  iliac  artery  is  covered  by  peritoneum  and 
is  crossed  obliquely  by  the  ureter.  More  anteriorly  the  vessel  of  the  right  side  is  in 
relation  with  some  coils  of  the  ileum,  while  that  of  the  left  side  is  in  relation  to  the 
upper  part  of  the  rectum.  Posteriorly  each  artery  rests  upon  the  upper  part  of  the 
external  iliac  vein,  which  separates  it  from  the  inner  border  of  the  psoas  muscle,  and  is 
accompanied  throughout  its  course  by  the  internal  iliac  vein. 

Branches. — From  the  main  stem  of  the  artery,  before  its  division,  there  arises 

(I)  the  ilio-lumbar  artery,  and  from  its  posterior  division  (2)  the  lateral  sacrals, 
usually  two  in  number,  and  (3)  the  gluteal.  From  the  anterior  division  there  are 
given  off  a  hypogastric  axis,  which  divides  into  (4)  the  sitperior  vesical,  (5)  inferior 
vesical,  and  (6)  prostatic  or  vaginal  branches,  and  (7)  the  vesiculo-defere7itial  or 
uterine  artery,  and,  in  addition,  (8)  the  obturator  and  (9)  middle  hemorrhoidal 
arteries,  the  main  stem  terminating  by  dividing  into   (10)  the  internal  pudic  and 

(II)  sciatic  arteries. 

Variations. — The  internal  iliac  arteries  represent  the  proximal  part  of  the  fcetaLumbilical 
or  hypogastric  arteries  which  return  the  blood  from  the  fcetus  to  the  placenta.  During  intra- 
uterine life  these  vessels  are  large  and  appear  to  be  the  continuation  of  the  common  iliacs,  pass- 
ing forward  beneath  the  peritoneum  to  the  lateral  walls  of  the  bladder  and  thence  upward  upon 
the  anterior  abdominal  wall  to  the  umbilicus,  and  thence  in  the  substance  of  the  umbilical  cord 
to  the  placenta.  After  birth  the  arteries  diminish  in  size,  and  those  portions  of  them  which  pass 
across  the  lateral  walls  of  the  urinary  bladder  and  up  the  abdominal  wall  become  converted  into 
solid  fibrous  cords  which  persist  throughout  life  and  are  known  as  the  obliterated  hypogastric 


THE    INTERNAL    ILIAC    ARTERY.  809 

arteries.  The  portions  of  the  arteries  which  remain  patent  form  the  main  stems  of  the  internal 
iliacs,  the  hypogastric  axes  and  the  superior  vesical  arteries  ;  what  are  spoken  of  as  the  main 
stems  of  the  anterior  divisions  of  the  internal  iliacs  are  really  the  common  trunks  by  which 
the  sciatic  and  internal  pudic  arteries  arise  from  the  hypogastric. 

In  the  arrangement  of  the  branches  of  the  fcetal  hypogastric  arteries  four  types  may 
be  recognized,  and  corresponding  to  each  of  these  is  an  arrangement  of  the  adult  internal 
iliac  branches.  Leaving  out  of  consideration  for  the  present  the  smaller  branches,  the  first 
type  is  that  in  which  two  large  trunks  arise  from  the  hypogastric,  the  posterior  one  being 
the   gluteal   and   the  anterior  a  trunk  which  divides  into  the  pudic  and  sciatic.     The  adult 

Fig.  724. 


Left  dorsal  artery  of  p 
Left  corp 


Dissection  of  pelvis  of  male,  showing  right  internal  iliac  artery  and  its  branches. 


condition  which  results  from  this  arrangement  is  that  described  above,  the  main  stem  of  the 
internal  iliac  appearing  to  divide  into  two  divisions,  from  the  anterior  of  which  the  hypogastric 
axis  arises. 

The  second  type  is  that  in  which  the  three  large  vessels  arise  independently  from  the  hypo- 
gastric, the  resulting  adult  condition  closely  resembling  that  produced  from  the  first  type,  except 
that  the  hypogastric  axis  seems  to  arise  from  the  internal  pudic,  the  separation  of  the  anterior 
division  into  its  two  terminal  branches  occurring  high  up. 

The  third  type  is  that  in  which  the  gluteal  and  sciatic  arteries  arise  by  a  common  trunk 
from  the  hypogastric,  the  pudic  remaining  distinct.  In  the  adult,  in  such  cases,  the  anterior 
division  gives  rise  to  the  hypogastric  axis  and  the  internal  pudic,  the  sciatic  arising  from  the 
posterior  division. 

Finally,  in  the  fourth  type,  which  is  of  rare  occurrence,  all  three  large  vessels  arise  from  a 
common  stem,  in  which  case  there  will  be  no  apparent  separation  of  the  adult  internal  iliac  into 
an  anterior  and  a  posterior  division. 


Sio 


HUMAN    ANATOMY. 


The  variations  of  the  smaller  branches,  which  are  quite  numerous,  will  be  considered  in 
connection  with  their  description.  It  may  be  pointed  out,  however,  that,  since  the  superior 
vesical  artery  is  the  persistent  portion  of  the  original  hypogastric  artery  and  primarily  the 
direct  continuation  of  the  hypogastric  axis,  some  of  the  visceral  branches  which  normally 
arise  from  the  axis  may  take  their  origin  from  the  superior  vesical.  Furthermore,  vessels  which 
embryologically  arise  from  one  or  other  of  the  great  branches  of  the  hypogastric  may,  on  account 
of  the  variations  in  the  origin  of  these,  come  to  arise  from  the  hypogastric  axis. 

Practical  Considerations. — The  internal  iliac  artery  is  almost  never  the  seat 
of  aneurism.  It  has  been  ligated  for  hemorrhage,  for  gluteal  and  sciatic  aneurism, 
and  in  the  treatment  of  inoperable  pelvic  growths.  It  may  be  approached  intrape?-i- 
toneally  by  the  same  incision  and  the  same  general  procedure  as  employed  in 
ligation  of  the  common  iliac  (q.v.).      The  vein  lies  behind  and  to  the  inner  side,  and 

Fig.  725. 


Diagram  illustrating  four  types  of  arrangement  of  branches  from  hypogastric  (internal  iliac)  artery  :  ci,ei, 
ii,  common,  external  and  interna]  iliac  artery  ;  il,  ilio-lumbar ;  Is,  lateral  sacral;  g,  gluteal;  5,  sciatic  ;  ipy 
internal  pudic  ;  ha,  hypogastric  axis. 

by  reason  of  its  size  and  its  close  proximity  to  the  vessel  must  be  very  carefully  dealt 
with.  The  needle  should  be  passed  from  within  outward.  The  relation  of  the  ureter, 
which  crosses  the  vessel  obliquely  from  without  inward  and  downward,  and  of  the 
hypogastric  plexus  should  be  borne  in  mind. 

In  the  extraperitoneal  method  the  incision  and  procedure  are  just  as  in  extra- 
peritoneal ligation  of  the  external  iliac  (page  819),  except  that  the  separation  of  the 
peritoneum  from  the  iliac  fascia  must  be  carried  to  a  higher  level. 

The  collateral  circulation  is  carried  on  chiefly  through  (a)  the  inferior  mesen- 
teric ;  (£)  the  circumflex  iliac  ;  (c)  the  middle  sacral  ;  (d)  the  deep  femoral  ;  (e)  the 
obturator  and  internal  pudic  of  the  opposite  side,  all  of  which  carry  blood  from  above 
the  ligature  into  (a)  the  hemorrhoidal  branches  of  the  internal  iliac  ;  (b)  the  ilio- 
lumbar ;  (c)  the  lateral  sacral  ;  (d  )  the  sciatic  and  gluteal  ;  and  (V)  the  corresponding 
vessels  of  the  other  side  (z.  e. ,  the  side  of  the  ligature). 

1.  The  Ilio-Lumbar  Artery. — The  ilio-lumbar  artery  (a.  ilio-lumbalis) 
(Fig.  724)  is  most  frequently  given  off  from  the  main  stem  of  the  internal  iliac, 
shortly  above  its  separation  into  the  anterior  and  posterior  divisions.  Not  infre- 
quently, however,  it  is  a  branch  of  the  posterior  division.  It  passes  upward  and 
outward  towards  the  brim  of  the  pelvis,  crossing  in  front  of  the  lumbo-sacral  nerve 
and  behind  the  external  iliac  artery,  beyond  which  it  passes  beneath  the  psoas 
muscle.      On  reaching  the  crest  of  the  ilium  it  divides  into  two 


Branches. — (a)  The  lumbar  branch  (ramus  lumbalis)  is  directed  upward  and  backward  be- 
neath the  psoas  and  supplies  that  muscle  and  the  quadratus  lumborum.  It  sends  a  spinal  branch 
(ramus  spinalis)  through  the  intervertebral  foramen  between  the  last  lumbar  and  first  sacral 
vertebrae,  and  anastomoses  with  branches  of  the  last  lumbar  artery. 

(b)  The  iliac  branch  (ramus  iliacus)  passes  outward  beneath  the  psoas  and  ramifies  upon 
the  surface  of  the  iliacus  muscle,  supplying  it  and  usually  giving  off  a  nutrient  branch  to  the 
ilium. 

2.  The  Lateral  Sacral  Arteries. — The  lateral  sacral  arteries  (aa.  sacrales 
laterales")  (Fig.  724)  are  usually  two  in  number,  and  arise  from  the  posterior  division  of 
the  internal  iliac.  The  superior  one  passes  downward  and  inward  to  the  first  anterior 
sacral  foramen,  and  passes  through  it  to  supply  the  spinal  membranes  and  anastomose 


THE    INTERNAL    ILIAC    ARTERY.  811 

with  the  other  spinal  arteries.  The  inferior  artery  passes  at  first  inward  and  then 
downward  upon  the  surface  of  the  sacrum,  parallel  to  the  middle  sacral  artery,  with 
which  it  anastomoses  at  the  tip  of  the  coccyx  and  also,  by  delicate  transverse  branches, 
opposite  each  sacral  vertebra.  Opposite  each  anterior  sacral  foramen  that  it  passes 
— i.e. ,  opposite  the  second,  third,  and  fourth — it  gives  off  a  branch  (ramus  spinalis  J 
which  enters  the  foramen  and  behaves  like  the  spinal  branch  of  the  superior  artery. 
In  its  downward  course  the  inferior  lateral  sacral  lies  to  the  outer  side  of  the  sacral 
portion  of  the  sympathetic  cord  and  crosses  the  slips  of  origin  of  the  pyriformis 
muscle. 

Variations. — Very  frequently  the  two  lateral  sacral  arteries  arise  by  a  common  stem,  and 
occasionally  the  branch  which  enters  the  second  anterior  sacral  foramen  arises  independently. 
In  all  probability  the  longitudinal  stem  of  the  inferior  artery  is  to  be  regarded  as  having  been 
formed  by  the  direct  anastomosis  of  ascending  and  descending  twigs  from  the  lateral  branches 
of  the  middle  sacral,  each  of  which  is  serially  ""homologous  with  the  lumbar  and  intercostal  arte- 
ries. The  process  is  similar  to  what  has  occurred  in  the  formation  of  the  vertebral  artery 
(page  721 ). 

3.  The  Gluteal  Artery. — The  gluteal  artery  (a.  glutaea  superior)  (Fig.  727)  is 
the  continuation  of  the  posterior  division  of  the  internal  iliac.  It  is  the  largest  of  all 
the  branches  of  that  vessel,  and  passes  backward  between  the  lumbo-sacral  cord  and 
the  first  sacral  nerve  to  the  upper  border  of  the  great  sacro-sciatic  foramen.  It  passes 
through  the  foramen,  in  company  with  the  superior  gluteal  nerve,  above  the  pyriformis 
muscle,  and  soon  after  making  its  exit  from  the  pelvis  divides  into  a  superficial  and  a 
deep  branch. 

Branches. — (a)  The  superficial  branch  (ramus  superior)  soon  divides  into  a  number  of 
branches  which  enter  the  upper  portion  of  the  gluteus  maximus,  some  supplying  that  muscle, 
while  others  traverse  it  to  supply  the  skin  over  the  upper  part  of  the  gluteal  region.  One 
branch,  larger  than  the  others,  passes  outward  along  the  upper  border  of  the  origin  of  the 
gluteus  medius  almost  to  the  anterior  superior  spine  of  the  ilium,  anastomosing  with  branches  of 
the  external  circumflex  iliac  artery. 

(b)  The  deep  branch  (ramus  inferior)  soon  divides  into  two  branches,  (aa)  The  superior 
branch  passes  outward  along  the  upper  border  of  the  gluteus  minimus  almost  to  the  anterior 
inferior  spine  of  the  ilium,  where,  under  cover  of  the  tensor  vaginae  femoris,  it  anastomoses 
with  the  descending  branch  of  the  external  circumflex  iliac  ;  it  sends  branches  to  both  the  glu- 
teus medius  and  minimus,  (bb)  The  inferior  branch  passes  outward  and  downward,  over  the 
surface  of  the  gluteus  medius,  towards  the  greater  trochanter  of  the  femur,  and  gives  branches 
to  both  the  gluteus  medius  and  minimus  and  to  the  hip-joint. 

4.  The  Superior  Vesical  Artery. — The  superior  vesical  artery  (a.  umbilicalis) 
(Fig.  724)  represents  the  original  main  stem  of  the  fcetal  hypogastric  artery,  and 
consequently  takes  its  origin  from  the  hypogastric  axis  and  is  continuous  anteriorly 
with  the  fibrous  cord  which  represents  the  obliterated  hypogastric  artery  (Fig.  728). 
It  passes  forward,  beneath  the  peritoneum,  towards  the  urinary  bladder,  and  as  it 
approaches  that  structure  gives  off  branches  to  it  (aa.  vesicales  superiores)  which  ramify 
over  its  surface  and  sides  and  supply  its  upper  and  middle  portions.  They  anasto- 
mose below  with  branches  of  the  prostatic  and  inferior  vesical  arteries. 

Variations. — Not  infrequently  an  accessory  branch  arising  from  the  superior  vesical  is  dis- 
tributed to  the  middle  and  lower  portions  of  the  bladder,  forming  what  has  been  termed  the 
middle  vesical  artery  (Fig.  724). 

5.  The  Inferior  Vesical  Artery. — The  inferior  vesical  artery  (a.  vesicalis 
inferior)  (Fig.  724)  may  arise  from  the  hypogastric  axis,  from  the  anterior  division  of 
the  internal  iliac  below  the  axis,  from  the  middle  hemorrhoidal,  or  quite  frequently 
from  the  prostatic.  It  descends  towards  the  lower  portion  of  the  bladder,  supplying 
the  base  and  neck  of  that  structure,  and  also  sending  branches  to  the  prostate  gland 
and  the  seminal  vesicles  in  the  male.  It  anastomoses  with  branches  of  the  prostatic 
and  superior  vesical  arteries. 

Variations. — The  inferior  vesical  is  usually  a  rather  slender  branch,  and  may  be  replaced 
by  vesical  branches  from  the  prostatic  or  by  branches  of  the  superior  vesical. 


HUMAN    ANATOMY. 


6a.  The  Prostatic  Artery. — The  prostatic  artery  arises  either  from  the  hypo- 
gastric axis,  or,  more  usually,  from  a  trunk  common  to  it  and  the  inferior  vesical  or  the 
middle  hemorrhoidal.  It  passes  downward,  forward,  and  inward  to  the  lateral  surface 
of  the  prostate  gland,  and  sends  branches  into  the  interior  of  that  structure  and  also 
to  the  base  of  the  bladder,  anastomosing  with  branches  of  the  inferior  vesical  artery. 

6b.  The  Vaginal  Artery. — The  vaginal  artery  (a.  vaginalis)  (Fig.  726),  the 
homologue  of  the  prostatic  artery,  arises  either  from  the  hypogastric  axis,  more  usually 
from  a  trunk  common  to  it  and  the  inferior  vesical  or  middle  hemorrhoidal,  or  from 
the  anterior  division  of  the  internal  iliac,  below  the  hypogastric  axis.  It  passes  down- 
ward and  inward  towards  the  lower  part  of  the  sides  of  the  vagina,  where  it  divides  into 
numerous  branches  which  ramify  over  the  anterior  and  posterior  surfaces  of  that  organ, 
anastomosing  with  the  corresponding  branches  of  the  artery  of  the  other  side.  It  also 
anastomoses  above  with  the  cervical  branches  of  the  uterine  artery  and  below  with  the 
perineal  branches  of  the  internal  pudic.  By  these  anastomoses  there  is  usually  formed 
along  the  median  line  of  both  the  anterior  and  posterior  surfaces  of  the  vagina  a  more 
or  less  regular  vessel  which  is  known  as  the  azygos  artery  of  the  vagina. 


Fig.  726. 


Riylit  ureter 
Common  iliac  artery 


Dorsal  artery  of 


Artery  to  corpus 


Middle  hemorrhoidal  artery 


Artery  to  bulb  Vaginal  branch  Left  Vaginal  artery 

Arteries  of  female  pelvis,  seen  from  left  side. 

Variations. — The  vaginal  artery  occasionally  arises  from  a  common  trunk  with  the  uterine. 
Frequently,  as  a  result  of  its  precocious  division,' it  is  represented  by  two  or  more  vessels. 

■ja.  The  Vesiculo-Deferential  Artery. — The  vesiculo-deferential  artery 
fa.  deferentialis  )  usually  arises  from  the  hypogastric  axis,  but  sometimes  from  the 
proximal  part  of  the  superior  vesical  or  from  the  anterior  division  of  the  internal  iliac, 
below  the  hypogastric  axis.  It  passes  downward,  forward,  and  inward,  and,  crossing 
the  ureter,  gives  a  branch  to  the  vas  deferens  and  then  breaks  up  into  a  number  of  small 
branches  which  are  distributed  to  the  vesicula  seminalis.  The  deferential  branch, 
on  reaching  the  vas,  divides  into  an  ascending  and  a  descending  branch.  The  former 
passes  upward  along  the  vas  to  the  internarabdominal  ring  and  thence  through  the 
inguinal  canal  to  the  neighborhood  of  the  epididymis,  anastomosing  with  branches  of 
the  spermatic  artery.      The  descending  branch  accompanies  the  vas  to  the  prostate. 

76.  The  Uterine  Artery.— The  uterine  artery  (a.  uterina)  (Fig.  726)  corres- 
ponds to  the  vesiculo-deferential  and  has  a  similar  origin.  It  passes  atfirst  downward 
and  inward  upon  the  surface  of  the  levator  ani,  and  then  inward  in  a  tortuous  course 


THE    INTERNAL    ILIAC    ARTERY.  813 

along  the  base  of  the  broad  ligament  towards  the  neck  of  the  uterus.  Just  before 
reaching  the  uterus,  usually  about  2  cm.  (  ^  in. )  from  it,  the  artery  crosses  in  front 
of  the  ureter  and  then  bends  upward  between  the  two  layers  of  the  broad  ligament 
along  the  side  of  the  uterus.  Arrived  at  the  junction  of  the  Fallopian  tube  with  the 
uterus,  it  bends  outward  along  the  lower  border  of  the  tube,  and  then,  passing 
beneath  the  hilum  of  the  ovary,  terminates  by  inosculating  with  the  ovarian  artery. 
In  its  course  between  the  layers  of  the  broad  ligament  the  artery  is  accompanied 
by  the  large  uterine  veins,  which  almost  conceal  it,  and  both  artery  and  veins  are 
enclosed  in  a  rather  dense  sheath  of  areolar  tissue.  During  pregnancy  the  artery 
becomes  much  enlarged,  and  its  course,  as  well  as  that  of  its  branches,  becomes 
exceedingly  sinuous  and  even  spiral. 

Branches. — (a)  As  the  uterine  artery  crosses  the  renal  duct,  a  ureteral  branch  is  supplied 
to  the  ureter.     On  reaching  the  sides  of  the  uterus,  it  gives  off — 

(b)  One  or  several  cervical  branches.  These  pass  to  the  cervix  and  divide  into  numerous 
branches  which  supply  that  portion  of  the  uterus  and  the  upper  part  of  the  vagina.  They  are 
relatively  long  and  tortuous,  and  anastomose  below  with  the  branches  of  the  vaginal  arteries. 
Throughout  the  rest  of  its  course  along  the  sides  of  the  uterus  it  gives  off  numerous — 

(c)  Uterine  branches,  which,  although  tortuous,  yet  differ  from  the  cervical  branches  in 
being  rather  short.  They  pass  to  both  the  anterior  and  posterior  surfaces  of  the  uterus  and 
supply  its  body  and  fundus,  and  it  is  to  be  remarked  that  both  these  branches  and  the  cervical 
ones  diminish  rapidly  in  calibre  as  they  branch  upon  the  surface  of  the  uterus,  so  that  at  the 
middle  line  of  the  organ  only  exceedingly  minute  twigs  are  to  be  found. 

From  the  portion  of  the  artery  that  runs  outward  along  the  lower  border  of  the  Fallopian 
lube — 

(d)  Tubal  branches  (rami  tubarii)  are  given  off.  One  of  these,  much  stronger  than  the 
others,  arises  just  before  the  uterine  inosculates  with  the  ovarian  artery,  and  passes  outward 
along  the  tube  to  its  fimbriated  extremity,  sending  branches  to  it  through  its  entire  course. 

(e)  Ovarian  branches  (rami  ovarii)  to  the  ovary  are  finally  given  off  from  the  uterine 
artery  in  the  vicinity  of  its  anastomosis  with  the  ovarian. 

8.  The  Middle  Hemorrhoidal  Artery. — The  middle  hemorrhoidal  artery 
(a.  haemorrhoidalis  media)  (Fig.  726)  is  somewhat  variable  both  in  its  origin  and  in 
its  size.  It  arises  either  from  the  anterior  division  of  the  internal  iliac,  below  the 
hypogastric  artery,  or,  as  frequently  happens,  from  the  inferior  vesical  or  occasionally 
from  the  internal  pudic.  It  passes  along  the  lateral  surface  of  the  middle  portion  of 
the  rectum,  giving  off  branches  which,  in  addition  to  aiding  in  supplying  the  vagina 
and  communicating  with  the  vaginal  arteries,  anastomose  above  with  the  superior 
hemorrhoidal  from  the  inferior  mesenteric  and  below  with  the  inferior  hemorrhoidal 
from  the  internal  pudic. 

9.  The  Obturator  Artery. — The  obturator  artery  (a.  obturatoria)  (Fig.  724) 
arises  from  the  anterior  division  of  the  internal  iliac,  below  the  hypogastric  axis.  It 
passes  forward  along  the  lateral  wall  of  the  pelvis,  resting  upon  the  pelvic  fascia 
which  covers  the  upper  portion  of  the  internal  obturator  muscle,  and  having  the 
obturator  nerve  immediately  above  it  and  the  vein  below.  Just  before  reaching  the 
anterior  wall  of  the  pelvis  it  is  crossed  by  the  vas  deferens  in  the  male,  as  it  passes 
downward  from  the  internal  abdominal  ring,  and  then  it  pierces  the  pelvic  fascia  and 
makes  its  exit  from  the  pelvic  cavity  through  the  obturator  canal,  on  emerging  from 
which  it  divides  into  two  terminal  branches,  an  internal  and  an  external. 

Branches. —  Within  the  pelvis  the  obturator  artery  gives  off  several  small  branches,  of 
which  the  more  important  are — 

(a)  An  iliac  branch,  which  is  given  off  near  the  origin  of  the  obturator  and  passes  up  to 
the  iliac  fossa,  supplying  the  ilio-psoas  muscle,  giving  nutrient  branches  to  the  ilium  and  anasto- 
mosing with  the  iliac  branch  of  the  ilio-lumbar  artery. 

( />)  Muscular  branches,  which  are  distributed  to  the  obturator  internus  and  the  levator  ani. 

(r)  Vesical  branches,  which  pass  to  the  bladder  beneath  the  false  lateral  ligament  and 
anastomose  with  branches  from  the  superior  vesical  ;  and 

(d)  A  pubic  branch  (ramus  pubicus)  which  arises  just  before  the  artery  enters  the  obtu- 
rator canal  and  ascends  upon  the  posterior  surface  of  the  os  pubis  to  anastomose  above  with  the 
pubic  branch  of  the  deep  epigastric  artery. 

Outside  the  pelvis  the  obturator  artery  divides  into  an  external  and  an  internal  branch. 


8i4  HUMAN    ANATOMY. 

(e)  The  external  branch  passes  around  the  external  border  of  the  obturator  foramen, 
beneath  the  external  obturator  muscle,  and  terminates  by  anastomosing  with  the  internal  branch 
and  with  the  internal  circumflex  from  the  deep  femoral.     Near  its  origin  it  gives  off— 

(aa)  An  internal  branch,  which  passes  downward  on  the  posterior  surface  of  the  obturator 
membrane,  under  cover  of  the  internal  obturator  muscle,  to  the  tuberosity  of  the  ischium,  and 
it  also  gives  rise  to — 

(66)  An  aceta6ular  6ranch  (ramus  acetabuli),  which  passes  through  the  cotyloid  notch  and 
supplies  the  fatty  tissue  occupying  the  bottom  of  the  acetabulum. 

(/)  The  internal  branch  runs  around  the  inner  border  of  the  obturator  foramen,  beneath 
the  external  obturator  muscle,  and  terminates  by  anastomosing  with  the  external  branch. 

Variations. — The  obturator  artery  varies  greatly  in  its  origin,  and  these  variations  may  be 
divided  into  two  groups,  according  as  the  origin  is  from  the  internal  or  the  external  iliac  system 
of  arteries.  While  the  origin  of  the  vessel  from  the  anterior  division  of  the  internal  iliac  is  the 
most  frequent,  yet,  when  compared  with  all  the  variations  taken  together,  it  occurs  in  some- 
what less  than  50  per  cent,  of  cases.  Of  other  origins  from  the  system  of  the  internal  iliac  there 
may  be  mentioned  those  from  the  main  stem  of  the  iliac  before  its  division,  from  its  posterior 
division,  and  from  the  gluteal  artery.  Furthermore,  its  origin  may  occur  from  either  the  sciatic 
or  the  internal  pudic  artery,  although  such  cases  are  rare. 

More  frequent  and  of  greater  importance  from  the  practical  stand-point  is  the  origin 
from  the  external  iliac  system,  which  occurs  in  about  30  per  cent,  of  cases.  In  the  immense 
majority  of  such  cases— in  almost  twenty-nine  out  of  every  thirty — the  origin  is  from  the  deep 
epigastric  artery,  being  in  the  remaining  cases  from  the  external  iliac  distal  to  the  deep  epigas- 
tric or  from  the  upper  part  of  the  common  femoral  artery.  Undoubtedly  the  primary  relations 
of  the  obturator  artery  are  with  the  internal  iliac  system  of  vessels,  and  the  origin  from  the  ex- 
ternal iliac  system  is  to  be  regarded  as  due  to  the  secondary  enlargement  of  an  anastomosis  nor- 
mally present  and  the  diminution  or  inhibition  of  the  original  stem  of  the  obturator.  Possibilities 
for  such  a  process  are  furnished  by  the  normal  anastomosis  between  the  pubic  branches  of  the 
obturator  and  the  external  circumflex,  and  all  gradations  may  be  found  between  the  normal  ar- 
rangement and  the  complete  replacement  of  the  original  intrapelvic  portion  of  the  obturator  by 
the  pubic  anastomosis. 

The  origin  of  the  obturator  from  the  deep  epigastric  artery  (  Fig.  728)  becomes  of  importance 
from  the  fact  that,  in  order  to  reach  its  point  of  exit  from  the  pelvis,  the  obturator  canal,  the 
vessel  must  come  into  intimate  relations  with  the  crural  ring,  and  may  thus  add  an  important 
complication  to  the  operation  for  the  relief  of  femoral  hernia  (page  1775).  There  are  three  possi- 
ble courses  for  the  vessel  in  relation  to  the  ring  :  ( 1)  it  may  pass  inward  from  its  origin  over  the 
upper  border  of  the  ring  and  then  curve  downward  and  inward  along  the  free  border  of  Gim- 
bernat's  ligament  to  reach  the  obturator  canal  ;  (2)  it  may  bend  downward  abruptly  at  its  origin 
and  pass  in  an  almost  direct  course  to  the  obturator  canal,  passing  over  the  inner  surface  of 
the  external  iliac  vein,  and  therefore  down  the  outer  border  of  the  crural  ring ;  or  (3)  it  may 
pass  directly  across  the  ring.  As  regards  the  relative  frequency  of  each  of  these  courses  it  is 
interesting  to  note  that,  according  to  observations  made  by  Jastschinski,  the  course  along  the 
outer  border  of  the  ring  is  much  the  most  frequent,  occurring  in  60  per  cent,  of  cases,  and  being 
more  frequent  in  females  than  in  males.  The  course  across  the  ring  occurs  in  about  22.5  per 
cent,  of  cases,  and  is  again  more  frequent  in  females  than  in  males  ;  while  the  course  along  the 
free  edge  of  Gimbernat's  ligament  occurs  in  only  17.5  per  cent,  of  cases,  and  is  more  common 
in  males  than  in  females.  The  differences  in  the  two  sexes  are  associated  with  the  differences  in 
the  form  of  the  pelvis  and  of  the  obturator  foramen. 

Practical  Considerations. — The  gluteal  and  sciatic  arteries  have  not  uncom- 
monly been  affected  by  aneurism  which  has  shown  itself  as  a  pulsating  compressible 
tumor  in  the  gluteal  region,  often  with  a  bruit,  and  usually  causing  pain  over  the 
nates,  extending  down  the  posterior  aspect  of  the  thigh — from  pressure  on  the  sciatic 
nerve — and  causing  lameness. 

The  gluteal  aneurism  is  situated  somewhat  farther  back  in  the  buttock  than  the 
sciatic,  which  is  apt  to  be  farther  forward  and  downward,  near  the  gluteo-femoral 
crease  (Agnew). 

Either  of  these  vessels  or  the  internal  pudic  may  require  ligature  on  account  of 
stab-wounds.  Serious  hemorrhage  from  a  wound  in  the  upper  part  of  the  gluteus 
maximus,  i.e. ,  a  little  below  a  line  from  the  posterior  superior  iliac  spine  to  the  top 
of  the  great  trochanter,  is  likely  to  proceed  from  the  gluteal  artery.  Lower,  nearer 
to  the  fold  of  the  buttock,  it  may  come  from  the  sciatic.  The  gluteal  may  be  tied 
through  an  incision  made  along  the  line  just  mentioned,  from  the  posterior  superior 
spine  to  the  trochanter.  With  the  thigh  in  inward  rotation,  the  junction  of  the  middle 
with  the  upper  third  of  that  line  indicates  about  the  point  where  the  gluteal  artery 
comes  out  through  the  sciatic  notch.  The  fibres  of  the  gluteus  maximus  are  sepa- 
rated, the  muscle  is  relaxed  by  full  extension  of  the  thigh,  and  the  upper  bony  margin 


THE    INTERNAL    ILIAC    ARTERY.  815 

of  the  sciatic  notch  is  felt  for  with  the  finger  through  the  interspace  between  the  pyri- 
formis  and  the  gluteus  medius.  The  artery  may  be  found  as  it  turns  over  the  bony 
tip  of  the  sacro-sciatic  foramen  towards  the  dorsum  ilii.  The  sciatic  artery  may  be 
reached  through  the  same  incision,  the  finger  then  being  carried  below  the  pyriformis 
muscle,  when  the  spine  of  the  ischium  and  the  sharp  edge  of  the  sacro-sciatic  ligament 
will  serve  as  landmarks. 

The  point  of  emergence  of  both  the  sciatic  and  internal  pudic  arteries  is  indicated 
with  sufficient  accuracy  by  the  junction  of  the  lower  and  middle  thirds  of  a  line  drawn 
from  the  tuberosity  of  the  ischium  to  the  posterior  superior  spine  of  the  ilium.  The 
incision  employed  should  follow  the  direction  of  the  fibres  of  the  greater  gluteal 
muscle. 

10.  The  Sciatic  Artery. — The  sciatic  artery  (a.  glutaea  inferior)  (Fig.  727)  is 
one  of  the  two  terminal  branches  of  the  anterior  division  of  the  internal  iliac.  It  lies 
at  first  internal  and  posterior  to  the  internal  pudic  artery,  and  is  directed  downward 
and  backward  towards  the  lower  part  of  the  great  sacro-sciatic  foramen,  passing  usu- 
ally below  the  fourth  sacral  nerve.  It  makes  its  exit  from  the  pelvis  through  the  great 
sacro-sciatic  foramen,  below  the  pyriformis  muscle,  and  bends  downward  beneath 
the  gluteus  maximus.  It  crosses  the  internal  pudic  artery  at  about  the  level  of  the 
spine  of  the  ischium,  and  in  the  rest  ot  its  course  lies  to  the  inner  side  of  the  great 
sciatic  nerve.  It  descends  upon  the  gemelli,  the  internal  obturator,  and  the  quad- 
ratus  femoris,  and,  after  giving  off  its  principal  branches,  is  continued  down  the  leg 
as  a  slender  vessel,  the  comes  nervi  ischiadici. 

Branches. —  Within  the  pelvis  the  sciatic  artery  gives  off  some  small  and  inconstant  branches 
to  the  internal  obturator  and  pyriformis  muscles  and  to  the  trunks  of  the  sacral  pelvis. 
Outside  the  pelvis  it  gives  rise  to  several  larger  branches. 

(a)  The  coccygeal  branch  passes  inward  and  pierces  the  great  sacro-sciatic  ligament  and 
the  gluteus  maximus  near  its  origin,  terminating  in  the  tissues  over  the  lower  part  of  the  sacrum 
and  coccyx. 

(b)  Muscular  branches,  variable  in  number,  pass  to  the  neighboring  muscles,  some  of 
them  being  continued  beneath  the  quadratus  femoris  to  reach  the  capsule  of  the  hip-joint. 
One  branch  somewhat  larger  than  the  rest  can  frequently  be  seen  entering  the  deep  surface  of 
the  gluteus  maximus  in  company  with  the  inferior  gluteal  nerve  ;  it  supplies  the  muscle  and 
forms  anastomoses  with  the  gluteal  artery. 

(c)  An  anastomotic  branch  passes  transversely  outward,  usually  beneath  the  great  sciatic 
nerve,  towards  the  greater  trochanter  of  the  femur.  It  gives  twigs  to  the  gemelli  muscles,  and 
in  the  neighborhood  of  the  trochanter  anastomoses  with  the  terminal  branch  of  the  internal  cir- 
cumflex, with  the  transverse  branch  of  the  external  circumflex,  and,  below,  with  the  first  per- 
forating artery,  completing  what  is  termed  the  crucial  anastomosis. 

( d  )  Cutaneous  branches,  variable  in  number,  wind  around  the  lower  border  of  the  gluteus 
maximus  in  company  with  branches  of  the  small  sciatic  nerve,  and  supply  the  integument  over 
the  lower  part  of  the  gluteal  region. 

(e)  The  a.  comes  nervi  ischiadici  is  the  continuation  of  the  sciatic  artery.  It  is  a  long, 
slender  branch  which  passes  downward  upon  or  in  the  substance  of  the  great  sciatic  nerve,  sup- 
plying it  and  anastomosing  with  the  perforating  branches  of  the  profunda  femoris. 

Variations. — The  occasional  origin  of  the  sciatic  from  the  gluteal  artery  or  from  the 
hypogastric  axis  has  already  been  described  in  connection  with  the  variations  of  the  internal 
iliac  (page  808).  Occasionally  it  has  a  double  origin  from  both  the  gluteal  and  the  anterior 
division  of  the  internal  iliac,  or  it  may  be  double,  owing  to  the  existence  of  stems  from  each  of 
these  vessels  which  pursue  independent  courses. 

In  addition  to  its  normal  branches,  it  may  give  origin  to  the  lateral  sacral,  the  inferior 
vesical,  and  the  uterine  or  the  middle  hemorrhoidal.  Especial  interest  attaches  to  the  comes 
nervi  ischiadici,  which  occasionally  traverses  the  entire  length  of  the  thigh  to  unite  below  with 
the  popliteal  artery.  It  represents  the  original  main  stem  of  the  sciatic  artery,  of  which  the 
popliteal  was  primarily  the  continuation,  the  connection  of  that  artery  with  the  femoral,  and  the 
subsequent  diminution  of  the  sciatic  being  secondary  arrangements  (page  824). 

11.  The  Internal  Pudic  Artery. — The  internal  pudic  artery  (a.  pudenda 
interna)  (Fig.  727)  is  the  other  terminal  branch  of  the  anterior  division  of  the  internal 
iliac.  It  is  directed  downward  in  front  of  the  sciatic  artery  to  the  lower  portion  of  the 
great  sacro-sciatic  foramen,  where  it  makes  its  exit  from  the  pelvis,  passing  between 


Si6 


HUMAN   ANATOMY. 


Fig.  727. 


Superior  gluteal  artery. 


Gluteus  medius,  cut 

Upper  ramus  of  deep  branch  of 

superior  gluteal  artery 
Gluteus  minimus 

Muscular  branch  of  sup.  gluteal 
Lower  ramus  of  deep  branch 
Pyriformis  [of  sup.  gluteal 


Tendon  of  obturator  inl 

Articular  branch  from  ; 

branch  of  internal  c 

Articular  branch  of  scit 

Anastomotic  branch 


Comes  nervi  ischiadici 
Gluteus  maximus 

From  external  circumflex 
Superior  perforating  artery 

From  external  circumflex 

Vastus  externus 

Middle  perforating  artery    ^ 

Inferior  perforating  artery     0 
Biceps— short  head 
Biceps — long  head 


nal  articular  artery 


External  sural  artery 

Inferior  external  articular  artery 


Arteries  of  gluteal  region  and  posterior  surface  of  right  thigh. 


THE   INTERNAL   ILIAC   ARTERY.  817 

the  pyriformis  and  coccygeus  muscles.  It  then  bends  forward,  under  cover  of  the 
gluteus  maximus,  and,  curving  beneath  the  spine  of  the  ischium,  passes  through  the 
lesser  sacro-sciatic  notch  to  enter  the  ischio-rectal  fossa.  Its  course  is  then  forward 
along  the  lateral  wall  of  the  fossa,  lying  with  its  accompanying  vein  and  the  pudic 
nerve  in  a  fibrous  canal  known  as  Alcock1  s  canal,  formed  by  a  splitting  of  the  obtu- 
rator fascia  near  its  lower  border.  At  the  anterior  portion  of  the  ischio-rectal  fossa 
the  artery  perforates  the  triangular  ligament  of  the  perineum  and  passes  forward 
between  the  two  layers  composing  that  structure,  finally  perforating  the  superficial 
layer  and  becoming  the  dorsal  artery  of  the  penis  (or  clitoris). 

Branches. — In  the  pelvic  and  gluteal  portions  of  its  course  the  internal  pudic,  as  a  rule, 
gives  off  only  slender  muscular  branches  to  the  neighboring  muscles.  In  its  ischio-rectal  por- 
tion its  branches  are  more  important. 

(a)  The  inferior  hemorrhoidal  arteries  (aa.  haemorrhoidales  inferiores),  usually  two  in  num- 
ber, but  frequently  only  one,  which  early  divides  into  two  or  three  stems,  arise  from  the  internal 
pudic,  just  after  it  has  traversed  the  lesser  sacro-sciatic  foramen.  They  perforate  the  inner  wall 
of  Alcock' s  canal  and  pass  through  the  fat-tissue  which  occupies  the  ischio-rectal  fossa  towards 
the  lower  part  of  the  rectum.  They  give  branches  to  the  ischio-rectal  fat-tissue,  to  the  sphincter 
and  levator  ani,  to  the  gluteus  maximus,  to  the  skin  over  the  ischio-rectal  and  anal  regions,  and 
to  the  lower  part  of  the  rectum,  anastomosing  above  with  the  middle  hemorrhoidal  branches  of 
the  internal  iliac. 

(5)  The  superficial  perineal  artery  (a.  perinei)  arises  just  before  the  internal  pudic  enters  the 
space  between  the  layers  of  the  triangular  ligament  of  the  perineum.  It  is  at  first  directed 
almost  vertically  downward,  but  quickly  bending  around  the  posterior  border  of  the  superficial 
transverse  muscle  of  the  perineum,  near  its  origin  from  the  ischial  tuberosity,  it  is  directed  for- 
ward and  inward  in  the  interval  between  the  ischio-cavernosus  and  bulbo-cavernosus  muscles. 
In  this  portion  of  its  course  it  is  covered  only  by  the  superficial  perineal  fascia  and  the  integu- 
ment, and  passes  forward  to  be  distributed  to  the  posterior  portion  of  the  scrotum  in  the  male 
and  to  the  labia  majora  in  the  female.  In  its  course  it  gives  off  numerous  cutaneous  branches 
as  well  as  branches  to  the  neighboring  muscles.  One  of  these  latter,  usually  somewhat  larger 
than  the  rest,  passes  inward  towards  the  median  line,  beneath  the  superficial  transverse  muscle 
of  the  perineum,  which  it  supplies,  as  also  the  bulbo-cavernosus  and  external  sphincter  ani. 
This  is  what  has  been  termed  the  transverse  artery  of  the  perineum.  It  anastomoses  at  the 
central  point  of  the  perineum  with  its  fellow  of  the  opposite  side,  with  other  branches  from  the 
superficial  perineal  artery  anteriorly  and  with  branches  of  the  inferior  hemorrhoidals  posteriorly. 

In  its  perineal  portion  also  the  internal  pudic  gives  off  important  branches. 

(c)  The  artery  to  the  bulb  (a.  bulbi  urethrae  or  a.  bulbi  vestibuli)  arises  from  the  internal 
pudic  a  short  distance  after  it  has  entered  the  deep  perineal  interspace.  It  is  a  relatively 
large  vessel  in  the  male,  and  passes  almost  horizontally  inward  towards  the  median  line. 
Before  reaching  this,  however,  it  perforates  the  superficial  layer  of  the  triangular  ligament, 
enters  the  substance  of  the  bulbus  urethrce  about  15  mm.  in  front  of  its  posterior  extremity, 
and  is  distributed  to  that  structure  and  to  the  posterior  third  of  the  corpus  spongiosum  and 
urethra.  In  the  female  it  is  of  a  lesser  calibre  than  in  the  male,  and  is  distributed  to  the  bulbus 
vestibuli. 

(d)  The  urethral  artery  (a.  urethralis)  arises  usually  some  distance  anteriorly  to  the  artery 
of  the  bulb,  and,  like  it,  is  directed  medially,  and  penetrates  the  superficial  layer  of  the  tri- 
angular ligament  to  enter  the  substance  of  the  corpus  spongiosum.  It  reaches  the  corpus 
spongiosum  just  behind  the  symphysis  pubis,  where  the  two  corpora  cavernosa  come  together 
to  form  the  penis,  and  is  continued  forward  in  the  spongiosum  to  the  glans.  It  is  a  somewhat 
inconstant  branch,  and  is  quite  small  in  the  female. 

(e)  The  artery  of  the  corpus  cavernosum  (a.  profunda  penis  s.  clitoridis)  arises  from  the 
internal  pudic,  just  posterior  to  the  lower  border  of  the  symphysis  pubis,  and  is  directed 
outward  towards  the  bone.  It  penetrates  the  superficial  layer  of  the  triangular  ligament 
close  to  its  attachment  to  the  pubic  ramus,  and  enters  the  corpus  cavernosum  at  about  the 
junction  of  its  middle  and  posterior  thirds.  It  passes  to  the  centre  of  the  corpus  and  there 
divides  into  a  posterior  branch  which  supplies  blood  to  the  posterior  third  of  that  structure, 
and  an  anterior  one  which  distributes  to  its  anterior  two-thirds.  It  is  much  smaller  in  the 
female  than  in  the  male. 

(_/")  The  dorsal  artery  of  the  penis  or  clitoris  (a.  dorsalis  penis  s.  clitoridis)  is  the  continua- 
tion of  the  main  stem  of  the  internal  pudic  beyond  the  origin  of  the  artery  to  the  corpus  cav- 
ernosum. It  penetrates  the  superficial  layer  of  the  triangular  ligament  near  its  apex,  and  passes 
upward  in  the  suspensory  ligament  of  the  penis  or  clitoris  to  the  dorsal  surface  of  that  organ, 
along  which  it  passes,  lying  to  the  side  of  the  median  line  and  separated  from  its  fellow  of  the 
opposite  side  by  the  single  median  dorsal  vein.     Laterally  to  it  is  situated  the  dorsal  nerve  of 

52 


818  HUMAN    ANATOMY. 

the  penis  (or  clitoris),  and  still  more  laterally  the  deep  external  pudic  branch  of  the  common 
femoral  artery.  On  reaching  the  glans,  it  forms  an  anastomotic  circle  around  the  base  of  that 
structure,  uniting  with  its  fellow  of  the  opposite  side.  Throughout  its  course  it  gives  branches  to 
the  corpus  cavernosum  and  the  integument  of  the  penis  or  the  prepuce  of  the  clitoris. 

Variations. — The  occasional  origin  from  the  internal  pudic  of  the  inferior  vesical,  middle 
hemorrhoidal,  and  uterine  arteries  has  already  been  noted.  The  internal  pudic,  instead  of 
passing  out  of  the  pelvis  by  the  great  sacro-sciatic  foramen,  may  be  directed  forward  upon  the 
floor  of  the  pelvis  and  pass  out  beneath  the  pubic  symphysis  to  become  the  dorsal  artery  of  the 
penis.  More  frequently  this  course  is  taken  by  an  accessory  internal  pudic  which  arises  from 
the  pudic  in  cases  where  this  vessel  appears  to  arise  from  the  hypogastric  axis,  a  condition 
which  results  in  the  early  division  of  the  common  stem  from  which  the  sciatic  and  internal 
pudic  arteries  normally  arise. 

The  artery  of  the  bulb  may  arise  opposite  the  ischial  tuberosity  and  pass  obliquely  forward 
and  medially  across  the  ischio-rectal  fossa,  and  in  some  cases  it  passes  at  first  directly  across 
towards  the  anus  and  then  bends  forward  to  reach  the  bulb. 

The  dorsal  artery  of  the  penis  or  clitoris  occasionally  unites  with  its  fellow  of  the  opposite 
side  to  form  a  single  median  artery,  or  the  two  arteries  of  opposite  sides  may  be  united  by  trans- 
verse anastomoses.  Sometimes  a  third  vessel  arises  either  directly  from  the  anterior  division 
of  the  internal  iliac  or  from  the  obturator,  even  when  this  vessel  takes  its  origin  from  the  deep 
epigastric. 

Anastomoses  of  the  Internal  Iliac. — The  internal  iliac  makes  anastomoses 
with  branches  of  the  abdominal  aorta  and  of  the  external  iliac,  and  with  its  fellow  of 
the  opposite  side,  and  it  is  through  these  connections  that  the  collateral  circulation 
may  be  established. 

Of  branches  communicating  with  the  abdominal  aortic  system  there  are  the 
hemorrhoidal  branches  which  anastomose  with  the  superior  hemorrhoidal  from  the 
inferior  mesenteric,  the  uterine  which  anastomoses  with  the  ovarian,  and  the  lateral 
sacrals  which  anastomose  with  the  middle  sacral.  Communications  with  the  system 
of  the  external  iliac  are  through  the  sciatic  with  branches  of  the  profunda  femoris, 
through  the  ilio-lumbar  and  gluteal  with  the  external  and  internal  circumflex  iliacs, 
and  through  the  obturator  with  the  deep  epigastric  through  the  pubic  branches.  The 
anastomoses  across  the  middle  line  occur  between  the  vesical,  prostatic  (vaginal), 
obturator,  and  internal  pudic  branches. 

THE    EXTERNAL    ILIAC    ARTERY. 

The  external  iliac  artery  (a.  iliaca  externa)  (Figs.  724,  728)  extends  from  the 
bifurcation  of  the  common  iliac,  opposite  the  sacro-iliac  articulation,  to  a  point  beneath 
Poupart'  s  ligament  midway  between  the  anterior  superior  spine  of  the  ilium  and  the 
symphysis  pubis.  It  there  becomes  the  femoral  artery.  In  the  adult  the  external 
iliac  is  usually  larger  than  the  internal  and  is  directed  more  nearly  in  the  line  of  the 
common  iliac,  downward,  forward,  and  outward  along  the  brim  of  the  true  pelvis. 

Relations. — Anteriorly,  the  artery  is  covered  by  peritoneum  and  is  enclosed, 
together  with  the  vein,  in  a  moderately  dense  sheath  derived  from  the  subperitoneal 
tissue  and  termed  Abernethf  s  fascia.  By  the  peritoneum  it  is  separated  on  the 
right  side  from  the  terminal  portion  of  the  ileum  and  sometimes  from  the  vermiform 
appendix,  and  on  the  left  from  the  sigmoid  colon.  Near  its  origin  it  is  crossed  by 
the  ovarian  vessels  in  the  female  and  sometimes  by  the  ureter  ;  near  its  lower  end  it 
is  crossed  obliquely  by  the  genital  branch  of  the  genito-crural  nerve  and  by  the  deep 
epigastric  vein.  Some  lymph-nodes  are  also  found  resting  upon  its  anterior  surface. 
Posteriorly,  it  rests  upon  the  iliac  fascia,  which  separates  it  from  the  psoas  muscle  , 
medially,  it  is  crossed  near  its  lower  end  by  the  vas  deferens  in  the  male  and  the 
round  ligament  of  the  uterus  in  the  female,  and  is  accompanied  throughout  its 
course  by  the  external  iliac  vein,  which  lies,  however,  on  a  slightly  posterior  plane. 
Laterally,  it  is  in  relation  to  the  genito-crural  nerve. 

Branches. — In  addition  to  some  small  twigs  to  the  psoas  muscle  and  to  the 
neighboring  lymphatic  glands,  the  external  iliac  gives  origin  to  (1)  the  deep  epigastric 
and  (2)  the  deep  circumflex  iliac  arteries. 

Variations. — The  external  iliac  varies  considerably  in  length,  according  to  the  level  at 
which  the  abdominal  aorta  and  the  common  iliac  bifurcate.  Independently  of  this,  however, 
and  especially  in  aged  individuals,  it  is  frequently  longer  than  is  necessary  to  reach  in  a  direct 


THE    EXTERNAL    ILIAC    ARTERY.  819 

line  from  the  common  iliac  to  beneath  Poupart's  ligament,  and  in  such  cases  it  makes  a  more 
or  less  pronounced  bend  which  may  dip  below  the  brim  of  the  pelvis.  In  the  embryo  it  is  a 
comparatively  small  vessel,  the  main  supply  of  the  lower  limb  being  through  the  sciatic,  which 
is  continuous  below  with  the  popliteal  (page  823).  Occasionally  this  condition  is  retained,  the 
artery  then  terminating  by  becoming  the  deep  instead  of  the  common  femoral. 

In  addition  to  the  usual  branches  it  may  give  off  the  obturator  (page  814),  or  an  accessory 
deep  epigastric  or  deep  circumflex  iliac.  Or  branches  usually  arising  from  the  common  femoral, 
such  as  the  superficial  external  pudic  or  even  the  profunda  femoris,  may  arise  from  it. 

Practical  Considerations. — The  external  iliac  artery  is  occasionally  the  seat 
of  aneurism,  and  such  tumors  have  been  mistaken  for  malignant  growths  or  for 
abscess.  A  swelling  with  expansile  pulsation  and  bruit  can  usually  be  found  in  the 
line  of  the  vessel  near  the  brim  of  the  pelvis,  and  the  patient  will  be  unable  to  extend 
freely  the  thigh  or  the  trunk,  and  will  lean  forward  in  walking  or  standing  to  relieve 
,  the  ilio-psoas  from  pressure.  There  is  apt  to  be  pain  in  the  groin  and  down  the  front 
of  the  thigh  from  pressure  on  the  anterior  crural  nerve,  or  on  the  crural  branch 
of  the  genito-crural. 

It  may  be  imperfectly  compressed  just  above  its  termination  at  the  middle  of 
Poupart's  ligament,  but,  as  is  the  case  with  the  common  and  internal  iliacs,  the 
circulation  through  it  is  better  controlled  by  pressure  on  the  abdominal  aorta.  The 
line  of  the  vessel  extends  from  a  point  half-way  between  the  pubic  symphysis  and  the 
anterior  superior  spinous  process  to  a  point  a  little  below  and  to  the  left  of  the 
umbilicus.  The  course  of  the  external  iliac  corresponds  to  the  lower  third  of  this 
line,  the  upper  two-thirds  representing  the  line  of  the  common  iliac. 

Ligation  of  the  vessel  has  been  done  for  aneurism  of  the  common  femoral,  for 
hemorrhage,  and  as  a  palliative  in  malignant  growths  or  in  elephantiasis  of  the 
extremity. 

Like  the  other  iliacs,  it  may  be  approached  by  either:  (1)  the  intraperitoneal; 
or  (2)  the  extraperitoneal  route. 

1.  The  incision  should  be  made  in  the  semilunar  line,  and  will  thus  cross  the 
line  of  the  vessel  obliquely.  Its  lower  end  should  reach  Poupart's  ligament.  Its 
length  will  vary  (with  the  thickness  of  the  abdominal  wall)  from  three  inches  to  four 
inches.  The  superficial  circumflex  ilii  and  the  deep  epigastric  arteries  may  require 
ligation.  The  intestines  are  displaced  upward.  At  the  left  side  the  sigmoid  flexure, 
and  on  the  right  the  termination  of  the  ileum,  may  be  found  in  close  relation  to  the 
vessel.  On  both  sides  the  spermatic  vessels  cross  it,  and  their  distention  (analogous 
to  that  of  the  mesenteric  vessels  spoken  of  in  connection  with  ligation  of  >  the  left 
common  iliac)  (page  808),  when  deprived  of  their  peritoneal  support,  has  been  noted 
(Makins). 

The  peritoneum  over  the  vessel — on  the  left  side  possibly  a  part  of  the  sigmoid 
mesocolon — is  divided  parallel  with  the  long  axis  of  the  artery,  and  the  needle  is 
passed  from  the  vein. 

2.  Ligation  by  the  extraperitoneal  method — still  preferred  by  many  surgeons  in 
the  case  of  this  vessel — is  done  through  an  incision  parallel  with  Poupart's  ligament, 
but  slightly  convex  downward,  beginning  one  inch  above  the  anterior  superior  spinous 
process  of  the  ilium  and  ending  at  the  outer  pillar  of  the  external  abdominal  ring. 
After  dividing  the  abdominal  muscles  and  the  transversalis  fascia,  the  separation  of 
the  peritoneum  from  the  iliac  fascia  is  begun  near  the  outer  extremity  of  the  wound, 
where  the  subperitoneal  areolar  tissue  is  more  abundant  and  the  connection  of  the 
peritoneum  and  the  fascia  less  intimate.  After  the  detachment  has  been  effected 
(chiefly  by  means  of  a  finger),  the  vessel  is  exposed  with  the  vein  lying  behind 
it  above  and  to  the  inner  side  near  Poupart's  ligament,  and  the  anterior  crural 
nerve  some  distance  to  the  outer  side.  The  needle  should  be  passed  from  within 
outward. 

The  collateral  circnlatio?i  is  carried  on  from  above  the  ligature  by  (a)  the  lumbar; 
(6)  the  obturator;  (c)  the  sciatic;  (d)  the  gluteal;  (e)  the  internal  pudic;  and  (/") 
the  internal  mammary  and  lower  intercostals  anastomosing  respectively  with  (a)  the 
deep  circumflex  iliac;  (6)  the  internal  circumflex;  (c)  the  perforating  (profunda); 
(d)  the  external  circumflex;  (e  )  the  external  pudic  (femoral);  and  (_/)  the  deep 
epigastric  from  below. 


820 


HUMAN   ANATOMY. 


i.  The  Deep  Epigastric  Artery. — The  deep  epigastric  artery  (a.  epigastrica 
inferior)  (Fig.  728)  arises  from  the  anterior  surface  of  the  external  iliac,  a  short 
distance  above  where  it  passes  beneath  Poupart's  ligament.  Immediately  after  its 
origin  it  bends  downward  and  medially  to  pass  the  lower  border  of  the  internal 
abdominal  ring,  being  crossed  in  this  situation  by  the  vas  deferens  in  the  male  and  the 
round  ligament  of  the  uterus  in  the  female.  It  then  curves  upward  and  medially 
along  the  medial  border  of  the  internal  abdominal  ring  and  ascends  along  the  outer 
border  of  Hesselbach's  triangle  (page  526),  of  which  it  forms  the  lateral  boundary. 
Throughout  this  portion  of  its  course  it  lies  between  the  peritoneum  and  the  trans- 
versalis  fascia,  but  at  about  the  level  of  the  fold  of  Douglas,  in  the  posterior  surface 
of  the  sheath  of  the  rectus  abdominis,  it  pierces  the  fascia  and  ascends  between  the 
muscle  and  the  posterior  layer  of  its  sheath,  eventually  entering  the  substance  of  the 
muscle,  where  it  terminates  by  anastomosing  with  the  superior  epigastric  branch  of 
the  internal  mammary  artery. 

Branches. — Throughout  its  course  the  deep  epigastric  artery  gives  off  a  number  of  branches. 

(a)  The  cremasteric  branch  (a.  spermatica  externa  in  the  male,  a.  ligamenti  teretis  in  the 

female)  is  given  off  a  short  distance  beyond  the  origin  of  the  deep  epigastric  and  accompanies 

Fig.  72S. 

Anterior  superior  spine  of  ilium 


External  il 

External  iliac  vein 
Upper  part  of  left  broad 

liniment  passing 

leniM  iliac  artery  ; 

fundibulo-pelvic    ligament 
Common  il' 


Round  liiinnient  of 


umflex  iliac  ar 
Deep  epigastri 

1, 

' 

-Rectus  abdominis, 
turned  d"\wi\\.inl 
with   part  of   ab- 
dominal wall 

-< ibturator  artery 

fr-r- — Xji 

_ — — -~ 

Crural  ring 

Urachus 

Vesical   branch  of 
obturator 


Cut  edge  of  broad  ligament 


Portion  ot  left  half  pelvis  of  female  subject  viewed  from  above  and  right 
side,  showing  obturator  artery  arising  from  deep  epigastric. 


the  spermatic  cord  or  round  ligament  of  the  uterus  through  the  inguinal  canal.  In  the  male  it 
supplies  the  cremaster  muscle  and  the  spermatic  cord,  anastomosing  with  the  spermatic  and 
deferential  arteries,  and  in  the  female,  in  which  it  is  small,  it  supplies  the  lower  part  of  the 
round  ligament  and  terminates  in  the  labia  majora  by  anastomosing  with  branches  of  the  super- 
ficial perineal  artery. 

(6)  The  pubic  branch  (ramus  pubicus)  arises  a  short  distance  beyond  the  cremasteric  and, 
passing  either  above  or  below  the  femoral  ring,  passes  downward  and  inward  upon  the  posterior 
surface  of  the  os  pubis,  where  it  may  anastomose  with  the  pubic  branch  of  the  obturator.  It  is 
by  the  anastomosis  and  enlargement  of  this  artery  and  the  pubic  branch  of  the  obturator 
that  the  latter  vessel  comes  to  arise  so  frequently  from  the  deep  epigastric  (page  814).  And 
even  when  the  obturator  has  its  normal  origin,  the  anastomosis  may  render  the  pubic  branch  of 
the  deep  epigastric  of  considerable  importance  in  the  operation  for  the  relief  of  femoral  hernia. 

(c)  Muscular  branches,  variable  in  number,  are  given  off,  for  the  most  part,  from  the 
outer  side  of  the  artery  and  supply  the  muscles  of  the  abdominal  walls.  They  anastomose  with 
branches  of  the  lower  intercostal  and  lumbar  arteries. 

(d)  Cutaneous  branches,  also  variable  in  number,  pierce  the  rectus  and  the  anterior  wall 
of  its  sheath  and  supply  the  skin  of  the  abdomen  near  the  median  line. 


THE    FEMORAL    ARTERY.  821 

Variations. — The  deep  epigastric  may  arise  from  the  external  iliac  higher  up  than  usual, — 
as  high,  indeed,  as  a  point  6  cm.  (2^  in.)  above  Poupart's  ligament.  In  such  cases  it  passes 
downward  and  forward  upon  the  anterior  surface  of  the  external  iliac  to  reach  the  abdominal 
wall.  It  may  also  arise  below  its  usual  position, — that  is  to  say,  from  the  common  femoral 
artery, — and  it  may  be  given  off  from  a  trunk  common  to  it  and  the  deep  circumflex  iliac. 

In  addition  to  being  frequently  the  origin  of  the  obturator  (page  814),  it  may  be  given  off 
from  that  artery  as  a  result  of  the  enlargement  of  the  anastomosis  of  the  pubic  branches  of  the 
two  arteries  and  the  subsequent  degeneration  of  the  proximal  portion  of  the  deep  epigastric. 
Occasionally  it  gives  origin  to  the  dorsal  artery  of  the  penis  or  clitoris,  an  arrangement  which 
also  results  from  its  relation  to  the  obturator,  from  which  this  artery  sometimes  arises. 

2.  The  Deep  Circumflex  Iliac  Artery. — The  deep  circumflex  iliac  artery  (a. 
circumflexa  ilium  profunda)  (Fig.  728)  arises  from  the  outer  surface  of  the  external 
iliac,  a  little  below  the  deep  epigastric.  It  passes  outward  along  the  lower  border 
of  Poupart's  ligament,  enclosed  in  a  sheath  formed  by  the  iliac  fascia,  and  opposite  the 
anterior  superior  spine  of  the  ilium,  or  it  may  be  a  little  beyond  it,  divides  into  an 
ascending  and  a  horizontal  branch. 

Branches. — In  its  course  it  gives  branches  to  the  muscles  of  the  abdominal  wall  and,  at 
the  anterior  superior  spine  of  the  ilium,  to  the  upper  part  of  the  sartorius  and  to  the  tensor 
vaginae  femoris. 

(a)  The  ascending  branch  pierces  the  transversalis  muscle  and  ascends  directly  upward 
between  that  muscle  and  the  internal  oblique.  It  sends  branches  to  both  these  muscles,  as  well 
as  to  the  external  oblique  and  the  integument,  and  terminates  by  anastomosing  with  the  lumbar 
arteries  and  with  the  tenth  aortic  intercostal  (subcostal). 

(b)  The  horizontal  branch  continues  the  course  of  the  main  stem.  It  lies  at  first  a  little 
below  the  crest  of  the  ilium,  but  later  ascends  and  perforates  the  transversalis  muscle,  passing 
onward  upon  the  crest  of  the  ilium  between  that  muscle  and  the  internal  oblique.  It  gives  off 
branches  which  supply  the  abdominal  muscles  and  anastomose  with  the  lumbar  arteries,  and 
terminates  by  anastomosing  with  the  lumbar  branches  of  the  ilio-lumbar. 

Variations. — The  deep  circumflex  iliac  artery  may  arise  from  a  common  stem  with  the  deep 
epigastric  or  from  the  upper  part  of  the  common  femoral  artery.  Not  infrequently  it  gives  rise 
to  a  branch,  shortly  after  its  origin,  which  passes  upward  upon  the  anterior  abdominal  wall,  un- 
derneath the  transversalis  fascia,  parallel  and  lateral  to  the  deep  epigastric.  This  lateral  epi- 
gastric artery,  as  it  has  been  termed,  is  occasionally  of  considerable  size,  in  which  case  the 
ascending  branch  of  the  circumflex  iliac  may  be  more  or  less  reduced.  It  may  ascend  to  the 
level  of  the  umbilicus  or  even  above  that  point,  sending  branches  to  the  muscles  of  the  abdom- 
inal wall. 

Anastomoses  of  the  External  Iliac— Opportunities  for  the  development  of 
a  collateral  circulation  after  ligation  of  the  external  iliac  artery  are  afforded  by  the 
anastomoses  of  its  deep  epigastric  branch  with  the  superior  epigastric  branch  of  the 
internal  mammary,  with  the  lower  aortic  intercostals,  and  with  the  lumbar  arteries. 
The  deep  circumflex  iliac  also  makes  connections  with  the  lumbar  arteries  by  its 
ascending  and  lateral  epigastric  branches,  and,  furthermore,  anastomoses  with  the 
ilio-lumbar  and  gluteal  branches  of  the  internal  iliac.  Another  connection  with  the 
internal  iliac  system  is  made  by  the  anastomoses  of  the  pubic  branches  of  the  deep 
epigastric  and  obturator  arteries. 

Anastomoses  between  branches  of  the  internal  iliac  and  the  femoral  arteries  are 
also  of  importance  in  this  connection,  but  will  be  described  in  connection  with  the 
femoral  artery  (page  831). 

THE    FEMORAL    ARTERY. 

The  femoral  artery  (a.  femoralis)  (Figs.  729,  732)  is  the  continuation  of  the 
external  iliac  below  Poupart's  ligament.  Its  course  is  almost  vertically  downward, 
with  a  slight  inclination  inward  and  backward,  and  may  be  indicated  by  a  line  drawn 
from  a  point  in  Poupart's  ligament  midway  between  the  symphysis  pubis  and  the 
anterior  superior  spine  of  the  ilium  to  the  adductor  tubercle  upon  the  inner  condyle 
of  the  femur,  when  the  thigh  is  flexed  upon  the  pelvis  and  rotated  outward.  It  ter- 
minates at  about  the  junction  of  the  middle  and  lower  thirds  of  the  thigh,  where  it 
passes  through  the  adductor  magnus  muscle,  close  to  the  inner  surface  of  the  femur, 
to  become  the  popliteal  artery. 


8z: 


HUMAN    ANATOMY. 


Fig.  729. 


Sartorius,  stump 

Anterior  crural  nerve 

Superficial  circumflex  iliac 

Rectus  femoris,  stump 

Iliacus 

Ascending  branch  of 

external  circumflex 
Deep  femoral  artery 

External  circumflex  artery 
Transverse  branch  of 

external  circumflex 
Descending  branch  of 

external  circumflex 


Rectus  femoris.  cut 


Vastus  extern 


Superficial  epigastric 

1  artery 
Deep  external  pudic 

§ -Superficial  ex- 
ternal pudic 
Femoral  vein 


Adductor  longus 


Aponeurotic  roof  of  Hunter's  canal 


Anastomotic.-!  magna— 

superficial  branch 
Inner  hamstring  muscles 


Vastus  interims 


From  anastomotica  magna 


Tendon  of  sartonus 
Anastomotica  magn 


Arteries  of  front  of  thigh  ;  superficial  dissection. 


THE    FEMORAL   ARTERY.  823 

Relations. — In  its  uppermost  part,  for  a  distance  of  about  3  cm.  (1%  in.),  the 
femoral  artery,  together  with  the  accompanying  vein,  is  enclosed  within  a  sheath 
formed  by  a  prolongation  of  the  transversalis  and  iliac  fasciae  below  Poupart'  s  liga- 
ment. This  femoral  sheath  is  funnel-shaped  and  is  divided  by  partitions  into  three 
compartments,  the  most  lateral  of  which  contains  the  artery,  the  middle  one  the 
femoral  vein,  while  the  medial  one  forms  what  is  termed  the  femoral  or  crural  canal 
(page  625).  Below,  the  walls  of  the  sheath  gradually  pass  over  into  the  con- 
nective tissue  which  invests  the  vessels. 

In  the  upper  half  of  its  course  the  femoral  artery  lies  in  Scarpa's  triangle  (page 
639),  while  in  its  .lower  half  it  is  contained  within  a  space  known  as  Hunter1  s  canal, 
situated  between  the  adductor  magnus  and  vastus  medialis  muscles  and  covered  in 
by  the  sartorius. 

In  Scarpa's  triangle  the  relations  of  the  artery  are  as  follows.  Anteriorly,  it 
is  covered  by  the  integument,  the  superficial  fascia,  and  the  fascia  lata,  the  inner 
margin  of  the  attenuated  portion  of  the  latter  fascia,  which  is  known  as  the  cribriform 
fascia,  overlapping  it  at  about  the  junction  of  its  upper  and  middle  thirds.  Superficial 
to  the  fascia  lata  are  some  of  the  superficial  inguinal  lymphatic  nodes  and  the  superfi- 
cial circumflex  iliac  vein,  while  deeper  and  resting  upon  the  upper  part  of  the  artery  is 
the  crural  branch  of  the  genito-crural  nerve,  and  towards  the  apex  of  the  triangle  the 
internal  cutaneous  nerve.  Posteriorly,  the  artery  rests  upon  the  tendon  of  the  ilio- 
psoas muscle,  which  separates  it  from  the  capsule  of  the  hip-joint,  and  lower  down  it 
lies  upon  the  pectineus  muscle.  Throughout  the  lower  part  of  the  triangle  it  is  sep- 
arated from  the  adductor  longus  muscle  by  the  femoral  vein  and  by  the  deep  femoral 
artery  and  vein.  Medially,  it  is  in  relation  above  with  the  femoral  vein  and  below 
with  the  adductor  longus;  laterally,  with  the  ilio-psoas  muscle  and  the  leash  of 
nerves  formed  from  the  anterior  crural  nerve. 

In  Hunter's  canal  the  artery  lies  beneath  the  sartorius  muscle  and  is  crossed 
obliquely  from  without  inward  by  the  long  saphenous  nerve.  Posteriorly  it  rests  upon 
the  adductor  longus  and  the  adductor  magnus,  and  also  upon  the  femoral  vein  which, 
below,  comes  to  lie  somewhat  laterally  as  well  as  posterior  to  it  and  is  firmly  united 
to  the  artery  by  dense  connective  tissue.  To  the  inner  side  of  the  artery  is  the  ad- 
ductor longus  above  and  the  adductor  magnus  below,  while  to  its  outer  side,  and 
partly  overlapping  it,  is  the  vastus  internus. 

Branches. — In  Scarpa's  triangle  the  femoral  artery  gives  off  (1)  the  stiper- 
ficial  epigastric,  (2)  the  superficial  circumflex  iliac,  (3)  the  superficial  external 
pudic,  (4)  the  deep  external  pudic,  (5)  the  profunda  femot is,  and  (6)  muscular 
branches.  In  Hunter's  canal  it  gives  off  additional  muscular  branches  and,  just 
before  perforating  the  adductor  muscle,  (7)  the  anastomotica  magna. 

The  profunda  femoris  so  much  surpasses  in  size  the  other  branches  of  the  femoral 
that  the  latter  artery  is  frequently  regarded  as  bifurcating  at  the  point  where  this 
vessel  arises.  The  portion  of  the  artery  above  the  bifurcation  is  then  termed  the 
common  femoral,  while  its  continuation  through  Scarpa's  triangle  and  Hunter's  canal 
is  known  as  the  superficial  femoral. 

Variations. — A  comparative  study  of  the  arteries  of  the  thigh  reveals  the  fact  that  the  exist- 
ence of  a  well-developed  femoral  artery  forming  the  main  blood-channel  for  the  leg  is  a  condi- 
tion characteristic  of  the  mammalia.  In  the  lower  vertebrate  groups  the  sciatic  is  the  principal 
artery  of  the  thigh,  extending  throughout  the  whole  length  of  its  flexor  surface  and  becoming 
continuous  below  with  the  popliteal  artery,  the  femoral  artery  being  comparatively  insignificant 
and  terminating  as  the  profunda  femoris.  The  peculiar  course  of  the  mammalian  femoral,  start- 
ing, as  it  does,  as  an  artery  of  the  extensor  surface  of  the  limb  and  later  perforating  the  adductor 
magnus  to  become  continuous  with  the  popliteal  upon  the  flexor  surface,  is  to  be  regarded, 
therefore,  as  a  secondary  arrangement,  and  its  history  is  somewhat  as  follows. 

While  the  sciatic  is  still  the  principal  vessel  Of  the  thigh  and  retains  its  connection  with  the 
popliteal  below,  a  branch  is  given  off  from  the  femoral  which  accompanies  the  long  saphenous 
nerve  through  Hunter's  canal  and  down  the  inner  surface  of  the  cms,  having  in  this  lower  por- 
tion of  its  course  a  superficial  position  corresponding  with  that  of  the  nerve.  Near  the  lower 
part  of  Hunter's  canal  this  vessel,  which  is  known  as  the  saphenous  artery,  gives  off  a  branch 
which  perforates  the  adductor  magnus  and  unites  with  the  sciatic,  producing  an  arrangement 
which,  in  various  degrees  of  development,  may  be  regarded  as  characteristic  of  the  mammalia 
as  a  group.  In  man,  however,  the  process  goes  a  step  further  in  that,  correlatively  with  an 
enlargement  of  the  anastomosis  between  the  saphenous  and  the  sciatic,  there  is  a  diminution  of 
the  main  stem  of  the  latter  vessel,  so  that  eventually  it  becomes  reduced  to  the  slender  a.  comes 


824  HUMAN    ANATOMY. 

nervi  ischiadic!  which  loses,  as  a  rule,  its  continuity  with  the  popliteal.  That  artery  now  appears 
to  be  the  continuation  of  the  saphenous  (femoral),  since  there  occurs  a  degeneration  of  the 
saphenous  below  the  point  where  the  anastomosing  branch  is  given  off.  These  changes  are 
shown  diagrammatically  in  Fig.  74S,  (page  S49)  from  which  it  will  be  seen  that  the  femoral  artery 
below  the  origin  of  the  profunda  is  the  upper  part  of  the  original  a.  saphena,  the  continuation  of 
that  vessel  down  the  crus  being  represented  only  by  the  superficial  branch  of  the  anastomotica 
magna. 

The  principal  variations  which  are  shown  by  the  femoral  artery  are  associated  with  these 
changes  which  it  has  passed  through  in  its  development,  and  represent  a  cessation  of  the  devel- 
opment at  one  stage  or  other  of  its  progress.  Thus,  as  already  pointed  out  (page  S15),  the 
comes  nervi  ischiadici  may  remain  the  principal  vessel  of  the  thigh,  the  femoral  terminating  in 
the  profunda  femoris.  Or  the  development  may  proceed  to  the  formation  of  the  a.  saphena, 
which  may  arise  either  immediately  above  the  profunda  femoris,  in  such  case  the  superficial 
femoral  being  wanting  and  the  comes  nervi  ischiadici  still  well  developed,  or  else  from  the  lower 
part  of  the  femoral,  just  before  it  pierces  the  adductor  muscle.  From  this  point  the  vessel, 
when  fully  developed,  is  continued  onward  with  the  long  saphenous  nerve  between  the  adductor 
magnus  and  the  vastus  medialis,  and  below  the  knee-joint  perforates  the  crural  fascia  and  is 
continued  superficially  down  the  inner  side  of  the  crus,  accompanying  the  long  saphenous  nerve 
and  vein  to  the  internal  malleolus,  where  it  makes  connections  with  the  posterior  tibial  artery 
and  may  sometimes  persist  as  a  branch  of  that  vessel. 

In  addition  to  these  anomalies,  the  femoral  artery  frequently  gives  off  branches  which  nor- 
mally arise  from  other  vessels.  Thus  it  may  give  rise  to  the  deep  epigastric  or  the  deep  cir- 
cumflex iliac,  normally  branches  of  the  external  iliac,  or  to  the  external  or  internal  circumflex, 
normally  branches  of  the  profunda  femoris.  It  has  also  been  observed  to  give  origin  to  the  ilio- 
lumbar artery. 

Practical  Considerations. — The  femoral  artery  is  more  often  wounded  than 
the  brachial  on  account  of  the  position  of  its  upper  half — in  Scarpa's  triangle — on 
the  anterior  surface  of  the  limb,  and  of  its  relatively  more  intimate  relation  to  the 
bone  at  its  lower  end.  In  the  latter  region  it  has  been  opened  by  spicules  of  necrotic 
bone.  Next  to  the  popliteal,  it  is  more  frequently  the  subject  of  aneurism  than  any 
other  external  arterial  trunk.  On  account  of  the  close  relation  of  the  lymphatic 
glands  in  and  near  the  groin,  the  vessel  has  been  opened  by  ulceration  and  sloughing 
in  bubo  or  in«carcinoma,  and  has  been  involved  in  sarcomatous  growths.  The  same 
relation  has  caused  the  aneurism  to  be  mistaken  for  a  glandular  abscess,  an  error 
which  has  occurred  oftener  in  connection  with  this  vessel  than  with  any  other. 

Compression  of  the  femoral  artery  has  yielded  very  satisfactory  results  in  the 
treatment  of  popliteal  aneurism.  The  pressure  is  best  applied  in  a  direction  backward 
and  outward  just  below  the  inferior  edge  of  Poupart's  ligament  where  the  vessel  can 
be  flattened  against  the  brim  of  the  pelvis — the  upper  margin  of  the  acetabulum — 
just  outside  the  ilio-pectineal  eminence,  only  a  very  thin  portion  of  the  ilio-psoas 
muscle  intervening.  A  little  lower,  a  more  fleshy  portion  of  that  muscle  separates  it 
from  the  head  of  the  femur,  and  yet  lower  the  artery  has  back  of  it,  the  still  less 
resistant  mass  of  the  pectineus  and  adductor  brevis  muscles,  and  more  force  will  be 
required  to  obliterate  its  lumen.  At  the  apex  of  Scarpa's  triangle  the  pressure  must 
be  directed  backward  and  somewhat  more  outward,  and  a  little  lower  still  more 
directly  outward,  the  artery  at  these  places  being  compressed  against  the  femur,  the 
vastus  internus  intervening. 

Extreme  flexion  of  the  thigh  upon  the  trunk  will  occlude  the  femoral,  and  has 
been  used  successfully  in  the  cure  of  popliteal  aneurism  and  for  the  temporary  arrest 
of  hemorrhage. 

Ligation  of  the  vessel  may  be  done  :  1.  Between  Poupart's  ligament  and  the 
origin  of  the  profunda — the  common  femoral  {vide  supra).  2.  At  the  apex  of 
Scarpa's  triangle.      3.    In  Hunter's  canal. 

1.  The  common  femoral  is  rarely  ligated  except  as  a  preliminary  to  some  forms 
of  hip-joint  amputations,  or  for  the  relief  of  hemorrhage.  In  aneurism  of  the  upper 
portion  of  the  superficial  femoral  the  external  iliac  is  ordinarily  preferred  because  of 
(a)  the  possibility  of  a  high  origin  of  the  profunda.  The  common  femoral  is  normally 
only  about  one  and  a  half  inches  in  length.  If  its  bifurcation  occurs  above  the  usual 
level — the  most  common  variation — the  ligature  would  be  in  dangerously  close 
proximity  to  so  large  a  trunk.  (6)  The  presence  of  a  number  of  smaller  branches — 
the  deep  epigastric  and  deep  circumflex  iliac  coming  off  immediately  above  Poupart's 
ligament,  the  superficial  epigastric,  circumflex  iliac,  and  external  pudic,  the  deep 
external  pudic,  and  occasionally  one  of  the  circumflex  arteries  (especially  the  internal), 


THE    FEMORAL   ARTERY. 


825 


arising  from  the  femoral.  This  circumstance  likewise  interferes  with  the  firmness  and 
security  of  the  clot  formation  after  ligature,  (c)  The  fact  that  ligature  of  the 
common  femoral  cuts  off  the  chief  blood-supply  to  the  lower  limb  also  militates 
against  its  selection  and  leads  to  the  choice  of  the  superficial  femoral  whenever  pos- 
sible, so  as  to  permit  the  profunda  and  its  branches  to  maintain  a  sufficient  vascular 
current.  The  incision  should  be  begun  on  the  abdomen  a  little  above  Poupart's 
ligament,  midway  between  the  anterior  superior  spine  and  the  symphysis  pubis,  and 
extend  downward  to  about  two  inches  below  the  ligament  in  the  line  of  the  vessel — 
vide  supra.  The  structures  to  be  avoided  in  approaching  the  artery  are  the  glands 
and  veins  that  lie  in  the  fat  over  the  cribriform  fascia,  the  superficial  epigastric  artery 
and,  when  the  sheath  is  exposed,  the  crural  branch  of  the  genito-crural  nerve  lying 
upon  it  near  its  outer  side.  The  vein  is  in  close  contact  with  the  inner  side  of  the 
artery.      The  needle  should  be  passed  from  within  outward. 

The  collateral  circulation  will  be  carried  on  from  above  the  ligature  by  (a)  the 
internal  pudic  (from  the  internal  iliac  J ;  (b)  the  gluteal  and  sciatic  (from  the  same 
vessel)  ;  (c)  the  deep  cir- 
cumflex iliac,  from  the  Fig.  730. 
external  iliac ;  ( d)  the  ob- 
turator, and  (<?)  the  comes 
nervi  ischiadici,  anasto- 
mosing respectively  with 
(«)  the  superficial  and 
deep  external  pudic  ;  (6) 
the  circumflex  and  per- 
forating arteries  ;  (r)  the 
external  circumflex  ;  {d) 
the  internal  circumflex  ; 
and  (<?)  the  perforating,  all 
from  either  the  common, 
superficial,  or  deep  fem- 
oral. 

2.  At  the  apex  of 
Scarpa's  triangle  an  inci- 
sion with  its  centre  at  the 
apex  of  the  triangle  is 
made  on  the  line  of  the 
vessel,  the  thigh  being  ab- 
ducted and  rotated  out- 
ward, the  hip  a  little 
flexed,  the  knee  well 
flexed,  and  the  leg  resting 
on  its  outer  surface.  Be- 
fore reaching  the  deep 
fascia,  the  long  saphenous 
vein  or  the  external  super- 
ficial femoral  vein,  may  be 
met  with  and  should  be  avoided.  After  opening  the  deep  fascia  the  fibres  of  the 
inner  edge  of  the  sartorius  should  be  exposed,  and  may  be  recognized  by  their  oblique 
course.  That  muscle  should  be  displaced  outward,  the  vascular  groove  containing 
the  vessel  and  some  fatty  areolar  tissue  identified,  and  the  sheath  exposed.  The 
internal  cutaneous  branch  of  the  anterior  crural  nerve  in  front,  and  the  nerve  to  the 
vastus  internus  and  the  long  saphenous  nerve  externally,  should  be  avoided,  and  the 
sheath  opened.  The  needle  should  be  passed  from  without  inward  to  avoid  the  vein, 
which  here  lies  behind  and  to  the  outer  side  of  the  artery. 

3.  To  reach  the  vessel  in  Hunter's  canal,  the  limb  being  in  the  position  above 
described,  an  incision  is  made  on  the  line  of  the  vessel  extending  from  the  apex  of  the 
triangle  to  about  three  inches  above  the  internal  condyle.  The  long  saphenous  vein 
should  be  avoided.  The  deep  fascia  is  opened,  and, the  outer  edge  of  the  sartorius 
identified.      The  only  structure  that  could  be  mistaken  for  it  is  the  vastus  internus, 


Superficial  dissectii 


S26 


HUMAN    ANATOMY. 


-Adductor  longus  I 

-Internal  saphenou: 
-Femoral  artery 

-Roof  of  Hunters 


Internal  saplie 


the  fibres  of  which  run  obliquely  outward  instead  of  inward.  The  sartorius  is 
displaced  inward  and  the  thigh  more  strongly  abducted,  when  the  tension  on  the 
adductor  fibres — the  adductor  magnus  and  the  lower  edge  of  the  adductor  longus — 
will  clearly  define  the  lower — inner — border  of  Hunter's  canal.      The  aponeurotic  roof 

of  the  canal  stretch- 
IG'  73t  ing    across    to    the 

vastus  internus  is 
pierced  by  the  in- 
ternal saphenous 
nerve,  which  may  be 
a  useful  guide.  This 
aponeurosis  is  di- 
vided and  the  vessel 
exposed.  The  vein 
lies  behind  and 
somewhat  to  the 
outer  side.  The 
needle  should  be 
passed  from  without 
inward. 

The  collateral 
circulation  after  liga- 
tion of  the  superficial 
femoral  is  carried  on 
from  above  by  (a) 
the  perforating  and 
terminal  branches  of 
the  profunda  ;  and 
(6)  the  descending 
branch  of  the  exter- 
nal circumflex  anas- 
tomosing respectively  with  (a)  the  superior  articular  and  muscular  branches  of  the 
popliteal  ;  and  (d)  the  anastomotica  magna  and  superior  articular  from  below. 

i.  The  Superficial  Epigastric  Artery. — The  superficial  epigastric  artery 
(a.  epigastrica  superficialis)  (Fig.  729)  arises  from  the  anterior  surface  of  the  femoral, 
about  1  cm.  below  Poupart's  ligament.  It  is  directed  at  first  forward,  but,  after  per- 
forating the  fascia  lata  or  sometimes  the  cribriform  fascia,  it  bends  upward  over 
Poupart's  ligament  and  ascends  between  the  superficial  and  deep  layers  of  the  super- 
ficial abdominal  fascia  to  the  neighborhood  of  the  umbilicus.  It  gives  branches  to 
adjacent  inguinal  lymphatic  nodes  and  to  the  integument,  anastomosing  with  the 
cutaneous  branches  of  the  deep  epigastric  artery. 

2.  The  Superficial  Circumflex  Iliac  Artery. — The  superficial  circumflex 
iliac  artery  (a.  circumtlexa  ilium  superficialis)  (Fig.  729)  arises  from  the  anterior  surface 
of  the  femoral,  a  little  below  the  superficial  epigastric,  or  from  a  common  trunk  with 
that  artery.  It  perforates  the  fascia  lata  or  the  cribriform  fascia  and  is  then  directed 
laterally  more  or  less  parallel  with  Poupart's  ligament,  extending  almost  as  far  as  the 
anterior  superior  spine  of  the  ilium.  It  gives  branches  to  the  adjacent  inguinal  lym- 
phatic nodes  and  to  the  sartorius  muscle,  and  anastomoses  with  the  cutaneous 
branches  of  the  deep  circumflex  iliac. 

3.  The  Superficial  External  Pudic  Artery. — The  superficial  external  pudic 
artery  (a.  pudenda  externa  superficialis)  (Fig.  729)  arises  from  the  inner  surface  of  the 
femoral  artery  and  is  directed  inward  and  slightly  upward  towards  the  spine  of  the 
pubis.  It  pierces  the  cribriform  fascia  and,  crossing  over  the  spermatic  cord  or  round 
ligament,  sends  branches  to  the  integument  above  the  pubes.  It  is  then  continued 
along  the  dorsal  surface  of  the  penis  or  clitoris,  lateral  and  external  to  the  dorsal  artery 
of  that  organ,  with  which  it  anastomoses  at  the  glans.  It  supplies  branches  to  the 
integument  of  the  penis  and  to  the  preputium  clitoridis,  and  also  gives  branches 
to  the  scrotum  or  labium  majus. 


showing:  fen 
nd  disappea 


THE    FEMORAL    ARTERY 


827 


Fig.  732. 


Stump  of  sartorius 
Superficial  circumflex  iliac  artery 

Rectus  tendon 
Femoral  artery 

Ascending  branch  of  external 
circumflex  artery 

Deep  femoral  artery 

Transverse  branches  of  external 
circumflex  artery 
Descending  branch  of  external 
circumflex  artery 

Vastus  extern  us 


Tendon  of  quadriceps 
extensor,  cut 


Superficial  epigastric  artery 

Superficial  ext.  pudic  artery 

Deep  external  pudic  artery 

Femoral  vein 

Pectineus 

Penis— sectional  surface 


Adductor  longus 

Semitendiuosus 

Gracilis 
Adductor  magnus 


Anastomotica  magna 

nastomotica  magna- 
deep  portion 

■Anastomotica  magna- 
superficial  branch 

■Popliteal  artery 

membranosus 


Inferior  internal  articular  artery 


Arteries  of  front  of  thit 


deeper  dissection. 


828  HUMAN    ANATOMY. 

4.  The  Deep  External  Pudic  Artery. — The  deep  external  pudic  artery  (a. 
pudenda  externa  profunda)  (Fig.  732)  arises  from  the  inner  surface  of  the  femoral, 
either  a  little  below  the  superficial  external  pudic  or  in  common  with  that  vessel.  It 
passes  medially  beneath  the  fascia  lata  across  the  femoral  vein  and  the  pectineus  and 
adductor  longus  muscles.  It  then  pierces  the  fascia  lata  close  to  the  ramus  of  the 
pubis  and  is  distributed  to  the  sides  of  the  scrotum  or  labium  majus,  anastomosing- 
with  branches  of  the  superficial  external  pudic  and  of  the  superficial  perineal  branch 
of  the  internal  pudic. 

5.  The  Deep  Femoral  Artery. — The  deep  femoral  artery  (a.  profunda 
femoris)  (Fig.  733)  arises  from  the  outer  surface  of  the  femoral,  usually  about 
4  cm.  below  Poupart's  ligament,  and  at  first  is  directed  downward  parallel  to  the 
femoral  and  to  the  outer  side  of  that  vessel.  It  then  bends  medially  and  passes 
obliquely  behind  the  femoral  artery  and  vein,  and  on  arriving  at  the  upper  border  of  the 
adductor  longus,  passes  behind  that  vessel  and  is  continued  downward  between  it 
and  the  adductor  magnus,  rapidly  diminishing  in  size.  Finally  it  perforates  the 
adductor  magnus  and  terminates  in  branches  to  the  lower  portions  of  the  hamstring- 
muscles. 

Relations. — At  first  the  profunda  lies  alongside  the  femoral  and  is,  like  it,  su- 
perficial, having  in  front  of  it  only  the  fasciae  and  integument,  together  with  some 
branches  of  the  anterior  crural  nerve.  Later  it  lies  behind  the  femoral  artery  and 
the  femoral  and  profunda  veins,  and  still  later  the  adductor  longus  and  the  adductor 
magnus.  Posteriorly  it  rests  at  first  upon  the  ilio-psoas  and  then  successively  upon 
the  pectineus,  the  adductor  brevis,  and  the  adductor  magnus. 

Branches. — The  profunda  femoris  gives  origin  to  the  following  branches  :  ( 1 )  the  external 
circumflex,  (2)  the  internal  circumflex ;  (3)  the  three  perforating  arteries.  The  terminal  por- 
tion of  the  profunda,  after  it  has  pierced  the  adductor  magnus,  is  sometimes  spoken  of  as  the 
fourth  perforating  artery. 

(a)  The  external  circumflex  artery  (a.  circumflexa  femoris  lateralis)  is  the  largest  of  the 
branches  of  the  profunda  and  arises  from  it  a  short  distance  beyond  its  origin.  It  is  directed 
horizontally  outward  across  Scarpa's  triangle,  resting  upon  the  ilio-psoas  muscle  and  passing 
between  the  superficial  and  deep  branches  of  the  anterior  crural  nerve.  It  then  passes  beneath 
the  sartorius  and  rectus  muscles  and  terminates  by  dividing  into  an  ascending,  a  transverse,  and 
a  descending  branch.  The  ascending  branch  passes  upward  and  outward  to  beneath  the  tensor 
vaginae  femoris,  running  along  the  anterior  trochanteric  line  of  the  femur,  and  terminates  by  anas- 
tomosing with  the  gluteal  and  the  deep  circumflex  iliac  arteries.  It  sends  twigs  to  the  neigh- 
boring muscles  and  to  the  hip-joint.  The  transverse  branch  is  small  and  runs  directly  outward 
to  below  the  greater  trochanter,  passing  between  the  rectus  and  the  crureus  muscles  and  through 
the  substance  of  the  vastus  lateralis.  It  unites  with  branches  of  the  sciatic,  internal  circumflex, 
and  first  perforating  arteries  to  form  the  crucial  anastomosis.  The  descending  branch  runs 
downward  beneath  the  rectus  muscle,  along  with  the  nerve,  to  the  vastus  lateralis,  and  usually 
extends  to  the  neighborhood  of  the  knee-joint,  where  it  anastomoses  with  the  superior  external 
branch  of  the  popliteus  and  assists  in  the  formation  of  the  circumpatellar  anastomosis.  It  gives 
branches  to  the  rectus,  crureus,  and  vastus  lateralis. 

(6)  The  internal  circumflex  artery  (a.  circumflexa  femoris  medialis)  arises  from  the  inner 
surface  of  the  profunda,  very  nearly  opposite  the  external  circumflex.  It  passes  over  the  surface 
of  the  ilio-psoas  and  beneath  the  pectineus  to  reach  the  anterior  surface  of  the  neck  of  the 
femur.  It  then  crosses  the  upper  portion  of  the  adductor  brevis  and  adductor  magnus  and 
passes  along  the  lower  border  of  the  obturator  externus  and,  finally,  upon  the  anterior  surface 
of  the  quadratus  femoris,  where  it  divides  into  its  terminal  branches. 

(aa)  The  ascending  branch  (ramus  ascendens)  passes  upward  towards  the  digital  fossa  of 
the  femur,  sending  branches  to  the  capsule  of  the  hip-joint  and  anastomosing  with  the  sciatic 
and  external  circumflex  arteries. 

(bb)  The  descending  branch  (ramus  descendens)  passes  downward  and  curves  around  the 
lower  border  of  the  quadratus  femoris  to  terminate  in  the  upper  portion  of  the  hamstring  mus- 
cles. This  branch  anastomoses  with  the  sciatic,  external  circumflex,  and  first  perforating  ves- 
sels to  form  the  crucial  anastomosis.  In  addition,  the  internal  circumflex  in  its  course  sends 
muscular  branches  to  the  adjacent  muscles  and  also  an  articular  branch  (ramus  acetabuli)  to  the 
hip-joint. 

(c)  The  three  perforating  branches  arise  in  succession  from  the  profunda  and  pass  back- 
ward, curving  around  the  inner  surface  of  the  femur.  They  perforate  the  adductor  muscles 
close  to  the  bone,  and  supply  the  hamstring  muscles  and  the  vastus  externus,  anastomosing  with 
one  another  and  with  neighboring  vessels. 


THE    FEMORAL    ARTERY. 


829 


(aa)  The  first  or  superior  perforating  artery  (a.  perforans  prima)  is  generally  the  largest  of 
the  three,  and  arises  just  as  the  profunda  passes  behind  the  adductor  longus.  It  either  passes 
through  the  adductor  brevis  or  between  that  muscle  and  the  pectineus  and  pierces  the  adductor 

Fig.  733. 


Superficial  < 


11  flex  iliac 
us  muscle 


Femoral  artery 
Tendon  of  rectus 


Tensor  vaginae  femoris 
Ascending  branch  of 

external  circumflex 


Profunda  femoris 
External  circumflex 


Vastus  extern 

First  perforating  artery 

Adductor  brevis 
Second  perforating  artery 

Vastus  internus 
Third  perforating  artery 


Adductor  longus 


Fourth  perforating  artery 


Deep  branch  of 

anastomotica  magna 


Adductor  magnu 
Gracilis 


Superficial  epigastric  artery 


Psoas  mu 

scle 

Sperm  a 

ic  cord 

Obturator  artery 
Adductor  longus 
Adductor  brevis 
Corpus  spongiosum  of  penis 

Obturator  externus 
Internal  circumflex  artery 


^>  Adductor  magnus 


Semimembranosus 


Superficial  branch  of 

anastomotica  magna 


Deep  femoral  artery  and  its  branches. 

magnus,  and  then  divides  into  an  ascending  and  a  descending  branch,  the  latter  of  which  anasto- 
moses with  the  ascending  branch  of  the  second  perforating,  while  the  former  assists  in  the  for- 
mation of  the  crucial  anastomosis. 


83o 


HUMAN    ANATOMY. 


(bb)  The  second  or  middle  perforating  artery  (a.  perforans  secunda)  arises  a  little  below  the 
first  and,  after  piercing  the  adductor  brevis  and  the  adductor  magnus,  divides  into  an  ascending 
and  a  descending  branch  which  anastomose  respectively  with  the  descending  branch  of  the  first 
and  the  ascending  branch  of  the  third  perforating.  A  nutrient  artery  to  the  femur  is  usually- 
given  off  from  this  vessel,  although  frequently  it  comes  from  the  third  perforating. 

(cc)  The  third  or  inferior  perforating  artery  (a.  perforans  tertia)  arises  usually  on  a  level 
with  the  lower  border  of  the  adductor  brevis.  It  pierces  the  adductor  magnus  and  terminates, 
like  the  other  perforating  arteries,  by  dividing  into  an  ascending  and  a  descending  branch.  The 
ascending  branch  anastomoses  with  the  descending  branch  of  the  second  perforating,  while  the 
descending  one  anastomoses  with  branches  from  the  terminal  portion  of  the  profunda.  The 
nutrient  artery  to  the  femur  is  frequently  given  off  by  this  branch. 

Variations. — The  variations  of  the  profunda  and  its  branches  are  somewhat  numerous,  and 
to  a  very  considerable  extent  are  largely  associated  with  one  another.  In  other  words,  there 
may  be  more  or  less  dissociation  of  the  various  vessels  of  the  profunda  complex,  one  or  other 
of  them  having  an  independent  origin  from  the  femoral,  and,  indeed,  this  process  may  occur  to 
such  an  extent  that  a  profunda  femoris  as  a  definite  vessel  can  hardly  be  said  to  exist. 

The  point  of  origin  of  the  profunda  from  the  femoral  is  stated  to  be  usually  about  4  cm. 
distant  from  Poupart's  ligament,  but  the  figure  must  be  taken  as  a  general  average  from  which 
there  may  be  wide  departures.  Thus,  in  430  limbs  Quain  found  that  the  distance  from  Poupart's 
ligament  of  the  origin  of  the  profunda  was  between  2.5  and  5.1  cm.  in  68  per  cent.,  and  of 
this  number  it  was  between  2.5  and  3.8  cm.  in  42.6  per  cent.  It  was  distant  less  than  2.5  cm.  in 
24.6  per  cent,  of  the  limbs  and  more  than  5.1  cm.  in  only  7.4  per  cent.  Quain's  figures  are  as 
follows  : 

Origin  at  Poupart's  ligament 7  cases. 

0-1.3  cm-  below  Poupart's  ligament 13  cases. 

1.3-2.5  cm.  below  Poupart's  ligament S6  cases. 

2.5-3.8  cm.  below  Poupart's  ligament 183  cases. 

3.8-5.1  cm.  below  Poupart's  ligament 109  cases. 

5.1-6.3  cm.  below  Poupart's  ligament 19  cases. 

6.3-7.6  cm.  below  Poupart's  ligament 12  cases. 

1 1.6  cm.  below  Poupart's  ligament 1  case. 

Essentially  similar  results  have  been  obtained  by  Srb  and  other  observers,  and  it  seems 
evident  from  the  statistics  that  the  origin  of  the  profunda  is  more  apt  to  be  above  than  below  the 
point  taken  as  the  average. 

One  or  other  of  the  circumflex  arteries  may  arise  independently  from  the  femoral,  this  con- 
dition occurring  somewhat  more  frequently  in  the  case  of  the  internal  circumflex  than  in  that  of 

the  outer  one,  and  the  point  of  origin  of  the  inde- 
Fig.  734.  pendent  vessel  may  be  either  above  or  below  that 

of  the  profunda.  When  it  is  the  internal  circum- 
flex which  is  the  independent  vessel,  its  origin  is 
most  frequently  above  that  of  the  profunda;  or  per- 
haps it  would  be  more  correct  to  say  that  with  an 
independent  internal  circumflex  the  origin  of  the 
profunda  is  apt  to  be  somewhat  below  the  typical 
point.  With  a  high  origin  of  the  profunda,  the 
external  circumflex  may  be  represented  by  two 
vessels,  one  of  which  arises  from  the  profunda, 
while  the  accessory  one  springs  from  the  femoral 
lower  down.  Occasionally  both  circumflexes  may 
arise  independently  from  the  femoral,  the  profunda 
in  such  cases  having  usually  a  low  origin,  and  one 
or  other  of  the  perforating  arteries  may  arise  from 
the  circumflexes.  An  extreme  case  of  this  nature, 
representing  an  almost  complete  dissociation  of  the 
profunda,  has  been  described  by  Ruge,  (Fig.  734) 
in  which  the  superior  perforating  arises  from  the 
internal  circumflex  and  the  middle  one  from  the 
external  circumflex,  what  may  be  termed  the  pro- 
funda arising  9.7  cm.  below  Poupart's  ligament 
and  giving  off  only  the  inferior  perforating. 

The  internal  circumflex  may  be  very  much 
reduced  in  size  or  even  absent,  its  territory  being 
supplied  by  branches  from  the  obturator  artery.  Occasionally,  although  rarely,  one  or  other 
of  the  perforating  branches  arises  directly  from  the  femoral,  and  a  similar  origin  has  also  been 
observed  for  the  descending  branch  of  the  external  circumflex. 

6.  The  Muscular  Branches. — The  muscular  branches  (rami  musculares)  of 
the  femoral  artery  are  rather  numerous  and  are  distributed  to  all  the  muscles  upon  the 
front  of  the  thigh.  They  are  variable  in  number  and  position  and  do  not  call  for  any 
special  description. 


Superficial 


Middle 

perforating- 


Inferior  perforating 
(profunda  femoris) 


Superficial 
epigastric 


\ '■  -S7—  Internal 

f  drcumflex 

\\ —  Superior 

perforating 


Diagram  showing  almost  complete  dissociation 
of  profunda  femoris.     {Ruge). 


THE   POPLITEAL   ARTERY.  831 

7.  The  Anastomotica  Magna. — The  anastomotica  magna  (a.  genu  supremaj 
(Fig.  733)  arises  from  the  femoral,  just  before  it  passes  through  the  adductor  magnus. 
It  passes  downward  a  short  distance  in  front  of  the  adductor  magnus  and  divides  into 
two  branches,  a  superficial  and  a  deep. 

Branches. — (a)  The  superficial  branch  (ramus  saphenus)  follows  the  course  of  the  long 
saphenous  nerve  and,  perforating  with  it  the  crural  fascia,  is  supplied  to  the  integument  over  the 
inner  side  of  the  knee  and  the  upper  portion  of  the  leg.  It  anastomoses  with  the  inferior  in- 
ternal articular  branch  of  the  popliteal,  then  entering  into  the  formation  of  the  circumpatellar 
anastomosis. 

(6)  The  deep  branch  (ramus  musculo-articularis)  enters  the  substance  of  the  vastus  interims 
and  passes  downward  to  take  part  in  the  formation  of  the  circumpatellar  plexus,  also  sending 
branches  to  the  capsule  of  the  knee-joint. 

Variations.— The  anastomotica  magna  is  occasionally  given  off  from  the  upper  portion  of  the 
popliteal  artery.  Occasionally  it  is  continued  some  distance  down  the  leg  with  the  long  saphe- 
nous nerve,  representing  in  such  cases  more  perfectly  the  original  saphenous  artery  (page  849)  ; 
or  this  vessel  may  be  indicated  by  a  series  of  anastomoses  which  accompany  the  nerve  and  vein 
and  begin  with  the  superficial  branch  of  the  anastomotica. 

Anastomoses  of  the  Femoral  Artery. — In  the  case  of  obliteration  of  the 
external  iliac  artery,  blood  may  reach  the  femoral  by  means  of  the  anastomoses  of  the 
iliac  arteries  already  noted  (page  821),  and,  in  addition,  byway  of  the  anastomoses 
between  the  superficial  and  deep  epigastrics  and  between  the  superficial  circumflex 
iliac  artery  and  the  deep  vessel  of  the  same  name  and  the  gluteal.  The  anastomoses 
between  the  external  and  internal  pudics  would  also  assist. 

If  the  obliteration  of  the  femoral  artery  be  above  the  origin  of  the  profunda 
femoris,  a  collateral  circulation  may  be  established  by  the  union  of  the  branches  of  that 
vessel  with  the  sciatic  in  the  crucial  anastomosis  and  also  by  the  communication  exist- 
ing between  the  external  circumflex  and  the  gluteal  and  the  deep  circumflex  iliac. 

If  the  obliteration  be  below  the  origin  of  the  profunda,  circulation  will  be  main- 
tained through  the  anastomoses  around  the  knee-joint,  in  which  the  descending 
branch  of  the  external  circumflex  and  the  terminal  portion  of  the  profunda,  on  the 
one  hand,  and  the  anastomotica  magna,  on  the  other,  participate. 

THE    POPLITEAL   ARTERY. 

The  popliteal  artery  (a.  poplitea)  (Fig,  736)  is  the  continuation  of  the  femoral, 
and  extends  from  the  point  where  the  latter  pierces  the  adductor  magnus  to  the  lower 
border  of  the  popliteus  muscle,  where  it  divides  into  the  anterior  and  posterior  tibial 
arteries.  Its  course  is  at  first  downward  and  slightly  outward,  but  it  soon  becomes 
almost  vertical,  corresponding  practically  with  the  long  axis  of  the  popliteal  space. 

Relations. — Anteriorly,  the  popliteal  artery  is  in  relation  to  the  posterior  sur- 
face of  the  lower  part  of  the  femur,  from  which  it  is  separated,  however,  by  a  layer 
of  adipose  tissue.  Lower  down  it  rests  upon  the  posterior  ligament  of  the  knee-joint, 
and  still  lower  upon  the  fascia  covering  the  posterior  surface  of  the  popliteus  muscle. 
Posteriorly ,  it  is  somewhat  overlapped  in  the  upper  part  of  its  course  by  the  border  of 
the  semimembranosus,  and  below  by  the  inner  head  of  the  gastrocnemius.  In  its  pas- 
sage through  the  popliteal  space,  however,  it  is  covered  only  by  the  integument  and 
fasciae,  beneath  which  is  a  considerable  amount  of  fatty  tissue.  About  the  middle  of  its 
course  it  is  crossed  obliquely  from  without  inward  by  the  internal  popliteal  nerve,  and 
throughout  its  entire  length  it  has  resting  upon  and  firmly  adherent  to  it  the  popliteal 
vein,  which  lies,  however,  slightly  to  its  outer  side  above  and  to  its  inner  side  below. 
Internally,  it  is  in  relation  from  above  downward  with  the  semimembranosus,  the 
internal  condyle  of  the  femur,  the  internal  popliteal  nerve,  and  the  inner  head  of  the 
gastrocnemius,  and  externally  with  the  internal  popliteal  nerve,  the  external  condyle 
of  the  femur,  the  outer  head  of  the  gastrocnemius,  and  the  plantaris. 

Branches. — The  branches  which  arise  from  the  popliteal  artery  are  all  small 
and  may  be  arranged  in  three  groups:   (1)  muscular,  (2)  articular,  (3)  cutaneous. 

Variations. — The  popliteal  artery  occasionally  divides  into  the  tibial  arteries  above  the 
upper  border  of  the  popliteus  muscle,  and  more  rarely  the  division  is  delayed  until  the  artery 
has  reached  a  point  almost  half-way  down  the  leg. 


832 


HUMAN    ANATOMY. 


Practical  Considerations. — The  popliteal  artery  is  rarely  wounded  because 
of  its  protected  position  on  the  posterior  aspect  of  the  limb  and  in  the  hollow  of  the 
ham.  Its  upper  portion  is  overlapped  by  the  outer  border  of  the  semimembranosus 
muscle,  and  its  lower  portion  by  the  inner  head  of  the  gastrocnemius  ;  the  inter- 
mediate portion,  covered  only  by  skin,  fascia,  and  areolo-fatty  tissue,  is  very  deeply 
placed  and  is  not  more  than  an  inch  in  length.  It  may  be  torn  in  luxation  of  the 
knee,  or  wounded  in  fracture  of  the  lower  end  of  the  femur,  or  during  certain  opera- 
tions, as  osteotomy  of  the  femur  for  genu  valgum.  Laceration  or  wound  of  this 
vessel  is  more  dangerous  than  a  corresponding  injury  to  the  brachial  at  the  bend  of 
the  elbow,  because  of  the  greater  proximity — in  the  case  of  the  popliteal — of  the 
branches  on  which  the  chief  anastomotic  supply  depends  ;  and  because  of  the 
unyielding  character  of  the  walls  of  the  space  in  which  the  effused  blood  is  confined. 
Aneurism  of  the  popliteal  artery  comes  next  in  frequency  to  aneurism  of  the 
thoracic  aorta.  This  is  due  (a)  to  the  frequent  minor  strains  occurring  during 
flexion  and  extension  of  the  knee.  If  extreme,  the  former  movement  bends  the 
artery  at  such  an  acute  angle   that  the  flow  of   blood  through   it  is  arrested  and 

the    pressure    above    this 
Fig.  735.  point    greatly    increased  ; 

and  the  latter  may  so 
stretch  the  vessel  longi- 
tudinally that  if  its  elasticity 
is  at  all  diminished  by  ather- 
omatous changes  the  inner 
and  middle  coats  are 
thinned  or  ruptured.  (Jb~) 
The  lack  of  muscular  sup- 
port which  the  artery — sur- 
rounded by  loose  cellular 
tissue — receives  also  favors 
the  development  of  aneur- 
ism, (t)  The  artery  is  said 
to  be  unusually  liable  to  ath- 
eromatous degeneration. 
{d )  It  divides  a  short  dis- 
tance below  into  two 
vessels,  thus  increasing  the 
blood-pressure  above  the 
bifurcation.  (<?)  Its  course 
is  curved  (like  that  of 
the  aortic  arch),  and  hence 
the  pressure  is  irregularly 
distributed.  (_/)  The  ten- 
dinous opening  in  the 
adductor  magnus,  through 
which  the  vessel  runs,  con- 
stricts it  slightly  at  each  pulse-beat  and  tends — as  in  the  case  of  the  abdominal  aorta 
below  the  hiatus  aorticus— to  produce  a  little  dilatation  below  that  level.  As  both 
these  vessels  have  been  said  to  be  especially  weak  in  these  regions,  it  may  be 
possible  that  some  trifling  but  oft-repeated  interference  with  the  vasa  vasorum 
favors  degenerative  changes  by  slightly  diminishing  the  blood-supply  to  the  vessel 
walls. 

Aneurism  may  occur  suddenly,  with  a  sensation  resembling  that  produced  by  a 
blow  with  a  whip.  It  may  develop  slowly,  and,  if  it  takes  a  forward  direction,  with 
symptoms  simulating  rheumatism  on  account  of  the  pressure  upon  the  posterior 
ligament  of  the  knee-joint— i.e.,  dull  pain,  stiffness,  semi-flexion  of  the  knee,  inability 
to  extend  the  joint  freely.  If  it  develops  in  the  opposite  direction,  the  absence  of 
resistance  causes  the  early  appearance  of  a  characteristic  pulsating  tumor  with  bruit 
and  the  usual  signs  of  aneurism.  It  should  not  be  confused  with  an  enlarged  bursa 
(page  647),  the  subject  of  transmitted  pulsation,  or  with  tumor  or  abscess  overlying 


THE    POPLITEAL   ARTERY.  833 

the  artery  and  similarly  influenced.  Ultimately  there  is  apt  to  be  cedema  of  the  leg 
from  interference  with  the  venous  circulation,  or  erosion  of  the  posterior  lower  sur- 
face of  the  femur,  or  great  pain  with  weakness  of  the  leg  from  pressure  on  the  inter- 
nal popliteal  nerve,  or  even  moist  gangrene  if  the  aneurism  has  leaked  or  burst  and 
the  venous  current  has  been  cut  off  by  the  pressure  of  the  effused  blood  confined  for 
a  time  within  narrow  limits  and  under  great  pressure  by  the  fascia  of  the  region 
(page  646). 

Compression  of  the  popliteal  may  be  effected  directly  at  its  upper  end  by  pres- 
sure forward,  so  that  it  is  flattened  out  against  the  femur,  only  a  little  fatty  connective 
tissue  intervening.  It  is  almost  impossible,  however,  to  avoid  including  the  thick- 
walled  vein  which  is  nearer  the  surface  and  very  closely  attached  to  the  artery. 
Compression  is  therefore  almost  invariably  applied  to  the  common  femoral  (page 
824).  On  account  of  the  shortness  of  the  popliteal — and  the  consequent  proximity 
of  a  ligature  to  the  diseased  portion,  if  the  vessel  itself  is  tied — the  superficial  femoral 
at  the  point  of  election — the  apex  of  Scarpa's  triangle — is  usually  selected  for  liga- 
tion when  that  becomes  necessary. 

Ligation  of  the  popliteal  artery  is  effected  at  either  :  (1)  its  upper,  or  (2)  its 
lower  third,  the  depth  of  the  middle  portion  and  the  density  of  the  lateral  fascial 
border  of  the  space  in  which  it  lies  rendering  it  unsuitable  for  operation. 

1.  The  patient  being  prone  with  the  leg  extended,  an  incision  is  made  along  the 
external  border  of  the  semimembranosus  muscle,  beginning  at  the  junction  of  the 
middle  and  lower  thirds  of  the  thigh.  The  skin  and  fascia  and  some  fatty  tissue 
having  been  divided,  the  muscle  is  drawn  inward,  and  the  vessel  will  be  found  with 
the  internal  popliteal  nerve  external  to  it  and  much  more  superficial,  and  the  vein 
external  and  behind  it, — i.e. ,  nearer  the  surface  of  the  popliteal  space — and  closely 
adherent.      The  needle  is  passed  from  without  inward. 

2.  An  incision  is  made  beginning  opposite  the  line  of  the  articulation  a  little 
external  to  the  middle  of  the  popliteal  space,  the  inner  head  of  the  gastrocnemius 
being  slightly  larger  than  the  outer  head.  The  external  saphenous  vein  lying  in  the 
superficial  fascia  is  drawn  to  one  side,  the  fascia  is  divided,  and  the  two  heads  of  the 
gastrocnemius  are  exposed  and  separated  with  the  finger,  the  knee  being  a  little 
flexed  so  as  to  relax  them.  At  the  bottom  of  the  interval  between  them  will  be  found 
the  nerve  and  vein  lying  to  the  inner  side  of  the  artery  and  somewhat  superficial  to  it. 
The  needle  is  passed  from  within  outward. 

The  collateral  circulation  is  carried  on  from  above  the  ligature  by  means  of  (a) 
the  superior  articulars  ;  (J>)  the  anastomotica  magna  ;  (c)  the  descending  branch  of 
the  external  circumflex  and  the  terminal  portion  of  the  profunda  anastomosing 
respectively  with  («)  the  inferior  articulars  ;  (6)  the  tibial  recurrent  ;  and  (c)  the 
superior  fibular  and  branches  of  the  popliteal.  The  rete  patellar  takes  part  in  this 
anastomosis. 

1.  The  Muscular  Branches. — These  (Fig.  736)  are  arranged  in  two  groups, 
and  are  supplied  to  the  muscles  which  bound  the  popliteal  space.  The  superior  gj'oup 
consists  of  a  variable  number  of  small  vessels  which  pass  to  the  biceps,  semimembra- 
nosus, and  semitendinosus,  while  the  inferior  group  is  composed  of  some  small 
branches  which  pass  to  the  popliteus  muscle,  and  two  larger  vessels,  the  largest  of  all 
the  vessels  which  arise  from  the  popliteal,  which  pass  respectively  to  the  inner  and 
outer  heads  of  the  gastrocnemius,  and  are  termed  the  sural  arteries  (aa.  surales). 
They  arise  just  as  the  popliteal  is  passing  beneath  the  inner  head  of  the  gastrocnemius. 

2.  The  Articular  Branches. — These  (Fig.  736)  are  five  in  number,  four 
being  arranged  in  pairs,  two  above  and  two  below,  while  the  fifth  is  unpaired  or 
azygos.  The  paired  branches  wind  around  the  femur  and^  the  capsule  of  the  knee- 
joint  towards  the  front,  where  they  anastomose  with  one  another  and  with  adjacent 
vessels  to  form  a  rich  circumpatellar  anastomosis.  They  give  off  branches  to  the 
capsule  of  the  knee-joint  and  also  to  the  neighboring  muscles. 

(a  and  6)  The  internal  and  external  superior  articular  branches  (aa.  genu  superior  medialis 
et  lateralis)  arise  opposite  each  other  and  pass  transversely  above  the  corresponding  heads  of  the 
gastrocnemius.     The  external  one  then  passes  beneath  the  biceps  and  winds  around  the  femur 

53 


834  HUMAN   ANATOMY. 

above  its  external  condyle,  embedded  in  the  substance  of  the  vastus  externus,  dividing  finally 
into  branches  which  take  part  in  the  formation  of  the  circumpatellar  anastomoses.  The  termi- 
nation of  the  internal  branch  is  similar,  and  its  course  is  beneath  the  semimembranosus  and 
through  the  tendon  of  the  adductor  magnus  into  the  substance  of  the  vastus  internus. 

(c)  The  internal  inferior  articular  branch  (a.  genu  inferior  medialis)  arises  about  opposite 
or  a  little  above  the  line  of  the  tibio-femoral  articulation  and  courses  downward  and  inward 
over  the  surface  of  the  popliteal  muscle,  beneath  the  inner  head  of  the  gastrocnemius.  It  passes 
beneath  the  internal  lateral  ligament  of  the  knee-joint  and  winds  around  the  tuberosity  of  the 
tibia  to  join  the  circumpatellar  anastomosis. 

(d  )  The  external  inferior  articular  branch  (a.  genu  inferior  lateralis)  arises  a  little  lower  down 
than  its  fellow  and  passes  almost  transversely  outward,  at  first  beneath  the  external  head  of  the 
gastrocnemius  and  the  plantaris,  and  winds  around  the  outer  tuberosity  of  the  tibia,  beneath 
the  long  internal  lateral  ligament  of  the  knee-joint,  to  join  the  circumpatellar  anastomosis. 

(e)  The  azygos  articular  branch  (a.  genu  media)  is  the  smallest  of  all  the  articular  branches. 
It  arises  either  from  the  anterior  surface  of  the  popliteal  or  from  the  external  superior  articular 
branch,  and  pierces  the  posterior  ligament  of  the  knee-joint  to  be  distributed  to  the  crucial, 
mucous,  and  alar  ligaments. 

The  circumpatellar  anastomosis  (rete  patellae)  (Fig.  732)  is  a  rich  net-work 
of  vessels  which  occurs  in  the  superficial  fascia  surrounding  the  patella,  and  from  which 
branches  are  sent  to  the  patella,  the  capsule  of  the  knee-joint,  and  the  neighboring 
muscles.  The  following  vessels  take  part  in  its  formation.  From  above,  the  anasto- 
motica  magna  from  the  femoral  and  the  descending  branch  of  the  external  circumflex ; 
from  the  sides,  the  internal  and  external  superior  and  the  internal  and  external  inferior 
articular  branches  of  the  popliteal  and  the  muscular  branches  of  the  same  artery ;  and 
from  below,  the  anterior  tibial  recurrent. 

3.  The  Cutaneous  Branches. — These  are  variable  in  origin  and  number  and 
are  distributed  to  the  integument  covering  the  popliteal  space  and  the  upper  part  of 
the  calf  of  the  leg.  One  of  them  occasionally  attains  a  considerable  size  and  is 
termed  the  posterior  saphenous  artery.  It  accompanies  the  short  saphenous  vein 
down  the  back  of  the  crus,  sending  off  branches  to  the  adjacent  integument. 

The  Collateral  Circulation  of  the  Popliteal  Artery. — The  passage  of 
blood  to  the  leg  after  ligation  of  the  popliteal  artery  is  effected  by  means  of  the  rich 
anastomosis  which  exists  around  the  knee-joint,  and  in  which  the  branches  of  the 
popliteal  take  part.  In  addition  to  these,  however,  it  also  receives  from  above  the 
anastomotica  magna,  the  descending  branch  of  the  external  circumflex,  and  the 
terminal  portion  of  the  profunda  artery,  while  there  pass  to  it  from  below  the  superior 
fibular  and  the  anterior  and  posterior  tibial  recurrent  arteries. 

THE    POSTERIOR    TIBIAL    ARTERY. 

The  posterior  tibial  artery  (a.  tibialis  posterior)  (Fig.  736)  is  the  direct  con- 
tinuation of  the  popliteal  down  the  posterior  surface  of  the  leg.  It  begins  at  the 
bifurcation  of  the  popliteal  at  the  lower  border  of  the  popliteus  muscle  and  passes 
almost  vertically  downward,  under  cover  of  the  more  superficial  muscles  of  the  calf, 
to  the  groove  between  the  inner  malleolus  and  the  os  calcis,  where,  opposite  the  tip 
of  the  malleolus,  it  terminates  by  dividing  into  the  internal  and  external  plantar 
arteries.  Its  course  may  be  indicated  by  a  line  drawn  from  the  centre  of  the  popli- 
teal space  to  a  point  midway  between  the  inner  malleolus  and  the  os  calcis. 

Relations. — Anteriorly,  the  artery  rests  in  succession,  from  above  downward, 
upon  the  tibialis  posticus,  the.  flexor  longus  digitorum,  the  posterior  surface  of  the 
lower  part  of  the  tibia,  and  the  internal  lateral  ligament  of  the  ankle-joint.  It  is 
closely  bound  down  to  the  muscles  upon  which  it  rests  by  the  layer  of  the  deep  fascia 
which  covers  them,  the  thickness  and  density  of  this  fascia  increasing  towards  the 
lower  part  of  the  leg.  Posteriorly ,  it  is  covered  by  the  soleus  and  gastrocnemius 
throughout  the  greater  part  of  its  course,  but  in  the  lower  third  of  the  leg  it  is  super- 
ficial, being  covered  only  by  the  skin  and  fascias,  except  just  before  its  termination, 
where  it  lies  beneath  the  internal  annular  ligament  and  the  origin  of  the  abductor 
hallucis.  A  short  distance  below  its  commencement  it  is  crossed  obliquely,  from 
within  outward,  by  the  posterior  tibial  nerve.  Internally,  it  is  in  relation  with  the 
posterior  tibial  nerve  for  a  short  distance  above,  and   in  the  malleolar  groove  it  has 


THE    POSTERIOR   TIBIAL   ARTERY. 

Fig.  736. 


835 


Semimembranosus  ■—•:_--- 


Semitendinosus 
Superior  internal 

articular  artery 

Sartori 
Gracilis 

Sural  branches 
Gastrocnemius — 


Inferior  internal  articul; 

Internal  lateral  ligament 
Posterior  tibial  artery 

Soleus.  cut 


Flexor  longus  digitorum 


External  plantar  artery 
Internal  plantar  artery 


Flexor  longus  hallucis  tend 


Popliteal  artery 

Superior  external  articular  artery 

Azygos  articular  artery 

Sural  branches 

Inferior  external  articular 

Plantaris 

Gastrocnemius— outer  head 

Tendon  of  popliteus 


Anterior  tibial  artery 


Tibialis  post 


Peroneal  artery 

Soleus,  turned  aside 


Flexor  longus  hallucis 


Anterior  peroneal  artery 
Communicating  branch 
Tendon  of  peroneus  longus 


Flexor  longus  hallucis 
Tendo  Achillis 

External  calcanean  (postern 

peroneal)  branches 
Internal  calcanean  branch 


Plantar  fascia  and  flexor  bre> 
digitorum 
Tendon  of  flexor  longus  digitorum 


Arteries  of  posterior  surface  of  right  1 


836  HUMAN    ANATOMY. 

internally  and  in  front  of  it  the  tendon  of  the  flexor  longus  digitorum,  and  internal  to 
that  the  tendon  of  the  tibialis  posticus.  Externally,  the  posterior  tibial  nerve  accom- 
panies it  throughout  the  greater  portion  of  its  course,  and  at  the  ankle-joint  the  nerve 
lies  external  and  posterior  to  the  artery,  between  it  and  the  tendon  of  the  flexor  longus 
pollicis.  The  artery  is  accompanied  throughout  its  course  by  two  vena;  comites 
which  lie  respectively  to  its  outer  and  inner  side. 

Branches. — In  addition  to  numerous  muscular  bj-anches  which  are  distributed 
to  the  neighboring  muscles,  and  cutaneous  branches  to  the  inner  and  posterior  sur- 
faces of  the  leg,  the  posterior  tibial  gives  origin  to  ( I )  a  nutrient  branch  to  the  tibia, 
(2)  the  peroneal  artery,  (3)  a  communicating  branch,  (4)  an  internal  malleolar 
branch,  (5)  an  internal  calcaneal  and  the  two  terminal  branches,  (6)  the  internal, 
and  (7)  the  external  plantar  arteries. 

Variations.— Although  apparently  the  principal  artery  of  the  flexor  surface  of  the  leg  and 
the  direct  continuation  of  the  popliteal,  developmentally  the  posterior  tibial  is  a  secondary 
vessel,  the  original  main  vessel  being  the  peroneal.  The  history  of  the  posterior  tibial  seems  to 
have  been  somewhat  as  follows.  The  saphenous  artery,  whose  origin  has  been  mentioned  in 
connection  with  the  variations  of  the  femoral  artery  (page  823),  in  the  lower  part  of  the  leg 
winds  around  to  the  posterior  surface  and  passes  behind  the  internal  malleolus,  where  it  termi- 
nates by  dividing  into  the  plantar  arteries.  From  the  upper  part  of  the  peroneal  artery  a  branch 
arises  which  passes  down  the  tibial  side  of  the  leg,  beneath  the  superficial  flexor  muscles,  and 
at  the  internal  malleolus  anastomoses  with  the  saphenous.  This  vessel  is  the  posterior  tibial, 
and,  its  calibre  enlarging,  exceeds  that  of  the  peroneal,  which  thus  sinks  to  the  rank  of  a  branch  . 
of  the  artery  to  which  it  gave  birth.  A  reason  for  this  increase  of  calibre  in  the  posterior  tibial 
is  to  be  found  in  the  degeneration  of  the  saphenous  artery  (page  S49),  whereby  the  tibial  be- 
comes the  channel  of  supply  for  the  plantar  arteries,  which  seem  to  be  its  continuation. 

The  majority  of  the  principal  variations  of  the  posterior  tibial  are  readily  explained  in  the 
light  of  such  a  history.  Thus  there  may  be  no  posterior  tibial,  or  it  may  be  represented  by  a 
small  vessel  whose  distribution  is  confined  to  the  upper  part  of  the  leg.  In  such  a  case,  as 
the  saphenous  artery  degenerates,  anastomoses  between  it  and  the  terminal  portion  of  the  pero- 
neal may  enlarge  so  that  the  plantar  arteries  come  to  take  their  origin  from  that  vessel.  Or, 
again,  the  development  of  the  posterior  tibial  may  proceed  normally,  but  the  lower  portion  of 
the  saphenous  may  not  degenerate  completely,  but  persists,  as  has  been  observed,  as  a  branch 
of  the  tibial,  passing  upward  upon  the  leg  in  company  with  the  long  saphenous  nerve. 

Other  variations  of  the  posterior  tibial  which  have  been  observed,  however,  cannot  appar- 
ently be  explained  as  resulting  from  modifications  of  the  normal  course  of  development,  but  are 
rather  to  be  regarded  as  progressive  variations  due  to  the  enlargement  of  what  are  usually  more 
or  less  insignificant  anastomoses.  Of  this  nature  is  the  origin  from  the  posterior  tibial,  at  about 
the  middle  of  the  leg,  of  a  branch  which  pierces  the  interosseous  membrane  and  divides  into 
an  ascending  and  a  descending  branch,  which  together  represent  the  anterior  tibial  artery.  Or, 
again,  the  posterior  tibial  has  been  observed  to  perforate  the  lower  part  of  the  interosseous 
membrane  and  to  be  continued  down  the  dorsum  of  the  foot  as  the  dorsalis  pedis  artery, 
the  plantar  arteries  arising  from  the  peroneal.  Occasionally,  also,  the  posterior  tibial  may 
terminate  by  inosculating  with  the  peroneal,  probably  by  the  enlargement  of  the  communicating 
branch,  the  peroneal  in  this  case  also  giving  rise  to  the  plantar  arteries. 

The  high  and  low  origins  of  the  posterior  tibial  have  already  been  mentioned  in  connection 
with  the  variations  of  the  popliteal  (page  831). 

Practical  Considerations. — The  posterior  tibial  artery  on  account  of  its  deep 
position  beneath  the  large  superficial  calf  muscles  is  rarely  wounded  and,  by  reason 
of  the  support  which  it  receives  in  its  upper  two-thirds  from  those  muscles  and  the 
deeper  muscular  layer  on  which  it  lies,  and  in  its  lower  third  from  the  dense  fascia 
covering  it,  it  is  seldom  the  subject  of  aneurism.  Except  for  a  short  portion  of  its 
course  immediately  above  the  ankle,  it  is  separated  from  the  tibia  by  the  deep  calf 
muscles,  and  is  therefore  not  often  involved  in  fractures  of  that  bone. 

The  bifurcation  of  the  popliteal  is  not  infrequently  the  region  at  which  an  em- 
bolus carried  down  from  the  popliteal  is  arrested,  and  such  a  clot  may  block  both 
the  tibial  arteries.  Their  free  anastomosis  prevents  gangrene  if  only  one  of  them  is 
occluded  ;  but  if  both  are  involved,  and  especially  if  the  succeeding  additions  to  the 
clot  invade  the  anterior  tibial  recurrent — interfering  with  anastomosis  from  above — 
gangrene  almost  certainly  follows. 

Compression  of  the  posterior  tibial  is  scarcely  possible  above  its  lower  third. 
Above  the  ankle  and  behind  the  inner  malleolus  it  may  be  flattened  against  the  tibia 
by  pressure  directed  outward  and  a  little  forward. 

Ligation  of  the  posterior  tibial  may  be  done  at  any  part  of  its  course,  but  in  its 
upper  third  is  an  operation  of  some  difficulty. 


THE    POSTERIOR    TIBIAL   ARTERY. 


S37 


Vena?  comites 

Flexor  longus 
digitorum 
Post,  tibial  artery 
Post,  tibial  nerve 


Tendon  of 

plantaris 


i.    The  artery  is  best  approached  from  the  inner  side  of  the  leg.      The  leg  being 

flexed,  the  limb  is  laid  on  its  outer  side,  and  an  incision  three  and  a  half  or  four  inches 

in   length   is   made  along  the  inner 

margin  of  the  tibia,   beginning  two  ' 

and  a  half  inches  from  the  upper  end  of 

that  bone.      The  skin  being  divided, 

care  must  be  exercised   in   opening 

the  superficial  fascia  not  to  injure  the 

internal  saphenous  vein  or  nerve,  both 

of  which  lie  directly  in  the  track  of  the 

wound.      These  structures  being  dis- 
placed, the  deep  fascia  must  be  slit  up 

to  the  full  extent  of  the  incision.      It 

should  also  be  cut  transversely,  so  as 

to  allow  a  freer  access  to  the  intermus- 
cular parts.      The  next  step  consists 

in  detaching  the  origin  of  the  soleus 

muscle  from  the  tibia.      It  is  at  this 

stage  of  the  operation  that  one  of  two 

errors  is  often  committed, — the  inter- 
muscular  space    between    the    inner 

head  of  the  gastrocnemius  and  the 

soleus  muscle  is  opened,  or  all  the 

muscular  tissue  is  separated  from  the 

bone,  the  tibialis  posticus  muscle  be- 
ing  raised    along   with    the    soleus. 

The  first  mistake  leads  the  operator 

above  the  vessel  and  the  second  leads 

him  underneath.     There  is,  however, 

a  guide  which  will  afford  important 

assistance.      If    the  soleus   has   been 

properly  detached    and    raised,    its 

under  surface  will  present   a  white,    shining  sheet   of   tendinous    material,   beneath 
F  „  which   will  be   seen    a 

layer  of  fascia  (inter- 
muscular) covering  the 
tibialis  posticus  muscle. 
If  search  is  now  made 
externally  and  towards 
the  middle  of  the  leg, 
the  artery  will  be  found 
covered  by  the  inter- 
muscular fascia,  the 
nerve  lying  to  its  outer 
side.  After  the  vessel 
has  been  separated 
from  the  investing  con- 
nective tissue  and  the 
accompanying  veins, 
the  needle  must  be 
passed  from  without 
inward  (Agnew). 

2.  At  the  middle 
third  the  artery  is 
reached  through  an 
incision  parallel  with 
the  inner  edge  of  the 

tibia  and  a  half  inch  from  its  border.      Avoiding  the  saphenous  vein  and  nerve,  the 

superficial  fascia  and    the  deep  fascia    (with    its   fibres    running   transversely)   are 


Dissection  of  back  of 
terior  tibial  vessels  and 
muscles  bave  been  cut  and  drawn~aside 


ght  leg,  showing  relations  of  pos- 
gastrocnemius  and    soleus 


Post,  tibial  artery 

Post,  tibial  nerve 
Tendo  Achillis 
Flex.  lony.  halluci! 


/ 


ner  side  of  right  ankle,  showing  re!ati< 
as  they   pass  between  calcanium  and  i 


838  HUMAN    ANATOMY. 

divided  in  the  line  of  the  skin  wound,  the  inner  margin  of  the  soleus  displaced 
outward,  and  the  vessel,  with  its  venae  comites,  exposed,  the  posterior  tibial  nerve 
lying  to  its  outer  side.  A  little  lower — i.e.,  in  the  lower  third  of  the  leg — the 
incision  should  be  made  midway  between  the  inner  edge  of  the  tibia  and  the  inner 
edge  of  the  tendo  Achillis,  and  the  artery  will  be  found  lying  on  the  fibres  of  the 
flexor  longus  digitorum,  the  tendon  to  the  inner  side,  and  the  nerve  external. 

3.  To  ligate  the  vessel  at  the  inside  of  the  ankle  the  incision  should  be  semi- 
lunar in  shape,  parallel  with  the  margin  of  the  inner  malleolus,  and  about  half-way 
between  it  and  the  margin  of  the  tendo  Achillis.  After  dividing  the  deep  fascia — 
internal  annular  ligament — the  artery  will  be  found,  with  its  accompanying  veins, 
lying  between  the  flexor  longus  digitorum  and  tibialis  posticus  tendons  on  the  inside 
— each  in  a  separate  synovial  sheath  and  the  latter  near  the  malleolus — and  the 
nerve  and  flexor  longus  pollicis  tendon  on  the  outside.  The  sheaths  of  these  tendons 
should  not  be  opened. 

The  collateral  circulation  is  carried  on  from  above  the  ligature  by  (a)  the 
anterior  and  posterior  peroneal  arteries  and  their  muscular  and  communicating 
branches  ;  (6)  the  external  malleolar  branch  of  the  anterior  tibial ;  (c)  the  internal 
malleolar  (anterior  tibial);  (d)  the  dorsalis  pedis.  Anastomosing  respectively 
with  (a)  the  muscular  branches  and  the  communicating  branch  of  the  posterior 
tibial  ;  (<5)  the  external  plantar  branch  of  the  posterior  tibial  ;  (c)  the  internal  malle- 
olar (posterior  tibial)  ;  and  (d)  the  internal  and  external  plantars. 

1.  The  Nutrient  Artery. — The  nutrient  artery  to  the  tibia  (a.  nutritia  tibiae) 
may  arise  from  the  posterior  tibial,  either  above  or  ?below  the  origin  of  the  peroneal 
artery,  or  sometimes  it  arises  from  that  vessel.  It  pierces  the  tibialis  posticus  and 
enters  the  nutrient  foramen  on  the  posterior  surface  of  the  tibia,  sending  off,  before 
it  does  so,  some  small  muscular  branches. 

2.  The  Peroneal  Artery. — The  peroneal  artery  (a.  peronaea)  (Fig.  736)  is  by 
far  the  largest  of  the  collateral  branches  of  the  posterior  tibial.  It  arises  about  2.5  cm. 
below  the  lower  border  of  the  popliteus  muscle  and  is  at  first  directed  outward  and 
downward  towards  the  fibula,  and  then  passes  vertically  downward  along  the  inner 
surface  of  that  bone  to  a  point  about  2.5  cm.  above  the  ankle-joint,  where  it  termi- 
nates by  dividing  into  the  anterior  and  posterior  peroneal  arteries. 

Relations. — In  the  upper  part  of  its  course  it  is  covered  posteriorly  by  the 
soleus,  lying  between  that  muscle  and  the  tibialis  posticus.  Lower  down  it  passes 
beneath  the  flexor  longus  hallucis  or  else  traverses  the  substance  of  that  muscle,  and 
just  before  its  termination  it  emerges  from  beneath  the  muscle  and  becomes  super- 
ficial.     It  is  accompanied  by  two  venae  comites. 

Branches. — In  addition  to  numerous  muscular  branches  to  the  neighboring  muscles  and 
cutaneous  branches  to  the  integument  of  the  outer  border  of  the  cms,  the  peroneal  artery  gives 
off  the  following  vessels  : 

(a)  The  nutrient  artery  to  the  fibula  (a.  nutritiae  fibulae)  enters  the  nutrient  foramen  of  that 
bone. 

(b)  The  communicating  branch  (ramus  communicans)  passes  inward  over  the  lower  end  of 
the  tibia  and  beneath  the  tendo  Achillis,  a  short  distance  above  the  terminal  bifurcation  of  the 
peroneal.     It  inosculates  with  the  communicating  branch  of  the  posterior  tibial. 

(c)  The  anterior  peroneal  artery  (ramus  perforans)  is  one  of  the  terminal  branches  of  the 
peroneal.  It  passes  directly  forward  and,  perforating  the  interosseous  membrane,  bends  down- 
ward over  the  ankle-joint  to  the  dorsum  of  the  foot.  It  sends  branches  to  the  ankle-joint  and 
to  the  inferior  tibio-fibular  articulation,  as  well  as  to  the  peroneus  tertius  muscle,  beneath  which 
it  passes,  and  terminates  by  anastomosing  with  the  tarsal  and  metatarsal  branches  of  the  dorsalis 
pedis  and  with  the  external  plantar  artery  upon  the  side  of  the  foot. 

(d)  The  posterior  peroneal  artery  is  the  other  terminal  branch  of  the  peroneal,  of  which 
it  is  the  direct  continuation.  It  gives  origin  to  the  external  calcaneal  branch  which  ramifies 
over  the  outer  surface  of  the  os  calcis  and  terminates  by  anastomosing  with  the  internal  cal- 
caneal branch  of  the  posterior  tibial  artery  and  with  the  tarsal  and  metatarsal  branches  of  the 
dorsalis  pedis. 

Variations. — The  peroneal  artery  is  exceedingly  subject  to  variation.  It  is  rarely  absent, 
but  not  infrequently  it  terminates  over  the  outer  malleolus,  its  lower  portion  being  given  off  from 
a  branch  which  passes  across  from  the  posterior  tibial  and  represents  the  enlarged  anastomosis 


THE    POSTERIOR    TIBIAL   ARTERY. 


839 


Abductor  hallucis 


of  the  posterior  tibial  and  peroneal  communicating  branches.  Conversely,  when  the  lower  por- 
tion of  the  posterior  tibial  is  wanting,  it  may  be  replaced  by  the  peroneal,  which  then  gives  rise 
to  the  plantar  arteries.  Occasionally  the  peroneal  is  larger  than  usual,  and  may  give  origin  to 
the  anterior  tibial  artery,  and  it  may  give  off  the  nutrient  artery  for  the  tibia. 

The  anterior  peroneal  artery  is  sometimes  absent,  but  more  frequently  it  is  larger  than 
usual  and  inosculates  with  the  anterior  tibial.  Occasionally  the  lower  portion  of  this  latter  ves- 
sel is  wanting,  and  the  anterior  peroneal  may  then  take  its  place,  being  continued  downward 
upon  the  dorsum  of  the  foot  as  the  dorsalis  pedis  and  giving  off  the  branches  which  normally 
arise  from  that  vessel. 

3.  The  Communicating  Artery. — The  communicating  artery  (r.  commuaicans) 
(Fig.  736)  extends  transversely  outward  across  the  posterior  surface  of  the  tibia,  beneath 
the  tendon  of  the  flexor 

longus  hallucis  and  the  Fig.  739. 

tendo  Achillis,  and  an- 
astomoses with  the 
communicating  branch 
of  the  peroneal. 

4.  The  Internal 
Malleolar  Artery. — 
The  internal  malleolar 
artery  (a.  malleolaris 
posterior  medialis)  (  Fig. 
740)  passes  directly  in- 
ward, beneath  the  ten- 
dons of  the  flexor 
longus  digitorum  and 
tibialis  posticus,  to 
ramify  over  the  internal 
surface  of  the  inner 
malleolus,  anastomos- 
ing with  the  internal 
malleolar  branch  of  the 
anterior  tibial  artery. 

5.  The  Internal 
Calcaneal  Artery. — 
The  internal  calcaneal 
artery  (ramus  calcanei 
medialis)  (Fig.  736) 
arises  from  the  lower 
part  of  the  posterior 
tibial,  just  before  it 
divides  into  the  two 
plantar  vessels.  It  is 
frequently  represented 
by  several  branches 
which  descend  along 
the  inner  side  of  the 
tuberosity  of  the  os  calcis,  supplying  the  neighboring  parts  of  the  integument  and 
anastomosing  with  branches  of  the  internal  malleolar  and  posterior  peroneal  arteries. 

6.  The  Internal  Plantar  Artery.— The  internal  plantar  artery  (a.  plantaris 
medialis)  (Fig.  740)  is  the  smaller  of  the  two  terminal  branches  of  the  posterior  tibial. 
It  arises  in  the  groove  between  the  internal  malleolus  and  the  os  calcis  and  is  directed 
at  first  downward  and  forward,  under  cover  of  the  abductor  hallucis,  and  then  forward 
along  the  inner  border  of  the  foot,  between  the  abductor  hallucis  and  the  flexor  brevis 
digitorum,  terminating  opposite  the  head  of  the  first  metatarsal  bone  by  anastomosing 
with  one  or  other  of  the  two  branches  distributed  to  the  plantar  surface  of  the 
great  toe. 

Branches.— In  its  course  it  gives  off  muscular  branches  to  the  abductor  hallucis  and  the 
flexor  brevis  digitorum,  cutaneous  branches  to  the  integument  over  the  inner  border  of  the  foot, 
and  articular  branches  to  the  neighboring  tarsal  joints."    In  addition,  it  usually  gives  off  near  its 


From  external  calcaneal! 


Flexor  brevis  digitorum 
Abductor  minimi  diipti 
External  plantar  artery 


Interosseous  arteries 
dividing  into 

digital  branches 


Arteries  of  plantar 


ght  foot ;    superficial  dissection. 


840  HUMAN    ANATOMY. 

origin  a  larger  branch,  the  anastomotic  branch,  which  passes  beneath  the  abductor  hallucis  to 
gain  the  upper  border  of  that  muscle,  along  which  it  courses  forward,  giving  off  numerous 
branches  to  the  abductor  and  the  adjacent  integument  and  anastomosing  with  the  tarsal  and 
metatarsal  branches  of  the  dorsalis  pedis.  More  distally  it  gives  off  from  its  outer  surface  a 
varying  number  of  slender  superficial  digital  branches,  which  pass  obliquely  forward  and  out- 
ward across  the  sole  of  the  foot  to  anastomose  with  one  or  more  of  the  plantar  interosseous 
branches  from  the  plantar  arch. 

Variations. — Occasionally  the  superficial  digital  branches  of  the  internal  plantar  arise  from 
a  common  stem  which  anastomoses  with  a  branch  from  the  external  plantar  to  form  a  superfi- 
cial plantar  arch  beneath  the  superficial  fascia.  This  is  the  equivalent  of  the  superficial  palmar 
arch  of  the  hand. 

7.  The  External  Plantar  Artery. — The  external  plantar  artery  (a.  plautaris 
lateralis)  (Fig.  740)  is  the  larger  of  the  terminal  branches  of  the  posterior  tibial.  It 
passes  forward  and  outward  across  the  sole  of  the  foot,  at  first  between  the  flexor 
brevis  digitorum  and  the  flexor  accessorius,  and  then  in  the  interval  between  the  flexor 
brevis  digitorum  and  the  abductor  minimi  digiti.  Opposite  the  base  of  the  fifth  meta- 
tarsal bone  it  turns  somewhat  abruptly  inward  and  again  crosses  the  sole  of  the  foot, 
forming  the  plantar  arch  (arcus  plantaris),  which  terminates  at  the  proximal  end  of 
the  first  intermetatarsal  space  by  uniting  with  the  communicating  branch  from  the 
dorsalis  pedis. 

Relations. — In  the  first  part  of  its  course  the  external  plantar  lies  beneath  the 
abductor  hallucis  and  the  flexor  brevis  digitorum,  but  as  it  approaches  the  fifth  meta- 
tarsal it  becomes  more  superficial,  being  covered  only  by  the  skin  and  the  superficial 
and  plantar  fasciae.  It  rests  upon  the  flexor  accessorius  and  the  flexor  brevis  minimi 
digiti,  and  is  accompanied  by  the  external  plantar  nerve. 

The  plantar  arch,  on  the  contrary,  occupies  a  much  deeper  position.  It  passes 
beneath  the  tendons  of  the  flexor  longus  digitorum,  the  lumbricales,  and  the  oblique 
portion  of  the  adductor  hallucis,  resting  upon  the  proximal  ends  of  the  second,  third, 
and  fourth  metatarsals  and  upon  the  interosseous  muscles  which  occur  between  those 
bones. 

Branches. — The  external  plantar  artery  gives  rise  to  (a)  numerous  muscular  branches 
which  supply  the  various  muscles  of  the  plantar  surface  of  the  foot,  and  in  its  first  part  to 

(b)  Cutaneous  branches  which  supply  the  skin  over  the  sole  and  outer  border  of  the  foot, 
some  of  them  forming  anastomoses  with  branches  of  the  tarsal  and  metatarsal  branches  of  the 
dorsalis  pedis.     In  addition,  there  are  given  off  from  the  first  portion  of  the  artery — 

(c)  Calcaneal  branches,  one  or  more  in  number,  which  arise  near  the  commencement  of 
the  external  plantar  and  ramify  over  the  inner  surface  of  the  os  calcis,  anastomosing  with  the 
internal  calcaneal  branches  of  the  posterior  tibial. 

From  the  plantar  arch  a  number  of  vessels  are  given  off. 

(d)  The  articulating  branches  are  given  off  from  the  posterior  or  concave  surface  of  the 
arch  and  supply  the  tarsal  articulations. 

(e)  The  posterior  perforating  branches,  four  in  number,  arise  either  from  the  plantar  arch 
or  from  the  plantar  digital  branches  of  the  fourth  intermetatarsal  space.  They  ascend  in  the 
intermetarsal  spaces  between  the  heads  of  the  dorsal  interosseous  muscles  and  terminate  by  inos- 
culating with  the  first,  second,  and  third  dorsal  interosseous  arteries.  The  branch  which  passes 
through  the  first  intermetatarsal  space  is  much  larger  than  the  rest  and  inosculates  with  the  dor- 
salis pedis  artery  ;  it  is  sometimes  regarded  as  the  terminal  branch  of  that  vessel. 

{/)  The  plantar  interosseous  arteries  (aa.  metatarsae  plantares)  are  five  in  number,  and  are 
usually  numbered  in  succession  from  the  outer  side  of  the  foot  inward, — that  is  to  say,  in  the 
opposite  direction  to  the  intermetatarsal  spaces  in  which  they  lie.  The  first  arises  just  where 
the  external  plantar  artery  is  bending  inward  to  form  the  plantar  arch  and  passes  forward 
along  the  inner  border  of  the  abductor  minimi  digiti,  later  crossing  over  the  flexor  brevis  minimi 
digiti  to  reach  the  outer  surface  of  the  little  toe,  along  which  it  runs. 

The  second,  third,  and  fourth  plantar  interosseous  arteries  arise  in  succession  from  the 
plantar  arch  as  it  crosses  the  fourth,  third,  and  second  intermetatarsal  spaces,  and  pass  forward, 
resting  upon  the  interosseous  muscles  and  covered  by  the  tendons  of  the  flexor  longus  digitorum 
and  the  lumbricales,  and  more  distally  by  the  transverse  adductor  of  the  great  toe.  Just  before 
reaching  the  line  of  the  metatarso-phalangeal  articulations  each  artery  gives  off  an  anterior  per- 
forating branch,  which  passes  dorsally  to  communicate  with  the  corresponding  dorsal  interos- 
seous artery,  and  then  divides  into  two  plantar  digital  branches,  which  pass  onward  upon  the 
adjacent  sides  of  neighboring  digits. 


THE    POSTERIOR   TIBIAL   ARTERY. 


The  fifth  plantar  interosseous  artery  is  considerably  larger  than  the  others,  and  arises  from 
the  inner  end  of  the  plantar  arch,  opposite  the  communicating  branch  which  passes  between  the 
plantar  arch  and  the  dorsalis  pedis.  It  runs  forward  at  first  along  the  first  intermetatarsal  space 
and  then  upon  the  first  metatarsal  bone,  and  gives  off  a  digital  branch  which  passes  to  the  inner 
surface  of  the  great  toe  and  continues  on  towards  the  metatarso-phalangeal  joint  of  that  digit. 
Before  reaching  this,  however,  it  gives  off  an  anterior  perforating  branch  and  then  divides  into 
two  plantar  digital  branches,  which  supply  respectively  the  inner  side  of  the  second  and  the 
outer  side  of  the  great  toe. 

Since  the  communicating  branch  which  traverses  the  first  intermetatarsal  space  is  some- 
times regarded  as  the  terminal  portion  of  the  dorsalis  pedis  artery,  and  the  fifth  plantar  inter- 
osseous artery  seems  to  be,  upon  such  a  view,  the  branch  of  the  communicating  vessel,  the  fifth 
plantar  has   been   de- 
scribed as  a  branch  of  PiG   740 
the  dorsalis  pedis  ar- 
tery, under  the  name  of 
the  a.princeps  hallucis. 
There  can  be  no  doubt, 
however,  that  both  the 
communicating    and 
the  princeps  are  equiv- 
alent to  the  other  pos- 
terior perforating  and 
plantar    interosseous 
arteries. 

Variations. — The 
external  plantar  artery 
may  be  quite  small,  in 
which  case  the  plantar 
arch  seems  to  be  a 
continuation  from  the 
anterior  tibial  artery 
through  the  posterior 
perforating  branch  of 
the  first  intermetatar- 
sal space.  The  arch 
is  occasionally  double, 
owing  to  its  division 
at  its  origin  into  two 
stems  which  reunite 
opposite  the  first  inter- 
metatarsal space.  The 
first  plantar  interosse- 
ous may  arise  by  a 
common  stem  with-the 
second,  and,  con- 
versely, one  or  more 
of  the  plantar  digital 
branches  may  have  an 
independent  origin 
from  the  arch. 

Anastomoses 
of  the  Posterior 
Tibial  Artery. — A 

collateral  circulation 

for  the  posterior  tibial  after  interruption  of  that  vessel  below  the  origin  of  the 
peroneal  may  readily  be  established  through  the  anastomoses  which  its  branches 
form  with  those  of  the  peroneal  and  those  of  the  anterior  tibial.  The  anasto- 
moses with  the  peroneal  are  between  the  communicating  branches  of  the  two 
arteries,  between  the  anterior  peroneal  and  the  external  plantar,  and  between  the 
posterior  peroneal  and  the  internal  calcaneal.  With  the  anterior  tibial  artery  there 
is  communication  through  the  malleolar  branches  of  the  two  arteries,  through  the 
anastomotic  branch  of  the  external  plantar  and  the  tarsal  and  metatarsal  branches 
of  the  dorsalis  pedis,  and  through  the  union  of  anterior  and  posterior  perforating 
branches  of  the  plantar  arch  and  the  plantar  interosseous  arteries  with  the  dorsalis 
pedis  and  dorsal  interosseas. 


Arteries  of  plantar  surface  of  right  foot ;   deeper  dissectio 


■842 


HUMAN    ANATOMY. 


THE   ANTERIOR  TIBIAL   ARTERY. 

The  anterior  tibial  artery  (a.  tibialis  anterior)  (Figs.  742,  743)  is  the  other  terminal 
branch  of  the  popliteal.  It  begins  at  the  lower  border  of  the  popliteus  muscle,  and  is  at 
first  directed  forward,  passing  between  the  tibia  and  fibula  and  the  two  uppermost  slips 
of  origin  of  the  tibialis  posticus,  above  the  upper  border  of  the  interosseous  membrane. 
It  then  bends  downward  and  traverses  the  entire  length  of  the  crus  to  the  front  of  the 
ankle-joint,  where  it  becomes  the  dorsalis  pedis  artery.  Its  course  may  be  represented 
by  a  line  drawn  from  the  head  of  the  fibula  to  a  point  half-way  between  the  two  malleoli. 

Relations. — In  its  course  down  the  leg  the  anterior  tibial  artery  rests  posteriorly 
upon  the  interosseous  membrane,  to  which  it  is  more  or  less  firmly  united  by  fibrous 
bands  ;  in  the  lower  quarter  of  its  course  it  rests  upon  the  front  of  the  tibia.  Anteriorly , 
in  the  upper  two-thirds  of  its  course,  it  is  overlapped  by  the  tibialis  anticus,  lying  along 
the  deep  edge  of  the  connective-tissue  partition  which  separates  that  muscle  from  the  ex- 
tensor longus  digitorum  and  the  extensor  proprius  hallucis.  Lower,  however,  it  is 
superficial,  and  just  above  the  ankle-joint  it  is  crossed  obliquely,  from  without  inward, 
by  the  tendon  of  the  extensor  proprius  hallucis,  and  then  passes  beneath  the  anterior 
annular  ligament.  Internally  to  it  is  the  tibialis  anticus,  and  at  the  ankle-joint  the  ten- 
don of  the  extensor  proprius  hallucis  ;  externally  it  has  in  its  upper  third  the  extensor 
longus  digitorum,  in  its  middle  third  the  extensor  proprius  hallucis,  and  at  the  ankle  the 
inner  tendon  of  the  extensor  longus  digitorum.  The  anterior  tibial  nerve  lies  to  the 
outer  side  of  the  artery  in  its  upper  and  lower  thirds  ;  in  the  middle  third  of  the  leg  it 
is  usually  in  front  of  the  vessel. 

Variations. — The  anterior  tibial  artery,  as  it  occurs  in  man,  appears  to  be  the  result  of  a  union 
of  two  originally  distinct  vessels,  both  of  which  arise  from  the  primitive  peroneal  artery  and  pass  to 

the  front  of  the  leg.     The  up- 
p  G   _  permost  of  these  forms  the 

greater  portion  of  the  artery, 
while  the  lower  one,  which 
is  represented  by  the  anterior 
peroneal  artery,  forms  only 
the  lower  part  of  the  anterior 
tibial  and  its  continuation 
upon  the  dorsum  of  the  foot, 
the  dorsalis  pedis.  In  case  of 
failure  in  the  union  of  these 
two  vessels,  the  anterior  tibial 
may  appear  to  terminate  in 
muscular  branches  a  short 
distance  above  the  ankle- 
joint,  the  dorsalis  pedis  being 
the  continuation  of  the  an- 
terior peroneal.  This  ar- 
rangement is  not  infrequent ; 
more  rarely  the  upper  portion 
of  the  vessel  is  greatly  re- 
duced, being  represented 
only  by  a  small  stem  which 
gives  off  the  posterior  and 
anterior  recurrent  branches 
as  well  as  branches  to  the 
popliteus  muscle,  the  front  of 
of  the  leg,  in  such  cases,  being 
sometimes  supplied  by  an  in- 
dependentperforating  branch 
from  the  posterior  tibial. 

Practical  Consid- 
erations.— The  anterior 
tibial  artery  is  more  often 
wounded  than  the  pos- 
terior tibial  because  of  its 
more  exposed  position  on  the  front  of  the  limb  and  its  close  relation  to  the  tibia.  It  is  not 
infrequently  lacerated  by  the  sharp  edge  of  a  fragment  in  fracture  of  that  bone.      It  is 


Peroneus  brev 


Ant.  tibial  nerve 
Ant.  tibial  artery 
Companion  vein 


THE   ANTERIOR    TIBIAL    ARTERY. 


843 


Tendo  patella; 

Inferior  internal  articular 


rarely  the  subject  of  aneurism.  Ligation  may  be  done  at  ( 1)  the  upper;  (2)  the  middle; 
or  (3).tne  lower  third.  The  line  of  the  artery  is  from  a  point  midway  between  the  exter- 
nal tibial  tuberosityand 

the  head  of  the  fibula  to  Fig.  742. 

the  middle  of  the  anteri- 
or intermalleolar  space. 
1.   When  through 
an    incision    made    at 
this  line  the  deep  fascia 
is  reached  and  divided, 
the  interspace  in  which 
the  artery  lies  should 
be  sought  for.       It  is 
that  between  the  tibi- 
alis    anticus    and    the 
extensor   longus    digi- 
torum,  is  the  only  in- 
termuscular interstice 
in  the   upper   anterior 
tibial   region,  is   about 
an  inch  or  an  inch  and 
.    a  quarter  external    to 
the  tibial  crest,  and  a 
half  to    three-quarters 
of  an  inch  internal  to 
the  septum  which   di- 
vides the  extensor  lon- 
gus from  the  peroneus 
longus.      This   septum 
is  often  marked  by   a 
white  line  visible  before 
the  deep   fascia  is  di- 
vided ;    or  it  may   be 
recognized  by  slipping 
a  director  outward  be- 
neath the  aponeurosis 
until  its  point  is  firmly 
arrested.       The    inter- 
space   containing    the 
anterior    tibial    artery 
will  then  be  internal  to 
this  and  can  be  felt  as 
a  line  of  lessened  resist- 
ance   when    the    fore- 
finger is  pressed  length- 
wise along  the  muscles 
(Treves).       On     the 
other  hand,  the  apon- 
eurotic   partition     be- 
tween   the    extensor 
and    the    peroneus  — 
external   to   the    inter- 
space    sought     for  — 
resists    and     vibrates 
under  the  point  of  the 
director    or    the    fore- 
finger (Farabeuf).     At 
the  bottom  of  the  interspace  the  artery  will  be  found  lying  upon  the  interosseous 
membrane  to  the  outer  side  of  the  tibia  and  with  the  nerve  external  to  it. 


alleolar  artery 


Dorsal  interosseous 


tendon  of 
:tensor  brevis  digi 
Dorsalis  pedis 

Communicating  arter\ 
-    hallucis 

perforating  arterii: 


844  HUMAN   ANATOMY. 

2.  At  the  middle  of  the  limb  the  same  interspace  is  found — usually  more 
easily,  as  there  is  often  some  yellowish-white  fatty  tissue  lying  between  the  muscles 
and  seen  as  a  line  on  the  surface  of  the  deep  fascia — and  is  opened.  The  artery 
which  still  lies  on  the  interosseous  membrane  will  be  found  in  the  deeper  space  thus 
disclosed  between  the  extensor  proprius  pollicis  and  the  tibialis  anticus. 

3.  At  the  lower  third  an  incision  on  the  same  line  will  expose  the  vessel  lying 
usually  in  the  innermost  of  the  two  interstices  found  at  that  part  of  the  limb,  viz., 
that  between  the  tibialis  anticus  and  the  extensor  proprius  pollicis.  Occasionally 
it  will  be  found  to  the  outer  side  of  the  tendon  of  the  extensor  proprius — the  second 
tendon  from  the  tibia — in  the  space  between  that  muscle  and  the  extensor  longus 
digitorum.      The  vessel  lies  on  the  front  of  the  tibia,  with  the  nerve  external. 

The  collateral  circulation  is  carried  on  from  above  the  ligature  by  (<z)  the  pero- 
neals ;  and  (b)  the  posterior  tibial,  anastomosing  respectively  with  (a)  the  external 
malleolar,  the  branches  of  the  dorsalis  pedis  and  the  plantar  ;  and  (b)  the  internal 
malleolar  from  below,  assisted  by  the  many  small  anastomotic  vessels  piercing  the 
interosseous  membrane  and  derived  from  the  two  tibials. 

Branches. — In  addition  to  numerous  muscular  branches  which  supply  the 
adjacent  muscles,  the  anterior  tibial  artery  gives  off  the  following  : 

1.  The  superior  fibular  branch  (ramus  fibularis)  is  a  small  vessel  which  arises 
from  the  anterior  tibial  immediately  below  its  origin  ;  occasionally  it  arises  by  a  com- 
mon trunk  with  the  posterior  tibial  recurrent  or  else  from  the  lower  part  of  the 
popliteal.  It  passes  upward  behind  the  neck  of  the  fibula,  traversing  the  substance 
of  the  soleus,  and  sends  branches  to  that  muscle  and  to  the  peroneus  longus,  and 
anastomoses  with  the  external  inferior  articular  branch  of  the  popliteal. 

2.  The  posterior  recurrent  tibial  artery  (a.  recurrens  tibialis  posterior)  arises 
while  the  anterior  tibial  is  still  upon  the  posterior  surface  of  the  leg.  It  passes  upward 
between  the  popliteal  muscle  and  the  posterior  ligament  of  the  knee-joint,  both  of 
which  it  supplies,  and  terminates  by  anastomosing  with  the  external  and  internal 
inferior  articular  branches  of  the  popliteal. 

3.  The  anterior  recurrent  tibial  artery  (a.  recurrens  tibialis  anterior)  is  given 
off  just  after  the  anterior  tibial  has  reached  the  front  of  the  leg.  It  runs  upward  in 
the  substance  of  the  tibialis  anticus  and  over  the  outer  tuberosity  of  the  tibia,  and 
terminates  by  taking  part  in  the  formation  of  the  circumpatellar  anastomosis.  It 
gives  branches  to  the  tibialis  anticus,  the  extensor  longus  digitorum,  the  capsule  of 
the  knee-joint,  and  the  adjacent  integument.  This  artery  is  of  importance  in  the 
establishment  of  a  collateral  circulation  after  ligation  of  the  popliteal  artery  (page  834) , 
on  account  of  its  anastomoses  with  the  descending  branch  of  the  external  circumflex 
artery  and  with  the  anastomotica  magna. 

4.  The  internal  malleolar  artery  (a.  malleolaris  anterior  medialis)  arises  from 
the  inner  surface  of  the  anterior  tibial,  a  little  above  the  ankle.  It  passes  inward 
beneath  the  tibialis  anticus,  over  the  surface  of  the  inner  malleolus,  and  terminates 
by  anastomosing  with  the  malleolar  branch  of  the  posterior  tibial,  the  internal  plantar, 
and  the  internal  calcaneal  arteries. 

5.  The  external  malleolar  artery  (a.  malleolaris  anterior  lateralis)  arises  from 
the  outer  surface  of  the  anterior  tibial,  usually  a  little  below  the  internal  malleolar. 
It  is  directed  outward  and  downward  beneath  the  extensor  longus  digitorum  and  the 
peroneus  tertius,  over  the  surface  of  the  external  malleolus,  and  anastomoses  with 
branches  from  the  anterior  and  posterior  peroneal  arteries. 

Anastomoses  of  the  Anterior  Tibial  Artery. —  Collateral  circulation  is 
readily  established,  in  cases,  of  interruption  of  the  anterior  tibial  artery,  by  means 
of  its  abundant  anastomoses  with  branches  of  the  posterior  tibial.  Thus  there  are 
rich  anastomoses  between  the  internal  malleolar  branch  of  the  anterior  tibial  and  the 
malleolar  branch  of  the  posterior  tibial,  and  between  the  external  malleolar  branch  of 
the  anterior  tibial  and  the  anterior  and  posterior  peroneal  branches.  Further,  since 
the  dorsalis  pedis  artery  is  the  continuation  of  the  anterior  tibial,  it  will  assist  mate- 
rially in  the  collateral  circulation  by  the  anastomoses  of  its  tarsal  and  metatarsal 
branches  with  the  plantar  and  peroneal  arteries  and  by  its  connections  with  the 
plantar  arch. 


THE    DORSAL   ARTERY. 


845 


Peroneus  b  rev  is 
Peroneus  longus 


Dorsal  is  ped 


THE  DORSAL  ARTERY  OF  THE  FOOT. 

The  dorsal  artery  of  the  foot  (a.  dorsalis  pedis)  (Fig.  743)  is  the  continuation  of 
the  anterior  tibial  beyond  the  ankle-joint.  It  extends  to  the  proximal  portion  of  the 
first  intermetatarsal  space,  where  it  receives  the  large  fourth  perforating  branch  of  the 
plantar  arch,  and  is  thence  continued  forward  along  the  intermetatarsal  space  as  the 
a.  dorsalis  hallucis. 

Relations. — The  dorsalis  pedis  is  covered  in  the  proximal  portion  of  its  course  by 
the  anterior  annular  ligament,  and  is  crossed  just  before  it  reaches  the  intermetatarsal 
space  by  the  tendon  of  the  extensor  brevis  digitorum  which  passes  to  the  great  toe.  It 
rests    successively  upon 

the  anterior  ligament  of  743- 

the  ankle-joint,  the  head 
of  the  astragalus,  the 
astragalo-scaphoid  liga- 
ment, the  dorsal  surface 
of  the  scaphoid  bone,  the 
dorsal  scapho-cuneiform 
ligament,  and  the  in- 
tercuneiform ligaments 
which  extend  between 
the  middle  and  internal 
cuneiform  bones.  Ex- 
ternally it  is  separated 
from  the  innermost  ten- 
don of  the  extensor  lon- 
gus digitorum  and  from 
the  extensor  brevis  digi- 
torum by  the  inner  termi- 
nal branch  of  the  anterior 
tibial  nerve,  and  inter- 
nally it  is  in  relation  with 
the  tendon  of  the  exten- 
sor hallucis  proprius. 

Branches.  —  In 
addition  to  numerous  cu- 
taneous branches  to  the 
skin  of  the  dorsum  of 
the  foot  and  muscular 
branches  to  the  extensor 
brevis  digitorum,  the 
dorsalis  pedis  gives  rise 
to  the  following  vessels. 

1.  The  internal 
tarsal    branches    (aa. 

tarseae  mediates )  are  one  portion  of  anterior  annular  ligament  sti"  in  place' 

or  more  small  vessels  which  pass  over  the  outer  border  of  the  foot,  supplying  the 
integument  and  the  tarsal  articulations  and  anastomosing  with  the  internal  malleolai 
and  internal  plantar  arteries. 

2.  The  external  tarsal  branch  (a.  tarsea  lateralis)  arises  opposite  the  head 
of  the  astragalus  and  passes  outward  and  forward  over  the  scaphoid  and  cuboid 
bones,  under  cover  of  the  extensor  brevis  digitorum.  It  gives  branches  to  that 
muscle,  to  the  skin,  and  to  the  tarsal  articulations,  and  anastomoses  with  the  external 
malleolus  and  anterior  peroneal  arteries  above,  with  the  external  plantar  laterally,  and 
with  the  metatarsal  below. 

3.  The  metatarsal  branch  (a.  arcuata)  arises  over  the  internal  cuneiform  bone 
and  is  directed  at  first  laterally  forward  and  then  laterally  over  the  bases  of  the  four 
outer  metatarsal  bones  and  beneath  the  tendons  of  the  extensor  longus  and  extensoi 


:g  relations  of  vessels  and  nerves  in  vicinity  of  left  ankle  ; 
portion  of  anterior  ; 


846  HUMAN    ANATOMY. 

brevis  digitorum.  It  thus  forms  an  arch  upon  the  dorsal  surface  of  the  foot  corres- 
ponding in  position  with  the  plantar  arch  below.  It  anastomoses  laterally  with  the 
external  tarsal  and  with  the  external  plantar,  and  opposite  each  of  the  intermetatarsal 
spaces  which  it  passes — the  second,  third  and  fourth — gives  off  a  dorsal  interosse- 
ous artery  (a.  metatarsea  dorsalis). 

Each  of  these  passes  forward  along  its  intermetatarsal  space,  and,  immediately 
beyond  its  origin,  gives  off  a  posterior  perforating  branch  which  communicates  directly 
with  the  corresponding  posterior  perforating  branch  of  the  plantar  arch.  At  the  distal 
end  of  its  intermetatarsal  space  each  artery  gives  off  an  anterior  perforating  branch 
which  unites  with  the  similar  branch  of  the  corresponding  plantar  interosseous,  and 
then  divides  into  two  dorsal  digital  branches  (aa.  digitales  dorsales)  which  pass  along 
the  adjacent  surfaces  of  two  neighboring  digits  and  anastomose  with  one  another  and 
with  the  plantar  digital  branches. 

4.  The  dorsal  interosseous  branch  of  the  first  intermetatarsal  space 
appears  to  be  the  continuation  of  the  dorsalis  pedis,  and  is  usually  termed 
the  a.  dorsalis  hallucis.  Its  course  is  exactly  similar  to  that  of  each  of  the 
other  dorsal  interosseous  arteries,  except  that,  in  addition  to  the  anterior  dorsal 
perforating  and  terminal  dorsal  digital  branches,  it  gives  off,  not  far  from  its 
origin,  a  third  digital  branch  which  passes  forward  along  the  outer  surface  of  the 
great  toe.  The  posterior  communicating  artery  which  should  arise  from  this  vessel 
is  represented  by  the  large  branch  by  which  the  dorsalis  pedis  communicates  with  the 
plantar  arch. 

Variations. — The  origin  of  the  dorsalis  pedis  from  the  peroneal  by  means  of  the  anterior 
peroneal  branch  has  already  been  noted  in  connection  with  the  variations  of  the  anterior  tibial 
artery.  Another  origin  which  has  been  observed  is  from  the  external  plantar  artery,  which 
sends  upward  through  the  astragalo-calcaneal  canal  a  large  branch  which  is  continued  distally 
upon  the  dorsum  of  the  foot  and  gives  off  the  tarsal  and  metatarsal  branches.  This  vessel  is 
represented  in  the  adult  by  a  small  branch  which  arises  from  the  external  tarsal  artery  and  pur- 
sues the  course  indicated  to  anastomose  with  the  external  plantar  ;  it  appears  to  be  much  more 
highly  developed  in  the  embryo  than  in  the  adult  (Leboucq). 

Other  variations  in  the  dorsalis  pedis  and  its  branches  depend  upon  a  correlation  which 
exists  between  the  development  of  the  dorsal  and  plantar  system  of  vessels.  If,  for  example, 
the  plantar  interosseae  are  well  developed,  they  will,  through  the  anterior  perforating  branches, 
furnish  the  main  blood-supply  for  the  dorsal  digital  branches,  and  the  dorsal  interosseous  ves- 
sels, as  well  as  the  metatarsal,  may  be  much  reduced.  Or  the  plantar  arch,  through  the  pos- 
terior perforating  branches,  may  be  the  main  supply  for  the  dorsal  interosseous  vessels,  and  the 
dorsalis  pedis'  itself  may  be  diminished  in  size  or  may  even  terminate  in  a  net-work  of  small 
vessels  over  the  dorsal  surface  of  the  tarsus. 

DEVELOPMENT  OF  THE  ARTERIES. 

In  the  preceding  pages  some  of  the  more  important  facts  regarding  the  development  of  the 
arteries  have  been  mentioned  in  connection  with  the  anomalies  in  whose  production  they  are 
concerned  ;  these  facts  may  now  be  briefly  restated  in  a  more  connected  manner. 

At  an  early  stage  of  development,  while  the  heart  lies  far  forward  beneath  the  pharyngeal 
region  and  its  ventricle  is  still  undivided,  the  blood  leaves  it  by  a  single  vessel  which  passes  forward 
along  the  mid-ventral  line  of  the  pharynx  and  divides  to  form  two  ventral  longitudinal  stems,  from 
each  of  which  six  lateral  branchial  vessels  arise,  the  fifth  vessel  of  each  stem,  counting  from 
before  backward,  being  quite  rudimentary  and  closely  associated  with  the  fourth.  These 
branchial  vessels  pass  dorsally  in  the  branchial  arches  to  the  dorsal  surface  of  the  pharynx,  where 
those  of  each  side  unite  to  form  a  longitudinal  stem  which  passes  backward,  and  at  about  the 
level  of  the  eighth  cervical  vertebra  unites  with  its  fellow  of  the  opposite  side  to  form  a  single 
longitudinal  trunk,  the  dorsal  aorta  (Fig.  677).  This  is  continued  backward  to  the  posterior 
extremity  of  the  trunk,  lying  immediately  ventral  to  the  vertebral  column.  From  the  anterior 
ends  of  the  ventral  and  dorsal  longitudinal  stems  branches  pass  forward  into  the  cranial  region; 
and  from  the  dorsal  longitudinal  stems  and  the  dorsal  aorta  lateral  and  ventral  branches  are 
given  off  in  regular  segmental  succession.  The  modifications  undergone  by  the  branchial  arch 
vessels  in  the  course  of  development  may  first  be  traced  and  then  the  arrangement  and  modifica- 
tions of  the  segmental  branches  will  be  considered. 

The  first  modification  of  the  branchial  arch  vessels  consists  in  the  disappearance  of  the  two 
anterior  ones  on  either  side,  and  then  follow  a  number  of  changes  which  may  be  briefly  stated  as 
follows.  (1)  The  portions  of  the  dorsal  longitudinal  stems  intervening  between  the  third  and 
fourth  branchial  vessels  disappear  ;  (2)  the  fifth  branchial  vessels  disappear  ;  (3)  the  sixth  loses 
its  connection  with  the  dorsal  longitudinal  stem  on  the  right  side  5(4)  the  proximal  portion  of 


DEVELOPMENT  OF  THE  ARTERIES. 


847 


the  ventral  longitudinal  stem  divides  in  the  frontal  plane  into  two  portions,  one  of  which  is  con- 
nected with  the  sixth  branchial  vessels,  while  the  other  retains  the  remaining  ones  ;  and  (5)  the 
posterior  portion  of  the  right  dorsal  longitudinal  stem  disappears,  so  that  the  dorsal  aorta  is 
formed  only  by  the  left  stem  ( Fig.  67S ) .  As  the  result  of  these  changes  the  anterior  portion  of  the 
ventral  longitudinal  stem  becomes  the  external  carotid  artery  ;  the  anterior  portion  of  the  dorsal 
longitudinal  stem  the  internal  carotid  ; 


Fig.  744. 


Diagrams  illustrating  primary  arrangement  (A)  and  second- 
ary modifications  (B)  in  branchial  arch  vessels.  TA,  truncus 
arteriosus;  I-VI,  aortic  bows;  VA,  DA,  ventral  and  dorsal 
aortaa  ;  A,  aorta;  A  A,  aortic  arch;  /,  innominate  artery;  CC, 
CE,  CI,  common,  external  and  internal  carotids;  ^subclavian; 
P,  pulmonary  artery  ;  da,  ductus  arteriosus. 


the  third  branchial  vessel  becomes  the 
connection  between  the  two  carotids  ; 
the  fourth  branchial  vessel  of  the  left 
side,  together  with  the  left  dorsal  longi- 
tudinal stem,  becomes  the  arch  of  the 
aorta  ;  the  right  fourth  branchial  vessel 
and  the  persisting  portion  of  the  right 
dorsal  longitudinal  stem  become  the 
proximal  portion  of  the  right  subclav- 
ian artery  ;  the  sixth  branchial  vessels 
become  the  pulmonary  arteries,  the 
persisting  connection  of  the  left  one 
with  the  aortic  arch  being  the  ductus 
arteriosus  ;  the  proximal  portion  of  the 
ventral  longitudinal  trunk  which  re- 
mains connected  with  the  sixth  vessels 
becomes  the  pulmonary  aorta,  while 
the  other  portion  becomes  the  prox- 
imal part  of  the  aortic  arch.  These 
changes  are  shown  diagrammatically 
in  Fig.  744,  A  and  B. 

From  the  forward  prolongations 
of  the  carotid  arteries  the  vessels  which 
supply  the  cranial  structures  are  de- 
veloped, and  lateral  branches  also  pass  from  the  carotids  to  the  structures  which  are  formed 
from  the  branchial  arches.  Of  these  branches  the  superior  thyroid,  lingual,  and  facial  arteries  are 
probably  from  the  beginning  connected  with  the  external  carotid,  but  the  greater  part  of  the 
internal  maxillary  takes  its  origin  from  the  internal  carotid  and  only  secondarily  becomes  con- 
nected with  the  external  one  (page  743). 

From  the  dorsal  longitudinal  stems,  posterior  to  the  point  at  which  the  sixth  branchial 
vessels  join  them,  branches  pass  off  laterally  to  each  of  the  cervical  segments,  the  most  anterior 
pair  accompanying  the  hypoglossal  nerve  and  passing  to  the  occipital  segments  with  which  the 
nerve  is  associated.     Later,  as  the  heart  recedes  towards  its  final  position  in  the  thorax,  carrying 

with  it  the  dorsal  longitudinal  stems,  the  majority  of 
the  cervical  lateral  branches  separate  from  the  stems 
and  are  represented  in  the  adult  by  the  segmental 
muscular  and  spinal  branches  which  arise  from  the 
vertebral  artery.  The  seventh  branches,  however, 
retain  their  connection  with  the  longitudinal  stems 
and  become  the  subclavian  arteries  of  the  adult. 

Throughout  the  entire  length  of  the  dorsal  aorta 
segmental  branches  are  distributed  not  only  to  the 
body-wall,  but  also  to  the  viscera,  and  in  each  seg- 
ment two  typical  sets  of  visceral  branches  may  be 
distinguished, — a  pair  of  lateral  branches  which  pass 
laterally  beneath  the  peritoneum  to  the  paired  viscera, 
and  a  single  median  branch  which  passes  ventrally  in 
the  mesentery  and  is  supplied  to  the  digestive  tract 
and  its  derivatives  (Fig.  745).  The  lateral  branches 
to  the  body-wall  persist  in  the  adult  as  the  inter- 
costal lumbar  and  lateral  sacral  branches,  the  fifth 
lumbar  branches  entering  into  the  formation  of  the 
iliac  arteries.  The  visceral  branches  belonging  to 
both  sets,  however,  undergo  much  modification, 
some  disappearing  and  others  fusing,  so  that  little  trace  of  their  primarysegmental  arrangement 
is  to  be  recognized  in  the  adult.  Representatives  of  the  paired  visceral  branches  are  to  be 
found  in  the  bronchial,  suprarenal,  renal,  and  spermatic  (ovarian)  arteries,  and  in  the  fcetus 
the  umbilical  arteries  represent  the  paired  branches  of  the  third  lumbar  segment.  At  an 
early  stage,  however,  these  vessels  make  connections  with  branches  of  the  iliac  arteries  and 


FiG.745. 


Diagram  showing  fundamental  arrangement 
of  branches  from  aorta  {A)  ;  B,  lateral  branches 
to  body-wall;  C,  paired  visceral,  D,  unpaired 
visceral  branch  ;   E.  peritoneum. 


HUMAN    ANATOMY. 


then  lose  their  original  connections  with  the  aorta,  so  that  they  seem  in  the  foetus  to  arise 
from  the  iliac  vessels,  and  these  latter,  although  primarily  somatic  in  their  distribution,  give  off 
a  number  of  visceral  branches. 

Of  the  unpaired  visceral  branches  representatives  are  to  be  found  in  the  thoracic  region  in 
the  oesophageal  and  mediastinal  vessels  and  in  the  abdomen  m  the  cceliac  axis  and  the  superior 
and  inferior  mesenteric  arteries,  the  superior  mesenteric  representing  the  omphalo-mesenteric 
or  vitelline  arteries  of  the  embryo  which  primarily  arise  by  several  roots,  only  the  lowest  of  which 
persists  to  form  the  adult  vessel. 

According  to  the  general  plan  of  the  embryonic  arterial  system  thus  outlined,  the  only  ves- 
sels which  have  primarily  a  longitudinal  course  are  the  dorsal  and  ventral  longitudinal  stems, 
the  dorsal  aorta,  and  its  prolongation,  the  a.  sacra  media.  In  the  adult,  however,  several  other 
longitudinal  vessels  exist,  such,  for  instance,  as  the  vertebrals,  the  internal  mammaries,  and  the 
superficial  and  deep  epigastrics.  All  these  vessels  are  secondary  formations  due  to  the  end-to- 
end  anastomoses  of  upwardly  and  downwardly 
directed  branches  of  the  lateral  segmental  ves- 
sels. The  internal  mammaries  and  the  epigas- 
trics (Fig.  746)  are  formed  in  this  manner  from 
branches  of  the  intercostal  arteries,  with  which 
they  remain  connected  to  a  greater  or  less  ex- 
tent ,  the  vertebrals  are  formed  from  branches 
of  the  lateral  cervical  vessels,  and  become  inde- 
pendent stems  by  the  separation  of  these  vessels 
from  the  dorsal  longitudinal  stems,  as  already 
described. 

The  arteries  of  the  limbs  are  formed,  as 
already  stated,  by  the  lateral  somatic  branches 
of  the  seventh  cervical  and  fifth  lumbar  segments 
respectively,  but  in  both  limbs  a  series  of  changes 
is  necessary  before  the  adult  arrangement  is 
acquired.  In  the  arm  the  subclavian  artery  at 
first  extends  as  a  single  main  stem  as  far  as  the 
carpus,  where  it  terminates  by  dividing  into 
digital  branches  for  the  fingers  (Fig.  747,  A). 
Throughout  its  course  in  the  forearm  it  lies 
between  the  two  bones,  resting  on  the  interos- 
seous membrane,  in  the  position  occupied  by 
the  adult  anterior  interosseous  artery ;  from 
the  upper  part  of  this  portion  of  its  course  a 
branch  is  given  off  which  takes  a  more  super- 
ficial course,  accompanying  the  median  nerve. 
This  median  artery  gradually  becomes  larger, 
while  the  anterior  interosseous  undergoes  a  cor- 
responding retrogression,  and  eventually  the 
median,  by  fusing  with  the  lower  portion  of  the 
interosseous;  forms  the  main  channel  for  the  digi- 
tal branches  and  becomes  the  principal  artery  of 
the  forearm  (Fig.  747,  B).  A  further  stage  is  marked  by  the  development  of  the  ulnar  artery  as  a 
branch  from  the  brachial,  and  this,  extending  down  the  ulnar  side  of  the  forearm,  unites  with  the 
median  to  form  a  carpal  arch  from  which  the  digital  branches  arise  (C).  Later  there  develops 
high  up  upon  the  brachial  a  superficial  brachial  artery,  which,  after  traversing  the  brachium, 
passes  down  the  radial  side  of  the  forearm  and  near  the  wrist  passes  to  the  posterior  surface, 
dividing  over  the  carpus  into  branches  for  the  dorsum  of  the  thumb  and  index-finger.  After  the 
appearance  of  the  ulnar  artery  a  retrogression  of  the  median  begins,  whereby  it  becomes  the 
a.  comes  nervi  mediani  of  the  adult ;  a  branch,  the  superficial  volar,  arises  from  the  lower  part  of 
the  superficial  brachial  and  passes  downward  into  the  palm  to  unite  with  the  palmar  arch  already 
present  (D)  ;  and,  finally,  a  branch  arising  from  the  lower  part  of  the  brachial  anastomoses  with 
the  superficial  brachial  just  below  the  bend  of  the  elbow  and.  together  with  the  antibrachial  part 
of  the  superficial  brachial,  forms  the  radial  artery.  The  upper  part  of  the  superficial  brachial 
then  degenerates  until  it  is  normally  represented  in  the  adult  by  a  small  branch  of  the  brachial 
which  passes  to  the  biceps  muscle  ( E) . 

In  the  leg  the  changes  are  equally  complicated.  Primarily  it  is  the  sciatic  artery  which 
forms  the  main  stem,  extending  the  entire  length  of  the  posterior  surface  of  the  limb  into  the 
plantar  surface  of  the  foot,  where  it  divides  into  the  digital  branches  (Fig.  748,  A).  The  ex- 
ternal iliac  at  this  stage  is  a  relatively  slender  vessel  which  extends  but  a  short  distance  down  the 
thigh  and  terminates  in  what  is  later  the  profunda  femoris.     In  a  later  stage  there  arises  from 


Trunk-arteries  of  embryo  of  six  weeks,  showing 
origin  of  internal  mammary  (ijn)  and  epigastric  arteries 
(se,  superficial,  de,  deep) ;  a,  aorta  ;  v,  vertebral ;  ci, 
common  iliac,  continuing  as  large  hypogastric  (h) ; 
external  iliac,  giving  off  deep  epigastric  and  femoral, 
is  still  small.     X  5.     (Mall.) 


DEVELOPMENT  OF  THE  ARTERIES. 


849 


the  external  iliac  a  vessel  (safih)  which  accompanies  the  internal  saphenous  nerve  down  the 
leg  and,  entering  the  foot,  takes  from  the  original  main  stem  its  digital  branches  (£).  From  this 
saphenous  artery  a  branch  is  given  off  which  pierces  the  substance  of  the  adductor  magnus  mus- 

Fig.  747. 


J/k 


Diagrams  illustrating  development  of  arteries  of  upper  limb ;  b,  brachial  ;  i,  interosseous  ; 
d,  digital ;  m,  median;  u,  ulnar;  sbt  superficial  brachial  ;  r,  radial. 


Fig.  748. 


Diagrams  illustrating  development  of  arteries  of  lower  limb;  s,  sciatic  :  rf.  digital  ;  /,  femoral ; 
saph,  saphenous  ;  pop,  popliteal ;  per,  peroneal ;  pt,  at,  posterior  and  anterior  tibial. 


cle  and  anastomoses  with  the  sciatic  artery  just  above  the  upper  end  of  the  popliteal  space  ( C), 
whereupon  the  portion  of  the  sciatic  artery  immediately  above  tne  anastomosis  degenerates  and 

54 


85o  HUMAN    ANATOMY. 

the  vessel  becomes  reduced  to  the  slender  a.  comes  nervi  ischiadici  of  the  adult.  Its  lower  por- 
tions, which  become  the  popliteal  and  peroneal  arteries,  now  seem  to  be  the  continuation  of  the 
femoral  {i.e.,  the  saphenous). 

From  the  lower  part  of  the  popliteal  a  branch  arises  which  anastomoses  with  the  saphenous 
and,  together  with  the  lower  part  of  that  artery,  forms  the  posterior  tibial,  the  upper  part  of  the 
saphenous  then  disappearing  except  in  so  far  as  it  is  represented  by  one  of  the  branches  of  the 
anastomotica  magna.  The  anterior  tibial  is  a  late  formation  resulting  from  the  fusion  of  an  upper 
and  lower  branch  from  the  peroneal  which  perforate  the  interosseous  membrane  (  C),  the  con- 
nection of  the  lower  branch  with  the  peroneal  degenerating  after  the  anastomosis,  except  in  so 
far  as  it  persists  as  the  anterior  peroneal  artery  (/?). 

THE  VEINS. 

The  veins  are  those  vessels  which  receive  the  blood  from  the  capillary  net-work 
and  return  it  to  the  heart. 

Compared  with  the  arteries,  they  present  many  differences,  both  of  structure 
(page  677)  and  arrangement.  Their  walls  are  much  thinner,  so  that  the  color  of 
the  blood  which  they  contain  shows  through,  and  they  are  readily  compressible  to  the 
extent  of  a  complete  obliteration  of  their  lumen  and  are  also  exceedingly  dilatable. 
Notwithstanding  their  thinness,  they  are  less  easily  ruptured  by  over-distention  than 
are  the  arteries  and  are  capable  of  undergoing  a  remarkable  elongation,  those  of  an 
adult  withstanding  an  extension  to  at  least  50  per  cent,  more  than  their  original  length 
without  losing  their  elasticity — a  property  which  explains  the  more  direct  course 
taken  by  the  veins  as  compared  with  the  arteries  in  mobile  portions  of  the  body  {e.g. , 
the  facial  vein  as  compared  with  the  artery).  Indeed,  it  seems  that  the  veins  when 
in  place  in  the  body  are  always  stretched  to  a  considerable  extent,  the  cephalic  vein, 
for  example,  contracting  when  removed  from  the  body  to  40  per  cent,  of  its  length 
in  the  extended  arm  (Bardeleben). 

The  most  striking  structural  peculiarity  of  the  veins,  however,  is  the  occurrence 
in  them  of  semilunar  valves,  arranged  usually  in  pairs,  with  their  cavities  directed 
towards  the  heart.  These  valves  resemble  in  their  general  form  the  semilunar  valves 
of  the  systemic  and  pulmonary  aortse,  and,  as  in  those  vessels,  the  veins  are  somewhat 
enlarged  immediately  above  the  attachment  of  each  pair,  so  that  the  blood  may 
readily  flow  behind  the  valves,  force  their  free  margins  together  and  so  occlude 
the  vessel.  These  valves  play  an  important  part  in  directing  the  flow  of  blood  in 
the  veins  towards  the  heart,  since,  in  the  event  of  any  pressure,  such  as  that  exerted 
by  a  contracting  muscle,  acting  on  the  vein,  they  will  prevent  a  backward  flow  of 
blood  towards  the  capillaries.  Valves  do  not  occur  in  veins  of  less  than  1  mm.  in 
diameter  and  are  also  lacking  in  many  of  the  larger  trunks,  such  as  the  superior  and 
inferior  venae  cavse,  the  pulmonary  and  the  portal  veins.  In  general  they  are  more 
numerous  in  the  veins  of  the  limbs  than  in  those  of  the  trunk  and  in  the  deep  than  in 
the  superficial  vessels. 

Their  number  in  any  vessel  in  which  they  normally  occur  is  subject  to  con- 
siderable variation  in  different  individuals  and  even  on  opposite  sides  of  the  body  in 
the  same  subject.  It  seems  probable  that  this  variation  is  brought  about  by  a 
degeneration  of  a  greater  or  less  number  of  the  pairs  originally  present,  since  in  the 
majority  of  the  veins  the  number  of  valves  diminishes  with  age  (Bardeleben),  and 
even  in  adult  bodies  evidence  of  degeneration  may  be  seen  in  the  insufficiency  of 
some  of  the  valves  or  even  in  their  perforation.  It  is  possible,  therefore,  that  the 
arrangement  of  the  valves  in  the  adult  is  a  secondary  condition,  derived  from  one  in 
which  the  valves  were  much  more  numerous  and  were  situated  at  regular  intervals 
along  the  vessels.  In  favor  of  this  view  it  has  been  found  (Bardeleben)  that  in  certain 
veins  the  valves  in  the  adult  are  separated  by  intervals  either  of  a  definite  length  or  of 
a  multiple  of  this,  the  length  of  the  intervals  standing  in  relation  to  the  length  of  the 
part  or,  in  general,  to  the  height  of  the  individua1  m  which  the  vein  occurs.  Thus,  in 
a  man  measuring  160  mm.  in  height,  the  valves  of  the  right  long  saphenous  vein  were 
separated  by  intervals  which  were  all  approximately  multiples  of  6. 85  mm.  in  length, 
while  the  intervals  separating  the  valves  of  the  right  cephalic  vein  were  approximately 
multiples  of  5.2  mm. ;  and  in  a  male  child  81  cm.  in  height,  the  valves  of  the  right 
long  saphenous  vein  were  separated  by  intervals  of  3  mm.  or  some  multiple  of  this. 


THE    VEINS.  851 

A  more  readily  appreciable  relation  of  the  valves  is  that  which  they  bear  to  the 
branches  which  open  into  the  vein,  a  pair  of  valves  being  found  immediately  distal  to 
the  entrance  of  each  collateral  vein  ;  and,  furthermore,  a  pair,  or  at  least  a  single  valve, 
very  generally  occurs  at  the  termination  of  a  vein,  where  it  enters  either  a  larger 
stem  or  the  heart.  These  terminal  valves  are  present  in  certain  veins  which  other- 
wise are  quite  destitute  of  valves,  as,  for  instance,  in  the  internal  jugular,  the  internal 
maxillary,  and  the  vertebral  veins. 

It  has  already  been  noted  that  valves  are  entirely  wanting  in  certain  veins.  Among  these 
are  the  sinuses  of  the  cranium,  the  cerebral,  ophthalmic,  periosteal,  pulmonary,  bronchial, 
portal,  renal,  uterine,  ovarian,  and  innominate  (brachio-cephalic)  veins,  and  the  superior  and 
inferior  venae  cavae.  Furthermore,  they  are  usually  absent  in  the  common  and  internal  iliacs 
and  in  the  facial  veins,  although  occasionally  they  occur  in  all  three. 

In  their  position  and  arrangement  also  the  veins  differ  noticeably  from  the 
arteries.  While  veins  are  usually  to  be  found  accompanying  the  arteries,  enclosed  with 
them  in  a  common  fibrous  sheath,  additional  veins  of  considerable  size  are  abundant 
immediately  beneath  the  skin — a  condition  which  is  almost  entirely  foreign  to  the 
arteries.  Furthermore,  although  in  a  general  way  a  vein  may  pursue  the  same 
course  as  an  artery,  it  may  lie  at  some  little  distance  from  the  latter  and  fail  to  follow 
its  course  exactly.  This  is  true,  for  instance,  of  the  facial  and  the  lingual  veins 
and  also  of  the  subclavian  vein,  which  is  separated  from  the  corresponding  artery  by 
the  scalenus  anticus  muscle  ;  this  likewise  applies  to  the  veins  at  the  root  of  the  neck 
which  accompany  in  a  general  way  the  branches  of  the  subclavian  artery,  but  open  into 
the  innominate  vein  instead  of  the  subclavian.  In  many  cases  the  veins  which  accom- 
pany arteries  are  double,  one  lying  on  either  side  of  the  artery  and  forming  what  are 
generically  known  as  venae  comites  (venae  comitantes  ).  The  causes  which  determine 
this  double  condition  are  obscure.  The  arrangement  is  not  found  in  the  larger 
venous  trunks,  occurring,  for  instance,  in  the  leg  only  below  the  knee  and  in  the 
arm  only  as  far  up  as  the  middle  of  the  brachium  ;  size  alone,  however,  does  not 
seem  to  be  the  determining  factor,  since  the  internal  mammary  and  epigastric  veins 
are  double,  while  the  intercostal  and  lumbar  veins,  almost  of  the  same  size  as  the 
former,  are  single.  Nor  does  the  quality  of  the  tissue  in  which  the  veins  occur 
determine  their  duplication,  for  those  which  are  embedded  within  the  muscles  of  the 
tongue  are  doubled,  while  those  within  the  heart  musculature  are  single  ;  again, 
while,  as  a  rule,  the  veins  which  occur  in  fibrous  tissue — as,  for  instance,  the  menin- 
geal veins — are  double,  yet  those  of  the  skin  are  single.  Finally,  it  may  be  noted 
that  there  are  exceptions  to  the  rule  that  the  veins  which  occur  in  the  cavities  of  the 
body  are  single,  since  a  duplication  is  found  in  the  spermatic  veins  and  also  in  those 
of  the  gall-bladder. 

Not  only  doubling  of  many  of  the  veins  occurs,  but  a  prevailing  tendency  exists 
towards  extensive  anastomoses  far  surpassing  that  displayed  by  any  of  the  arteries. 
Even  in  the  cases  of  the  larger  proximal  trunks  communications  exist,  those  between 
the  pulmonary  and  bronchial  veins  and  that  between  the  superior  and  inferior  venae 
cava?  by  way  of  the  azygos  being  examples.  In  the  smaller  vessels  the  anastomoses 
are  often  so  numerous  as  to  result  in  the  formation  of  plexuses.  Venae  comites  are 
united  by  frequent  cross-connections,  sometimes  so  numerous  as  to  present  the  ap- 
pearance of  a  plexus  surrounding  the  artery.  Complicated  venous  plexuses  also 
accompany  the  various  ducts  of  the  body,  as,  for  example,  the  parotid  ducts,  the 
ureters,  and  the  vasa  deferentia.  In  addition,  extensive  venous  plexuses  occur  in 
various  regions  of  the  body,  as  in  the  neighborhood  of  its  orifices,  in  the  terminal 
phalanges  of  the  fingers  and  toes,  in  the  diploe  of  the  skull,  in  the  spinal  canal,  in 
the  pelvis,  and  in  connection  with  the  genito-urinary  organs.  Since  the  larger 
trunks  usually  arise  at  several  points  both  from  these  and  from  the  wider-meshed 
plexuses  occurring  elsewhere,  opportunity  is  thus  afforded  for  the  return  of  the 
blood  to  the  heart  by  different  paths — an  arrangement  explaining  the  frequent  ineffi- 
ciency of  a  ligation  of  even  large  trunks  to  prevent  venous  hemorrhage. 

Special  mention  should  be  made  of  one  set  of  the  venous  channels — namely, 
the  simises  of  the  dui-a  mater — which  establish  communication  between  the  cerebral 
and  ophthalmic  veins  and  the  internal  jugular.      They  are  channels  contained  within 


852  HUMAN    ANATOMY. 

the  dura  mater,  lined  by  an  endothelium  similar  to  and  continuous  with  that  of  the 
extracranial  veins,  but  lack  any  extensive  development  of  elastic  fibres  in  their 
walls,  which  are  formed  by  the  dura.  They  possess  no  valves,  although  in  certain 
of  them,  as  in  the  superior  longitudinal  and  cavernous  sinuses,  the  lumen  is 
traversed  by  irregular  trabecular  of  fibrous  tissue.  These  are  especially  well 
developed  and  almost  tendinous  in  character  in  the  superior  longitudinal  sinus, 
while  in  the  cavernous  sinus  they  are  softer,  and  from  them  and  from  the  walls  of  the 
sinus  fringe-like  prolongations,  .5-2  mm.  in  length,  project  freely  into  the  lumen. 
Connected  with  certain  of  these  sinuses  and  developed  from  certain  of  the  smaller 
veins  which  open  into  them  are  so-called  blood-lakes  ( lacunae) — cavities  or  plexuses 
in  the  dura  mater,  lined  with  endothelium,  and  connecting  either  directly  or  by  means 
of  a  short  canal  with  an  adjacent  sinus.  They  are  usually  situated  more  or  less  sym- 
metrically with  reference  to  the  sinus  with  which  they  are  connected,  and  some  are 
very  constant  in  occurrence.  Thus,  a  certain  number  usually  occur  on  either  side 
of  the  superior  longitudinal  sinus  (page  1199),  others  in  the  tentorium  cerebelli  con- 
necting with  the  lateral  sinus,  others  in  the  middle  fossa  of  the  skull  along  the  course 
of  the  meningeal  veins,  and  others  in  the  vicinity  of  the  straight  sinus.  They  occasion- 
ally reach  a  considerable  size,  bulging  outward  the  dura  which  encloses  them  and 
excavating  by  absorption  irregular  depressions  upon  the  inner  surface  of  the  skull. 
Occasionally  this  absorption  of  the  cranial  bones  proceeds  so  far  that  bulging  of  the 
outer  table  of  the  skull  over  a  lake  takes  place,  and,  in  the  case  of  those  occurring 
along  the  course  of  the  superior  longitudinal  sinus,  Pacchionian  bodies  developed  from 
the  subjacent  arachnoid  tissue  may  invade  them,  pushing  before  them  the  attenuated 
floors  of  the  lakes. 

Classification  of  the  Veins. — Theoretically  a  description  of  the  veins  should 
start  with  the  peripheral  vessels  and  proceed  towards  the  great  trunks,  following  the 
course  of  the  blood.  Such  a  method  would  prove,  however,  somewhat  confusing, 
largely  on  account  of  the  numerous  anastomoses  that  occur  ;  it  is  preferable,  therefore, 
to  base  a  classification  primarily  upon  the  great  trunks  and  to  consider  their  afferents 
topographically,  according  to  the  areas  which  they  drain. 

From  the  embryological  stand-point,  there  are  primarily  four  great  systems  of  . 
veins  :  (1)  the  cardinal  system,  represented  by  the  vena  cava  superior  and  its  tributa- 
ries ;  (2)  the  inferior  cava/  system;  (3)  the  portal  system  ;  and  (4)  the  pulmonary 
system.  Owing  to  subsequent  changes,  it  is  necessary  to  recognize  in  the  cardinal 
system  three  sub-systems  :  (1)  that  of  the  cardiac  veins  ;  (2)  that  of  the  superior 
vena  cava  and  its  tributaries,  except  (3)  the  azygos  veins.  In  all,  then,  six  great 
systems  of  veins  may  be  recognized  in  the  adult.      The)'  are  as  follows  : 

1.  The  pulmonary  system. 

2.  The  cardiac  system.  } 

3.  The  superior  caval  system.    >-  The  cardinal  system. 

4.  The  azygos  system.  ) 

5.  The  inferior  caval  system. 

6.  The  portal  system. 

In  the  descriptions  which  follow  the  veins  are  considered  on  the  basis  of  this 
classification. 

THE    PULMONARY    SYSTEM. 

The  Pulmonary  Veins. 

The  pulmonary  veins  (venae  pulmonales)  (Figs.  749,  750)  are  four  in  number, 
two  passing  from  the  hilum  of  each  lung  to  the  posterior  surface  of  the  left  auricle  of 
the  heart.  Each  vein  is  formed  at  the  hilum  of  its  lung  by  the  union  of  a  number 
of  smaller  vessels  which  take  origin  ultimately  from  the  capillary  net-work  formed  by 
the  branches  of  the  pulmonary  artery  and  to  a  certain  extent  from  that  formed  by  the 
bronchial  arteries.  The  arrangement  of  the  afferent  branches  in  the  substance  of  the 
lungs  is  described  in  connection  with  the  anatomy  of  these  organs  (page  1854),  and  it 
will  be  sufficient  to  note  here  that  they  correspond  in  number  to  the  branches  of  the 
pulmonary  artery  and  of  the  bronchi,  and  pursue  a  course  more  or  less  independent 
of  these,  which  lie  side  by  side.  Converging  and  uniting  as  they  pass  towards  the 
hilum,  the  branches  from  the  superior  lobe  of  each  lung  unite  to  form  the  superior 


THE    PULMONARY    VEINS. 


S53 


pulmonary  vein  of  that  side,  those  from  the  inferior  lobe  unite  to  form  the  in- 
ferior pulmonary  vein,  while  those  from  the  middle  lobe  of  the  right  lung  unite 
to  form  a  single  trunk  which  usually  opens  into  the  right  superior  vein,  although  it 
occasionally  opens  independently  into  the  left  auricle,  forming  what  is  then  termed 
the  middle  pulmonary  vein. 

Each  of  the  four  pulmonary  veins  has  a  length  of  about  15  mm.,  and  for  about 
line-third  of  its  course  is  partially  invested  by  the  visceral  layer  of  the  pericardium 
(page  715).  The  right  superior  vein  is  usually  slightly  the  largest  of  the  four,  while 
the  left  superior  is  the  smallest,  the  right  and  left  inferior  veins  being  about  the  same 
size.  No  valves  occur  either  throughout  the  course  or  at  the  orifices  of  the  pulmonary 
veins. 

Relations. — The  superior  pulmonary  veins  have  a  course  which  is  obliquely 
downward  and  inward.  In  their  extrapericardial  portion  they  lie  anterior  to  and 
below  the  pulmonary  arteries,   and  are  separated   by  them  from  the  bronchi;   the 

Fig.  749. 


Left  pulmonary  arterj 


appendage       / / / 
Aorta,  systemic  ' / / 
Left  coronary  artery     / 
Right  coronary  vessels  Ri<rht 

marginal 


Injected  heart  and  great  vessels,  viewed  from  before  ;  parts  of  superior  vena  cava  and  aorta 
have  been  removed  to  show  right  pulmonary  artery. 

vein  of  the  right  side  is  crossed  from  above  downward  by  the  phrenic  nerve  and  by 
the  vena  cava  superior.  In  its  intrapericardial  portion  the  right  superior  vein  lies 
behind  the  terminal  portion  of  the  superior  vena  cava  and  the  left  one  behind  the 
pulmonary  aorta  (pulmonary  artery),  while  posteriorly  each  is  in  relation  with  its 
corresponding  inferior  vein. 

The  inferior  veins  are  more  horizontal  in  position,  but  are  directed  forward 
as  well  as  inward.  They  lie  in  a  plane  considerably  posterior  to  that  of  the 
corresponding  superior  veins  and  are  situated  internally  to  and  behind  an  anterior 
descending  branch  of  each  bronchus. 

Anastomoses. — In  addition  to  serving  for  the  return  flow  of  the  blood  carried 
to  the  lungs  by  the  pulmonary  arteries,  the  pulmonary  veins  also  receive  a  certain 
amount  of  the  blood  carried  by  the  bronchial  arteries.      Communications  between 


854  HUMAN    ANATOMY. 

the  bronchial  and  pulmonary  veins  in  the  region  of  the  smaller  bronchi  are  abundant, 
and,  in  addition,  the  main  stems  of  the  pulmonary  veins  receive  at  the  hilum  of  the 
lung  one  or  more  branches  from  the  larger  bronchial  veins.  They  also  receive  com- 
munications from  the  venous  plexus  which  surrounds  the  thoracic  aorta  in  the  pos- 
terior mediastinum,  and  occasionally  also  a  vein  from  the  pericardium.  There  is 
thus  a  certain  commingling  of  venous  blood  with  the  arterialized  blood  which  forms 
the  principal  contents  of  the  pulmonary  veins. 

Variations. — At  one  stage  in  the  development  of  the  embryo  the  veins  from  each  lung 
converge  to  a  single  short  trunk  before  opening  into  the  portion  of  the  atrium  which  corresponds 
to  the  left  auricle.  As  the  development  of  the  heart  proceeds,  this  trunk  is  gradually  taken  up 
into  the  auricle,  until  the  two  stems  which  unite  to  form  it  open  independently  into  that 
structure.  An  inhibition  of  this  process  occasionally  obtains,  so  that  but  a  single  vein,  repre- 
senting the  original  terminal  trunk,  opens  into  the  auricle  from  one  lung  or  from  both.  On  the 
other  hand,  the  taking  up  of  the  pulmonary  vein  into  the  wall  of  the  auricle  may  proceed  further 
than  usual,  or,  to  state  it  perhaps  more  correctly,  the  union  of  the  various  stems  emerging  from 
the  hilum  of  the  lung  may  be  partly  delayed  until  they  have  reached  the  original  terminal  trunk, 
so  that  when  this  is  taken  up  into  the  auricle  an  additional  vein  will  open  independently  into  the 
latter.  This  extra  vein  is  most  frequently  that  from  the  middle  lobe  of  the  right  lung,  but  three 
distinct  veins  have  also  been  observed  upon  the  left  side. 

THE    CARDINAL    SYSTEM. 

The  cardinal  system  of  veins  is  so  named  because  its  main  trunks  are  the  repre- 
sentatives of  the  cardinal  veins  of  the  embryo.  These  veins  are  four  in  number, 
disposed  symmetrically  in  pairs,  two  returning  the  blood  from  the  head,  neck,  and 
upper  extremities,  while  the  other  two  return  that  from  the  thoracic  and  abdominal 
walls,  from  the  thoracic  viscera,  and  from  the  lower  extremities.  Just  before  they 
reach  the  heart,  the  superior  and  i?iferior  or  posterior  cardinal  veins  of  each  side 
unite  (Fig.  776)  to  form  trunks  known  as  the  ducts  of  Givier,  the  two  ducts  opening 
independently  into  the  primitive  right  auricle.  By  a  series  of  changes,  which  are 
described  more  fully  in  the  section  on  the  development  of  the  veins  (page  927),  the 
left  superior  cardinal  becomes  connected  with  the  right  at  the  base  of  the  neck,  the  stem 
so  formed  constituting  what  is  termed  the  superior  vena  cava.  The  portion  of  the 
left  superior  cardinal  between  the  connecting  vessel  and  the  heart  becomes  greatly 
reduced  in  size,  indeed,  almost  completely  degenerates ;  the  left  duct  of  Cuvier, 
however,  persisting  as  the  coronary  sinus,  which  receives  the  coronary  veins  returning 
the  blood  from  the  heart's  walls.  On  the  development  of  the  vena  cava  inferior  the 
veins  of  the  lower  extremity  make  connection  with  it,  separating  from  the  inferior 
cardinals ;  these  latter  become  considerably  reduced  in  size,  especially  in  the  abdominal 
region,  a  cross-connection  develops  between  the  left  and  right  veins,  and  the  former 
severs  its  connection  with  the  left  ductus  Cuvieri,  the  final  result  being  the  formation 
of  the  venae  azygos  and  hemi-azygos  of  the  adult. 

There  are,  then,  developed  from  the  cardinal  veins  of  the  embryo  three  sub- 
systems of  veins  :  (1)  that  of  the  cardiac  veins  ;  (2)  that  of  the  superior  vena  cava, 
which  includes  the  jugular  and  subclavian  groups  of  veins,  the  original  superior 
cardinals  being  represented  by  the  internal  jugular  veins  ;  and  (3)  the  azygos  sub- 
system.     These  will  be  considered  in  the  order  in  which  they  have  been  named. 

THE   CARDIAC    VEINS. 
The  Coronary  Sinus. 

The  coronary  sinus  (sinus  coronarius)  (Fig.  750)  is  a  short  venous  trunk  about 
3  cm.  (a  little  over  an  inch)  in  length,  which  occupies  the  right  half  of  that  portion  of  the 
posterior  auriculo-ventricular  groove  which  lies  between  the  left  auricle  and  ventricle. 
At  its  right  end  it  opens  into  the  right  auricle,  its  orifice  (Fig.  657)  being  situated 
upon  the  posterior  surface  of  the  auricle,  below  that  of  the  inferior  vena  cava,  and  being 
guarded  by  the  Thebesian  valve  (valvula  sinus  coronarii).  At  its  left  end  it  receives  the 
great  coronary  vein,  from  whose  proximal  portion  it  is  not  always  clearly  distinguish- 
able upon  superficial  examination.  A  close  inspection  usually  reveals,  however, 
either  a  constriction  or  a  slight  dilatation  at  the  union  of  the  two  vessels,  and  on 


THE    CARDIAC    VEINS. 


855 


laying  them  open  a  distinct  valve,  of  either  one  or  two  cusps,  but  usually  insuffi- 
cient, will  be  found  at  their  line  of  junction.  This  valve  is  known  as  the  valve  of 
Vieussens.  Furthermore,  the  walls  of  the  sinus  differ  from  those  of  the  vein  in  pos- 
sessing a  complete  layer  of  muscular  fibres,  both  oblique  and  circular,  continuous 
with  the  musculature  of  the  auricle. 

In  addition  to  the  great  coronary  vein,  the  coronary  sinus  also  receives  the 
posterior  vein  of  the  left  ventricle  and  the  middle  cardiac  vein,  which  open  into  it 
from  below,  and  the  oblique  vein  of  the  left  auricle,  which  passes  to  it  from  above. 

Variations. — The  coronary  sinus,  as  already  stated,  represents  the  left  ductus  Cuvieri  of 
the  embryo.  It  varies  somewhat  in  length,  reaching  in  extreme  cases  a  length  of  5.4  cm.  It  has 
been  observed  to  be  obliterated  at  its  entrance  into  the  right  auricle,  the  great  coronary  vein 
then  opening  into  the  left  innominate  (brachio-cephalic)  vein,  and,  in  addition  to  the  veins 
already  noted  as  emptying  into  it,  it  frequently  receives  the  marginal  vein  of  the  left  ventricle. 


i.  The  Left  Coronary  Vein. — The  great  cardiac  or  left  coronary  vein  (v.  cor- 
dis magna)  (Fig.  749)  begins  upon  the  anterior  surface  of  the  heart  at  the  apex, 
where  it  anastomoses  with  the  veins  of  the  posterior  surface,  and  ascends  the  anterior 

Fig.  750. 


Left  pulmonary  artery 


Superior  left  pulmonary  \ 
Inferior  left  pulmonary  1 


Transverse  branch  of 
left  coronary  artery 


Left  ventricle 


-Superior  right  pulmonary  ■ 
Right  pulmonary  artery 


ght  pulmonary  a 


Inferior  vena  cava 


Coronary  sinus 

Right  coronary  vein 
Transverse  branch  of  right 

coronary  artery 

Posterior  descending  branch 

of  right  coronary  artery 


-  Middle  cardiac  1 


Right  • 


Posterior-inferior  aspect  of  injected  heart,  showing  blood-vessels. 

interventricular  groove  in  company  with  the  left  coronary  artery,  to  the  anterior 
auriculo-ventricular  groove,  in  which  it  passes  to  the  left  and,  curving  around  the  left 
border  of  the  heart  to  the  posterior  surface,  terminates  by  opening  into  the  left  end 
of  the  coronary  sinus. 

In  the  vertical  portion  of  its  course  it  receives  veins  from  the  anterior  surface  of 
both  ventricles,  and  in  its  course  in  the  auriculo-ventricular  groove,  throughout  which  it 
is  embedded  in  the  fat  which  usually  occupies  the  groove,  it  receives  a  number  of  small 
veins  from  the  surfaces  of  both  the  left  auricle  and  ventricle.  Among  those  from  the 
ventricle  there  is  especially  to  be  mentioned,  as  larger  and  more  constant  than  the 
rest,  the  vena  marginalis  sinistra,  which  ascends  along  the  left  border  of  the  heart 
and  empties  into  the  great  coronary  vein  shortly  before  its  opening  into  the  sinus. 


856  HUMAN    ANATOMY. 

2.  The  Posterior  Cardiac  Vein. — The  posterior  cardiac  vein  (v.  posterior 
ventriculi  sinistrij  ascends  along  the  posterior  surface  of  the  left  ventricle,  lying  about 
midway  between  the  left  border  of  the  heart  and  the  posterior  interventricular  groove 
and  receiving  collateral  branches  from  the  walls  of  the  ventricle.  It  opens  above 
into  the  coronary  sinus  near  the  point  of  entrance  of  the  great  coronary  vein  and 
occasionally  unites  with  that  vessel. 

3.  The  Middle  Cardiac  Vein. — The  middle  cardiac  vein  (v.  cordis  media; 
(Fig.  750;  occupies  the  posterior  interventricular  groove,  accompanying  the  right 
coronary  artery.  It  arises  in  the  vicinity  of  the  apex  of  the  heart  and  ascends, 
receiving  collateral  branches  from  the  posterior  surfaces  of  both  ventricles,  to  open 
into  the  coronary  sinus  near  its  termination.  This,  next  to  the  great  coronary  vein,  is 
the  largest  vein  of  the  heart,  and  occasionally  opens  independently  into  the  right 
auricle  close  to  the  entrance  of  the  coronary  sinus. 

4.  The  Right  Coronary  Vein. — The  small  cardiac  or  right  coronary  vein 
(v.  cordis  parva)  (Fig.  750)  occupies,  when  present,  the  right  half  of  the  posterior 
auriculo-ventricular  groove  and  opens  into  the  coronary  sinus  just  before  its  termi- 
nation. Occasionally  it  opens  into  the  middle  cardiac  vein,  or  directly  into  the 
right  auricle,  and  is  not  infrequently  lacking  as  a  distinct  vessel,  the  tributaries 
which  empty  into  it  from  the  posterior  surface  of  the  right  auricle  and  the  upper 
part  of  the  posterior  surface  of  the  right  ventricle  then  opening  directiy  into  the 
auricle.  One  of  the  largest  and  most  constant  of  these  tributaries  ascends  along- 
the  right  border  of  the  right  ventricle  and  is  termed  the  right  marginal  vein  or 
vein  of  Galen. 

5.  The  Oblique  Vein  of  the  Left  Auricle. — The  oblique  vein  of  the  left 
auricle  (v.  obliqua  atrii  sinistri),  also  known  as  Marshall '  s  vein,  is  a  small  vein  of 
variable  development  which  descends  obliquely  over  the  posterior  surface  of  the  left 
auricle  and  opens  below  into  the  coronary  sinus.  Above,  it  is  continuous  with  a 
fibrous  cord  contained  within  the  vestigial  fold  of  the  pericardium  (page  716),  the 
cord  and  vein  together  representing  the  lower  part  of  an  original  left  superior  vena 
cava.  The  degree  of  development  of  the  vein  varies  greatly,  and  occasionally  the 
fibrous  cord  retains  its  original  lumen,  so  that  a  more  or  less  developed  left  superior 
vena  cava  is  really  present.  This  anomaly  may,  however,  be  more  convenientlv 
considered  in  connection  with  those  of  the  superior  caval  system  of  veins  (page  859). 

In  addition  to  these  principal  veins  of  the  heart  there  is  a  varying  number  of 
others  which  open  directly  into  the  right  auricle  and  are  situated  upon  the  anterior 
surface  of  the  right  ventricle,  whence  they  have  been  termed  the  anterior  cardiac 
veins  (vv.  cordis  anteriores).  They  are  all  comparatively  short  vessels  and  usually 
accompany  descending  branches  of  the  right  coronary  artery.  Owing  to  the  fre- 
quency with  which  it  opens  directly  into  the  auricle,  the  vein  of  Galen  is  usually 
regarded  as  one  of  this  group  of  veins. 

Finally,  the  Thebesian  veins  (vv.  cordis  minimae)  form  part  of  the  cardiac 
venous  system.  These  are  minute  veins,  imbedded  in  the  substance  of  the  heart 
walls,  and  communicating  with  the  heart  cavities  by  means  of  the  Thebesian  foramina 
(page  716),  which  occur  most  abundantly  upon  the  walls  of  the  right  auricle,  though 
also  upon  those  of  the  left  auricle,  and,  less  abundantly,  upon  those  of  the  ventricles. 
At  their  other  ends  these  veins  communicate  in  the  heart' s  substance  with  the  radicles 
of  the  other  cardiac  veins,  and,  in  cases  of  stenosis  of  the  coronary  arteries,  may 
consequently  contribute  to  some  extent  to  the  nutrition  of  the  heart  musculature, 
carrying  blood  to  it  directly  from  the  heart  cavities. 

Valves  of  the  Cardiac  Veins. — The  Thebesian  valve,  which  guards  the  right 
auricle,_  may  be  considered  as  the  ostial  valve  of  that  vessel,  which  throughout  its 
course  is  destitute  of  valves.  So,  too,  throughout  the  extent  of  the  cardiac  veins 
valves  are  entirely  lacking,  but  certain  of  those  which  open  into  the  coronary  sinus 
are  provided  with  ostial  valves.  That  of  the  great  coronary  vein  is  the  valve  of 
Vieussens,  and  others  are  usually  present  at  the  mouths  of  the  middle  vein  and  the 
posterior  vein  of  the  left  ventricle,  and  less  constantly  at  the  mouths  of  the  marginal 
and  the  small  coronary  veins.  These  valves  may  be  either  single  or  paired  and  are 
frequently  insufficient.  No  valves  are  present  either  throughout  the  course  or  at  the 
orifice  of  the  oblique  vein  of  the  left  auricle. 


THE    SUPERIOR    CAVAL    SYSTEM. 


857 


Variations. — The  principal  variations  which  occur  in  connection  with  the  cardiac  veins  have 
been  noted  in  the  description  of  the  vessels,  and  it  need  only  be  added  that  the  oblique  vein  of 
the  left  auricle  is  not  infrequently  entirely  lacking,  except  in  so  far  as  it  is  represented  by  a 
fibrous  cord,  that  absence  of  the  great  coronary  vein  has  been  observed,  and  that  the  middle 
vein  occasionally  opens  directly  into  the  right  auricle. 


THE   SUPERIOR   CAVAL   SYSTEM. 

The  Vena  Cava  Superior. 

The  superior  or  descending  vena  cava  (Figs.  749,  751)  is  the  main  venous  trunk 
which  delivers  to  the  heart  the  blood  returning  from  the  head,  neck,  upper  limbs,  and 
thorax.  It  measures  7-8  cm.  (3  in.)  in  length,  and  has  a  diameter  at  its  termination 
of  about  2.  2  cm.  (a  little  less  than  1  in.  ).  It  is  situated  throughout  its  entire  course  in 
the  thoracic  cavity,   lying  in  the  superior  mediastinum,  and  is  formed  immediately 


Fig.  751 


Anterior  juyul. 

Transverse  cervical 

Clavicle. 

Suprascapular  vei 


Diaphragm,  thora 


Dissection  she. 


lun^s  have  bee 


below  the  lower  border  of  the  first  costal  cartilage  of  the  right  side  by  the  union  of  the 
right  and  left  innominate  (brachio-cephalic)  veins.  Its  course  is  downward  and 
slightly  backward,  with  a  curvature  corresponding  to  the  first  portion  of  the  arch  of 
the  aorta,  with  which  it  is  in  relation.  Below,  it  opens  into  the  upper  posterior  portion 
of  the  right  auricle  on  a  level  with  the  third  costal  cartilage  of  the  right  side. 

Relations. — The  lower  portion  of  the  superior  vena  cava  is  invested  by  the  peri- 
cardium to  an  extent  varying  from  a  few  to  40  mm.,  on  an  average,  perhaps  to  about 
one-third   its  length.      The  upper  extrapericardial  portion   is  in  relation   anteriorly 


S58  HUMAN   ANATOMY. 

with  the  thymus  gland  or  the  fatty  tissue  which  replaces  it,  and  is  overlapped  by 
the  right  pleura  and  lung.  Behind,  it  crosses  the  origin  of  the  right  bronchus  and 
the  structures  at  the  root  of  the  right  lung,  from  which  it  is  separated  by  numerous 
lymphatic  nodes  ;  to  the  light  it  is  in  contact  with  the  pleura  covering  the  inner  surface 
of  the  right  lung  and  with  the  right  phrenic  nerve  ;  and  to  the  left  it  lies  alongside  the 
ascending  portion  of  the  aortic  arch. 

In  its  lower  intrapericardial  portion  it  has  to  the  left  the  systemic  aorta:  anteriorly, 
the  right  auricle;  posteriorly,  the  right  pulmonary  artery,  the  right  superior  pul- 
monary vein,  and  the  right  bronchus,  while  upon  the  right  it  is  free. 

The  vena  cava  superior  contains  no  valves. 

Tributaries. — In  addition  to  the  right  and  left  innominate  veins,  by  the  union 
of  which  it  is  formed,  the  vena  cava  superior  receives  the  vena  azygos  major  and 
small  veins  from  the  mediastinum  and  pericardium. 

Variations. — Cases  have  been  recorded  in  which  the  vena  cava  superior  received  the  right 
internal  mammary  or  the  right  superior  intercostal  vein  which  normally  open  into  the  right 
innominate  vein.  It  may  also  receive  the  vena  thyreoidea  ima,  a  vein  only  occasionally  present 
and  draining  the  territory  supplied  by  the  art.  thyreoidea  ima. 

A  more  remarkable  and  rarer  variation  is  the  union  with  the  superior  vena  cava  of  a  com- 
paratively large  vein  which  issues  from  the  right  lung.  A  similar  condition  has  been  observed 
in  connection  with  the  innominate  veins,  and  its  probable  significance  will  be  considered  in 
connection  with  the  variations  of  those  vessels. 

Practical  Considerations. — The  superior  vena  cava  would  be  involved  in  a 
stab-wound  passing  through  either  the  first  or  the  second  intercostal  space  on  the 
right  side,  close  to  the  sternum.  The  vessel  is  subject  to  compression  in  aneurism 
of  the  ascending  aorta  (q.v.),  producing  venous  congestion  in  the  veins  of  the  neck 
and  of  the  upper  extremities. 

The  Innominate  Veins. 

The  innominate  or  brachio-cephalic  veins  (vv.  anonymae)  (Fig.  751)  are  two  in 
number,  a  right  and  a  left.  They  are  situated  in  the  upper  portion  of  the  thoracic 
cavity,  being  formed  by  the  union  of  the  internal  jugular  and  subclavian  veins,  and 
terminate  by  uniting  opposite  the  first  costal  cartilage  of  the  right  side  to  form  the 
vena  cava  superior.  The  union  of  the  internal  jugular  and  subclavian  vein  takes 
place  on  each  side  opposite  the  sternal  end  of  the  clavicle  ;  but,  since  the  vena  cava 
superior  lies  entirely  to  the  right  of  the  median  line  of  the  body,  the  left  innominate 
vein  has  a  much  greater  distance  to  traverse  in'  order  to  reach  its  point  of  termination 
than  has  the  right  one,  and  consequently  it  will  be  necessary  to  describe  each  vein 
separately. 

The  right  innominate  vein  has  a  length  of  2-4  cm.  (%-i%  in.)  and  an 
almost  vertical  course,  opening  directly  downward  into  the  vena  cava  superior.  It 
lies  behind  the  inner  end  of  the  right  clavicle,  from  which  it  is  separated  by  the  lower 
portions  of  the  sterno-hyoid  and  sterno-thyroid  muscles,  and  a  little  lower  it  is  behind 
the  first  right  costal  cartilage.  To  the  right  it  is  in  relation  with  the  inner  surface 
of  the  right  pleura  and  with  the  right  phrenic  nerve,  to  the  left  with  the  brachio- 
cephalic artery  and  right  pneumogastric  nerve,  and  behind  with  the  pleura. 

The  left  innominate  vein  has  a  length  almost  double  that  of  the  right,  meas- 
uring 5-9  cm.  (2-3 %  in.)  from  its  origin  behind  the  sternal  end  of  the  left  clavicle 
to  its  union  with  the  right  vein  to  form  the  vena  cava.  Its  course  is  transverse 
from  left  to  right  and  at  the  same  time  slightly  downward,  and  it  extends  completely 
across  the  uppermost  part  of  the  thoracic  cavity,  resting  below  upon  the  aortic  arch, 
and  passing  in  front  of  the  left  subclavian  and  common  carotid  arteries,  the  trachea, 
the  brachio-cephalic  artery,  and  the  pneumogastric  nerve.  It  is  separated  from  the 
manubrium  sterni  by  the  insertion  of  the  sterno-hyoid  and  sterno-thyroid  muscles  and 
by  the  fatty  tissue  representing  the  thymus  gland,  and,  being  on  a  level  with  or 
slightly  above  the  upper  border  of  the  manubrium,  it  can  usually  be  felt  in  the  supra- 
sternal fossa. 

Neither  of  the  innominate  veins  possesses  valves.  The  left  is  of  somewhat  greater 
diameter  than  the  right,  owing  to  the  greater  number  of  tributaries  which  it  receives. 


THE    SUPERIOR    CAVAL   SYSTEM. 


859 


Variations. — As  pointed  out  in  the  account  of  the  development  of  the  great  veins  (page  926), 
there  is  at  one  stage  a  symmetrical  arrangement  of  the  vessels  which  open  into  the  right  auricle 
from  above  ;  in  other  words,  the  left  internal  jugular  is  continued  directly  downward  from  the 
point  where  the  left  subclavian  vein  opens  into  it  to  the  auricle,  this  downward  continuation 
being  usually  termed  the  left  superior  vena  cava.  Later  a  cross-connection,  the  left  innominate 
vein,  forms  between  the  right  and  left  jugulars  at  the  root  of  the  neck,  and  the  left  superior  vena 
cava  then  normally  undergoes  degeneration,  traces  of  it  only  persisting  as  the  oblique  vein  of 
the  left  auricle  and  the  coronary  sinus'. 

Occasionally  this  normal  progress  of  events  fails  to  occur,  the  result  being  the  complete 
absence  or  imperfect  development  of  the  left  innominate  vein  together  with  a  persistence  of  the 
left  superior  vena  cava  ;  or  else,  even  with  the  perfect  development  of  the  left  innominate,  there 
may  be  a  failure  of  the  left 

superior  vena  cava  to  degen-  pIG   __2 

erate.  Various  gradations 
between  the  embryonic  and 
adult  conditions  may  occur, 
and  the  annexed  diagram 
(Fig.  752)  shows  the  nature 
of  the  anomaly.  It  may  be 
noted  that  with  the  persist- 
ence of  the  left  superior  vena 
cava  there  is  frequently  a 
retention  of  the  communica- 
tion with  it  of  the  left  cardinal 
vein,  which  normally  be- 
comes the  v.  hemi-azygos,  — a 
condition  which  will  be  more 
especially  considered  in  con- 
nection with  the  anomalies  of 
the  azygos  veins  (page  S93). 


Left  internal  jugul 


L.  sup 


R.  pulmonary  artery 
R.  pulmonary  veins 


Practical  Consid- 
erations.—  The  left  in- 
nominate vein,  running 
horizontally  just  below  the 
upper  border  of  the  ma- 
nubrium, lies  immediately 
above  the  aortic  arch. 
When  the  latter  is  unusually  high,  and  occasionally  in  children,  the  vein — especially 
if  engorged — may  project  above  the  level  of  the  suprasternal  notch  and  may  be 
endangered  during  a  thyroidectomy,  the  removal  of  a  tumor,  or  a  low  tracheotomy. 


ior  aspect  of  heart  and  great  vessels,  showing  persistence 
of  left  superior  vena  cava  ;  (semidiagrammatic). 


Tributaries.  —  In  addition  to  the  subclavian  and  internal  jugular  veins,  by 
whose  union  they  are  formed,  each  innominate  vein  receives  (1)  the  deep  cervical, 
(2)  the  vertebral,  (3)  the  internal  mam?nary,  and  (4)  the  inferior  thyroid  veins  of 
its  side.  The  left  innominate  vein  receives  in  addition  (5)  the  superior  phrenic, 
(6)  the  thymic,  (7)  the  pericardial,  (8)  the  anterior  mediastinal,  and  (9)  the 
left  superior  i?itercostal  vein.  Of  these  the  left  superior  intercostal  vein  will  be 
described  with  the  other  intercostals. 

1.  The  Deep  Cervical  Vein. — The  deep  cervical  vein  (v.  cervicalis  profunda) 
takes  its  origin  in  a  plexus  situated  in  the  occipital  triangle  and  having  also  con- 
nected with  it  the  vertebral  and  occipital  veins.  It  passes  down  the  neck,  lying  be- 
tween the  semispinalis  cervicis  and  the  splenius  cervicis,  and  in  the  upper  part  of  its 
course  accompanies  the  deep  branch  of  the  art.  princeps  cervicis.  Lower  down  it 
accompanies  the  deep  cervical  branch  of  the  superior  intercostal  artery  and  bends 
slightly  outward  and  forward,  passes  between  the  transverse  process  of  the  seventh 
cervical  vertebra  and  the  first  rib,  and  opens  into  the  innominate  vein  either  behind 
the  vertebral  vein  or  by  a  common  trunk  with  that  vessel. 


Tributaries. — In  its  course  down  the  neck  it  receives  numerous  tributaries  from  the  deeper 
cervical  muscles,  and  opposite  each  intervertebral  foramen  which  it  passes  it  makes  connections 
with  the  vertebral  vein  and  the  veins  of  the  spinal  canal. 

The  most  important  of  its  tributaries  is,  however,  the  occipital  vein,  which  arises  in  a 
plexus  covering  the  occipital  portion  of  the  skull  and  communicating  with  branches  of  the  pos- 
terior auricular  and  temporal  veins.     It  passes  downward  with  the  occipital  artery,  pierces  the 


860  HUMAN    ANATOMY. 

trapezius  muscle  near  its  origin  from  the  superior  nuchal  line,  and  enters  the  suboccipital  tri- 
angle where  it  opens  into  the  deep  cervical  vein.  Occasionally,  however,  it  either  unites  with 
the  posterior  auricular  vein  or  opens  directly  into  the  external  jugular  below  the  posterior 
auricular.     The  mastoid  emissary  vein  (page  876)  usually  opens  into  one  of  its  branches. 

2.  The  Vertebral  Vein. — The  vertebral  vein  (v.  vertebralis)  accompanies 
the  artery  of  the  same  name  through  all  but  the  cranial  portion  of  its  course,  and  is 
usually  a  single  trunk,  although  frequently  it  is  double  or  occasionally  even  plexiform 
throughout  more  or  less  of  its  course.  It  arises  in  the  suboccipital  triangle  from  a 
plexus  of  small  veins  with  which  the  occipital  and  deep  cervical  veins  also  communi- 
cate, and  passes  downward  through  the  foramina  in  the  transverse  processes  of  the  six 
(occasionally  seven  or  five  or  even  only  four)  upper  cervical  vertebrae.  At  its  exit 
from  the  foramen  of  the  sixth  vertebra  it  is  continued  obliquely  forward  and  down- 
ward behind  the  inferior  thyroid  artery  and  the  internal  jugular  vein,  and,  passing 
usually  in  front  of,  but  occasionally  behind,  the  subclavian  artery,  opens  into  the 
innominate  vein  near  its  origin. 

The  opening  into  the  innominate  is  guarded  by  a  pair  of  valves.  Throughout 
its  course  the  vein  is  connected  to  the  periosteum,  lining  each  of  the  vertebrarterial 
canals  it  traverses,  by  fibrous  bands,  and  in  its  terminal  portion  it  is  adherent  to  the 
deep  cervical  fascia,  so  that  its  walls  do  not  collapse  even  when  it  is  emptied  of  blood. 

Tributaries. — Like  the  vertebral  artery,  the  vein  receives  tributaries  from  the  deep  mus- 
cles of  the  neck  and,  at  each  intervertebral  foramen  which  it  passes,  communicating  branches 
from  the  plexuses  in  the  spinal  canal  on  the  one  hand,  and  from  the  posterior  spinal  plexus  and 
the  deep  cervical  vein  on  the  other.  In  its  terminal  portion,  after  it  has  issued  from  the  fora- 
men in  the  transverse  process  of  the  sixth  cervical  vertebra,  it  receives  the  ascending  cervical 
vein,  which  arises  in  the  plexus  upon  the  anterior  surfaces  of  the  bodies  of  the  upper  cervical 
vertebras,  and  accompanies  the  ascending  cervical  artery  down  the  neck.  Very  frequently  it 
also  receives,  shortly  before  its  termination,  the  deep  cervical  vein. 

3.  The  Internal  Mammary  Vein. — The  internal  mammary  vein  (v.  mamma' 
ria  interna)  is  formed  by  the  union  of  the  venae  comites  of  the  musculo-phrenic  and 
superior  epigastric  arteries,  and  throughout  the  greater  part  of  its  course  is  double,  one 
stem  lying  along  the  outer  and  the  other  along  the  inner  side  of  the  artery  in  its 
course  along  the  inner  surface  of  the  anterior  thoracic  wall.  Opposite  the  second 
or  third  intercostal  space  the  two  stems  unite,  the  single  vein  so  formed  lying  to  the 
inner  side  of  the  artery  and  opening  above  into  the  innominate  vein  of  the  same 
side.      Numerous  valves  occur  in  the  course  of  the  vein. 

Tributaries. — The  tributaries  of  the  internal  mammary  veins  correspond  in  general  with 
the  branches  of  the  internal  mammary  artery,  with  the  exception  of  the  superior  phrenic,  medi- 
astinal, pericardial,  and  thymic  branches,  which  usually  open  independently  into  the  left  innom- 
inate vein.  Its  sternal  branches  form  plexuses  upon  both  surfaces  of  the  sternum,  and  so  form 
communication  with  the  vein  of  the  opposite  side,  and  the  anterior  intercostal  branches  unite 
with  the  posterior  intercostals  (page  896).  The  perforating  branches  assist  in  returning  the  blood 
from  the  pectoral  muscles,  those  of  the  first  and  second  intercostal  spaces  being  larger  than  the 
rest  in  the  female,  and  serving  to  return  a  considerable  portion  of  the  blood  from  the  mammary 
gland.  By  means  of  the  superior  epigastric  branches  the  internal  mammary  makes  connection 
with  the  subcutaneous  veins  of  the  abdomen,  and,  since  these  are  also  connected  with  the 
epigastric  and  circumflex  iliac  branches  of  the  iliac  veins,  an  anastomosis  is  formed  between  the 
superior  and  inferior  caval  systems  of  veins. 

4.  The  Inferior  Thyroid  Veins. — The  inferior  thyroid  veins  (w.  thyreoideae 
inferiores)  have  their  origin  in  a  venous  plexus  (plexus  thyreoideus  impar)  which  covers 
the  anterior  surface  and  sides  of  the  trachea  immediately  below  the  isthmus  of  the 
thyroid  gland,  the  vessels  which  form  the  plexus  issuing  from  the  substance  of  the  thy- 
roid gland,  or  in  some  cases  being  downward  prolongations  of  the  branches  of  origin 
of  the  superior  thyroid  veins.  From  the  plexus  two  or  sometimes  three  veins  descend 
the  neck,  following  paths  quite  distinct  from  those  of  the  inferior  thyroid  arteries, 
and  open  below  into  the  innominate  veins,  their  orifices  being  guarded  by  valves. 
When  three  veins  are  present,  the  odd  one  occupies  a  median  position  and  is  known 


THE   SUPERIOR   CAVAL  SYSTEM.  86 1 

as  the  vena  thyreoidea  ima,  corresponding  to  the  artery  of  the  same  name,  which, 
however,  need  not  be  present  with  it.  It  opens  usually  into  the  left  innominate 
vein,  but  occasionally  is  prolonged  inward  to  terminate  in  the  superior  vena  cava. 

Tributaries. — The  plexus  thyreoideus  impar  receives  communications  from  the  superior 
thyroid  veins  and  also  has  opening"  into  it  the  inferior  laryngeal  veins  (vv.  laryngeae  inferiores ) 
which  descend  from  the  larynx.  The  inferior  thyroid  veins  receive  directly  brandies  from  the 
trachea  (vv.  tracheales)  and  from  the  oesophagus  (vv.  oesophageae). 

Practical  Considerations. — An  incision  across  the  inferior  thyroid  vein, 
whose  walls,  being  imbedded  in  inflamed  tissue,  could  not  collapse,  has  caused 
sudden  death  by  the  entrance  of  air.  Parise,  in  attempting  to  seize  the  divided 
inferior  thyroid  vein  during  tracheotomy,  lifted  the  superficial  wall  only,  thus  per- 
mitting air  to  enter  the  vein  with  a  fatal  result  (Allen). 

5.  The  Superior  Phrenic  Vein. — The  superior  phrenic  vein  (v.  phrenica 
superior)  has  its  origin  upon  the  upper  surface  of  the  diaphragm  and  ascends  through 
the  thorax,  lying  between  the  pericardium  and  pleura  and  accompanying  the  phrenic 
nerve  and  the  superior  phrenic  artery,  of  which  it  is  a  companion  vein.  Usually  the 
veins  of  both  sides  are  double.  They  open  above  into  the  left  innominate  vein,  fre- 
quently uniting  with  the  thymic,  pericardial,  and  mediastinal  veins  before  their  termi- 
nation.     They  are  provided  with  valves  both  at  their  orifice  and  along  their  course. 

6.  The  Thymic  Veins. — The  thymic  veins  (vv.  thyraicae)  are  rather  insig- 
nificant in  the  adult  and  are  usually  two  or  three  in  number.  They  arise  in  the 
adipose  tissue  which  replaces  the  thymus  gland  and  empty  above  into  the  left  innomi- 
nate vein,  frequently  uniting  with  the  superior  phrenic  veins.  In  the  child  they  are 
of  considerable  size  in  correlation  with  the  development  of  the  thymus  gland. 

7.  The  Pericardial  Veins. — The  pericardial  veins  (vv.  pericardiacae)  vary 
considerably  in  number.  They  are  all  small,  and  empty  in  part  into  the  left  innomi- 
nate vein  and  in  part  into  the  azygos  and  internal  mammary  veins. 

8.  The  Anterior  Mediastinal  Veins. — The  anterior  mediastinal  veins  (vv. 
mediastinales  anteriores),  like  the  preceding,  are  variable  in  number  and  small.  They 
arise  in  the  anterior  mediastinum  and  open  above  into  the  left  innominate  vein. 

The  Internal  Jugular  Vein. 

The  internal  jugular  vein  (v.  jugularis  interna)  (Figs.  753,  760)  is  the  principal 
venous  trunk  of  the  neck.  It  is  the  continuation  of  the  lateral  sinus  at  the  jugular 
foramen,  and  descends  the  neck  in  company  with  the  internal  and  common  carotid 
arteries  to  a  point  a  little  external  to  the  sterno-clavicular  articulation,  where  it  unites 
with  the  subclavian  to  form  the  innominate  vein.  At  its  origin  it  rests  upon  the  anterior 
sloping  surface  of  the  jugular  process  of  the  occipital  bone,  and  usually  presents  at 
this  point  a  distinct  bulbous  enlargement  (bulbus  venae  jugularis  superior )  measuring 
about  1.5  cm.  in  diameter.  Below  the  bulbus  superior,  at  its  exit  from  the  jugular 
foramen,  the  diameter  of  the  vein  averages  about  9  mm.,  although  subject  to  consider- 
able variation,  and  usually  differing  on  the  two  sides,  since  the  lateral  sinuses,  of 
which  the  veins  are  the  continuations,  differ  on  the  two  sides,  that  of  the  right  being 
in  the  majority  of  cases  the  larger.  As  it  descends  the  neck  the  vein  gradually 
increases  in  size  as  it  receives  its  various  tributaries,  and  just  before  its  union  with  the 
subclavian  vein  it  presents  a  more  or  less  pronounced  spindle-shaped  enlargement 
(bulbus  venae  jugularis  inferior).  This  dilatation  is  usually  much  more  distinct  in  the 
right  vein  than  in  the  left,  and  at  its  upper  end  is  provided  with  a  pair  of  valves  or  else 
with  a  single  one,  the  cavities  of  the  valves  being  directed  downward  as  if  to  prevent 
an  upward  flow  of  blood.  Even  when  a  pair  is  present  they  are  insufficient,  but  they 
may  nevertheless  play  an  important  part  in  preventing  the  blood  from  flowing  into 
the  innominate  through  the  subclavian  vein  and  from  producing,  during  the  systole 
of  the  auricle,  a  back  pressure  in  the  cerebral  veins  which  are  in  connection  with  the 
internal  jugular.  Since  the  right  innominate  is  much  more  nearly  in  a  line  with  the 
vena  cava  superior  than  is  the  left,  the  greater  development  of  the  inferior  bulb  in 
the  right  internal  jugular  can  be  readily  understood. 


862 


HUMAN   ANATOMY. 


Relations. — In  the  upper  part  of  its  course  the  internal  jugular  rests  upon  the 
rectus  capitis  lateralis  and  the  transverse  processes  of  the  upper  cervical  vertebrae. 
To  its  inner  side  and  somewhat  in  front  of  it  is  the  internal  carotid  artery,  the  glosso- 
pharyngeal, pneumogastric,  spinal  accessory,  and  hypoglossal  nerves  separating  the 
two  vessels  above.  The  external  branch  of  the  spinal  accessory  crosses  it  obliquely 
either  in  front  or  behind,  and  somewhat  lower  it  is  crossed  anteriorly  by  the  stylo- 
hyoid muscle  and  the  posterior  belly  of  the  digastric  and  also  by  the  occipital  and 
posterior  auricular  arteries.  To  its  inner  side  is  the  wall  of  the  pharynx,  with  which  it 
is  not,  however,  directly  in  contact. 

Throughout  the  neck  it  lies  beneath  the  sterno-cleido-mastoid  muscle,  imme- 
diately to  the  outer  side  of  the  common  carotid  artery,  being  enclosed  in  a  common 


Superficial  temporal  vein 
Posterior  auricular 


Fig.  753. 


y  Temporal  muscle,  cut 

Internal  maxillary  \ 


External  auditory  meatus 
Mastoid 
Occipital 
Internal  maxillary 

Temporo-maxillary 

Posterior  trunk  of  temporo- 
maxillary 
Anterior  trunk  of  temporo- 

External  jugular 
Lingual 

Internal  carotid  artery 

Internaljugiilarveiii 

posterior  external  jugular  vein 

Superior  thyroid  vein 

Common  carotidartery 


Ext.  carotid  artery 
Coninuinication  bet.  lin 
gual  and 
Middle  thyroid 


ulai 


Right  innominate  vein  I.  rib    Internal  mammary  vein        Superior  vena  cava  Inferior  thyroid  veins 

Dissection  showing  deep  veins  of  neck  and  head. 

sheath  with  it,  as  is  also  the  pneumogastric  nerve,  which  lies  behind  and  between  the 
two  vessels.  Below  the  omohyoid  muscle  the  vein  tends  to  separate  from  the  artery, 
passing  somewhat  more  anteriorly.  In  this  part  of  its  course  it,  or,  to  be  more  pre- 
cise, the  inferior  bulb,  is  situated  immediately  behind  the  space  which  separates  the 
two  heads  of  the  sterno-cleido-mastoid.  Behind,  it  rests  upon  the  inner  border  of  the 
scalenus  anticus,  crosses  the  subclavian  artery,  and  has  the  pneumogastric  and  phrenic 
nerves  passing  downward  on  either  side. 

Variations.— Variations  of  the  internal  jugular  vein  are  not  numerous.  It  may  be  noted, 
however,  that  in  its  course  down  the  neck  it  occasionally  overlaps  the  carotid  artery  to  a  con- 
siderable extent,— a  condition  which  is  especially  marked  in  the  region  of  the  inferior  bulb  when 
this  is  well  developed. 


THE   SUPERIOR   CAVAL  SYSTEM.  863 

The  left  internal  jugular  has  been  observed  much  reduced  in  size,  there  being  a  compen- 
satory enlargement  of  the  corresponding  external  jugular,  and  it  may  be  doubled  throughout  a 
greater  or  less  portion  of  its  course,  although  always  single  at  either  extremity.  In  addition 
to  the  normal  tributaries  described  below,  it  may  receive  the  temporo-maxillary  vein,  the  verte- 
bral, superior  laryngeal,  or  left  superior  intercostal,  a  bronchial  vein,  the  suprascapular,  or  the 
transverse  cervical  vein. 

Practical  Considerations. — The  internal  jugular  vein — the  largest  of  the 
superficially  placed  veins  of  the  body — may  be  involved  in  cut-throat  or  other  wounds 
of  the  neck.  Like  the  carotid,  it  usually  escapes  in  attempts  at  suicide  on  account  of  the 
usual  position  assumed — with  the  chin  elevated  and  the  head  thrown  back  so  that  the 
muscles  are  rendered  tense  and  prominent  and  the  vessels  are  protected.  If  the 
wound  is  above  the  thyroid  cartilage  they  are  still  safer  on  account  of  their  inclination 
backward,  and  such  a  wound  may  reach  the  spinal  column  without  injuring  them.  In 
wounds  below  the  thyroid  if  the  air  passages  are  opened  in  attempted  suicide,  the 
sudden  exit  of  air  from  the  lungs,  accompanied  by  collapse  of  the  chest,  may,  it  has 
been  suggested,  result  in  the  dropping  of  the  arm  carrying  the  weapon  before  the 
wound  has  reached  the  level  of  the  vessels,  although  they  are  here  more  vulnerable 
than  they  are  above.  The  internal  jugular,  the  other  veins  of  the  neck,  and  the 
subclavian  and  axillary  veins,  are  greatly  influenced  by  respiration,  emptying  during 
inspiration,  distending  during  expiration — the  "respiratory  wave,"  or  "venous 
pulse. ' '  Their  attachments  to  the  fascia  keep  them  from  entirely  collapsing.  This 
is  especially  noticeable  in  the  internal  jugular.  After  the  carotid  sheath  has  been 
opened  the  vein  will  vary  in  appearance  from  a  distended  thin-walled  tube  perhaps 
half  an  inch  in  diameter,  (expiration),  to  a  flaccid,  ribbon-like  structure  with  walls 
apparently  in  contact  (inspiration).  During  inspiration  air  may  thus  be  readily  drawn 
into  one  of  these  veins  if  it  has  been  wounded,  and  if  the  wound  is  dry,  or  if  pressure 
is  not  immediately  applied  to  the  vein  on  the  cardiac  side  of  the  wound.  If  the  air  is 
in  large  quantity  it  may  cause  instant  death  when  it  reaches  the  right  auricle  by  over- 
distension and  paralysis  of  the  right  side  of  the  heart  ;  or  sometimes  less  rapidly  by 
asphyxia  following  air  embolism  of  the  pulmonary  veins. 

The  internal  jugular  vein  may  be  infected  secondarily  to  infective  intracranial 
sinus  thrombosis,  especially  of  the  sigmoid.  Phlebitis  or  thrombosis  of  the  internal 
jugular  is  attended  by  pain  and  tenderness  along  the  course  of  the  vein,  and  later  by 
the  development  of  a  cord-like  mass  to  the  inner  side  of  the  sterno-mastoid  muscle 
and  the  outer  side  of  the  carotid  artery.  This  may  involve  the  whole  length  of  the 
vein  but  is  apt  to  be  confined  to  the  upper  third.  When  an  infected  thrombus  in  the 
sigmoid  sinus  has  undergone  such  extensive  disintegration  that  it  is  unlikely  to  be 
entirely  removed  by  operative  obliteration  of  the  upper  two-thirds  of  the  sinus,  or  -» 
when  in  a  thrombosed  internal  jugular,  giving  the  sensation  of  a  hard  cord-like  struc- 
ture, its  upper  part  becomes  soft  from  disintegration  of  the  thrombus  and  this  disin- 
tegration descends,  ligation  of  the  vessel  below  this  point  usually  becomes  necessary 
(Macewen).  The  ligation  shuts  off  the  main  channel  between  the  sigmoid  sinus  and 
the  lungs,  although  the  latter  may  still  be  infected  by  way  of  the  occipital  sinus  and 
condylar  veins  and  the  subclavian  vein. 

The  vessel  is  approached  by  the  same  incision  as  that  made  for  ligation  of  a  caro- 
tid. The  vascular  sheath  is  opened  well  to  the  outer  side  so  that  the  carotid  com- 
partment may,  if  possible,  be  left  intact.  The  vein  should  be  tied  in  two  places  and 
divided  between  the  ligatures. 

After  occlusion  of  the  vein  either  by  ligature  or  by  pressure  from  a  growth,  the 
blood  from  the  corresponding  side  of  the  head  passes  by  a  transverse  vein  to  the 
internal  jugular  of  the  opposite  side. 

Tributaries. — In  addition  to  the  lateral  and  the  inferior  petrosal  sinuses,  which 
will  be  described  with  the  other  cranial  sinuses,  the  internal  jugular  receives  the 
following  tributaries:  (1)  the  pharyngeal,  (2)  the  facial,  (3)  the  lingual,  (4)  the 
superior  thyroid,  and  (5)  the  middle  thyroid  veins. 

1.  The  Pharyngeal  Veins. — The  pharyngeal  veins  (vv.  pharvngeae)  are  small 
vessels,  varying  in  number,  which  open,  either  independently  or  after  having  united 
to  a  single  stem,  either  directly  into  the  internal  jugular  or  indirectly  by  way  of  the 


864  HUMAN    ANATOMY. 

lingual  or  superior  thyroid  vein.  They  take  their  origin  from  a  venous  plexus 
(plexus  pharyngeus)  which  covers  the  outer  surface  of  the  pharynx,  lying  between 
the  constrictor  muscles  and  the  pharyngeal  portion  of  the  bucco-pharyngeal  fascia. 
In  addition  to  branches  from  the  pharyngeal  wall,  this  plexus  also  receives  tributaries 
from  the  anterior  recti  and  longus  colli  muscles,  and  from  the  soft  palate,  the  tonsillar 
plexus  and  the  Eustachian  tube,  and  has  opening  into  it  branches  from  a  plexus  which 
surrounds  the  internal  carotid  artery  in  its  course  through  the  carotid  canal,  communi- 
cating above  with  the  cavernous  sinus.  It  also  receives  the  veins  (vv.  canalis  pterygoidei) 
which  accompany  the  Vidian  artery  through  its  canal,  and  communicates  with  the 
pterygoid,  oesophageal,  and  vertebral  plexuses. 

2.  The  Facial  Vein. — The  facial  vein  (v.  facialis  anterior)  (Fig.  754)  is 
formed  at  about  the  inner  extremity  of  the  eyebrow  by  the  union  of  the  frontal  and 
supraorbital  veins.  From  its  point  of  origin  it  skirts  around  the  inner  border  of  the 
orbit  and  is  then  directed  obliquely  downward  and  backward  across  the  face,  crosses 
over  the  anterior  inferior  angle  of  the  masseter  muscle  and  the  ramus  of  the  mandible 
a  short  distance  in  front  of  the  angle,  and  is  thence  continued  onward  across  the 
posterior  part  of  the  submaxillary  and  the  upper  part  of  the  superior  carotid  triangles 
to  open  into  the  internal  jugular  at  about  the  level  of  the  hyoid  bone.  It  follows 
in  a  general  way  the  course  of  the  corresponding  artery,  lying  posterior  to  it,  but 
the  path  across  the  face  is  much  more  direct  than  that  followed  by  the  artery. 

That  portion  of  the  vein  which  extends  from  the  junction  of  the  frontal  and  supra- 
orbital arteries  to  the  lower  border  of  the  orbit  is  usually  termed  the  angular  vein, 
and  branches  arise  from  this  which  pass  backward  into  the  orbit  to  communicate 
with  the  ophthalmic  vein.  Just  below  the  ramus  of  the  mandible  it  usually  receives 
a  large  communicating  branch  from  the  external  jugular,  and  the  portion  which  in- 
tervenes between  this  communication  and  the  internal  jugular  is  termed  the  common 
facial  vein  (v.  facialis  communis).  Both  the  facial  and  the  angular  veins  are  usually 
described  as  being  destitute  of  valves  ;  these  structures  do  occur,  however,  but  they 
are  always  insufficient  and  form  no  bar  to  the  passage  of  blood  in  an  inverse  direc- 
tion— i.-,e. ,  from  the  facial  and  angular  backward  into  the  ophthalmic  veins. 

Relations. — The  angular  vein  rests  upon  the  nasal  process  of  the  maxillary 
vein  internal  to  the  lachrymal  sac.  In  its  upper  portion  the  facial  vein  lies  under 
cover  of  the  orbicularis  palpebrarum,  and  it  also  passes  beneath  the  zygomatic  muscles, 
but  is  superficial  to  the  other  muscles  of  the  face.  In  its  inframandibular  or  cervical 
portion  it  lies  beneath  the  platysma  in  a  groove  in  the  submaxillary  gland. 

Variations.— The  upper  portion  of  the  facial  vein  may  be  greatly  reduced  in  size.     Below, 
»  it  frequently  unites  with  the  lingual  vein  to  form  a  linguo-facial  trunk,  which  may  also  be  joined 
by  the  superior  thyroid.     Instead  of  opening  into  the  internal  jugular,  it  occasionally  passes 
across  the  sterno-cleido-mastoid  muscle  to  unite  with  the  external  or  anterior  jugular. 

Practical  Considerations. — Allen  has  called  attention  to  the  fact  that  the 
venous  supply  of  the  face  differs  in  some  important  particulars  from  that  of  the  trunk 
and  limbs.  In  the  last-named  localities,  both  deep  and  superficial  currents  flow  in 
the  same  direction  towards  the  heart.  -The  facial  trunk,  however,  is  not  formed  by 
primal  venules,  as  is  commonly  the  case,  but  by  branches  communicating  with  the 
frontal  and  supraorbital  veins,  and  by  a  transverse  branch  found  at  the  bridge  of 
the  nose. 

The  two  most  important  communications  with  the  cavernous  sinus  are  through 
the  ophthalmic  vein,  which  receives  tributaries  from  the  angular  vein,  and  the  deep 
facial  vein,  which  empties  into  the  pterygoid  plexus,  which  in  its  turn  communicates 
with  the  cavernous  sinus  by  veins  passing  through  the  foramen  ovale.  The  veins 
corresponding  to  the  deep  parts  of  the  face,  other  than  those  mentioned,  also  seek 
an  outlet  in  the  same  direction,  so  that  much  of  the  superficial  blood  of  the  upper 
part  and  side  of  the  face  passes  inward  to  the  brain-case  and  to  the  interior  of  the 
facial  region,  while  the  remaining  portion  flows  downward  to  join  the  jugular  veins. 

The  facial  vein  at  its  lower  end  receives  a  large  communicating  branch  from  the 
external  jugular,  and  therefore  at  or  below  that  point  carries  a  considerable  volume 
of  blood,  making  wounds  of  the  vein  dangerous. 


THE   SUPERIOR   CAVAL  SYSTEM.  865 

The  facial  vein  is  said  to  be  less  flaccid  than  most  superficial  veins,  and  there- 
fore to  remain  more  patent  after  section  ;  it  possesses  either  imperfectly  developed 
or  rudimentary  valves,  or  none  at  all.  As  a  consequence  of  these  facts,  septic  dis- 
ease— malignant  pustule,  furuncle,  carbuncle,  cancrum  oris — involving  the  face  or 
forehead,  is  exceptionally  dangerous,  as  the  infection  may  spread  by  way  of  the 
ophthalmic  vein  or  the  pterygoid  plexus  to  the  cavernous  sinus  and  result  in  a  fatal 
thrombosis  or  meningitis. 

The  relations  existing  between  the  venous  blood  of  the  face  and  that  of  the 
brain-case  are  rendered  evident  by  the  fact  that  the  state  of  the  circulation  of  the 
external  nose  is  sometimes  an  index  of  the  condition  of  the  vessels  of  the  brain. 
Moreover,  in  cases  of  orbital  or  intracranial  tumors,  the  ophthalmic,  angular,  and 
facial  veins  become  congested,  dilated,  and  tortuous  from  pressure-interference  with 
the  venous  current. 

The  line  of  the  facial  vein  is  from  the  canthus  of  the  eye  to  a  point  on  the  mandible 
at  the  anterior  border  of  the  masseter  muscle  and  just  behind  the  facial  artery.  This 
line  is  straight  instead  of  tortuous,  as  is  the  case  with  that  of  the  latter  vessel. 

Tributaries. — The  tributaries  of  the  facial  vein  are  (a)  the  frontal  and  (b)  the  supraorbital, 
by  the  union  of  which  it  is  formed.  In  addition  it  receives  in  its  course  across  the  face  (c)  the 
palpebral,  (d)  the  lateral  nasals,  (e)  the  superior  labial,  (f)  the  inferior  labial,  (g)  the  deep 
facial,  (h)  the  masseteric,  and  (i  )  the  anterior  parotid  veins.  In  its  cervical  portion  it  has  open- 
ing into  it  (/  )  the  inferior  or  descending  palatine,  and  (k)  the  submental  veins. 

(a)  The  frontal  veins  ( vv.  frontales)  descend  over  the  forehead  on  either  side  of  the  median 
line,  lying  immediately  beneath  the  skin  upon  the  frontalis  muscle.  The  branches  from  which 
they  take  origin  communicate  at  the  sides  and  vertex  of  the  skull  with  tributaries  of  the  occip- 
ital and  temporal  veins,  and  also  through  small  foramina  in  the  frontal  bone  with  the  superior 
longitudinal  sinus.  The  two  veins  are  connected  by  numerous  cross-branches,  and  not  infre- 
quently unite  more  or  less  completely  to  form  a  single  median  stem  which  bifurcates  below. 
Each  vein  terminates  at  the  inner  angle  of  the  orbit  by  uniting  with  the  corresponding  supraor- 
bital vein  to  form  the  angular. 

At  the  root  of  the  nose  the  two  veins  are  usually  united  by  a  distinct  cross-branch,  the 
nasal  arch,  which  receives  from  below  the  dorsal  nasal  veins. 

(b)  The  supraorbital  vein  (v.  supraorbital)  is  a  relatively  large  trunk  which  runs  trans- 
versely above  the  superior  margin  of  the  orbit  and  consequently  is  quite  distinct  from  the  artery 
of  the  same  name.  It  arises  at  the  external  angle  of  the  orbit,  where  it  communicates  with 
affluents  of  the  temporal  veins,  and  passes  inward  beneath  the  orbicularis  palpebrarum,  and, 
piercing  that  muscle  just  above  the  inner  angle  of  the  orbit,  unites  with  the  frontal  vein  to  form 
the  angular. 

It  receives  numerous  small  branches  from  neighboring  regions  and  from  the  diploic  vein 
of  the  frontal  bone,  and  at  the  supraorbital  notch  it  communicates  with  the  ophthalmic  system 
of  veins. 

(c)  The  palpebral  veins  (vv.  palpebrals  superiores  et  inferiores)  are  small  vessels  which  take 
their  origin  from  the  venous  plexus  of  the  eyelids  and  open  into  the  angular  vein.  The  palpe- 
bral plexus  also  communicates  laterally  with  the  affluents  of  the  temporal  veins. 

(d  )  The  lateral  nasal  veins  (vv.  nasales  externae)  arise  in  a  rich  plexus  which  occupies  the 
alas  and  tip  of  the  nose  and  with  which  the  dorsal  nasal  vein  communicates  and  also  branches  from 
the  extensive  pituitary  plexus,  these  latter  branches  emerging  along  the  line  of  junction  of  the 
nasal  bones  and  cartilage.  The  veins  extend  upward  and  backward  and  open  into  the  lower 
part  of  the  angular  vein. 

(e)  The  superior  labial  or  coronary  vein  (v.  labialis  superior)  takes  its  origin  in  a  plexus  in 
the  substance  of  the  upper  lip  with  which  branches  from  the  septum  and  ala;  of  the  nose  com- 
municate. The  course  of  the  vein  is  independent  of  that  of  the  artery  of  the  same  name,  passing 
backward  and  somewhat  upward  to  the  naso-labial  groove,  and  opening  into  the  facial  vein 
about  opposite  the  ala  of  the  nose. 

(/)  The  inferior  labial  vein  (v.  labialis  inferior)  arises  from  a  venous  plexus  in  the  lower  lip 
and  passes  downward  and  outward  to  open  into  the  facial  just  after  it  has  crossed  the  ramus  of  the 
mandible.  Usually  a  second  vein,  the  inferior  coronary,  also  arises  from  the  inferior  labial  plexus 
and  passes  almost  horizontally  outward  to  open  into  the  facial  a  little  below  the  angle  of  the  mouth. 

(g)  The  deep  facial  vein,  also  termed  the  anterior  internal  maxillary,  takes  its  origin  from 
the  pterygoid  plexus  (page  8S2)  over  the  tuberosity  of  the  maxilla,  through  which  it  receives 
branches  from  a  net-work  lying  beneath  the  mucous  membrane  lining  the  antrum  of  Highmore. 
It  passes  forward  and  downward  between  the  buccinator  and  masseter  muscles,  and  opens  into 
the  outer  surface  of  the  facial  where  that  vein  passes  beneath  the  zygomatic  muscle. 

55 


866 


HUMAN    ANATOMY. 


(//)  The  masseteric  veins  (vv.  massetericae)  are  several  small  veins  which  return  the  blood 
from  the  masseteric  and  buccinator  muscles,  opening  into  the  outer  surface  of  the  facial  vein. 

(i  )  The  anterior  parotid  veins  (vv.  parotideae  anteriores)  consist  of  several  small  veins  which 
issue  from  the  anterior  border  of  the  parotid  gland  and  from  the  socia  parotidis.  They  follow 
the  parotid  duct,  around  which  they  form  a  net-work,  and  open  into  the  outer  surface  of  the 
facial  vein. 

(J  )  The  inferior  or  descending  palatine  vein  (v.  palatina)  accompanies  the  ascending  palatine 
or  tonsillar  branch  of  the  facial  artery.  It  takes  its  origin  in  the  tonsillar  plexus  and  descends 
upon  the  side  of  the  pharynx  to  open  into  the  facial  after  it  has  crossed  the  ramus  of  the  mandible. 


Fig.  754. 


Superficial 

temporal 
Middle  temporal 


Occipital  vein 
Internal  maxillary 

Temporo- 


<ill:irv  vein 
"  :ul; 


Posterior  a 


between  facial 
and  external 
jugular  vein 
External  jugul 

Tributary  of  t: 

verse  cervical 

Posterior  ext< 

jugular  veir 


of  head  and  neck ;  external  jugular  lies  beneath  platysma  muscle, 
wriich  has  been  partly  removed. 


[k)  The  submental  vein  (v.  submentals)  accompanies  the  artery  of  the  same  name.  It 
rests  upon  the  superficial  surface  of  the  mylo-hyoid  muscle  and  passes  backward  and  outward  in 
the  submaxillary  triangle,  beneath  the  platysma,  to  open  into  the  cervical  portion  of  the  facial. 
It  communicates  with  the  sublingual  vein  by  several  branches  which  perforate  the  mylo-hyoid 
muscle,  and,  in  addition  to  cutaneous  and  muscular  branches,  also  receives  tributaries  from  the 
submaxillary  gland,  these  latter  vessels,  however,  frequently  opening  directly  into  the  facial  as 
it  traverses  the  groove  upon  the  gland. 


THE   SUPERIOR   CAVAL  SYSTEM.  867 

3.  The  Lingual  Vein. — The  lingual  vein  (v.  lingualis)  is  a  short  trunk  which 
either  opens  directly  into  the  internal  jugular  or  unites  with  the  facial  vein  to  form  a 
linguo  -facial  trunk.  It  is  formed  by  the  union  of  two  vessels,  the  deep  lingual  veins, 
which  are  the  venae  comites  of  the  lingual  artery,  and  the  sublingual. 

The  deep  lingual  veins  are  of  small  calibre  and  accompany  the  lingual  artery 
throughout  its  entire  course,  numerous  cross-connections  between  them  involving  the 
artery  as  in  a  plexus.  Shortly  before  opening  into  the  lingual  stem  the  two  veins  unite, 
and  into  the  vessel  so  formed  the  companion  veins  of  the  dorsal  artery  of  the  tongue 
(vv.  dorsales  linguae)  open,  these  vessels  communicating  with  the  tonsillar  plexus  and 
the  superior  laryngeal  vein. 

The  sublingual  vein,  also  termed  the  ranine,  has  its  origin  on  the  under  sur- 
face of  the  tip  of  the  tongue,  beneath  the  mucous  membrane.  It  passes  backward, 
at  first  in  company  with  the  submaxillary  duct,  and,  after  receiving  communicating 
branches  from  the  deep  lingual  and  the  submental  veins,  it  passes  to  the  outer  side 
of  the  hyoglossus  muscle  and  continues  backward  in  company  with  the  hypoglossal 
nerve,  whence  it  has  been  termed  the  v.  comitans  n.  hypoglossi. 

All  the  branches  of  the  lingual  vein  are  provided  with  valves. 

Variations. — Considerable  variation  exists  in  the  extent  to  which  the  lingual  vein  is  de- 
veloped, both  its  constituent  tributaries  as  well  as  the  dorsales  lingua?  sometimes  opening  inde- 
pendently into  the  internal  jugular.  It  may  open  into  either  the  external  or  anterior  jugular 
instead  of  the  internal,  and  the  deep  Unguals  may  open  into  the  pharyngeal  vein.  Occasionally, 
by  the  enlargement  of  the  connection  normally  occurring,  the  submental  vein  becomes  a  tribu- 
tary of  the  sublingual. 

4.  The  Superior  Thyroid  Vein. — The  superior  thyroid  vein  (v.  thyreoidea 
superior)  accompanies  the  artery  of  the  same  name.  It  arises  in  the  upper  portion 
of  the  plexus  which  encloses  the  thyroid  gland,  communicating  through  it  with  its  fellow 
of  the  opposite  side  and  with  the  middle  and  inferior  thyroid  veins.  It  is  directed  up- 
ward and  backward,  and  opens  either  directly  into  the  internal  jugular  or  more  usually 
into  the  lingual  or  the  linguo-facial  trunk. 

Tributaries. — The  following  are  received  by  the  superior  thyroid  vein,  (a)  The  superior 
laryngeal  vein  (v.  laryngea  superior),  which  arises  in  the  pharyngo-laryngeal  recess  from  a  plexus 
which  receives  the  blood  from  the  aryepiglottidean  fold  and  the  laryngeal  musculature  and  com- 
municates with  the  vv.  dorsales  linguae  above  and  also  with  the  lower  portion  of  the  pharyngeal 
plexus.  It  passes  upward  and  backward  in  company  with  the  corresponding  nerve  and  artery 
and  opens  into  the  superior  thyroid  vein  or  occasionally  into  the  linguo-facial  trunk  or  the 
anterior  jugular.  (<5)  The  crico-thyroid  vein  is  a  slender  vessel  which  accompanies  the  artery 
of  the  same  name,  [c)  The  sterno-mastoid  vein  (v.  sternocleidomastoidea)  receives  blood  from 
the  sterno-cleido-mastoid  muscle  and  is  associated  with  the  artery  of  the  same  name. 

5.  The  Middle  Thyroid  Vein. — The  middle  thyroid  vein  is  not  always 
present  and  may  be  regarded  as  accessory  to  the  superior  thyroid.  It  issues  from 
the  thyroid  plexus,  opposite  the  lower  part  of  the  lateral  lobe  of  the  gland,  and  passes 
downward  and  outward,  independently  of  any  artery,  to  open  into  the  internal  jugular 
at  the  junction  of  its  middle  and  lower  thirds. 

The  Sinuses  of  the  Dura  Mater. 

The  sinuses  of  the  dura  mater  (sinus  durae  matris)  form  a  series  of  channels, 
frequently  of  considerable  size,  occupying  clefts  in  the  substance  of  the  dura  mater. 
They  receive  the  cerebral,  meningeal,  and  diploic  veins  and,  in  addition,  communicate 
with  the  extracranial  veins  by  numerous  connecting  veins  known  as  emissary  veins,  the 
largest  and  most  important  of  which  are  the  ophthalmic  veins.  They  are  drained 
mainly  by  the  internal  jugular.  A  statement  of  their  general  structure  and  a  brief 
description  of  the  blood-lakes  associated  with  them  have  already  been  given  (page  851). 

1.  The  Lateral  Sinus. —  The  lateral  sinus  (sinus  transversus)  (Figs.  756,  757) 
has  its  origin  opposite  the  internal  occipital  protuberance,  at  which  point  there  is  a 
meeting  of  five  sinuses,  the  two  lateral,  the  superior  longitudinal,  the  straight,  and 


868  HUMAN    ANATOMY. 

the  occipital.  From  this  meeting-point,  which  is  termed  the  torcular  Herophili  (con- 
fluens  sinuum),  each  lateral  sinus  passes  outward  over  the  squamous  portion  of  the 
occipital  bone  along  the  line  of  the  attachment  of  the  tentorium  cerebelli,  and,  passing 
over  the  posterior  inferior  angle  of  the  parietal,  is  continued  inward  upon  the  inner 
surface  of  the  mastoid  portion  of  the  temporal  and  the  jugular  process  of  the  occipital 
to  reach  the  jugular  foramen,  where  it  opens  into  the  internal  jugular  vein.  As  it  passes 
upon  the  mastoid  portion  of  the  temporal,  it  leaves  the  line  of  attachment  of  the  ten- 
torium cerebelli,  passing  somewhat  downward  as  well  as  inward,  and  follows  the  line 
of  junction  of  the  petrous  and  mastoid  portions  of  the  bone  in  a  somewhat  S-shaped 
course,  whence  this  portion  of  it  is  frequently  termed  the  sigmoid  simis. 

A  difference  in  size  is  usually  noticeable  in  •  the  sinuses  of  the  opposite  sides, 
that  of  the  right  being  usually  the  larger,  and  this  difference  is  due  to  the  mode  in 
which  the  various  sinuses  meet  at  the  torcular  Herophili.  Most  frequently  the 
superior  longitudinal  sinus  communicates  mainly  with  the  right  lateral,   while  the 

Fig.  755. 


Superior  longitudinal  sinus 


Fibro-aponeurotic  layers  of  scalp 
Parietal  layer  of  dura 
Bone 


Inferior  longitudi- 
nal sinus,  cut 
obliquely 


Tentorium 
Left  lateral  sinus 


Tentorium 

Right  lateral  sinus 


Frontal  section  of  head,  viewed  from  behind,  showing  relations  of  dura  mater  to  sinuses 
and  to  cerebral  hemispheres  and  cerebellum. 

straight  sinus  opens  principally  into  the  left,  the  greater  amount  of  blood  carried  by 
the  superior  longitudinal,  as  compared  with  that  transmitted  by  the  straight,  resulting 
in  the  larger  size  of  the  right  lateral  sinus.  Indeed,  in  some  cases  the  right  lateral 
sinus  is  practically  the  direct  continuation  of  the  superior  longitudinal  and  the  left 
lateral  of  the  straight,  the  two  laterals  being  connected  only  by  a  short  and  relatively 
small  connecting  arm,  which  represents  the  torcular  Herophili.  Throughout  that 
portion  of  their  courses  in  which  the  lateral  sinuses  lie  in  the  line  of  attachment  of  the 
tentorium  cerebelli  they  are  triangular  in  cross-section  (Fig.  755),  but  in  their  mastoid 
(sigmoid)  portion  they  are  semi-circular  ;  the  right  sinus  has  a  diameter  of  from 
9-12  mm.,  while  the  left  varies  from  3-5  mm.  At  the  jugular  foramen  each  sinus 
makes  a  sudden  bend  and  opens  either  directly  into  the  summit  of  the  superior  jugular 
bulb,  or  else  at  a  varying  distance  downward  upon  the  anterior  surface  of  the  bulb, 
the  upper  extremity  of  which  then  forms  a  dome-shaped  structure  projecting  upward 
into  the  jugular  foramen. 


THE   SUPERIOR   CAVAL  SYSTEM.  869 

Tributaries. — The  lateral  sinuses,  in  addition  to  the  sinuses  which  communicate  with  them 
at  the  torcular  Herophili,  receive  the  following  tributaries,  most  of  which  will  be  described  in 
greater  detail  later:  (a)  the  posterior  inferior  cerebral  veins,  which  pass  backward  from  the 
temporo-sphenoidal  regions  of  the  cerebral  hemispheres  ;  ( b )  some  of  the  inferior  cerebellar  veins  ; 
(c)  the  superior  petrosal  sinus,  this  latter  communicating  with  it  just  where  it  leaves  the  line  of 
attachment  of  the  tentorium  cerebelli.  Into  the  sigmoid  portion  there  open  (d  )  the  internal  au- 
ditory veins  (vv.  auditivaeinternae),  which  issue  from  the  internal  auditory  meatus  ;  (e)  the  mastoid 
emissary  vein  (page  S76)  ;  and  (_/)  some  of  the  veins  of  the  medulla  oblongata  and  pons. 

Variations. — Considerable  variation  exists  in  the  relative  sizes  of  the  right  and  left  lateral 
sinuses,  in  accordance  as  the  superior  longitudinal  sinus  opens  more  or  less  directly  into  one 
or  the  other.  As  stated,  the  tendency  is  for  the  superior  longitudinal  to  open  into  the  right 
lateral ;  quite  often,  however,  it  opens  into  the  left,  and  occasionally  it  may  communicate  equally 
with  both.  In  100  crania,  Riidinger  found  that  the  right  lateral  sinus  was  the  larger  in  70  cases, 
the  left  in  27,  and  the  two  were  equal  in  size  in  only  3  cases. 

The  horizontal  portion  of  the  left  sinus  has  been  observed  to  be  lacking  or  reduced  to  an 
exceedingly  fine  channel,  and  one  or  both  of  the  sinuses  have  been  observed  to  pass  through  a 
greatly  enlarged  mastoid  foramen  to  open  into  the  posterior  auricular  vein,  the  sigmoid  sinus 
being  represented  only  by  a  very  small  channel. 

In  a  considerable  number  of  cases  a  small  sinus,  known  as  the  petro-squamosal  sinus,  opens 
into  the  lateral  just  as  it  bends  downward  and  inward  upon  the  mastoid  portion  of  the  temporal. 
This  sinus  passes  downward  over  the  anterior  surface  of  the  petrous  portion  of  the  temporal, 
along  the  line  of  its  junction  with  the  squamous  portion,  and  occasionally  passes  through  a 
foramen — the  foramen  jugulare  spurium — which  opens  to  the  exterior  just  behind  the  articular 
eminence  of  the  zygomatic  process.  The  sinus  represents  the  original  terminal  portion  of  the 
lateral  sinus,  the  sigmoid  portion  of  that  sinus  being  a  secondary  formation,  and  opened  after 
its  exit  from  the  foramen  jugulare  spurium  into  the  internal  jugular,  although  its  connection  in  the 
adult  is  with  the  temporal  vein. 

Practical  Considerations. — By  reason  of  its  proximity  to  the  middle  ear, 
mastoid  antrum  and  cells,  the  sigmoid  portion  of  the  lateral  sinus  is  more  often  the 
subject  of  thrombosis  than  any  other  sinus  (page  1509).  This  may  arise  in  the 
following  six  ways,  mentioned  in  the  order  of  frequency,  the  first  outnumbering  all  the 
others  :  (1)  Extension  from  chronic  purulent  inflammation  of  the  middle  ear;  (2) 
extension  of  acute  inflammatory  disease  from  the  mouth,  pharynx,  and  tonsils  into 
the  middle  ear,  antrum,  and  cells  ;  (3)  extension  of  thrombosis  from  other  sinuses, 
especially  the  so  closely  associated  superior  petrosal  ;  (4)  trauma,  such  as  fracture  of 
the  base  extending  through  the  middle  ear  to  the  sinus  ;  (5)  pressure  of  tumors  or 
discharge  associated  with  them  ;  (6)  infection  from  septic  wounds  of  the  head,  neck, 
or  mastoid  region  (Macewen). 

The  anatomical  symptoms  of  thrombosis  of  this  sinus  may  be  due  to  (a)  obstruc- 
tive distension  of  the  superficial  veins  communicating  with  the  sinus,  chiefly  the 
mastoid  vein  (q.v.)  ;  (b)  mastoid  inflammation  (osteitis)  resulting  from  contiguity 
and  from  the  venous  connection  ;  (<?)  phlebitis  of  the  veins  communicating  with  the 
sinus,  especially  the  internal  jugular  (page  863),  condyloid  (page  876),  and,  occasion- 
ally, the  mastoid. 

The  subject  of  sigmoid  sinus  thrombosis  is  further  considered  in  relation  to  the 
mastoid  (page  1508). 

The  knee  (genu)  of  the  sigmoid  portion  of  the  lateral  sinus  extends  further 
inward  and  forward  on  the  right  side  than  on  the  left,  and  this  fact,  together  with  the 
larger  size  of  the  right  lateral  sinus  as  compared  with  the  left,  aids  in  explaining  the 
greater  frequency  of  sinus  thrombosis,  septic  meningitis,  and  cerebral  abscess  as 
sequelae  of  otitis  media  on  the  right  side  (page  1509).  The  infection  is  carried 
by  the  veins  which  connect  the  mastoid  cells  and  antrum  with  the  genu  of  the 
sigmoid  sinus. 

On  the  surface  the  top  of  the 'curve  represented  by  the  horizontal  and  descending 
(sigmoid)  portion  of  the  lateral  sinus  should  correspond  to  a  point  (asteric)  2.5  cm. 
above  and  3.8  cm.  {i]4  in.)  behind  the  centre  of  the  auditory  meatus.  This  is 
about  the  infero-posterior  parietal  angle.  The  superior  limit  of  the  horizontal  portion 
of  the  sinus  is  represented  by  a  line  from  this  asteric  point  to  3.8  cm.  (i)4  in.)  above 
the  inion.  The  superior  and  anterior  boundary  of  the  sigmoid  portion  is  indicated 
by  a  line  from  the  same  point  curving  downward  and  forward  along  the  skin 
groove  at  the  auriculo-mastoid  junction  to  a  little  below  the  level  of  the  external 


870  HUMAN    ANATOMY. 

auditory  meatus.  Here  the  sinus  turns  inward  and  forward  to  reach  the  jugular 
foramen  and  has  no  further  close  relation  to  the  lateral  cranial  wall.  A  curved  line 
drawn  12  mm.  (y2  in.)  below  the  horizontal  and  behind  the  vertical  portions  of  the 
curved  line  last  described  represents  approximately  the  inferior  and  posterior 
boundary  of  the  sinus.  The  width  thus  indicated — a  half  inch — varies  ;  it  is  usually 
greater  in  the  descending  part  of  the  sinus.  So,  too,  the  space  intervening 
between  the  genu  and  the  posterior  wall  of  the  external  auditory  meatus  may  vary 
from  2-12  mm. 

The  direction  of  the  sinuses  is  also  indicated  (Macewen)  by  a  line  from  the 
upper  edge  of  the  external  meatus  to  the  asterion,  and  by  one  from  the  tip  of  the 
mastoid  to  the  parieto-squamo-mastoid  junction,  the  latter  corresponding  to  the 
midportion  of  the  sinus,  or  that  most  often  involved  in  middle-ear  disease.  The 
region  of  danger  in  trephining  is  enclosed  (Birmingham)  by  two  lines,  one  from  a 
point  3.3  cm.  (1^  in.)  above  and  3.8  cm.  (1%  in.)  behind  the  centre  of  the 
external  auditory  meatus  to  a  point  12  mm.  (}4  in.)  above  the  inion  ;  the  other 
from  a  point  3.8  cm.  (i}4  in.)  behind  the  meatus  and  on  the  same  level  to  a  point 
12  mm.  (}4  in.)  below  the  inion.  The  sinus  almost  never  overpasses  these  limits 
in  either  a  downward  or  an  upward  direction,  and  hence  the  trephine  or  chisel  may 
be  safely  applied  either  below  or  above  these  lines. 

Fracture  of  the  base  of  the  skull  may  extend  into  the  lateral  sinus,  in  which 
case  the  blood  may  pass  outward  into  the  tympanum  and  thence  by  way  of  the  Eusta- 
chian tube  to  the  pharynx,  or — if  the  tympanic  membrane  is  torn — may  find  exit, 
mingled  with  cerebro-spinal  fluid,  at  the  external  auditory  meatus  (page  1505). 

For  further  remarks  on  the  practical  relations  of  this  important  sinus,  see 
page  1508. 

2.  The  Superior  Longitudinal  Sinus. — The  superior  longitudinal  sinus 
(sinus  sagittalis  superior)  (Fig.  756)  is  an  unpaired  sinus  which  lies  along  the  line  of 
attachment  of  the  falx  cerebri  to  the  cranial  vault.  It  begins  blindly  anteriorly  by  a 
small  vein-like  portion  which  lies  in  the  foramen  caecum  between  the  frontal  and 
ethmoidal  bones,  but  soon  becomes  a  true  sinus  which  passes  upward  and  backward  in 
the  median  line  of  the  frontal  bone,  beneath  the  sagittal  suture  of  the  parietals,  and  down 
the  median  line  of  the  squamous  portion  of  the  occipital  to  terminate  at  the  internal 
occipital  protuberance  by  opening  into  the  torcular  Herophili,  or,  usually,  more  or 
less  directly  into  the  right  lateral  sinus. 

The  sinus  is  triangular  in  section  and  increases  gradually  in  size  from  before  back- 
ward, measuring  about  1.5  mm.  in  diameter  at  the  level  of  the  apex  of  the  crista 
galli  and  1 1  mm.  at  its  termination.  Its  lumen  is  usually  traversed  by  numerous 
irregular  bands  of  connective  tissue  known  as  chordas  Willisii,  and  frequently,  espe- 
cially in  aged  persons,  Pacchionian  bodies,  which  are  numerous  along  its  course, 
project  into  it  (Fig.   1039). 

Tributaries. — In  the  foetus  and  in  early  childhood  the  superior  longitudinal  sinus  communi- 
cates with  the  veins  of  the  nasal  cavity  through  the  foramen  caecum,  but  this  connection  is  dissolved 
in  the  adult.  In  addition,  it  communicates  with  the  neighboring  blood-lakes  and  through  these 
with  the  meningeal  veins,  and  receives  (a)  branches  from  the  adjacent  portions  of  the  dura 
mater  ;  (b)  the  superior  cerebral  veins,  from  ten  to  fifteen  in  number  (page  877)  ;  and  (c)  diploic 
veins,  some  of  which  traverse  the  parietal  bone  and  constitute  emissary  veins,  the  most  noticeable 
of  these  being  one  which  traverses  the  parietal  foramen  (page  876). 

Variations. — The  superior  longitudinal  sinus  varies  considerably  in  size  and  is  occasionally 
exceedingly  small,  the  tributaries  which  normally  open  into  it  passing  downward  in  the  falx 
to  open  into  the  inferior  longitudinal  sinus.  It  has  been  observed  to  divide  into  two  trunks 
throughout  a  portion  of  its  course,  and  also  to  divide  at  the  apex  of  the  occipital  bone  into  two 
trunks  which  followed  the  lines  of  the  lambdoid  suture  to  open  into  the  lateral  sinuses.  Usually, 
as  stated,  the  sinus  communicates  more  or  less  directly  with  the  right  lateral  sinus,  but  occasion- 
ally it  may  bend  to  the  left  of  the  internal  occipital  protuberance  and  open  into  the  left  lateral. 

Practical  Considerations. — The  superior  longitudinal  sinus  may  become 
infected  (a)  from  the  scalp  through  the  diploic  veins  ;  (3)  from  foci  of  cerebral  or 
meningeal  disease  through  the  contiguous  blood-lakes  or  through  the  cerebral  veins  ; 
(c)  in  childhood  from  the  nose  through  the  veins  traversing  the  foramen  caecum. 


THE   SUPERIOR    CAVAL   SYSTEM. 


871 


When  the  latter  veins  are  patent  epistaxis  may  be  a  symptom  of  cerebral  hyperemia 
(as  in  congestive  headaches)  and  may  relieve  it.  In  children  epistaxis,  in  infants 
cedema  of  the  scalp  over  the  anterior  fontanelle,  and  in  adults  cedema  over  the  parie- 
tal and  occipital  regions  are  common  symptoms  of  thrombosis  of  this  sinus,  and  are 
easily  understood  in  view  of  its  venous  tributaries. 

Naevi  in  the  scalp  in  the  mid-line  sometimes  communicate  directly  with  the  sinus 
by  veins  passing  between  the  parietals  or  directly  through  them  near  the  medial  edge. 

Traumatic  or  inflammatory  thrombosis  may  follow  a  depressed  fracture  of  the 
cranial  vault  if  the  fragment  invades  the  lumen  of  the  sinus  and  obstructs  or  arrests 
the  flow  of  blood. 

A  noninfective  form  of  thrombosis  is  sometimes  observed  in  connection  with 
this  sinus.  It  has  received  the  name  of  marasmic  thrombosis,  as  it  has  usually  been 
associated  with  weakness  and  debility. 

The  construction  of  all  the  sinuses  predisposes  them  to  thrombosis.  Their 
rigidity,  their  width,  the  trabeculse  which  occasionally  cross  them,  the  peculiar 
manner  in  which  they  are  prevented  from  being  too  rapidly  depleted  during  inspira- 


Fig.  756. 


Superior  longitudinal  ■ 
Right  choroid  < 


Falx  cerebri 

Inferior  longitudinal  sinu 

In 


Right  superior  petrosal  Sim 
Internal  auditory  meatus 
Torcular  Herophili 
Lateral  superior  cerebellar 
Right  lateral  sinus 
Falx  cerebelli 


Head  has  been  sectioned  to  ISft  of  mid-sagittal  plane  and  brain  removed,  showing  dural  septa  in  position; 
terminal  portions  of  some  superior  cerebral  veins  are  seen  upon  the  surface  of  falx  cerebri. 

tion  when  the  lowering  of  pressure  takes  place  in  the  great  cervical  veins  (page  878), 
and,  in  the  case  of  the  longitudinal  sinus,  the  direction  in  which  the  blood  from  the 
cerebral  veins  enters  at  an  obtuse  or  right  angle  against  the  current,  all  tend  to  retard 
the  flow  of  blood  and  favor  coagulation.  When  to  these  conditions  is  added  a 
deficient  supply  of  possibly  defective  blood,  as  in  exhaustion  or  depletion  from  pro- 
fuse diarrhoea,  marasmic  thrombosis  is  apt  to  occur  (Macewen). 

The  line  of  the  sinus  begins  at  the  root  of  the  nose  and  runs  in  the  mid-line  to 
the  external  occipital  protuberance. 

Rarely  there  are  found  in  the  mid-line  of  the  vertex  small  reducible  swellings  to/ 
which  are  feebly  transmitted  the  brain  pulsations.  They  are  subpericranial,  contain 
venous  bloody  and  connect  with  the  longitudinal  sinus  through  apertures  in  the  skull, 
either  congenital,  the  result  of  bone  disease  or  atrophy,  or  due  to  accident. 

3.  The  Inferior  Longitudinal  Sinus.— The  inferior  longitudinal  sinus  (sinus 
sagittalis  inferior)  (Fig.  756)  is  an  unpaired  sinus  which  lies  in  the  inferior  or  free  edge 
of  the  falx  cerebri.      It  begins  at  about  the  middle  of  the  border  of  the  falx  and  passes 


/ 


872  HUMAN   ANATOMY. 

backward,  gradually  increasing  in  size,  to  the  junction  of  the  falx  with  the  tentorium 
cerebelli,  where  it  opens  into  the  straight  sinus.  It  receives  small  tributaries  from  the 
falx  and  sometimes  also  from  the  corpus  callosum. 

4.  The  Straight  Sinus. — The  straight  sinus  (sinus  rectus)  (Fig.  756),  also 
unpaired,  lies  along  the  line  of  junction  of  the  falx  cerebri  with  the  tentorium  cerebelli. 
It  is  formed  at  the  anterior  border  of  the  tentorium  by  the  junction  of  the  inferior  longi- 
tudinal sinus  and  the  great  cerebral  vein  (vena  Galeni)  (page  877),  and  is  directed 
backward  to  open  into  the  torcular  Herophili  or  more  usually  into  the  left  lateral 
sinus. 

In  addition  to  the  two  trunks  by  whose  union  it  is  formed,  it  receives  a  number 
of  small  branches  from  the  tentorium,  branches  from  the  posterior  portion  of  the 
medial  surfaces  of  the  cerebral  hemispheres,  and  sometimes  a  median  superior  cere- 
bellar vein. 

5.  The  Occipital  Sinus. — The  occipital  sinus  (sinus  occipitalis)  (Fig.  757)  is 
an  unpaired,  or  in  some  cases  a  paired,  sinus  which  descends  from  the  torcular  Herophili 
along  the  line  of  attachment  of  the  falx  cerebelli  to  the  posterior  border  of  the  foramen 
magnum.  There  it  divides  into  two  trunks,  the  marginal  sinuses,  which  pass 
forward  along  the  margin  of  the  foramen  magnum,  one  on  one  side  and  one  on 
the  other,  to  open  into  the  bulbus  superior  of  the  corresponding  internal  jugular 
vein. 

The  occipital  sinus  receives  as  tributaries  branches  from  the  falx  cerebelli  and 
the  adjacent  portions  of  the  dura,  and  also  some  veins  from  the  inferior  surface  of  the 
cerebellum.  At  the  posterior  border  of  the  foramen  magnum,  where  it  bifurcates  to 
form  the  marginal  sinuses,  it  makes  connection  with  the  veins  of  the  posterior  spinal 
plexus. 

Variations. — The  occipital  sinus  is  occasionally  wanting,  and  frequently  extends  only  as  far 
as  the  posterior  border  of  the  foramen  magnum,  the  marginal  sinuses  being  undeveloped.  It 
may  open  above  into  either  the  right  or  left  lateral  sinus,  or  into  the  straight  sinus  a  short 
distance  before  its  termination. 

6.  The  Cavernous  Sinus. — The  cavernous  sinus  (sinus  cavernosus)  (Fig.  757) 
is  a  paired  sinus  of  considerable  size  which  extends  along  the  sides  of  the  body  of  the 
sphenoid  bone  from  the  sphenoidal  fissure  in  front  to  the  apex  of  the  petrous  portion  of 
the  temporal.  It  measures  about  2  cm.  in  length  and  has  a  diameter  of  about  1  cm. 
and  is  almost  quadrilateral  in  cross-section.  Its  external  diameter  does  not,  however, 
represent  the  actual  capacity  of  its  lumen,  since  this  is  greatly  reduced  in  size  (1)  by 
being  traversed  by  numerous  trabeculas  from  which  fringe-like  prolongations  hang 
freely  into  the  blood-current,  a  section  of  the  sinus  having  very  much  the  appearance 
of  a  section  of  the  corpus  cavernosum  penis,  whence  the  name  bestowed  upon  it  by 
Winslow  ;  and  (2)  by  the  fact  that  the  internal  carotid  artery  and  the  abducent 
(sixth)  nerve  traverse  it,  while  certain  other  of  the  cranial  nerves  are  embedded  in  its 
outer  wall.  These  nerves  are  the  oculomotor,  the  pathetic,  and  the  ophthalmic  and 
maxillary  divisions  of  the  trigeminus,  which  lie  in  that  order  from  above  downward. 

Tributaries. — At  the  sphenoidal  fissure  the  cavernous  sinus  receives  the  ophthalmic  vein 
and,  farther  back,  occasionally  the  basilar  vein,  both  of  which  are  described  later  on  (page  877). 
In  addition,  it  receives  veins  from  the  neighboring  portions  of  the  dura  mater,  and  has  connecting 
with  it  the  spheno-parietal  and  the  intercavernous  sinuses.  These  latter  are  transverse  sinuses 
which  pass  across  between  the  two  cavernous  sinuses,  the  one  (sinus  intercavernosus  anterior) 
passing  in  front  of  the  sella  turcica  and  the  other  (sinus  intercavernosus  posterior)  behind  that 
i  cavity,  and  they  receive  branches  from  the  dura  mater  and  from  the  pituitary  body.  The  two 
sinuses,  together  with  the  portion  of  the  cavernous  sinus  between  their  terminations  on  each  side, 
}orm  what  is  usually  termed  the  circular  sinus  (sinus  circularis). 

Besides  the  vessels  which  are  truly  tributaries,  the  cavernous  sinus  also  has  connected 
with  it  certain  vessels  which  are  emissary  in  function,  leading  blood  away  from  it.  The  two 
petrosal  sinuses  in  which  it  terminates  are  of  this  nature.  In  addition,  veins  pass  from  its  under 
surface  (1)  through  the  foramen  ovale,  along  with  the  mandibular  division  of  the  trigeminal 
nerve,  to  communicate  with  the  pterygoid  plexus  ;  (2)  through  the  fibrous  tissue  which  closes 
the  foramen  lacerum  medium  ;  (3)  through  the  foramen  of  Vesalius,  when  this  exists  ;  and  (4) 
occasionally  through  the  foramen  rotundum  with  the  maxillary  division  of  the  trigeminal  nerve. 


THE   SUPERIOR   CAVAL  SYSTEM. 


873 


Where  the  internal  carotid  enters  the  cavernous  sinus  at  the  internal  orifice  of  the  carotid 
canal  the  sinus  projects  downward  around  the  artery  in  a  funnel-shaped  manner,  and  from  it 
there  arises  a  close  net-work  of  veins,  the  carotid  plexus  or  carotid  sinus,  which  completely 
invests  the  artery  throughout  its  course  through  the  carotid  canal,  at  the  lower  opening  of 
which  it  is  continued  into  one  or  two  veins  which  open  into  the  internal  jugular. 


Practical  Considerations. — The  cavernous  sinus,  though  less  frequently 
affected  with  thrombosis  than  any  other  large  sinus,  may  become  infected  from 
foci  apparently  far  removed,  through  the  extra-orbital  communications  of  the 
ophthalmic  veins  (pages  879,  880).  Thus,  carbuncle  of  the  face,  cancrum 
oris,  alveolo-dental  periostitis,  ulceration  of  the  Schneiderian  mucous  membrane, 
empyema  of   the  maxillary  antrum,   abscess  of   the  frontal   sinus,   osteomyelitis  of 

Fig.  757. 


Eyeball 
Superior 

ophthalmic  vein 
Inferior 

ophthalmic  vein 

Optic  nerve 
Ophthal 
Anterio 


clii 


id  process 


petrosal  sinus 
Superior  petros; 

Lateral  sinus 
Inferior 

cerebral  * 


Lateral  sinus- 


Optic  nerve 

Circular  sinus 
Cavernous  sinus 

Basilar  sinus 

Inferior 

petrosal  sinus 

Superior 

petrosal  sinus 

Foramen  magnum 
Tentorium  cerebelli 

Inferior  cerebral  vein 

Inferior  longitudinal 

section 

Lateral  sinus. 


Dural  sinuses  at  base  of  skull ;  falx  cerebri  and  left  half  of  tentorium  ha 


the  frontal  diploic  tissue,  may  each  be  followed  by  cavernous  sinus  thrombosis. 
In  the  presence  of  thrombosis,  there  are  two  groups  of  pressure  symptoms  (a) 
venous,  causing  exophthalmos,  oedema  of  the  eyelids  and  of  the  corresponding  side 
of  the  root  of  the  nose,  and  some  chemosis  ;  (&)  nervous,  causing  ptosis,  strabismus, 
variations  in  the  pupil,  pain,  etc. 

_  Arterio-venous  aneurism  between  this  sinus  and  the  internal  carotid,  in  addition 
to  similar  symptoms  of  venous  obstruction  (page  863),  often  likewise  causes  paralyses 
in  the  distribution  of  the  third,  the  fourth,  and  the  ophthalmic  division  of  the  fifth 
cranial  nerves,  which  lie  in  the  dura  mater  on  the  outer  wall  of  the  sinus,  and  of  the 
sixth  nerve,  which  is  in  close  relation  to  the  internal  carotid. 

The  bulk  of  the  blood  of  the  contents  of  the  anterior  and  lower  portions  of  the 
skull  empties  into  the  cavernous  sinus;  that  of  the  remaining  portion,— including  the 
greater  part  of  the  cerebrum,  the  cerebellum,  the  pons,  and  the  cerebral  peduncles 


S74  HUMAN    ANATOMY. 

— chiefly  into  the  tributaries  of  the  lateral  sinus.  The  two  sinuses  through  the 
superior  petrosal  sinus  and  other  venous  channels,  have  free  anastomotic  connection 
which  effectually  tends  to  equalize  or  distribute  blood-pressure. 

The  communication  between  the  two  cavernous  sinuses  through  the  basilar  sinus 
— or  plexus — and  the  circular  sinus,  is  an  important  portion  of  the  mechanism  by 
which  the  pressure  of  venous  blood  within  the  skull  is  equalized.  This  same  com- 
munication may,  however,  in  a  case  of  anterio-venous  aneurism  {vide  supra)  bring 
about  involvement  of  the  orbit  on  the  other  side,  the  blood  from  the  aneurism  entering 
the  opposite  sinus  by  way  of  these  intercommunicating  sinuses,  or  infection  may 
follow  the  same  channel. 

7.  The  Spheno-Parietal  Sinus. — The  spheno-parietal  sinus  (sinus  spheno- 
parietalis),  also  known  from  its  position  as  the  sinus  al<z  parvce,  arises  at  the  outer 
extremity  of  the  lesser  wing  of  the  sphenoid  from  one  of  the  meningeal  veins  and 
passes  horizontally  inward,  under  cover  of  the  posterior  border  of  the  lesser  wing,  to 
reach  the  cavernous  sinus  near  its  anterior  extremity.  It  receives  dural,  diploic,  and 
some  of  the  anterior  cerebral  veins. 

8.  The  Superior  Petrosal  Sinus. — The  superior  petrosal  sinus  (sinus  petrosus 
superior)  is  the  smaller  of  the  two  sinuses  into  which  the  cavernous  divides  at  the 
apex  of  the  petrous  portion  of  the  temporal.  It  passes  outward  and  backward  along 
the  superior  border  of  the  petrous  bone  and  opens  into  the  lateral  sinus  just  at  the 
point  where  it  leaves  the  line  of  attachment  of  the  tentorium  cerebelli  to  become  the 
sigmoid  sinus.  The  superior  petrosal  sinuses  receive  some  small  tympanic  veins  and 
some  branches  from  the  cerebellum  and  cerebrum. 

9.  The  Inferior  Petrosal  Sinus. — The  inferior  petrosal  sinus  (sinus  petrosus 
inferior)  is  the  larger  terminal  branch  of  the  cavernous  sinus,  and  extends  from  the 
posterior  extremity  of  that  sinus,  at  the  apex  of  the  petrous  portion  of  the  temporal 
bone,  along  the  petro-occipital  suture  to  the  jugular  foramen,  where  it  opens  into  the 
superior  bulb  of  the  jugular  vein,  or,  frequently,  into  the  vein  below  the  bulb. 

In  addition  to  small  branches  from  the  neighboring  portions  of  the  dura  and 
from  the  cerebellum,  pons,  and  medulla  oblongata,  the  inferior  petrosal  sinus 
receives  some  internal  auditory  veins  and  an  anterior  co?idyloid  vein  which  arises 
from  a  plexus  surrounding  the  hypoglossal  nerve  in  its  course  through  the  anterior 
condyloid  foramen.  In  its  anterior  portion  the  sinus  is  also  in  communication  with 
the  basilar  sinus. 

10.  The  Basilar  Sinus. — The  basilar  sinus  (plexus  basilaris),  also  termed  the 
transverse  sinus,  is  usually  a  plexus  of  sinuses  rather  than  a  single,  distinct  sinus. 
It  occupies  the  dura  mater  which  covers  the  basilar  process  of  the  occipital 
bone  and  communicates  with  the  inferior  petrosal  and  posterior  intercavernous 
sinuses  in  front,  and  behind,  at  the  anterior  border  of  the  foramen  magnum,  with 
the  anterior  spinal  plexus.  It  receives  branches  from  the  medulla  oblongata  and 
from  the  diploe. 

Practical  Considerations. — Fracture  of  the  base  of  the  skull  through  the 
posterior  (cerebellar)  fossa  may  involve  the  basilar  plexus  of  sinuses  and  be  followed 
by  an  intracranial  hemorrhage  which  slowly  oozes  through  the  line  of  fracture  and, 
following  the  lines  of  vessels  or  nerves,  ultimately  causes  swelling  and  ecchymosis  of 
the  skin  of  the  neck  ;  the  latter  is  apt  to  show  first  anterior  to  the  tip  of  the  mastoid, 
to  which  region  the  blood  is  conducted  by  the  cellular  tissue  around  the  auricular 
artery.      It  spreads  thence  upward  and  backward  in  a  curved  line. 

The  Diploic  Veins. 

The  spaces  of  the  diploe  are  traversed  by  a  rich  plexus  of  veins,  characterized 
by  the  thinness  of  their  walls  and  opening  by  numerous  small  communicating 
branches  either  into  the  veins  of  the  scalp,  the  middle  meningeal  veins,  or  the 
crania;  sinuses.  Some  larger,  although  rather  inconstant,  stems  also  arise  from  the 
plexus  and  form  what  are  termed  the  diploic  veins.  Of  these,  four  are  usually 
recognized  (Fig.  758). 


THE    SUPERIOR    CAVAL   SYSTEM. 


875 


1.  The  anterior  diploic  vein  (v.  diploica  frontalis)  descends  in  the  diploe  of  the  frontal  bone 
and  at  the  level  of  the  supra-orbital  notch  opens  either  into  the  supra-orbital  or  ophthalmic  vein. 
It  communicates  with  the  anterior  temporal  diploic  vein  and  also  with  the  frontal  veins  and  the 
superior  longitudinal  sinus. 

2.  The  anterior  temporal  diploic  vein  (v.  diploica  temporalis  anterior)  passes  downward  and 
forward  in  the  diploe  of  the  anterior  portion  of  the  parietal  bone  and  opens  either  into  a  deep 
temporal  vein  or  into  the  spheno-parietal  sinus. 

3.  The  posterior  temporal  diploic  vein  (v.  diploica  temporalis  posterior)  passes  downward  in 
the  diploe  of  the  posterior  part  of  the  parietal  bone  and  usually  opens  into  the  mastoid  emissary 
vein,  thus  communicating  with  the  lateral  sinus.  It  also  communicates  with  the  posterior  auric- 
ular vein  and  may  open  into  it. 

4.  The  occipital  diploic  vein  (v.  diploica  occipitalis)  passes  downward  in  the  squamous  portion 
of  the  occipital  bone,  not  far  from  the  median  line,  and  opens  either  into  the  occipital  vein  or  into  the 
occipital  emissary  vein,  by  which  it  communicates  with  the  torcular  Herophili  or  the  lateral  sinus. 

Fig.  75S. 


Outer  table  of  skull  has  been  removed  to  expose  venous  spaces  of  diploe. 


Practical  Considerations.— The  diploic  veins  being  incapable  of  effective 
contraction,  bleed  very  freely  and  persistently,  and  are  sometimes  a  source  of 
embarrassment  during  operations  on  the  skull.  Through  their  communications 
with  the  veins  of  the  scalp  on  the  one  hand,  and  with  the  endo-cranial  sinuses 
and  meningeal  veins  on  the  other,  they  may,  as  in  some  cases  of  compound  fracture, 
convey  infection  from  the  surface  to  the  diploe,  causing  osteomyelitis  and  necrosis, 
or  within  the  cranium,  causing  septic  meningitis  or  sinus  thrombosis.  Pyaemia 
has  followed  an  infective  phlebitis  of  the  diploic  veins  themselves.  Diploic  infection 
introduced  from  without — pyogenic — or  through  the  blood — tuberculous — is  apt 
to  spread  rapidly  within  the  diploic  tissue  itself,  as  well  as  to  the  underlying 
structures. 

The  Emissary  Veins. 

The  term  emissary  vein  is  applied  to  those  branches  which  place  the  sinuses  of 
the  dura  mater  in  communication  with  veins  external  to  the  cranial  cavity.  Using 
the  term  in  its  broadest  sense,  the  emissary  veins  are  very  numerous,  since  bothi  the 
diploic  and  the  meningeal  veins  might  be  regarded  as  such,  as  well  as  the  carotid 


876  HUMAN   ANATOMY. 

plexus  (page  873)  and  the  ophthalmic  vein  (page  879),  all  these  making  connections 
with  the  sinuses,  on  the  one  hand,  and  with  extracranial  veins,  on  the  other.  It  is 
customary,  however,  to  limit  the  term  to  certain  veins  which,  for  the  most  part, 
traverse  special  foramina  in  the  cranial  walls,  a  few,  however,  passing  through 
foramina  whose  principal  content  is  one  of  the  cranial  nerves. 

1.  The  parietal  emissary  vein  (emissarium  parietale),  rather  variable  in  size,  traverses  the  cor- 
respondingly variable  parietal  foramen,  placing  the  superior  longitudinal  sinus  in  communication 
with  the  veins  of  the  scalp. 

2.  The  occipital  emissary  vein  (emissarium  occipitale)  traverses  the  occipital  protuberance 
and  places  the  torcular  Herophili  or  one  or  the  other  of  the  lateral  sinuses  in  communication  with 
the  occipital  veins.  Its  size  is  variable  ;  it  usually  receives  the  occipital  diploic  vein,  and  may 
perforate  only  the  external  or  the  internal  table  of  the  occipital  bone,  representing  in  such  cases 
the  terminal  portion  of  the  diploic  vein  rather  than  a  true  emissary. 

3.  The  mastoid  emissary  vein  (emissarium  mastoideum )  passes  through  the  mastoid  foramen 
and  places  the  lateral  sinus  in  communication  with  either  the  occipital  or  the  posterior  auricular 
veins.  It  is  occasionally  wanting,  and,  on  the.  other  hand,  may  be  so  large  as  to  appear  to  be 
the  continuation  of  the  lateral  sinus,  the  terminal  portion  of  that  vessel  between  the  mastoid  and 
jugular  foramina  being  greatly  reduced  in  size. 

4.  The  posterior  condyloid  emissary  vein  (emissarium  condyloideum)  is  very  inconstant,  and 
when  present  traverses  the  posterior  condyloid  foramen,  extending  between  the  lateral  sinus  near 
its  termination  and  the  vertebral  veins. 

5.  The  anterior  condyloid  emissary  vein  (retecanalis  hypoglossi)  is  a  net-work  which  sur- 
rounds the  hypoglossal  nerve  in  its  course  through  the  anterior  condyloid  foramen.  From  the 
plexus  two  veins  arise,  one  of  which  passes  to  the  inferior  petrosal  sinus  and  the  other  to  the 
vertebral  veins. 

6.  The  emissaries  of  the  foramen  ovale  (  rete  foraminisovalis)  are  formed  by  two  veins  which 
communicate  above  with  the  cavernous  sinus  and  pass  to  the  foramen  ovale,  where  they  form  a 
plexus  surrounding  the  mandibular  division  of  the  trigeminal  nerve  and  communicate  with  the 
pterygoid  plexus  of  veins.  Occasionally,  also,  a  similar  plexus  accompanies  the  maxillary  division 
of  the  trigeminus  through  the  foramen  rotundum, 

7.  The  emissary  vein  of  the  foramen  of  Vesalius  is,  like  the  foramen,  inconstant,  occurring 
only  about  once  in  three  cases.  It  extends  between  the  cavernous  sinus  and  the  pterygoid 
plexus  of  veins. 

8.  Finally,  a  variable  number  of  small  veins  pass  through  the  connective  tissue  which 
closes  the  foramen  lacerum  medium  and  place  the  cavernous  sinus  in  communication  with  the 
pterygoid  plexus. 

Practical  Considerations. — The  relations  of  the  emissary  veins  explain  many 
cases  of  spread  of  extra-cranial  infection  to  the  meninges  and  the  sinuses.  If  there 
were  no  emissary  veins,  injuries  and  diseases  of  the  scalp  and  skull  would  lose 
half  their  seriousness  (Treves).  Infected  wounds  of  the  scalp,  cellulitis  or  erysipelas 
involving  that  structure,  osteomyelitis,  or  necrosis  of  the  cranial  bones  may  through 
the  emissary  veins  result  in  serious  intra- cranial  disease.  The  largest  of  these  veins 
is  usually  the  mastoid,  the  communication  between  the  lateral  sinus  and  the  occipital 
or  posterior  auricular  vein  {vide  supra).  ■  This  relation  and  the  considerable  quan- 
tity of  blood  carried  by  the  mastoid  vein  are  thought  to  explain  the  supposed  effect 
of  leeches  or  blisters  applied  behind  the  ear  in  cerebral  hyperemia  or  inflammation, 
especially  as  nearly  all  the  blood  of  the  brain  leaves  it  through  the  lateral  sinuses. 
They  also  explain  the  extensive  cedema  behind  the  ear  and  around  the  mastoid 
region  often  seen  in  lateral  sinus  thrombosis.  Pus  has  formed  in  the  cerebellar 
fossa  outside  of  the  sigmoid  sinus,  made  its  exit  through  the  mastoid  foramen  and 
appeared  as  an  occipitocervical  abscess  (Erichsen).  The  escape  of  pus  by  the 
mastoid  foramen  indicates  extradural  pus  in  the  cerebellar  fossa  about  the  sigmoid 
groove,  with  the  probability  that  sigmoid  sinus  thrombosis  exists,  especially  if  the 
mastoid  vein  is  itself  thrombosed  (Macewen). 

In  suppurative  sigmoid  sinus  disease  the  posterior  condyloid  vein  may  convey 
infection  to  the  cellular  tissue  in  the  upper  part  of  the  posterior  cervical  triangle, 
causing  abscess  beneath  the  deep  fascia  ;  or,  as  a  result  of  cerebellar  pachymen- 
ingitis, there  may  be  phlebitis  of  this  vein,  with  marked  tenderness  in  the  same 
region.  The  emissary  veins  are  important  agents  in  the  equalization  of  intra-cranial 
pressure. 


THE   SUPERIOR   CAVAL  SYSTEM.  877 

The  Cerebral  Veins. 

The  cerebral  veins  (vv.  cerebri)  convey  the  blood  carried  to  the  brain  by 
the  cerebral  arteries  to  the  sinuses  of  the  dura  mater.  They  differ  from  most 
of  the  other  veins  in  that  they  contain  no  valves,  their  walls  are  very  thin  and 
destitute  of  muscle-tissue,  and  their  arrangement  does  not  usually  follow  that  of  the 
arteries. 

1.  The  Superior  Cerebral  Veins. — The  superior  cerebral  veins  (vv.  cerebri 
superiores)  are  from  eight  to  twelve  in  number,  draining  the  upper,  lateral  and  medial 
surfaces  of  the  cerebral  hemispheres.  They  follow,  for  the  most  part,. the  sulci  of  the 
hemispheres,  although  connected  across  the  gyri  by  numerous  anastomoses,  and  they 
open  above  into  the  superior  longitudinal  sinus.  The  various  veins  show  a  tendency 
to  increase  in  size  from  before  backward,  and  while  the  anterior  ones  have  a  course 
almost  at  right  angles  to  the  superior  longitudinal  sinus,  the  more  posterior  ones  are 
directed  forward  as  well  as  upward  and  open  obliquely  into  the  sinus  and  in  a  direc- 
tion contrary  to  the  flow  of  the  blood  contained  within  it. 

2.  The  Middle  Cerebral  Vein. — The  middle  cerebral  vein  (v.  cerebri  media), 
also  termed  the  superficial  Sylvian  vein,  lies  superficially  along  the  line  of  the  Sylvian 
fissure  and  opens  below  into  either  the  cavernous  or  the  spheno-parietal  sinus.  It 
receives  affluents  from  the  surface  of  the  brain  on  either  side  of  the  fissure  and  through 
these  anastomoses  with  both  the  superior  and  inferior  cerebral  veins.  One  of  these 
affluents  which  lies  approximately  along  the  line  of  the  fissure  of  Rolando  is  usually 
of  large  size  and  communicates  directly  with  one  of  the  superior  cerebral  veins,  the 
two  forming  what  is  known  as  the  great  anastomotic  vein  of  Trolard,  uniting  the 
superior  longitudinal  sinus  with  the  median  cerebral  vein. 

3.  The  Inferior  Cerebral  Veins. — The  inferior  cerebral  veins  (w.  cerebri 
inferiores)  are  a  number  of  small  veins  which  occupy  the  inferior  surfaces  of  the  hemi- 
spheres. They  are  somewhat  irregular  in  their  arrangement,  those  of  the  frontal 
lobes  anastomosing  with  the  superior  cerebrals  and  opening  into  the  anterior  portion 
of  the  superior  longitudinal  sinus,  while  those  of  the  temporo-sphenoidal  region 
anastomose  with  the  middle  cerebral  and  open  into  the  spheno-parietal,  cavernous  and 
superior  petrosal  sinuses  and  into  the  basilar  vein. 

4.  The  Great  Cerebral  Vein. — The  great  cerebral  vein  (v.  cerebri  magna), 
also  known  as  the  great  vein  of  Galen,  is  a  short  stem  about  1  cm.  in  length  which 
is  formed  beneath  the  splenium  of  the  corpus  callosum  in  the  neighborhood  of  the 
pineal  body,  by  the  union  of  the  two  internal  cerebral  veins.  It  passes  backward 
and  upward,  curving  around  the  posterior  extremity  of  the  corpus  callosum,  and 
terminates  (Fig.  756)  by  opening  into  the  anterior  end  of  the  straight  sinus. 

Tributaries. — The  great  cerebral  vein  is  formed  by  the  union  of  the  two  {a)  internal  cerebral 
veins  (vv.  cerebri  interna?),  also  known  as  the  small  veins  of  Galen.  These  are  situated,  one  on 
either  side  of  the  median  line,  in  the  velum  interpositum,  which  forms  the  roof  of  the  third 
ventricle.  Each  is  formed  at  the  foramen  of  Monro  by  the  union  of  three  veins,  the  choroid  vein, 
the  vein  of  the  septum  lucidum,  and  the  vein  of  the  corpus  striatum.  The  choroid  vein  ( v.  chori- 
oidea )  seems  to  be  the  direct  continuation  of  the  internal  cerebral  vein.  It  begins  at  the  junc- 
tion of  the  body  and  descending  horn  of  the  lateral  ventricle,  passes  forward  along  the  floor  of 
the  ventricle  in  the  outer  edge  of  the  choroid  plexus,  and  opens  at  the  foramen  of  Monro  into  the 
internal  cerebral  vein  of  its  side.  The  vein  of  the  septum  lucidum  (v.  septi  pellucidi)  passes 
backward  along  the  outer  (ventricular)  surface  of  the  septum  lucidum,  returning  the  blood  from 
the  head  of  the  caudate  nucleus  and  neighboring  parts,  and  the  vein  of  the  corpus  striatum  (v. 
terminalis),  which  drains  the  lenticular  nucleus  and  to  a  certain  extent  the  caudate  nucleus  also, 
passes  backward  in  the  groove  between  the  corpus  striatum  and  the  optic  thalamus  (stria  termi- 
nalis). 

(b)  The  posterior  vein  of  the  corpus  callosum  passes  backward  from  about  the  middle  of 
the  superior  surface  of  the  corpus  callosum  and,  bending  around  the  splenium,  empties  into  the 
great  cerebral  vein  or  into  the  internal  cerebral  vein  near  its  termination.  It  receives  blood 
from  the  corpus  callosum  and  from  the  median  surface  of  the  hemisphere. 

(c)  The  basilar  vein  (v.  basalis)  is  a  large  paired  vein  which  arises  at  the  anterior  per- 
forated space  by  the  junction  of  the  deep  Sylvian  vein  with  the  anterior  vein  of  the  corpus  cal- 
losum. It  passes  backward  over  the  optic  tract  of  its  side  and  then  curves  upward  around  the 
crus  cerebri  to  reach  the  dorsal  surface  of  the  brain-stem,  where  it  opens  into  either  the  great  or 
the  internal  cerebral  vein.     Occasionally  the  terminal  portion  which  bends  upward  around  the 


878  HUMAN   ANATOMY. 

crus  is  lacking,  the  vein  then  emptying  into  the  cavernous  sinus.  The  deep  Sylvian  vein,  which 
is  its  main  stem  of  origin,  begins  in  a  number  of  vessels  which  ramify  over  the  surface  of  the 
insula  (island  of  Reil)  and  passes  downward  and  forward  at  the  bottom  of  the  Sylvian  fissure  to 
become  continuous  with  the  basilar  at  the  anterior  perforated  space.  Occasionally  it  unites 
with  the  lower  portion  of  the  middle  cerebral  vein  or  opens  with  it  into  the  spheno-parietal 
sinus.  The  anterior  vein  of  the  corpus  callosum  corresponds  to  the  anterior  cerebellar  artery, 
sometimes  termed  the  anterior  central  vein  ;  it  arises  on  the  anterior  part  of  the  upper  surface 
of  the  corpus  callosum  and  bends  downward  around  the  genu  to  unite  with  the  deep  Sylvian 
vein  at  the  anterior  perforated  space. 

The  basilar,  vein  drains  all  the  central  part  of  the  base  of  the  brain,  and,  in  addition  to  the 
two  veins  which  are  regarded  as  its  stems  of  origin,  it  receives  branches  from  the  optic  tract, 
the  olfactory  bulb,  the  anterior  perforated  space,  the  tuber  cinereum,  the  corpora  mammillaria, 
and  the  posterior  perforated  space,  and  it  furthermore  receives  a  vein  from  the  superior  vermis 
of  the  cerebellum.  The  veins  of  the  anterior  perforated  space  are  from  ten  to  fifteen  in  number 
and  have  their  origin  in  the  nuclei  of  the  corpus  striatum  and  in  the  internal  capsule,  while  those 
of  the  posterior  perforated  space  drain  the  optic  thalami. 

Practical  Considerations. — The  free  communication  of  the  thin-walled 
valveless  cerebral  veins  with  one  another  is  one  of  the  agents  for  the  equalization  of 
intracranial  venous  pressure.  An  anastomotic  trunk  unites  the  middle  cerebral  vein 
with  the  posterior  cerebral,  thus  permitting  the  passage  of  venous  blood  by  means 
of  the  anterior  basilar  vein  into  the  sinuses  about  the  foramen  magnum.  Relief  from 
excessive  intracranial  blood-pressure  may,  in  addition,  be  effected  by  the  escape  of 
blood  from  within  the  cranium  (a)  in  the  occipital  region  through  the  internal 
jugular  and  mastoid  vein  ;  (d)  in  the  frontal  region  through  the  ophthalmic  vein 
and  the  vein  traversing  the  foramen  ovale  ;  (c)  in  the  basal  region  through  the 
petrosal  sinuses  and  the  posterior  condyloid  vein  ;  and  (af)  at  the  vertex  through  the 
diploic  veins  and  the  venules  penetrating  the  outer  table  of  the  cranium  to  join  those 
of  the  scalp  (Allen). 

The  avoidance  of  sudden  depletion  of  the  intracranial  venous  channels  through 
the  inspiratory  emptying  of  the  large  extracranial  veins  is  admirably  provided  for 
and  the  mechanism  should  be  understood,  as  it  has  practical  relation  to  many  phe- 
nomena of  cerebral  anaemia  and  hyperaemia,  to  shock  and  syncope  and  concussion, 
to  sinus  thrombosis,  and  to  many  other  intracranial  conditions.  The  chief  factors 
in  equalizing  the  flow  in  the  sinuses — and  thus  practically  throughout  the  brain — 
may  be  briefly  summarized  as  follows  : 

(a)  The  oblique  entrance  into  the  longitudinal  sinus  of  its  tributaries — the 
larger  middle  and  posterior  cerebral  veins — pouring  their  blood  into  it  against  the 
stream  ;  (b)  the  division  of  the  sinus  at  the  Torcular  Herophili  into  two  trunks 
diverging  at  right  angles  ;  (c)  the  course  of  the  blood-current  in  the  lateral  sinus — 
first  horizontal,  with  a  convexity  outward  ;  then — in  the  first  part  of  the  sigmoid — 
vertical  ;  then  horizontal,  with  a  convexity  downward,  and  then  a  quick  upward  and 
outward  turn,  with  narrowing  of  its  calibre  before  entering  the  jugular  fossa  ;  (d ) 
the  widening  of  the  upper  part  of  this  fossa — which  is  above  the  outlet  of  the  sig- 
moid— and  the  narrowing  of  its  exit  (Macewen).  Were  it  not  for  these  and  other 
subsidiary  anatomical  arrangements  contributing  to  the  same  end,  the  effect  of  a 
deep  inspiration  on  the  cervical  veins  (page  863)  would  be  so  to  aspirate  the  venous 
channels  of  the  brain  as  to  cause  faintness  or  momentary  unconsciousness. 

The  cerebral  veins  are  so  delicate  that  in  operations  upon  the  brain  it  is  often 
better  to  arrest  bleeding  by  gauze-pressure  than  to  attempt  to  seize  and  tie  separate 
vessels. 

5.  The  Cerebellar  Veins. — The  cerebellar  veins  form  a  net-work  over  the 
surface  of  the  cerebellum,  the  course  of  the  larger  stems  being,  for  the  most  part,  at 
right  angles  to  that  of  the  foliae. 

The  superior  cerebellar  veins  (vv.  cerebelli  superiores)  open  in  part  laterally 
into  the  lateral  and  superior  petrosal  sinuses,  while  others  pass  medially  and  unite  to 
form  a  superior  median  cerebellar  vein,  which  passes  forward  and  downward  along 
the  superior  vermis  and  opens  either  into  the  great  cerebral  vein  or  the  terminal 
portion  of  the  basilar  vein. 


THE    SUPERIOR    CAVAL   SYSTEM.  879 

The  inferior  cerebellar  veins  (vv.  cerebelli  inferiores),  somewhat  larger  than 
the  superior,  pass  in  part  forward  and  outward  to  open  into  the  lateral  or  superior 
petrosal  sinuses,  and  in  part  backward  to  unite  with  the  occipital  sinus. 

The  Ophthalmic  Veins. 

The  ophthalmic  veins  take  their  origin  from  the  contents  of  the  orbit  and  pass  from 
before  backward,  uniting  to  form  two  principal  trunks,  a  large  superior  and  a  smaller 
inferior  ophthalmic  vein,  which  open  at  the  sphenoidal  fissure  into  the  anterior 
extremity  of  the  cavernous  sinus.  At  the  margin  of  the  orbit  both  veins  form 
important  connections  with  the  angular  vein,  and,  since  no  valves  occur  in  any  of 
the  branches  of  the  ophthalmic  veins,  they  form  important  emissaries  connecting 
the  cavernous  sinus  with  the  facial  vein. 

1.  The  Superior  Ophthalmic  Vein. — The  superior  ophthalmic  vein  (v.  opta- 
thalmica  superior)  (Fig.  757)  is  formed  at  the  inner  angle  of  the  orbit  by  the  fusion  of 
usually  two  vessels  which  come  from  the  supra-orbital  and  angular  veins  and  pass 
respectively  above  and  below  the  pulley  of  the  superior  oblique  muscle  of  the  eye 
and  unite  a  short  distance  posterior  to  that  structure.  The  anterior  portion  of  the 
superior  ophthalmic  vein  so  formed  is  sometimes  termed  the  v.  naso-frontalis,  and  in 
its  further  course  it  is  directed  somewhat  tortuously,  at  first  obliquely  backward  and 
outward,  passing  across  the  optic  nerve  and  beneath  the  superior  rectus  muscle, 
and  then  more   directly  backward  to  the  sphenoidal  fissure. 

Tributaries. — The  superior  ophthalmic  receives  numerous  tributaries  from  both  the  eyeball 
and  the  other  contents  of  the  orbit,  most  of  the  branches  from  the  latter  sources  corresponding 
to  branches  of  the  ophthalmic  artery.  Thus  it  receives  {a)  the  anterior  and  (b)  the  posterior 
ethmoidal  veins  (  vv.  ethmoidals  anterior  et  posterior)  which  return  blood  from  the  sphenoidal 
sinus  and  the  superior  meatus  and  turbinate  bone  of  the  nose,  communicating  with  the  other 
veins  of  the  nasal  cavity  and  entering  the  orbit  by  the  ethmoidal  foramina  ;  (c)  the  lachrymal 
vein  (v.  lacrimalis),  a  vein  of  considerable  size  arising  in  the  lachrymal  gland  and  accompanying 
the  artery  of  the  same  name  ;  and  (d)  muscular  veins  (vv.  musculares)  which  return  the  blood 
from  the  levator  palpebrae  superioris,  the  superior  and  internal  recti,  and  the  superior  oblique,  the 
veins  from  the  other  muscles  of  the  orbit  usually  opening  into  the  inferior  ophthalmic  vein. 

From  the  eyeball  it  receives  {e)  the. two  superior  venae  vorticosae.  These  veins  return  the 
blood  from  the  choroid  coat,  the  ciliary  body,  and  the  iris,  and  are  four  in  number,  each  having 
its  origin  from  a  rich  plexus  which  occupies  one  of  the  four  quadrants  of  the  choroid,  the  prin- 
cipal stems  of  the  plexus  radiating  from  all  directions  towards  the  central  point  of  its  quadrant. 
Here  they  unite  to  form  a  single  trunk  which  pierces  the  sclera  obliquely  at  about  the  equator 
of  the  eyeball,  the  veins  from  the  two  superior  quadrants  emptying  into  the  superior  ophthalmic, 
while  the  two  from  the  inferior  quadrants  connect  with  the  inferior  ophthalmic.  Occasionally 
five  or  six  vena  vorticosae  exist,  and  they  open  sometimes  into  the  muscular  veins  instead  of 
directly  into  the  ophthalmic  stems.  (/)  The  anterior  ciliary  veins  (vv.  ciliares  anteriores)  are 
very  slender  veins  which  leave  the  eyeball  at  the  points  where  the  recti  muscles  are  inserted 
into  the  sclerotic  ;  two  or  three  veins  are  associated  with  each  muscle-tendon  and  open  into  the 
muscular  veins,  ( g)  The  posterior  ciliary  veins  (vv.  ciliares  posteriores)  accompany  the  poste- 
rior or  short  ciliary  arteries.  The  territory  supplied  by  the  arteries  is,  however,  drained  by  the 
venae  vorticosae,  and  the  posterior  ciliary  veins,  which  are  very  small,  take  their  origin  only  from 
the  posterior  portion  of  the  sclerotic  and  from  the  sheath  of  the  optic  nerve.  (A)  The  vena  cen- 
tralis retinae  is  a  single  stem  which  accompanies  the  corresponding  artery  through  the  centre  of  the 
optic  nerve,  and  has  its  origin  in  branches  which  ramify  over  the  surface  of  the  retina.  The  vein 
leaves  the  optic  nerve  usually  before  the  artery  and  opens  either  into  the  superior  ophthalmic 
vein  or,  more  frequently,  directly  into  the  cavernous  sinus. 

2.  The  Inferior  Ophthalmic  Vein. — The  inferior  ophthalmic  vein  (v.  oph- 
thalmica  inferior)  (Fig.  757)  takes  its  origin  from  a  net- work  of  small  veins  situated 
on  the  inner  portion  of  the  floor  of  the  orbit  near  its  border.  This  plexus  communi- 
cates with  the  facial  vein  and  is  continued  backward  towards  the  fundus  of  the  orbit, 
more  frequently  as  a  coarse  net-work  than  as  a  definite  stem.  The  vein,  when  it 
exists,  or  the  net-work,  anastomoses  with  branches  of  the  superior  ophthalmic. 

Tributaries. — (a)  Muscular  branches  from  the  inferior  and  external  recti  and  the  inferior 
oblique  muscles  and  (b)  the  inferior  venae  vorticosae  from  the  lower  half  of  the  eyeball. 
It  opens  posteriorly  either  directly  into  the  cavernous  sinus  or  else  unites  with  the  superior 
ophthalmic  vein. 


88o  HUMAN    ANATOMY. 

Anastomoses  of  the  Ophthalmic  Veins.— The  ophthalmic  veins  are  throughout  destitute 
of  valves  and  open  posteriorly  into  the  cavernous  sinus,  and,  since  they  also  communicate  with 
peripheral  veins,  they  may  well  be  regarded  as  emissary  channels  through  which  the  blood  may 
flow  either  from  the  cavernous  sinus  to  the  peripheral  veins  or  in  the  reverse  direction,  as  may 
be  determined  by  the  relative  pressure  within  and  without  the  cranium.  The  principal  connec- 
tions which  the  veins  make  are  ( i )  with  the  facial  vein,  which  is  itself  practically  devoid  of 
valves,  through  their  branches  of  origin  ;  (2)  with  the  veins  of  the  nasal  cavity  through  the  eth- 
moidal branches  ;  and  (3)  with  the  pterygoid  plexus  by  means  of  a  branch  of  the  inferior  ophthal- 
mic which  passes  downward  through  the  spheno-maxillary  fissure. 

Practical  Considerations. — The  communication  between  the  superior 
ophthalmic  vein — the  largest  channel  in  the  adult  between  the  vessels  of  the  venous 
system  of  the  head  and  face  and  the  sinuses  of  the  dura  mater — and  the  facial  vein, 
while  adding  to  the  danger  of  intracranial  complications  as  a  result  of  infectious  disease 
situated  upon  the  face  (page  873),  affords  relief  to  intraocular  tension  in  cases  of 
pressure  upon  the  cavernous  sinus,  as  from  an  inflammatory  exudate  or  an  intra- 
orbital or  intracranial  growth.  Such  relief  delays  the  appearance  of  ' '  choked  disc' ' 
(page  1471),  due  to  the  distension  of  the  tributaries  of  the  vein,  especially  the  poste- 
rior ciliary  veins  and  the  vena  centralis  retinae.  In  arterio-venous  aneurism  of  the 
cavernous  sinus  and  internal  carotid  artery — due  to  basal  cranial  fracture,  a  bullet  - 
or  stab-wound,  or  to  idiopathic  vascular  degeneration — the  ophthalmic  veins  are 
usually  compressed  and  may  transmit  pulsation  from  the  sinus  to  the  dilated  veins 
of  the  eyelids  and  of  the  frontal  region.  The  conjunctivae  are  congested.  Exoph- 
thalmos (page  1439),  bruit  and  thrill  are  not  uncommonly  present  as  a  result  of 
involvement  of  the  intraorbital  veins.  Nervous  symptoms — noise  in  the  head, 
intracranial  or  frontal  pain  and  paralyses — are  rarely  absent. 

These  symptoms  may  be  simulated  by  those  caused  by  traumatic  aneurism  of 
an  orbital  artery  or  by  the  direct  pressure  of  an  internal  carotid  aneurism  on  the 
ophthalmic  vein  as  it  empties  into  the  sinus. 

The  External  Jugular  Vein. 

The  external  jugular  vein  (v.  jugularis  externa)  (Fig.  759),  notwithstanding  its 
usual  connection  with  the  subclavian,  is  closely  related  both  in  its  development  and 
topographical  relations  with  the  internal  jugular,  and  may  be  most  conveniently  con- 
sidered here.  It  is  formed  in  the  neighborhood  of  the  angle  of  the  mandible  by  the 
union  of  the  temporo-maxillary  and  posterior  auricular  veins,  and  courses  downward 
immediately  below  the  platysma,  crossing  the  sterno-cleido-mastoid  muscle  obliquely. 
In  the  lower  part  of  the  neck  it  pierces  the  superficial  layer  of  the  deep  cervical 
fascia,  sometimes  above  and  sometimes  below  the  posterior  belly  of  the  omo-hyoid, 
and  opens  into  the  subclavian  vein  near  its  junction  with  the  internal  jugular.  A 
short  distance  below  its  origin  it  gives  off  a  large  branch  which  passes  forward  and 
downward  to  communicate  with  the  facial  vein. 

At  its  entrance  into  the  subclavian  it  is  provided  with  a  pair  of  valves,  and  usually 
a  second  pair  occurs  at  about  the  middle  of  the  neck.  A  third  pair  is  occasionally 
present  in  the  interval  between  the  other  two,  and  all  of  them  are  insufficient. 
The  superficial  layer  of  the  deep  cervical  fascia  is  intimately  adherent  to  the  walls 
of  the  vein  at  the  point  where -the  latter  perforates  it,  and  sometimes  the  fascia 
is  especially  thickened  immediately  below  and  to  the  inner  side  of  the  vein.  This 
attachment  of  the  fascia  prevents  any  collapse  of  the  walls  of  the  lower  part  of  the 
vein,  if  for  any  reason  there  is  a  deficiency  in  the  amount  of  blood  it  contains,  and 
predisposes,  therefore,  to  the  entrance  of  air  in  case  the  vein  is  severed. 

Variations. — Considerable  differences  of  opinion  exist  as  to  the  definition  of  the  external 
jugular  vein.  Some  authors  describe  it  as  formed  by  the  union  of  the  posterior  auricular  and 
occipital  veins,  the  communicating  branch  described  above  as  occurring  between  it  and  the 
facial  being  then  regarded  as  the  main  stem  of  the  temporo-maxillary  ;  others,  again,  regard  it 
as  formed  by  the  union  of  the  temporal  and  maxillary  veins,  the  temporo-maxillary  then  con- 
stituting its  upper  portion. 

The  vein  is  subject  to  considerable  variation  in  size,  an  inverse  correlation  existing  between 
it  and  the  anterior  jugular.  It  may  even  be  entirely  wanting  or,  on  the  other  hand,  it  may  be 
double  throughout  a  portion  of  its  course.  It  occasionally  divides  below,  one  branch  passing, 
as  usual,  to  the  subclavian,  while  the  other,  passing  over  the  clavicular  attachment  of  the  sterno- 
cleido-mastoid,  opens  into  either  the  anterior  or  the  internal  jugular. 


THE   SUPERIOR    CAVAL    SYSTEM.  881 

In  connection  with  the  abundant  variation  shown  in  the  size  of  the  external  jugular  it  is 
interesting  to  note  that  in  the  majority  of  mammals  it  is  the  most  important  vein  of  the  neck, 
surpassing  the  internal  jugular  in  size.  It  is,  however,  of  later  development  than  the  latter, 
and  its  later  importance  is  due  largely  to  the  union  with  it  of  the  facial  vein  or  of  the 
linguo-facial  trunk.  In  man,  however,  a  new  connection  of  the  facial  with  the  internal  jugular 
occurs,  whereby  the  importance  of  the  external  jugular  becomes  reduced,  and  its  variation 
in  size  is  largely  dependent  upon  the  extent  to  which  the  original  direct  connection  of 
the  facial   with   it  is   retained. 


Fig.  759. 


Superficial 
temporal 
Middle  temporal 


Superficial 


beneath  platysma 


Practical  Considerations. — The  line  of  the  external  jugular  vein  is  from  the 
ano-le  of  the  jaw  to  the  centre  of  the  clavicle.  Backward  pressure  made  about 
an  inch  above  the  latter  point  will  cause  the  vein  to  become  visible  through- 
out its  length.  For  that  reason  it  was  at  one  time  selected  for  phlebotomy  in 
congestions  or  inflammations  about  the  face  and  neck.  The  vein  is  in  the 
superficial  fascia  and  therefore  courses  over  the  sterno-mastoid  muscle.  In  all 
operations  on  the  side  of  the  neck  its  size  and  its  course  should  be  borne  in  mind. 

56 


882  HUMAN    ANATOMY. 

Tributaries. — The  tributaries  of  the  external  jugular  are  (i)  the  temporo- 
maxillary,  (2)  the  posterior  auricular,  (3)  the  posterior  external  jugular,  (4)  the 
suprascapular,  and  (5)  the  anterior  jugular  vein.  It  may  also  receive  the  occipital 
vein  (page  859). 

1.  The  Temporo-Maxillary  Vein. — The  temporo-maxillary  vein  (v,  facialis 
posterior)  (Fig.  753)  is  formed  in  the  substance  of  the  parotid  gland  by  the  union  of  the 
temporal  and  internal  maxillary  veins.  It  passes  directly  downward,  and  at  about  the 
angle  of  the  jaw  unites  with  the  posterior  auricular  vein  to  form  the  external  jugular. 

The  temporal  vein  accompanies  the  temporal  artery  and  is  formed  just  above 
the  zygoma  by  the  union  of  the  superficial  and  middle  temporal  veins.  The  super- 
ficial temporal  vein  (v.  temporalis  superficialis)  (Fig.  759)  is  formed  by  the 
union  of  an  anterior  and  a  posterior  branch,  which  take  their  origin  in  a  plexus 
covering  the  greater  portion  of  the  skull-cap  and  communicate  anteriorly  with 
branches  of  the  frontal  vein  and  posteriorly  with  the  posterior  auricular  and  occipital 
veins.  The  middle  temporal  (v.  temporalis  media)  arises  from  a  plexus  which 
lies  upon  the  outer  surface  of  the  temporal  muscle,  beneath  the  temporal  fascia  and 
above  the  zygoma.  Branches  of  the  plexus  pierce  the  temporal  fascia  near  the 
external  angle  of  the  eye  and  communicate  with  branches  of  the  facial  and  lachrymal 
nerves,  while  other  branches  pass  deeply  into  the  substance  of  the  temporal  muscle 
and  anastomose  with  the  deep  temporal  veins.  The  middle  temporal,  from  its  origin 
in  the  plexus,  passes  backward  parallel  with  the  upper  border  of  the  zygoma, 
perforates  the  temporal  fascia,   and  joins  with  the  superficial  temporal  vein. 

Tributaries. — The  temporal  vein  receives  the  following  tributaries,  (a)  The  anterior 
auricular  veins  (vv.  auriculares  anteriores)  are  four  or  five  small  vessels  which  come  from  the 
anterior  surface  of  the  pinna,  (b)  The  posterior  parotid  veins  (vv.  parotideae  posteriores),  small 
branches  which  drain  the  parotid  gland,  communicating  with  the  anterior  parotid  branches  of 
the  facial,  (c)  The  articular  veins  (vv.  articulares  mandibulae),  several  in  number,  arise  in  a  rich 
plexus  which  surrounds  the  synovial  membrane  of  the  temporo-mandibular  articulation. 
This  plexus  receives  tympanic  branches  (vv  tympanicae),  which  accompany  the  tympanic 
artery  through  the  Glaserian  fissure,  and  communicates  anteriorly  with  the  pterygoid  plexus. 
(d)  The  transverse  facial  vein  (v.  transversa  faciei)  which  accompanies  the  artery  of  the 
same  name. 

The  internal  maxillary  vein  (v.  maxillaris  interna)  (Fig.  760)  appears 
sometimes  as  a  distinct  vessel  accompanying  the  internal  maxillary  artery  and 
receiving  as  tributaries  veins  corresponding  to  the  arterial  branches.  In  other  cases 
it  is  represented  by  a  plexus  of  veins,  frequently  exceedingly  dense,  occupying  the 
pterygoid  fossa  and  communicating  anteriorly  with  the  facial  vein  and  posteriorly 
with  the  temporo-maxillary.  This  pterygoid  plexus  (plexus  pterygoideus)  (Fig. 
760)  is  embedded  in  the  adipose  tissue  which  occupies  the  pterygoid  fossa  and 
consists  of  two  portions,  one  situated  upon  the  outer  surface  of  the  external 
pterygoid  muscle  and  the  other  between  the  two  pterygoids,  this  latter  plexus 
being  somewhat  more  extensive  than  the  other,  with  which  it  is  united  by  branches 
passing  through,  above,  and  beneath  the  external  pterygoid  muscle.  It  is  also 
continued  forward  as  a  fine  plexus  surrounding  the  infra-orbital  nerve,  and  that 
portion  which  rests  upon  the  tuberosity  of  the  maxilla  is  occasionally  more  or  less 
distinct  from  the  remainder,  and  has  been  termed  the  plexus  alvcolaris. 

The  pterygoid  plexus  communicates  with  the  facial  vein  through  the  deep 
facial  or  anterior  internal  maxillary  vein,  with  the  pharyngeal  plexus,  and  with  the 
articular  plexus  of  the  temporo-mandibular  articulation.  It  further  receives  the 
emissary  veins  from  the  cavernous  plexus  which  traverse  the  foramen  ovale,  the  fora- 
men of  Vesalius,  and  the  foramen  lacerum  medium,  and  also  a  branch  from  the 
inferior  ophthalmic  vein  which  passes  through  the  spheno-maxillary  fissure. 

Tributaries. — The  tributaries  of  the  internal  maxillary  vein  or  the  pterygoid  plexus  may  be 
described  as  follows. 

(a)  The  spheno-palatine  vein  has  its  origin  in  the  rich  venous  plexus  which  underlies  the 
mucous  membrane  of  the  nasal  cavity  and  with  which  the  ethmoidal  veins  also  communicate. 
It  traverses  the  spheno-palatine  foramen  with  the  artery  of  the  same  name,  and  is  joined  by  the 
Vidian,  ptery go-palatine ,  and  superior  palatine  veins,  all  small  vessels  whose  origin  is  indicated 


THE   SUPERIOR    CAVAL  SYSTEM.  883 

by  their  names.     It  then  passes  between  the  two  heads  of  the  external  pterygoid  muscle  and 
opens  into  the  pterygoid  plexus  or  into  the  internal  maxillary  vein. 

(b)  The  superior  dental  veins  open  into  the  infra-orbital  and  alveolar  portions  of  the  plexus. 

(c)  Muscular  veins  from  the  masseter,  buccal,  and  pterygoid  muscles. 

(d)  The  deep  temporal  veins  (vv.  temporales  profundae)  descend  from  the  substance  of  the 
temporal  muscle,  where  they  anastomose  with  the  superficial  temporals,  between  the  muscle 
and  the  bone. 

(e)  The  middle  meningeal  veins  (vv.  meningeae  mediae)  accompany  the  main  stem  and 
branches  of  the  middle  meningeal  artery  as  vena;  comites  and  return  the  blood  from  the  dura  mater 
lining  the  sides  and  vertex  of  the  cranium.     Lying  in  the  substance  of  the  dura  mater,  these  veins 


Fig.  760. 


Temporal  muscle 

Superficial 

temporal 


Middle 

temporal 
Middle 

meningeal 


Temporal 

Pterygoid  pi 

Internal  pterygoid  m 
Temporo-maxillary 
Posterior  auricular 

Posterior  trunk  of 

temporo-maxillary 
Anterior  trunk  of 

temporo-maxillary 

Sterno-cleido-mastoid 


Veins  of  head ;   part  of 


ndible  and  associated  muscle 
:o  expose  pterygoid  plexus. 


resemble  the  sinuses  of  the  dura  in  their  structure,  and  they  communicate  with  the  blood-lakes  of 
the  dura,  with  the  superior  longitudinal,  spheno-parietal  and  petro-squamosal  sinuses,  and  with 
the  superficial  Sylvian  vein.  They  open  below  into  the  deeper  portion  of  the  pterygoid  plexus. 
(/)  The  inferior  dental  vein  follows  the  course  of  the  inferior  dental  artery,  opening  above 
into  the  more  superficial  portion  of  the  plexus. 

2.  The  Posterior  Auricular  Vein. — The  posterior  auricular  vein  (v.  auricularis 
posterior)  arises  from  a  plexus  situated  over  the  mastoid  portion  of  the  temporal  bone 
and  communicating  with  branches  of  the  occipital  and  temporal  veins.      It  descends 


884  HUMAN    ANATOMY. 

behind  the  pinna,  occasionally  receiving  the  mastoid  emissary  vein,  and  terminates  near 
the  angle  of  the  jaw  by  uniting  with  the  temporo-maxillary  to  form  the  external  jugular. 

3.  The  Posterior  External  Jugular  Vein. — The  posterior  external  jugular 
vein  arises  from  the  integument  and  muscles  of  the  upper  and  back  part  of  the  neck, 
just  below  the  occipital  region,  and  descends  obliquely  behind  the  sterno-cleido-mastoid 
muscle  to  open  into  the  external  jugular  just  after  it  has  crossed  the  muscle. 

4.  The  Suprascapular  Vein. — The  suprascapular  vein  (v.  transversa  scapulae) 
is  really  a  double  vein,  being  represented  by  two  vessels  provided  with  valves  which 
accompany  the  suprascapular  artery  as  its  vena?  comites.  They  arise  upon  the 
upper  part  of  the  dorsal  surface  of  the  scapula,  pass  over  the  transverse  ligament  of 
that  bone,  and  are  continued  inward,  parallel  with  the  clavicle  and  behind  it,  to  open 
into  the  external  jugular  near  its  termination  or  else  directly  into  the  subclavian. 
Just  before  their  termination  the  two  venae  comites  unite  to  a  single  stem. 

The  suprascapular  vein  is  usually  joined  either  at  or  near  its  termination  by  the 
transverse  cervical  veins  which  form  the  venae  comites  of  the  transversalis  colli  artery. 
These  veins  may  also  open,  however,  directly  into  the  subclavian. 

5.  The  Anterior  Jugular  Vein. — The  anterior  jugular  vein  (v.  jugularis 
anterior)  (Fig.  753)  arises  beneath  the  chin,  upon  the  mylo-hyoid  muscle,  by  branches 
which  come  from  the  integument  and  superficial  muscles  of  that  region,  communicating 
with  the  submental  branches  of  the  facial.  The  vein  passes  almost  vertically  down  the 
neck,  resting  upon  the  sterno-hyoid  muscle  a  short  distance  lateral  from  the  median  line, 
until  it  meets  the  anterior  (inner)  border  of  the  sterno-cleido-mastoid  near  its  sternal 
attachment.  There  it  makes  an  abrupt  bend,  passing  almost  horizontally  outward 
beneath  the  muscle  to  open  into  the  external  jugular  immediately  above  its  termination. 

The  anterior  jugular  receives  a  communicating  branch,  occasionally  of  con- 
siderable size,  from  the  facial  subcutaneous  veins,  and  tributaries  from  the  median 
region  of  the  neck  also  open  into  it  ;  it  may  also  receive  small  branches  from  the  larynx 
and  thyroid  gland. 

It  contains  no  valves.  At  its  origin  it  is  superficial  to  the  deep  cervical  fascia,  but 
below  the  hyoid  bone  it  is  embedded  in  the  superficial  layer  of  that  fascia,  and  below 
lies  in  the  spatium  suprasternale  (space  of  Burns)  formed  by  the  splitting  of  the  fascia 
into  two  lamellae.  In  this  space  there  occurs  a  transverse  anastomosis  between  the 
two  veins,  forming  what  is  termed  the  arcus  venosus  juguli,  and  into  this  a  number 
of  small  branches  from  neighboring  structures  open.  The  horizontal  portion  of  the 
vein  eventually  pierces  the  posterior  layer  of  the  space  to  reach  the  external  jugular. 

Variations. — The  anterior  jugular  varies  considerably  in  size,  inversely  to  the  external 
jugular.  Occasionally  the  two  veins  of  opposite  sides  unite  throughout  the  vertical  portion  of 
their  course  to  form  a  single  stem,  which  passes  down  the  median  line  of  the  neck  and  has  con- 
sequently been  termed  the  v,  mediana  colli. 

The  communicating  branch  from  the  facial  vein,  which  passes  downward  along  the  anterior 
border  of  the  sterno-cleido-mastoid,  is  sometimes  quite  large,  functioning  as  the  direct  continua- 
tion of  the  facial,  which  may  thus  pour  its  blood  mainly,  if  not  entirely,  into  the  anterior  jugular. 
Below,  while  the  anterior  jugular  usually  opens  into  the  external  jugular,  yet  it  sometimes  opens 
directly  into  the  subclavian,  and  occasionally  it  receives  near  its  termination  an  ex'ternal  thoracic 
vein,  which  ascends  from  the  region  of  the  mammary  gland  over  the  clavicle,  posterior  to  the 
attachment  of  the  sterno-cleido-mastoid. 

The  Subclavian  Vein. 

The  subclavian  vein  (v.  subclavia)  (Fig.  753)  is  the  terminal  portion  of  the  venous 
system  of  the  upper  extremity.  It  begins  at  the  anterior  border  of  the  first  rib,  where 
it  is  directly  continuous  with  the  axillary  vein,  and  passes  almost  horizontally  inward, 
anterior  to  the  scalenus  anticus  muscle  and  behind  the  clavicle,  to  the  junction 
of  that  bone  with  the  sternum,  where  it  unites  with  the  internal  jugular  to  form  the 
innominate  vein.  Its  course  is  very  similar  to  that  of  the  subclavian  artery,  but  it 
is  more  horizontal  and  somewhat  anterior  to  the  artery,  from  which  it  is  separated 
by  the  scalenus  anticus. 

It  is  provided  with  a  pair  of  valves  at  its  junction  with  the  internal  jugular  and  with 
another  pair  at  its  junction  with  the  axillary  vein.  In  the  first  portion  of  its  course  it 
is  in  relation  anteriorly  with  the  subclavius  muscle,  and  its  anterior  wall  is  united  to 


THE   SUPERIOR   CAVAL  SYSTEM.  885 

the  fascia  which  encloses  that  muscle  ;  near  its  termination  it  is  united  to  the 
middle  layer  of  the  deep  cervical  fascia,  behind  which  it  lies.  As  a  result  of  these 
connections  the  vein  does  not  collapse  when  empty,  and,  furthermore,  its  lumen  is 
enlarged  by  movements,  such  as  those  of  inspiration  or  the  raising  of  the  arm, 
which  affect  the  fascia. 

With  the  exception  of  the  external  jugular  and  occasionally  the  anterior 
jugular,  the  subclavian  vein  receives,  as  a  rule,  no  tributaries,  the  veins  which 
correspond  to  the  branches  of  the  subclavian  artery  opening  either  into  the 
innominate  or  the  external  jugular.  Occasionally,  however,  it  receives  the  supra- 
scapular and  the  superior  intercostal  vein  (page  896),  and  the  acromial  thoracic 
vein  may  open  into  it  near  its  beginning. 


Fig.  761. 


Descending 
branches  of 
cervical  plexus 


Subclavian  artery 


Clavicular  portk 
sterno-mastoid,  t 
turned  forward 


Anterior  scale 
Phrenic  nerve 


Internal  jugular  vein 
Sternal  portion  of 

sterno-mastoid 
Common  carotid  artery 
Sterno-hyoid  muscle 

First  rib 


Variations. — Occasionally  the  course  of  the  subclavian  vein  has  the  form  of  a  curve  which 
rises  above  the  level  of  the  clavicle  and  may  even  bring  the  vein  to  lie  above  the  artery.  It  may 
pass  with  the  artery  behind  the  scalenus  anticus,  the  artery  and  vein  may  exchange  places  with 
reference  to  that  muscle,  or  the  vein  may  divide  to  form  a  ring  encircling  the  muscle.  Rarely  it 
passes  between  the  subclavius  muscle  and  the  clavicle. 


Practical  Considerations. — The  subclavian  vein  occupies  the  acute  inner 
angle  between  the  clavicle  and  the  first  rib,  and  therefore — and  on  account  of  its 
slight  resistance — in  periosteal  or  osseous  growths  from  those  bones  is  especially 
likely  to  suffer  compression.  The  interposed  subclavius  muscle  usually  protects  it, 
as  it  does  the  artery  and  the  brachial  plexus,  from  injury  in  case  of  fracture  (page  259). 
The  vein  barely  rises  above  the  clavicle,  and  therefore  usually  escapes  in  stab- 
wounds  involving  the  supraclavicular  fossa,  while  the  artery  which  arches  an  inch 
to  an  inch  and  a  half  above  that  line  suffers  much  oftener. 

The  connection  of  the  anterior  wall  of  the  vein  with  the  fascia  of  the  subclavius 
muscle,  causing  an  increase  in  its  calibre  during  forced  inspiration  or  an  elevation  of 
the  arm  {vide  supra),  should  be  remembered  in  case  of  wound  of  this  vessel  during 


886  HUMAN    ANATOMY. 

operation,  as  elevation  of  the  clavicle  may  then  be  followed  by  the  entrance  of  air 
into  the  vein  (Henle).  Obstruction  of  the  subclavian  at  the  point  of  junction  with 
the  internal  jugular  results  in  compression  of  the  orifice  of  the  thoracic  duct. 

THE  VEINS   OF   THE   UPPER    EXTREMITY. 

Instead  of  following  distally  the  various  branches  which  return  the  blood  from 
the  upper  limb  it  will  be  more  convenient  to  begin  with  the  peripheral  branches  and 
trace  the  vessels  proximally  towards  the  subclavian. 

The  veins  of  the  upper  extremity  may  be  divided  into  a  superficial  and  a  deep 
set.  The  latter  follow  in  general  the  course  of  the  arteries,  of  which  they  are,  as  a 
rule,  the  vena?  comites.  They  anastomose  frequently  with  the  superficial  veins  and 
are  more  richly  supplied  with  valves  than  are  the  latter. 

THE    DEEP   VEINS. 
The  Deep  Veins  of  the  Hand. 

The  deep  veins  of  the  hand  are  all  relatively  small  and  are  of  less  importance 
than  the  superficial  ones  in  returning  the  blood.  Each  of  the  palmar  arterial 
arches  is  accompanied  by  venae  comites,  and  into  those  of  the  superficial  arch  (arcus 
volaris  venosus  superficialis)  the  superficial  digital  veins  (vv.  digitales  volares  com- 
munes) open,  while  those  of  the  deep  arch  (arcus  volaris  venosus  profundus)  receive 
the  veins  (vv.  metacarpeae  volares)  which  accompany  the  aa.  princeps  pollicis,  radialis 
indicis,  and  interossei  palmares. 

Upon  the  dorsum  of  the  hand  even  more  than  on  its  volar  surface  the  chief 
part  is  played  by  the  superficial  veins.  Three  or  four  pairs  of  dorsal  interosseous 
veins  occur,  however,  accompanying  the  corresponding  arteries  and  opening  event- 
ually partly  into  the  radial  veins  and  partly,  through  the  veins  corresponding  to  the 
posterior  carpal  net-work,  into  the  superficial  veins  of  the  dorsum  of  the  wrist  (rete 
venosum  dorsale  manus).  As  in  the  case  of  the  arteries,  the  deep  veins  of  the  dorsal 
and  volar  surfaces  of  the  hand  are  connected  by  perforating  veins,  and  both  make 
numerous  connections  with  the  superficial  veins. 

The  Deep  Veins  of  the  Forearm. 

The  deep  veins  of  the  forearm  are  the  venae  comites  which  accompany  the  radial 
and  ulnar  arteries  and  their  branches.  The  radial  veins  (vv.  radiales)  are  the 
upward  continuation  of  the  veins  of  the  deep  palmar  arch  and  are  relatively  slender. 
The  ulnar  veins  (vv.  ulnares)  are  larger  and  are  formed  by  the  union  of  the  ulnar 
ends  of  the  venae  comites  of  both  the  superficial  and  deep  palmar  arches.  Usually 
they  have  a  large  communication  from  the  superficial  veins  of  the  dorsum  of  the  hand, 
and  receive  near  the  elbow  the  veins  which  accompany  the  interosseous  artery  and 
its  branches,  and  also  a  strong  communicating  branch,  the  deep  median  vein,  from 
the  superficial  median  (page  890).  Both  the  ulnar  and  radial  veins  are  well  supplied 
with  valves,  and  they  unite  at  the  elbow  to  form  the  brachial  veins. 

The  Brachial  Veins. 

The  brachial  veins  (vv.  brachiales)  (Fig.  762)  are  the  companion  veins  of  the 
brachial  artery  and  receive  tributaries  corresponding  to  the  branches  of  the  artery. 
They  are  formed  at  about  the  elbow-joint  by  the  union  of  the  radial  and  ulnar  veins, 
and  extend  upward,  one  on  either  side  of  the  brachial  artery,  to  the  lower  border  of  the 
pectoralis  major  muscle,  at  about  which  level  they  unite  to  form  a  single  trunk,  termed 
the  axillary  vein. 

As  is  usual  with  venae  comites,  the  two  brachial  veins  are  united  by  numerous 
anastomoses  and  occasionally  unite  through  portions  of  their  course,  especially  above,  to 
form  a  single  trunk.  At  the  elbow  one  of  the  veins  frequently  lies  in  front  of  the  artery 
and  sometimes  the  two  veins  pursue  a  spiral  course  around  it.  In  addition  to  the 
tributaries  which  accompany  the  branches  of  the  brachial  artery,  the  brachial  veins,  or 
rather  the  inner  one  of  the  two,  receive  near  their  termination  the  basilic  vein  (page  890). 


VEINS   OF   THE   UPPER   EXTREMITY. 


The  Axillary  Vein. 


Fig.  762. 


Costo-coracoid 


The  axillary  vein  (v. 
axillaris)  (Fig.  762)  is 
formed  by  the  union  of 
the  two  brachial  veins, 
usually  at  about  the  lower 
border  of  the  pectoralis 
major.  It  lies  along  the 
inner  side  of  the  axillary 
artery,  and  at  the  lower 
border  of  the  first  rib 
passes  directly  into  the 
subclavian  vein.  In  the 
lower  part  of  its  course  it  is 
separated  from  the  artery 
by  the  ulnar  nerve  and  the 
inner  head  of  the  median  ; 
above,  it  is  more  nearly  in 
contact  with  it. 

The  axillary  vein 
possesses  a  pair  of  valves, 
usually  situated  at  the 
level  of  the  lower  border  of 
the  subscapularis  muscle. 
Its  walls  are  intimatelv 
connected  with  the  fascia 
of  the  axillary  space,  so 
that,  as  in  the  case  of  the 
subclavian,  its  lumen 
remains  patent  even  when 
empty  of  blood,  and  con- 
sequently air  may  possibly 
enter  in  cases  where  the 
vein  is  wounded. 

Tributaries. — 
These  correspond  in 
general  with  the  branches 
of  the  artery,  except  that 
the  axillary  vein  receives 
the  cephalic,  which  is  un- 
represented by  an  artery, 
and,  furthermore,  the 
acromial  thoracic,  which 
corresponds  to  the  artery 
of  the  same  name,  instead 
of  opening  into  the  axil- 
lary, connects  with  the 
cephalic.  Of  especial 
importance  among  the 
tributaries  is  the  long 
thoracic  vein  (v.  thorac- 
alis  lateralis)  which  brings 
to  the  axillary  the  blood 
from  the  lateral  walls  of 
the  thorax.  Its  branches 
of  origin  are  the  venae 
comites  of  the  branches  of  the  thoracic  arteries,  and  they  return  the  blood  from  the 


Median  cephalic 
Superficial  radial 


Superficial  veins  of  anterior  surface  of  right  forearm  and 
axillary  vein  and  its  tributaries. 


888  HUMAN    ANATOMY. 

pectoral  and  serratus  magnus  muscles  and  in  part  from  the  intercostals.  They  are 
abundantly  supplied  with  valves,  and  unite  to  a  single  stem  which  presents  variations 
in  its  connections  with  the  axillary  vein  similar  to  those  described  for  the  corresponding 
artery.  By  means  of  the  costo-axillary  veins  (w.  costo-axillares),  which  pass  from 
the  middle  portions  of  the  upper  six  or  seven  intercostal  spaces,  it  forms  anastomoses 
with  the  intercostal  veins  which  open  into  the  azygos  system. 

These  costo-axillary  veins  open  either  directly  into  the  long  thoracic  or  into 
the  thoraco-epigastric  vein  (v.  thoracoepigastrica),  a  more  or  less  definite  stem 
which  extends  upward  along  the  lateral  walls  of  the  thorax,  subcutaneously,  to  open 
into  the  long  thoracic  near  its  termination.  It  receives  numerous  tributaries  from  the 
rich  subcutaneous  venous  net-work  which  occurs  upon  the  anterior  and  lateral 
walls  of  the  thorax  (w.  cutaneae  pectoris),  and  communicates  directly  below  with  epi- 
gastric branches  from  the  femoral  vein,  thus  forming  an  important  communication 
between  the  superior  and  inferior  caval  systems.  It  also  receives  the  veins  coming 
from  the  region  of  the  mammary  gland,  where  the  pectoral  cutaneous  veins  form  a 
net-work  surrounding  the  nipple,  the  plexus  venosus  mammillae.  The  deeper 
veins  of  the  gland  open  in  part  directly  into  the  long  thoracic,  whence  this  has 
been  termed  the  external  mammary  vein,  and  partly  into  the  internal  mammary 
by  branches  which  accompany  the  perforating  branches  of  the  internal  mammary 
artery  (page  860). 

Practical  Considerations. — When  the  axillary  vein  is  formed  by  the  junc- 
tion of  the  two  brachial  veins  with  the  basilic  vein,  the  union  occurs  usually  at  the 
inferior  border  of  the  subscapularis  muscle.  The  vein  is  then  somewhat  shorter 
than  the  artery.  Occasionally  the  coalescence  of  these  tributaries  does  not  take 
place  until  a  level  just  beneath  the  lower  border  of  the  clavicle  has  been  reached. 
When  this  is  the  case,  operations  in  the  axilla  will  involve  the  ligation  of  many  com- 
municating transverse  veins  crossing  the  artery  to  join  the  vena;  comites  lying  upon 
either  side  of  it. 

Phlebitis  of  the  veins  of  the  upper  extremity  is  but  seldom  transmitted  to  the 
axillary  vein,  rarely  to  the  subclavian,  and  never  to  the  internal  jugular  or  innomi- 
nate (Allen).  This  immunity  is  supposed  to  be  due  to  disproportionately  greater 
size  of  a  main  venous  trunk  as  compared  with  its  tributaries  ;  any  of  the  radicles  of 
the  veins  of  the  hand,  forearm,  and  arm — whose  calibres  are  nearly  equal — readily 
transmitting  infection.  Phlebitis  of  the  axillary  vein  may,  through  the  costo-axillary 
branches  of  the  long  thoracic  vein,  extend  to  within  the  thorax  and  result  in  a  septic 
pleurisy. 

Accidental  wounds  of  the  axillary  vein — especially  of  its  upper  portion — are 
dangerous  on  account  of  its  size,  its  nearness  to  the  thorax — so  that  it  markedly 
shows  the  respiratory  wave — and  its  attachment  to  the  costo-coracoid  membrane, 
preventing  its  collapse,  favoring  hemorrhage,  or,  when  it  is  empty,  permitting  the 
entrance  of  air.  It  lies  within  and  a  little  below  the  artery,  which  it  overlaps, 
particularly  towards  its  upper  and  lower  portions,  and  when  it  is  distended  during 
expiration.  As  it  is  straighter  than  the  artery,  the  curve  of  the  latter  carries  it  a  little 
away  from  the  vein  at  the  middle  portion.  Abduction  of  the  arm  brings  the  vein  to 
a  higher  level  and  often  almost  in  front  of  the  artery  so  as  partly  to  hide  it.  It  will 
therefore  be  found  with  this  relationship  in  many  operations  upon  the  axilla,  and  it  is 
on  account  of  it — i.  e. ,  its  more  superficial  position — and  of  its  larger  size  that  the  vein  is 
more  frequently  wounded  than  is  the  artery.  On  the  other  hand,  the  axillary  artery 
is  oftener  ruptured,  as  in  the  manipulations  for  the  reduction  of  old  luxations  of  the 
shoulder,  probably,  as  such  luxations  are  more  frequent  in  old  persons,  on  account 
of  the  greater  loss  of  elasticity  of  its  thicker  walls,  and  possibly  on  account  of  greater 
traction  upon  it  by  reason  of  its  deeper  and  more  external  position  (page  769). 

The  close  relation  of  the  vein  to  the  deep  chain  of  axillary  glands  makes  it  the 
chief  source  of  danger  in  operations  for  the  removal  of  the  breast  and  cleaning  out 
the  axilla  in  cases  of  mammary  cancer,  especially  if  the  axillary  nodes  are  already 
notably  involved.  It  is  well,  therefore,  to  expose  the  vein  at  an  early  stage  of  the 
operation.  If  the  walls  have  been  invaded  by  the  disease,  or  if  extirpation  of  the 
cancerous  mass  is  impossible  without  resection  of  the  vein,  the  latter  operation  may 


VEINS    OF   THE    UPPER    EXTREMITY. 


Posterior  


be  performed.  The  resulting  swelling  and  cedema  of  the  upper  limb  are  minimized 
by  the  consecutive  enlargement  of  the  cephalic  vein.  Such  swelling  and  cedema  are 
common  symptoms  of  pressure  upon  the  axillary  vein  by  cancerous  lymph-nodes  in 
the  later  stages  of  mammary  cancer  (page  770).  Suture  of  the  wall  of  the  vein  in 
cases  of  accidental  and  of  operative  wound  has  been  successfully  performed. 

THE   SUPERFICIAL  VEINS. 
The  Superficial  Veins  of  the  Hand. 

The  veins  upon  the  dorsal  surface  (Fig.  763)  form  the  principal  superficial 
channels  for  the  return  of  blood  from  the  hand.  They  begin  in  a  plexus  upon  the 
dorsum  of  the  first  phalanges,  surrounding 

the  nail,  and  are  continued  over  the  sue-  Fig.  763. 

ceeding  phalanges  as  a  coarser  plexus  in 
which  longitudinal  trunks  (vv.  digitales 
dorsales  propriae)  can  be  more  or  less 
distinctly  perceived.  At  about  the  middle 
of  the  dorsum  of  the  proximal  phalanges 
transverse  arches  (arcus  veuosi  digitales), 
one  for  each  digit,  connect  the  various 
dorsal  digital  veins  ;  each  arch  is  concave 
proximally,  and  at  either  end  unites  with 
the  extremities  of  the  neighboring  arches 
to  form  four  dorsal  metacarpal  veins 
(vv.  metacarpeae  dorsales)  which  pass 
upward  along  the  lines  of  the  intermeta- 
carpal spaces.  Just  before  joining  with 
its  neighbors  each  digital  arch  receives 
intercapitular  veins  (vv.  intercapitu- 
lares)  which  ascend  in  the  web  of  the 
fingers  from  the  volar  surface  and  assist  in 
the  passage  of  the  blood  of  the  superficial 
volar  veins  into  those  of  the  dorsal  surface. 

The  four  dorsal  metacarpal  veins  are 
abundantly  connected  by  anastomosing 
branches  which  pass  obliquely  from  one 
vein  to  the  other,  a  net- work  (rete  venosum 
dorsale  manus)  with  elongated  meshes 
being  thus  formed.  The  veins  of  the  first 
and  fourth  intermetacarpal  spaces,  as  a 
rule,  however,  retain  a  greater  amount  of 
individuality  than  the  other  two,  and  have 
consequently  received  special  names,  that 
of  the  first  interspace  being  sometimes 
termed  the  vena  cephalica  pollicis, 
while  that  of  the  fourth  interspace  is  the 
vena  salvatella.  The  dorsal  net-work 
is  drained  by  two  veins  which  pass  up  the 
forearm,  the  cephalic  and  basilic  veins. 

The  superficial  veins  of  the  volar 
surface  of  the  hand  are  small  and  for  the 
most  part  open  into  the  dorsal  veins. 
They  arise  as  a  plexus  in  the  balls  of  the 
fingers  and  pass  along  the  volar  surfaces 
of  the  digits  as  a  plexus  in  which  longitudi- 
nal trunks  (vv.  digitales  volares  propriae) 
can  be  distinguished.  From  the  plexus  of  each  finger  branches  wind  around  the  sides  of 
the  digits  to  open  into  the  dorsal  digital  veins,  and  at  the  roots  of  the  fingers  important 
connections  in  a  similar  direction  are  made  by  the  intercapitular  veins  (see  above). 


890  HUMAN   ANATOMY. 

The  superficial  veins  of  the  palm  of  the  hand  are  situated  superficially  to  the 
palmar  aponeurosis.  They  are  for  the  most  part  small,  and  form  a  net-work  which 
is  open  over  the  central  part  of  the  palm,  but  much  closer  over  the  thenar  and 
hypothenar  eminences.  These  lateral  portions  communicate  with  the  dorsal  net-work 
as  well  as  the  net-work  of  the  anterior  surface  of  the  forearm,  into  which  the  central 
portion  opens. 

The  Basilic  Vein. 

The  basilic  vein  (v.  basilica)  (Fig.  762)  takes  its  origin  from  the  ulnar  side  of 
the  dorsal  net-work  of  the  hand,  and  is  sometimes  described  as  the  direct  continuation 
of  the  dorsal  metacarpal  vein  of  the  fourth  interspace.  It  passes  obliquely  upward  and 
inward,  winding  around  the  border  of  the  hand  towards  the  anterior  surface  of  the  fore- 
arm, up  which  it  ascends.  Beyond  the  bend  of  the  elbow  it  continues  its  way  upward 
along  the  inner  border  of  the  biceps  muscle  as  far  as  the  upper  third  of  the  brachium, 
at  which  level  it  pierces  the  fascia  of  the  arm,  and  after  a  usually  short  subfascial 
course  terminates  by  opening  into  the  internal  brachial  vein. 

The  basilic  is  the  largest  of  all  the  superficial  veins  of  the  arm,  and  is  provided 
with  from  ten  to  fifteen  pairs  of  valves.  It  receives  tributaries  from  the  superficial 
plexus  of  the  thenar  eminence  and  from  the  anterior  and  posterior  surfaces  of  the 
forearm.  Near  the  elbow  it  receives  from  the  cephalic  vein  the  median  vein,  and 
also  communicates  with  the  cephalic  higher  up  by  branches  which  pass  across  the 
biceps  muscle,  and  with  the  brachial  veins  by  small  branches  which  pierce  the  brachial 
fascia. 

Variations. — The  basilic  is  little  subject  to  variation  except  in  regard  to  its  termination, 
which  is  frequently  in  the  axillary  and  sometimes  in  the  subclavian  ;  in  both  these  cases  the  sub- 
fascial portion  of  its  course  is  considerably  longer  than  usual.  Occasionally  it  is  accompanied 
throughout  its  course  by  an  accessor)'  basilic. 

The  portion  of  the  vein  extending  from  its  origin  to  the  bend  of  the  elbow  is  frequently 
spoken  of  as  the  superficial  ulnar  vein,  the  term  basilic  being  limited  to  the  brachial  portion  of 
the  vein  as  described  above. 

The  Cephalic  Vein. 

The  cephalic  vein  (v.  cephalica)  (Fig.  762)  takes  its  origin  from  the  radial  portion 
of  the  dorsal  net-work  of  the  hand,  and  especially  from  the  dorsal  metacarpal  vein 
of  the  first  interspace.  It  passes  upward,  inclining  forward  over  the  surface  of  the 
brachio-radialis  muscle,  and  so  reaches  the  anterior  surface  of  the  forearm.  Arrived 
at  the  bend  of  the  elbow,  it  ascends  along  the  groove  which  marks  the  outer  border  of 
the  biceps  muscle  and  then  in  the  groove  between  the  deltoid  and  the  pectoralis  major, 
and  at  the  upper  border  of  the  latter  muscle  it  passes  between  it  and  the  clavicle,  per- 
forates the  costo-coracoid  membrane,  and,  crossing  in  front  of  the  axillary  artery, 
empties  into  the  axillary  vein. 

It  is  provided  with  from  twelve  to  fifteen  pairs  of  valves,  of  which  from  four  to 
seven  occur  in  its  antibrachial  portion,  seven  in  its  brachial  portion,  and  one  at  its 
union  with  the  axillary. 

Tributaries. — The  cephalic  vein  receives  numerous  branches  from  the  super- 
ficial net-work  of  the  posterior  surface  of  the  forearm  and,  indeed,  plays  a  much 
more  important  part  in  the  drainage  of  this  region  than  does  the  antibrachial  portion 
of  the  basilic.  Quite  frequently  it  is  accompanied  in  its  course  up  the  forearm  by  an 
accessory  cephalic  vein  (v  cephalica  accessoria),  which  arises  in  the  posterior  super- 
ficial net-work  and  opens  into  the  main  cephalic  vein  at  the  bend  of  the  elbow.  It 
also  receives  branches  from  the  superficial  net-work  of  the  anterior  surface  of  the 
forearm  and,  a  short  distance  below  the  bend  of  the  elbow,  gives  off  a  strong  branch, 
the  median  vein  (v.  mediana  cubiti),  which  passes  obliquely  upward  and  inward  to 
open  into  the  basilic,  giving  off  in  its  course  a  communicating  branch  to  one  or  other 
of  the  deep  veins  of  the  forearm. 

In  its  brachial  portion  it  is  connected  with  the  basilic  by  branches  which  pass 
across  the  biceps  muscle,  and  just  before  opening  into  the  axillary  it  receives  the 
acromial  thoracic  vein  (v.  thoracoacromialis),  which  corresponds  to  the  artery  of 
the  same  name. 


VEINS    OF    THE    UPPER   EXTREMITY.  891 

Variations. — Unlike  the  basilic,  the  cephalic  vein  frequently  presents  variations  which  affect 
principally  its  brachial  portion.  One  of  the  most  important  of  these  is  the  complete  absence  of 
this  portion  of  the  vein,  the  antibrachial  portion  emptying  its  blood  into  the  basilic  by  means 
of  the  median  vein.  In  other  cases  it  is  only  the  uppermost  part  of  the  brachial  portion  that  is 
lacking,  the  lower  part  in  such  cases  either  making  connection  with  the  brachial  veins  or  else 
conveying  its  blood  downward  to  the  median  vein,  by  which  it  passes  to  the  basilic. 

Another  interesting  anomaly  consists  in  the  occurrence  of  a  branch  which  is  given  off  just 
as  the  vein  dips  downward  to  pierce  the  costo-coracoid  membrane.  It  is  termed  the  jugulo- 
cephalic  vein,  and  passes  up  over  the  clavicle  to  open  above  into  the  external  jugular  near  its 
communication  with  the  subclavian. 

These  variations  find  an  explanation  in  the  changes  undergone  by  the  superficial  veins  of 
the  arm  during  their  development,  both  the  absence  of  the  brachial  portion  of  the  vein  and  the 
occurrence  of  a  jugulo-cephalic  being  the  persistence  of  conditions  normally  passed  through  in 
development.  It  would  seem  that  three,  or  perhaps  better  four,  stages  are  to  be  recognized  in 
the  development  of  the  superficial  veins  of  the  arm.  In  the  first  stage  the  basilic  vein  forms  the 
only  great  superficial  trunk,  extending  up  the  inner  side  of  the  arm  from  the  wrist  to  the  axilla  and 
opening  into  the  axillary  vein  above.  Later,  however,  this  condition  is  modified  by  the  de- 
velopment of  the  antibrachial  portion  of  the  cephalic,  which  increases  in  size  at  the  expense  of 
the  antibrachial  portion  of  the  basilic  until  it  becomes  the  most  important  vein  of  the  forearm. 
At  the  bend  of  the  elbow  this  vein  receives  a  short  transverse  branch  formed  by  the  union  of  an 
ascending  and  descending  limb,  and  then  bends  obliquely  inward  to  join  the  brachial  portion  of 
the  basilic.  Higher  up  in  the  groove  between  the  pectoralis  major  and  deltoid  muscles  is  a 
small  deltoid  vein,  which  is  unconnected  with  the  veins  already  described.  Such  a  stage  as  this 
gives  a  clue  to  the  variations  in  which  the  brachial  portion  of  the  cephalic  is  either  absent  or 
only  partially  developed.  The  ascending  limb  of  the  transverse  branch  of  the  elbow,  and  this 
branch  itself,  together  represent  what  will  later  be  the  lower  part  of  the  brachial  portion  of  the 
cephalic,  while  the  deltoid  vein  represents  its  upper  part  ;  the  descending  limb  of  the  trans- 
verse branch  represents  the  accessory  cephalic  vein,  and  the  oblique  portion  of  the  antibrachial 
cephalic,  between  the  transverse  branch  and  the  basilic,  represents  the  median  vein.  Indeed, 
relics  of  this  condition  are  to  be  seen  even  in  the  normal  arrangement,  for  while  the  antibrachial 
portion  of  the  cephalic  usually  exceeds  in  size  the  corresponding  portion  of  the  basilic,  the  con- 
ditions are  reversed  in  the  brachial  portions  of  the  two  veins,  the  antibrachial  portion  of  the 
cephalic  and  the  brachial  portion  of  the  basilic  (connected  by  the  median)  forming  the  main 
channel  for  the  return  of  blood  from  the  superficial  portions  of  the  arm. 

A  third  stage  is  brought  about  by  the  completion  of  the  cephalic  vein  by  the  union  of  the 
ascending  limb  of  the  transverse  branch  with  the  deltoid,  the  vein  so  formed  being  continued  up 
over  the  clavicle  to  open  into  the  external  jugular  ;  and,  finally,  the  fourth  or  adult  stage  is  pro- 
duced from  this  by  the  degeneration  of  that  portion  of  the  cephalic  which  corresponds  to  what 
is  termed  the  jugulo-cephalic. 

The  antibrachial  portion  of  the  cephalic  is  frequently  termed  the  S2iperficial  radial  vein,  the 
accessory  cephalic  being  then  the  accessory  superficial  radial.  Furthermore,  it  is  to  be  noted 
that  quite  frequently  one  or  more  strong  longitudinal  stems  are  developed  in  the  superficial  net- 
work of  the  anterior  surface  of  the  forearm,  and  to  one  of  these  the  term  median  vein  has  been 
applied.  This  condition  has  generally  been  accepted  by  the  English  and  French  anatomists  as 
typical,  and  their  description  of  the  origin  of  the  basilic  and  cephalic  veins  is  as  follows.  The 
median  vein  when  it  reaches  the  bend  of  the  elbow  divides  into  two  divergent  stems  (Fig.  764) 
which  are  termed  the  median  basilic  and  median  cephalic  veins.  The  median  basilic,  which 
corresponds  with  what  has  been  termed  above  the  median  vein,  unites  with  the  superficial  ulnar 
to  form  the  basilic  vein,  while  the  median  cephalic,  which  represents  the  foetal  transverse  branch 
of  the  elbow,  similarly  unites  with  the  superficial  radial  to  form  the  cephalic.  Such  an  arrange- 
ment is  undoubtedly  of  frequent  occurrence  ;  but  since  the  median  vein,  as  understood  in  such  a 
description,  is  so  variable  and  so  manifestly  a  secondary  formation,  and  since  the  arrangement 
taken  above  as  typical  is  not  only  also  of  frequent  occurrence,  but  furthermore  follows  more 
closely  the  embryonic  relations  of  the  various  vessels,  it  has  been  given  the  preference. 

Practical  Considerations.— The  Veins  of  the  Upper  Extremity. 

The  Deep  Veins. — The  venae  comites  of  the  radial  artery  have  been  said, 
when  distended,  to  alter,  by  pressure,  the  character  of  the  pulse.  The  numerous 
short  anastomotic  branches  which  unite  the  venae  comites  of  the  brachial  artery 
cross  in  front  of  that  vessel  and  may  have  to  be  tied  as  a  preliminary  to  ligation 
of  the  artery. 

The  Superficial  Veins. —  The  Hand. — The  veins  of  the  dorsal  surface  are 
subcutaneous,  prominent,  and,  in  order  that  the  circulation  may  not  be  inter- 
rupted during  prehension,  are  much  larger  than  those  of  the  palmar  surface.  Like 
the  other  superficial  veins  of  the  upper  extremity,  they  are  scantily  supplied  with 
valves  and  are  therefore  easily  distended  by  the  effects  of  gravity  or  by  any  constric- 
tion of  the  limb  above. 

The  Forearm. — The  large  size  of  the  superficial  veins  in  the  forearm,  their  sub- 
cutaneous position,  the  small  number  of  valves  they  contain,  and  the  fact  that  most 


HUMAN    ANATOMY. 


of  the  venous  blood  of  the  limb  is  returned  by  them,  make  circular  constriction  of 
the  arm  or  forearm — as  in  cases  of  poorly  applied  splints — especially  dangerous. 
Swelling  and  cedema  distal  to  the  constriction  are  sure  to  result  speedily  and,  if  the 
pressure  is  continued,  to  be  followed  by  ulceration  or  gangrene. 

On  the  extensor  surface  of  the  forearm  the  superficial  veins  are  less  conspicuous 
than  on  the  flexor,  and  between  the  olecranon  and  the  level  of  the  pronator  teres 
insertion  are  almost  completely  lacking.  This  is  the  surface  most  exposed  to  trau- 
matism, and  along  it  main  arteries  and  nerve-trunks  are  also  absent. 

The  Elbow. — The  vein  given  off  by  the  median  vein  when  it  reaches  the  bend  of 
the  elbow,  and  known  by  the  English  and  French  anatomists  {vide  supra)  as  the 
median  basilic,  is  of  the  greatest  practical  importance  among  the  veins  at  the  bend  of 
the  elbow.  The  M-like  figure  made  by  the  superficial  ulnar  and  superficial  radial  in 
uniting  respectively  with  the  median  basilic  and  median  cephalic  to  form  the  basilic 

and    cephalic   veins     is    by 
Fig.  764.  no    means    constant,    but   is 

present  in  only  from  one-half 
to  two-thirds  of  all  cases 
(Treves).  Even,  however, 
if  the  basilic  and  cephalic 
veins  do  not  originate  in 
this  way,  the  median  vein 
(if  from  the  cephalic),  the 
median  basilic  (if  from  the 
median) ,  will  be  found  begin- 
ning a  short  distance  below 
the  elbow,  to  the  outer  side 
of  the  biceps  tendons,  and 
crossing  the  tendon,  the 
brachial  artery,  the  brachial 
veins,  and  the  median  nerve, 
from  all  of  which  it  is 
separated  by  the  bicipital 
aponeurosis,  the  inner  of  the 
two  lower  biceps  tendons  of 
the  old  anatomists.  The 
vein  may,  however,  run 
either  more  transversely  or 
more  vertically  and  so  have 
different  relations  to  the 
artery  and  nerve  ;  it  is 
usually  the  largest  of  the 
anticubital  veins,  but  may 
be  smaller  than  the  median 
cephalic,  which  is  commonly  the  second  in  size,  followed  by  the  median,  ulnar,  and 
radial,  in  the  order  mentioned. 

For  reasons  explained  above,  abnormalities  and  even  absence  of  the  cephalic 
and  radial  veins  are  more  frequent  than  those  of  the  basilic. 

For  this  reason,  and  on  account  of  its  large  size,  the  greater  quantity  of  blood 
it  carries — as  it  is  above  the  entrance  of  the  deep  median  vein,  and  thus  receives 
blood  from  the  deep  veins  of  the  forearm — its  superficial  position,  its  prominence, 
and  its  relative  fixation  to  the  bicipital  fascia  by  cellular  tissue,  the  median  basilic  is 
the  vein  selected  for  either  intravenous  transfusion  or  phlebotomy.  In  opening  the 
vein,  certain  dangers  are  to  be  avoided:  (1)  Wound  of  the  brachial  artery,  if  it 
results  in  a  direct  communication  between  the  vein  and  artery,  will  cause  an  aneu- 
rismal  varix  ;  if  it  results  in  the  formation  of  an  intervening  sac  in  the  perivascular 
connective  tissue,  through  which  the  blood  from  the  artery  flows  before  entering  the 
vein,  it  will  cause  a  varicose  aneurism.  (2)  A  septic  wound  may  cause  a  lymphan- 
gitis from  infection  of  the  lymph-vessels  accompanying  the  vein,  and  may  result  in 
axilary  abscess.       (3)   Unnecessary  damage  to   the  filaments  of  the  internal   cuta- 


THE   AZYGOS   SYSTEM.  893 

neous  nerve  (lying  in  front  of  the  vein)  may  give  rise  to  chronic  traumatic  neuritis 
(Tillaux),  while  injury  of  the  cutaneous  branches  of  the  musculo-cutaneous  nerve 
(in  closer  relation  to  the  median  cephalic  vein),  or  entanglement  of  those  branches 
in  the  cicatrix,  may,  by  reflex  irritation  acting  through  the  motor  fibres,  cause  tonic 
spasm  of  the  biceps  and  brachialis  anticus,   "bent  arm"  (Hilton). 

The  Arm. — The  cephalic  vein  and  its  anomalies  should  be  studied  in  relation 
to  ligation  of  the  axillary  artery  {q.v. ),  the  first  portion  of  which  it  crosses  (sepa- 
rated from  it  by  the  clavi-pectoral  fascia),  on  its  way  to  reach  the  axillary  vein. 

It  may  be  remembered  that  the  basilic  vein  pierces  the  brachial  aponeurosis  a 
little  below  the  middle  of  the  arm  and  ceases  to  be  superficial. 

THE   AZYGOS    SYSTEM. 

The  principal  trunks  of  the  azygos  system  of  veins  are  persistent  portions  of 
the  embryonic  cardinal  veins  which  drained  the  thoracic  and  abdominal  walls,  as  well 
as  the  paired  viscera  of  the  abdomen,  and  united  above  with  the  jugular  trunks  to 
form  the  Cuvierian  ducts  (page  926).  On  the  development  of  the  inferior  vena 
cava  their  importance  diminished  greatly,  and  in  the  adult  they  serve  principally  to 
collect  the  blood  from  the  intercostal  spaces.  The  reduction  of  the  lower  part  of  the 
left  jugular  vein  (page  927)  brought  about  further  modifications  of  the  left  cardinal, 
its  original  connection  with  the  left  jugular  being  dissolved  and  a  new  one  formed 
with  the  right  cardinal.  This  latter  vein  forms  what  is  termed  the  azygos  vein  of  the 
adult,  while  what  persists  of  the  left  one  is  known  as  the  hemiazygos  and  accessory 
hemiazygos. 

The  Azygos  Vein. 

The  azygos  vein  (v.  azygos)  (Fig.  765),  sometimes  called  the  azygos  major, 
begins  immediately  below  the  diaphragm,  where  it  is  directly  continuous  with  the  right 
ascending  lumbar  vein,  formed  by  the  anastomosis  of  branches  of  the  lumbar  veins  and 
connecting  below  with  the  ilio-lumbar  or  common  iliac.  The  azygos  vein  passes  up- 
ward into  the  thoracic  cavity,  traversing  the  diaphragm  either  by  the  cleft  between  the 
medial  and  intermediate  portions  of  the  right  crus  or  else  by  the  aortic  opening.  It 
then  continues  its  way  upward  in  the  posterior  mediastinum,  resting  upon  the  ante- 
rior surfaces  of  the  bodies  of  the  thoracic  vertebrae  a  little  to  the  right  of  the  middle 
line,  passing  over  the  right  intercostal  arteries  and  having  the  thoracic  aorta  and  the 
thoracic  duct  immediately  to  the  left  of  it.  When  it  reaches  the  level  of  the  fourth 
vertebra  it  bends  forward  and  somewhat  to  the  right,  and,  curving  over  the  right 
bronchus  and  the  right  pulmonary  artery,  it  descends  slightly  to  open  into  the  pos- 
terior surface  of  the  superior  vena  cava,  just  above  the  level  at  which  that  vessel 
becomes  invested  by  the  pericardium.  The  terminal  portion  of  the  vein  from  the 
fourth  vertebra  onward  is  sometimes  termed  the  azygos  arch. 

The  azygos  vein  in  a  considerable  proportion  (22  per  cent.,  Gruber)  of  cases  is 
entirely  destitute  of  valves,  and  when  present  they  rarely  exceed  four  in  number,  are, 
apparently,  never  exactly  paired,  and  are  usually  insufficient.  They  occur  more  fre- 
quently in  the  arch  than  in  the  vertical  portion  of  the  vein. 

Tributaries. — The  azygos  vein  at  its  origin  has  usually  some  small  connections 
with  the  vena  cava  inferior,  but  its  principal  tributaries  are  the  right  intercostal  veins. 
In  addition  it  receives  branches  from  the  oesophagus  (vv.  oesophageae),  from  the  are- 
olar tissue  and  lymph-nodes  of  the  posterior  mediastinum  and  from  a  plexus  which 
surrounds  the  thoracic  aorta,  from  the  posterior  surface  of  the  pericardium,  and  from 
the  substance  of  the  right  lung,  these  last  bronchial  veins  (vv.  bronchiales  posteri- 
ores)  issuing  from  the  hilum  of  the  lung  and  opening  into  the  azygos  at  the  beginning 
of  its  arch.  They  anastomose  with  the  pulmonary  veins  both  along  the  course  of  the 
smaller  bronchi  and  also  outside  the  lung,  and  they  receive  some  smaller  bronchial 
veins  (vv.  bronchiales  anteriores)  situated  upon  the  anterior  surface  of  the  bronchi. 
The  azygos  vein  furthermore  receives  the  hemiazygos  vein  ;  this  and  the  intercostal 
veins  will  be  described  below. 

Variations. — Since  the  cardinal  veins,  from  which  the  azygos  and  hemiazygos  are  formed, 
are  primarily  symmetrical,  it  may  happen,  just  as  was  the  case  with  the  aortic  arches,  that  it  is 
the  left  one  that  is  more  fully  retained  and  therefore  becomes  the  azygos  vein,  the  right  becoming 


»94 


HUMAN    ANATOMY. 


Fig.  765. 


Internal  jugular 
Right  vertebral 

Right  subclavian 

Right  innominate 

Right  inferior  thyroid 

Right  internal  mammary 


Branch  of 

ena  azygos 
Ascending  lumbar  vein 


Portion  of  posterior  body-wall,  showing  azvgos  veins,  superior  and  inferior 
vena  cava,  and  their  tributaries. 


THE  AZYGOS   SYSTEM.  895 

the  hemiazygos.  Occasionally,  instead  of  opening  into  the  superior  vena  cava,  the  azygos 
terminates  in  the  right  subclavian,  the  right  innominate  vein,  or  even  opens  directly  into  the  right 
auricle.  A  further  anomaly  is  sometimes  presented  by  the  azygos,  in  its  upper  part,  being  situated 
at  the  bottom  of  a  deep  groove  upon  the  surface  of  the  right  lung,  which  thus  comes  to  have  an 
accessory  lobe  known  as  the  azygos  lobe  or  lobule. 

Practical  Considerations. — The  azygos  veins  are  the  connecting  links  be- 
tween the  cardinal  and  the  inferior  caval  systems.  In  cases  of  obstruction  of  the 
inferior  cava  they  are  able  to  carry  on  the  collateral  circulation  very  effectively, 
through  their  communication  with  the  common  iliac,  renal,  lumbar,  and  ilio-lumbar 
veins.  Growths  in  the  posterior  mediastinum,  enlarged  bronchial  glands,  or  aortic 
aneurisms  may  so  compress  these  veins  as  to  cause  cedema  of  the  chest  wall  by 
interference  with  the  intercostal  veins  which  empty  into  them. 

The  Hemiazygos  Vein. 

The  hemiazygos  vein  (v.  hemiazygos)  (Fig.  765),  also  called  the  azygos  minor 
inferior,  is  the  counterpart,  on  the  left  side  of  the  body,  of  the  lower  part  of  the  azygos. 
It  arises  just  below  the  diaphragm  as  the  continuation  upward  of  the  left  ascending 
lumbar  vein  (page  901),  also  receiving  usually  a  communicating  branch  from  the  left 
renal  vein.  It  passes  upward  into  the  thorax  between  the  medial  and  intermediate 
portions  of  the  left  crus  of  the  diaphragm,  and  then  ascends  upon  the  left  side  of  the 
bodies  of  the  lower  thoracic  vertebrae,  passing  in  front  of  the  lower  left  intercostal 
arteries  and  having  the  thoracic  aorta  to  its  right.  At  about  the  level  of  the  eighth 
or  ninth  vertebra  it  bends  towards  the  right  and,  passing  behind  the  aorta  and  the 
cesophagus,  opens  into  the  azygos  vein. 

In  its  course  it  receives  the  lower  five  or  four  left  intercostal  veins,  which  con- 
stitute its  principal  tributaries,  and  in  some  cases  it  also  receives  the  accessory  hemi- 
azygos vein.  It  also  receives  some  branches  from  the  cesophagus  and  from  the 
posterior  mediastinum. 

The  Accessory  Hemiazygos  Vein. 

The  accessory  hemiazygos  vein  (v.  hemiazygos  accessoria)  (Fig.  765),  also  called 
the  azygos  mitior  superior,  is  a  descending  stem  which  lies  upon  the  left  side  of  the 
bodies  of  the  upper  thoracic  vertebrae  and  receives  the  upper  left  intercostal  veins.  It 
begins  above  at  about  the  second  intercostal  space  by  the  union  of  a  small  vein,  which 
connects  it  with  the  left  innominate,  with  the  left  superior  intercostal.  When  it  has 
reached  the  level  of  the  seventh  or  eighth  thoracic  vertebra  it  bends  to  the  right  and, 
passing  beneath  the  aorta  and  the  cesophagus,  opens  into  the  azygos  vein.  Quite 
frequently  it  opens  below  into  the  hemiazygos  just  as  that  vein  bends  towards  the 
right,  and  even  when  it  has  an  independent  connection  with  the  azygos  it  may  be 
connected  with  the  hemiazygos  by  an  anastomotic  branch. 

It  receives  the  upper  seven  or  eight  left  intercostal  veins  and  in  addition  the  left 
posterior  bronchial  vein. 

Variations. — The  hemiazygos  and  accessory  hemiazygos  veins  together  represent  the  left 
cardinal  vein  of  the  embryo  which  primarily  opened  into  the  left  Cuvierian  duct.  With  the  dis- 
appearance of  the  lower  part  of  the  left  jugular  vein  the  relations  of  the  left  cardinal  change, 
the  vein  making  a  connection  across  the  middle  line  with  the  right  cardinal  (the  azygos).  Indi- 
cations of  the  original  condition  are  occasionally  seen  in  a  fibrous  cord  which  connects  the  left 
superior  intercostal  vein,  which  is  strictly  a  portion  of  the  accessory  hemiazygos,  with  the 
oblique  vein  of  the  left  auricle  (page  856). 

As  already  pointed  out  in  speaking  of  variations  of  the  azygos,  cases  have  been  observed 
in  which  the  hemiazygos  and  accessory  hemiazygos  occur  upon  the  right  side  of  the  body,  being 
formed  from  the  right  cardinal,  while  the  left  cardinal  gives  rise  to  the  azygos.  And  more 
rarely  the  two  veins  have  been  observed  fused  to  form  a  single  trunk  lying  upon  the  anterior 
surface  of  the  thoracic  vertebra?  and  receiving  all  the  intercostal  arteries. 

A  considerable  amount  of  variation  exists  in  the  number  of  intercostal  veins  received  by  the 
hemiazygos  and  the  accessory  hemiazygos  respectively.  Usually  they  divide  between  them  the 
inrercostals,  since  they  either  unite  or  cross  the  median  line  to  the  azygos  over  successive 
vertebrae.  The  hemiazygos  has  been  observed  to  cross  the  vertebral  column  anywhere  from  the 
sixth  to  the  eleventh  vertebra,  and  the  accessory  may  descend  as  far  as  the  tenth  or  may  cross  at 
the  third.     In  cases  where  it  makes  its  crossing  high  up  a  number  of  intercostal  spaces  may  inter- 


896  HUMAN    ANATOMY. 

vene  between  it  and  the  hemiazygos,  and  the  veins  of  these  then  open  directly  into  the  azygos, 
passing,  each  independently,  across  the  vertebral  column  beneath  the  aorta  and  oesophagus. 
Absence  of  the  accessory  hemiazygos  has  been  observed,  the  upper  six  or  eight  inter- 
costal veins  uniting  to  form  a  common  ascending  trunk  which  opens  into  the  left  innominate. 
In  all  probability,  however,  this  common  ascending  stem  is  properly  to  be  regarded  as  the 
accessory  hemiazygos,  whose  normal  connection  with  the  innominate  has  increased  in  size  while 
its  connection  with  the  azygos  or  hemiazygos  has  either  degenerated  or  failed  to  form. 

The  Intercostal  Veins. 

The  intercostal  veins  (w.  intercostales)  (Fig.  765),  sometimes  designated  as 
posterior  intercostal  as  distinguished  from  the  anterior  intercostal  tributaries  of  the 
internal  mammary  vein,  accompany  the  intercostal  arteries  and  are  twelve  in  number 
on  each  side,  one  occurring  in  each  intercostal  space  and  one,  sometimes  termed  the 
subcostal  vein,  running  along  the  lower  border  of  each  twelfth  rib.  They  lie  along 
the  upper  border  of  the  spaces  to  which  they  belong,  in  a  groove  on  the  lower  border 
of  the  rib,  and  are  above  the  corresponding  arteries.  The  upper  nine  or  ten  veins 
open  anteriorly  into  the  internal  mammary  or  musculo-phrenic  veins,  but  the  lower 
three  or  two,  which  are  somewhat  larger  than  the  rest,  have  no  anterior  communica- 
tion and  receive  tributaries  from  the  abdominal  muscles  and  the  diaphragm.  In  the 
middle  portion  of  their  course  the  upper  six  or  seven  veins  give  off  branches,  the 
costo-axillary  veins,  which  ascend  towards  the  axilla  and  open  into  either  the  long 
thoracic  or  the  thoraco-epigastric  vein  and  so  into  the  axillary,  and,  as  it  approaches 
the  vertebral  column  behind,  each  vein  receives  a  dorsal  branch  (ramus  dorsalis)  which 
accompanies  the  spinal  branch  of  the  intercostal  artery  and  returns  the  blood  from  the 
skin  and  muscles  of  the  back  and  also  from  the  spinal  column  and  its  contents,  this 
latter  drainage  being  by  means  of  a  spinal  branch  (ramus  spinalis)  which  connects 
with  the  intervertebral  veins  (page  898). 

Their  posterior  termination  varies  considerably  in  different  individuals,  especially 
as  regards  the  upper  members  of  the  series.  It  may  be  supposed  that  primarily  all 
the  intercostal  veins  of  the  right  side  opened  into  the  azygos  vein  and  all  of  those  of 
the  left  side  into  the  hemiazygos  or  accessory  hemiazygos,  and  this  condition  holds 
in  the  adult  with  all  but  the  upper  two  or  three  veins.  On  the  right  side  the  vein 
of  the  first  space — that  of  the  second  space  sometimes  uniting  with  it — frequently 
accompanies  the  superior  intercostal  artery  as  a  right  superior  intercostal  vein, 
and  opens  above  into  either  the  right  innominate  or  one  of  its  branches,  usually  the 
vertebral ;  on  the  left  side  the  vein  of  the  first  space  opens  into  the  left  innominate  vein, 
being  sometimes  termed  the  accessory  left  superior  intercostal  vein,  while  the 
veins  of  the  second,  third,  and  sometimes  the  fourth  spaces  unite  to  a  common  trunk 
which  crosses  the  arch  of  the  aorta  and  opens  into  the  left  innominate  vein,  forming 
the  left  superior  intercostal  vein.  It  is  to  be  noted  that  this  last  is  connected 
with  the  accessory  hemiazygos  vein  and  really  represents,  in  part  at  least,  its  upper 
portion, — a  fact  which  is  all  the  more  evident  from  its  frequent  connection  by  means 
of  a  fibrous  cord  with  the  oblique  vein  of  the  left  auricle  ;  and,  furthermore,  it  may 
also  be  pointed  out  that  the  veins  of  the  second,  third,  and  sometimes  the  fourth  spaces 
of  the  right  side  usually  unite  to  a  common  trunk  which  opens  into  the  azygos 
vein. 

The  principal  tributaries  and  connections  of  the  intercostal  veins  have  already 
been  mentioned,  but  there  remain  to  be  described  the  interesting  arrangement  shown 
by  the  valves  in  those  veins  which  connect  anteriorly  with  the  internal  mammary  or 
musculo-phrenic  veins.  So  far  as  this  arrangement  is  concerned,  each  vein  may  be 
regarded  as  consisting  of  three  portions  :  (1)  an  anterior  portion,  in  which  the  con- 
cavities of  the  valves  look  towards  the  internal  mammary  or  musculo-phrenic  veins  ; 
(2)  a  posterior  portion,  in  which  the  valves  look  towards  the  azygos  or  hemiazygos 
veins  ;  and  (3)  an  intermediate  portion,  which  is  destitute  of  valves.  As  a  result  of 
this  arrangement  the  blood  of  the  anterior  portion  of  each  vein  must  pass  to  the  internal 
mammary  veins  (page  860),  that  of  the  posterior  portion  to  the  azygos  or  hemiazygos, 
while  in  the  intermediate  portion  it  may  pass  in  either  direction.  But  it  is  with  this 
intermediate  portion  that  the  costo-axillary  veins  are  connected,  so  that  in  the  upper 
six  or  seven  veins,  in  addition  to  passing  partly  anteriorly  and  partly  posteriorly,  some 
of  the  blood  takes  an  ascending  direction  and  empties  into  the  axillary  vein. 


THE   AZYGOS   SYSTEM.  897 

In  the  two  or  three  lower  veins  there  is  no  such  double  flow,  the  valves  all 
looking  towards  the  azygos  veins.  Valves  occur  at  the  opening  of  practically  all  the 
intercostals  into  the  azygos  veins,  the  last  intercostal  forming  an  exception  to  this 
rule,  and,  furthermore,  the  valves  of  the  lower  veins  are  apt  to  be  insufficient. 

The  Spinal  Veins. 

The  spinal  veins,  which  return  the  blood  from  the  vertebral  column  and  the 
adjacent  muscles  and  also  from  the  membranes  enclosing  the  spinal  cord,  present  in  a 
high  degree  the  plexiform  arrangement  which  is  characteristic  of  the  veins  as  com- 
pared with  the  arteries.  They  form  a  series  of  longitudinal  plexuses  which  extend 
practically  the  entire  length  of  the  spinal  column,  communicating  extensively  with  one 
another,  and  may  be  divided  primarily  into  those  which  lie  external  to  the  spinal 
canal  and  those  which  lie  within  the  canal. 

The  external  spinal  plexuses  (plexus  venosi  vertebrates  externi)  are  two  in 
number,  anterior  and  posterior.  The  anterior  external  plexus  (plexus  venosus 
vertebralis  anterior)  rests  upon  the  anterior  surfaces  of  the  bodies  of  the  vertebrae, 
and  presents  considerable  differences  in  the  amount  of  its  complexity  in  different 
portions  of  the  spinal  column.  In  the  thoracic  and  lumbar  regions  it  forms  a  net- 
work with  large  meshes,  in  the  sacral  region  it  is  represented  by  transverse  anasto- 
moses between  the  lateral  and  middle  sacral  veins,  and  in  the  cervical  region  it  reaches 
its  greatest  degree  of  complexity,  forming  a  close  net-work,  especially  dense  above 
and  resting  partly  upon  the  bodies  of  the  vertebrae  and  partly  upon  the  longus  colli 
muscles.  At  each  intervertebral  foramen  the  plexus  communicates  with  the  veins 
issuing  from  the  internal  spinal  plexuses  and  also  with  the  posterior  external  plexus, 
and  in  addition  sends  branches  to  the  vertebral  veins  in  the  cervical  region  and  to 
the  rami  spinales  of  the  intercostal  and  lumbar  veins  in  the  corresponding  regions. 

The  posterior  external  plexuses  (plexus  venosi  vertebrates  posteriores)  lie  partly 
upon  the  posterior  surfaces  of  the  laminae  of  the  vertebrae  and  the  ligamenta  subflava 
and  partly  between  the  deeper  dorsal  muscles.  As  in  the  case  of  the  anterior  plexus, 
they  are  more  complicated  in  the  cervical  than  in  the  thoracic  and  lumbar  regions. 
In  the  latter  their  meshes  are  somewhat  elongated  longitudinally,  and  they  communi- 
cate with  the  internal  plexuses  at  the  intervertebral  foramina  and  also  by  branches 
which  traverse  the  ligamenta  subflava,  and  they  have  further  communications  with 
the  anterior  external  plexus  and  with  the  spinal  rami  of  the  intercostal  and  lumbar 
veins.  In  the  cervical  region,  in  correspondence  with  the  greater  differentiation  of 
the  dorsal  musculature,  the  plexuses  become  divided  into  several  layers,  and  in  the 
region  between  the  occiput  and  the  axis  vertebra  their  deep  layers  form  an  especially 
dense  net-work,  the  suboccipital  plexus,  with  which  the  occipital,  vertebral,  deep 
cervical,  and  posterior  external  jugular  veins  communicate.  Throughout  its  course 
the  cervical  portion  of  the  plexus  communicates  with  the  internal  and  anterior  ex- 
ternal plexuses  and  also  with  the  vertebral  vein. 

The  internal  spinal  plexuses  (plexus  venosi  vertebrates  interni)  are  situated  in 
the  dura  mater  lining  the  spinal  canal  and  are  much  closer  than  the  external  plexuses. 
The  veins  which  form  them  have  a  general  longitudinal  direction  and  anastomose 
abundantly,  but  nevertheless  four  subordinate  longitudinal  lines  of  vessels  can  be 
recognized,  two  of  which  are  upon  the  anterior  wall  of  the  spinal  canal  and  two  upon 
the  posterior  wall. 

The  anterior  internal  plexuses  lie  one  on  each  side  of  the  median  line  on  the 
posterior  surfaces  of  the  bodies  of  the  vertebrae  and  the  intervertebral  disks,  from  the 
foramen  magnum  to  the  sacral  region.  They  are  composed  of  rather  large  veins, 
between  which  are  frequent  anastomoses,  and  transverse  connecting  vessels  run  across 
the  body  of  each  vertebra  between  the  two  plexuses,  passing  beneath  the  posterior 
common  vertebral  ligament.  Into  these  transverse  connections  open  the  bashwtebral 
veins  (w.  basivertebrales)  which  return  the  blood  from  the  bodies  of  the  vertebrae, 
traversing  these  to  a  certain  extent  to  communicate  with  the  anterior  external  plexus. 
The  anterior  internal  plexuses  also  communicate  opposite  each  vertebra  with  the  pos- 
terior internal  plexuses,  rings  of  anastomosing  veins  thus  surrounding  the  spinal  canal 
opposite  each  vertebra  and  constituting  what  are  termed  the  retia  venosa  vertebrarum. 

57 


898  HUMAN    ANATOMY. 

The  posterior  internal  plexuses  are  situated  one  on  either  side  of  the  median  line 
on  the  anterior  surfaces  of  the  laminse  and  on  the  ligamenta  subflava,  through  which 
they  send  branches  to  communicate  with  the  posterior  external  plexus.  They  are 
connected  by  transverse  plexuses  which  complete  the  retia  venosa  vertebrarum,  and 
are  composed  of  smaller  vessels  than  the  anterior  plexuses,  and  the  net-work  which 
they  form  is  more  open. 

Laterally,  at  each  intervertebral  foramen  the  internal  plexuses  send  branches  out 
from  the  spinal  canal  along  the  nerve-trunks,  and  by  means  of  these  intervertebral 
veins  (w.  intervertebrales),  which  have  the  form  of  plexuses  at  their  origin  and  receive 
communicating  branches  from  the  external  vertebral  plexuses  and  from  the  veins  of  the 
spinal  cord,  the  internal  plexuses  pour  their  blood  into  the  vertebral,  intercostal,  lum- 
bar, and  lateral  sacral  veins,  the  connection  with  the  intercostals  being  through  their  rami 
spinales.  Above,  the  internal  plexuses  form  an  especially  rich  rete  or  plexus  around 
the  foramen  magnum  and  communicate  with  the  occipital,  marginal,  and  basilar  sinuses. 

Practical  Considerations. — The  posterior  external  spinal  plexuses,  by  means 
of  their  communication  through  the  intervertebral  foramina  and  the  ligamenta  sub- 
flava with  the  internal  plexuses,  may  convey  infection  from  without — septic  wounds 
of  the  back,  severe  bed-sores,  osteitis  of  the  vertebral  laminae — to  the  interior  of  the 
spinal  canal.  External  pachymeningitis  has  thus  originated.  In  operations  upon 
the  spine,  these  veins  bleed  so  freely  that  it  is  often  well  after  severing  them  upon 
one  side  to  control  them  by  packing  and  proceed  to  the  exposure  of  the  spine  on 
the  opposite  side,  repeating  the  packing  there.  The  internal  plexuses,  interposed 
between  the  theca  of  the  cord  and  the  interior  walls  of  the  vertebral  column,  may, 
as  a  result  of  trauma,  furnish  blood  enough  to  cause  compression  of  the  cord.  The 
symptoms  are  usually  relatively  slow  in  developing — as  compared  with  those  due  to 
injury  to  the  cord  itself  or  to  its  vessels — and  are  referable  mainly  to  the  lower  spinal 
segments,  the  blood  gravitating  to  that  portion  of  the  canal. 

Hemorrhage  may  occur  within  the  membranes  (haematorrhacis),  when  the 
blood  will  likewise  tend  to  gravitate  toward  the  lower  end  of  the  cord,  and,  unless 
in  large  amount,  may  cause  no  definitely  localizing  symptoms.  Bleeding  from  the 
venae  medulli  spinales  may  take  place  into  the  substance  of  the  cord  (hasmato- 
myelia),  and  is  most  likely  to  occur  in  the  segments  from  the  fourth  cervical  to  the 
first  dorsal  (Thorburn),  because  of  the  degree  of  motion  of  that  portion  of  the  spine, 
the  union  toward  its  base  of  a  fixed  and  a  movable  segment,  and  the  frequency  with 
which  forces  causing  excessive  flexion  or  over- extension  are  applied  to  the  head. 
If  the  lesion  causes  compression  only,  the  paralysis,  anaesthesia,  etc. ,  will  be  only 
temporary.     If  it  is  associated  with  disorganization  of  the  cord,  they  will  be  permanent. 

The  Veins  of  the  Spinal  Cord. 

The  veins  of  the  spinal  cord  (w.  medulli  spinales)  occur  as  six  longitudinal  stems 
situated  upon  the  surface  of  the  cord  and  connected  by  a  fine  net -work  very  much  as 
are  the  arteries.  One  of  these  stems  traverses  the  entire  length  of  the  cord  along  the 
line  of  the  anterior  median  fissure,  and  has  on  either  side  of  it  another  stem  which 
lies  immediately  posterior  to  the  line  of  exit  of  the  anterior  nerve-roots.  These  three 
stems  together  form  the  anterior  medulli-spinal  veins  (w.  spinales  externae 
anteriores).  The  posterior  veins  (w.  spinales  externae  posteriores)  have  a  similar 
arrangement,  one  lying  along  the  line  of  the  posterior  longitudinal  fissure  and  one 
posterior  to  each  of  the  lines  of  entrance  of  the  posterior  nerve-roots. 

All  these  stems,  together  with  the  plexus  which  connects  them,  lie  in  the  pia 
mater  and  receive  branches  (w.  spinales  internae)  from  the  substance  of  the  cord. 
From  them  branches  pass  out  along  the  nerve-roots  to  join  the  intervertebral  veins, 
and  at  the  upper  extremity  of  the  cord  they  join  the  veins  of  the  medulla  oblongata. 

THE  INFERIOR  CAVAL  SYSTEM. 

The  inferior  caval  system  includes  all  the  veins  from  the  body-wall  below  the 
level  of  the  diaphragm  ;  those  from  the  abdominal  and  pelvic  cavities,  with  the 
exception  of  those  from  the  stomach,  intestines  (except  the  lower  part  of  the  rectum), 


THE    INFERIOR    CAVAL    SYSTEM. 


899 


pancreas,  and  spleen  ;   and  those  from  the  lower  limb.      It  receives  its  name  from  its 
principal  vessel,  the  inferior  vena  cava,  which  conveys  its  blood  to  the  right  auricle. 

The  Inferior  Vena  Cava. 

The  inferior  or  ascending  vena  cava  (vena  cava  inferior)  (Figs.  765,  766)  is  formed 
by  the  union  of  the  two  common  iliac  veins  either  on  the  right  side  of  the  intervertebral 
disk  separating  the  fourth  and  fifth  lumbar  vertebrae  or  on  the  right  side  of  the  fifth 
lumbar  vertebra.      From  this  point  it  ascends  directly  upward  to  the  level  of  the  first 


Hepatic  veins 


Fig.  766. 


C  celiac  axis 

Superior  mesenteric  artery- 
Left  suprarenal 
body 


Right  suprarenal 
body 


Left  kidney 
Left  renal  artery 


Inferior  mesen- 
teric artery 
Left  ureter 

Quadratus 

lumborum 
Left  spermatic 

artery 
Common  iliac 

artery 
Common  iliac 

vein 

Psoas  magnus 


Left  ureter, 
pelvic  portion 


Rectum  (cut) 


— I  Vas  deferens 


lumbar  vertebra  and  there  begins  to  bend  slightly  to  the  right  to  reach  the  fissure 
of  the  liver  which  separates  the  Spigelian  and  right  lobes.  Passing  upward  in  this 
fissure,  it  reaches  the  diaphragm  and  perforates  the  left  lobe  of  the  centrum  tendineum 
of  that  structure,  so  entering  the  cavity  of  the  thorax,  then  bends  slightly  forward  and 
to  the  left,  and  opens  into  the  lower  and  back  part  of  the  right  auricle  of  the  heart. 
It  is  the  largest  vein  of  the  body,  measuring  at  its  entrance  into  the  auricle  about 
33  mm.  in  diameter.  It  increases  in  size  from  below  upward  with  the  accession  of  its 
various  tributaries,  somewhat  sudden  increases  succeeding  the  entrance  into  it  of  its 
largest  tributaries,  the  renal  and  hepatic  veins.  It  contains  no  valves,  unless  the 
Eustachian  valve  guarding  its  entrance  into  the  auricle  be  regarded  as  belonging  to  it. 


9oo  HUMAN   ANATOMY. 

Relations. — For  convenience  in  description  the  vena  cava  inferior  may  be 
regarded  as  consisting  of  an  abdominal  and  a  thoracic  portion.  The  former,  which 
constitutes  by  far  the  greater  part  of  its  length,  has  the  following  relations.  Poste- 
riorly it  rests  upon  the  right  side  of  the  lumbar  vertebra?,  upon  the  origins  of  the 
psoas  major  and  minor  muscles,  and  above  upon  the  right  crus  of  the  diaphragm  ; 
it  crosses  in  its  course  the  right  lumbar  and  right  renal  arteries.  Medially  it  is  in 
close  relation  with  the  abdominal  aorta  throughout  the  greater  portion  of  its  course, 
but  separates  from  it  slightly  above,  the  right  crus  of  the  diaphragm  intervening. 
Laterally  it  is  in  contact  with  the  psoas  major  muscle  below,  and  at  about  the  middle 
of  its  course  it  is  in  close  relation  with  the  inner  border  of  the  right  kidney.  Ante- 
riorly it  is  covered  at  its  origin  by  the  right  common  iliac  artery  and  in  the  lower 
part  of  its  course  by  peritoneum.  At  the  level  of  the  third  lumbar  vertebra  it  lies 
beneath  the  third  portion  of  the  duodenum,  and  immediately  above  that  beneath  the 
head  of  the  pancreas  and  the  main  stem  of  the  portal  vein,  which  crosses  it  obliquely. 
Finally,  it  lies  in  the  vena  caval  fissure  of  the  liver,  having  to  the  right  the  right 
lobe  and  to  the  left  the  Spigelian  lobe,  and  being  sometimes  completely  surrounded  by 
liver-tissue,  owing  to  a  thin  portion  of  it  bridging  over  the  fissure.  Throughout  this 
part  of  its  course  it  is  firmly  united  to  the  walls  of  the  fissure  by  fibrous  bands. 

In  its  thoracic  portion,  which  is  quite  short,  measuring  not  more  than  3  cm.  in 
length,  it  is  in  relation  at  first  with  the  right  lung  and  pleura,  and  in  the  upper  part 
is  enclosed  for  about  1.2  cm.  in  the  pericardium. 

Variations. — The  development  of  the  inferior  vena  cava  (page  927)  shows  it  to  be  formed 
by  the  union  of  three  primarily  distinct  structures.  Its  upper  part,  between  the  entrance  of  the 
hepatic  veins  and  the  right  auricle,  is  the  upper  part  of  the  embryonic  ductus  venosus,  then  fol- 
lows a  considerable  portion  derived  from  the  right  subcardinal  vein,  and,  finally,  its  lower  part  is 
formed  from  the  right  cardinal  vein.  Of  these  embryonic  veins  the  ductus  venosus  is  unpaired, 
the  other  two  are  the  right  members  of  paired  veins,  whose  fellows  undergo  almost  complete 
degeneration. 

Anomalies  of  the  vena  cava,  which  are  not  uncommon,  are  for  the  most  part  explicable  as 
a  persistence  or  modification  of  the  embryonic  conditions.  Thus,  that  portion  of  the  vessel  which 
is  formed  from  the  right  subcardinal  and  right  cardinal  may  fail  to  develop,  in  which  case  what 
is  termed  a  persistence  of  the  cardinals  occurs.  Up  to  a  point  above  the  level  of  the  renal  veins 
the  vena  cava  is  represented  by  two  parallel  trunks  lying  one  on  either  side  of  the  aorta,  the  one 
receiving  the  right  common  iliac  vein  and  the  other  the  left.  These  represent  the  abdominal 
portions  of  the  cardinal  veins  or,  in  the  majority  of  cases,  more  probably  the  subcardinals,  and  unite 
above  with  the  unpaired  ductus  venosus,  which  carries  their  blood  to  the  heart.  In  other  words, 
such  cases  are,  as  a  rule,  to  be  regarded  as  a  similar  development  of  both  subcardinal  veins. 

Occasionally,  however,  the  development  of  the  right  subcardinal  to  form  the  vena  cava 
may  proceed  as  usual,  but  it  fails  to  make  a  connection  with  the  ductus  venosus,  one  of  its  con- 
nections with  the  right  cardinal  enlarging  so  that  this  vein  receives  the  caval  blood,  carries  it 
through  the  aortic  opening  of  the  diaphragm,  and,  as  the  azygos  vein,  empties  it  into  the  superior 
vena  cava.  The  hepatic  veins  open  as  usual  into  the  ductus  venosus,  which  passes  to  the  right 
auricle  in  the  normal  manner,  and  the  vena  cava  inferior  is  thus  represented  by  two  distinct  veins, 
the  upper  part  of  the  ductus  venosus.  which  in  such  cases  is  termed  the  common  hepatic  vein  ( v. 
hepatica  communis),  and  the  subcardinal  and  cardinal  portion. 

Another  variation  may  be  produced  by  a  reversal  of  the  roles  of  the  two  subcardinals  in 
forming  the  vena  cava,  the  left  being  the  one  which  develops,  while  the  right  degenerates. 
Such  a  condition  is  found  in  all  cases  of  situs  inversus  viscerum,  but  it  has  also  been  observed 
in  cases  in  which  there  was  otherwise  a  normal  arrangement  of  the  organs.  In  such  cases  the 
vena  cava  in  the  lower  part  of  its  course  lies  to  the  left  of  the  aorta  instead  of  to  the  right,  and  at 
the  level  of  the  renal  arteries  it  crosses  to  the  right  side  in  front  of  the  aorta,  its  further  course 
being  normal.  But  just  as  the  lower  part  of  the  inferior  vena  cava,  when  normally  formed  from 
the  right  subcardinal,  may  fail  to  unite  with  the  ductus  venosus  but  retain  its  primary  connection 
with  the  azygos,  so,  too,  when  formed  from  the  left  subcardinal,  it  may  retain  its  connection  with 
the  hemiazygos  and  drain  through  that  vessel  into  the  azygos  and  so  into  the  superior  vena  cava. 

These  various  cases  include  the  principal  variations  which  occur  in  connection  with  the 
vena  cava  inferior.  It  may  be  pointed  out  that  normally  connections  exist  between  the  azygos 
vein  and  the  vena  cava  below  the  diaphragm  ;  by  means  of  the  ascending  lumbar  veins,  and 
also  by  the  thoracoepigastric  veins,  connection  is  established  between  tributaries  of  the  inferior 
cava  and  the  external  iliac  veins,  and  the  axillary  vein.  By  means  of  these  normally  subordinate 
channels  opportunity  is  afforded  for  the  maintenance  of  the  circulation  in  case  of  obliteration  of 
the  vena  cava. 

Practical  Considerations. — The  inferior  cava  may  be  ruptured  in  severe 
abdominal  injuries,  as  in  the  case  of  a  weight  falling  upon,  or  a  wagon  passing  over, 
the  belly.      The  site  of  rupture  is  most  often  in  the  portion  lying  in  the  hepatic 


THE    INFERIOR   CAVAL   SYSTEM.  901 

Assure.  Its  relation  to  the  right  psoas  major  muscle  has  resulted,  in  cases  of  psoas 
abscess,  in  ulceration  and  opening  of  the  vein,  with  fatal  hemorrhage.  Its  relation 
to  the  inner  border  of  the  right  kidney  has  resulted  in  its  compression  by  a 
movable  kidney,  or  by  a  cancerous  growth  of  the  kidney,  causing  caval  thrombosis, 
a  condition  which  has  also  been  noted  in  connection  with  chronic  nephritis  and 
with  infarction  of  the  renal  parenchyma.  Its  relation  to  the  liver  results,  in 
some  cases  of  hepatic  enlargement,  in  compression  of  the  vena  cava  with  cedema 
of  the  lower  limbs,  and  other  symptoms  of  obstruction.  Its  close  proximity  to 
the  lower  end  of  the  bile-duct  necessitates  caution  in  cutting  operations  for  the 
removal  of  impacted  stones  from  the  duct  (choledochotomy)  (page  1732).  Enlarge- 
ment or  growth  involving  the  head  of  the  pancreas  may  compress  the  cava 
sufficiently  to  cause  obstructive  symptoms,  and  the  nearness  of  the  vein  constitutes 
one  of  the  very  serious  obstacles  to  removal  of  pancreatic  tumors.  In  ureterotomy 
or  other  operation  on  the  right  ureter,  the  close  relationship  of  the  vena  cava  at 
the  point  of  crossing  should  be  remembered.  Thrombosis  of  the  cava,  from 
whatever  cause,  though  it  may  extend  the  entire  length  of  the  vessel,  is  apt  to 
be  limited  to  a  portion  of  the  vessel,  as  that  between  the  renal  veins  and  the 
auricle,  or  that  extending  from  the  iliac  veins  to  the  renal  veins.  The  collateral 
circulation  after  occlusion  ma}'  be  carried  on  through  the  saphenous,  superficial 
abdominal,  spermatic,  pudic,  and  deep  epigastric  veins,  and  the  obturator,  inferior 
mesenteric,  external  mammary,   and  azygos  veins. 

Tributaries. — In  addition  to  the  common  iliac  veins  by  whose  union  it  is 
formed,  the  vena  cava  inferior  receives  a  number  of  tributaries  from  the  abdominal 
walls  and  organs.  These  may  be  arranged  into  two  groups  according  as  they  drain 
the parietes  of  the  abdomen  (radices  parietales)  or  its  viscera  (radices  viscerales).  Of 
the  former  there  are  :  (1.)  the  inferior  phrenic  and  (2)  the  lumbar  veins,  and  of  the 
latter  (3)  the  hepatic,  (4)  the  renal,  (5)  the  suprarenal,  and  (6)  the  spermatic  or 
ovarian  veins. 

1.  The  Inferior  Phrenic  Vein. — The  inferior  phrenic  (v.  phrenica  inferior) 
is  a  paired  vein  which  corresponds  to  the  similarly  named  artery.  It  is  formed  by 
the  union  of  a  number  of  tributaries  which  ramify  upon  the  under  surface  of  the 
diaphragm,  and  opens  into  the  vena  cava  just  before  it  passes  through  the  diaphragm. 
It  receives  tributaries  from  the  upper  portion  of  the  suprarenal  capsule,  and  the  left 
vein,  by  the  enlargement  of  an  anastomosis  of  its  suprarenal  tributaries  with  the 
suprarenal  vein,  may  open  through  the  latter  into  the  left  renal  vein.  The  right 
vein  occasionally  opens  into  the  right  hepatic  vein. 

2.  The  Lumbar  Veins. — The  lumbar  veins  (w.  lumbales)  are  usually  four  in 
number  on  each  side,  and  accompany  the  corresponding  arteries,  lying  above  them. 
They  resemble  closely  in  their  relations  and  tributaries  the  intercostal  veins,  of  which 
they  are  serial  homologues.  Each  vein  arises  in  the  muscles  of  the  abdominal  wall 
and  passes  backward  and  inward  towards  the  vertebral  column,  passing  beneath  the 
psoas  muscle.  Shortly  before  reaching  the  vena  cava  it  receives  a  ramus  dorsalis. 
This  has  its  origin  in  the  dorsal  integument  and  muscles,  communicating  with  the 
posterior  external  spinal  plexus,  and  receives  a  ramus  spinalis  which  communicates 
with  one  of  the  lumbar  intervertebral  veins  and  so  with  the  internal  spinal 
plexuses.  The  veins  then  continue  their  course  towards  the  vena  cava,  those  of  the 
left  side  passing  beneath  the  abdominal  aorta,  and  they  open  into  the  posterior 
surface  of  the  vena  cava. 

As  it  passes  upon  the  lateral  surface  of  its  corresponding  lumbar  vertebra,  each 
of  the  three  lower  veins  is  connected  with  the  one  above  by  an  ascending  stem,  which 
also  places  the  lowest  vein  in  communication  with  the  ilio-lumbar  or  the  common  iliac 
vein,  ■  while  from  the  uppermost  vein  it  is  continued  on  upward  to  join  with  the  azygos 
or  hemiazygos  as  the  case  may  be.  This  ascending  stem  is  the  ascending  lumbar 
vein  (v.  lumbalis  ascendens),  and  is  of  especial  interest  as  forming  an  important 
collateral  channel  between  the  inferior  and  superior  venae  cavas. 

Each  lumbar  vein  possesses  one  or  two  valves  in  its  course,  and  sometimes 
also  valves  at  its  entrance  into  the  vena  cava.  The  concavities  of  these  valves  are 
directed  towards  the  vena  cava,   but  the  valves  are  nearly  always  insufficient  and 


902  HUMAN    ANATOMY. 

consequently  will  not  prevent  a  flow  of  blood  from  the  vena  cava  outward  to  the 
ascending  lumbar  veins  in  cases  of  occlusion  of  the  upper  part  of  the  ve.ia  cava. 

3.  The  Hepatic  Veins. — The  hepatic  veins  (vv.  hepaticae)  (Fig.  765)  return 
the  blood  which  has  been  carried  to  the  liver  both  by  the  hepatic  artery  and 
by  the  portal  vein.  They  are  two  or  three  in  number,  and  are  formed  by  the 
union  of  the  intralobular  veins  of  the  liver  (page  920).  They  emerge  from  the 
substance  of  the  liver  at  the  upper  part  of  the  groove  in  which  the  vena  cava 
lies,  and,  passing  obliquely  upward,  enter  that  vessel  at  an  angle  shortly  before  it 
passes   through  the  diaphragm. 

One  of  the  hepatic  veins  drains  the  substance  of  the  right  lobe  of  the  liver, 
the  other,  when  there  are  but  two,  the  remaining  lobes.  Quite  frequently  this 
second  or  left  vein  is  replaced  by  two  vessels,  one  of  which  drains  the  left 
lobe  alone,  while  the  other  drains  the  Spigelian  and  quadrate  lobes.  Usually, 
in  addition  to  these  principal  veins,  a  varying  number  of  small  hepatic  veins 
occur,  which  make  their  exit  from  the  liver-substance  on  the  walls  of  the  groove 
for  the  vena  cava  and  open  directly  into  that  vessel  without  joining  the  principal 
hepatic  veins. 

The  hepatic  veins  possess  no  valves  in  the  adult,  and  are  characterized  by  the 
thickness  of  their  walls,  which  are  provided  with  both  circular  and  longitudinal 
muscles. 

Variations. — Occasionally  the  right  vein,  more  rarely  the  left,  perforates  the  diaphragm 
and  opens  either  into  the  thoracic  portion  of  the  inferior  vena  cava  or  else  directly  into  the  right 
auricle.  The  two  (or  three)  veins  sometimes  unite  to  a  single  trunk  before  joining  the  vena 
cava,  and  this  trunk  has  been  observed  to  penetrate  the  diaphragm  and  open  directly  into  the 
right  auricle  without  communicating  with  the  vena  cava. 

4.  The  Renal  Veins. — The  renal  veins  (vv.  renales)  (Fig.  766)  are  two  in 
number,  one  returning  the  blood  from  each  kidney.  Each  vein  is  formed  at  the 
hilum,  or  some  little  distance  from  it,  ■  by  the  union  of  from  three  to  five  branches 
which  come  from  the  kidney  substance,  and  is  directed  medially  and  slightly  upward, 
lying  in  front  of  the  corresponding  artery.  On  account  of  the  position  of  the  vena 
cava  to  the  right  of  the  median  line,  the  left  vein  is  somewhat  longer  than  the  right, 
and  passes  in  front  of  the  abdominal  aorta,  just  below  the  origin  of  the  superior 
mesenteric  artery,  to  reach  its  point  of  entrance  into  the  vena  cava,  this  point  being 
usually  a  little  higher  than  that  of  the  right  vein. 

Tributaries. — In  addition  to  the  vessels  by  whose  union  it  is  formed,  each  renal  vein  receives 
(«)  an  inferior  suprarenal  vein  from  the  lower  part  of  the  suprarenal  capsule,  accompanying  the 
corresponding  artery  ;  (d)  adipose  veins,  which  pass  transversely  across  both  surfaces  of  the 
kidney,  taking  their  origin  in  its  adipose  capsule;  (c)  a  ureteric  vein,  frequently  more  or  less 
plexiform  in  structure,  which  returns  the  blood  from  the  upper  part  of  the  ureter,  anastomosing 
below  with  the  ureteric  tributaries  of  the  spermatic  vein.  In  addition,  the  left  renal  vein  receives 
the  left  spermatic  (ovarian)  and  the  left  middle  suprarenal  veins,  both  of  which  will  be 
considered  with  their  fellows  of  the  opposite  side. 

The  adipose  veins  ramifying  in  the  kidney  fat  penetrate  the  renal  fascia  and  so  come 
into  connection  with  the  tributaries  of  the  lumbar  veins,  and  they  also  send  branches  to  the 
spermatic  or  ovarian  veins.  A  more  important  communication  is,  however,  made  through 
a  vein  which  arises  from  the  lower  surface  of  each  renal  and  empties  on  the  right  side 
into  the  first  lumbar  vein,  while  on  the  left  side  it  bifurcates,  sending  one  branch  downward 
to  the  first  lumbar  and  the  other  upward  to  open  into  the  hemiazygos.  Since  valves  occur 
but  rarely  in  the  renal  vein,  and  its  tributaries  are  likewise  either  without  valves  or  with 
insufficient  ones,  the  circulation  of  the  kidney  may  be  maintained  by  means  of  these 
communications  of  the  renal  veins,  even  in  cases  of  obliteration  of  the  vena  cava  inferior  in 
its  upper  portion. 

Variations. — The  renal  veins  are  occasionally  replaced  by  from  two  to  seven  vessels  which 
open  independently  into  the  vena  cava, — a  condition  which  probably  depends  upon  the  failure  of 
the  vessels  from  the  different  portions  of  the  kidneys  to  unite  to  a"  common  stem.  Accessory 
veins,  which  communicate  with  the  vena  cava  below  the  level  of  the  renals  or  even  with  the  com- 
mon iliac,  sometimes  occur,  but  more  rarely  than  the  similar  arteries.  The  left  renal  vein  has 
been  observed  in  several  cases  to  pass  almost  vertically  downward  parallel  to  the  vertebral 
column,  opening  into  the  vena  cava  at  the  level  of  the  fourth  lumbar  vertebra 


THE    INFERIOR    CAVAL    SYSTEM.  903 

5.  The  Middle  Suprarenal  Veins.  —  The  middle  suprarenal  veins  (vv. 
suprarenales)  are  the  principal  veins  of  the  suprarenal  bodies,  from  which,  however, 
the  superior  suprarenals,  emptying  into  the  phrenics,  and  the  inferior,  opening 
into  the  renals,  also  arise.  Each  vein  occupies  a  groove  on  the  anterior  surface 
of  the  suprarenal  body,  and  descends  obliquely  inward  to  open  on  the  right 
side  into  the  inferior  vena  cava  above  the  right  renal,  and  on  the  left  side  into  the 
left  renal. 

6a.  The  Spermatic  Veins. — The  spermatic  veins  (vv.  spermaticae)  begin  at 
the  internal  abdominal  ring,  whence  they  pass  upward  and  inward  along  with  the 
spermatic  arteries  and  are  the  continuation  upward  of  the  venous  plexuses  which 
surround  the  spermatic  cords. 

Each  of  these  plexuses  has  its  origin  in  the  testicular  veins  (vv.  testiculares) 
which  return  the  blood  from  the  tunica  albuginea  testis  and  from  the  seminiferous 
tubules,  these  latter  branches  passing  towards  the  hilum  of  the  organ  in  the  trabecular. 
They  make  their  exit  from  the  testis  at  about  the  middle  of  its  superior  border,  and 
are  joined  very  shortly  by  the  veins  of  the  epididymis.  They  are  then  continued 
up  the  spermatic  cord  in  the  form  of  from  ten  to  twenty  flexuous  stems,  which 
anastomose  abundantly  to  form  what  is  termed  the  pampiniform  plexus  (plexus 
pampiniformis),  surrounding  the  spermatic  artery.  As  the  cord  enters  the  inguinal 
canal  the  plexus  is  reduced  to  some  three  or  four  stems,  which,  at  the  internal 
abdominal  ring,   become  the  spermatic  veins. 

These  are  two  or  three  stems  which  anastomose  abundantly  with  one  another 
and  consequently  present  a  plexiform  arrangement.  They  surround  the  abdominal 
portion  of  the  spermatic  artery  and,  shortly  before  reaching  their  termination,  unite 
to  a  single  stem,  which  on  the  right  side  opens  at  an  acute  angle  into  the  vena  cava 
inferior  below  the  right  renal  vein,  while  on  the  left  side  it  opens  almost  at  a  right 
angle  into  the  lower  border  of  the  left  renal  vein. 

The  spermatic  veins  proper  possess  no  valves,  except  that  there  is  usually 
a  pair  at  the  entrance  of  the  right  vein  into  the  vena  cava.  In  the  stems  of  the 
pampiniform  plexus,  however,  valves  are  usually  to  be  found,  but  they  are  very 
frequently  insufficient. 

Tributaries. — The  spermatic  veins  receive  a  ureteric  branch  from  the  lower  part  of  the 
ureter  and  also  peritoneal  branches  and  renal  branches  from  the  adipose  capsule  of  that  organ. 
In  the  scrotum  the  pampiniform  plexus  makes  connections  with  the  branches  of  the  external  pudic 
veins,  and  at  their  entrance  into  the  external  abdominal  ring  the  two  plexuses  of  opposite  sides 
are  connected  by  transverse  anastomoses  which  pass  in  front  of  the  symphysis  pubis.  A  deeper 
transverse  anastomosis  also  occurs  between  the  two  spermatics  as  they  emerge  from  the  internal 
abdominal  rings,  and  they  communicate  by  means  of  their  peritoneal  branches  with  the  branches 
of  the  right  and  left  colic  veins. 

Variations. — Occasionally  the  left  vein  as  well  as  the  right  opens  directly  into  the  vena  cava, 
and  in  cases  in  which  that  vessel  is  situated  upon  the  left  side  it  is  the  left  vein  which  opens 
directly  into  it,  the  right  one  opening  into  the  right  renal  vein.  They  communicate  sometimes  on 
one  side  or  the  other  with  a  lumbar  vein  or  with  the  middle  suprarenal,  and  the  left  vein  has 
been  observed  to  open  into  the  hemiazygos. 

The  spermatic  veins  are  very  apt  to  become  varicose,  and  it  is  well  known  that  this  con- 
dition is  more  apt  to  occur  in  the  left  vein  than  in  the  right.  Various  reasons  have  been  assigned 
for  this  difference  in  the  two  veins,  the  chief  of  these  being  ( 1 )  that  the  left  vein  opens  at  prac- 
tically a  right  angle  into  the  renal,  while  the  right  opens  at  an  acute  angle  into  the  vena  cava  ; 
(2)  the  left  vein  is  destitute  of  valves  at  its  opening  into  the  renal,  while  the  right  one  usually 
possesses  a  pair  at  its  orifice  ;  and  (3)  that  the  left  vein  in  its  course  up  the  abdominal  wall  lies 
beneath  the  sigmoid  colon,  while  the  right  has  only  coils  of  the  small  intestine  with  their  more 
fluid  contents  in  front  of  it. 

6b.  The  Ovarian  Veins. — The  ovarian  veins  (vv.  ovaricae)  correspond  to 
the  spermatic  veins  of  the  male.  They  take  their  origin  from  the  veins  which 
issue  at  the  hilum  of  the  ovary  and  are  also  connected  by  wide  anastomoses 
with  the  veins  of  the  fundus  of  the  uterus.  They  form  a  close  plexus,  the  pam- 
piniform plexus  (plexus  pampiniformis),  which  accompanies  the  ovarian  artery 
between  the  two  layers  of  the  broad  ligament  parallel  with  the  Fallopian  tube, 
receiving   branches  from  the  latter  structure  and   from  the  round  ligament  of  the 


9o4  HUMAN   ANATOMY. 

uterus.  Leaving  the  broad  ligament  with  the  ovarian  artery,  they  ascend  along 
that  vessel,  the  number  of  trunks  becoming  reduced  to  two  and  eventually  to  one, 
and  they  open  above  in  the  same  manner  as  the  spermatic  veins,  the  right  one 
into  the  inferior  vena  cava  and  the  left  one  into  the  left  renal  vein.  They  possess 
no  valves. 

Their  variations  are  essentially  similar  to  those  presented  by  the  spermatic  veins. 

Practical  Considerations. —  The  Tributa?ries  of  the  Inferior  Cava. — In  a 
case  of  occlusion  of  the  inferior  cava  by  thrombus  extending  from  the  renal  vein  to 
the  right  auricle,  the  phrenic  and  renal  veins  opened  into  the  lumbar  and  azygos 
veins,  the  blood  of  the  abdomen  thus  gaining  the  superior  cava  (Allen). 

The  intralobular  branches  of  the  hepatic  veins  may  be  the  source  of  profuse 
hemorrhage  in  cases  of  wound  or  rupture  of  the  liver,  because  (a)  they  are  thin- 
walled  ;  (6)  they  are  not  encircled  by  cellular  tissue,  but  are  closely  attached  to  the 
liver  substance  and  thus  cannot  collapse  or  retract,  a  condition  which  also  predisposes 
to  the  entrance  of  air  into  the  divided  veins  ;  (c)  they  are  valveless,  and  the  main 
trunks  open  direct  into  the  vena  cava,  any  obstruction  of  which  would  therefore  result 
in  the  escape  of  great  quantities  of  blood  ;  (d  )  the  flow  in  the  main  trunks — from  the 
vein  to  the  cava — is  influenced  by  the  movements  of  the  diaphragm,  the  descent  of 
this  muscle  tending  to  constrict  the  opening  through  which  the  veins  pass,  and  thus 
to  obstruct  the  current  and  favor  bleeding.  Hemorrhage  from  the  liver  after  a  wound 
or  during  an  operation  is  very  difficult  to  arrest  by  ligature  on  account  of  the  thinness 
of  the  walls  of  the  intralobular  veins  and  the  friability  of  the  liver  tissue  itself.  It  is 
usually  controlled  by  gauze-pressure  or  by  the  galvano-cautery.  The  branches  of  the 
portal  vein  may  also  bleed  freely,  but  are  surrounded  by  a  quantity  of  lax  cellular 
tissue,  as  theyrun  in  the  "  portal  canals"  with  the  branches  of  the  biliary  ducts  and 
of  the  hepatic  artery,  and  can  thus  retract  or  collapse  when  torn  or  divided.  More- 
over, the  blood-pressure  within  the  portal  vein  is  low,  favoring  the  spontaneous  arrest 
of  hemorrhage.  In  obstruction  of  the  common  duct,  preventing  the  escape  of  bile 
into  the  intestine,  the  radicles  of  the  hepatic  veins  take  up  the  bile-stained  exudate 
that  results  from  the  increased  intra-hepatic  tension.  Its  entrance  into  the  general 
circulation  through  the  vena  cava  gives  rise  to  jaundice. 

The  relative  shortness  of  the  right  renal  vein  occasionally  adds  to  the  difficulties 
of  a  right-sided  nephrectomy,  the  pedicle — the  vein,  artery,  ureter,  etc. — being 
shorter  and  less  easily  controlled  by  ligature.  As  the  veins  are  subject  to  variation 
as  well  as  the  arteries — though  less  frequently — supernumerary  or  misplaced  vessels 
should  be  carefully  looked  for.  They  may  be  found  emerging  from  the  kidney  at 
either  pole,  or  from  the  hilum  behind  the  pelvis.  Fatal  results  have  followed  the 
failure,  during  a  nephrectomy,  to  find  and  secure  such  aberrant  vessels.  At  times 
the  left  renal  vein  passes  behind  the  aorta,  to  which  occurrence  may  be  attributed 
the  greater  frequency  of  hyperemia  of  the  left  kidney  (Allen).  The  renal  veins 
may  be  obstructed  by  pressure  from  retroperitoneal  growths,  or — in  the  supine 
position — from  movable  abdominal  tumors  or  the  gravid  uterus,  or  from  traction 
caused  by  displacements  of  the  kidney  itself,  or  as  a  result  of  congestion  in  the 
cardio-pulmonary  system,  as  in  pneumonia  or  valvular  heart  disease.  By  whatever 
cause  produced,  the  congestion,  if  sufficiently  long-continued,  may  give  rise  to  a  form 
of  chronic  interstitial  nephritis.  The  communication  (vide  supra)  between  the  renal 
veins  and  the  first  lumbar  vein  and — on  the  left  side- — the  hemiazygos  vein,  accounts 
for  the  undoubted  good  effect  often  produced  in  renal  congestions  by  counter- 
irritation,  blisters,  cupping,  or  leeching  in  the  loin. 

The  spermatic  veins  are  of  chief  practical  interest  in  their  relation  to  varicocele. 
The  anatomical  reasons  for  the  frequency  of  this  condition,  and  for  its  occurrence  by 
preference  on  the  left  side,  are  given  on  page  1961. 

The  veins  of  the  pampiniform  plexus  proper  are  usually  distinct  from  those 
which  accompany  the  vas  deferens  and  its  artery.  In  excision  of  the  former  set  for 
varicocele,  the  vas  deferens  is  always  pushed  to  the  rear  and  held  out  of  harm's  way. 
It  carries  with  it  its  artery  and  veins,  and  the  anastomotic  communications  of  the 
former  with  the  spermatic  artery — almost  always  cut  or  tied  with  its  venous  plexus — 
and  with  the  scrotal  arteries  suffice  to  maintain  the  nutrition  of  the  testis,  while  the 


THE   INFERIOR   CAVAL   SYSTEM.  905 

veins  of  this  smaller  and  posterior  group  enlarge  to  carry  on  the  return  circulation. 
Elevation  is  of  especial  value  in  testicular  inflammation,  as  the  dependent  position  of 
the  spermatic  veins  and  their  lack  of  adequate  support  greatly  intensify  the  engorge- 
ment and  venous  obstruction  of  inflammatory  processes. 

The  Common  Iliac  Veins. 

The  common  iliac  veins  (vv.  iliacae  communes)  (Fig.  765)  are  two  in  number, 
and  are  formed  opposite  the  sacro-iliac  articulations  by  the  union  of  the  internal  and 
external  iliac  veins.  They  pass  upward,  converging  as  they  go,  and  unite  at  about 
the  level  of  the  intervertebral  disk  between  the  fourth  and  fifth  lumbar  vertebra?  to 
form  the  vena  cava  inferior. 

Since  their  point  of  union  lies  somewhat  to  the  right  of  the  median  line,  the  right 
vein  is  shorter  than  the  left  and  its  course  is  more  directly  upward.  Neither  vein 
possesses  valves. 

Relations. — The  union  of  the  two  veins  takes  place  beneath  the  right  common 
iliac  artery,  and  the  right  vein,  at  its  origin,  lies  behind  that  vessel,  although,  since  its 
course  is  more  vertical  than  that  of  the  artery,  it  gradually  comes  to  lie  somewhat 
lateral  to  it  above.  The  left  vein  near  its  termination  is  crossed  from  without  inward 
by  the  right  common  iliac  artery,  and  throughout  its  course  lies  medially  to  the  left 
common  iliac  artery  and  on  a  plane  somewhat  posterior  to  it. 

Variations. — Occasionally  the  external  and  internal  iliac  veins  do  not  unite  to  form  a  common 
stem,  but  open  directly  into  the  inferior  vena  cava.     This  may  occur  on  one  or  both  sides. 

Tributaries. — In  addition  to  the  external  and  internal  iliacs,  by  whose  union 
they  are  formed,  the  common  iliacs  receive  but  a  single  tributary,  the  middle  sacral 
vein  (v.  sacralis  media),  and  this  opens  into  the  left  vein.  It  accompanies  the  middle 
sacral  artery,  and  in  the  lower  part  of  its  course  it  is  frequently  double,  one  vessel 
lying  on  each  side  of  the  artery.  Opposite  each  sacral  vertebra  it  receives  a 
transverse  connecting  branch  from  the  lateral  sacral  veins  and  so  forms  with  these 
what  is  termed  the  anterior  sacral  plexus.  At  its  origin  it  communicates  with 
the  hemorrhoidal  veins. 

The  Internal  Iliac  Vein. 

The  internal  iliac  vein  (v.  hypogastrica)  (Fig.  767)  of  each  side  is  a  short  but 
rather  large  vessel,  which  accompanies  the  internal  iliac  artery,  lying  to  its  medial 
side  and  in  a  plane  somewhat  posterior  to  it.  It  extends  from  the  neighborhood  of 
the  great  sacro-sciatic  foramen  to  the  level  of  the  sacro-iliac  synchondrosis,  where  it 
unites  with  the  external  iliac  to  form  the  common  iliac  vein. 

Tributaries. — Its  tributaries  correspond  in  general  with  the  branches  of  the 
internal  iliac  artery,  but  those  which  arise  in  the  pelvic  viscera  present  the  peculiarity 
that  they  take  their  origin  from  more  or  less  extensive  plexuses  which  communicate 
with  one  another.  The  stems  which  pass  from  these  plexuses  to  the  internal  iliac 
also  anastomose  to  a  considerable  extent,  the  result  being  that  it  is  not  possible  in  all 
cases  to  recognize  definite  veins  corresponding  to  the  visceral  arteries. 

The  following  are  the  tributaries  that  are,  as  a  rule,  to  be  recognized  :  ( 1 )  the 
gluteal,  (2)  the  lateral  sacral,  (3)  the  ilio-licmbar,  (4)  the  sciatic,  (5)  the  internal 
ptidic,  (6)  the  obturator,  (7)  the  middle  hemorrhoidal,  (8)  the  uteri?ie,  and  (9)  the 
vesical  veins. 

1.  The  Gluteal  Vein. — The  gluteal  vein  (v.  glutaea  superior)  accompanies  the 
artery  of  the  same  name.  Throughout  its  extrapelvic  course  its  tributaries  accom- 
pany the  branches  of  the  artery  as  valved  vena?  comites,  and  at  the  upper  part  of  the 
greater  sacro-sciatic  foramen  the  veins  accompanying  the  two  main  branches  of  the 
artery  unite  to  form  a  double  trunk,  united  by  numerous  anastomoses.  This  trunk, 
which  is  occasionally  single,  passes  through  the  greater  sacro-sciatic  foramen  above 
the  pyriformis  muscle  and,  after  a  short  intrapelvic  course,  opens  into  the  internal 
iliac  vein. 

Where  they  pass  through  the  greater  sacro-sciatic  foramen  both  artery  and  vein 
are  surrounded  by  a  dense  connective  tissue  which  renders  their  separation  difficult 
and  brings  it  about  that  the  lumen  of  the  vein  remains  patent  when  emptied  of  blood. 


906 


HUMAN    ANATOMY. 


2.  The  Lateral  Sacral  Veins. — The  lateral  sacral  veins  (w.  sacrales  laterales) 
are  usually  double,  and  pass  upward  with  their  arteries  upon  the  anterior  surface 
of  the  sacrum  just  medial  to  the  anterior  sacral  foramina,  and  open  above  either 
directly  into  the  internal  iliacs  or  into  the  gluteal  veins.  As  they  pass  each  sacral 
foramen  they  receive  tributaries  from  the  internal  spinal  plexuses,  and  opposite  each 
sacral  vertebra  are  connected  by  transverse  branches  with  the  middle  sacral  veins, 
these  anastomoses  forming  the  anterior  sacral  plexus. 

3.  The  Ilio-Lumbar  Vein. — The  ilio-lumbar  vein  (v.  iliolumbalis)  follows 
the  course  of  the  corresponding  artery  and  its  branches  and  is  richly  supplied  with 


Fig.  767. 


Internal  il 
Anterior  superior 


External  ili 

artery  and 
Superior  gluteal 


perineal  muscle 


Bulb  of  corpus  spongiosum 


Veins  of  pelv 


■iewed  from  left  side 


valves.  Its  lumbar  tributary  receives  some  of  the  lower  intervertebral  veins. and 
occasionally  the  last  lumbar,  and  anastomoses  with  the  lower  portion  of  the  ascending- 
lumbar  vein.  The  iliac  tributary,  which  begins  over  the  crest  of  the  ilium  and  in 
the  substance  of  the  iliacus  muscle,  makes  anastomoses  with  tributaries  of  the  deep 
circumflex  iliac  vein  and  thus  establishes  an  important  collateral  venous  path  between 
the  external  and  internal  iliacs. 

The  main  stem  of  the  vein  is  a  single  trunk  which  opens  into  the  internal  iliac 
or  occasionally  into  the  common  iliac. 

4.  The  Sciatic  Vein. — The  sciatic  vein  (v.  glutaea  inferior)  of  either  side  of  the 
body  has  essentially  the  same  course  as  the  corresponding  artery.      Its  extrapelvic 


THE    INFERIOR   CAVAL   SYSTEM.  907 

tributaries  are  vena?  comites  of  the  branches  of  the  artery,  and  its  usually  single 
main  stem  passes  through  the  greater  sacro-sciatic  foramen  below  the  pyriformis  to 
empty  into  the  internal  iliac. 

Anastomoses  of  comparatively  large  calibre  occur  between  the  extrapelvic 
portions  of  the  sciatic  vein  and  the  internal  circumflex  and  first  perforating  tribu- 
taries of  the  deep  femoral  vein,  thus  establishing  a  collateral  venous  path  between 
the  tributaries  of  the  internal  and  external  iliacs. 

5.  The  Internal  Pudic  Vein. — The  internal  pudic  vein  (v.  pudenda  interna)  is 
associated  throughout  the  greater  part  of  its  course  with  the  artery  of  the  same  name. 
It  differs,  however,  somewhat  in  its  origin,  since  it  is  not  the  direct  continuation  of  the 
dorsal  vein  of  the  penis  (or  clitoris),  although  it  communicates  with  that  vessel  by  a 
small  branch  immediately  below  the  symphysis  pubis,  but  is  rather  the  continuation 
of  the  veins  of  the  corpus  cavernosum  which  accompany  the  artery  to  that  structure. 
It  is  throughout  the  most  of  its  length  double,  anastomoses  between  the  two  stems 
surrounding  the  internal  pudic  artery.  It  has  its  origin  between  the  two  layers  of  the 
triangular  ligament  of  the  perineum  and  passes  backward  into  the  ischio-rectal  fossa, 
lying  with  the  artery  at  the  side  of  that  cavity  in  a  canal  (A/cock' s  ca?ial)  formed  by  a 
splitting  of  the  lower  edge  of  the  obturator  fascia.  It  leaves  the  ischio-rectal  fossa  by 
the  lesser  sacro-sciatic  foramen  and,  curving  around  the  spine  of  the  ischium,  enters 
the  pelvis  through  the  lower  part  of  the  greater  sacro-sciatic  foramen  and  empties 
into  the  internal  iliac. 

In  addition  to  the  communication  with  the  dorsal  vein  of  the  penis  (or  clitoris) 
already  mentioned,  the  internal  pudic  vein  makes  near  its  origin  a  connection  with  the 
pudendal  plexus  and,  as  it  curves  over  the  spine  of  the  ischium,  with  the  sciatic  vein. 

It  possesses  several  valves  arranged  in  a  rather  characteristic  manner.  Through- 
out its  course  through  the  perineum  it  is  valveless,  but  both  its  terminal  portion  and 
its  communication  with  the  pudendal  plexus  possess  valves  whose  concavities  look  in 
the  one  case  towards  the  internal  iliac  and  in  the  other  towards  the  plexus.  Blood 
contained  in  the  perineal  portion  of  the  vein  may  flow,  therefore,  either  towards  the 
internal  iliac  directly  or  to  the  pudendal  plexus  (Fenwick),  and  the  communication 
with  the  latter  cannot  well  be  regarded  as  the  origin  of  the  vein,  as  is  sometimes 
done. 

Tributaries. — In  addition  to  (a)  the  vein  of  the  corpus  cavernosum  (v.  profunda  penis  vel 
clitoridis)  already  mentioned,  the  internal  pudic  vein  receives  numerous  tributaries  which  cor- 
respond with  the  branches  of  the  artery.  Among  these  may  be  mentioned  :  (b)  the  veins  of  the 
bulb  ( vv.  bulbi  urethrae),  which  are  quite  numerous  and  issue  from  the  bulb  of  the  urethra  or  from 
the  bulbus  vestibuli  in  the  female,  these  latter  vessels  being  quite  large  ;  {c)  the  superficial  peri- 
neal veins  (vv.  scrotales  posteriores),  which  return  the  blood  from  the  integument  and  superficial 
muscles  of  the  perineum  and  from  the  posterior  surface  of  the  scrotum  and  the  posterior  portion 
of  the  labia  majora,  anastomosing  in  these  structures  with  the  tributaries  of  the  external  pudic 
veins;  (d)  the  inferior  hemorrhoidal  veins  (vv.  haemorrhoidales  inferiores),  which  traverse  the 
ischio-rectal  space  from  the  neighborhood  of  the  anus,  where  they  make  communications  with 
the  hemorrhoidal  plexus  of  the  rectum. 

6.  The  Obturator  Vein. — The  obturator  vein  (v.  obturatoria)  accompanies  the 
obturator  artery  and  shares  in  the  variations  which  that  vessel  presents  (page  814). 
It  takes  its  origin  in  the  adductor  muscles  of  the  thigh,  its  tributaries  uniting  to  form 
an  internal  and  an  external  branch,  which  curve  around  the  margins  of  the  obturator 
foramen.  The  vein  formed  by  the  union  of  these  two  branches  passes  through  the 
opening  in  the  upper  part  of  the  obturator  membrane  and  passes  across  the  lateral 
pelvic  wall,  lying  immediately  below  the  artery.  It  opens,  as  a  rule,  into  the  internal 
iliac  vein. 

Its  communications  are  somewhat  extensive  and  important.  Its  external  tribu- 
tary branch  receives  branches  from  the  scrotum  or  labia  majora  and  through  these 
communicates  with  the  external  pudic  veins.  At  its  passage  through  the  opening 
in  the  obturator  membrane  it  receives  branches  from  the  obturator  plexus,  which 
cover  both  surfaces  of  the  membrane  and  drain  the  obturator  muscles,  and  also  a 
branch  which  passes  downward  and  inward  upon  the  inner  surface  of  the  os  pubis, 
frequently  communicating  above  with  the  pubic  tributary  of  the  deep  epigastric  vein. 


9o8  HUMAN   ANATOMY. 

Additional  communications  are  made  with  the  vesico-prostatic  (vesico-vaginal) 
plexus  and  the  internal  pudic  vein,  and  also  with  the  internal  circumflex  branch  of 
the  deep  femoral  and  with  the  sciatic. 

7.  The  Middle  Hemorrhoidal  Vein. — The  middle  hemorrhoidal  vein  (v. 
haemorrhoidalis  media)  has  its  origin  in  the  hemorrhoidal  plexus  of  the  rectum,  and 
after  receiving  tributaries  from  the  seminal  vesicles,  the  prostate  gland,  and  the  urinary 
bladder  in  the  male  and  from  the  vagina  in  the  female,  opens  into  the  internal  iliac 
or  one  of  its  tributaries.  It  is  a  comparatively  large  vein,  and  of  importance  in  that 
it  forms  through  its  connection  with  the  hemorrhoidal  plexus  a  communication 
between  the  portal  and  inferior  caval  systems  of  veins. 

The  hemorrhoidal  plexus  (plexus  haemorrhoidalis)  which  surrounds  the  rectum 
is  composed  of  two  venous  net-works,  one  of  which,  the  internal  hemorrhoidal  plexus , 
lies  in  the  submucosa  of  the  rectum,  while  the  other,  the  external  hemorrhoidal  plexus , 
rests  upon  its  outer  surface.  The  internal  plexus  is  characterized  in  the  adult,  in  that 
portion  of  it  which  lies  just  above  the  anal  opening,  by  the  occurrence  of  round  or 
elongated  bunches  (glomera  haemorrhoidalia)  formed  by  a  number  of  small  veins  coiled 
together  into  a  mass  resembling  somewhat  a  Malpighian  glomerulus.  Upon  the  veins 
which  form  the  glomera,  or  upon  those  extending  between  adjacent  glomera,  ampullar 
dilatations  occur  which  have  been  regarded  both  as  the  cause  and  as  the  result  of  the 
glomera  formation.  Be  that  as  it  may,  the  internal  hemorrhoidal  plexus  presents  in 
the  adult,  slightly  above  the  anus,  a  distinct  band  characterized  by  the  occurrence 
of  glomera  and  dilatations,  and  forming  what  is  termed  the  annulus  haemorrhoidalis. 

The  internal  plexus  opens  partly  at  the  anal  orifice  into  the  branches  of  the 
inferior  hemorrhoidal  veins  and  partly,  by  branches  which  traverse  the  muscular  coats 
of  the  rectum,  into  the  external  plexus.  This  has  three  sets  of  efferent  veins  : 
(1)  the  inferior  hemorrhoidals,  which  open  into  the  internal  pudic  ;  (2)  the  middle 
hemorrhoidals,  which  pass  to  the  internal  iliac  or  one  of  its  branches  ;  and  (3)  the 
superior  hemorrhoidal,  which  leads  to  the  inferior  mesenteric  and  so  to  the  portal 
vein.  The  external  plexus  also  communicates  with  the  vesico-prostatic  plexus  in 
the  male  and  the  vaginal  plexus  in  the  female. 

8.  The  Uterine  Vein. — The  uterine  vein  (v.  uterina)  arises  opposite  the 
external  os  uteri  from  the  plexus  utero-vaginalis.  It  is  at  first  a  double  vein,  its  two 
trunks  accompanying  the  uterine  artery,  and  where  that  vessel  crosses  the  ureter  one 
of  the  trunks  passes  with  the  artery  in  front  of  the  duct  and  the  other  behind  it. 
The  two  trunks  then  usually  unite  to  a  single  vein,  which  passes  into  the  internal 
iliac,  frequently  receiving  the  vesical  veins  or  the  obturator. 

The  utero-vaginal  plexus  is  formed  by  the  veins  which  return  the  blood  from 
the  uterus  and  vagina.  The  veins  in  the  substance  of  the  uterus  are  exceedingly 
thin-walled,  appearing  as  clefts  in  sections,  and  form  a  more  or  less  distinct  layer 
(stratum  vasculare)  in  the  muscular  wall  of  the  organ.  From  this  vessels  pass  to 
both  the  anterior  and  posterior  surfaces  of  the  organ  and  follow  a  course  which  is 
outward  and  more  or  less  downward  towards  the  lateral  borders,  where,  between  the 
two  layers  of  the  broad  ligament,  they  form  a  rich  plexus,  the  uterine  plexus,  the 
vessels  of  which  converge  towards  the  origin  of  the  uterine  vein,  opposite  the  external 
os  uteri.  The  vaginal  veins  form  a  rich  plexus  in  the  walls  of  the  vagina,  the 
emissaries  from  which  are  directed  laterally  and  more  or  less  upward,  forming  along 
the  lateral  walls  of  the  organ  a  rich  vaginal  plexus  whose  stems  also  converge  to 
the  uterine  vein  at  the  level  of  the  external  os  uteri.  These  two  plexuses,  the  uterine 
and  vaginal,  are  continuous  at  the  level  of  the  external  os  uteri  and  form  together 
the  extensive  plexus  utero-vaginalis. 

At  the  fundus  of  the  uterus  this  plexus  makes  abundant  connections  with 
the  pampiniform  plexus  of  the  ovarian  veins  and  with  the  funicular  veins  which 
accompany  the  ligamentum  teres.  Lower  down,  throughout  its  uterine  portion,  it 
receives  affluents  from  the  plexus  of  veins  which  occurs  between  the  layers  of  the  broad 
ligament,  and  the  lower  part  of  its  vaginal  portion  makes  connections  anteriorly 
with  the  vesico-vaginal  plexus  and  posteriorly  with  the  external  hemorrhoidal  plexus. 

9.  The  Vesical  Veins. — The  vesical  veins  (vv.  vesicates)  vary  somewhat  in 
number,  but  together  represent  a  vessel  of  considerable  size.  They  arise  at  the  sides 
of  the  bladder  from  a  well-marked  plexus  which  occupies  in  the  male  the  groove 


THE    INFERIOR    CAVAL    SYSTEM.  909 

between  the  prostate  gland  and  the  bladder  and  is  termed  the  vesico-prostatic  plexus. 
In  the  female  the  plexus  lies  at  the  sides  and  base  of  the  bladder,  and  from  its 
relations  posteriorly  is  known  as  the  vesico-vaginal  plexus.  From  their  origin 
the  vesical  veins  pass  upward,  outward,  and  backward  to  open  into  the  internal 
iliac. 

The  vesico-prostatic  or  vesico-vaginal  plexus  (plexus  vesicalis),  occupying 
the  position  indicated  above,  is  formed  principally  by  the  veins  which  drain 
the  urinary  bladder  and,  in  the  male,  the  prostate  gland.  Posteriorly,  in  the 
male,  the  plexus  communicates  with  the  external  hemorrhoidal  plexus,  and  in  the 
female  with  the  vaginal  plexus,  and  anteriorly,  in  both  sexes,  it  communicates 
extensively  with  the  pudendal  plexus.  In  addition  to  the  drainage  which  it 
possesses  through  the  vesical  veins,  it  also  drains  by  way  of  the  obturator  veins, 
branches  from  it  joining  those  vessels  just  after  they  have  passed  through  the 
obturator  foramina. 

The  pudendal  plexus  (plexus  pudendalis),  also  known  as  the  plexus  of  Santo  - 
rini,  occupies  the  space  between  the  lower  part  of  the  pelvic  surface  of  the  symphysis 
pubis  and  the  anterior  surface  of  the  neck  of  the  bladder,  becoming  continuous 
posteriorly  at  the  sides  with  the  vesico-prostatic  (vesico-vaginal)  plexus.  Its  chief 
tributary  is  the  deep  dorsal  vein  of  the  penis  (clitoris)  (v.  dorsalis  penis  vel 
clitoridis),  which  is  a  single  large  vein  (sometimes  partly  double  in  the  female)  which 
passes  along  the  dorsal  mid-line  of  the  penis  or  clitoris,  beneath  the  deep  fascia 
(Fig.  767),  in  the  groove  between  the  two  corpora  cavernosa,  and  has  on  either  side 
of  it  one  of  the  two  dorsal  arteries.  It  receives  branches  from  the  corpora  cavernosa 
and  has  its  origin  in  two  veins  which  curve  from  below  upward  around  the  base  of 
the  glans  penis  (clitoridis).  At  the  root  of  the  penis  (clitoris)  it  leaves  the  dorsal 
surface  and  perforates  the  triangular  ligament  of  the  perineum,  usually  just  below  the 
border  of  the  subpubic  ligament,  so  entering  the  pelvis.  It  then  bifurcates,  each  of 
the  branches  passing  into  the  pudendal  plexus.  Before  entering  the  pelvis  it  gives 
off  on  either  side  a  small  branch  which  unites  with  the  internal  pudic  vein,  thus 
representing  the  course  of  the  artery. 

In  addition  to  the  dorsal  vein  of  the  penis  (clitoris),  the  pudendal  plexus  also 
receives  branches  from  the  internal  pudic  vein  and  from  the  anterior  surfaces  of  the 
bladder  and,  in  the  male,  the  prostate.  It  communicates  posteriorly  and  at  the 
sides  with  the  vesico-prostatic  (vesico-vaginal)  plexus,  and  through  it  finds  its  chief 
efferents  in  the  vesical  veins,  although  it  is  also  drained  by  the  obturator  veins,  with 
each  of  which  it  communicates  by  one  or  two  branches. 

The  External  Iliac  Vein. 

The  external  iliac  vein  (v.  iliaca  externa)  (Figs.  766,  767)  begins  at  Poupart's 
ligament,  where  the  femoral  vein  becomes  continuous  with  it,  and  passes  upward, 
backward,  and  inward  to  the  level  of  the  sacro-iliac  articulation,  where  it  unites  with 
the  internal  iliac  to  form  the  common  iliac. 

Its  course  is  along  the  line  of  junction  of  the  false  and  the  true  pelvis,  and  it  lies 
upon  the  inner  border  of  the  psoas  muscle  and  internal,  or  in  its  upper  part  internal 
and  posterior,  to  the  external  iliac  artery.  Near  its  termination  it  is  crossed  by  the 
internal  iliac  artery,  on  the  left  side  almost  at  a  right  angle,  pn  the  right  more 
obliquely.  Valves  are  present  in  about  35  veins  out  of  100,  but  in  a  third  of 
such  cases    they  are   insufficient. 

Tributaries. — The  tributaries  of  the  external  ilia-c  vein  are  :  ( 1 )  the  deep  epi- 
gastric and  (2)  the  deep  circumflex  iliac  veins. 

1.  The  Deep  Epigastric  Vein. — The  deep  epigastric  vein  (v.  epigastrica 
inferior)  has  its  origin  above  the  umbilicus  in  the  substance  of  the  rectus  abdominis 
muscle,  where  it  anastomoses  with  the  superior  epigastric  vein.  It  accompanies  the 
deep  epigastric  artery  as  two  venae  comites  which  unite  below  to  form  a  single  trunk 
opening  into  the  external  iliac  a  short  distance  above  Poupart's  ligament. 

Below  the  level  of  the  umbilicus  the  vein  is  provided  with  valves  whose  concav- 
ities are  directed  downward,  but  above  the  umbilicus  it  is  said  to  be  destitute  of 
valves.     It  receives  tributaries  from  the  rectus  muscle  and,  as  it  passes  beneath  the 


gio  HUMAN    ANATOMY. 

internal  abdominal  ring,  from  the  spermatic  cord  or  round  ligament  of  the  uterus. 
The  connections  which  it  makes  with  other  veins  are  numerous  and  important. 
Its  connections  with  the  superior  epigastric  vein  have  already  been  noted  ;  by  this 
communication  is  established  between  the  superior  and  inferior  venae  cavae.  In 
addition,  by  means  of  branches  which  traverse  the  sheath  of  the  rectus  muscle, 
it  communicates  with  the  subcutaneous  and  subperitoneal  veins  of  the  abdominal 
wall  and  with  the  parumbilical  veins,  forming  through  these  latter  a  connection 
with  the  portal  system  of  veins.  Finally,  by  means  of  a  pubic  branch,  which  is 
frequently  a  tributary  of  the  external  iliac  rather  than  of  the  deep  epigastric,  it 
communicates  with  the  obturator  vein,  and  by  the  enlargement  of  this  communication 
the  obturator  vein,  just  as  is  the  case  with  the  artery,  may  become  a  tributary  of  the 
deep  epigastric. 

2.  The  Deep  Circumflex  Iliac  Vein. — The  deep  circumflex  iliac  vein  (v. 
circumtlexa  ilium  profunda)  has  the  same  course  as  the  corresponding  artery,  which 
it  surrounds  in  a  plexiform  manner.  It  possesses  valves  and  communicates  with  the 
iliolumbar  veins.  Near  its  termination  it  becomes  a  single  trunk  and  opens  into  the 
external  iliac  a  little  above  the  deep  epigastric  ;  occasionally  it  opens  into  the  latter 
vessel. 

THE    VEINS    OF    THE    LOWER    LIMB. 

The  external  iliac  vein  is  the  channel  by  which  the  blood  returning  from  the 
lower  limb  is  conveyed  to  the  inferior  vena  cava  and  is  the  direct  upward  continuation 
of  the  femoral  vein.  Instead,  however,  of  proceeding  to  a  description  of  this  latter 
vessel  and  so  down  the  leg,  it  will  be  more  convenient  to  begin  the  account  of  the 
veins  of  the  lower  limb  with  those  of  the  foot  and  proceed  upward  to  the  femoral. 

As  in  the  upper  limb,  two  practically  distinct  sets  of  veins  can  be  recognized  in 
the  leg  ;  one  set  is  more  or  less  deeply  seated  and  accompanies  the  arteries,  while  the 
other  is  superficial  and,  in  the  adult,  has  a  course  quite  independent  of  the  arterial 
distribution.      The  deep  veins  will  first  be  considered. 

THE   DEEP   VEINS. 
The  Deep  Veins  of  the  Foot. 

The  deep  veins  of  the  sole  of  the  foot  have  their  origin  in  a  net-work  with 
more  or  less  distinctly  elongated  meshes,  which  occurs  upon  the  plantar  surfaces 
of  the  digits.  These  are  the  plantar  digital  veins  (vv.  digitales  plantares),  and 
in  the  webs  of  the  toes  the  vessels  of  each  digit  unite  with  those  of  the  neighboring 
ones  to  form  a  series  of  plantar  interosseous  veins  (vv.  metatarseae  plantares) 
occupying  the  metatarsal  interspaces  and  forming  venae  comites  for  the  plantar 
interosseous  (metacarpal)  arteries.  Just  as  the  digital  veins  unite  to  form  the 
interosseous,  they  send  dorsal  branches  (vv.  intercapitulares),  which  unite  with 
the  dorsal  interosseous  veins,  and,  in  addition,  make  connections  with  the  superficial 
plantar  veins,  and  might,  indeed,  be  classed  with  these  quite  as  appropriately  as  with 
the  deep  set. 

The  plantar  interosseous  veins  pass  backward,  receiving  branches  from  the 
neighboring  muscles,  and  open  into  a  venous  plantar  arch  (arcus  venosus  plantaris), 
formed  by  the  ver;ae  comites  of  the  arterial  plantar  arch.  These  are  continued  pos- 
teriorly into  the  external  plantar  veins,  which  pass  obliquely  across  the  foot  along 
with  the  corresponding  artery  and  unite  behind  the  inner  malleolus  with  the  internal 
plantar  veins  to  form  the  companion  veins  of  the  posterior  tibial  artery.  Both 
plantar  veins  give  off  branches  which  perforate  the  plantar  aponeurosis  and  communi- 
cate with  the  superficial  plantar  veins,  and  connecting  vessels  also  pass  across  the 
sole  of  the  foot  between  the  two  veins. 

Upon  the  dorsum  of  the  foot  there  exist  the  dorsal  digital  veins  (vv.  digitales 
dorsales),  which,  like  the  corresponding  plantar  veins,  may  be  equally  classified  with 
superficial  or  deep  veins,  since  they  make  connections  with  both  sets.  In  the  webs  of 
the  toes  the  vessels  of  adjoining  digits  unite  to  form  the  four  dorsal  interosseous 
veins  (vv.  metatarseae  dorsales),  which  occupy  the  metatarsal  interspaces  and  com- 
municate with  the  corresponding  plantar  veins  by  the  intercapitular  and  perforating 


THE  VEINS    OF    THE    LOWER    LIMB.  911 

veins.  They  form  the  vena  comites  of  the  dorsal  interosseous  (metatarsal)  arteries  and 
open  into  the  companion  veins  of  the  metatarsal  artery.  These,  together  with  the  veins 
accompanying  the  tarsal  arteries,  open  into  the  venae  comites  of  the  art.  dorsalis  pedis, 
and  these  in  turn  are  continuous  with  the  vena;  comites  of  the  anterior  tibial  artery. 

The  Deep  Veins  of  the  Leg. 

The  deep  veins  of  the  leg  are  the  venae  comites  of  the  posterior  and  anterior 
tibial  arteries  and  their  branches.  The  posterior  tibial  vein  (v.  tibialis  posterior) 
is  formed  behind  the  internal  malleolus  by  the  union  of  the  internal  and  external 
plantar  veins,  and  consists  of  two,  or  in  many  cases  three,  veins  accompanying  the 
posterior  tibial  arterv.  It  terminates  at  the  lower  border  of  the  popliteus  muscle  by 
uniting  with  the  anterior  tibial  veins  to  form  the  popliteal,  and  possesses  in  its  course 
from  eight  to  twenty  valves.  A  short  distance  below  the  popliteus  muscle  it  receives 
the  peroneal  veins  ( w.  peroneae)  which  accompany  the  peroneal  artery.  They  are 
usually  of  larger  calibre  than  the  posterior  tibial  veins,  receiving  a  larger  share  of  the 
vessels  which  come  from  the  posterior  crural  muscles,  and  they  anastomose  with  the 
posterior  tibials  by  frequent  transverse  branches,  and  also  with  the  anterior  tibials. 
They  possess  from  eight  to  ten  valves. 

The  anterior  tibial  veins  (vv.  tibiales  anteriores)  are  the  upward  continuation 
of  the  venae  comites  of  the  art.  dorsalis  pedis.  They  accompany  the  anterior  tibial 
artery,  and  are  united  across  the  artery  by  numerous  transverse  anastomoses.  They 
pass  with  the  artery  to  the  posterior  surface  of  the  crus  above  the  interosseous  mem- 
brane and  unite  with  the  posterior  tibials  to  form  the  popliteal  vein.  They  make 
communications  with  both  the  peroneal  and  posterior  tibial  veins  by  branches  which 
perforate  the  interosseous  membrane,  and  are  furnished,  on  the  average,  with  about 
eleven  valves. 

The  Popliteal  Vein. 

The  popliteal  vein  (v.  poplitea)  (Fig.  768)  is  a  single  trunk  formed  by  the  union 
of  the  anterior  and  posterior  tibial  veins  at  the  lower  border  of  the  popliteus  muscle, 
and  it  extends  from  that  point  to  the  opening  in  the  adductor  magnus  which  transmits 
the  femoral  artery.  It  is  throughout  closely  bound  down  by  dense  connective  tissue 
to  the  popliteal  artery,  and  lies  between  that  vessel  and  the  internal  popliteal  nerve. 
Its  course,  however,  is  not  quite  parallel  to  that  of  the  artery,  but  in  its  lower  part 
it  is  slightly  internal  to  the  artery  and  in  its  upper  part  somewhat  external  to  it. 
The  popliteal  vein  possesses  from  one  to  four  valves  and  is  directly  continuous  above 
with  the  femoral  vein. 

In  addition  to  the  popliteal  vein,  the  popliteal  artery  has  two  other  smaller  veins 
accompanying  it.  The  external  one  (v.  comitans  lateralis)  has  its  origin  from  the 
veins  issuing  from  the  outer  head  of  the  gastrocnemius  and  the  soleus,  and  passes 
upward  along  the  outer  surface  of  the  artery  to  open  into  the  popliteal  vein  at  about 
the  middle  of  its  course.  The  inner  vena  comitans  (v.  comitans  medialis)  is  formed 
by  the  veins  issuing  from  the  inner  head  of  the  gastrocnemius  and  ascends  along  the 
inner  side  of  the  artery,  making  connections  with  the  inferior  and  superior  internal 
articular  veins,  to  open  into  the  popliteal  vein  just  below  the  opening  in  the  adductor 
magnus. 

Tributaries. — The  majority  of  the  tributaries  of  the  popliteal  vein  correspond 
to  the  branches  of  the  popliteal  artery, — that  is  to  say,  they  are  articular  and 
muscular.  In  addition  it  receives  the  short  saphenous  vein  at  about  the  middle  of 
its  course. 

Variations. — The  popliteal  vein  may  be  considerably  shorter  than  usual  owing  to  the  fail- 
ure of  the  tibial  veins  to  unite  at  the  customary  level.  Not  infrequently  the  vein  is  double 
throughout  a  portion  of  its  course,  more  rarely  throughout  its  entire  length,  and  it  occasionally 
lies  beneath  (i.e.,  anterior  to)  the  artery. 

It  normally  communicates  by  means  of  its  tributaries  with  branches  of  the  deep  femoral 
vein,  and  occasionally  this  communication  becomes  so  large  that  the  popliteal  seems  to  bifurcate 
above,  one  branch  becoming  continuous  with  the  femoral  and  the  other  with  the  deep 
femoral.     More  interesting  from  the  historical  stand-point  are  the  rare  cases  in  which  the  vein 


912 


HUMAN   ANATOMY. 


ascends  the   back  of  the  thigh  along  with   the  sciatic  nerve,  either  uniting  above  with  one 
of  the  branches  of  the  deep  femoral  or  continuing  into  the  pelvis  with  the  nerve  to  become  a 

Fig.  76S. 


Semitendinosus  muscle 

Popliteal  artery 
Semimembranosus  muscle 

Azygos  articular  vein 

Communication  with 

internal  saphenous  vein 

Popliteal  veil 
External  saphenous  vein 


Popliteus  muscl 


Posterior  tibial  artery 
Communication  between 
anterior  and  posterior 

tibial  veins 


Posterior  tibial 


Communication  with 
deep  femoral  ve 


Plantaris  muscle 


Anterior  tibial  vein 
Anterior  tibial  artery 
Soleus,  cut  surface 


Deep  fascia,  cut  edge 


Veins  of  right  popliteal  space. 


tributary  of  the  internal  iliac  vein.     This  last  arrangement  recalls  an  anomaly  occasionally  pre- 
sented by  the  sciatic  artery  (page  815),  and  is  probably  due  to  the  same  embryological  conditions. 


THE  VEINS   OF   THE   LOWER   LIMB. 
The  Femoral  Vein. 


9i3 


The  femoral  vein  (v.  feinoralis)  (Fig.  769)  accompanies  the  femoral  artery 
from  the  opening  in  the  adductor  muscle  through  Hunter's  canal  and  Scarpa's 
triangle  to   its  beginning  at  the  lower  border  of  Poupart's  ligament.      It  is  a  single 

Fig.  769. 


Anterior 

superior  spine  of  ilium 


Sartorius,  cut 

Femoral  artery 

Rectus  femoris,  cut 


External  circumflex  vein1 
Deep  femoral 


Rectus  femoris,  cut 


Anastomotica  magna  vein 


Patella, 

displaced  outwardly 


Superficial  epigastric  vein 
Poupart's  ligament 
External  pudic  vein 

Pectineus  muscle 
Dorsal  vein  of  penis 

Internal  saphenous  vein 


Femoral  artery 

Tendon  of  adductor  magnus 


Right  femoral  vein  and  its  tributaries. 

58 


9i4  HUMAN   ANATOMY. 

trunk  and  is  the  direct  continuation  of  the  popliteal  vein  below,  and  it  terminates  by 
becoming  continuous  with  the  external  iliac  vein  above.  In  its  lower  part  it  lies 
slightly  external  to  the  artery,  but  throughout  the  greater  part  of  its  course  it  rests 
upon  the  posterior  surface  of  the  artery  and  is  enclosed  in  a  common  sheath  with  it. 
Above  it  inclines  somewhat  inwardly  and  comes  to  lie  upon  the  inner  surface  of  the 
artery,  between  it  and  the  femoral  canal.  It  possesses  from  one  to  five  pairs  of 
valves,  the  most  constant  pair,  present  in  81  per  cent,  of  cases,  being  situated  in  the 
upper  5  cm.  of  the  vein  and  consequently  controlling  the  flow  from  all  the  veins  of 
the  lower  limb. 

Tributaries. — The  tributaries  of  the  femoral  vein  correspond  with  the  branches 
of  the  femoral  artery,  although  some  of  them  communicate  with  the  vein  only  indirectly, 
opening  primarily  into  the  long  saphenous  vein,  which  is  itself  a  tributary  of  the 
femoral.  Thus,  the  long  saphenous  usually  receives  the  external  pudic,  superficial 
circumflex  iliac,  and  superficial  epigastric  veins,  and  these  will  be  described  later 
with  the  saphenous  veins.  Of  the  remaining  tributaries,  (i)  the.  deep  femoral,  (2) 
the  vents  co?nites,  and  (3)  the  anastomotica  magna,  the  first  two  deserve  special 
mention. 

1.  The  Deep  Femoral  Vein. — The  deep  femoral  vein  (v.  profunda  femoris) 
accompanies  the  deep  femoral  artery,  and,  like  it,  receives  as  tributaries  perforating 
veins  (vv.  perforantes)  which  take  their  origin  upon  the  posterior  surface  of  the 
adductor  muscles  and  anastomose  with  one  another,  with  tributaries  of  the  popliteal 
below  and  with  the  sciatic  above.  The  lowest  perforating  vein,  which  represents  the 
actual  beginning  of  the  deep  femoral,  has  communicating  with  it  one  of  the  terminal 
branches  of  the  short  saphenous  vein.  The  deep  femoral  vein  also  receives  the 
internal  and  external  circumflex  veins  (vv.  circumflexa  femoris  medialis  et 
lateralis)  which  accompany  the  corresponding  arteries  as  their  vense  comites,  the 
internal  circumflex  anastomosing  with  the  sciatic  and  obturator  veins  and  so 
providing  for  a  possible  collateral  circulation  between  the  internal  and  external  iliac 
veins.  The  deep  femoral  opens  into  the  femoral  usually  about  4-5  cm.  below 
Poupart's  ligament,  but  not  infrequently  at  a  somewhat  higher  level,  and  the 
circumflex  veins  may  open  directly  into  the  femoral  instead  of  into  the  deeper  vein. 

2.  The  Venae  Comites. — The  venae  comites  of  the  femoral  artery  are  two  or 
three  small  stems  which  run  parallel  with  the  artery  and  vein  through  Hunter's 
canal.  One  lies  to  the  inner  side  of  the  artery  (v.  eomitans  medialis)  and  the  other 
to  the  outer  side  (v.  eomitans  lateralis),  and  when  a  third  is  present  it  accompanies 
the  long  saphenous  nerve.  They  communicate  with,  or  in  some  cases  receive,  the 
veins  issuing  from  the  adjacent  muscles  and  open  into  the  femoral  vein,  usually  a 
little  below  the  point  where  it  receives  the  deep  femoral  vein. 

Variations. — The  portion  of  the  femoral  vein  above  the  entrance  of  the  deep  femoral  is 
sometimes  termed  the  common  femoral  vein  and  the  rest  of  it  the  superficial  femoral,  the 
common  femoral  being  formed  by  the  union  of  the  superficial  and  deep  veins. 

Occasionally  the  vein  lies  anterior  to  the  artery  throughout  a  considerable  portion  of  its 
course,  and  it  may  be  double  to  a  greater  or  less  extent,  the  two  veins  in  such  cases  either  lying 
posterior  to  the  artery  or  one  on  either  side  of  it. 

It  occasionally  passes  up  the  leg  behind  the  adductor  magnus,  passing  through  the  muscle 
where  it  is  normally  perforated  by  one  of  the  perforating  veins,  this  arrangement  being 
apparently  due  to  the  enlargement  of  a  connection  with  the  deep  femoral  and  of  the  anastomosis 
between  the  perforating  veins.  In  such  cases  the  femoral  artery  is  accompanied  by  one  or  two 
small  stems,  perhaps  representing  the  venae  comites,  and  in  those  cases  in  which  the  popliteal 
vein  passes  up  the  back  of  the  thigh  (page  911 )  the  femoral  is  also  greatly  reduced  in  size. 

THE  SUPERFICIAL  VEINS. 

The  Superficial  Veins  of  the  Foot. 

It  has  already  been  pointed  out  (page  910)  that  the  dorsal  and  plantar  digital 
veins  may  be  grouped  either  with  the  superficial  or  deep  veins  of  the  foot,  since  they 
communicate  extensively  with  both  sets.  The  superficial  connections  of  the  plantar 
digitals  are  with  an  arcus  venosus  plantaris  cutaneus  which  runs  across  the  foot  at  the 
bases  of  the  toes  and,  bending  upward  over  the  edges  of  the  foot,  communicates  with 
the  dorsal  veins.      Posteriorly  to  this  arch  is  a  subcutaneous  net-work  (rete  venosum 


THE  VEINS    OF    THE    LOWER    LIMB. 


9'5 


Fig.  770. 


Biceps 
Popliteal  vein 


plantare  cutaneum)  which  is  especially  close  in  the  fatty  pad  beneath  the  heel,  but  more 
open  towards  the  bases  of  the  toes.  This  net-work  makes  numerous  connections 
with  the  deep  plantar  veins,  and  to  a  great  extent  is  drained  by  superficial  emissaries 
which  pass  upward  over  the  borders  of  the  foot  and  open  into  the  superficial  dorsal 
veins.  These  emissaries  are  larger  on  the  inner  than  on  the  outer  side  of  the  foot,  and 
they  all  have  a  somewhat  backward  as  well  as  an  upward  direction,  those  from  the 
most  posterior  portions  of  the  plexus  passing  directly  backward  and  upward  over 
the  tuberosity  of  the  heel.  Anteriorly  the  more  central  portions  of  the  net-work  drain 
into  the  superficial  plantar  arch  and  communicate  through  this  with  the  dorsal  veins. 
The  dorsal  digital  veins  form  by  their  union  in  pairs  the  common  digital  veins 
(vv.  digitales  communes  pedis),  which  correspond  in  position  to  the  dorsal  interosseous 
veins,  except  that  they  are  subcutaneous.  Posteriorly  these  veins  anastomose  to  from 
a  more  or  less  regular  dorsal  subcu- 
taneous arch  (arcus  venosus  dorsalis 
pedis),  which  extends  across  the  dorsal 
portions  of  the  metatarsal  bones,' being 
convex  distally  and  increasing  in  size 
from  the  outer  to  the  inner  border  of 
the  foot.  Proximally  to  this  arch  there 
is  an  irregular  net-work  of  veins  (rete 
venosum  dorsale  pedis)  which  makes 
numerous  connections  with  the  deep 
veins  and  passes  proximally  into  the 
net-work  of  the  anterior  surface  of  the 
crus.  Towards  the  borders  of  the  foot, 
and  forming  the  lateral  and  medial 
boundaries  of  the  net-work,  a  more  or 
less  distinct  longitudinal  marginal 
vein  can  be  seen  on  each  side  (vv. 
marginales  lateralis  et  medialis),  and  it  is 
into  these  that  the  superficial  emissaries 
from  the  plantar  net-work  open  from 
below.  The  internal  marginal  vein  is 
somewhat  larger  than  the  external  and 
joins  the  dorsal  arch  to  form  the  long 
saphenous  vein,  while  the  external  is  the 
principal  origin  of  the  short  saphenous. 

The  Short  Saphenous  Vein. 

The  short  or  external  saphenous 
vein  (v.  saphena  parva)  (Fig.  770)  is  the 
superficial  vein  of  the  back  of  the  crus. 
It  begins  behind  the  external  malleolus 
at  the  upward  continuation  of  the  ex- 
ternal marginal  vein  of  the  foot.  It  lies 
at  first  upon  the  outer  border  of  the 
tendo  Achillis,  but  later  takes  a  more 
median  position  and  ascends  the  pos- 
terior surface  of  the  leg  almost  in  the 
median  line.  At  about  the  middle  of 
the  leg  it  perforates  the  crural  fascia 
and  continues  its  upward  course  in  the 
groove  between  the  two  heads  of  the 
gastrocnemius,  and,  entering  the  pop- 
liteal space,  terminates  by  dividing  into 

two  branches,  one  of  which  opens  into  the  posterior  surface  of  the  popliteal  vein 
about  on  a  level  with  the  origins  of  the  gastrocnemius,  while  the  other  passes 
farther  upward  to  communicate  with  the   beginning   of    the   deep  femoral   vein. 


Superfic 


9i6  HUMAN    ANATOMY. 

The  short  saphenous  vein  possesses  from  nine  to  ten  valves  in  its  course  up  the 
leg.  In  its  lower  part  it  accompanies  the  external  or  short  saphenous  nerve,  which 
lies  beneath  (i.e. ,  anterior  to)  it,  and  above  it  accompanies  a  branch  of  the  small 
sciatic  nerve. 

Tributaries. — The  short  saphenous  vein  drains  the  outer  border  of  the  foot 
and  the  whole  of  the  posterior  superficial  portion  of  the  crus.  Near  its  origin  it 
receives  the  posterior  emissaries  from  the  superficial  plantar  net-work,  and  throughout 
its  course  up  the  crus  it  receives  numerous  branches  from  the  superficial  net-work  of 
the  posterior  surface  of  that  portion  of  the  leg,  and  through  this  net-work  makes 
communications  with  the  long  saphenous  vein.  The  terminal  branch  which  com- 
municates with  the  deep  femoral  vein  receives  a  stem  known  as  the  v.  femoropoplitea, 
which  runs  downward  upon  the  back  of  the  thigh,  superficially,  receiving  branches 
from  the  posterior  superficial  net-work  of  the  thigh  and  communicating  above  with 
the  sciatic  and  gluteal  veins. 

Variations. — The  short  saphenous  vein  occasionally  opens  into  the  long  saphenous  by  the 
enlargement  of  one  of  the  anastomoses  between  the  two  veins,  only  a  small  vessel  representing 
its  communication  with  the  popliteal.  It  has  been  observed  to  continue  up  the  thigh  without 
or  with  but  a  small  communication  with  the  popliteal  and  deep  femoral  veins,  and,  entering  the 
pelvis  with  the  great  sciatic  nerve,  to  open  into  the  internal  iliac  vein.  In  such  cases  its  femoral 
portion  probably  represents  the  original  femoral  portion  of  the  sciatic  vein,  and  has  the  same 
significance  as  the  prolongation  of  the  popliteal  up  the  thigh,  of  which  mention  has  already  been 
made  (page  911). 

The  Long  Saphenous  Vein. 

The  long  or  internal  saphenous  vein  (v.  saptaena  magna)  (Fig.  771)  has  its 
origin  in  the  junction  of  the  inner  end  of  the  dorsal  arch  of  the  foot  with  the  inner 
marginal  vein.  It  passes  upward  in  front  of  the  inner  malleolus  and  then  in  the 
groove  between  the  medial  border  of  the  tibia  and  the  inner  border  of  the  gastrocne- 
mius muscle.  As  it  approaches  the  knee-joint  it  bends  slightly  backward  to  pass 
behind  the  internal  condyle  of  the  femur,  and  then  continues  up  the  thigh  in  an 
almost  direct  course  to  the  fossa  ovalis,  where  it  pierces  the  cribriform  fascia  and 
opens  into  the  femoral  vein. 

It  is  subcutaneous  throughout  its  entire  course  and  possesses  from  twelve  to 
eighteen  valves,  some  of  which,  especially  in  old  individuals,  are  apt  to  be  insufficient. 
Throughout  its  course  up  the  crus  it  accompanies  the  long  saphenous  nerve,  and  in 
the  thigh  it  lies  at  first  along  the  line  of  the  outer  (anterior)  edge  of  the  sartorius, 
but  later  crosses  that  muscle  obliquely  so  as  to  lie  internal  to  it  above. 

Tributaries. — At  its  origin  the  long  saphenous  vein  receives  some  of  the  more 
posterior  internal  emissaries  of  the  plantar  net-work,  and  in  its  course  up  the  crus  it 
receives  the  blood  from  all  those  portions  of  the  superficial  crural  net-work  which  do 
not  communicate  with  the  short  saphenous.  In  the  thigh  it  is  the  collecting  stem 
for  all  the  superficial  veins,  those  from  the  posterior  surface  frequently  uniting  to  form 
an  accessory  saphenous  vein  (v.  saphena  accessoria),  while  those  from  the 
anterior  surface  may  form  an  external  superficial  femoral  vein  (Fig.  771). 

Throughout  its  entire  course  it  makes  numerous  connections  with  the  deep  veins, 
with  the  anterior  tibial  by  some  five  or  six  branches  (vv.  sapheno-tibialcs  anteriores), 
with  the  posterior  tibial  by  usually  three  (vv.  sapheno-tibiales  posteriores) ,  and  with 
the  femoral  or  one  of  its  tributaries  by  usually  a  single  one.  Various  communications 
with  the  small  saphenous  also  occur. 

In  addition  to  these  various  connections,  the  long  saphenous  receives,  just 
before  its  entrance  into  the  femoral,  a  number  of  vessels  which  accompany  some  of 
the  superficial  branches  of  the  femoral  artery.  They  are  by  no  means  constant 
tributaries  of  the  saphenous,  but  frequently  pass  through  the  cribriform  fascia  to 
open  directly  into  the  femoral  vein. 

1.  The  External  Pudic  Veins. — The  external  pudic  veins  (vv.  pudendae 
externae)  are,  like  the  corresponding  arteries,  two  in  number,  one  superficial  and 
one  deep.  They  have  their  origin  in  the  external  genitals,  receiving  numerous 
veins  from  the  anterior  surface  of  the  scrotum  (vv.  scrotales  anteriores)  or  the 
anterior  portions  of  the  labia  majora  (vv.  labiales  anteriores).     They  also  receive  a 


THE  VEINS   OF   THE   LOWER   LIMB. 


917 


Superficial 
epigastric  vein 


of  penis 


saphenous  vein 


single  or  paired  vein  which  runs  along  the  dorsal  surface  of  the  penis  or  clitoris 
immediately  beneath  the  integment  (v.  dorsalis  penis  (clitoridis)  subcutanea),  and  at 
the  symphysis  pubis  bends  later- 
ally to  join  the  external  pudics. 

2.  The  Superficial  Cir- 
cumflex Iliac  Vein. — The 
superficial  circumflex  iliac  vein 
(v.  circumflexa  ilium  superficialis) 
accompanies  the  artery  of  the 
same  name,  receiving  subcuta- 
neous branches  from  the  lower 
lateral  portions  of  the  abdomen 
and  from  the  anterior  hip  region. 
It  frequently  unites  with  the 
superficial  epigastric  vein  before 
opening  into  the  saphenous. 

3.  The  Superficial  Epi- 
gastric Vein. — The  superficial 
epigastric  vein  (v.  epigastrica 
superficialis)  takes  its  origin  from 
the  subcutaneous  veins  of  the 
lower  part  of  the  anterior  abdom- 
inal wall  as  high  as  a  little  above 
the  umbilicus.  It  is  joined  at  a 
varying  level  by  the  thoraco- 
epigastric vein  (Fig.  775),  which 
opens  above  into  the  axillary 
vein,  and  is  occasionally  pro- 
longed downward  to  open 
independently  into  the  long 
saphenous. 

Variations. — The  long  saphe- 
nous vein  may  perforate  the  fascia 
lata  some  distance  below  the  fossa 
ovalis.  It  is  not  infrequently  replaced 
in  the  crural  portion  of  its  course  by  a 
net-work  of  veins  in  which  no  special 
main  stem  can  be  recognized,  and  in 
the  thigh  it  is  occasionally  double. 

Practical  Considerations. 
— The  Iliac  Veins  and 
the  Veins  of  the  Lower 
Extremity. 

The  common  iliac  veins 

illustrate  the  rule  (Owen)  that 
below  the  diaphragm  the  veins  of 
the  trunk  are  on  a  plane  posterior 
to  the  arteries  (except  the  renal) 
and  incline  generally  to  the 
venous — the  right — side.  Thus 
the  left  common,  iliac  is  always 
on  the  inner  (right)  side  of  the 
corresponding  artery  and  ulti- 
mately crosses  the  right  artery, 
on  a  posterior  plane.      The  right 

vein  begins  slightly  to  the  inner  side  of  the  right  artery,  which  it  crosses — 
on  a  posterior  plane — to  reach  the  right  side  of  the  fifth  lumbar  vertebra.  These 
relations   are   important  in   operations    on   the   common   iliac  arteries    (page  808). 


9i 8  HUMAN    ANATOMY. 

The  internal  iliac  veins  may  become  involved  in  infections  of  any  of  the 
numerous  plexuses  from  which  their  tributaries  arise.  Thus,  puerperal  metritis 
may  not  only  lead  to  pelvic  cellulitis  (page  2014),  but  may  set  up  a  thrombo-phlebitis 
in  the  intra-uterine  veins  which,  spreading  to  the  internal  and  common  iliac  veins, 
will  obstruct  the  venous  current  from  the  whole  lower  extremity,  bringing  about  a 
wide-spread  cedema,  with  aching  and  tenderness  (phlegmasia  alba  dolens,  milk  leg). 
Similar  conditions  sometimes  follow  septic  infection  of  the  prostatic  vesical  and 
hemorrhoidal  plexuses.  The  practical  relations  of  these  venous  channels  have  been 
described  in  connection  with  the  prostate,  bladder,  and  rectum.  The  branches 
of  the  internal  iliac  vein  aid  indirectly  in  supporting  the  pelvic  viscera.  They  are 
apt  to  be  varicose  in  the  aged,  especially  in  females.  They  supply  the  blood  in 
cases  of  pelvic  hsematocele. 

The  external  iliac  vein  is  frequently  involved  in  femoral  phlebitis,  the 
continuity  of  direction  and  calibre  between  it  and  the  femoral  being  practically 
unbroken. 

The  femoral  vein  is  not  infrequently  the  subject  of  thrombo-phlebitis,  descend- 
ing, as  a  result  of  some  form  of  pelvic  infection  (vide  supra),  or  ascending,  following 
septic  infection  of  the  soft  parts  or  bones  of  the  lower  extremity  ;  or  occasionally 
directly  caused  by  contusion  of  the  vessel  just  below  the  groin,  or  by  its  bruising 
during  forced  flexion  of  the  thigh.  Femoral  phlebitis  is  not  uncommonly  a  sequel 
of  enteric  fever  and  of  other  exhausting  diseases,  and  is  a  familiar  post-operative 
complication  of  operations  for  the  removal  of  the  appendix,  the  uterus,  the  tubes  and 
ovaries,  and  other  abdomino-pelvic  procedures,  even  when  apparently  unattended  by 
infection.  The  predisposing  causes  are  thought  to  be  the  relative  immobility  of  the 
patient  and  the  consequent  sluggishness  of  the  circulation,  especially  in  the  lower 
extremities,  the  dependent  position  of  the  limb  in  bed,  and  the  altered  constitution 
of  the  blood  (in  the  case  of  fever)  ;  the  exciting  cause  is  probably  a  very  slight 
degree  of  infection.  Pain  and  cedema  follow,  but  such  cases  almost  always  do  well. 
On  account  of  its  nearness  to  the  artery,  both  vessels  are  often  wounded  at  the  same 
time,  with  the  resulting  formation — if  the  communication  between  them  is  direct — 
of  an  aneurismal  varix  ;  or  if  it  is  indirect — an  aneurismal  sac  intervening — of  a 
varicose  aneurism.  Wounds  requiring  ligation  and  sudden  occlusion  of  the  vein 
from  any  cause  are  dangerous  from  the  risk  of  development  of  moist  gangrene. 
Lateral  suture  of  wounds  in  this  vein  has  been  successfully  employed  in  a  number  of 
instances.  The  femoral  vein  is  not  infrequently  involved  in  ulcerative  malignant 
or  phagedenic  processes  implicating  the  skin  of  the  groin  and  upper  thigh,  or  the 
inguinal  lymphatic  nodes. 

After  ligation,  the  collateral  circulation  is  established  between  the  veins  of  the 
buttocks  and  the  internal  circumflex  veins,  and  between  the  veins  of  the  pelvis  and 
the  external  pudic  veins. 

The  practical  relations  of  the  femoral  vein  to  femoral  hernia  have  been  described 
(page  1773). 

The  popliteal  vein,  together  with  the  artery  (which  is  closer  to  the  bone,  and 
therefore  more  easily  compressed  or  torn),  has  been  lacerated  in  supracondyloid 
fracture  of  the  femur.  It  has  been  so  compressed  by  a  popliteal  aneurism  as  to  cause 
thrombosis  and  enormous  distention  of  the  veins  and  of  the  leg.  Owing  to  the 
unyielding  character  of  the  boundaries  of  the  ham,  it  may  also  be  sufficiently  com- 
pressed by  inflammatory  exudates,  by  abscess,  or  by  enlarged  bursae,  to  cause 
swelling  and  cedema  of  the  foot  and  leg.  The  vein  is  so  exceptionally  thick-walled 
that  in  spite  of  its  more  superficial  position  it  is  never  ruptured  alone,  but  only  when 
the  force  is  sufficient  to  tear  the  artery  also.  The  involvement  of  both  may  be  favored 
by  the  fact  that  the  two  vessels  are  so  closely  united  that  it  is  difficult  to  separate  them, 
and  this  also  favors  the  occasional  production  of  aneurismal  varix  or  varicose 
aneurism  after  stab-wounds.  This  close  connection  makes  the  denudation  of  the 
artery  difficult  in  the  operation  for  its  ligation. 

The  veins  of  the  leg  are,  with  the  possible  exception  of  the  veins  of  the 
pampiniform  and  hemorrhoidal  plexuses,  more  often  the  subject  of  varicosity  than 
any  other  veins  of  the  body.  This  is  due  to  ( 1 )  the  high  blood-pressure  in  these 
veins,  resulting  from  (a)  the  erect  posture  of  the  human  species  and  the  consequent 


THE   PORTAL  SYSTEM.  919 

vertical  position  of  these  veins  ;  (6)  the  length  of  the  column  of  blood  they  carry, 
extending,  in  the  case  of  the  long  saphenous  vein,  from  its  beginning  at  the  ankle  to 
the  upper  orifice  of  the  inferior  vena  cava  ;  (c)  in  many  cases  to  compression  above, 
as  from  abdominal  or  pelvic  growths,  or  the  gravid  uterus,  or  from  garters.  (2)  In 
the  superficial  veins  the  frequency  of  varicosity  is  also  due  to  the  lack  of  adequate 
external  support  to  their  thin  and  distensible  walls,  the  saphenous  veins,  for  example, 
lying  outside  of  the  deep  fascia  in  loose  connective  tissue.  (3)  To  the  increased 
resistance  that  must  be  overcome  at  the  points  where  the  deep  and  superficial  vessels 
communicate,  and  where  in  many  cases  the  varicosity  seems  to  begin.  At  such 
points  the  upward  current  of  blood  has  to  overcome — and  the  walls  of  the  veins  to 
support — not  only  the  downward  pressure  of  the  vertical  column  of  blood  in  the 
vessels  above  it,  but  also  the  resistance  of  the  blood-stream  driven  out  of  the  deep 
vein  by  the  contracting  muscles  between  which  it  lies,  and  entering  the  superficial 
vein  at  a  right  angle.  The  valve  next  below  this  point  of  entrance  prevents  the  relief 
that  might  be  obtained  from  temporary  distention  of  a  long  lower  section  of  the  vein 
and  limits  these  forces  to  a  circumscribed  area,  which  yields  and  becomes  varicose. 

The  venous  plexus  between  the  two  layers  of  the  muscles  of  the  calf  is  often  the 
seat  of  varices  of  great  size.  The  six  chief  veins  which  pass  from  the  soleus  muscle 
alone  to  enter  into  the  posterior  tibial  and  peroneal  trunks  have  a  united  diameter 
of  not  less  than  one  inch  (Treves). 

The  fact  that  each  of  the  saphenous  veins  is  accompanied  by  a  sensory  nerve 
accounts  for  the  aches  and  pains  associated  with  varicosity. 

THE  PORTAL  SYSTEM. 

The  portal  system  is  composed  of  all  the  veins  which  have  their  origin  in  the 
walls  of  the  digestive  tract  below  the  diaphragm  (with  the  exception  of  those  of  the 
lower  part  of  the  rectum)  and  includes  also  the  veins  which  return  the  blood  from 
the  pancreas,  spleen,  and  gall-bladder.  It  presents  a  marked  peculiarity  in  that  the 
system  begins  and  ends  in  capillaries,  the  blood  which  it  contains  having  entered  its 
constituent  veins  from  the  capillaries  of  the  intestine,  stomach,  and  the  other  organs 
mentioned  above,  and  passing  thence  to  the  liver,  where  it  traverses  another  set 
of  capillaries,  by  which  it  reaches  the  hepatic  veins  and  so  the  heart.  Coming  as 
it  does  principally  from  the  intestine,  the  portal  blood  is  more  or  less  laden  with 
nutritive  material,  which  has  been  digested  and  absorbed  through  the  intestinal 
walls,  but  is  not  yet  in  a  condition,  so  far  as  some  of  its  constituents  are  concerned, 
suitable  for  assimilation  by  the  tissues.  To  undergo  the  changes  necessary  for  its 
conversion  into  assimilable  material  it  is  carried  by  the  portal  vein  to  the  liver,  and  as  it 
passes  through  the  capillaries  of  that  organ  it  undergoes  the  necessary  modifications. 

In  other  words,  the  portal  vein  stands  in  a  somewhat  similar  relation  to  the  liver 
that  the  pulmonary  vein  does  to  the  lungs.  Its  purpose  is  not  to  convey  material  to 
the  organ  for  its  nutrition,  that  being  accomplished  by  the  hepatic  arteries  for  the 
liver  just  as  it  is  accomplished  by  the  bronchial  arteries  for  the  lungs,  but  to  carry  to 
the  liver  crude  material  upon  which  the  organ  may  act,  elaborating  it  and  returning 
it,  as  required,  to  the  circulation  in  a  purified  and  assimilable  condition. 

The  inclusion  of  the  veins  of  the  spleen,  gall-bladder,  and  pancreas,  or  even  of 
those  of  the  rectum,  in  the  portal  system  is  to  be  explained  on  the  ground  of  topo- 
graphic relationship  rather  than  on  the  basis  indicated  above. 

The  main  stem  of  the  portal  system  will  first  be  described  and  then  its  tributaries 
in  succession. 

The  Portal  Vein. 

The  portal  vein  (v.  portae)  (Figs.  772,  774)  is  formed  behind  the  head  of  the 
pancreas  by  the  union  of  the  superior  mesenteric  and  splenic  veins,  the  latter  receiving 
the  inferior  mesenteric  vein  shortly  before  its  union  with  the  superior  mesenteric. 
The  two  veins  unite  almost  at  a  right  angle,  and  from  their  point  of  union  the  portal 
vein  passes  obliquely  upward  and  to  the  right,  along  the  free  edge  of  the  lesser 
omentum,  towards  the  transverse  fissure  of  the  liver.  There  it  divides  into  two 
trunks,  of  which  the  right  is  the  larger  and  shorter  and  quickly  bifurcates  into 
an  anterior  and   a  posterior   branch.      It  is  distributed  to   the  whole  of   the  right 


920 


HUMAN    ANATOMY. 


lobe  of  the  liver  and  to  the  greater  part  of  the  Spigelian  and  quadrate  lobes,  the 
remainder  of  these  lobes  and  the  left  lobe  receiving  branches  from  the  left  trunk. 

The  trunks  of  the  vein  or  their  branches  enter  the  substance  of  the  liver  and 
divide  in  a  more  or  less  distinctly  dichotomous  manner  to  form  interlobular  veins, 
which,  as  their  name  indicates,  occupy  a  position  between  the  lobules  of  the  organ, 
and  give  off  capillaries  which  traverse  the  lobule  and  empty  into  the  intralobular 
veins,  the  origins  of  the  hepatic  veins. 

The  portal  vein  measures  about  8  cm.  (3^  in. )  in  length  and  has  a  diameter  of 
from  1.5  to  2  cm.  Its  walls,  especially  in  its  upper  portion,  contain  a  considerable 
quantity  of  muscle-tissue  and  it  is  destitute  of  valves. 

Relations. — At  its  origin  the  portal  vein  lies  behind  the  head  of  the  pancreas 
and  to  the  left  of  the  vena  cava  inferior.      As  it  ascends  it  comes  to  lie  at  first  behind 


Fig.  772. 


Komi'l  li^.Tnienl  uf  ] 


and  its  tiiltiit.tri 


has  been  pulled  upward. 


the  first  portion  of  the  duodenum  and  then  between  the  two  layers  of  the  lesser 
omentum.  In  this  latter  portion  of  its  course  it  is  associated  with  the  hepatic  artery 
and  the  common  bile-duct,  both  of  which  lie  anterior  to  it,  the  artery  to  the  left  and  the 
duct  to  the  right.  It  enters  the  transverse  fissure  towards  its  right  extremity,  hence 
the  shortness  of  the  right  trunk  compared  with  the  left,  and  its  trunks  have  in  front 
of  them  the  branches  of  the  hepatic  artery,  the  hepatic  ducts  lying  anterior  to  these. 
Tributaries. — The  tributaries  of  the  portal  vein  are  :  (1)  the  superior  mesen- 
teric, (2)  the  splenic,  (3)  the  inferior  7nesenteric,  (4)  the  gastric,  (5)  the  pyloric, 
and  (6)  the  cystic  veins.  In  addition  to  these  principal  tributaries,  the  portal  vein,  or 
its  branches  within  the  liver,  also  receives  a  number  of  small  veins  which  have  their 
origin  in  the  falciform  ligament  of  the  liver  and  in  the  lesser  omentum, -and,  further- 
more, it  receives  at  the  transverse  fissure  (7)  some parumbi/ical  veins  which  ascend 
the  anterior  abdominal  wall  along;  with  the  round  ligament. 


THE   PORTAL  SYSTEM.  921 

1.  The  Superior  Mesenteric  Vein. — The  superior  mesenteric  vein  (v.  mesen- 
terica  superior)  (Fig.  773)  accompanies  the  artery  of  the  same  name,  lying  upon  its 
right  side.  It  has  its  beginning  somewhere  in  the  neighborhood  of  the  terminal 
portion  of  the  ileum  and  ascends  in  the  line  of  attachment  of  the  mesentery.  Above, 
it  passes  over  the  third  portion  of  the  duodenum  and  then  between  that  portion 
of  the  intestine  and  the  lower  border  of  the  pancreas,  uniting  behind  the  head  of  the 
pancreas  with  the  splenic  vein  to  form  the  portal  vein.      It  possesses  no  valves. 

Tributaries. — The  tributaries  of  the  superior  mesenteric  vein  correspond  with  the  branches 
of  the  corresponding  artery,  except  that  it  receives  in  addition  the  pancreatico-duodenal  and 
right  gastro-epiploic  veins  which  accompany  the  similarly  named  branches  of  the  hepatic  artery. 

(a)  The  veins  of  the  small  intestine  (vv.  intestinales)  have  their  origin  in  the  walls  of  the 
small  intestine  from  the  last  portion  of  the  duodenum  to  within  a  short  distance  of  the  ileo-caecal 
valve.  Their  arrangement  is  essentially  similar  to  that  of  the  arteries  of  the  small  intestine,  the 
numerous  small  branches  which  emerge  from  the  intestine  being  united  by  transverse  anasto- 
moses, as  a  rule  more  numerous  than  those  of  the  arteries,  and  forming  one  or  more  series  of 
venous  arcades  lying  between  the  two  layers  of  the  mesentery.  From  these  arcades  branches 
arise  which  pass  towards  the  superior  mesenteric  vein,  gradually  uniting  to  form  about  twenty 
stems  which  open  independently  into  the  superior  mesenteric.  The  branches  of  origin  of  the 
intestinal  veins,  just  after  they  emerge  from  the  intestine  are  provided  with  valves  in  the  child, 
but  they  usually  degenerate  more  or  less  completely  before  adult  life. 

(6)  The  ileo-colic  vein  (v.  ileocolica)  arises  at  the  junction  of  the  ileum  and  cascum  by  the 
union  of  a  caecal  and  an  ileal  branch,  the  latter  of  which  anastomoses  with  the  origin  of  the 
superior  mesenteric.  The  caecal  branch  receives  an  appendicular  vein  from  the  appendix  vermi- 
formis,  and  the  main  stem  passes  upward  between  the  two  layers  of  the  mesentery  to  open  into 
the  superior  mesenteric  just  before  it  passes  over  the  duodenum. 

(c)  The  right  colic  veins  (vv.  colicae  dextrae)  originate  in  the  walls  of  the  ascending  colon 
and  are  two  or  three  in  number.  They  anastomose  by  transverse  branches  with  the  ileo-colic  and 
middle  colic  veins  and  pass  almost  horizontally  medially  to  open  into  the  superior  mesenteric. 

(d)  The  middle  colic  vein  (v.  colica  media)  emerges  from  the  transverse  colon  by  a 
number  of  small  branches  which  anastomose  to  the  right  and  left  with  the  right  and  left  colic 
veins,  and  unite  to  a  single  stem  which  opens  into  the  superior  mesenteric  just  before  it  passes 
beneath  the  pancreas. 

(e )  The  right  gastro-epiploic  vein  (v.  gastroepiploica  dextra)  runs  from  left  to  right  along 
the  greater  curvature  of  the  stomach,  communicating  directly  with  the  left  gastro-epiploic  at 
about  the  middle  of  the  curvature.  It  receives  tributaries  from  the  lower  portions  of  the 
anterior  and  posterior  surfaces  of  the  stomach  and  from  the  greater  omentum,  and  opens  into 
the  superior  mesenteric  shortly  before  its  union  with  the  splenic.  It  occasionally  receives  a 
pancreatico-duodenal  vein,  and  may  unite  with  the  middle  colic  vein  to  form  a  gastro-colic 
vein  instead  of  opening  directly  into  the  superior  mesenteric. 

(f)  The  pancreatico-duodenal  veins  (vv.  pancreaticoduodenales),  like  the  arteries,  may  be 
two  in  number,  one  of  which  opens  directly  into  the  superior  mesenteric  and  the  other 
into  the  right  gastro-epiploic.  Frequently,  however,  they  are  broken  up  into  a  number  of 
separate  vessels  arising  independently  from  each  of  the  two  viscera  concerned,  the  duodenum 
(vv.  duodenales)  and  the  head  of  the  pancreas  (vv.  pancreaticae). 

2.  The  Splenic  Vein. — The  splenic  vein  (v.  lienalis)  (Fig.  774)  is  formed  by 
the  union  of  five  or  six  branches  which  emerge  from  the  hilum  of  the  spleen.  It  passes 
almost  horizontally  to  the  right  below  the  splenic  artery,  resting  at  first  upon  the 
upper  border  of  the  pancreas,  but  later  coming  to  lie  behind  that  organ.  Behind  the 
head  of  the  pancreas  it  unites  with  the  superior  mesenteric  to  form  the  portal  vein. 

Tributaries. — These  correspond  with  the  branches  of  the  artery,  and  in  addition  it  receives 
near  its  termination  the  inferior  mesenteric  vein,  which  for  purposes  of  description  will,  however, 
be  regarded  as  independent. 

(a)  The  short  gastric  veins  (vv.  gastricae  breves)  arise  from  the  fundus  of  the  stomach  and 
pass  between  the  layers  of  the  gastro-splenic  omentum  to  open  partly  into  the  splenic  vein  and 
partly  into  its  branches  of  origin  as  they  emerge  from  the  hilum. 

(/>)  The  left  gastro-epiploic  vein  (v.  gastroepiploica  sinistra)  passes  from  right  to  left  along 
the  greater  curvature  of  the  stomach,  communicating  directly  with  the  right  gastro-epiploic  about 
half-way  along  the  curvature.  It  receives  branches  from  the  lower  portions  of  both  surfaces  of 
the  stomach  and  from  the  greater  omentum,  and  opens  into  the  splenic  vein  near  its  formation. 

(c)  The  pancreatic  veins  (vv.  pancreaticae),  which  maybe  five  or  more  in  number,  open 
into  the  splenic  vein  at  various  points  in  its  passage  behind  the  pancreas. 


922 


HUMAN    ANATOMY. 


3.  The  Inferior  Mesenteric  Vein. — The  inferior  mesenteric  vein  (v.  mesen- 
teriea  inferior)  (Fig.  774)  is  formed  by  the  junction  of  the  superior  hemorrhoidal  and 
sigmoid  veins  opposite  the  sigmoid  flexure  of  the  colon,  and  passes  upward  in 
company  with  the  corresponding  artery.  It  is  continued  on,  however,  beyond  the 
point  where  the  artery  arises  from  the  abdominal  aorta,  lying  behind  the  peritoneum 
slightly  medial  to  the  ascending  colon,  and,  finally,  it  passes  beneath  the  pancreas 


Fig.  773 


Transverse  colon 


nesenteric  vein  and  its  tributaries;    transverse  colon 
has  been  pulled  upward. 


to  open  usually  into  the  splenic  vein  not  far  from  its  union  with  the  superior 
mesenteric.  Occasionally  it  opens  into  the  latter  vein  (Fig.  774)  or  else  equally 
into  both,  thus  taking  a  direct  part  in  the  formation  of  the  portal  vein. 


Tributaries. — Its  tributaries  correspond  to  the  branches  of  the  artery. 

(a)  The  superior  hemorrhoidal  vein  (v.  haemorrhoidalis  superior)  has  its  origin  from  the 
upper  part  of  the  hemorrhoidal  plexus  by  several  branches,  and,  passing  upward,  unites  with  the 
sigmoid  veins  to  form  the  inferior  mesenteric.  Through  the  hemorrhoidal  plexus  it  communi- 
cates with  the  middle  and  inferior  hemorrhoidal  veins,  thus  placing  the  portal  and  inferior  caval 
systems  in  communication. 

(b)  The  sigmoid  veins  (w.  sigmoideae)  are  variable  in  number  and  pass  from  the  sigmoid 
flexure  and  the  lower  portion  of  the  descending  colon  to  the  inferior  mesenteric,  the  lowest  one 
uniting  with  the  superior  hemorrhoidal  to  form  that  vein. 


THE   PORTAL  SYSTEM.  923 

(c)  The  left  colic  vein  (v.  colica  sinistra)  has  its  origin  in  the  walls  of  the  descending  colon, 
anastomosing  above  with  the  middle  colic  and  below  with  the  sigmoid  veins.  It  passes  medially 
to  open  into  the  upper  part  of  the  inferior  mesenteric. 

4.  The  Gastric  Vein. — The  gastric  vein  (v.  coronaria  ventriculi)  (Fig.  772) 
accompanies  the  gastric  artery  along  the  lesser  curvature  of  the  stomach.  It  has  its 
origin  at  the  pyloric  end  of  the  stomach,  where  it  anastomoses  with  the  pyloric  vein, 
and  passes  at  first  from  right  to  left  along  the  lesser  curvature,  receiving  tributaries 
from  the  upper  part  of  both  surfaces  of  the  stomach.  At  the  opening  of  the 
oesophagus  into  the  stomach  it  makes  connections  with  the  oesophageal  veins,  and 
then  bends  upon  itself  and  passes  from  left  to  right  behind  the  posterior  wall  of  the 
lesser  sac  of  the  peritoneum,  and  terminates  either  in  the  portal  vein  or  in  the  splenic 
shortly  before  its  union  with  the  superior  mesenteric. 

The  peculiar  reflected  course  of  the  gastric  vein  is  readily  understood  if  it  be  remembered 
that  the  adult  position  of  the  stomach  is  a  secondary  one.  When  first  formed  the  long  axis  of 
the  stomach  is  practically  vertical,  the  pyloric  end  being  directed  downward,  and  a  vein  starting 
at  the  pylorus  will  have  a  direct  ascending  course  to  the  portal  vein.  When  the  stomach  as- 
sumes its  adult  position  the  course  of  the  vein  with  reference  to  the  viscus  does  not  alter,  and 
consequently  it  passes  from  pylorus  to  cardia,  and  must  then  bend  back  upon  itself  to  reach  the 
portal  vein. 

5.  The  Pyloric  Vein. — The  pyloric  vein  (v.  pylorica)  (Fig.  772)  accompanies 
the  pyloric  branch  of  the  hepatic  artery.  It  takes  its  origin  at  the  pyloric  end  of  the 
stomach,  where  it  anastomoses  with  the  gastric  vein,  and  passes  downward  to  open 
into  the  portal. 

6.  The  Cystic  Vein. — The  cystic  vein  (v.  cystica)  (Fig.  772)  returns  the 
blood  from  the  walls  of  the  gall-bladder  and  opens  usually  into  the  right  trunk  of  the 
portal  vein.      It  is  frequently  represented  by  two  separate  stems. 

7.  The  Parumbilical  Veins. — The  parumbilical  veins  (vv.  paruinbilicales)  are 
a  number  of  small  veins  which  have  their  origin  in  the  anterior  abdominal  wall  in  the 
neighborhood  of  the  umbilicus  and  pass  upward  in  the  fold  of  peritoneum  which 
contains  the  round  ligament  of  the  liver.  They  anastomose  below  with  both  the 
superficial  and  deep  epigastric  veins  and  also  with  small  vessels  which  pass  down- 
ward alongside  of  the  urachus  to  empty  into  the  vesical  plexus.  Above,  the  majority 
of  them  enter  the  quadrate  and  left  lobes  of  the  liver,  but  one  of  them,  the  vena 
supraumbilicalis,  enters  the  substance  of  the  round  ligament  at  a  varying  level  and 
opens  into  the  more  or  less  extensive  lumen  of  that  structure,  which  represents  the 
umbilical  vein  of  fcetal  life.  This  lumen  appears  to  persist  in  the  majority  of  cases, 
although  greatly  reduced  in  size  from  that  of  the  umbilical  vein,  and  may  extend 
throughout  almost  the  entire  length  of  the  round  ligament,  although  perhaps,  more 
usually,  it  is  limited  to  its  upper  part,  and  opens  into  the  right  trunk  of  the  portal 
vein.  When  the  lumen  is  entirely  obliterated  it  is  possible  that  the  supraumbilical 
vein,  which  has  also  been  termed  the  accessory  portal  vein,  may  open  directly  into 
the  portal  vein. 

Collateral  Circulation  of  the  Portal  Vein.— Considering  the  fact  that  the  portal  vein 
terminates  in  capillaries  in  the  substance  of  the  liver,  it  is  evident  that  certain  pathological 
conditions,  such  as  cirrhotic  changes,  which  may  occur  in  that  organ,  will  more  or  less  completely 
interfere  with  the  return  of  the  blood  to  the  heart  from  the  intestine,  spleen,  and  pancreas,  by 
producing  an  obliteration  of  the  capillaries.  The  possibilities  of  a  collateral  circulation  are 
therefore  important,  and  a  number  of  routes  occur  by  which,  under  stress,  the  blood  of  the 
portal  venous  system  may  pass  around  the  liver  and  reach  the  heart  through  one  of  the  other 
systems.  The  functional  capabilities  of  these  various  routes  are  furthered  by  the  fact  that  none 
of  the  tributaries  of  the  portal  vein  possess  valves  except  in  their  finer  branches,  and  the  blood 
can  therefore  flow  in  them  in  a  reverse  direction  if  necessary.  The  principal  collateral  routes 
are  as  follows  : 

1.  Through  the  gastric  vein  the  blood  may  pass  to  the  oesophageal  veins  and  thence  to  the 
azygos  and  hemiazygos  veins.  When  this  route  is  functional  the  oesophageal  veins  become 
enlarged  and  frequently  varicose,  forming  contorted  elevations  upon  the  surface  of  the  cesophagus. 

2.  Through  the  superior  hemorrhoidal  veins  connections  are  made  by  way  of  the  hemor- 
rhoidal plexus  with  the  hemorrhoidal  branches  of  the  internal  iliac.  These  connections  seem, 
however,  to  be  less  frequently  functional  than  either  the  cardiac  or  parumbilical  routes. 


924 


HUMAN    ANATOMY. 


3.  Through  the  umbilical  and  supraumbilical  veins  to  the  superficial  or  deep  epigastrics  and 
so  to  the  external  iliac  veins.  It  is  interesting  to  note  that  in  cases  where  this  route  is  functional 
the  enlargement  of  the  superficial  epigastric  veins  is  usually  accompanied  by  a  development  of 
varicosities  upon  them,  while  this  is  not  the  case  with  the  deep  epigastrics.  An  explanation  of 
this  difference  has  been  found  in  the  fact  that  the  deep  veins,  before  opening  into  the  external 
iliac,  bend  slightly  backward,  so  that  their  orifices  are  directed  in  the  same  way  as  the  flow  of 
blood  in  the  larger  stem,  whereas  the  superficial  epigastrics  open  from  above  into  the  long 
saphenous  veins,  their  orifices  being  opposed,  therefore,  to  the  flow  of  blood  in  the  saphenous, 
— a  condition  which  naturally  predisposes  towards  stasis  of  the  blood  in  the  epigastrics  and,  it 
may  be  remarked,  also  of  that  in  the  saphenous. 

These  are  the  principal  routes,  but  it  must  be  noted  that  anastomoses  also  exist  between 
the  portal  system  and  the  phrenic  veins  by  means  of  the  small  veins  which  descend  towards  the 


Fig.  774. 


Suspensory  ligament 


Round  ligament 


under  surface 

Spigelian  lobe  of  liver 

'                   Crura  of  diaphragm 

J//                ~~y* ,           Phrenic 

vein 

Spleen 

x       ^JeS       ^s 

(which  typiualh 

^passes,  fartlu-i  t<. 

1  \Mr  the  right  to  open 

%r      into  the  portal 

d  tributaries  of  portal  vein;  stomach  and 
and  liver  pulled  upward. 


liver  in  the  falciform  ligament,  and  communications  with  the  inferior  caval  system  also  occur 
by  means  of  retroperitoneal  anastomoses  between  the  peritoneal  and  mesenteric  veins,  both  of 
which  are  quite  small.     These  communications  are  known  as  the  veins  of  Retzius. 

Finally,  it  may  be  mentioned  that  anomalous  and  therefore  inconstant  communications  of 
the  portal  branches  with  those  of  other  systems  have  been  observed.  Thus  the  gastric,  the 
short  gastrics,  or  the  pyloric  vein  may  anastomose  with  the  phrenics;  the  splenic  or  the  left 
gastro-epiploic  with  the  renals  ;  the  right  or  left  colic  with  the  branches  from  the  fatty  capsule  of 
the  corresponding  kidney  ;  and  the  duodenal  branches  may  open  into  the  inferior  vena  cava. 


THE   PORTAL  SYSTEM. 


925 


Practical  Considerations. — The  portal  system  may  be  obstructed  by  (a) 
tumors  or  swellings  involving  the  liver  itself,  as  carcinoma,  hydatids,  or  abscess  ;  {d) 
enlargement  of  the  gall-bladder  from  new  growth  or  from  concretions  ;  (c)  tumors 
of  contiguous  structures,  as  disease  of  lymph-nodes  in  the  portal  fissure  or  between 
the  layers  of  the  lesser  omentum,  or  carcinoma  of  the  head  of  the  pancreas  ;  (d ) 
disease  of  the  liver  tissue,  especially  cirrhosis  (chronic  interstitial  hepatitis)  in 
which  the  interlobular  veins  are  compressed  by  the  contraction   of  the  connective 


Fig.  775. 


External  jugular  vein 

Cephalic  vein 

Axillary  artery 
Axillary  1 


Superficial  veins  of  anterior  body-wall  j    pectoralis  and  external  intercostal  muscles  (of 
fifth  to  seventh  intercostal  spaces)  on  left  side  have  been   removed. 

tissue  in  the  spaces  between  the  lobules  ;  (<?)  valvular  disease  of  the  heart  leading  to 
backward  pressure  through  the  cava  and  hepatic  and  intralobular  veins  which  finally 
reaches  the  terminal  capillaries  of  the  portal  vein  and  then  the  interlobular  veins 
and  the  entire  portal  system,  resulting  in  some  cases  in  the  so-called  nutmeg  liver 
(cyanotic  atrophy).  The  consequences  of  portal  obstruction  are  various,  but  may,  as 
a  rule,  easily  be  understood  by  referring  each  symptom  to  its   anatomical   basis   in 


926 


HUMAN    ANATOMY. 


obstruction  of  one  or  the  other  of  the  venous  tributaries.  The  chief  results  are  : 
(i)  Enlargement  of  the  liver  itself,  at  first  congestive,  later  from  hyperplasia. 
Diminution  in  the  quantity  of  bile  or  alteration  in  its  character  may  cause  constipa- 
tion and  indigestion  ;  or  escape  of  its  coloring  matter  and  its  absorption  by  the 
hepatic  veins  may  give  rise  to  jaundice.  (2)  From  congestion  of  the  gastric  and 
intestinal  mucosa  (through  the  superior  and  inferior  mesenteric,  splenic,  and  gastric 
tributaries)  there  may  develop  indigestion,  flatulence,  eructations,  and  vomiting,  often 
bloody  ;  serous  exudation  into  the  bowel — intestinal  indigestion,  and  diarrhcea,  some- 
times with  black  stools  from  decomposed  blood — or  into  the  general  peritoneal 
cavity — ascites  ;  enlargement  and  tenderness  of  the  spleen  ;  hemorrhoids  (from  the 
communication  between  the  middle  and  inferior  hemorrhoidal  veins — systemic — and 
the  superior  hemorrhoidal  vein — portal)  ;  varicosities  in  the  lower  extremities,  possibly 
from  the  same  communication  between  the  caval  and  portal  systems,  but  oftener  from 
the  direct  interference  by  an  enlarged  liver  with  the  current  in  the  inferior  cava. 

Septic  inflammation  of  the  liver  may  reach  that  organ  through  any  of  the  portal 
tributaries.  It  is  not  uncommonly  the  result  of  infection  originating  during  a  dysen- 
teric attack.  Cancer  may  also  reach  the  liver  by  venous  channels,  usually  by  the 
gastric  or  hemorrhoidal  tributaries. 

As  the  number  of  extraperitoneal  anastomoses  between  the  branches  of  the 
parietal  vessels  (lower  intercostal,  phrenic,  lumbar,  ilio-lumbar,  epigastric  and  circum- 
flex iliac)  and  branches  of  vessels  that  supply  viscera  without  a  complete  peritoneal 
covering  (liver,  kidneys,  suprarenals,  duodenum,  pancreas,  ascending  and  descending 
colon)  are  of  great  importance  in  case  of  obstruction  to  the  visceral  arterial  supply, 
so  the  corresponding  venous  anastomoses  are  of  equal  or  greater  importance  in 
obstruction  of  the  portal  vein  or  of  the  inferior  cava.  The  occasional  connection 
between  a  parumbilical  vein  and  the  external  iliacs — through  the  epigastrics — may 
also  relieve  portal  obstruction.  The  above  anastomoses  explain  the  effect  of  leeches 
or  wet  cups  or  counter-irritation  of  the  surface  in  congestions  or  inflammations  of 
the  partly  extraperitoneal  viscera.      (Woolsey.) 

DEVELOPMENT  OF  THE  VEINS. 

The  embryonic  venous  system  may  be  regarded  as  consisting  of  three  sets  of  vessels. 
One  of  these  becomes  the  pulmonary  veins,  another  gives  rise  to  the  portal  and  umbilical  veins, 
while  the  third  is  represented  by  what  are  termed  the  cardinal  veins.  It  is  to  these  last  that 
attention  may  first  be  directed. 

The  Cardinal  Veins. — The  cardinal  veins  (Fig.  776)  are  two  longitudinal  stems  which 
extend  the  entire  length  of  the  body,  one  on  either  side  of  the  median  line,  receiving  throughout 

their  course  lateral  somatic  and  visceral  branches 
in  more  or  less  perfect  segmental  succession. 
From  each  vein  a  branch  passes  medially  towards 
the  heart,  and  the  portion  of  the  longitudinal 
vein  anterior  to  this  cross-branch  is  termed  the 
anterior  cardinal  or  primitive  jugular,  while 
that  behind  it  is  known  as  the  posterior  cardinal. 
The  cross-branch,  which  is  usually  described  as 
formed  by  the  union  of  the  anterior  and  pos- 
terior cardinals,  is  termed  the  duct  of  Cuvier. 

The  anterior  cardinals  take  their  origin 
from  veins  which  ramify  over  the  surface  of  the 
brain  and  receive  at  first  both  the  ophthalmic  and 
facial  veins.  The  cerebral  veins  later  condense 
to  form  the  superior  and  inferior  longitudinal, 
the  straight,  and  the  lateral  sinuses,  with  the  last 
of  which  the  ophthalmic  veins  unite,  their  intra- 
cranial portions  becoming  the  cavernous  and 
inferior  petrosal  sinuses.  The  facial  veins,  how- 
ever, sever  their  connection  with  the  cerebral 
veins  and  unite  with  other  superficial  veins  to 
form  the  external  jugular — a  vessel  which  in 
some  mammalia  reaches  a  high  degree  of  devel- 
opment, almost  or  entirely  replacing  the  internal  jugular,  which  represents  the  main  stem 
of  the  cardinal.     In  man  the  original  condition,  in  which  the  external  jugular  is  of  subordinate 


Venous  sinus  of  heart 
Duct  of  Cuvier 


Umbilical  vein 
Posterior  cardinal 


DEVELOPMENT   OF   THE   VEINS. 


927 


importance,  is  more  nearly  retained,  but  indications  of  a  transference  of  blood  from  the  intracranial 
portions  of  the  internal  jugular  system  to  the  external  vessel  are  to  be  seen  in  the  emissary  veins. 
At  first  each  internal  jugular  opens  independently  into  the  right  auricle  through  the 
corresponding  duct  of  Cuvier  (Fig.  777,  A) ,  but  later  a  communicating  branch  extending 
obliquely  across  from  the  left  to  the  right  vein  is  developed  (Fig.  777,  B),  and  thereafter  the 

Fig.  777. 


Anterior  cardinal        M 

(internal  jugular) 


Cuvierian  duct 
Primary  inf. 
Posterior  cardinal 


Internal  jugular 

I     H External  jugular 

\S~Z-  Subclavian 


Oblique  vein  of 


t  of  superior  vena  cai 
trophy  on  left  side 


1;  A,  primary  symmetrical  arrangement ;  ^.establishment 
md  persistence  on  right  side  of  superior  vena  cava. 


lower  portion  of  the  left  vein  degenerates  until  it  is  represented  only  by  the  small  oblique  vein  of 
the  left  auricle,  opening  into  the  coronary  sinus,  which  is  the  persisting  left  ductus  Cuvieri 
(Fig.  777.  C).  The  oblique  connecting  branch  becomes  the  left  innominate  vein  of  adult 
anatomy,  and  the  portion  of  the  left  anterior  cardinal  below  the  point  where  it  is  joined  by  the 
innominate,  together  with  the  right  ductus  Cuvieri,  becomes  the  superior  vena  cava. 

The  Inferior  Vena  Cava. — The  posterior  cardinals  persist  in  part  as  the  azygos  veins,  but 
their  history  is  so  intimately  associated  with  that  of  the  inferior  vena  cava  that  an  account  of  the 
development  of  the  latter  may  first  be  presented.  In  the  early  stages  of  development  the  only 
portion  of  the  inferior  vena  cava  which  exists  is  the  portion  which  intervenes  between  the  entrance 
of  the  hepatic  veins  and  the  right  auricle,  this  portion  representing  the  terminal  part  of  the  ductus 

Fig.  778. 


Posterior  cardinal 


Diagrams  illustrating  developmental  changes  leading  to  formation  of  inferior  cava]  and  azygos  veins. 

venosus  (page  705).  Branches  which  pass  to  the  posterior  cardinal  veins  from  the  mesentery 
anastomose  longitudinally  to  form  on  each  side  of  the  body  a  venous  stem  which  has  a  course 
parallel  to  that  of  the  cardinals,  with  which  it  unites  below  (Fig.  778,  A).  This  is  the  subcardinal 
vein,  the  two  vessels  of  opposite  sides  of  the  body  being  united  with  one  another  and  with  the 
cardinals  by  a  strong  cross-branch  which  joins  the  cardinals  opposite  the  point  of  entrance  into 


928 


HUMAN   ANATOMY. 


those  of  the  renal  veins.  The  portion  of  the  right  subcardinal  which  lies  anterior  to  the  cross- 
branch  then  enlarges  and  unites  with  the  existing  portion  of  the  inferior  vena  cava,  and  the  lower 
portion  of  the  right  cardinal,  together  with  the  portion  of  the  cross-branch  which  intervenes 
between  it  and  the  right  subcardinal,  also  enlarges,  and  these  three  elements  eventually  come 
into  line  with  one  another  and  with  the  terminal  portion  of  the  ductus  venosus  to  form  the 
inferior  vena  cava. 

The  lower  portions  of  both  subcardinals  now  degenerate,  and  the  upper  portion  of  the  left 
vein,  diminishing  in  size,  becomes  the  left  suprarenal  vein.  A  cross-branch  forms  between 
the  two  posterior  cardinals  at  the  level  of  the  common  iliac  veins,  and  the  lower  part  of  the  left 
cardinal  then  disappears  (Fig.  778,  C),  a  small  portion  below  the  original  renal  cross-branch 
alone  persisting  to  form  the  terminal  part  of  the  left  spermatic  (ovarian)  vein,  which  thus  comes 
to  open  into  the  left  renal  vein,  since  the  terminal  portion  of  that  vessel  represents  the  original 
renal  cross-branch.  As  a  result  of  this  degeneration  the  left  common  iliac  vein  comes  to  open 
into  the  lower  part  of  the  right  posterior  cardinal  by  way  of  the  iliac  cross-branch. 

The  Azygos  Veins. — While  these  changes  have  been  taking  place  the  anterior  portions  of 
the  posterior  cardinals  have  undergone  degeneration  immediately  anterior  to  the  renal  cross- 
branch  (Fig.  778),  so  that  they  form  independent  vessels,  receiving  the  intercostal  veins  and 
terminating  above  in  the  ductus  Cuvieri.     They  now  constitute  the  azygos  veins,  and,  on  the 

degeneration  of  the  lower  part  of  the  left 
Fig.  779.  anterior  cardinal,  the  left  azygos  develops 

connection  with  the  right  by  one  or  two 
transverse  branches  and  then  separates 
from  the  coronary  sinus,  the  adult  condi- 
tion of  the  hemiazygos  vein  being  thus 
acquired. 

The  Portal  Vein. — Passing  along  the 
umbilical  cord  to  the  body  of  the  embryo 
are  two  vitelline  or  omphalo-mesenteric 
veins,  which  have  their  origin  in  the  yolk- 
sac,  and  the  umbilical  vein,  which  brings 
back  the  blood  from  the  placenta.  When 
it  reaches  the  umbilicus,  the  umbilical 
vein  divides  into  two  stems  which  pass 
upward  upon  the  inner  surface  of  the 
anterior  abdominal  wall  and  unite  above 
with  the  corresponding  vitelline  veins  to 
open  into  the  ductus  Cuvieri.  The  vitel- 
line veins  pass  from  the  umbilicus  to  the 
intestine  and  ascend  along  it,  receiving 
tributaries  from  it ;  above,  they  traverse 
the  liver,  breaking  up  into  a  net-work  in  its 
substance,  and  are  then  continued  on  to 
unite  with  the  umbilicals  (Fig.  779,  A). 
By  the  enlargement  of  certain  portions  of 
the  hepatic  net-work  a  well-marked  venous 
stem  is  formed,  extending  from  the  point 
where  the  left  vitelline  vein  enters  the  liver 
to  the  junction  of  the  common  stem  formed 
by  the  right  vitelline  and  umbilical  veins 
with  the  duct  of  Cuvier.  This  new  stem  is 
the  ductus  venosus  (Figs.  779,  B  and  C), 
and  it  later  forms  a  connection  with  the  left  umbilical  vein  and  becomes  the  continuation 
of  that  vessel  as  the  result  of  the  degeneration  of  the  upper  part  of  the  umbilical  (D). 

In  the  meantime  three  cross-connections  have  developed  between  the  two  vitelline  veins 
(Fig.  779,  A,  B,  C),  two  of  them  passing  ventral  to  the  intestine  and  one  dorsal  to  it,  the 
intestine  thus  becoming  surrounded  by  two  venous  rings.  The  right  half  of  the  lower  ring 
and  the  left  half  of  the  upper  one  now  degenerate  (D),  and  the  persisting  portions,  which 
terminate  partly  in  the  hepatic  net-work  and  partly  in  the  ductus  venosus,  become  the  portal 
vein.  The  upper  portion  of  the  right  umbilical  vein  has  in  the  meantime  made  a  connection 
with  the  upper  ring  of  the  vitelline,  and  the  part  above  the  connection  then  degenerates,  the 
lower  part  becoming  much  reduced  in  size  and  persisting  as  a  small  parumbilical  vein  in  the 
anterior  abdominal  wall.  This  arrangement  persists  until  birth,  the  placental  blood  passing  by 
way  of  the  left  umbilical  vein  partly  to  the  ductus  venosus  and  thence  by  the  inferior  vena  cava  to 
the  heart  and  partly  through  the  hepatic  net-work  by  way  of  the  communication  between  the  left 
umbilical  and  vitelline  veins.    At  birth  the  placental  supply  of  blood  is  of  course  cut  off,  the  ductus 


*$Gh 


Diagrams  illustrating  transformations  of  vitelline  and 
umbilical  veins  during  development  of  liver-veins.  DC,  ducts 
of  Cuvier;  h,  heart;  ru,  lu,  right  and  left  umbilical  veins; 
rv,  Iv,  right  and  left  vitelline  veins ;  dv,  ductus  venosus ;  pv, 
portal  vein.     {Hochstetter.) 


THE    FGETAL   CIRCULATION.  929 

venosus  degenerates  to  a  solid  cord  up  to  the  point  where  the  hepatic  veins,  developed  from  the 
hepatic  net-work,  unite  with  it.  The  umbilical  vein  also  degenerates  to  form  the  round  ligament 
of  the  liver,  which  frequently  presents  more  or  less  distinct  evidences  of  its  original  lumen. 

The  Veins  of  the  Limbs. — The  details  of  the  development  of  the  limb  veins  are  not  as  yet 
thoroughly  known.  The  superficial  veins  are  the  first  to  form,  the  basilic  vein  of  the  arm  and 
the  long  saphenous  of  the  leg  being  the  primary  vessels  and  the  axillary  and  subclavian  and  the 
iliac  veins  their  respective  continuations.  The  remaining  superficial  veins  and  the  deep  veins 
are  later  formations. 

The  Pulmonary  Veins. — The  pulmonary  veins  make  their  exit  from  the  lungs  as  four 
vessels,  two  belonging  to  each  lung,  but  as  they  approach  the  heart  they  unite  first  in  pairs  and 
then  to  form  a  single  trunk  which  opens  into  the  right  auricle.  Later  a  considerable  portion  of 
the  original  veins  is  taken  up  into  the  wall  of  the  auricle,  the  absorption  eventually  extending 
beyond  the  point  of  the  union  of  the  original  veins  in  pairs,  so  that  in  the  adult  all  four  veins 
open  independently  into  the  auricle. 

THE  FCETAL  CIRCULATION. 

The  primary  or  vitelline  circulation  of  the  mammalian  embryo,  formed 
'  by  the  ramifications  of  the  vitelline  arteries  and  veins  over  the  yolk-sac  (umbilical 
vesicle),  must  be  regarded  as  an  inheritance  from  ancestors  in  whom  the  yolk 
provided  the  nutrition  for  the  developing  animal.  While  in  birds  and  reptiles 
the  vitelline  veins  are  important  channels  for  the  conveyance  of  the  nutritive 
materials  taken  up  from  the  yolk,  in  mammals  in  this  respect  they  are  of  little 
consequence,  thus  affording  an  example  of  structures  that,  although  no  longer 
useful,  recur  in  the  development.  The  vitelline  circulation  is  soon  followed  by  a 
second,  the  allantoic  circulation,  which  in  man  and  the  higher  mammals  provides 
the  vessels  connecting  the  fcetus  with  the  placenta — the  organ  whereby  respiration 
and  nutrition  are  secured  to  the  fcetus  during  the  greater  part  of  its  sojourn  within 
the  uterus. 

The  blood  is  carried  from  the  fcetus  to  the  placenta  by  the  hypogastric  arteries 
and  their  prolongations,  the  two  umbilical  arteries.  After  passing  through  the 
vascular  tufts  of  the  chorionic  villi  that  constitute  the  essential  structures  of  the  foetal 
part  of  the  placenta,  the  fcetal  blood,  renewed  in  oxygen  and  laden  with  nutritive 
material  derived  from  the  maternal  circulation,  is  carried  by  venous  tributaries  that 
unite  into  the  single  umbilical  vein.  The  latter  vessel  accompanies  the  umbilical 
arteries  within  the  umbilical  cord  as  far  as  the  umbilicus,  from  which  point  it  then 
passes  along  the  free  margin  of  the  crescentic  peritoneal  fold,  the  falciform  ligament, 
to  the  under  surface  of  the  liver  to  join  the  portal  vein  and  pour  its  stream  of  freshly 
oxygenated  blood  into  the  current  of  venous  blood  returned  from  the  digestive  tract 
to  the  liver.  For  a  short  time  the  rapidly  growing  liver  is  capable  of  transmitting 
all  the  blood  brought  to  it  by  the  vitelline  (later  portal)  and  the  umbilical  veins, 
and  this  blood  is  returned  to  the  heart  after  making  the  circuit  of  the  vessels  of  the 
liver.  Soon,  however,  the  latter  organ  can  no  longer  accommodate  the  entire 
volume  of  blood  conveyed  to  it  by  the  portal  and  umbilical  veins,  and  the  necessary 
relief  is  afforded  by  the  development  of  a  short  vessel,  the  ductus  venosus,  or 
ductus  Arantii,  that  extends  from  the  portal  vein  to  the  inferior  vena  cava  and 
thus  establishes  a  by-pass  for  the  greater  part  of  the  oxygenated  blood  returned 
from  the  placenta.  On  reaching  the  inferior  cava,  this  pure  blood  is  mingled  with 
the  venous  blood  being  returned  from  the  lower  half  of  the  body  and  the  abdominal 
viscera,  the  mixed  stream  so  formed  being  poured  into  the  right  auricle.  On  entering 
the  heart  the  current  is  directed  by  the  Eustachian  valve  towards  the  foramen 
ovale  in  the  auricular  septum  and  enters  the  left  auricle.  After  receiving  the 
meagre  additions  returned  by  the  pulmonary  veins  from  the  uninflated  lungs,  the 
blood  passes  through  the  left  auriculo-ventricular  opening  into  the  left  ventricle. 
Contraction  of  this  chamber  forces  the  blood  into  the  systemic  aorta  and  thence  to 
all  parts  of  the  body. 

After  traversing  the  vessels  of  the  head,  neck,  upper  extremities,  and  thorax, 
the  venous  blood  from  these  parts  is  returned  to  the  heart  by  the  superior  vena  cava, 
but  on  entering  the  right  auricle  does  not  mingle  to  any  extent  with  the  current 
returned  by  the  inferior  cava,  but  passes  through  the  auriculo-ventricular  orifice  into 
the  right  ventricle.      With  contraction  of  the  ventricles  the  blood  is  propelled  into 

59 


93° 


HUMAN   ANATOMY. 


the  pulmonary  artery  and  towards  the  lungs.  Being  uninflated  these  organs  can 
appropriate  only  a  small  part  of  the  entire  volume  of  blood  brought  by  the  pulmonary 
artery,  hence  the  necessity  of  a  second  by-pass,  the  ductus  arteriosus,  or  ductus 
Botalli,  that  extends  from  the  beginning  of  the  left  pulmonary  artery  to  the 
adjacent  aorta  and  represents  the  still  pervious  distal  portion  of  the  last  aortic  arch 

on  the  left  side  (page  847).      By  means 
Fig.  7S0.  0f  tne  ductus  arteriosus,  the  venous  blood 

returned  from  the  head  and  upper 
extremities  is  poured  into  the  great 
descending  trunk,  the  aorta,  and  carried 
to  the  abdominal  viscera  and  the  lower 
extremities.  On  reaching  the  bifurcation 
of  the  common  iliac  arteries,  the  blood- 
stream divides,  that  part  going  into  the 
internal  iliacs  being  of  much  greater 
importance,  so  far  as  the  general  nutri- 
tion of  the  fcetus  is  concerned,  since  it 
is  carried  by  the  continuations  of  these 
vessels — the  hypogastrics  and  umbilical 
arteries — to  the  placenta,  to  be  once  more 
purified  and  again  returned  to  the  fcetus 
by  the  umbilical  vein. 

From  the  foregoing  sketch  of  the 
foetal  circulation  it  is  evident  that,  with 
the  exception  of  the  umbilical  vein,  no 
vessel  within  the  fcetus  conveys  strictly 
arterial  or  fully  oxygenated  blood,  since 
on  entering  the  inferior  cava  the  pure 
blood  is  mixed  with  the  venous  returning 
from  the  lower  half  of  the  body.  It  is 
further  evident  that  the  blood  distributed 
to  the  head  and  upper  extremities  is  less 
contaminated  than  that  passing  to  the 
lower  half  of  the  body  from  branches  of 
the  aorta  given  off  after  junction  with 
the  venous  stream  conveyed  by  the 
ductus  arteriosus.  It  may  be  borne  in 
mind  that  the  umbilical  vein  and  the 
ductus  venosus  carry  arterial  blood  and 
the  pulmonary  artery  and  the  ductus 
arteriosus  purely  venous  blood,  the  aorta 
distributing  mixed.  Upon  the  assumption 
of  the  respiratory  function  at  birth,  the 
three  anatomical  structures  peculiar  to 
the  fcetal  circulation — the  ductus  venosus, 
the  foramen  ovale,  and  the  ductus  arteri- 
osus— become  useless  and  so'on  undergo 
occlusion  and  atrophy,  the  two  former 
ducts  being  represented  by  the  fibrous  cords  seen  on  the  posterior  surface  of  the  liver 
and  terminal  part  of  the  aortic  arch  respectively.  Closure  of  the  foramen  ovale 
proceeds  more  slowly,  a  week  or  more  being  usually  consumed  in  effecting 
obliteration  of  the  opening  ;  indeed,  in  a  large  proportion  of  individuals  complete 
closure  never  occurs  (page  695). 


Diagram  of  foetal  circulation  shortly  before  birth : 
courseof  blood  is  indicated  byarrows.  P, placenta;  UA, 
UV,  umbilical  arteries  and  vein  ;  U,  umbilicus  ;  DV, 
ductus  venosus  ;  1VC,  inferior  vena  cava  ;  PV,  portal 
vein;  HV,  hepatic  veins;  RV,  LV.  right  and  left 
ventricle;  PA,  pulmonary  artery;  DA,  ductus  arteri- 
osus ;  SVC.  superior  vena  cava  ;  AA,  abdominal  aorta ; 
HA,  hypogastric  arteries  (internal  iliac);  EIA,  ex- 
ternal iliac  arteries ;  I,  intestine;  L,  lungs;  K,  kidney. 


THE   LYMPHATIC  SYSTEM. 

The  lymphatic  system  is  a  system  of  vessels  which  occur  abundantly  in  almost 
all  portions  of  the  body  and  converge  and  anastomose  to  form  two  or  more  main 
trunks,  which  open  into  the  subclavian  veins  just  before  they  are  joined  by  the 
internal  jugular.  The  vessels  contain  a  fluid  termed  lymph,  usually  colorless,  and 
containing  numerous  corpuscles  known  as  lymphocytes.  Since  the  latter  usually 
come  under  observation  as  they  circulate  within  the  blood-vessels,  the  detailed 
account  of  the  lymphocytes  is  given  in  connection  with  blood-corpuscles  (page  684). 
In  those  vessels  which  have  their  origin  in  the  wall  of  the  small  intestine, 
however,  the  contained  fluid  has,  especially  during  digestion,  a  more  or  less  milky 
appearance,  owing  to  the  lymphocytes  being  loaded  with  particles  of  fat  which  they 
have  taken  up  from  the  intestinal  contents.  On  this  account,  these  vessels  are 
usually  spoken  of  as  lacteals,  although  it  must  be  recognized  that  they  are  merely 
portions  of  the  general  lymphatic  system. 

In  certain  respects  the  vessels  of  the  system  strongly  resemble  the  veins,  closely 
associated  with  which  they  take  their  origin  embryologically  and  into  which  they 
finally  pour  their  contents  in  the  adult.  They  arise  from  a  capillary  net-work,  their 
walls  have  a  structure  closely  resembling  that  of  the  veins,  they  are  abundantly 
supplied  with  valves,  and  it  may  be  said  that  the  fluid  which  they  contain  flows  from 
the  tissues  towards  the  heart.  With  these  similarities  there  are  combined,  however, 
marked  differences.  One  of  the  most  important  of  these  consists  in  the  fact  that 
the  capillaries  are  closed  and  do  not  communicate  with  any  centrifugal  set  of  vessels, 
as  the  venous  capillaries  do  with  the  arterial  ;  and  another  important  difference  is 
to  be  found  in  the  frequent  occurrence  upon  the  lymphatic  vessels  of  character- 
istic enlargements,  the  lymphatic  nodes  or  so-called  glands  (lymphoglandulae),  quite 
different  from  anything  occurring  in  connection  with  the  veins. 

Lymph-Spaces. — Throughout  practically  all  regions  of  the  body  spaces  of 
varying  size,  occupied  by  a  clear,  more  or  less  watery  fluid,  exist,  and  to  these 
the  term  lymph-spaces  has  been  applied  (Fig.  781).  It  was  long  believed  that 
they  were  directly  continuous  with  the  lymphatic  capillaries,  that  the  latter,  indeed, 
opened  out  from  them,  the  spaces  forming  the  origins  of  the  capillaries.  There  is, 
however,  a  growing  tendency  to  dispute  this  view  and  to  regard  the  lymphatic 
capillaries  as  being  quite  independent  of  the  spaces, — the  entire  lymphatic  system, 
in  fact,  being  a  closed  system,  except  for  its  communications  with  the  subclavian 
veins.  Since,  however,  the  lymphatic  capillaries  form  net-works  in  the  tissues 
which  bound  these  spaces,  interchange  of  their  contents  with  those  of  the  capillaries 
is  by  no  means  difficult,  the  lymphocytes,  even,  passing  on  occasion  through  the 
walls  of  the  capillaries  into  the  spaces  and  returning  again  to  the  interior  of  the 
capillaries. 

If  a  colored  fluid  be  injected  into'the  portal  vein  it  will  pass  through  the  walls  of 
the  venous  capillaries  and  invade  the  spaces  of  the  interlobular  hepatic  connective 
tissue,  and  later  it  will  flow  away  by  the  hepatic  lymph-capillaries.  By  varying  the 
extent  of  the  injection  it  will  be  found  that  the  lymphatic  vessels  will  be  injected  when 
the  lymph-spaces  are  completely  filled,  but  will  not  be  when  the  spaces  are  only 
partially  injected  (Mall),  so  that  it  may  be  concluded  that  the  extravasation  from  the 
portal  capillaries  is  primarily  into  the  hepatic  lymph-spaces  and  thence  makes  its  way 
into  the  lymph-capillaries. 

The  spaces  vary  greatly  in  size,  existing  in  certain  tissues  even  between  the 
individual  cells.  They  are  more  evident,  however,  in  the  connective  tissues,  reaching 
a  considerable  size  in  areolar  tissue,  where  they  form  a  continuous  net-work,  and, 
since  the  blood-vessels  are  usually  surrounded  by  a  greater  or  less  amount  of  con- 
nective tissue,  lymph-spaces  are  quite  distinct  along  their  courses,  forming  what  are 
known  as  the  perivascula?'  lymph-spaces  (Fig.  782).  In  other  regions  of  the  body 
somewhat  extensive  spaces  occur  which  have  been  regarded  as  belonging  to  the 

931 


932 


HUMAN   ANATOMY. 


category  of  lymph-spaces,  and  among  these  there  may  be  mentioned  the  subarachnoid 
and  subdural  spaces   of  the  meninges,  Tenon's   space  in   the  orbit,   and  even  the 

Fig.  7S1. 


%,  ^Valv 


<■[" -Lymph-vessel 


Deeply  stained 
ground  substance 


m:^x3 


Portion  of  centra]  tendon  of  rabbit's  diaphragm,  treaLed  with  silver  nitrate;  lymphatic  vessels  are  show 
irregular  tracts  ;  lymph-spaces  are  seen  within  stained  ground  substance.     X  120. 


light 


Fig 


spaces    occupied  by  the  aqueous  and  vitreous  humors  of  the  eye,   as  well  as  the 
smaller  spaces  of  that  organ.      So,  too,  the  spaces  surrounding  that  enclosed  by  the 

membranous  labyrinth  of 
the  ear  have  been  regarded 
as  lymph-spaces,  as  is 
indicated  by  their  names. 
Finally,  it  may  be 
mentioned  that  the  syn- 
ovial cavities  of  the  artic- 
ulations and  the  greater 
serous  cavities  of  the  body 
enclosed  by  the  pleura, 
pericardium,  and  perito- 
neum have  been  regarded 
as  being  in  direct  com- 
munication with  the  lym- 
phatic'capillaries;  but  this 
view  is  also  in  all  proba- 
bility erroneous. 

Notwithstanding  the 
independence  of  these 
spaces  from  the  lymphatic 
capillaries,  it  must  be 
recognized  that  some  of 
them  at  least  play  im- 
portant roles  from  the 
physiological  standpoint, 
in  serving  as  middle-men  between  the  tissues  and  the  lymphatics,  and,  furthermore, 
those  of  the  eyeball,  by  their  communication  with  neighboring  spaces,  permit  of  a 


Perivascular  lymph-spaces  sur 


al  blood-vessels.    X  230. 


THE    LYMPHATIC    SYSTEM. 


933 


nnective-tissue  layer  of  skin;  smaller 
al  net-work,  larger  to  deeper.     (  Teichmann.*) 


rapid  compensation  for  variations  in  the  intraocular  tension.      From  the  anatomical 

standpoint,  however,  they  are  not  to  be  regarded  as  actually  parts  of  the  lymphatic 

system,  and  the  mention  that  they  here  receive  is  merely  a  tribute  to  their  historical 

importance  in  the  problem  of  the  origin  of  the  lymphatic  capillaries. 

The  Capillaries. — The  lymphatic  capillaries  (Fig.  783),  which  are  arranged 

in  the  form  of  net-works  of  very  different  degrees  of  fineness  and  complexity,  closely 

resemble  in  structure  the 

blood  -  capillaries,     their  FIG-  7S3- 

walls     consisting     of     a 

single  layer  of  endothelial 

plates,   which,   however, 

are    usually    larger    and 

less    regularly    disposed 

than    those    lining     the 

blood  -  channels.      They 

differ  from  those  of  the 

blood  -  vascular     system 

not  only  in  their  ultimate 

branches   being    closed, 

but  also  in  their  general 

appearance.     Thus,  they 

are     of     much     greater 

calibre,    their     diameter 

varying  from  .030-.  060 

mm.,  while  that  of   the 

blood-capillaries  may  be 

as    little   as   .008    mm.  ; 

they  do  not  present  the  regularity  of  size   and  gradual  increase  or   diminution  of 

calibre  noticeable  in  the  blood-capillaries,  but  larger  and  smaller  stems  are  indefinitely 

interspersed,  and  spindle-shaped  or 
Fir,.    7S4.  nodular  enlargements  may  occur  at 

irregular  intervals  throughout  the 
net-work.  And,  finally,  as  a  result 
of  these  peculiarities,  the  meshes  of 
the  net-work  are  of  very  varying  size 
and  form. 

The  arrangement  assumed  by 
a  net-work  depends  largely  upon 
the  tissue  and  organ  in  which  it 
occurs.  In  the  integument,  for  in- 
stance, the  lymph- capillaries  arrange 
themselves  in  two  more  or  less 
distinct  layers,  a  more  superficial 
one,  composed  of  smaller  capillaries, 
and  a  deeper,  coarser  one, — numer- 
ous communications  necessarily 
existing  between  the  two.  Both  net- 
works are  confined  to  the  dermis, 
the  more  superficial  one  lying  close 
to  its  epidermal  surface,  while  the 
deeper  one  is  situated  in  its  deeper 
layers,  the  distance  between  the  two 
varying  according  to  the  develop- 
ment of  the  dermis  in  different 
portions  of  the  body  and  in  different 

individuals.     From  the  superficial  layer  loops  or  single  capillaries  project  upward  into 

the  dermal  papillse,  and  special  portions  of  the  net-work  surround  each  hair-follicle  and 

sudoriparous  gland. 

*  Das  Saugadersystem.     Leipzig,  1861. 


Transverse  section  ot  small  lymph-vessel.    X  : 


934 


HUMAN   ANATOMY. 


Fig.  7S5. 


The  mucous  membranes  have  essentially  the  same  arrangement,  the  net-work  with- 
in the  small  intestine,  for  instance,  being  arranged  in  two  more  or  less  distinct  layers,  one 
of  which  lies  in  the  submucosa  and  sends  loops  or  blindly  ending  processes  into  the  villi, 
while  the  other  is  situated  in  the  muscular  coat.  What  may  be  regarded  as  a  third  net- 
work, lying  beneath  the  serous  or  connective-tissue  investment,  is  formed  by  the  anas- 
tomosis of  the  stems  arising  from  the  deeper  net-works  and  it  is  from  this  last  net-work 
that  the  efferent  stems  arise.  In  most  other  organs  lined  by  mucous  membrane  a 
similar  arrangement  occurs,  although  in  the  uterus,  bladder,  and  ureters  the  submucous 
.net-work  seems  to  be  wanting,  the  muscular  set  alone  being  demonstrable.  Through- 
out the  serous  membranes  the  net-works  possess  naturally  a  layered  arrangement,  but 
in  the  more  massive  organs,  such  as  the  liver  and  pancreas,  they  are  arranged  with 
reference  to  the  constituent  lobules,  each  being  invested  by  an  interlobular  net-work. 
Considerable  variation  exists  in  the  closeness  of  the  net-work  in  different  organs, 
and,  indeed,  in  different  parts  of  the  same  organ,  but  everywhere  the  lymph- 
capillaries  are  exceedingly  thin-walled  and  possess  no  valves.  As  has  been  pointed 
out,  the  view  formerly  prevailed  that  the  capillaries  communicated  directly  with  the 
great  serous  cavities  of  the  body,  with  the  spaces  of  the  connective  tissues,  and  even 
w-ith  the  pericellular  spaces  which  occur  in  the  more  compact  tissues,  all  these  being 
regarded  as  radicles  of  the  lymphatic  vessels.  It  is  now  believed,  however,  that 
Isuch  is  not  the  case,  but  that  the  net-works,  which  are  everywhere  continuous,  are 
completely  closed  except  for  their  communications  with  the  efferent  vessels. 

The  Lymph-Vessels. — The  lymph-vessels, 
which  issue  from  the  capillary  net-works  and  convey 
the  lymph  ultimately  to  the  subclavian  veins,  have 
an  arrangement  closely  resembling  that  of  the  veins, 
and,  indeed,  the  larger  ones  are  usually  situated 
alongside  and  accompany  the  course  of  blood-vessels. 
Just  as  it  is  possible  over  the  surface  of  the  body  and 
limbs  to  distinguish  between  superficial  and  deep 
veins,  so  there  can  be  recognized  a  sitfie?-Jicial  set 
of  lymphatic  vessels  (vasa  lymphatica  superficialia), 
situated  superficially  to  the  fascia  which  encloses  the 
musculature,  and  a  deep  set  (vasa  lymphatica  profunda), 
the  vessels  of  which  lie  beneath  the  fascia  ;  numerous 
communications,  however,  exist  between  the  two  sets. 
Just  as  the  veins  unite  to  form  larger  trunks 
as  they  pass  from  the  capillaries  toward  their  termi- 
nation, so,  too,  the  lymphatics  ;  but  the  latter 
present  two  peculiarities  which  distinguish  them 
from  the  veins.  They  do  not  anastomose  as  abun- 
dantly as  the  latter  and  there  is  not  the  same 
proportional  increase  in  the  size  of  a  lymphatic 
vessel  formed  by  the  junction  of  others  as  in  the 
veins,  so  that,  while  the  lymphatics  at  their  origin 
from  the  capillary  net-works  may  have  the  same 
calibre  as  the  corresponding  veins,  yet  their  terminal 
trunks  are  of  much  smaller  diameter. 

As  a  rule,  several  lymphatic  vessels  arise  from 
the  capillary  net-work  of  any  organ  or  region  of  the 
body,  and,  since  the  net- work  is  to  be  regarded  as 
practically  continuous  over  large  areas,  it  would 
appear  that  the  flow  of  lymph  from  any  circumscribed 
area  might  take  place  through  widely  separated 
stems  and  be  carried  along  very  different  paths. 
And  such,  to  a  certain  extent,  is  the  case  ;  but  it 
has  been  found  by  experiment  and  by  the  observation 
of  pathological  conditions  that  for  each  organ  or  region  there  is  a  more  or  less  definite 
lymphatic  path,  each  vessel  or  group  of  vessels  tending  to  drain  a  somewhat  definite 
area  of  the  net-work,  a  fact  of  considerable  importance  from  the  diagnostic  standpoint. 


Shaded  part  of  figure  shows  area 
drained  by  right  lymphatic  duct;  lym- 
phatics of  remaining  territory  received 
by  thoracic  duct. 


THE    LYMPHATIC    SYSTEM. 


935 


All  the  lymphatic  vessels  terminate  directly  or  indirectly  in  one  of  two  main 
trunks,  which,  as  already  stated,  open  respectively  into  the  right  and  left  subclavian 
veins.  The  left  trunk,  the  thoracic  duct  (ductus  thoracicus),  is  much  larger  than 
the  right,  beginning  in  the  abdominal  region  and  traversing  the  entire  length  of  the 
thorax  to  reach  its  destination.  It  receives  all  the  lymph  returned  from  the  lower 
limbs,  the  pelvic  walls  and  viscera,  the  abdominal  walls  and  viscera,  the  lower  part  of 
the  right  half  and  the  whole  of  the  left  half  of  the  thoracic  wall,  the  left  half  of  the 
thoracic  viscera,  the  left  side  of  the  neck  and  head,  and  the  left  arm.  The  other 
trunk,  the  right  lymphatic  duct  (ductus  lymphaticus  dexter),  is  very  short,  and, 
indeed,  is  frequently  wanting,  the  vessels  which  typically  unite  to  form  it  opening 
independently  into  the  vein.  It  receives  the  lymph  from  the  upper  part  of  the  right 
side  of  the  thoracic  wall,  from  the  right  half  of  the  thoracic  viscera  and  the  upper  surface 
of  the  liver,  the  right  side  of  the  neck  and  head,  and  from  the  right  arm  (Fig.  785). 

In  structure  the  larger  lymphatic  vessels  are  similar  to  the  veins,  but,  as  a  rule, 
their  walls  are  thinner  than  those  of  veins  of  corresponding  calibre  and  their  valves 
are  more  numerous.  The  walls  of  the  most  robust  trunks,  particularly  those  of  the 
thoracic  duct,  consist  of  three  coats.  From  within  outward  these  are  :  (<z)  the 
intima,  composed  of  the  endothelial  lining  and  the  fibro-elastic  subendothelial  layer  ; 
(&)  the  media,  made  up  of  involuntary  muscle  interspersed  with  fibro-elastic  tissue  ; 
and  (c)  the  adventitia,  consisting  of  fibro-elastic  tissue  and,  frequently,  of  longitudinal 
bundles  of  involuntary  muscle.      (Fig.  784.) 

The  Lymphatic  Nodes. — Scattered  along  the  course  of  the  lymphatic  vessels 
are  to  be  found  in  various  regions  of  the  body  elliptical  flattened  nodules  (Fig.  796) 
of  varying  size,  some- 
times singly  but  more  Fig.  786. 
frequently  in  chains  or 
groups  ( plexus  lym- 
phatici)  of  from  three 
to  six  or  even  ten  to 
fifteen.  These  are  the 
lymphatic  nodes  (lym- 
phoglandulae).  As  it 
approaches  a  node,  a 
lymph  -  vessel  divides 
into  a  number  of  stems, 
the  vasa  afferentia, 
which  enter  the  sub- 
stance of  the  node  and 
communicate  with  a 
capillary  net-work  in 
its  interior,  from  which 
a  somewhat  smaller 
number  of  vessels,  the 
vasa  efferentia,  arise 
(Fig.  786).  These, 
leaving  the  node,  the 
surface  of  which  fre- 
quently presents  a 
slight  depression,  the 
hilum,  at  their  point  of  emergence,  unite  to  form  the  continuation  of  the  vessel. 
The  lymph  conveyed  by  any  of  the  vessels  traverses  one  or  more  nodes  before 
emptying  into  the  thoracic  or  right  lymphatic  duct,  and  in  those  cases  in  which 
a  plexus  occurs  in  a  lymph-path  a  number  of  nodes  must  be  traversed.  The 
passage  through  the  intranodular  net-work  produces  a  greater  or  less  retardation  of 
the  flow  of  the  fluid  and  affords  opportunity  for  the  accumulation  of  lymphocytes. 
Moreover,  since  these  possess  a  phagocytic  function,  in  cases  of  infection  of  any 
part  of  the  body  the  nodes  along  the  lymph-paths  leading  from  it  become  more 
or  less  engorged  with  lymphocytes  and  enlarged,  and  in  case  the  lymphocytes  are 
unable  to  contend  successfully  with  the  infective  material,  the  nodes  may  serve  as 


Cortical  follicle 


ustrating  architecture  of  lymph-node. 


936 


HUMAN   ANATOMY. 


foci  for  its  distribution  to  other  parts  of  the  system.  The  nodes  therefore,  serving 
as  traps  for  the  infective  material,  possess  a  high  degree  of  importance  from  the 
surgical  standpoint,  an  accurate  knowledge  of  their  location  and  of  the  lymph-paths 
along  which  each  group  is  situated  being  of  great  value. 

In  addition  to  the  ordinary  lymph-nodes  there  occur  in  various  regions  of  the 
body,  especially  in  the  prevertebral  regions  of  the  abdomen,  structures  which 
resemble  lymph-nodes  in  their  form  and  size,  but  differ  from  them  in  color.  In 
general  the  lymph-nodes  are  of  a  pale  pinkish  color,  although  those  in  the  vicinity 
of  the  lungs  are  usually  blackish,  from  the  deposition  in  them  of  dust  particles  from 
the  lungs,  and  those  in  connection  with  the  vessels  arising  from  the  small  intestine  are 
milky  white  during  digestion.  The  structures  in  question,  however,  are  of  a  deep 
red  color,  owing  to  the  presence  of  abundant  blood-vessels  in  their  cortical  portion. 
These  bodies  have  been  termed  the  hemolymph  nodes,  but  their  exact  nature  and 
function  have  not  yet  been  definitely  ascertained.  By  some  they  are  regarded  as 
special  structures,  quite  different  from  the  lymph-nodes,  perhaps  partaking  somewhat 
of  the  character  of  the  spleen  ;  while  others  regard  them  as  ordinary  lymph-nodes 
with  an  especially  rich  blood  supply,  transitional  forms  between  them  and  the  usual 
lymph-nodes  being  believed  to  exist.  Whether  or  not  direct  communication  exists 
between  the  cortical  blood-vessels  and  the  medullary  lymphatics  within  these 
hemolymph  nodes  is  also  a  question  concerning  which  differences  of  opinion  exist. 
Structure  of  Lymphoid  Tissue. — Wherever  found,  whether  as  diffuse  masses, 
simple  nodules,  or  as  the  larger  and  more  complex  lymph-nodes,  lymphoid  or  adenoid 

tissue  is  composed  of  two  chief  con- 
Fig.  7S7.  stituents,   the  supporting   reticulum 

and  the  lymphoid  cells  contained 
within  the  meshes  of  the  framework. 
The  reticulum  varies  in  the  thickness 
of  the  component  fibres  and  the  size 
of  its  meshes,  but  in  the  denser  types 
of  lymphoid  tissue,  as  seen  in  the 
periphery  of  the  solitary  nodules  and 
in  the  cortical  follicles  and  medullary 
cords  of  the  lymph-nodes,  it  is  so 
masked  by  the  innumerable  over- 
lying cells  that  only  after  removal 
of  the  latter  can  the  supporting 
framework  be  satisfactorily  demon- 
strated. The  reticulum,  the  nature 
of  which  is  still  a  subject  of  discus- 
sion, may  be  regarded  as  modified 
fibrous  connective  tissue,  upon  the 
trabecuke  of  which,  particularly  at 
the  points  of  junction,  flattened  con- 
nective tissue  cells  are  closely  applied 
as  a  more  or  less  complete  invest- 
ment. In  certain  localities  where  of 
exceptional  delicacy,  the  reticulum 
may  be  formed  almost  entirely  by 
the  anastomosing  processes  of  stellate 
connective-tissue  elements. 
The  cells  composing  lymphoid  tissue,  exceedingly  numerous  and  closely  packed, 
present  the  general  characteristics  that  distinguish  the  lymphocytes,  being  small 
elements  with  comparatively  large  nuclei,  which  exhibit  a  strong  .affinity  for  nuclear 
(basic)  stains. 

The  simple  lymph-nodules,  of  varying  size  but  seldom  more  than  2  mm.  in 
diameter,  are  irregularly  spherical  or  elliptical  masses  of  lymphoid  tissue  in  which  a 
denser  peripheral  zone  encloses  and  blends  with  a  core  of  less  compact  texture. 
Within  the  looser  and  therefore  lighter  central  area,  lymphoid  cells  in  various  stages 
of  mitotic  division  are  frequently  seen,  such  foci,  known  as  germ-centres,  indicating 


'Submucous 
layer 


Simple  lymph-nodule  from  large  intestine.     X  i 


THE   LYMPHATIC   SYSTEM. 


937 


Fig.  7S8. 


the  birthplaces  of  new  lymphocytes.  Although  the  limits  of  the  lymph-nodules  are 
commonly  imperfectly  defined  by  a  condensation  of  the  surrounding  connective 
tissue,  a  distinct  capsule  is  usually  wanting. 
Definite  lymph-channels  are  found  neither 
upon  the  surface  nor  within  the  simple 
nodules  ;  the  latter  are  provided,  however, 
with  a  generous  net-work  of  capillary 
blood-vessels  (Fig.  792). 

Intermediate  in  their  complexity  of 
arrangement,  between  the  simple  nodules 
on  the  one  hand  and  the  typical  lymph- 
nodes  on  the  other,  stand  such  structures 
as  Peyer's  patches  and  the  faucial  and 
pharyngeal  tonsils,  in  which  groups  of 
simple  nodules  are  blended  into  a  single 
organ,  the  component  follicles  only  partly 
retaining  their  individuality. 

The  lymph-nodes  interposed  along 
the  lymphatic  vessels,  usually  embedded 
within  fatty  tissue,  represent  still  higher 
differentiation  as  distinct  organs.  In  form 
and  size  they  vary  from  minute  bodies 
resembling  millet-seeds  to  flattened  oval  or 
bean-shaped  organs,  that  may  measure  almost  an  inch  in  their  longest  diameter. 
They  are  invested  by  a  distinct  fibrous  capsule,  in  which  elastic  fibres  constantly  and 
unstriped  muscle  occasionally  are  present.  From  the  deeper  surface  of  this  envelope 
numerous  radially  directed  trabecular  penetrate  the  outer  zone,  or  cortex,  which  is 
thus  subdivided  into  a  series  of  pyramidal  compartments.  On  reaching  the  inner 
limits  of  the  cortical  zone,  the  trabecular  are  less  regularly  disposed  and  more  freely 
united,  thereby  breaking  up  the  deeper  parts,  or  medulla,  of  the  node  into  uncertain 
cylindrical  compartments.      The  spaces  thus  imperfectly  defined  by  the  trabecular  are 


ot  lymph-nodule,  showing  details 
of  germ-centre.     X  350. 


Germ-centre 
Lymph-sinus  _\j. 


Fig.  7S9. 

Lymph-sinus 


Cortical  follicles 


Hilum 

of  small  lymph-] 


Vasa  efferentia 
3de  through  hilum. 


Mudiillarv  cords 


incompletely  filled  by  masses  of  compact  lymphoid  tissue,  the  general  form  and 
arrangement  of  which  correspond  to  the  compartments  in  which  they  lie.  The  masses 
contained   within   the   peripheral   spaces   are   spherical   or   pyriform  and   constitute 


93S 


HUMAN   ANATOMY. 


Cortical  follicle 


the  cortical  nodules ;  those  within  the  communicating  central  compartments  form  a 
net-work  of  irregular  cylinders,  the  medullary  cords,  which  are  continuous  with  one 

another  and  with  the  deeper 
part  of  the  cortical  nodules 
(Fig.  789). 

The  intervals  between 
the  tracts  of  lymphoid 
tissue  and  the  trabecular 
frame-work  constitute  a 
system  of  freely  intercom- 
municating channels,  the 
lymph  -  sinuses,  through 
which  passes  the  lymph 
brought  to  the  node  by  the 
afferent  lymphatic  vessels. 
The  latter  pierce  the  capsule 
on  the  convex  surface  of 
the  node  and  empty  into 
the  sinuses  that  surround 
the  outer  and  lateral  surfaces 
of  the  cortical  nodules. 
After  traversing  the  periph- 
eral sinuses,  the  lymph 
~%    '        -  passes    into    the    irregular 

':.y*  '''-.<:':'   ;0.     '"'  channels    of    the    medulla 

■■'  '%W  and   towards  the   point  at 

/§--:,?:  which  the  efferent  lymph- 

vessels    leave   the    nodule. 

relation  between  trabecula,  The  position   of    this  exit  is 

usually  indicated  by  a  more 
known  as  the  hilum,   on  the  surface  of  the  node 


or  less  pronounced  indentation, 
opposite  the  entrance  of  the 
afferent  lymph-vessels. 

The  lymph-sinuses,  there- 
fore, are  bounded  on  one  side 
by  the  capsule  or  the  trabecula? 
and  on  the  other  by  the  masses 
of  dense  lymphoid  tissue.  The 
lumen  of  these  channels,  however, 
is  not  free,  but  occupied  by  a 
delicate  wide-meshed  reticulum 
consisting  of  fine  strands  of 
connective  tissue  where  most 
marked,  or  of  the  processes  of 
stellate  cells  where  very  delicate 
(Ebner).  The  sinuses  are  lined 
by  an  imperfect  layer  of  flattened 
plate-like  cells,  that  represent 
the  endothelium  of  the  adjoining 
lymphatic  vessels  and  also  cover 
the  more  robust  trabecular  cross- 
ing the  channels.  The  reticulum 
occupying  the  sinuses  is  continu- 
ous with  the  closer  and  more 
delicate  net-work  within  the  adja- 
cent dense  lymphoid  tissue. 
Although  both  the  afferent  and 
efferent  lymphatics  are  provided 
with  valves,  the  lymph-channels 


Fig 


of  medulla  of  lymph-node,  showing  details  of  lymph-sinus 
and  medullary  cords.     X  250. 


THE    LYMPHATIC    SYSTEM. 


939 


within  the  node  are  destitute  of  such  folds.  The  passage  of  the  lymph  through  the 
nodes  is  retarded  by  the  reticulum  within  the  sinuses,  thus  favoring  the  entrance  of 
the  young  lymphocytes  from  the  surrounding  lymphoid  tissue  into  the  sluggishly 
circulating  fluid.  Germ-centres,  the  particular  foci  for  the  production  of  the  lympho- 
cytes, usually  are  present  within  the  cortical  nodules,  but  are  not  found  within 
medullary  cords. 

The  blood-vessels  for  the  nutrition  of  the  lymph-nodes  are  numerous.  Entering 
at  the  hilum ,  they  divide  into  arterioles  which  follow  the  trabecular,  giving  off  smaller 
branches    that    pene- 

Fig.  792. 


sS^aS^ssp^ 


all  lymph-node,  injected  to  show- 
supply.     X  10. 


trate  the  medullary 
cords  and  the  cortical 
nodules  and  break  up 
into  rich  capillary  net- 
works for  the  supply 
of  the  denser  lym- 
phoid tissue. 

Both  medullated 
and  non-medullated 
nerves  enter  the 
node  at  the  hilum  in 
company  with  the 
blood-vessels.  They 
are  chiefly  sympa- 
thetic fibres  destined 
for  the  involuntary 
muscle  of  the  vessels 
and  of  the  capsule. 
The  distribution  of  the 
medullated    fibres    is 

uncertain.      According  to  Tonkoff,  fibrillar  are  traceable  into  the  lymphatic  tissue  of 
the  medulla. 

Development. — The  origin  of  the  first  lymph-cells,  the  lymphocytes,  is  uncer- 
tain, these  elements  appearing  outside  the  vessels  as  derivatives  from  the  mesoblast 
(page  688).  After  the  establishment  of  the  lymphoid  tissue  new  cells  are  continually 
being  formed  within  the  various  lymph-nodes  and  nodules. 

The  development  of  the  lymphatic  vessels  has  generally  been  believed  to 
proceed  from  the  veins  by  a  process  of  budding  (Ranvier),  similar  to  that  followed 
in  the  extension  of  the  blood-vessels;  and  certain  recent  investigators, — Sabin,1 
who  studied  the  development  of  the  lymphatics  in  pig  embryos,  and  F.  T.  Lewis,2 
who  worked  with  rabbit  embryos, — while  differing  as  to  details  of  the  development 
of  the  definitive  lymphatic  steins,  agree  as  regards  their  origin  in  this  manner. 

Sabin,  by  employing  a  method  of  injection,  found  that  the  first  traces  of  a 
lymphatic  system  appear  in  pig  embryos,  14.5  mm.  in  length,  as  two  small  out- 
growths, which  develop,  one  on  each  side,  at  the  junction  of  the  subclavian  and 
jugular  veins  ;  from  these,  by  a  process  of  endothelial  budding,  vessels  gradually 
grow  towards  the  skin,  radiating  and  anastomosing  in  all  directions  to  form  a 
subcutaneous  net-work,  which  gradually  extends  throughout  the  anterior  half  of  the 
body.  Later  two  additional  outgrowths  develop  at  the  junction  of  the  femoral  and 
post-cardinal  veins,  and  give  rise  to  a  subcutaneous  net-work  throughout  the  posterior 
half  of  the  body,  the  two  sets  of  net-works  thus  formed  eventually  uniting. 

Lewis's  studies  of  serial  sections  of  rabbit  embryos  gave  somewhat  different 
results  and  indicated  that  Sabin' s  method  of  study  did  not  suffice  to  reveal  the  actual 
origin  of  the  lymphatics.  He  found  the  first  of  these  vessels  along  the  course  of  the 
internal  jugular  vein  as  a  series  of  spaces,  each  of  which  he  supposed  to  represent  an 
independent  outgrowth  from  the  vein.  These  spaces  eventually  fused  to  form  a 
single  lymph-channel  accompanying  each  vein,  and  other  channels  were  found  to 
arise  in  a  similar  manner  in  connection  with  the  subcardinal,  mesenteric,  and  azygos 

1  Amer.  Jour,  of  Anatomy,  vol.  i.,  1902. 

2  Amer.  Jour,  of  Anatomy,  vol.  v.,  1905. 


94Q 


HUMAN   ANATOMY. 


veins.  The  various  channels  finally  unite  to  form  a  continuous  system  which  acquires 
new  openings  with  the  venous  system  near  the  termination  of  the  subclavian  veins, 
the  condition  found  in  the  adult  being  thus  established. 

More  recently  Huntington  and  McClure,1  working  with  cat  embryos,  have  also 
found  the  earliest  traces  of  the  lymphatic  system  in  a  series  of  spaces  which  appear  in 
the  tissue  surrounding  the  intima  of  the  anterior  cardinal  veins,  but  they  found  that 
these  spaces  have  at  first  no  connection  with  the  veins,  nor  are  they  outgrowths 
from  them.  The  anterior  cardinal  vein  of  each  side  is  early  divided  longitudinally 
into  two  portions  by  the  passage  through  it  of  the  cervical  nerves,  and  the  dorso- 
lateral portion  of  the  vein  later 
undergoes  retrogression,  the 
ventro-medial  portion  persisting 
as  the  internal  jugular.  As  the 
dorso-lateral  portion  shrinks,  the 
lymphatic  spaces  along  its  course 
rapidly  enlarge,  fuse  together, 
and  form  a  large  lymphatic  stem, 
which  subsequently  makes  con- 
nection with  the  subclavian  vein, 
and  thus  forms  the  primary 
lymphatic    trunk    of    the    body 

(Fig-  793)- 

Later,  spaces  develop  along 
the  course  of  the  anterior  cardinal 
veins  below  the  point  where  the 
subclavians  open  into  them,  but 
it  is  noticeable  that  those  occur- 
ring in  association  with  the  left 
vein,  which  undergoes  retrogres- 
sion, develop  more  rapidly  than 
those  accompanying  the  same 
portion  of  the  right  vein  and  form 
the  thoracic  duct  (Fig.  794),  this 
structure  thus  belonging  essen- 
tially to  the  left  half  of  the  body, 
since  the  principal  persistent  veins 
occur  on  the  right  side.  Similar 
spaces  appear  in  the  peri-intimal 
tissue  of  other  veins,  and  in  all 
cases  those  associated  with  retro- 
gressive veins  are  the  most  rapidly 
developed.  While  most  of  the 
principal  lymphatic  trunks  unite  with  the  thoracic  duct,  yet  they  may  also  form 
temporary  or  even  permanent  communications  with  other  veins  than  the  subclavian, 
certain  of  the  adult  anomalies  being  results  of  these  connections. 

From  these  observations  it  seems  that  the  lymphatics  arise  from  spaces  which 
are  primarily  independent  of,  although  associated  with,  the  veins,  and  that,  while  this 
mode  of  origin  of  the  lymphatics  applies  to  those  following  the  primitive  systemic 
veins,  yet  the  more  peripheral  portions  of  the  system  are  developed  by  a  process  of 
budding  from  the  main  stems,  just  as  is  the  case  with  the  smaller  branches  of  the 
blood-vessels.  By  this  budding  process  the  system  gradually  extends  throughout  the 
body,  invading  the  various  tissues,  the  invasion,  however,  failing  to  affect  certain  of 
the  tissues,  such  as  cartilage  and  the  central  nervous  system. 

The  development  of  the  lymph-nodes  has  been  recently  studied  by  Kling2  and 
by  Sabin.3  According  to  the  latter  investigator,  the  lymph-nodes  may  be  regarded 
as  formed  by  two  fundamental  parts — the  lymphoid  element,  consisting  of  lympho- 
cytes in  a  reticulum  surrounding  the  terminal  artery  and  its  capillaries  within  the 

1  Amer.  Jour,  of  Anatomy,  vol.  vi.,  1907.         -  Archiv  f.  mikros.  Anat,  Bd.  63,  1904. 
:i  Amer.  Jour,  of  Anatomy,  vol.  v.,  1905.  *  Amer.  Jour,  of  Anatomy,  vol.  v.,  1905. 


Developing  lymphatics  in  rabbit  embryo  of  n  mm.  (14  days); 
X  9.  Lymphatic  vessels  are  heavily  shaded  ;  veins  are  light.  In.J., 
Ex.J.,  internal  and  external  jugular  veins;  Pr.U.,  primitive  ulnar; 
Ex.M..  external  mammary;  Az.,  azygos;  VCL,  inferior  vena  cava  ; 
G.,  gastric;  S.M.,  superior  mesenteric;  V..  vitelline;  Sc,  subcar- 
dial; R.A.,  renal  anastomosis  of  subcardinals  ;  Pr.Fi.,  primitive 
fibular;  c.  b.,  connecting  branch  ;  An.  T.t  anterior  tibial;  c,  caudal ; 
3>  4,  5,  6,  position  of  corresponding  cervical  nerves.     (F.  T.  Lewis.*) 


THE   THORACIC   DUCT. 


941 


cords  and  germ-centres  respectively,  and  the  sinus-element,  represented  by  channels 
resulting  from  the  multiplication  of  the  lymph-vessels.  The  former,  or  vascular  factor, 
is  constant  and  present  in  the  simplest  nodule  ;  the  sinus-element,  on  the  contrary, 
varies,  sometimes  (as  in  the  usual  type  of  node)  being  developed  from  numbers 
of  closely  packed  lymph-ducts 


and,  therefore,  of  lymphatic 
origin,  and  at  other  times  (as 
in  the  hemolymph  nodes) 
being  venous  channels  occu- 
pied by  blood.  By  the  sub- 
sequent intergrowth  of  the 
lymphoid  element  and  the 
greatly  multiplied  lymph- 
capillaries,  the  intervening 
bridges  of  connective  tissue 
are  reduced  in  thickness  until 
finally  only  the  reticulum 
remains  and  the  lymphoid 
tissue  is  ultimately  brought 
into  intimate  relation  with 
the  surrounding  sinus.  In 
certain  nodes  the  sinus  retains 
its  character  as  a  direct  out- 
growth from  the  veins  and 
becomes  filled  with  erythro- 
cytes. Such  nodes  assume  the 
peculiarities  of  hemolymph 
nodes,  in  which  the  blood- 
sinuses  replace  those  that 
convey  lymph.  As  Sabin 
has  emphasized,  the  follicle 
is  the  anatomical  as  well  as 
the  vascular  unit,  the  simplest 
nodule  consisting  of  a  single 
follicle.  The  latter  may  be 
without  a  sinus,  or  surrounded 
by  one  which  is  either  a  lym- 
phatic or  a  venous  channel. 


F:c.  794. 


Developing  lymphatics  in  rabbit  embryo  of  21  mm.  (17  days);  X  6. 
Lymphatic  vessels  are  heavily  shaded  ;  veins  are  light;  for  significance 
of  lettering  see  preceding  figure;  in  addition.  Ce.,  cephalic  ;  Br.,  bra- 
chial: R.,  radial;  5j..  subscapular;  Sci.t  sciatic ;  /*>.,  femoral;  //., 
iliolumbar.     (F.   T.  Lewis.*) 


In  describing  the  various 
lymphatic  vessels  and  nodes  it 
will  be  convenient  to  consider 
first  the  great  terminal  trunks 
of  the  system,  the  thoracic 
and  right  lymphatic  ducts, 
and  then  discuss  the  remaining 
portions  of  the  system  from 
the  topographical  standpoint.  Attention  will  be  directed  primarily  to  the  nodes 
of  each  region,  the  course  of  the  lymph-paths  from  each  organ  and  their  relations 
to  the  nodes  being  subsequently  considered. 

THE  THORACIC  DUCT. 

The  thoracic  duct  (ductus  thoracicus)  (Fig.  795)  extends  from  the  lower  border 

of  the  second  lumbar  vertebra,  through  the  entire  length  of  the  thorax,  to  open  into 

the  left  subclavian  vein  close  to  the  point  where  it  is  joined    by  the  left  internal 

jugular.      Its  entire  length  is  from  43-46  cm.  (17-18  in.).      The  duct  lies  at  first  in 

*  Amer.  Jour,  of  Anatomy,  vol.  v.,  1905. 


942 


HUMAN   ANATOMY. 


front  of  the  first  and  second  lumbar  vertebrae,  and  passes  upward  through  the  aortic 
opening  of  the  diaphragm.      In  the  thorax  its  course,  although  slightly  sinuous,  in 

Fig.  795. 


Internal  jugular  vein 

Trachea 
Vertebral  vein- 
Right  lymphatic  duct 
Subclavian 


I.  rib 


Right  innominate 


CEsophagu 


Right  lumbar  lymph  trunk 


Crest  of  ilium  - 


Dissection  of  posterior  body-wall,  seen  from  in  front,  showing  thoracic  duct  and  right  lymphatic  duct ; 
veins  have  been  laterally  displaced  to  expose  terminations  of  thoracic  duct. 

general  is  at  first  almost  directly  upward,  a  little  to  the  right  of  the  median  line  of 
the  bodies  of  the  thoracic  vertebrae  ;   at  the  level  of  from  the  sixth  to  the  fourth 


THE   THORACIC   DUCT.  943 

vertebrae,  however,  it  begins  to  incline  slightly  towards  the  left,  and,  finally,  at  about 
the  lower  border  of  the  seventh  cervical  vertebra  it  changes  its  direction  somewhat 
abruptly,  passing  upward,  forward  and  to  the  left,  and  then  downward  and  forward, 
thus  forming  an  arch  whose  convexity  is  directed  upward  and  .  whose  extremity 
opens  into  the  subclavian  vein. 

The  thoracic  duct  is  formed  by  the  union  of  the  right  and  left  lumbar  trunks 
(trunci  lumbales)  which  drain  the  lumbar  nodes.  The  left  trunk,  shortly  before  its 
union  with  the  right,  is  usually  joined  by  an  unpaired  intestinal  trunk  (truncus  intes- 
tinalis)  that  drains  the  cceliac  and  mesenteric  nodes.  Just  above  its  commencement 
the  thoracic  duct  usually,  although  not  always,  presents  a  pyriform  enlargement,  the 
receptaculum  chyli  ( cisterna  chyli),  which  extends  upward  as  far  as  the  level  of 
the  eleventh  thoracic  vertebra,  and  measures  from  5-7.5  cm.  (2-3  in.)  in  length  and 
from  6-8  mm.  in  diameter.  Above  the  eleventh  thoracic  vertebra  the  duct  gradually 
diminishes  in  calibre  until  about  the  middle  of  its  course,  where  it  again  enlarges. 
The  thoracic  duct  possesses  few  valves  in  comparison  with  other  lymphatic  vessels, 
those  which  do  occur  being  frequently  insufficient.  Its  entrance  into  the  subclavian 
vein,  however,  is  guarded  by  two  well-developed  leaflets,  which  prevent  the  passage 
of  blood  into  the  duct. 

Relations. — In  its  abdominal  portion  the  thoracic  duct  lies  almost  in  the  median 
line  in  front  of  the  bodies  of  the  first  two  lumbar  and  twelfth  thoracic  vertebrae,  and 
between  the  crura  of  the  diaphragm,  or  under  cover  of  the  right  crus.  Anteriorly,  it 
is  in  relation  with  the  right  side  of  the  abdominal  aorta,  with  the  greater  azygos  vein 
to  the  right. 

In  its  thoracic  portion  it  lies  at  first  within  the  posterior  mediastinum,  but 
above,  it  enters  the  superior  mediastinum.  In  the  former  it  lies  anterior  to  the 
bodies  of  the  eleventh  to  the  fifth  thoracic  vertebrae,  and  has  in  front  of  it,  from 
below  upward,  the  pericardium,  the  oesophagus,  and  the  arch  of  the  aorta.  The 
thoracic  aorta  lies  to  the  left  of  it,  and  to  the  right  are  the  right  pleura  and  the 
greater  azygos  vein.  The  lower  right  intercostal  arteries  pass  between  it  and  the 
bodies  of  the  vertebrae,  as  does  also  the  terminal  portion  of  the  hemiazygos  vein. 
In  the  superior  mediastinum  it  rests  upon  the  lower  part  of  the  left  longus  colli 
muscle,  being  separated  by  it  from  the  bodies  of  the  upper  three  thoracic  vertebrae. 
Anteriorly,  it  is  in  relation  with  the  origin  of  the  left  subclavian  artery  and  with  the 
vertebral  vein  ;  to  the  left  is  the  left  pleura  and  to  the  right  are  the  oesophagus  and 
the  left  recurrent  laryngeal  nerve. 

Its  arch  is  in  relation  below  with  the  apex  of  the  left  lung  and  with  the  left  sub- 
clavian artery  ;  to  the  left  and  posterior  to  it  is  the  vertebral  vein  and  to  the  right 
and  anteriorly  are  the  left  common  carotid  artery,  the  left  internal  jugular  vein,  and 
the  left  pneumogastric  nerve. 

Tributaries. — In  addition  to  the  right  and  left  lumbar  and  the  intestinal  trunks 
by  whose  union  it  is  formed,  the  thoracic  duct  receives  on  either  side  ( 1 )  near  its 
origin,  a  descending  trunk  which  drains  the  posterior  nodes  of  the  lower  six  or  seven 
intercostal  spaces  ;  (2)  an  ascending  stem  from  the  upper  lumbar  nodes  which  trav- 
erses the  crus  of  the  diaphragm  and  joins  the  duct  at  about  the  level  of  the  ninth  or 
tenth  thoracic  vertebrae  ;  (3)  the  efferent  vessels  from  the  upper  posterior  intercostal 
nodes,  which  sometimes  unite  to  form  a  single  ascending  stem  opening  into  the  upper 
part  of  the  duct  ;  (4)  the  effere7it  vessels  of  the  posterior  mediastinal  nodes  ;  (5)  the 
left  jugular  trunk  ;  and,  occasionally,  (6)  the  left  subclavia?i  and  (7)  the  left  broncho- 
mediastinal trunks,  these  last  three  uniting  with  the  duct  just  before  it  opens  into  the 
subclavian  vein. 

Variations The   thoracic    duct   is   subject   to   numerous   variations,   so   much    so    that 

certain  authors  have  regarded  as  typical  arrangements  which  others  have  considered  to  be 
abnormal. 

Its  origin  is  frequently  opposite  the  body  of  the  first  lumbar  vertebra  or  even 
opposite  the  last  thoracic  ;  and  rarely  it  is  below  the  lower  border  of  the  second  lumbar. 
Instead  of  being  formed  by  the  union  of  only  two  trunks,  three  are  frequently  found 
participating  in  its  origin,  the  odd  one  being  the  intestinal  trunk  which  usually  opens  into 
the  left  lumbar  trunk.  Occasionally  all  three  trunks  are  represented  by  a  number  of  smaller 
stems  which  anastomose  with  one  another  as  well  as  with  the  descending  stems  from  the 
posterior   intercostal   nodes,  the   plexus  so  formed  communicating  by  a  number  of   efferents 


944  HUMAN   ANATOMY. 

with  the  receptaculum  chyli.  It  must  be  remembered  that  embryologically  what  are  usually 
termed  the  origins  of  the  thoracic  duct  are  in  reality  its  prolongations,  that  is  to  say,  outgrowths 
from  it,  so  that  possibilities  for  variation  in  these  stems  are  abundant. 

In  another  respect  the  embryological  history  of  the  duct  probably  throws  light  upon  its 
anomalies.  In  the  rabbit  the  spaces  formed  along  the  course  of  the  left  posterior  cardinal  vein 
frequently  unite  to  form  two  more  or  less  distinct,  parallel  stems,  which  together  represent  the 
thoracic  duct  (Fig.  794).  Whether  this  condition  also  exists  in  man  is  unknown,  but  if  it  does 
then  an  explanation  is  afforded  for  one  of  the  most  frequent  anomalies  of  the  duct,  namely,  its 
division  in  its  lower  part  into  two  parallel  stems  which  unite  again  after  a  longer  or  shorter  inde- 
pendent course.  This  condition  is  so  frequent  that  it  has  been  regarded  as  typical  by  some 
authors  ;  usually  the  union  of  the  two  stems  occurs  at  about  the  level  of  the  seventh  thoracic 
vertebra,  but  occasionally  they  remain  separate  throughout  the  entire  length  of  the  thorax  and 
may  be  connected  by  transverse  anastomoses. 

Another  group  of  anomalies,  probably  having  a  quite  different  embryological  basis,  includes 
cases  in  which  there  are  either  two  distinct  thoracic  ducts,  or  else  a  single  one  which  branches 
in  its  upper  part,  one  of  the  two  stems  in  either  case  passing  to  the  left  subclavian  vein  and  the 
other  to  the  right.  This  condition  is  due  to  the  fact  that  the  lymphatic  system  is  symmetrical  in 
its  embo'ological  origin,  a  trunk  arising  in  connection  with  the  right  azygos  vein  as  well  as  with 
the  left.  Ordinarily  the  left  trunk,  developing  more  rapidly  than  the  right,  becomes  the  thoracic 
duct,  while  the  right  outgrowth  remains  short  and  forms  the  right  lymphatic  duct.  Conditions 
might  occur,  however,  in  which  the  right  trunk  would  undergo  a  more  extensive  development 
and  either  unite  with  the  left  trunk  or  grow  downward  to  form  a  second  thoracic  duct,  thus 
producing  the  conditions  under  discussion.  A  further  modification  along  the  same  line  would 
lead  to  the  development  of  the  thoracic  duct  from  the  right  trunk,  the  left  giving  rise  only  to 
a  short  lymphatic  duct,  an  exact  reversal  of  the  normal  arrangement  being  thus  produced. 
Several  such  cases  have  been  recorded,  and  it  is  interesting  to  note  that  they  frequently 
accompany  abnormalities  of  the  aortic  arch,  such  as  the  origin  of  the  right  subclavian  from  the 
descending  portion  ;  the  anomaly  also  occurs,  however,  independently  of  any  variation  in  the 
blood-vessels. 

Considerable  variation  exists  in  the  level  to  which  the  arch  of  the  thoracic  duct  rises  in  the 
neck,  and  it  is  stated  that  it  may  lie  anywhere  between  the  levels  of  the  fifth  cervical  and  first 
thoracic  vertebra?. 

Likewise,  variations  in  the  mode  of  termination  of  the  thoracic  duct  are  often  observed. 
It  ma)'  open  into  the  subclavian  vein  at  some  distance  from  the  junction  of  the  internal  jugular, 
or,  occasionally,  into  its  posterior  surface,  and  not  infrequently  it  divides  near  its  termination 
into  two  or  more  stems  (Fig.  795),  which  may  open  into  the  internal  or  the  external  jugular 
or  into  the  azygos  or  vertebral  veins  as  well  as  into  the  subclavian.  The  connection  with  the 
azygos  vein  is  probably  of  frequent  occurrence. 

Practical  Considerations. — The  thoracic  duct  may  be  obstructed  by  (a) 
aneurism  of  the  arch  of  the  aorta  ;  (b)  enlarged  mediastinal  nodes  (tuberculous, 
lymphadenomatous,  or  carcinomatous)  ;  (c)  mediastinal  neoplasms — especially  if  in 
the  anterior  mediastinum  ;  (d)  exophthalmic  goitre  (very  rarely)  ;  (e)  thrombosis 
of  the  left  innominate  vein  or  of  the  subclavian  at  its  junction  with  the  internal  jugular  ; 
(/")  tricuspid  incompetence  (through  backward  pressure)  ;  (g)  cardiac  hyper- 
trophy ;  (h)  dense  pancreatic  growths  (Agnew)  ;  (z)  thrombosis  (tuberculous)  of 
the  duct  itself  ;  (/)  filarial  disease  (obstruction  by  the  parent  worms)  ;  (/£)  cicatri- 
cial contraction  or  adhesion  involving  the  duct  ;  (/)  disease  (tuberculous,  carcino- 
matous) of  the  walls  of  the  duct. 

The  duct  may  be  injured  (a)  during  operations — as  for  growths  or  enlarged 
glands — or  by  stab  or  bullet  wounds  (usually  in  its  cervical  portion)  ;  or  (b)  by 
grave  trauma,  as  fracture  dislocation  of  the  spine  (usually  in  the  thoracic  or  abdomi- 
nal portion),  or  violent  compression  of  the  thorax  ;  or  (c)  by  muscular  effort  or 
during  a  paroxysm  of  vomiting  (Busey),  or  whooping-cough  (Wilhelm). 

The  fact  that  the  duct  as  a  rule  extends  upward  but  little  if  at  all  above  the 
level  of  the  junction  of  the  internal  jugular  and  subclavian  renders  operative  injury  of 
it  rare,  but  as  it  occasionally  is  found  higher,  and  may  even  extend  to  5. 5  cm. 
(2^  in.)  above  the  upper  border  of  the  sternum,  its  possible  presence  and  its  rela- 
tions and  variations  {vide  supra)  should  not  be  forgotten  during  extensive  operations 
at  the  base  of  the  neck  on  the  left  side. 

The  results  of  obstruction  of  the  thoracic  duct  are  (a)  increased  pressure 
and  dilatation  of  the  vessels  behind  the  obstruction  ;  (b)  the  establishment  of 
collateral  circulation  and  entrance  of  lymph  into  the  general  circulation;  or — if 
such  collateral  circulation  is  not  established — (c)  leakage  by  transudation  into 
the  surrounding  tissues,  into  the  pleural  cavity  (rare),  or  into  the  peritoneal 
cavity  ;  or  (d)  rupture  of  the  duct  or  its  tributaries.     The  stomata  of  the  thin-walled 


THE   LYMPHATICS   OF   THE   HEAD.  945 

lymphatic  vessels  offer  little  obstacle  to  free  transudation,  which,  when  it  follows 
obstruction,  may  be  compared  to  the  hematemesis  seen  in  hepatic  cirrhosis  (Rolleston). 

The  symptoms  of  obstruction  are  neither  so  constant  nor  so  marked  as  they 
would  be  if  it  were  not  that  (a)  the  lymphatic  system  is  not,  like  the  veins,  a  series  of 
closed  vessels,  but  is  practically  continuous  with  the  interstices  of  the  tissues ;  and  that 
(b)  it  communicates  with  the  venous  system,  the  duct  itself  with  the  azygos  vein  in  the 
posterior  mediastinum,  and  the  smaller  lymphatics  with  venules  elsewhere — certainly, 
for  example,  in  the  inguinal  region,  and  probably  in  other  parts  of  the  body  (Leaf ). 

The  effects  of  obstruction  are  most  often  noticeable  when  the  interference  with 
the  flow  of  lymph  takes  place  near  the  termination  of  the  duct  on  the  outer  side  of 
the  internal  jugular  vein,  near  its  junction  with  the  subclavian.  This  is  probably 
due  to  (<z)  the  frequency  of  tumor  or  of  injury  in  this  situation  ;  (b)  the  consolida- 
tion of  the  lymph-vessels  here  into  a  single  trunk  ;  (c)  the  greater  difficulty  in  estab- 
lishing a  compensatory  collateral  circulation  between  the  parts  of  the  duct  above  and 
below  the  obstruction  than  if  the  latter  were  lower  down  (Rolleston). 

Chylous  ascites  may  be  due  either  to  obstruction  with  transudation  of  chyle 
from  distended  lacteals  into  the  peritoneal  cavity,  or  to  wound  or  rupture  of  the 
thoracic  duct,  or  of  the  larger  lymph-vessels,  or  of  varicose  lymph-vessels,  or  of 
lymphangiomata.  Chylous  pleural  effusions  may  similarly  result,  or  an  effusion  fol- 
lowing wound  or  rupture  may  be  partly  thoracic  and  partly  abdominal,  as  in  a  case 
in  which,  after  extreme  compression  of  the  chest,  death  followed  in  three  weeks,  and 
the  thoracic  duct  was  found  ruptured  where  it  traversed  the  hiatus  aorticus  (Bellamy). 

When  the  receptaculum  chyli  is  involved,  the  thoracic  duct  above  may  be  quite 
healthy,  and  lymph  may  pass  into  it  by  anastomotic  channels  and  no  chylous  ascites 
be  produced. 

Carcinoma  of  the  aortic  or  mesenteric  nodes  may  cause  enough  dilatation  of  the 
lymphatics  to  bring  about  chylous  ascites. 

THE  RIGHT  LYMPHATIC  DUCT. 

The  right  lymphatic  duct  (ductus  lymphaticus  dexter)  (Fig.  795)  opens  into  the 
right  subclavian  vein  and  is  a  very  short  stem,  rarely  having  a  length  of  more  than 
from  10-12  mm.  It  is  formed  by  the  union  of  the  right  jugular  and  subclavian 
lymphatic  trunks,  the  right  broncho-mediastinal  trunk  rarely  contributing  to  its 
formation,  but  having  usually  an  independent  opening  into  the  subclavian  vein. 
Very  frequently  no  right  lymphatic  duct  exists,  the  jugular  and  subclavian  trunks, 
as  well  as  the  broncho-mediastinal,  opening  independently  into  the  vein. 

THE    LYMPHATICS    OF   THE    HEAD. 
The  Lymph-Nodes. 

The  lymphatic  nodes  of  the  head  are  arranged  in  groups,  which,  for  the  most 
part,  are  situated  along  the  line  of  junction  of  the  head  and  neck  regions,  that  is  to 
say,  along  a  line  extending  from  the  external  occipital  protuberance  to  the  temporo- 
mandibular articulation  and  thence  along  the  rami  of  the  mandible.  A  few  small  nodes 
also  occur  upon  the  cheeks,  and  others  which  lie  upon  the  surfaces  of  the  hyo-glossus 
and  genio-hyo-glossus  muscles  and  upon  the  upper  part  of  the  posterior  surface  of 
the  pharynx  may  be  regarded  as  belonging  to  the  head  region.  Including  these, 
the  various  groups  recognizable  in  the  region  are  (1)  the  occipital,  (2)  the  posterior 
auricular,  (3)  the  anterior  auricular,  (4)  the  parotid,  (5)  the  submaxillary,  (6)  the 
submental,  (7)  the  facial,  (8)  the  lingual,  and  (9)  the  retropharyngeal  groups. 

The  occipital  nodes  (lymphoglandulae  occipitales)  are  from  one  to  three  in  num- 
ber and  are  situated  at  the  base  of  the  occipital  triangle,  immediately  lateral  to  the 
border  of  the  trapezius  muscle  and  resting  upon  the  upper  part  of  the  semispinalis 
capitis  (Fig.  796).  Their  afferenfs  come  from  the  occipital  portion  of  the  scalp  and 
their  efferents  pass  to  the  upper  nodes  of  the  superior  deep  cervical  group. 

The  posterior  auricular  or  mastoid  nodes  (lymphoglandulae  auriculares 
posteriores)  are  usually  two  in  number  and  are  of  small  size  ;  they  rest  upon  the 
mastoid  portion  of  the  insertion  of   the  sterno-cleido-mastoid    muscle  (Fig.    796). 

60 


946 


HUMAN    ANATOMY. 


Their  afferent s  are  from  the  temporal  region  of  the  scalp,  from  the  posterior  surface 
of  the  pinna  and  of  the  external  auditory  meatus.  Their  efferents  pass  to  the  upper 
nodes  of  the  superior  deep  cervical  group. 

The  anterior  auricular  nodes  (lymphoglandulae  auriculares  anteriores)  vary  from 
one  to  three  in  number  and  are  situated  immediately  in  front  of  the  tragus,  beneath 
the  parotid  fascia.  Their  afferents  come  from  the  anterior  surface  of  the  pinna  and 
of  the  external  auditory  meatus,  from  the  integument  of  the  temporal  region,  and 
from  the  outer  portions  of  the  eyelids.  Their  efferents  pass  to  the  superior  deep 
cervical  nodes. 

The  parotid  nodes  ( lymphoglandulae  parotideae)  are  situated  in  the  substance 
of   the    parotid    gland    (Figs.    796,    801).       They   are    quite    numerous   and   vary 

greatly    in   size.      They 
Fig.  796.  receive     afferents     from 

the  same  regions  as  the 
anterior  auricular  nodes, 
and  the  lower  nodes  of 
the  group  also  receive 
stems  from  the  soft 
palate.  Their  efferents 
pass  to  the  superior 
deep  cervical  nodes. 

The  submaxillary 
nodes  (lymphoglandulae 
submaxillares)  are  from 
three  to  eight  or  more 
in  number,  forming  a 
chain  along  the  lower 
border  of  the  horizontal 
ramus  of  the  mandible, 
as  far  forward  as  the 
attachment  of  the  ante- 
rior belly  of  the  digastric 
muscle  (Fig.  796).  One 
node  which  rests  upon 
the  facial  artery  just 
before  it  passes  over  the 
ramus  of  the  mandible  is 
larger  than  the  rest,  and 
this,  together  with  two 
others,  which  are  some- 
what smaller  and  lie  one 
on  either  side  of  the 
larger  node,  are  the 
most  constant  represen- 
tatives of  the  group,  the 
remaining  nodes  being 
usually  still  smaller  and 
Occasionally  a  small  node  occurs  imbedded 
These   nodes   receive,  as  afferents, 


Superficial  lymphatii 


vessels  and  node 
cmidiagrammatic 


varying  both  in  number  and  position 

ra   the   substance   of  the   submaxillary  gland. 

vessels  from  the  submental   and   facial  nodes  and  also  directly  from  the  territory 

drained  by  the  latter,  namely,  the  upper  lip,  the  outer  surface  of  the  nose  and  the 

cheek,   from  the   inner   portions  of   the  eyelids,   from  the   lower  lip,   the  gums  of 

both  jaws,  and  from  the  anterior  part  of  the  tongue.     Their  efferents  descend  upon 

the  surface  of  the  submaxillary  gland  to  open  into  the  superior  deep  cervical  nodes, 

especially  into  those  situated  in  the  neighborhood  of  the  bifurcation  of  the  common 

carotid  artery. 

The  submental  nodes  are  two  or  sometimes  three  in  number,  and  are  situated 
in  the  triangular  space  included  between  the  anterior  bellies  of  the  two  digastric 
muscles,  each  of  the  two  principal  nodes  resting  upon  the  inner  border  of  one  of  the 


THE   LYMPHATICS    OF    THE    HEAD. 


947 


muscles  (Figs.  796,  797).  They  receive  afferents  from  the  integument  of  the  chin, 
from  the  lower  lip,  and  from  the  floor  of  the  mouth  ;  their  efferents  pass  partly  to  the 
submaxillary  nodes  and 

partly  to  a  node  of  the  FlG-   797- 

superior  deep  cervical 
group  situated  on  the 
internal  jugular  vein  a 
little  above  the  level  at 
which  it  is  crossed  by 
the  omo-hyoid  muscle. 
The  facial  nodes 
(lymphoglandulae  faciales 
profundae)  consist  of  sev- 
eral small  groups  (Fig. 
798).  One  of  these  is 
composed  of  two  or  three 
nodes  situated  upon  the 
outer  surface  of  the 
horizontal  ramus  of  the 
mandible,  in  front  of 
the  anterior  border  of 
the  masseter  muscle  ; 
these  may  be  termed 
the  mandibular  nodes. 
A  second  group  is  to  be 
found  resting  upon  the 
surface  of  the  buccinator 


Submaxillary  and  submental  lymph-nodes 


born  child.     (Sta/ir*) 


■^-Maxillary  node 


muscle,  and  its  nodes  are  therefore  termed  the  buccinator  nodes.  They  are  three 
or  four  in  number  and  are  situated  in  the  interval  between  the  facial  vein  and  artery, 
or  posterior  to  the  vein,  almost  opposite  the  angle  of  the  mouth  and  either  beneath 

or     slightly     below      the 
Fig.  -qS.  zygomaticus    major.       A 

third  group  is  formed  by 
the  maxillary  nodes, 
which  are  somewhat 
scattered,  one  or  two 
occurring  in  the  groove 
formed  by  the  junction  of 
the  nose  and  cheek,  while 
another  rests  upon  the 
malar  bone  near  the  lower 
border  of  the  orbit.  These 
maxillary  nodes  are  nor- 
mally quite  small  and  may 
readily  be  overlooked. 

The  affei-ents  for  the 
various   groups    of   facial 
nodes    take    their    origin 
in   the  upper  lip,    in   the 
integument   and    mucous 
membrane    of    the    nose 
and  cheek,  and  probably 
also    in    the   eyelids,    the 
conjunctiva,  and  the  lachrymal  gland.    Their  efferents  pass  to  the  submaxillary  nodes. 
The  lingual  nodes  (lymphoglandulae  linguales)  are  a  number  of  small  enlarge- 
ments situated  upon  the  vessels  which  drain  the  lymphatic  capillaries  of  the  tongue. 
They  do  not  possess  any  very  definite  grouping  and  are  to  be  found   upon   both 

*  Archiv  f.  Anat.  u.  Physiol.,  1S9S. 
t  Beitrage  zur  klin.  Chirurgie,  Bd.  39. 


Mandibular  node 


Facial  lymph-node 


HUMAN    ANATOMY. 


surfaces  of  the  hyo-glossus  muscle  and  in  the  interval  between  the  two  genio-hyo- 
glossi.  From  the  surgical  standpoint  they  are  of  comparatively  little  importance, 
and  have  been  termed  "intercalated  nodes,"  to  distinguish  them  from  the  true 
terminal  nodes  of  the  lingual  lymphatics  (page  954),  in  which  enlargement  occurs  in 

cases  of  cancerous  or 


Longus  colli  muscle,  stump 


Fig.  799. 


Internal 


Retropharyngeal  lymph-nodes.     {Most.*) 


other   infection  of  the 
tongue. 

The  retro-phar- 
yngeal  nodes  are  for 
the  most  part  small, 
appearing  as  slight  en- 
largements of  the  lym- 
phatics which  drain  the 
posterior  surface  of  the 
pharynx.  In  addition 
to  these  ' '  intercalated 
nodes, ' '  however,  one 
or  two  much  larger 
nodes  occur  at  the  junc- 
tion of  the  lateral  and 
posterior  surfaces  of 
the  pharynx,  about  on 
a  level  with  the  anterior 
arch  of  the  atlas.  They 
are  imbedded  in  the 
bucco-pharyngeal  fas- 
cia and  rest  upon  the 
lateral  portions  of  the 
rectus  capitis  anticus  major.  Afferents  come  to  them  from  the  upper  part  of  the 
pharynx  and  from  the  mucous  membrane  of  the  nose,  and  their  efferents  pass  to  the 
upper  deep  cervical  nodes  (Fig.  799). 

The  Lymphatic  Vessels. 

The  Scalp. — The  lymphatics  of  the  scalp  form  a  rich  net -work,  which  is  espe- 
cially dense  in  the  neighborhood  of  the  vertex,  the  meshes  becoming  more  elongated 
as  the  vessels  pass  away  from  the  median  line.  From  the  frontal  region  some  ten  to 
twelve  vessels  pass  downward  and  backward  to  terminate  in  the  parotid  nodes  ;  from 
the  parietal  and  temporal  regions  from  six  to  ten  vessels  pass  downward,  some  in 
front  of  the  external  auditory  meatus  to  terminate  in  the  anterior  auricular  and  paro- 
tid nodes,  and  some  behind  the  meatus  to  reach  the  posterior  auricular  nodes  ;  and 
from  the  occipital  region  the  more  posterior  vessels  pass  downward,  partly  to  the 
occipital  and  partly  to  the  superior  deep  cervical  nodes,  while  the  more  anterior  five  or 
six  converge  to  form  a  single  large  trunk  which  descends  along  the  posterior  border 
of  the  sterno-cleido-mastoid  muscle  and  terminates  in  the  inferior  deep  cervical  nodes. 

The  Brain  and  the  Meninges. — No  lymphatic  vessels  have  as  yet  been  cer- 
tainly demonstrated  either  in  the  central  nervous  system  or  in  the  meninges,  although 
they  have  been  described  as  accompanying  the  middle  meningeal  artery  in  the  dura 
mater  and  the  middle  cerebral  artery  in  the  pia  (Poirier).  Lymph-spaces,  how- 
ever, some  of  them  of  considerable  size,  are  abundantly  present.  Of  these  there  may 
be  mentioned,  first,  the  pericellular  spaces  which  surround  the  individual  cells  of  the 
brain  and  spinal  cord,  both  the  actual  nerve-cells  and  the  neuroglia-cells,  those 
accompanying  the  latter  extending  along  their  processes  to  communicate  with  an 
epicerebral  space  believed  to  exist  between  the  surface  of  the  brain  and  the  pia  (His), 
and  also  with  spaces  which  occur  along  the  course  of  the  cerebral  blood-vessels.  Of 
this  second  group  of  spaces,  the  perivascular  spaces,  two  sets  have  been  described, 
one  occurring  in  the  adventitia  surrounding  the  vessels  and  the  other  between  the 
adventitia  and  the  brain  substance,  and,  accompanying  the  blood-vessels  into  the  pia, 

*  Archiv  f.  klin.  Chirurgie,  Bd.  41,  1900. 


THE    LYMPHATICS    OF    THE    HEAD. 


949 


they  communicate  with  the  subarachnoid  spaces.  The  third  group  of  spaces  is 
formed  by  the  subdural  and  subarachnoid  spaces,  but  no  special  description  need  here 
be  given  of  these,  since  they  are  more  properly  described  (page  1197)  as  portions  of 
the  meninges  than  as  parts  of  the  lymphatic  system.  By  some  authors  an  epidural 
space,  situated  between  the  dura  and  the  skull,  is  also  recognized. 

Lymph-spaces  have  been  described  as  occurring  in  the  substance  of  both  the  dura 
and  the  pia,  forming  in  the  latter  a  rather  close  net-work  with  which  the  perivascular 
spaces  communicate.  The  spaces  of  both  membranes  communicate  with  the  subdural 
space,  and  those  of  the  dura  are  said  also  to  communicate  with  the  epidural  space. 

Practically  nothing  is  yet  known  concerning  the  lymphatics  of  the  spinal  cord. 

The  Eye  and  Orbit. — No  lymphatic  vessels  have  as  yet  been  described  as 
occurring  in  the  orbital  tissues,  nor  do  they  occur  in  the  eyeball.  But,  on  the  other 
hand,  numerous  lymph-spaces  occur  in  connection  with  the  latter  structure,  one  of 
the  most  important  of  these  being  the  space  of  Tenon  (spatium  interfasciale),  with 
which  the  remaining  spaces  communicate  more  or  less  directly  (Fig.  800).  A 
description  of  this  space  has  already  been  given  (page  504),  but  it  may  be  recalled 
that,  in  the  first  place,  the  space  is  continued,  by  means  of  the  supravaginal  lymph- 


Fig.  800. 


Conjunctival  sac 
Space  of  Te 


ial  lymph-spaces. 


path  surrounding  the  optic  nerve,  along  the  latter  to  the  apex  of  the  orbit,  where 
it  communicates  with  the  subdural  space  of  the  cranium,  injection  of  that  space 
resulting  in  the  injection  of  the  space  of  Tenon  (Schwalbe),  and,  secondly,  that  the 
sheaths  of  the  anterior  portions  of  the  orbital  muscles  are  formed  by  reflections  of  the 
capsule  of  Tenon,  so  that  no  obstacles  exist  in  the  way  of  the  passage  of  lymph 
from  the  muscles  into  the  space. 

The  cavities  occupied  by  the  vitreous  and  aqueous  humors  have  also  been  re- 
garded as  lymph-spaces,  and  pericellular  spaces  in  the  cornea,  which  come  into  rela- 
tion with  the  lymphatic  vessels  of  the  conjunctiva  at  the  corneal  margin,  are  readily 
demonstrable.  In  the  tissue  of  the  sclerotic  spaces  also  occur,  communicating  on 
the  one  hand  with  the  space  of  Tenon  and  on  the  other  with  suprachoroid  spaces 
which  are  abundantly  present  in  the  lamina  fusca  of  the  choroid  coat  and,  by  means 
of  spaces  accompanying  the  vena?  vorticosse,  communicate  with  the  space  of  Tenon. 

In  the  eyelids,  conjunctiva,  and  lachrymal  apparatus  true  lymphatic  vessels  occur. 
In  the  eyelids  three  net-works  have  been  distinguished,  one  of  which  is  subcutaneous, 
the  second  lies  immediately  external  to  the  tarsal  plate,  and  the  third  is  subconjunctival. 
Communicating   branches   pass  between   adjacent  plexuses,   especially  between  the 


95° 


HUMAN    ANATOMY. 


subcutaneous  and  prsetarsal  ones,  and  all  three  are  united  at  the  palpebral  margins 
in  a  rather  finely  meshed  plexus.  Efferents  pass  both  toward  the  inner  and  the 
outer  angle  of  the  orbit,  and  the  former  pass  downward,  obliquely  across  the  cheek, 
in  company  with  the  facial  vein,  to  terminate  in  the  submaxillary  nodes,  possibly 
making  connections  with  some  of  the  facial  nodes  on  their  way  (Fig.  798).  The 
outer  ones  pass  partly  to  the  anterior  auricular  and  partly  to  the  upper  parotid  nodes. 
In  the  conjunctiva  two  net-works  occur,  one  situated  in  the  superficial  and  the 
other  in  the  deeper  layers  of  the  conjunctival  dermis.  Communicating  stems  pass 
between  the  net-works,  which  are  much  finer  in  the  neighborhood  of  the  corneal 
margin  than  more  peripherally.  They  come  into  relation  with  the  pericellular 
lymph-spaces  of  the  cornea,  and  their  efferents  pass  toward  the  outer  and  inner 
angles  of  the  orbit,  to  accompany  the  palpebral  efferents  to  the  submaxillary, 
posterior  auricular,   and  parotid  nodes. 

Of  the  lymphatic  vessels  of  the  lachrymal  gland  but  little  is  known,  but  in  ma- 
lignant diseases  of  the  gland  enlargement  of  some  of  the  facial  and  anterior  auricular 
nodes  has  been  observed,  and  it  is  probable  that  vessels  from  the  gland  accompany 
the  palpebral  and  conjunctival  efferents.  The  vessels  from  the  nasal  duct  probably 
partly  accompany  branches  of  the  facial  vein  to  the  facial  nodes,  while  those  from  its 
lower  portion  pass  with  the  efferents  from  the  nasal  mucous  membrane  to  the  retro- 
pharyngeal and  superior  deep  cervical  nodes. 

The  Ear. — No  true  lymphatics  have  yet  been  observed  in  the  tissues  of  the 
internal  ear,  but  the  space  which  intervenes  between  the  osseous  wall  of  the  ear 
cavity  and  the  membranous  ear  has  been  regarded  as  a  lymph-space,  and  on  that 

account    has    been    termed    the 
Fig.   801.  perilymphatic    space.       It    com- 

municates with  the  subdural 
space  of  the  cranium  by  the 
aqueductus  cochleae  and  by  the 
prolongations  of  it  which  accom- 
pany the  ductus  endolymphaticus 
and  the  auditory  nerve. 

In  the  middle  ear  spaces 
have  been  observed  in  the  con- 
nective tissue  lining  the  bony 
walls,  as  well  as  in  that  of  the 
tympanic  membrane.  In  addi- 
tion a  feebly  developed  net- work 
has  been  described  as  occurring 
beneath  the  epithelium  lining  the 
inner  (tympanic)  surface  of  the 
tympanic  membrane,  efferents 
from  it  accompanying  the  tym- 
panic artery  and  terminating  in 
the  parotid  nodes. 

Much  more  extensively 
developed  are  the  lymphatic 
vessels  of  the  external  ear. 
Beneath  the  epithelium  covering 
the  outer  (meatal)  surface  of  the 
tympanic  membrane  there  is  a 
very  fine  net-work,  whose  effer- 
ents accompany  the  blood-vessels, 
radiating  toward  the  periphery  of  the  membrane,  and  eventually  open  partly  into  the 
posterior  and  partly  into  the  anterior  auricular  nodes.  A  net-work  also  occurs 
throughout  the  entire  extent  of  the  external  auditory  meatus,  its  efferents  having 
the  same  destination  as  those  of  the  pinna. 

The  vessels  of  the  last  named  portion  of  the  ear  form  a  rich  net-work  extending 
throughout  the  whole  extent  of  the  organ,  and  from  it  stems  pass  in  three  principal 
*Anatom.  Anzeiger,  Bd.  xv.,  1899. 


THE    LYMPHATICS    OF    THE    HEAD. 


95i 


directions  ;  it  must  be  recognized,  however,  that  this  classification  of  the  stems  into 
three  groups  does  not  imply  a  corresponding  division  of  the  net-work  into  distinct 
areas,  since  there  is  a  considerable  overlapping  of  the  areas  drained  by  the  various 
stems,  and,  indeed,  stems  from  the  same  region  may  pass  in  some  cases  with  one  of 
the  group,  and  in  others  with  another.  From  the  outer  (anterior)  surface  the 
stems  pass  mainly  to  the  anterior  auricular  nodes,  a  few  bending  backward  over  the 
helix  and  terminating  in  the  posterior  auricular  nodes.  From  the  upper  part  of  the 
posterior  surface  (Fig.  801)  the  stems  pass  mainly  to  the  posterior  auricular  nodes, 
some,  however,  continuing  past  them  to  terminate  in  the  external  jugular  nodes. 
From  the  lower  part  of  the  pinna,  including  the  lobule,  a  number  of  stems  pass  to 
the  parotid  nodes. 

The  Nasal  Region. — The  lymphatic  vessels  of  the  integument  of  the  nose 
(Fig.  802)  form  numerous  anastomoses  with  those  of  the  mucous  membrane,  especially 
with  those  of  the  middle  and  inferior  meatuses,  and  those  of  the  one  side  of  the  nose 
are  also  continuous  with  those  of  the  other  side.  Some  of  the  vessels  which  drain 
the  upper  portion  of 

the  nasal  integument  Fig.  802. 

pass  almost  directly 
backward  to  the 
parotid  nodes,  but 
the  principal  path, 
followed  by  vessels 
from  all  parts  of  the 
nasal  integument, 
is  downwards  and 
backwards  across 
the  cheek,  in  com- 
pany with  the  facial 
blood  -  vessels.  In 
their  course  some  of 
them  traverse  some 
of  the  facial  nodes, 
which  appear  as  if 
intercalated  in  their 
course,  but  the  ma- 
jority pass  directly 
to  the  submaxillary 
nodes. 

A  rich  1  y  m- 
phatic  net-work  lies 
beneath  the  mucous 
membrane      of     the 

nasal  cavities,  and  from  it  vessels  pass  in  two  directions.  Those  of  the  anterior  and 
lower  portions  of  the  fossa?  pass  forward  and,  partly  at  the  external  nares  and  partly  by 
passing  between  the  nasal  bones  and  the  cartilages,  communicate  with  the  superficial 
nasal  lymphatics.  The  majority  of  the  vessels,  however,  take  a  backward  course, 
terminating  in  different  node  groups.  Some  join  the  vessels  draining  the  palate  and 
tonsils  to  pass  to  the  superior  deep  cervical  nodes  and  especially  to  that  one  which  is 
situated  in  the  angle  formed  by  the  union  of  the  facial  and  internal  jugular  veins, 
while  the  rest  unite  to  form  from  two  to  four  stems  which  pass  over  the  lateral  surface 
of  the  pharynx  and  terminate  in  the  retropharyngeal  nodes. 

The  lymphatics  of  the  sinuses  which  open  into  the  nasal  cavities  follow,  in  part 
at  least,  the  same  courses  as  those  of  the  nasal  mucous  membrane,  their  principal 
termination  being  in  the  larger  retropharyngeal  nodes. 

The  Cheeks,  Lips,  Gums,  and  Teeth. — The  lymphatics  from  the  more 
posterior  portions  of  the  cheeks  empty  into  the  parotid  nodes  ;  those  from  the 
more  anterior  portions  pass  to  the  submaxillary  nodes,  and  the  deeper  ones 
communicate  with  the  facial  nodes. 

*  Beitrage  f.  klin.  Chirurgie,  Bd.  xxv.,  1899. 


and  cheek.     {Ktittner.*) 


952 


HUMAN    ANATOMY. 


The  vessels  from  the  submucous  tissues  of  the  lips  pass  mainly  to  the  submaxil- 
lary nodes,  two  or  three  stems  passing  from  the  lower  lip  and  one  or  two  from  the 
upper.  Those  of  the  lower  lip  pass  downward  and  outward  toward  the  facial  artery 
and  follow  its  course  into  the  submaxillary  region,  while  those  from  the  upper  lip  are 
directed  at  first  almost  horizontally  outward  toward  the  facial  vein,  whose  course 
they  follow  toward  their  termination.  No  anastomoses  occur  between  the  submucous 
vessels  of  the  two  sides  in  either  lip. 

The  subcutaneous  vessels  of  the  upper  lip  (Fig.  803)  have  a  course  similar  to 
that  of  the  corresponding  submucous  stems,  with  which  they  may  unite,  and  they 
terminate  principally  in  the  submaxillary  nodes,  although  communicatjon  may  also  be 
made  with  one  of  the  lower  parotid  nodes.  The  subcutaneous  vessels  of  the  lower  lip 
are  from  two  to  four  in  number,  and  pass  principally  to  the  submental  nodes,  from  which 

efferents  pass  to  the  sub- 
Fig.  803.  maxillary     and     superior 

deep  cervical  nodes.  A 
noteworthy  peculiarity  of 
these  lower  lip  vessels, 
which  is  in  marked  con- 
trast with  what  obtains  in 
the  submucous  stems,  is 
that  those  of  the  right 
and  left  halves  of  the  lip 
anastomose,  so  that  an 
injection  may  pass  from 
the  vessels  of  the  right 
half  into  the  left  sub- 
mental and  submaxillary 
nodes. 

The  lymphatics  of 
the  lower  gums  form  a 
very  rich  net-work  from 
which  from  fourteen  to 
seventeen  stems  arise. 
These  empty  into  a  single 
large  collecting  stem  on 
either  side,  which  passes 
outward  over  the  outer 
surface  of  the  mandible 
and,  opposite  the  last 
molar  tooth,  dips  down- 
ward to  terminate  in 
the  submaxillary  nodes. 
Whether  or  not  the  pulp 
of  the  teeth  contains  lymphatic  capillaries  is  a  disputed  question.  All  attempts  to 
inject  them  have  failed,  but  it  has  been  maintained  that  their  existence  has  been 
demonstrated  by  histological  methods.  Enlargement  of  the  submaxillary  nodes  has 
been  observed  to  follow  dental  lesions,  but  this  may  be  due  to  the  involvement  of  the 
tissues  of  the  gums  rather  than  to  that  of  the  tooth  pulp. 

The  Tongue. — The  lymphatics  of  the  tongue  (Fig.  804)  are  divisible  into  two 
groups  according  as  they  arise  in  the  submucous  tissue  or  in  the  musculature.  The 
submucous  vessels  take  their  origin  from  an  exceedingly  rich  net-work  which  extends 
throughout  the  entire  surface  of  the  tongue.  It  is  especially  close  toward  the  tip, 
the  meshes  becoming  larger  posteriorly,  and  that  portion  of  it  which  lies  posterior  to 
the  circumvallate  papilla?  is  independent  of  that  of  the  more  anterior  portions  of  the 
tongue.  The  vessels  of  the  muscular  portion  of  the  organ  are  much  less  extensively 
developed  and  the  efferent  stems  which  pass  from  them  early  unite  with  those  of 
the  submucous  net-work.  These  latter  are  quite  numerous  and  for  purposes  of 
description  may  be  arranged  in   four  groups. 

*  Internat.  Monatsschrift  f.  Anat.  u.  Physiol.,  1900. 


THE    LYMPHATICS    OF    THE    HEAD. 


953 


The  first  or  apical  group  (Fig.  805)  consists  of  from  two  to  four  stems  which 
arise  from  the  net-work  at  the  tip  of  the  tongue  and  pass  downward  and  backward, 
half  of  them  lying  on  one  side  of  the  frenum  and  half  on  the  other  side.  They  follow 
at  first  the  anterior  border  of  the  genio-hyo-glossus  muscle  and  then  pass  upon  the 
outer  surface  of  that  muscle  and  are  continued  downward  and  backward,  either 
external  or  internal  to  the  hyo-glossus,  until  they  reach  the  greater  cornu  of  the 
hyoid  bone,  just  below  the  attachment  of  the  stylo-hyoid.  They  then  cross  obliquely 
over  the  outer  surface  of  the  greater  cornu,  and  are  continued  down  the  neck  along 
the  outer  border  of  the  omo-hyoid  muscle  to  open  into  one  of  the  inferior  deep 
cervical  nodes  situated  upon  the  jugular  vein  just  above  the  point  where  it  is  crossed 
by  the  omo-hyoid  muscle.  Sometimes  an  additional  apical  stem  passes  down  the 
frenum  in  company  with  those  just  described,  but  continues  on  downward  to 
perforate  the  mylo-hyoid  muscle  and  terminate  in  one  of  the  submental  nodes. 

A  second  or  lateral g7'oup  consists  of  a  number  of  vessels  which  emerge  from  the 
net-work  along  the  borders  of  the  tongue  (Fig.  804).  There  are  from  eight  to  twelve 
stems    in    this    group    on 

either  side,   and  all  are  at  FlG-  s°4- 

first  directed  almost  verti- 
cally downwards,  a  few, 
three  or  four,  passing  later- 
ally to  the  sublingual  gland 
and  the  rest  medial  to  it. 
The  former  continue  their 
downward  course,  perforate 
the  mylo-hyoid  muscle,  and 
terminate  in  the  submaxil- 
lary nodes,  while  the  others 
take  a  course  obliquely 
downward  and  backward, 
and,  passing  some  upon 
the  median  and  others 
upon  the  lateral  surface 
of  the  hyo-glossus  muscle, 
terminate  in  the  superior 
deep  cervical  nodes  and 
especially  in  one  situated  a 
little  above  the  level  of  the 
bifurcation  of  the  common 
carotid  artery.  This  node, 
on  account  of  its  relations  to 
these  lingual  stems,  has  been 
termed  the  principal  node 
of  the  tongue  (  Fig.  805  ) . 

A  third  or  basal  group  takes  its  origin  from  the  dense  portion  of  the  submucous 
net-work  which  surrounds  the  circumvallate  papilla?  and  the  foramen  caecum.  Four 
stems  issue  from  the  net-work  in  the  neighborhood  of  the  median  line,  and  two  on  each 
side  more  laterally.  The  median  stems  pass  at  first  directly  backward  and  then  bend 
outward  in  the  glosso-epiglottidean  folds,  two  on  either  side,  and  join  the  lateral  stems 
beneath  the  tonsils.  The  lateral  stems,  which  drain  the  regions  of  the  lateral  circum- 
vallate papilla?,  the  foliate  papillae,  and  the  glandular  region  of  the  tongue,  are  directed 
backward  towards  the  lower  border  of  the  tonsil,  and,  after  being  joined  in  that  situation 
by  the  median  stems,  they  pass  deeply  to  terminate  in  the  superior  deep  cervical  nodes. 

Finally,  a  fourth  or  median  group  arises  from  the  net-wrork  of  the  median 
portion  of  the  tongue,  anterior  to  the  circumvallate  papillae.  These  stems  are  five 
or  six  in  number,  and  pass  at  first  directly  downward  through  the  substance  of  the 
tongue  and  through  the  interval  which  separates  the  two  genio-hyo-glossal  muscles. 
One  or  two  of  them  then  continue  in  their  downward  course  and  pass,  in  some  cases 


Lymphatics  of  dorsiu 


tongue.     (Kuttner*) 


*  Beitrage  f.  klin.  Chirurgie,  Bd.  xxi.,  1895. 


954 


HUMAN    ANATOMY. 


to  the  right  and  in  some  to  the  left,  between  the  genio-hyo-glossus  and  the  genio- 
hyoid muscles,  perforate  the  mylo-hyoid,  and  terminate  in  the  submaxillary  nodes. 
The  remaining  three  or  four  stems  pass  backward  along  the  mylo-hyoid  muscle 
and,  emerging  at  its  posterior  border,  pass  to  the  superior  deep  cervical  nodes. 

From  this  account  it  will  be  seen  that  four  different  groups  of  nodes  stand  in 
relation  to  the  lymphatics  of  the  tongue.  ( i )  The  submental  nodes  receive  a  stem 
from  the  tip  ;  (2)  the  submaxillary  nodes  receive  stems  from  the  marginal  and  cen- 
tral regions  ;  (3)  the  superior  deep  cervical  nodes  receive  stems  from  the  marginal, 
central,  and  basal  regions  ;  and  (4)  the  inferior  deep  cervical  nodes  receive  a  stem 

from  the  apical  region. 


Fig.  S05 . 


In  addition  it  may  be 
mentioned  that  many 
of  the  stems  have  upon 
their  course  one  or  more 
of  the  small  ' '  inter- 
calated ' '  lingual  nodes 
(page  9.48).  Special 
importance,  however, 
attaches  to  that  supe- 
rior deep  cervical  node 
already  mentioned  as 
occurring  at  about  the 
level  of  the  bifurcation 
of  the  common  carotid 
artery,  on  account  of 
the  numerous  afferents 
it  receives  from  the 
tongue. 

The  lymphatics  of 
the  floor  of  the  mouth 
have  essentially  the  same 
terminations  as  those  of 
the  tongue.  The  stems 
which  arise  from  its 
anterior  half  pass  with 
the  stems  from  the  tip 
of  the  tongue  to  the  inferior  deep  cervical  nodes,  while  from  its  entire  surface  stems 
pass  to  the  submaxillary  and  superior  deep  cervical  nodes. 

The  Palate,  Pharynx,  and  Tonsils. — The  lymphatics  of  the  hard  palate  form 
a  fine  net-work  in  the  superficial  portions  of  the  mucous  membrane  and  are  continuous 
laterally  with  those  of  the  upper  gum.  They  empty  into  several  stems  which  pass 
backward  in  the  median  line  of  the  palate  and  at  about  the  level  of  the  last  molar 
teeth  bend  outward  to  the  right  and  left,  and,  passing  in  front  of  the  anterior  pillars 
of  the  fauces,  pierce  the  superior  constrictor  of  the  pharynx  to  terminate  in  those 
superior  deep  cervical  nodes  which  are  situated  on  the  internal  jugular  vein  above  the 
level  at  which  it  is  crossed  by  the  posterior  belly  of  the  digastric  muscle. 

The  net-work  of  the  soft  palate  is  exceedingly  close  and  especially  so  in  the 
uvula,  which  in  a  successful  injection  of  the  lymphatics  may  treble  its  volume,  be- 
coming exceedingly  turgid  (Sappey).  Stems  emerging  from  the  net-work  pass 
toward  both  surfaces  of  the  palate,  those  lying  below  the  upper  surface  passing  back- 
ward and  outward  to  join  the  stems  from  the  nasal  mucous  membrane  just  below 
the  orifice  of  the  Eustachian  tube,  whence  their  course  is  similar  to  that  of  the  nasal 
stems.  Some  of  them  pass  upward  and  backward  to  perforate  the  superior  con- 
strictor of  the  pharynx  and  terminate  in  the  lateral  retropharyngeal  nodes,  while 
others  descend  beneath  the  mucous  membrane  covering  the  posterior  pillars  of  the 
fauces  and,  after  perforating  the  superior  constrictor,  terminate  in  the  upper  nodes 
of  the  superior  deep  cervical  group. 


Lymphatics  of  tongue.     {Pu 


*  Gazette  hebdomadaire,  1902. 


THE    LYMPHATICS    OF    THE    HEAD.  955 

The  lymphatics  of  the  tonsil,  which  resemble  those  of  the  soft  palate  in  their 
abundance,  pass  with  the  stems  from  the  basal  region  of  the  tongue  to  the  superior 
deep  cervical  nodes. 

Those  of  the  pharynx  are  also  abundant,  especially  above  (Fig.  799).  The 
stems  which  arise  from  the  roof  and  upper  part  pass  principally  to  the  retro- 
pharyngeal nodes,  although  some  reach  the  superior  deep  cervical  nodes  directly  by 
following  the  course  of  the  ganglionated  cord.  The  stems  which  have  their  origin 
in  the  lower  part  of  the  pharyngeal  net-work  pass  downward  toward  the  larynx 
and  unite  with  its  vessels  to  be  distributed  to  the  superior  deep  cervical  nodes  as  far 
down  as  opposite  the  level  of  the  second  or  third  tracheal  ring. 

Practical  Considerations. —  The  Lymph-Nodes  of  the  Head. — The  lymphatics 
of  the  scalp  pass  from  the  plexus  of  fine  radicles  on  the  vertex  into  the  suboccipital 
(occipital),  mastoid  (postauricular),  parotid  (preauricular),  and  superficial  cervical 
nodes,  and  a  few — from  the  frontal  region — into  the  submaxillary  node,  into  one  or 
the  other  of  which  infection  may  be  carried  from  any  portion  of  the  scalp. 

The  suboccipital  nodes — one  to  three  on  each  side — lie  on  a  line  drawn  from  the 
junction  of  the  upper  and  middle  thirds  of  the  ear  to  the  inion  and  about  two  inches 
external  to  that  point.  They  are  often  enlarged  as  a  result  of  wounds  or  irritation 
of  the  occipital  and  postauricular  portion  of  the  scalp  and — especially  in  neglected 
children — as  a  consequence  of  eczema  affecting  the  skin  back  of  the  ear.  The  close 
relation  of  the  node  to  the  great  occipital  nerve,  on  which  it  usually  lies,  gives  rise 
to  marked  tenderness  on  pressure,  the  nerve  being  compressed  between  the  node 
and  the  bone.  The  source  of  infection  of  these  nodes  may  be  intracranial — e.g. , 
suppurative  meningitis  of  the  cerebellar  fossa  (Macewen). 

The  posterior  auricular  or  mastoid node,  found  directly  over  the  mastoid  insertion 
of  the  sterno-cleido-mastoid,  is  likewise  usually  infected  from  the  same  scalp  region. 
It  may  also  be  involved  alone  or  together  with  the  suboccipital  and  deep  cervical 
nodes  in  localized  tuberculous  mastoiditis  or  even  in  tuberculous  otitis  media. 

The  parotid  nodes,  lying  both  in  and  upon  the  gland,  receive  lymph  from  and 
consequently  may  be  infected  by  lesions  of  the  scalp,  the  outer  portion  of  the  lids, 
the  orbit,  the  cheeks,  the  nasal  fossae,  the  naso-pharynx,  the  external  auditory 
meatus,  the  tympanum,  or  the  temporo-mandibular  joint.  Chronic  enlargement  of 
these  nodes,  especially  of  the  deeper  ones  in  the  substance  of  the  gland  and  beneath 
the  parotid  capsule,  may  lead  to  a  mistaken  diagnosis  of  parotid  tumor.  Suppura- 
tive inflammation  of  these  deeper  nodes  gives  rise  to  a  true  parotid  abscess,  which,  on 
account  of  the  resistance  of  the  strong  parotid  fascia,  will  be  under  great  tension. 
Sloughing  of  the  parotid  tissue  may  occur.  There  will  be  shooting  pains  in  the 
head,  neck,  and  ear,  from  pressure  on  the  branches  of  the  trigeminus  accompanying 
the  facial,  or  on  the  auriculo-temporal  and  great  auricular  nerves.  The  contiguity  of 
the  temporo-mandibular  joint — into  which  the  abscess  may  open — makes  movement 
of  the  lower  jaw  painful.  The  relative  weakness  of  the  capsule  anteriorly  and  on  its 
inner  aspect  causes  the  pus  to  travel  forward  towards  the  cheek,  or  inward  towards 
the  pharynx,  following  sometimes  the  pharyngeal  process  of  the  parotid  and  giving 
rise  to  a  retropharyngeal  abscess.  Gravity  and  the  cervical  process  of  the  parotid 
may  conduct  the  pus  into  the  neck. 

The  lymphatics  of  the  face  empty,  the  superficial  set — accompanying  the  facial 
vein  —into  the  parotid  and  submaxillary  nodes  ;  the  deep  set,  with  some  of  those  of 
the  orbit,  palate,  nasal  fossae,  and  upper  jaw,  are  said  to  end  in  the  internal  maxil- 
lary nodes  situated  at  the  sides  of  the  pharynx  anteriorly.  According  to  Leaf,  these 
are  only  exceptionally  present.  Their  involvement  in  infections  spreading  from  the 
above  regions  may  give  rise  to  "  latero-pharyngeal  abscess,"  causing  a  swelling 
externally  behind  the  angle  of  the  mandible,  and  an  inward  projection  of  the  pharyn- 
geal wall  posterior  to  the  tonsil.  The  proximity  of  the  internal  carotid  should  be 
remembered,  and  the  fact  that  an  aneurism  of  that  vessel  has  been  opened  under  the 
impression  that  it  was  an  abscess  of  this  variety  (page  747). 

Some  lymphatics  from  the  chin  and  the  mid-portion  of  the  lower  lip  empty  into 
the  suprahyoid  (submental)  nodes  lying  on  the  mylo-hyoid  between  the  two 
anterior  bellies  of  the  digastrics.      Enlargement  of  these  nodes  may  be  distinguished 


956  HUMAN    ANATOMY. 

from  a  bursal  tumor  (thyro-hyoid)  by  the  fact  that  the  former  is  above,  the  latter 
below,  the  hyoid  bone. 

Enlargement  of  a  submaxillary  ?iode,  as  of  a  parotid  node,  may,  particularly 
if  it  lies  within  the  sheath  of  the  gland,  be  mistaken  for  a  growth  of  the  gland  itself. 
The  latter — as  compared  with  the  parotid — is,  however,  much  less  closely  and  firmly 
enveloped  by  its  capsule,  is  more  superficial,  and  is  not  in  near  relation  to  such 
important  structures.  On  the  other  hand,  the  wide  area  which  drains  into  the  sub- 
maxillary nodes — the  middle  of  the  forehead  and  of  the  face,  the  inner  portions  of 
the  lids,  the  mouth,  pharynx,  anterior  portion  of  the  tongue,  gums  and  teeth  of  the 
lower  jaw — renders  them  especially  liable  to  pyogenic  or  tuberculous  or  syphilitic 
infection,  or  to  secondary  involvement  in  carcinoma  of  any  of  these  regions — espe- 
cially of  the  tongue  or  lower  lip.  In  examining  for  enlargement  of  these  nodes,  the 
chin  should  be  lowered  so  as  to  relax  the  depressors  of  the  lower  jaw  and  the  deep 
cervical  fascia  and  permit  of  more  accurate  palpation  of  the  region.  When  these 
submaxillary  nodes  require  removal  for  infectious  or  malignant  disease,  the  salivary 
gland  is  often  involved  and  must  be  removed  with  them.  On  account  of  its  accessi- 
bility and  the  laxity  of  its  capsular  connections,  enucleation  of  this  gland  is  easily 
accomplished.  The  relation  of  the  facial  artery  lying  close  to  the  upper  part  of  its 
deep  aspect — which  it  grooves — before  crossing  the  jaw  in  front  of  the  masseter 
muscle  should  be  remembered. 

The  efferent  vessels  from  all  these  nodes— suboccipital,  mastoid,  parotid,  and 
submaxillary — enter  into  the  superficial  cervical  nodes,  the  efferent  vessels  from 
which,  in  their  turn,  enter  the  deep  cervical  nodes  (page  957).  Extracranial  lesions 
of  an  irritative  kind  will  thus  first  show  themselves  in  enlargement  of  the  first 
mentioned  groups  ;  if  the  irritation  is  continued,  the  superficial  cervical  nodes  will 
enlarge  ;  and  if  it  persists  and  is  sufficiently  severe,  the  deep  cervical  will  also 
participate  in  the  enlargement  (Macewen).  As  the  intracranial  lymph-paths,  having 
their  origin  in  the  cerebral  pia  mater  and  the  choroid  plexuses  of  the  ventricles, 
pass  out  of  the  skull  in  company  with  the  internal  carotid  and  vertebral  arteries  and, 
lower,  the  internal  jugular  vein  and  empty  into  the  deep  cervical  nodes,  these  latter 
are,  theoretically,  first  affected  by  intracranial  irritation.  As  they  lie  beneath  the 
cervical  fascia,  their  enlargement  may  not  be  early  noticed.  These  variations  in  the 
seat  of  glandular  swelling  cannot,  however,  be  relied  upon  as  a  basis  for  a  positive 
differential  diagnosis  between  intracranial  and  more  superficial  (extracranial)  sources 
of  irritation  or  infection. 

THE    LYMPHATICS    OF    THE    NECK. 
The  Lymph-Nodes. 

The  principal  group  of  nodes  in  the  neck  region  is  that  which  is  situated  along 
the  course  of  the  internal  jugular  vein,  forming  the  jugular  plexus  (plexus  jugularis). 
It  consists  of  a  variable,  but  usually  large,  number  of  nodes  and  is  interposed  in  the 
pathway  followed  by  the  entire  lymphatic  system  of  the  head  and  neck.  It  is  prac- 
tically a  continuous  chain  of  nodes,  extending  the  entire  length  of  the  neck,  but  for 
convenience  in  description  it  is  convenient  to  regard  the  nodes  as  forming  two  sub- 
groups which  are  named  the  superior  and  inferior  deep  ce?'vical  nodes.  In  addition 
to  these  some  smaller  groups  occur  more  superficially,  forming  what  are  termed  the 
superficial  cervical  nodes,  so  that  altogether  there  are  three  main  groups  of  nodes  in 
the  cervical  region. 

The  superficial  cervical  nodes  (lymphoglandulae  cervicales  superficiales) 
may  conveniently  be  divided  into  two  subgroups,  both  of  which  are  composed 
of  rather  small  and  somewhat  inconstant  nodes.  The  external  jugular  nodes,  as 
their  name  indicates,  are  situated  along  the  course  of  the  external  jugular  vein, 
and  consequentlv  rest  upon  the  outer  surface  of  the  sterno-cleido-mastoid  muscle. 
They  occur  a  little  below  the  lower  extremity  of  the  parotid  gland  (Fig.  796), 
and  are  usually  two  or  three  in  number,  one  or  two  additional  nodes  sometimes 
being  present  at  a  somewhat  lower  level.  They  receive  afferents  from  the  pinna 
of  the  ear  and  from  the  parotid  region,  and  their  efferents  pass  over  the  anterior 
border  of  the  sterno-cleido-mastoid  to  open  into  the  superior  deep  cervical  nodes. 


THE    LYMPHATICS    OF   THE    NECK. 


957 


Anterior  cervical 


tial  nodes  and  lyr 
(Most.*) 


The  second  subgroup  is  that  of  the  anterior  cervical  nodes,  which  are  both  variable 

and  inconstant  and  are  situated  beneath 

the    depressor    muscles    of    the    hyoid 

bone,  resting  upon  the  anterior  surface 

of  the  larynx  and  on  the  anterior  and 

lateral  surfaces  of  the  trachea.     Those 

which  rest  upon  the  trachea  are  some- 
what more  constant  than  the  others,  but 

like   them  they  are   usually  small    and 

are  therefore  likely  to  be  overlooked  in 

normal    conditions.      The   more    lateral 

members  of  the  series,  from  three  to  six 

in    number,    are    arranged    in    a    chain 

which  follows  the  course  of  the  recurrent 

(inferior)  laryngeal  nerve  and  are  some- 
times   spoken    of    as    the    recnrre7itial 

nodes.       The    anterior    cervical    nodes 

receive  afferents   from  the    larynx   and 

trachea,  and  their  efferents  pass  to  the 

lower  superior  deep  cervical  nodes. 

The     superior    deep     cervical 

nodes  (lyraphoglandulae  cervicales  pro- 

fuudae    superiores)    vary   from    ten    to 

sixteen  in   number,   and    extend   along 

the  course  of  the  internal  jugular  vein 

from  the  tip  of  the  mastoid  process  to 

the  level  at  which  the   vein  is  crossed 

by    the    omo-hyoid   muscle.      They  lie 

either  directly  upon  the  vein  or  slightly  posterior  to  it,  beneath  the  sterno-cleido- 

mastoid  muscle,   and  are 
Fig.  807.  all    united    by    numerous 

connecting  stems  so  that 
they  form  a  veritable 
plexus.  Some  of  the 
nodes  are  exceedingly 
Constant  in  position,  one, 
especially,  which  receives 
numerous  afferents  from 
the  lingual  region  and  has 
therefore  been  termed  the 
principal  node  of  the 
tongue,  occurring  at  about 
the  level  of  the  bifurcation 
of  the  common  carotid 
artery,  and  a  second  is 
situated  just  above  the 
omo-hyoid  muscle.  The 
afferents  of  the  group  are 
very  numerous,  and  may 
be  divided  into  two  classes 
according  as  they  take 
their  origin  in  nodes 
belonging  to  other  groups 
or  come  directly  from 
the  lymphatic  net-works. 
Belonging  to  the  first 
class    and   terminating  in 

the  more   posterior  nodes   are   the    efferent  stems   for  the   posterior  auricular  and 
*Anatom.  Anzeiger,  Bd.  xv.,  1S99. 


Deep  cervical  lymph-nodes 


958  HUMAN    ANATOMY. 

occipital  nodes,  while  in  the  more  anterior  nodes  efferents  from  the  retropharyn- 
geal, parotid,  submaxillary,  submental,  and  superficial  cervical  nodes  terminate. 

Belonging  to  the  second  class  and  terminating  in  the  more  posterior  nodes  are 
(i)  a  vessel  which  descends  directly  from  the  occipital  region  of  the  scalp  ;  (2)  some 
stems  from  the  posterior  surface  of  the  pinna  ;  and  (3)  stems  from  the  upper  part 
of  the  back  of  the  neck.  To  the  more  anterior  nodes  pass  ( 1 )  the  majority  of  the 
stems  descending  from  the  tongue  ;  (2)  stems  from  the  nasal  mucous  membrane, 
the  palate,  and  the  upper  portions  of  the  pharynx  ;  (3)  stems  from  the  cervical 
portion  of  the  oesophagus  ;  (4)  the  majority  of  the  stems  from  the  larynx  and  those 
which  come  from  the  cervical  portion  of  the  trachea,  and  (5)  the  stems  from  the 
thyroid  gland. 

The  efferents  from  the  lower  nodes  of  the  plexus  pass  partly  to  the  inferior  deep 
cervical  nodes,  and  partly  unite  with  the  efferents  of  these  to  form  the  jugular  trunk, 
which  is  described  below. 

The  inferior  deep  cervical  nodes  (lymphoglandulae  cervicales  profundae 
inferiores),  also  termed  the  supraclavicular  nodes,  occupy  the  supraclavicular  triangle 
of  the  neck,  resting  upon  the  scalene  muscles  and  upon  the  trunks  of  the  brachial 
plexus.  They  are  fewer  in  number  and,  as  a  rule,  smaller  than  the  superior  deep 
cervical  nodes.  In  addition  to  the  affere7its  from  the  superior  nodes  they  receive  (1) 
a  stem  which  passes  directly  downward  from  the  occipital  region  of  the  scalp  along 
the  posterior  border  of  the  sterno-cleido-mastoid  muscle  ;  (2)  vessels  from  the 
integument  and  muscles  of  the  lower  portion  of  the  neck  ;  (3)  vessels  from  the 
integument  of  the  upper  portion  of  the  pectoral  region  ;  (4)  occasionally  some 
vessels  from  the  arm  which  follow  the  course  of  the  cephalic  vein  ;  (5)  some  efferents 
from  the  brachial  groups  of  the  axillary  nodes  ;  and  (6)  vessels  which  pass  to  the 
lower  nodes  of  the  left,  rarely  the  right,  side  from  the  liver,  ascending  in  the 
suspensory  ligament  of  that  organ,  piercing  the  diaphragm,  and  following  the  course 
of  the  internal  mammary  vessels  upward  through  the  thorax. 

Their  efferents  unite  with  some  of  those  from  the  superior  deep  cervical  nodes  to 
form  a  single  stem,  the  jugular  trunk  (truncus  jugularis),  which  on  the  left  side 
opens  into  the  arch  of  the  thoracic  duct  and  on  the  right  unites  with  the  subclavian 
trunk  to  form  the  right  lymphatic  duct.  Both  the  right  and  the  left  trunks,  how- 
ever, frequently  open  directly  into  the  subclavian  vein. 

The  Lymphatic  Vessels. 

The  Integument  and  Muscles  of  the  Neck. — The  lymphatic  stems  arising 
from  the  subcutaneous  and  muscular  net-works  of  the  neck  open  into  the  posterior 
nodes  of  the  superior  deep  cervical  chain. 

The  Larynx  and  Trachea. — The  lymphatic  net-work  of  the  larynx  is  very 
well  developed  over  the  greater  portion  of  the  mucous  membrane  and  is  especially 
rich  in  the  regions  of  the  false  vocal  cords  and  the  ventricles.  Over  the  true  vocal 
cords,  however,  it  is  very  feebly  developed,  and  the  entire  net-work  may  therefore  be 
regarded  as  consisting  of  two  portions,  one  of  which  is  situated  above  the  level  of  the 
true  cords  and  the  other  below  them.  The  two  portions  are  not,  it  is  true,  perfectly 
distinct,  since  they  are  connected  by  the  feeble  net-work  of  the  true  cords  ;  but  it  has 
not  been  found  possible  to  force  an  injection  from  one  portion  into  the  other  and, 
furthermore,  each  portion  gives  rise  to  a  special  set  of  efferent  stems. 

The  stems  which  arise  from  the  upper  net-work  are  from  three  to  six  in 
number  on  each  side,  and  make  their  exit  from  the  larynx  through  the  lateral 
portions  of  the  thyro-hyoid  membrane,  in  close  proximity  to  the  superior  laryngeal 
artery  (Fig.  806).  They  then  pass  outward  to  the  anterior  nodes  of  the  superior 
deep  cervical  chain,  some  opening  into  the  nodes  situated  in  the  neighborhood 
of  the  bifurcation  of  the  common  carotid  artery,  while  others,  bending  downward, 
terminate  in  lower  nodes. 

The  stems  from  the  lower  net-work  pass  in  two  directions  ;  a  few  small  ones 
perforate  the  crico-thyroid  membrane  near  the  median  line,  while  the  rest  are  directed 
posteriorly  and  make  their  exit  below  the  lower  border  of  the  cricoid  cartilage.  The 
anterior  stems  pass  partly  to  an  anterior  cervical  node  situated  usually  in  the  median 


THE   LYMPHATICS   OF   THE   NECK.  959 

line  between  the  two  crico-thyroid  muscles,  another  descends  over  the  isthmus  of 
the  thyroid  gland  to  terminate  in  one  of  the  nodes  which  rest  upon  the  anterior 
surface  of  the  trachea,  while  one  or  two  pass  outward  along  the  upper  border 
of  the  lobes  of  the  thyroid  gland  and  then  descend  to  terminate  in  one  of  the 
superior  deep  cervical  nodes  situated  about  opposite  the  middle  of  the  sterno-cleido- 
mastoid  muscle.  The  posterior  stems,  which  are  from  three  to  six  in  number,  after 
making  their  exit  from  the  larynx,  follow  the  course  of  the  recurrent  laryngeal 
nerves  and  terminate  in  the  recurrential  nodes  situated  in  the  course  of  those  nerves, 
some  of  the  stems  frequently  anastomosing  to  form  a  plexus  which  descends  along 
the  vagus  nerve  and  may  be  followed,  in  some  cases,  to  the  inferior  deep  cervical 
nodes. 

The  net-work  of  the  trachea  is  formed  of  delicate  and  slender  vessels  arranged  so 
as  to  form  elongated  meshes,  and  the  stems  which  arise  from  it  emerge  from  the 
lateral  surfaces  of  the  trachea,  passing  between  the  tracheal  cartilages.  Those  from 
the  upper  part  of  the  trachea  pass  to  the  recurrential  nodes,  while  the  lower  ones 
pass  to  the  bronchial  nodes  situated  in  the  neighborhood  of  the  bifurcation  of  the 
trachea. 

The  Thyroid  Gland. — The  lymphatic  stems  from  the  thyroid  gland  pass  for 
the  most  part  to  the  superior  deep  cervical  nodes,  following  the  course  of  the  superior 
thyroid  artery,  some  of  them,  however,  passing  at  first  directly  upward  and  coming 
into  relation  with  an  anterior  cervical  node  situated  upon  the  crico-thyroid 
membrane.  Those  which  arise  from  the  lower  border  of  the  isthmus  and  from  the 
neighboring  portions  of  the  lobes  are  directed  downward,  and  terminate  in  the 
anterior  cervical  nodes  which  are  situated  upon  the  anterior  surface  of  the  trachea 
and  in  the  recurrential  nodes. 

The  (Esophagus. — The  cervical  portion  of  the  oesophagus  will  be  considered 
together  with  its  thoracic  portion  (page  971). 

Practical  Considerations. —  The  Lymph- Nodes  of  the  Neck. — 1.  The  super- 
ficial cervical  nodes — not  invariably  present — are  found  over  the  sterno-mastoid, 
along  the  external  jugular  vein,  between  the  deep  fascia  and  the  platysma,  and  may 
be  enlarged  in  various  affections  of  the  external  ear  and  of  the  skin  of  the  face  and 
neck,  or  consecutively  to  infections  of  the  suboccipital  (occipital),  mastoid  (post- 
auricular),  parotid  (preauricular),  or  submaxillary  nodes.  Those  found  posteriorly 
near  the  anterior  border  of  the  trapezius  muscle  enlarge  early  in  the  secondary  stage 
'  of  syphilis  and,  on  account  of  their  accessibility  for  palpation,  are  then  of  diagnostic 
value.  2.  The  deep  cervical  nodes  are  divisible,  for  convenience,  into  two  groups  :  (a) 
an  upper  group,  situated  about  and  above  the  bifurcation  of  the  common  carotid  artery 
and  the  upper  part  of  the  internal  jugular  vein,  some  of  which  lie  partly  beneath  the 
posterior  edge  of  the  sterno-mastoid  and  partly  projecting  into  the  posterior  cervical 
triangle  ;  (5)  a  lower  group,  found  near  the  lower  portions  of  the  internal  jugular, 
external  jugular,  subclavian,  and  transverse  cervical  veins,  and  lying  almost  com- 
pletely beneath  the  sterno-mastoid.  At  the  root  of  the  neck  this  group  is  continuous 
externally  with  the  subclavian  and  axillary,  and  internally  with  the  mediastinal  nodes. 
All  these  deep  cervical  nodes  lie  in  or  beneath  the  deep  fascia  and  receive  the 
efferent  vessels  from  the  superficial  nodes  (and  thus  from  their  tributaries  mentioned 
above)  as  well  as  all  other  lymphatics  of  the  head  and  neck — retropharyngeal, 
suprahyoid,  etc. — that  do  not  directly  communicate  with  the  superficial  group. 

The  deep  cervical  nodes  are  accordingly  found  to  be  inflamed  or  enlarged 
consecutively  to  a  great  variety  of  conditions, — e.g.,  eczema,  wounds  or  ulcers  of 
any  portion  of  the  scalp  or  face,  dental  caries,  alveolo-dental  abscess,  pharyngeal 
or  buccal  or  tonsillar  inflammation  or  ulceration,  fissures  or  ulcers  or  carcinoma 
of  the  tongue,  otitis  (external  or  medial),  rhinitis,  hordeolum,  labial  herpes  or 
chancre  or  epithelioma.  They  may  also  be  enlarged — though  with  great  rarity — 
from  primary  carcinoma  and — less  rarely — from  lympho-sarcoma  or  from  Hodgkin's 
disease.  Furthermore,  various  intracranial  conditions  may  be  followed  by  involve- 
ment of  the  cervical  nodes,  both  superficial  and  deep.  In  most  cases  the  infection 
comes  from  the  same  side  of  the  head,  face,  or  neck,  as  the  enlarged  glands,  but 
occasionally  the  original  lesion  is  on  the  opposite  side. 


960  HUMAN    ANATOMY. 

Swellings  of  this  deep  chain  of  glands — especially  of  those  beneath  the  sterno- 
mastoid — may  be  present  without  being  distinctly  palpable,  and  are  apt,  in  any  case 
severe  enough  to  come  to  operation,  to  involve  many  more  nodes  than  were 
previously  suspected. 

One  node  of  the  upper  group  lies  behind  the  posterior  belly  of  the  digastric  in 
the  angle  between  the  internal  jugular  and  facial  veins.  Leaf  has  suggested  that 
it  be  called  the  "  jugulo-digastric"  node.  In  some  affections  of  the  tonsil  and  of 
the  base  of  the  tongue,  it  enlarges  and  projects  in  front  of  the  anterior  border  of  the 
sterno-mastoid,  its  contents  being  about  half  an  inch  below  and  somewhat  internal  to 
the  angle  of  the  jaw. 

Other  glands  of  this  group,  which  are  very  constant  in  position,  lie  over  the 
insertion  of  the  splenius  capitis  under  cover  of  the  upper  end  of  the  sterno-mastoid 
and  surround  the  spinal  accessory  nerve  before  it  perforates  the  latter  muscle.  En- 
largement of  these  glands  would  compress  the  nerve  against  the  transverse  process 
of  the  atlas  (Leaf). 

The  retropharyngeal  nodes  lie  in  the  space  of  that  name  (page  552),  about 
opposite  the  axis,  on  the  rectus  capitis  anticus  major  and  to  the  inner  side  of  the 
glosso-pharyngeal  nerve  where  it  curves  around  the  lower  border  of  the  stylo- 
pharyngeus.  They  communicate  with  the  upper  group  of  the  deep  nodes.  They 
may  be  enlarged  from  infection  through  the  overlying  mucosa,  as  they  are  in  close 
relation  to  the  buccal  portion  of  the  pharynx,  which,  on  account  of  its  many  crypts 
or  recesses,  the  large  amount  of  adenoid  tissue  present,  its  relatively  direct  exposure 
to  mechanical  injury  and  to  the  current  of  inspired  air  (drying  it,  reducing  its 
temperature,  and  possibly  conveying  microbic  irritants),  is  especially  susceptible  to 
inflammation.  They  may  also  enlarge  as  a  result  of  caries  of  the  bodies  of  the 
cervical  vertebrae.  In  either  case,  there  may  be  pharyngeal  and  tonsillar  pain,  ear- 
ache, and  other  evidence  of  glosso-pharyngeal  irritation.  If  suppuration  occurs,  a 
fluctuating  swelling  appears  which  pushes  the  posterior  wall  of  the  pharynx  forward 
(the  retropharyngeal  connective  tissue  being  lax  to  permit  of  the  free  movement  of 
the  pharynx  during  deglutition),  depresses  the  soft  palate,  and  causes  dysphagia  ; 
or,  if  lower,  causes  dysphonia  and  dyspncea  by  obstructing  the  laryngeal  opening. 
Such  an  abscess  may  gravitate  along  the  oesophagus  into  the  mediastinum  and  may 
even  reach  the  diaphragm  ;  or  it  may  extend  laterally  behind  the  parotid  and  great 
vessels  to  the  side  of  the  neck,  or,  reaching  the  cords  of  the  brachial  plexus,  may  be 
conducted  by  them  to  the  posterior  cervical  triangle  or  down  into  the  axilla.  Such 
an  abscess  should  not  be  left  to  spontaneous  evacuation,  on  account  of  the  danger' 
of  its  extension  in  these  directions,  or — if  the  abscess  should  suddenly  burst  into  the 
pharynx — of  suffocation  or  of  septic  pneumonia  if  the  pus  entered  the  air-passages. 
It  may  be  opened  through  the  mouth,  in  the  mid-line  of  the  pharynx  (the  head 
being  bent  over  so  that  the  pus  would  not  run  toward  the  glottis),  or  externally  by 
an  incision  along  the  posterior  margin  of  the  sterno-mastoid,  the  great  vessels  being 
pushed  forward  as  the  wound  is  deepened. 

The  lower  group  of  deep  cervical  nodes  enlarge  most  frequently  consecutively 
to  infection  or  disease  of  the  upper  group.  They  also  receive  the  lymphatics  from 
the  supraspinous  fossa  which  follow  the  suprascapular  artery,  and  those  from  the 
upper  part  of  the  deltoid.  Those  that  lie  at  the  very  base  of  the  neck,  in  the  sub- 
clavian triangle,  or  on  the  omo-hyoid  muscle,  are  not  uncommonly  affected  in  the  latter 
stages  of  mammary  carcinoma  (page  2035).  They  are  continuous  with  the  axillary 
nodes,  while  those  to  their  inner  side — lying  on  the  levator  anguli  scapulae  and 
scalenus  medius  just  external  to  the  internal  jugular  vein — are  also  often  involved  in 
the  upward  extension  of  cancer.  Both  sets  communicate  with  the  mediastinal  nodes. 
On  the  left  side  they  are  in  close  proximity  to  the  thoracic  duct.  The  branches  of 
the  cervical  plexus  pass  among  the  nodes  of  this  deep  cervical  group. 

In  cases  of  chronic  inflammation  and  enlargement  of  these  nodes  they  will  usually 
be  found  adherent  to  the  internal  jugular  vein,  which  is  in  close  relation  to  most  of 
them.  As  the  majority  of  them  lie  beneath  the  sterno-cleido-mastoid,  that  muscle 
will  often  have  to  be  divided  either  partially  or  completely  in  operations  for  their 
removal.  Certain  cysts,  in  most  cases  congenital,  usually  subcutaneous  but  with  deep 
prolongations  into  the  intermuscular  spaces,  are  found  in  the  neck,  and  are  believed 


THE    LYMPHATICS    OF    THE    UPPER    EXTREMITY.  961 

to  be  of  lymphatic  origin,  because  (a)  they  are  often  associated,  and  sometimes 
anatomically  connected  with  other  congenital  defects  of  the  lymphatic  system, 
such  as  macroglossia  (cavernous  lymphangioma  of  the  tongue)  and  macrocheilia 
(labial  lymphangioma)  ;  and  (6)  they  are  in  communication  with  the  lymphatic 
trunks  (Rolleston). 

THE  LYMPHATICS  OF  THE  UPPER  EXTREMITY. 
The  Lymphatic  Nodes. 

The  lymphatic  nodes  of  the  arm  are  for  the  most  part  confined  to  its  upper 
portions,  the  principal  group  occurring  in  the  axilla  and  consisting  of  a  considerable 
number  of  nodes  united  by  connecting  stems  to  form  a  plexus  axillaris.  A  few 
scattered  nodes  also  occur  in  the  brachial  region  and  some  are  occasionally  to  be 
found  in  the  antibrachium,  but  they  are  entirely  lacking  in  the  hand.  An  especial 
interest  attaches  to  the  axillary  nodes  on  account  of  the  extensive  area  from  which 
they  receive  afferents,  for,  in  addition  to  almost  the  entire  lymphatic  drainage  of  the 
arm,  they  also  receive  the  vessels  from  the  anterior  and  lateral  thoracic  walls,  from 
the  mammary  gland,  and  from  the  scapular  region.  The  brachial  and  antibrachial 
nodes,  on  the  other  hand,  are  rather  to  be  regarded  as  "intercalated"  nodes  inter- 
posed in  the  course  of  certain  of  the  lymphatic  vessels  ;  some  of  them  lie  superficial 
to  the  deep  fascia,  while  others  are  situated  more  deeply  along  the  course  of  the 
principal  blood-vessels,  and,  consequently,  it  is  convenient  to  divide  them  into  two 
sets  according  as  they  are  superficial  or  deep. 

The  superficial  brachial  nodes  (lymphoglandulae  cubitales  superficiales)  are 
arranged  in  two  principal  groups.  One  of  these  rests  upon  the  brachial  fascia  imme- 
diately over  the  internal  condyle  of  the  humerus,  and  may  be  termed  the  epitrochlear 
group  (Fig.  809).  It  consists  of  from  one  to  four  nodes,  of  which  one,  the  lowest  of 
the  group,  is  especially  constant  and  is  termed  the  epitrochlear  node.  The  remaining 
nodes,  if  present,  are  situated  along  the  course  of  the  basilic  vein,  one  frequently 
lying  almost  in  the  median  line  of  the  arm  a  short  distance  above  the  bend  of  the 
elbow.  The  afferents  of  the  epitrochlear  nodes  are  the  superficial  vessels  of  the 
forearm  and  hand,  especially  those  which  pass  upward  along  the  ulnar  border  of 
the  forearm  ;  their  efferents  pass  upward  along  the  basilic  vein  and  join  the  deep 
vessels  where  the  basilic  vein  dips  down  to  join  the  brachial. 

A  second  group,  which  may  be  termed  the  delto-pectoral group ,  consists  of  from 
one  to  four  nodes  situated  along  the  course  of  the  cephalic  vein,  in  the  groove 
between  the  deltoid  muscle  and  the  clavicular  portion  of  the  pectoralis-  major 
(Fig.  809).  They  are  not  always  distinguishable  and  are  usually  quite  small. 
They  are  interposed  in  the  course  of  the  delto-pectoral  lymphatic  stem  which  passes 
upward  in  the  groove  and  opens  into  the  subclavicular  group  of  axillary  nodes 
or  occasionally  into  the  inferior  deep  cervical  nodes. 

The  deep  brachial  nodes  sometimes  include  some  small  nodes  occurring  on 
the  lymphatic  stems  which  accompany  the  ulnar  and  radial  blood-vessels,  but  these 
nodes  are  relatively  inconstant.  Of  more  frequent  occurrence  is  a  group  of  two 
or  three  small  nodes  (lymphoglandulae  cubitales  profundae)  which  occur  upon  the  stems 
accompanying  the  brachial  artery  and  are  situated  at  about  the  middle  part  of  its 
course.  Their  afferents  are  the  deep  lymphatics  of  the  forearm  and  their  efferents 
pass  upward  to  terminate  in  the  humeral  nodes  of  the  axillary  group. 

The  axillary  nodes,  which  are  embedded  in  the  areolar  tissue  occupying  the 
axillary  space,  vary  in  number  from  sixteen  to  thirty-six.  Some  of  them  are  usually 
of  considerable  size,  especially  in  those  cases  in  which  their  number  approaches  the 
lower  limit  mentioned,  for  it  is  a  general  rule  that  the  size  of  the  nodes  in  any  group  is 
inversely  proportional  to  their  number  ;  but  it  seems  probable  that  in  addition  to  those 
which  may  be  observed  macroscopically,  exceedingly  small  ones,  approaching  micro- 
scopic size,  also  occur,  and  that  these,  under  pathological  conditions  or  after  removal 
of  the  larger  ones,  may  increase  in  size  and  form  additional  or  new  foci  of  infection. 

Although  united  by  connecting  stems  to  form  a  plexus,  the  axillary  nodes  may 
be  divided,  according  to  their  position  and  the  source  from  which  their  afferents 
come,  into  a  number  of  more  or  less  distinct  subgroups  (Figs.  808,  814),  and  of 

61 


962 


HUMAN    ANATOMY. 


these,  four  are  terminals  for  lymphatic  stems  coming  from  the  arm  and  the  thoracic 
walls,  while  two  others  form  relays  between  these  terminal  nodes  and  the  subclavian 
trunk  by  which  the  lymph  from  the  entire  axillary  plexus  is  conveyed  to  the  right 
lymphatic  duct  or  to  the  arch  of  the  thoracic  duct. 

1.  The  brachial  subgroup  is  composed  of  a  number  of  usually  large  nodes, 
arranged  in  a  chain  along  the  axillary  vein,  for  the  most  part  along  its  inner  surface, 
although  a  node  is  to  be  found  behind  it,  between  it  and  the  subscapular  muscle. 
The  affere7its  of  this  group  come  from  the  arm  and  include  almost  the  entire  set 
of  collecting  stems  from  that  region,  only  one  of  them,  that  which  accompanies 
the  cephalic  vein,  passing  to  another  group.  Their  eff events  pass  partly  to  the 
intermediate  subgroup  of  the  axillary  plexus,  partly  to  the  subclavicular  subgroup, 
and  partly  to  the  lower  nodes  of  the  inferior  deep  cervical  group. 

2.  The  anterior  pectoral  subgroup  is  composed  of  two  or  three  usually  small 
nodes   situated   over   the   second   and  third   intercostal  spaces,   beneath   the  lower 

Fig.  S08. 


Brachial  plexus 
Subclavian  artery. 


Intermediate  nod 


Subclavicular  nod 


Mammary  gland 


Brachial  nodes 
Subscapular  nodes 
Anterior  pectoral  nodes 

Inferior  pectoral  nodes 


W        V  \ 

Axillary  lymph-nodes,  new-born  child.     {Oelsncr.*) 


border  of  the  pectoralis  major  muscle  and  anterior  to  the  long  thoracic  artery. 
They  receive  afferents  from  the  integument  of  the  anterior  surface  of  the  thorax, 
from  the  pectoral  muscles,  and  from  the  mammary  gland.  Their  efferents  pass 
partly  to  the  intermediate  and  partly  to  the  subclavicular  subgroup  of  the  axillary 
nodes. 

3.  The  inferior  pectoral  subgroup  is  composed  of  two  or  three  small  nodes, 
situated  either  upon  or  posterior  to  the  long  thoracic  artery  over  the  fourth  and  fifth 
intercostal  spaces  or  even  higher.  They  receive  their  afferents  mainly  from  the 
integument  of  the  lateral  wall  of  the  thorax  and  from  the  subjacent  muscles,  and 
their  efferents  pass  to  the  nodes  of  the  intermediate  subgroup. 

4.  The  subscapular  subgroup  (lymphoglandulae  subscapulars )  consists  of  a  chain 
of  six  or  more  nodes  situated  along  the  course  of  the  subscapular  artery,  and,  in 
addition,  includes  two  or  three  nodes  which  rest  upon  the  dorsal  surface  of  the 
scapula  in  the  groove  between  the  teres  major  and  minor  muscles.      The  afferents 


■  Archiv  f.  klin.  Chirurgie,  Bd.  lxiv.,  1901. 


THE    LYMPHATICS    OF    THE    UPPER    EXTREMITY. 


963 


come  from  the  integument  and  muscles  of  the  lower  part  of  the  neck,  from  the 
dorsal  surface  of  the  thorax,  and  from  the  scapular  region  ;  the  efferents  pass  mainly 
to  the  nodes  of  the  intermediate  subgroup. 

5.  The  intermediate  subgroup  consists  of  a  number  of  rather  large  nodes 
imbedded  in  the  adipose  tissue  which  occupies  the  interval  between  the  lateral  wall 
of  the  thorax  and  the  upper  part  of  the  long  thoracic  vein  as  it  bends  outward  to 
open  into  the  terminal  part  of  the  axillary  vein.  It  receives  afferents  from  all  the 
terminal  subgroups  of  the  axillary  plexus,  and  its  efferents  pass  to  the  nodes  of  the 
subclavicular  subgroup. 

6.  The  subclavicular  subgroup  consists  of  from  six  to  twelve  nodes  situated 
near  the  apex  of  the  axillary  space,  partly  beneath  the  pectoralis  minor  and  partly 
above  the  upper  border  of  that  muscle.  They  constitute  the  final  link  in  the 
axillary  chain,  since  they  receive  as  afferents,  either  directly  or  indirectly  through  the 
intermediate  nodes,  the  efferents  from  all  the  other  subgroups.  Their  efferents  unite 
to  form  a  trunk  of  considerable  size,  the  subclavian  trunk  (truncus  subclavius), 
which,  from  its  origin  opposite  the  first  intercostal  space,  passes  almost  vertically 
upward  over  the  subclavian  vein  to  open  into  it  near  its  junction  with  the  external 
jugular,  or  else  to  unite  with  the  jugular  trunk  on  the  right  side  or  to  open  into  the 
arch  of  the  thoracic  duct  on  the  left  side.  In  addition  to  this  principal  termination 
one  or  more  of  the  subclavicular  efferents  usually  pass  to  one  of  the  lower  nodes  of 
the  inferior  deep  cervical  group. 

The  independent  termination  of  the  subclavian  trunk  in  the  subclavian  vein  is  probably  the 
most  frequent,  arrangement,  but  the  exact  position  of  its  junction  with  the  vein  is  variable.  Most 
frequently  it  empties  at  the  angle  formed  by  the  junction  of  the  subclavian  and  internal  jugular 
veins,  but  it  may  terminate  upon  the  superior  surface  of  the  subclavian  vein  some  distance  ( 1  cm. ) 
away  from  the  angle,  and  quite  frequently  it  opens  upon  the  anterior  surface  of  the  vein,  or,  in 
rarer  instances,  upon  its  posterior  surface.  Not  unfrequently  two  or  even  more  subclavian 
trunks  occur,  and  in  such  cases  one  may  unite  with  the  jugular  trunk,  or,  if  on  the  left  side,  open 
into  the  arch  of  the  thoracic  duct,  while  the  other  terminates  directly  in  the  vein. 


Fig.  Soq. 


The  Lymphatic  Vessels. 

The  lymphatic  vessels  of  the  upper  limb  are  divisible  into  two  groups  according 
as  they  lie  superficial  to  or  beneath  the  deep  fascia. 

The  superficial  vessels,  which  are  far  more  numerous  than  the  deep  ones,  have 
their  origin  in  the  subcutaneous  net-work  which  occurs  throughout 
the  entire  extent  of  the  limb,  but  is  especially  developed  upon  the 
palmar  surface  of  the  hand  and  upon  the  fingers  (Fig.  810).      The 
net-work  of  each  digit  tends  toward  its  sides  and  at  its  base  unites 
with  those  of  the  adjacent  digits  to  form  a  number  of 
stems  which  pass  upward  upon  the  dorsal  surface  of  the   Deito-peetorai 
hand,  for  the  most  part  over  the  intermetacarpal  spaces, 
although  abun- 
dant    anasto- 
moses    occur 
between      the 
vessels      of 
neighboring 
spaces  so  that 

an  open  dorsal  net-work  is  formed 
stems  which  arise  from  the  net-works  of  the 
inner  border  of  the  little  finger  and  of  the  outer  border  of  the 
index  also  pass  upward  upon  the  dorsum  of  the  hand,  lying 
respectively  toward  its  inner  and  outer  borders,  and  the  net- 
work of  the  thumb  is  drained  by  vessels  which  pass  upward 
on  its  dorsal  surface.  From  the  central  portion  of  the  palmar 
net-work  some  small  stems  pass  deeply,  penetrating  the 
palmar  aponeurosis  to  join  the  deep  lymphatic  vessels,  but 
its  remaining  portions  radiate  in  all  directions  to  join  the 
stems  of  the  dorsal  net-work.      Thus,  the  distal  portions  of  the  net-work  converge 


Superficial  lymphatic  vessels  of 
upper  limh:  semidiagrammatic. 
(Based  on  figures  of  Sappey.) 


964 


HUMAN    ANATOMY. 


toward  the  webs  of  the  fingers  and  pass  dorsally  to  join  the  stems  which  pass  upward 
over  the  intermetacarpal  spaces  ;  the  inner  portions  pass  over  into  a  number  of  small 
stems  which  curve  around  the  inner  border  of  the  hand  to  join  the  stems  coming  from 
the  little  finger  ;  the  outer  portions  similarly  empty  into  the  stems  coming  from  the 
outer  surface  of  the  index  finger  and  from  the  thumb  ;  while  the  proximal  portions 
give  rise  to  a  number  of  stems  which  pass  upward  along  the  anterior  surface  of  the 
forearm.  The  arrangement,  indeed,  is  very  similar  to  that  followed  by  the  veins. 
At  the  wrist,  then,  there  are  a  considerable  number  (about  thirty,  more  or  less) 
of  longitudinal  stems  which  are  arranged  in  two  groups,  one  of  which  is  dorsal  and 
the  other  ventral  (Figs.  810,  811).  The  former  consists  of  the  stems  which  drain 
the  digital  net-works  and  the  distal  and  lateral  portions  of  the  palmar  net-work, 
while  the  latter  is  formed  of  stems  arising  from  the  proximal  portion  of  the  palmar 
net-work.     As  they  ascend  the  arm   these  stems   receive  afferents  from   the  sub- 

Fig.  Sio.  Fig.  811. 


Lymphatics  of  hand  :  Fig.  Sio 
of  fingers  into  larger  stems  (£,  c),  which 
nicate  (Fig.  Sio,  *)  with  deeper  lymphati' 


,  Fig.  811,  dorsal  surface.  Superficial  digital  net-works  (c)  empty  at  bases 
re  tributary  to  trunks  on  forearm  (rf) ;  superficial  palmar  vessels  commu- 
i.     (Sappey.*) 


cutaneous  net-work  of  the  forearm,  and  at  the  same  time  anastomose  with  one 
another,  so  that  their  number  diminishes  gradually  as  they  ascend,  until,  at  about 
the  middle  of  the  brachium,  they  are  reduced  almost  to  half  the  original  number. 
As  they  approach  the  elbow  (Fig.  809),  the  stems  of  the  dorsal  group  divide  into 
two  sets,  which  curve  forward,  one  around  the  outer  border  and  the  other  around 
the  inner  border  of  the  forearm,  so  that  above  the  elbow  all  the  principal  stems  are 
situated  upon  the  anterior  (ventral)  surface  of  the  arm,  an  arrangement  which  again 
recalls  that  presented  by  the  veins. 

Just  above  the  bend  of  the  elbow  one  or  two  of  the  inner  stems  pass  into  the 
epitrochlear  nodes  (Fig.  809),  whose  efferents  pierce  the  brachial  fascia  to  empty 
into  the  deep  brachial  lymphatics,  but  the  majority  of  the  remaining  stems  pass 
directly  upward  along  the  anterior  surface  of  the  brachium  to  terminate  above  in 
the  brachial  nodes  of  the  axillary  plexus.  The  most  external  stem  follows,  however, 
a  different  course  (Fig.  809),  accompanying  the  cephalic  vein  along  the  groove 
between  the  deltoid  and  pectoralis  major  muscles  ;  after  traversing  the  delto-pectoral 


:  Description  et  iconographie  des  vaisseaux  lymphatiques,  1874. 


THE    LYMPHATICS    OF    THE    UPPER    EXTREMITY.  965 

nodes  it  perforates  the  costo-coracoid  membrane  and  terminates  in  one  of  the 
subclavicular  nodes  or,  more  rarely,  follows  the  course  of  the  jugulo-cephalic  vein 
over  the  clavicle  and  terminates  in  one  of  the  lower  inferior  deep  cervical  nodes. 
From  the  net-work  of  the  posterior  surface  of  the  brachium  a  number  of  small  stems 
arise  and  pass  obliquely  upward,  those  lying  towards  the  outer  border  of  the  arm 
curving  around  it  to  join  the  outer  main  stems,  while  the  inner  ones  partly  join  the 
inner  main  stems  and  partly  terminate  in  the  subscapular  nodes  along  with  the  vessels 
from  the  posterior  surface  of  the  shoulder. 

The  deep  lymphatics  of  the  arm  are  much  less  numerous  than  the  super- 
ficial ones  and  follow  the  courses  of  the  main  blood-vessels,  usually  corresponding  in 
number  with  the  vena?  comites.  They  occur  in  company  with  the  radial,  ulnar, 
anterior  and  posterior  interosseous,  and  brachial  vessels. 

The  radial  lymphatics  are  formed  by  the  union  of  two  stems,  one  of  which  follows 
the  course  of  the  main  stem  of  the  artery  from  the  deep  palmar  arch,  while  the  other 
accompanies  the  superficial  volar  artery  from  the  superficial  arch.  They  come 
together,  usually  a  short  distance  above  the  wrist-joint,  to  form  two  stems  which  pass 
upward  along  the  artery  and  may  traverse  one  or  two  small  and  inconstant  nodes. 
They  terminate  by  uniting  with  the  ulnar  stems  to  form  the  brachial  lymphatics. 

The  ulnar  lymphatics  are  also  formed  by  the  union  of  two  stems,  which 
accompany  the  deep  and  superficial  branches  of  the  ulnar  artery.  They  accompany 
the  ulnar  artery  up  the  forearm,  occasionally  traversing  one  or  two  small  nodes,  and, 
near  their  union  with  the  radial  stems  below  the  bend  of  the  elbow,  they  receive  the 
stems  which  accompany  the  anterior  and  posterior  interosseous  arteries. 

The  brachial  lymphatics  are  two  in  number  and  are  formed  by  the  union  of  the 
radial  and  ulnar  stems.  They  accompany  the  brachial  artery,  traversing  three  or 
four  nodes  in  their  course  and  receiving  the  efferents  of  the  epitrochlear  nodes,  or, 
these  failing,  the  inner  stems  of  the  forearm.  They  terminate  in  the  brachial  nodes 
of  the  axillary  plexus,  especially  in  one  which  usually  lies  between  the  axillary  vein 
and  the  subscapular  muscle. 

Practical  Considerations. —  The  Lymph-Nodes  of  the  Axilla  and  Upper 
Extremity. — The  palm  has  relatively  few  large  lymphatics  (as  it  has  few  superficial 
nerves  and  blood-vessels)  ;  hence  wounds  of  the  fingers  or  of  the  dorsum  of  the 
hand,  where  the  lymphatics  are  of  larger  size,  are  more  commonly  followed  by 
lymphangitis  than  are  wounds  of  the  palm.  Nodes  are  occasionally  found  along  the 
course  of  the  arteries  of  the  forearm  and  arm,  but  are  inconstant  and  not  of  great 
practical  importance.  One  or  two  beneath  the  deep  fascia  on  the  flexor  surface  of 
the  elbow  and  on  a  level  with  the  internal  condyle  or  an  inch  or  two  above  it,  are  less 
variable  and  are  sometimes  palpably  enlarged  in  syphilis  at  the  time  of  the  early 
general  adenopathy. 

The  axillary  nodes  will  be  almost  sufficiently  described  in  relation  to  the 
subject  of  mammary  cancer  (page  2035).  Further  reference  to  them  will  be  found  in 
the  description  of  the  axilla  (page  581). 

These  nodes  may  be  the  primary  seat  of  lympho-sarcoma,  may  be  the  subject  of 
tuberculous  or  syphilitic  enlargement,  and  are  constantly  infected  after  septic  wounds 
of  the  hand,  forearm,  or  arm,  and  less  frequently  from  wounds  in  the  remaining 
areas  which  drain  into  them,  viz.,  the  cervical  region  over  the  trapezius  muscle,  the 
dorsal  region,  the  lumbar  region  as  far  down  as  the  level  of  the  iliac  crest,  the 
abdominal  region  above  the  umbilicus,  and  the  front  and  sides  of  the  thoracic  region. 
Their  progressive  enlargement  widens  the  a-xilla,  renders  it  more  shallow  by  pushing 
its  floor  downward,  makes  the  anterior  fold  prominent,  and  increases  the  space 
between  the  outer  border  of  the  scapula  and  the  thoracic  wall.  Axillary  abscess 
commonly  originates  in  these  nodes,  consecutively  to  sepsis  elsewhere,  as  in  the 
regions  mentioned,  or  after  shoulder-joint  suppuration,  or  mammary  infection,  or 
caries  of  an  upper  rib.  Such  an  abscess  will  produce  rapidly  the  same  phenomena  as 
those  caused  by  a  growth.  It  may  make  its  way  behind  the  clavicle  into  the  supra- 
clavicular fossa  by  following  the  cords  of  the  brachial  plexus,  or  may  gravitate  down 
the  arm  along  the  course  of  the  vessels.  It  cannot  come  directly  forward  on  account 
of  the  pectoral  muscles  and  clavi-pectoral  fascia,  or  downward  on  account  of  the 


966 


HUMAN    ANATOMY. 


axillary  fascia,  or  backward  by  reason  of  the  attachment  of  the  serratus  magnus  to  the 
scapula,  or  outward  or  inward  because  of  the  upper  limb  and  the  wall  of  the  thorax. 
It  should  be  opened  half  way  between  the  anterior  and  posterior  folds  near  the 
inner  or  thoracic  wall. 


THE  LYMPHATICS  OF  THE  THORAX. 

The  Lymph-Nodes. 

Certain  of  the  nodes  which  have  been  described  as  belonging  to  the  axillary 
plexus,  namely,  those  forming  the  anterior  and  inferior  pectoral  subgroups,  might 
well  be  considered  as  belonging  to  the  thoracic  set,  since  their  afferents  drain  the 
anterior  and  lateral  walls  of  the  thorax.  On  account  of  their  situation,  however,  as 
well  as  their  intimate  connection  by  efferents  with  the  intermediate  and  subclavicular 
axillary  nodes,  they  are  more  conveniently  classed  with  the  axillary  set. 

The  remaining  thoracic  nodes  may  be  divided  into  two  sets  according  as  they 
occur  in  connection  with  the  thoracic  walls,  parietal  nodes,  or  with  the  viscera, 
visceral  nodes.      Of  the  parietal  nodes  there  are  two  principal  groups. 

The  sternal  or  internal  mammary  nodes  (lymphoglandulae  sternalesj  form 
two  chains  which  extend  upwards  upon  the  inner  surface  of  the  anterior  thoracic 
wall,  along  the  course  of  the  internal  mammary  blood-vessels  (Fig.  812).      They  vary 

in  number  from  four  to  ten, 
1  "'  and  are  situated  at  the  ante- 

rior or  -sternal  ends  of  three 
or  more  of  the  upper  inter- 
costal spaces,  resting  upon 
the  internal  intercostal  mus- 
cles and  being  covered,  so  far 
as  the  lower  members  of  the 
group  are  concerned,  by  slips 
of  the  triangularis  sterni. 
Their  afferents  come  from 
the  anterior  diaphragmatic 
nodes,  from  the  upper  por- 
tions of  the  rectus  abdominis, 
from  the  anterior  portions  of 
the  intercostal  muscles,  from 
the  integument  over  the  ster- 
num and  costal  cartilages, 
and,  to  a  certain  extent,  from 
the  mammary  glands.  Since 
the  nodes  are  arranged  in 
the  form  of  a  chain,  the  effer- 
ents from  the  lower  members 
of  the  series  are  afferents  for 
the  higher  ones;  the  terminal 
efferents  usually  unite  to  form 
a  single  stem  which  joins  the  efferents  of  the  anterior  mediastinal  and  bronchial  nodes 
to  form  the  broncho-mediastinal  trunk  (page  968). 

The  intercostal  nodes  (lymphoglandulae  intercostales )  are  situated  along  the 
courses  of  the  intercostal  arteries,  the  principal  and  most  constant  members  of  the 
series  being  situated  towards  the  posterior  extremities  of  the  intercostal  spaces. 
Some  nodes  which  occur  in  the  lateral  portions  of  the  spaces  are  inconstant  and 
always  small  ;  they  are  usually  situated,  when  present,  at  the  point  where  the 
intercostal  arteries  give  off  their  lateral  perforating  branches. 

The  afferents  of  the  intercostal  nodes  drain  the  posterior  portions  of  the  inter- 
costal spaces.  The  effej'ents  of  the  lower  members  of  the  series  unite  to  form  a  stem 
which  passes  downward  and  terminates  in  the  receptaculum  chyli,  while  those  from 


nph-nodes  of  anterior  thoracic  wall,  viewed  fr 
(Based  upon  figure  of  Poirier  and  Cuneo 


Poirier  et  Charpy  :   Traite  d'anatomie  humaine,  Tome  ii.,  1902. 


THE  LYMPHATICS  OF  THE  THORAX. 


967 


the  nodes  of  the  upper  spaces  are  directed  more  or  less  medially  to  open  into   the 
thoracic  duct. 

The  visceral  nodes  of  the  thorax  may  be  arranged  in  three  main  groups,  one 
consisting  of  the  nodes  situated  in  the  anterior  mediastinum,  a  second  of  those 
situated  in  the  posterior  mediastinum,  and  a  third  of  those  which  occur  in  the 
neighborhood  of  the  bifurcation  of  the  trachea  and  along  the  bronchi. 

The  anterior  mediastinal  nodes  ( lymphoglandulae  mediastinales  anterioresj 
are  arranged  in  two  groups,  one  of  which  occurs  in  the  lower  and  the  other  in  the 
upper  part  of  the  mediastinum.  The  nodes  of  the  lower  group,  termed  the  diaphrag- 
matic nodes,  are  from  three  to  four  in  number,  and  are  situated  upon  the  anterior 
part  of  the  upper  surface  of  the  diaphragm,  immediately  behind  the  xiphoid  process 
of  the  sternum  ;  their  afferents  come  from  the  diaphragm  and  from  the  upper  surface 
of  the  liver,  and  their  efferents  pass  to  the  lower  deep  cervical  nodes,  following  the 
course  of  the  internal  mammary  vessels. 

The  upper  group,  that  of  the  cardiac  nodes,  is  composed  of  from  eight  to  ten  nodes 
situated  upon  the  anterior  surfaces  of  the  arch  of  the  aorta  and  the  left  innominate  vein. 
They  receive  afferents  from  the  anterior  surface  of  the  pericardium  and  thymus  gland 
and  from  the  sternal  and  bronchial  nodes.  Their  efferents  pass  upward  and  unite  with 
those  from  the  bronchial  nodes  to  form  the  broncho-mediastinal  trunk  (page  968). 

The  posterior  mediastinal  nodes  (lymphoglandulae  mediastinales  posteriores), 
eight  to  twelve  in  number,  are  situated  along  the  thoracic  aorta  in  the  posterior 
mediastinum.  Their  afferents  come  from  the  cesophagus,  the  posterior  surface  of 
the  pericardium,  and  the  upper  surface  of  the  liver,  while  their  efferents  open  mainly 
into  the  thoracic  duct,  a  few  passing  to  the  bronchial  nodes. 

Two  or  three  small  nodes  which  may  be  regarded  as  belonging  to  this  group 
occur  upon  the  convex  surface  of  the  diaphragm  in  the  neighborhood  of  the  opening 
for  the  inferior  vena  cava.  They  receive  afferents  from  the  diaphragmatic  net-work 
and  also  from  the  superficial  net-work  of  the  upper  surface  of  the  liver. 

The  bronchial  nodes  (lymphoglandulae  bronchiales)  on  account  of  their  number 
and  size  are  the  most  im- 
portant of  the  thoracic 
nodes,  and  for  the  con- 
venience of  description 
they  may  be  regarded  as 
forming  three  subgroups 
(  Fig.  813).  One  of  these 
is  formed  by  the  tracheal 
nodes  ( lymphoglandulae 
tracheales),  seven  to  ten 
in  number  and  situated 
on  either  side  of  the 
lower  part  of  the  trachea. 
Those  upon  the  right 
side  are  as  a  rule  more 
numerous  and  larger  than 
those  on  the  left  side, 
varying  from  the  size  of 
a  pea  to  that  of  a  bean 
in  the  normal  condition. 
A  second  subgroup  is 
that  of  the  bronchial  nodes 
proper,  from  ten  to  twelve 
in  number  and  situated  in 
the  angle  formed  by  the 
two  bronchi.  They  are 
for  the  most  part  large, 
those  beneath  the   right   bronchus  being  usually  larger  and   more   numerous   than 


—  Tracheal  nodes 


Bronchial  node 


*  Clinique  m^dicale,  Tome  iv. 


968  HUMAN    ANATOMY. 

those  below  the  left  one.  The  third  subgroup  is  formed  by  the  pulmonary  nodes, 
usually  of  small  size  and  situated  in  the  hilus  of  the  lungs,  between  the  larger 
divisions  of  the  bronchi. 

The  afferents  of  the  bronchial  nodes  are  (i)  from  the  lungs,  (2)  from  the  lower 
part  of  the  trachea  and  from  the  bronchi,  (3)  from  the  heart,  and  (4)  from  the 
posterior  mediastinal  nodes.  Their  effere?its  may  either  pass  as  a  number  of  stems 
to  the  thoracic  duct  or  directly  to  the  subclavian  vein  on  the  right  side,  but  more 
frequently  they  unite  to  form  a  single  stem,  with  which  the  stems  coming  from  the 
sternal  and  anterior  mediastinal  nodes  unite  to  form  a  single  broncho-mediastinal 
trunk  (truncus  bronchomediastinalis),  which  passes  upward  toward  the  confluence 
of  the  internal  jugular  and  subclavian  veins.  It  either  opens  independently  into  the 
subclavian  vein,  which  is  the  most  usual  arrangement,  or  else,  on  the  right  side,  it 
unites  with  the  subclavian  and  jugular  trunks  to  form  the  right  lymphatic  duct  or,  on 
the  left  side,  it  unites  with  the  subclavian  trunk  to  open  into  the  arch  of  the  thoracic 
duct,  into  which  it  may  also  open  directly. 

The  Lymphatic  Vessels. 

The  cutaneous  lymphatics  of  the  thorax  form  a  rich  net-work  extending 
throughout  the  subcutaneous  tissue  and  being  continuous  above  with  the  subcutaneous 
net-work  of  the  cervical  region  and  below  with  that  of  the  abdomen.  From  the 
net-work  of  the  anterior  surface  a  considerable  number  of  stems  arise,  which  pass 
outward,  the  upper  ones  almost  horizontally  and  the  lower  ones  obliquely  upward 
and  outward,  to  terminate  in  the  anterior  pectoral  nodes  of  the  axillary  plexus 
(Fig.  814).  These  stems  form  the  principal  path  of  the  anterior  thoracic  drainage, 
but,  in  addition,  some  stems  which  arise  from  the  upper  portion  of  the  net-work 
pass  upward  over  the  clavicle  and  terminate  in  some  of  the  lower  inferior  deep 
cervical  nodes,  and  from  the  portions  of  the  net-work  near  the  median  line  short 
stems  perforate  the  intercostal  spaces  and  terminate  in  the  sternal  nodes.  Further- 
more, it  is  to  be  noted  that  the  net-works  of  either  side  are  continuous  across  the 
median  line  over  the  surface  of  the  sternum,  and  there  may  consequently  be  a  certain 
amount  of  crossing  in  the  lymph  flow,  that  coming  from  the  more  median  portions 
of  the  net-work  of  the  right  half  of  the  anterior  thoracic  wall,  for  instance, 
terminating  in  the  left  axillary  nodes.  These  decussating  paths  are,  however,  of 
comparatively  little  importance  except  in  cases  of  stoppage  of  the  normal  flow  to 
the  axillary  nodes  of  the  same  side,  and  in  such  cases  a  collateral  drainage  may 
also  be  established  for  the  lower  portion  of  the  thoracic  walls  through  the  abdominal 
lymphatics  to  the  inguinal  nodes. 

Upon  the  lateral  portions  of  the  thorax  the  net-work  gives  rise  to  some  half 
dozen  stems  which  pass  upwards  to  terminate  in  the  inferior  pectoral  nodes  of  the 
axillary  plexus,  and  from  the  net-work  of  the  posterior  thoracic  wall  about  ten  or 
twelve  main  stems  arise  which  converge  laterally  to  terminate  in  the  subscapular 
group  of  the  axillary  plexus.  As  was  the  case  in  the  anterior  net-work,  so  in  the 
posterior  net-work  some  stems  from  the  upper  portions  of  the  dorsal  net-work  pass  to 
the  lower  inferior  deep  cervical  nodes,  and  below  more  or  less  anastomosis  occurs 
between  the  net-works  of  the  thoracic  and  abdominal  (lumbar)  regions. 

The  Mammary  Gland. — The  lvmpbatics  of  the  mammary  gland  arise  in  the 
deeper  portions  of  the  mammary  tissue  from  sack-like  enlargements  situated  in 
the  connective  tissue  between  the  various  lobules  of  the  gland.  The  majority  of 
the  stems  follow  in  general  the  course  of  the  ducts  and,  passing  toward  the  surface, 
communicate  with  an  exceedingly  fine  subareolar  net-work,  which  is  a  special 
development  of  the  general  subcutaneous  net-work  of  the  anterior  thoracic  wall. 
From  the  subareolar  net-work  two  or  more  stems  arise  and  form  the  principal  paths 
for  the  mammary  lymph,  but  accessory  paths  are  also  furnished  by  stems  which  arise 
from  the  sack-like  enlargements  and  pass  toward  the  periphery  of  the  gland, 
avoiding  the  subareolar  net-work. 

The  stems  which  arise  from  the  subareolar  net-work  pass  at  first  almost  directly 
outwards  until  they  reach  the  lower  border  of  the  pectoralis  major.  They  then 
ascend  along;  the  lower  ede;e  of  this  muscle  for  a  short  distance,  and  eventually  bend 


THE    LYMPHATICS    OF    THE   THORAX. 


909 


around  it,  perforate  the  axillary  fascia,  and  terminate  in  the  anterior  pectoral  nodes 
of  the  axillary  plexus.  Occasionally  one  finds  along  the  course  of  one  or  other  of  the 
stems  a  small  intercalated  node,  and  one  or  two  small  nodes,  the  paramammillary 
nodes,  may  occur  a  short  distance  below  the  lower  border  of  the  gland  on  one  of  the 
efferents  which  passes  to  the  lower  principal  stem. 

The  accessory  paths  of  the  mammary  lymph  are  principally  two  in  number. 
(1)  In  about  ten  per  cent,  of  cases  examined  a  stem  issued  from  the  deep  surface  of 
the  gland,  perforated  the  pectoralis  major,  and  passed  upward  between  that  muscle 
and  the  pectoralis  minor  to  terminate  in  the  subclavicular  nodes.  (2)  A  varying 
number  of  small  stems  leave  the  medial  portion  of  the  periphery  of  the  gland  and 
perforate  the  sternal  border  of  the  pectoralis  major  and  the  intercostal  muscles,  to 
terminate  in  the  sternal  nodes. 

It  may  be  noted  that  the  obstacle  to  the  flow  of  lymph  presented  by  enlarged  axillary  nodes 
in  severe  affections  of  the  mammary  gland  may  lead  to  the  development  of  accessory  or 
collateral  paths  other  than  those  mentioned  above.     Thus,  since  the  subareolar  net-work  is 

Fig.  S14. 

Brachial  node 


Subscapular  node 


Anterior  pectoral  node 


Vessel  passing  to  anterior 

pectoral  node \    V 


Inferior  pectoral  node 


Lymphatics  of  mammary  gland 


( Poii 


nd  Cutieo.*) 


continuous  with  the  general  anterior  thoracic  subcutaneous  net-work,  and  the  latter  is  continuous 
across  the  median  line,  affection  of  the  gland  of  one  side  may  cause  enlargement  of  the  axillary 
nodes  of  the  opposite  side,  and,  furthermore,  since  the  thoracic  subcutaneous  net-work  is 
continuous  with  that  of  the  abdomen,  there  is  a  possibility  for  the  establishment  of  a  collateral 
path  leading  to  the  inguinal  nodes. 

Furthermore,  it  is  to  be  remembered  that,  although  the  anterior  pectoral  nodes  are  the 
termination  of  the  principal  mammary  stems,  yet  the  connection  between  these  and  other 
axillary  nodes,  especially  those  of  the  intermediate  and  subclavicular  subgroups,  is  so  intimate 
that  practically  all  the  axillary  nodes  may  be  involved,  or  are  at  least  open  to  suspicion,  in 
cases  of  mammary  carcinoma. 

The  intercostal  lymphatics  are  arranged  in  two  sets  corresponding  to  the 
two  intercostal  muscles  (Sappey).  The  vessels  from  each  internal  intercostal  unite  to 
form  a  single  stem  which  passes  forward  along  the  lower  border  of  the  rib  forming 
the  upper  boundary  of  its  space.  The  stems  of  the  upper  spaces  open  independently 
into  the  sternal  nodes,  while  those  from  the  lower  spaces  unite  to  form  a  common 
ascending  stem  which  terminates  in  the  lowest  node  of  the  sternal  chain. 

*  Poirier  et  Charpy  :   Traits  d'anatomie  humaine,  Tome  ii.,  1902. 


97o  HUMAN    ANATOMY. 

The  vessels  from  the  external  intercostals  are  somewhat  larger  than  those  from 
the  internal  muscles  and  have  a  backward  direction,  terminating  in  the  intercostal 
nodes.  It  is  upon  these  stems  that  the  lateral  intercostal  nodes  are  situated  when 
present.  Anastomoses  occur  between  the  two  sets  of  vessels,  and  the  internal  set 
also  receives  communicating  stems  from  the  parietal  layer  of  the  pleura,  while  the 
external  one  receives  branches  from  the  muscles  which  cover  the  thoracic  wall, 
although  the  principal  path  for  these  leads  to  the  axillary  nodes. 

The  Diaphragm. — The  lymphatics  of  the  diaphragm  form  rich  net-works  upon 
both  its  surfaces,  that  upon  the  peritoneal  surface  being  especially  well  developed,  and 
numerous  vessels  traverse  the  substance  of  both  the  muscular  tissue  and  the  centrum 
tendineum,  uniting  the  net-work  of  the  abdominal  with  that  of  the  thoracic  surface. 
Upon  the  thoracic  surface  the  net-work  is  exceedingly  fine  and  close-meshed  in  the 
region  of  the  centrum  tendineum,  being  most  distinct  in  the  regions  of  the  lateral 
leaflets.  From  this  net-work  branches  pass  outward  parallel  to  the  muscular 
fibres  to  unite  with  a  series  of  anastomosing  stems  whose  general  direction  is  forward. 
Branches  coming  from  the  more  peripheral  portions  of  the  diaphragm  also  empty  into 
these  stems,  which  carry  the  lymph  forward  to  the  diaphragmatic  nodes,  whence  it 
passes  to  the  anterior  mediastinal  nodes.  From  the  net-works  of  the  lateral  leaflets 
of  the  central  tendon  collecting  stems  are  also  directed  backward  and  medially  towards 
the  aortic  opening,  which  they  traverse  to  terminate  in  the  upper  cceliac  nodes. 

It  is  to  be  observed  that  the  nodes  of  the  thoracic  surface  are  for  the  most  part 
situated  anteriorly,  while  the  cceliac  nodes,  which  may  be  regarded  as  the  principal 
nodes  of  the  inferior  surface,  are  located  posteriorly.  Both  sets  of  nodes,  however, 
receive  lymph  from  both  surfaces  of  the  diaphragm  by  means  of  the  perforating 
branches  which  connect  the  upper  and  the  lower  net-works.  The  lower  net-work 
is,  furthermore,  connected  with  the  lymphatics  of  the  more  lateral  portions  of  the 
peritoneum  and  also  with  those  of  the  liver  (page  980),  while  the  upper  net-work 
makes  connections  with  the  lymphatic  vessels  of  the  pleurae.  These  communications, 
when  considered  in  connection  with  the  existence  of  the  perforating  branches,  explain 
the  occurrence  of  pleuritis  as  a  sequence  of  subphrenic  abscess  or  of  the  latter  as  a 
sequence  of  thoracic  empyema. 

The  Heart. — The  lymphatics  of  the  heart  are  arranged  in  two  principal  net- 
works, one  of  which  lies  immediately  beneath  the  endocardium,  while  the  other  is 
upon  the  outer  surface  of  the  organ  immediately  beneath  the  visceral  layer  of  the 
pericardium.  The  endocardial  net-work  communicates  with  the  superficial  one  by 
branches  which  traverse  the  heart  musculature,  and  the  flow  of  lymph  from  the 
endocardial  net-work  takes  place  only  through  these  communicating  branches.  The 
superficial  net-work  extends  over  the  whole  surface  of  the  heart,  the  vessels  of  which 
it  is  formed  being  well  supplied  with  valves  and  arranged  so  as  to  form  characteristic 
quadrate  or  rhomboidal  meshes.  From  the  net-work  longitudinal  stems  pass  up- 
ward towards  the  base  of  the  heart,  corresponding  in  a  general  way  to  the  cardiac 
veins.  Upon  the  anterior  surface  three  stems  are  to  be  found  passing  upward 
along  the  anterior  interventricular  groove,  parallel  to  the  anterior  cardiac  vein,  and, 
on  arriving  at  the  auriculo-ventricular  groove,  they  unite  to  form  a  single  trunk. 
With  this  another  stem  unites  which  has  its  origin  in  the  net-work  of  the  posterior 
surface  of  the  heart  and  ascends  along  the  posterior  interventricular  groove, 
parallel  with  the  posterior  cardiac  vein.  On  reaching  the  auriculo-ventricular  groove 
it  bends  round  to  the  left  and,  encircling  the  base  of  the  left  ventricle,  unites  with 
the  anterior  vessels.  The  conjoined  trunk  so  formed  passes  upward  along  the  pos- 
terior surface  of  the  pulmonary  aorta,  perforates  the  parietal  layer  of  the  pericardium, 
and  terminates  in  one  of  the  bronchial  nodes. 

From  the  net-work  over  the  right  side  of  the  right  ventricle  another  longitudinal 
stem  arises  and  passes  upward  parallel  to  the  right  marginal  vein,  and,  on  reaching  the 
auriculo-ventricular  groove,  winds  around  to  the  right  and  so  reaches  the  anterior 
surface  of  the  heart.  It  then  ascends  parallel  with  the  anterior  trunk,  along  the  pos- 
terior surface  of  the  pulmonary  aorta,  and  also  terminates  in  one  of  the  bronchial  nodes. 

The  Lungs. — The  lymphatics  of  the  lungs  may  be  regarded  as  consisting  of 
two  sets,  deep  and  superficial.  The  deep  set  is  composed  of  a  number  of  stems 
which  accompany  the  branches  of  the  pulmonary  arteries  and  veins  and  of  others 


THE    LYMPHATICS    OF    THE   THORAX.  971 

which  are  associated  more  especially  with  the  bronchi.  The  bronchial  vessels  take 
their  origin  from  a  net-work  contained  in  the  walls  of  the  bronchi,  and  are  traceable 
along  the  entire  length  of  each  bronchus  and  its  branches  until  the  terminal  bronchi 
are  reached  ;  here  the  net-work  disappears  and  no  indications  of  it  are  to  be  found 
in  the  walls  of  the  atria  or  alveoli.  In  the  larger  bronchi  the  net-work  is  double, 
one  portion  of  it  occurring  immediately  beneath  the  mucous  membrane  and  the 
other  external  to  the  cartilaginous  rings,  but  in  the  finer  bronchi  only  one  layer  is 
present  and  from  this  branches  pass  to  the  stems  which  accompany  the  arteries  and 
veins.  All  the  stems  belonging  to  this  deep  set  of  lymphatics  pass  to  the  hilus  of 
the  lung  and  there  open  into  the  pulmonary  nodes. 

The  superficial  set  consists  of  a  net-work  situated  upon  the  surface  of  the  lung, 
immediately  beneath  the  visceral  layer  of  the  pleura.  The  vessels  composing  it  are  well 
supplied  with  valves  and  have  communicating  with  them  branches  from  the  visceral 
layer  of  the  pleura  and  valved  branches  which  have  their  origin  in  the  interlobular  and 
intralobular  connective  tissue.  No  communication  has  been  observed  between  the 
superficial  and  deep  pulmonary  net-works,  the  stems  from  the  superficial  net-work 
alone  passing  toward  the  hilus  of  the  lung  and  terminating  in  the  pulmonary  nodes. 

Lymphatic  vessels  have  been  demonstrated  in  the  parietal  layer  of  the  pleura. 
Those  upon  its  costal  surface  communicate  with  the  intercostal  vessels  ;  those  upon 
the  diaphragmatic  surface  with  the  diaphragmatic  net-work  ;  and  those  upon  the 
mediastinal  surface  with  the  posterior  mediastinal  nodes. 

The  (Esophagus. — The  lymphatics  of  the  oesophagus  are  arranged  in  two  net- 
works, one  of  which  is  submucous,  while  the  other  is  situated  in  the  muscular  coat. 
The  stems  which  drain  the  net-works  of  the  cervical  portion  of  the  oesophagus  pass 
to  the  superior  deep  cervical  and  the  recurrential  nodes,  while  those  draining 
the  thoracic  portions  of  the  net-works  pass  to  the  posterior  mediastinal  nodes. 
Finally,  the  stems  originating  in  the  net-works  of  the  terminal  portion  pass  to  the 
upper  nodes  of  the  cceliac  group. 

Practical  Considerations. —  The  Lymph- Nodes  of  the  Thorax  and  Medias- 
tinum. Anterior  Mediastinum.  — The  nodes  in  close  relation  to  the  internal 
mammary  artery  are  of  practical  importance  on  account  of  their  relations  (a)  to 
the  diaphragm  ;  (b)  to  the  anterior  extremities  of  the  intercostal  spaces  ;  (c)  to  the 
inner  segment  of  the  mammary  gland.  They  may  therefore  be  involved  in  cases 
of  subpleural  (supradiaphragmatic)  abscess,  of  tuberculous  or  syphilitic  or  typhoidal 
caries  of  the  ribs  or  sternum,  or  of  carcinoma  of  the  breast  (page  2035). 

Middle  Mediastinum. — The  nodes  just  below  the  bifurcation  of  the  trachea 
(bronchial,  peribronchial),  in  close  relation  to  the  trachea,  the  bronchi,  and  the 
roots  of  the  lungs,  are  frequently  involved  in  tuberculous  infection  of  the  lungs. 
The  pulmonary  lymphatics,  both  perivascular  and  peribronchial,  communicate  on 
the  one  hand  indirectly  with  the  lymph-spaces  in  the  walls  of  the  alveoli  beneath 
the  epithelial  cells,  and  on  the  other  with  these  nodes.  Solid  particles — and  this 
includes  the  bacillus  tuberculosis  and  other  organisms — are  thus  enabled  to  pass  from 
■  within  the  alveoli  into  the  lymphatic  spaces,  and  from  these  they  are  forced  on  by 
the  respiratory  movements  of  the  lungs  to  the  bronchial  nodes,  to  which  all  the 
lymphatics  converge.  These  nodes  often  contain,  especially  in  coal  miners,  or  in  the 
inhabitants  of  large  cities,  a  large  amount  of  black  pigment,  consisting  of  minute 
particles  of  dust,   smoke   (carbon),    etc.,   that  have  been  inhaled   (Taylor). 

Caseation  and  ulceration  of  these  nodes  have  involved  the  trachea  (page  1840), 
the  bronchi  (especially  the  right  one,  with  which  the  larger  number  are  in  close 
relation),  and  the  oesophagus  (page  16 14),  directly  in  front  of  which  some  of  them  lie. 
Their  enlargement  has  also  produced  various  pressure  symptoms, — dyspncea,  dys- 
phagia, stridulous   respiration,  etc., — which  their  relations  easily  explain. 

Posterior  Mediastinum. — A  group  of  nodes — cesophago-pericardiac  (Leaf) — 
lying  between  the  posterior  surface  of  the  pericardium  and  the  oesophagus,  are  in 
close  relation  to  the  trunk  of  the  pneumogastric  nerve  and  its  oesophageal  branches. 
Their  infection — through  their  direct  connection  with  the  not  infrequently  infected 
nodes  in  the  neck  and  thorax  lying  between  the  trachea  and  oesophagus — may  produce 
symptoms  of  vagus  irritation.      It  has  been  thought  (Guiteras)  that  these  nodes  and 


972 


HUMAN    ANATOMY. 


the  bronchial  nodes  are  especially  enlarged  in  influenza  and  that  some  of  the  anomalous 
pulmonary  symptoms  of  that  disease — simulating  congestion,  pneumonia,  etc. ,  are 
thus  accounted  for.  Marked  enlargement  of  the  bronchial  nodes  may  be  indicated 
by  an  area  of  percussion  dulness  below  the  level  of  the  fourth  dorsal  vertebra  (Yeo). 

In  cancer  of  the  oesophagus  either  the  mediastinal  nodes  or  those  at  the  root  of 
the  neck  may  be  involved,  as  both  sets  receive  lymphatics  from  that  tube.  Medias- 
tinal growth  (sarcoma)  or  abscess  may  originate  in  these  nodes.  Either  condition 
— but  especially  the  neoplasm — will  occasion  marked  symptoms  of  pressure  on 
the  trachea,  bronchi,  oesophagus,  and  superior  cava  and  innominate  veins, — e.g. , 
dyspnoea,  dysphagia,  cedema  of  the  face,  neck,  and  upper  limbs,  dilatation  of  the 
superficial  veins  of  the  abdomen  and  thorax. 

THE   LYMPHATICS   OF   THE   ABDOMEN. 

The  Lymph-Nodes. 

The   principal   nodes  of   the  abdominal    region   are  those  associated  with   the 

viscera  and   those  situated   upon   the    posterior  wall  in   the   vicinity  of   the  aorta. 

A  few  small  and  inconstant  nodes  also  occur  upon  the  anterior  wall,  and  of  these  the 

most  important  are  the  epigastric,  the  circumflex  iliac,  and  the  umbilical  nodes. 

The  epigastric  nodes  ( lymphoglandulae  epigastricae)  are  three  or  four  in 
number  and  are  interposed  in  the  course  of  the  lymphatic  stems  which  accompany 

Fig.  S15. 


-  Umbilical  node 


W^^^ 


Deep  epigastric 

artery 


Umbilical   node 


,ymphatic  vessels 
accompanying  deep 

epigastric  artery 


Epigastric  and  umbilical  lymph-nodes 


(Ciaieo  and  Marcille*) 


the  deep  epigastric  vessels  (Fig.  815)  ;  they  occur  toward  the  lower  part  of  the 
vessels  and  their  efferents  pass  to  the  lower  iliac  nodes. 

The  circumflex  iliac  nodes  are  from  two  to  four  in  number  when  present, 
but  are  notunfrequently  wanting.  They  are  situated  along  the  course  of  the  deep 
circumflex  iliac  vessels  ;  they  receive  affere?iis  from  the  lower  lateral  portions  of  the 
abdominal  wall,  and  send  efferents  to  the  lower  iliac  nodes. 

The  umbilical  nodes  are  situated  in  the  subserous  areolar  tissue  in  the 
neighborhood  of  the  umbilicus.  They  are  three  in  number,  one  being  situated  a 
little  below  and  to  one  side  of  the  umbilicus,  and  the  other  two  above  the  umbilicus 

*Bull.  et  M&m.  Soci£t£  anatom.,  1901. 


THE    LYMPHATICS    OF    THE   ABDOMEN. 


973 


in  the  median  line  (Fig.  815).  They  occur  in  the  net-work  which  covers  the 
posterior  surface  of  the  sheath  of  the  rectus  muscles,  and  are  apparently  of  inconstant 
occurrence. 

The  remaining  abdominal  nodes  may  be  regarded  as  arranged  in  two  principal 
divisions,  one  of  which  includes  the  groups  associated  with  the  various  viscera,  while 
the  other  is  formed  by  the  groups  occurring  in  the  posterior  wall.  This  latter 
division  may  be  separated  into  the  casliac  and  lumbar  nodes. 

The  cceliac  nodes  vary  in  number  from  sixteen  to  twenty,  and  are  situated  in 
front  of  the  abdominal  aorta,  around  the  origins  of  the  cceliac  axis  and  the  superior 
mesenteric  artery.  They  are  extensively  connected  with  one  another  so  as  to  form 
a  distinct  cceliac  plexus  (plexus  coeliacus).  They  receive  afferents  from  the  lower 
portions  of  the  oesophagus,  from  the  diaphragm,  and  from  the  gastric,  hepatic,  pan- 
creatico-splenic,  and  mesenteric  nodes  ;  the  efferents  of  the  lower  nodes  pass  to  the 
higher  members  of  the  group  and  the  efferents  of  these  either  open  independently 


Fig.  816. 


Right 

suprarenal  body- 


Right  kidnej 


Median   lumbar  node 


^ —       /  , Left  lateral 


Left  suprarenal  body 


into  the  receptaculum  chyli,  or,  more  usually,  unite  to  form  a  common  trunk,  the 
truncus  intestinalis,  which  joins  the  left  lumbar  trunk  to  form  one  of  the  origins  of 
the  thoracic  duct  (page  943). 

The  lumbar  nodes  (lymphoglandulae  lumbales)  are  twenty  to  thirty  in  number, 
and  form  three  irregular  longitudinal  rows  along  the  course  of  the  abdominal  aorta 
(Fig.  816),  extending  from  the  level  of  the  second  lumbar  vertebra  to  the  bifurcation 
of  the  aorta,  and  forming  with  the  aid  of  connecting  vessels  a  well-marked  plexus, 
the  plexus  lumbalis.  The  median  row  is  composed  of  some  five  or  six  large  nodes 
situated  upon  the  anterior  surface  of  the  aorta,  and  of  four  or  five  retro-aortic  nodes 
which  rest  upon  the  bodies  of  the  third  and  fourth  lumbar  vertebrae,  immediately 
below  the  lower  extremity  of  the  receptaculum  chyli.  Of  the  lateral  rows  that  of 
the  left  side  is  formed  by  a  number  of  nodes  arranged  in  an  almost  vertical  series 
upon  the  successive  heads  of  the  psoas  muscle.      The  right  lateral  nodes  occupy  a 


*  Bull,  et  Mem.  Societe  anatom.,  1901. 


974  HUMAN    ANATOMY. 

corresponding  position  with  relation  to  the  right  psoas,  lying  posterior  to  the  vena 
cava  inferior,  but  a  varying  number  of  nodes  which  may  be  referred  to  this  group 
also  occur  upon  the  anterior  surface  of  that  vessel. 

Since  all  the  nodes  are  united  by  communicating  vessels,  they  form  a  plexus  and 
will  receive  afferents  from  and  give  efferents  to  one  another.  In  addition,  the  median 
row  receives  afferents  from  the  descending  colon  and  the  mesocolic  nodes,  while  the 
lateral  rows  receive  them  from  the  muscles  of  the  posterior  abdominal  walls,  from 
the  iliac  nodes,  from  the  testes  in  the  male  and  the  ovaries,  Fallopian  tubes,  and 
uterus  in  the  female,  and  from  the  kidneys  and  suprarenal  capsules.  The  efferents 
of  the  upper  nodes  of  the  median  row  pass  upward  to  terminate  in  the  lower  cceliac 
nodes,  while  those  of  the  lateral  rows  either  pass  to  the  nodes  of  the  median  row, 
or  unite  together  to  form  on  either  side  a  common  trunk,  the  truncus  lumbalis, 
which  unites  with  its  fellow  to  form  the  receptaculum  chyli  (page  943),  or  else 
they  perforate  the  crus  of  the  diaphragm  and  open  independently  into  the 
thoracic  duct. 

The  visceral  abdominal  nodes  are  arranged  in  groups  or  chains  which  follow 
in  general  the  principal  visceral  branches  of  the  aorta,  those  following  the  branches  of 
the  cceliac  axis  and  the  superior  mesenteric  artery  communicating  by  their  efferents 

Fig.  817. 


Inferior 

gastr 


Lymphatic  nodes  and  vessels  of  stomach.     (Po/jya  and  Navratil.*) 

mainly  with   the  cceliac  nodes,    while   those  accompanying   the   inferior  mesenteric 
branches  communicate  with  the  median  lumbar  nodes. 

Corresponding  with  the  branches  of  the  cceliac  axis  are  the  gastric,  hepatic,  and 
pancreatico-splenic  nodes.  The  gastric  nodes  consist  of  two  chains  (lympho- 
glandulae  gastricae  superiores  et  inferiores)  situated  respectively  along  the  lesser  and 
greater  curvatures  of  the  stomach.  The  superior  nodes,  three  to  fifteen  in  number, 
are  situated  along  the  course  of  the  gastric  artery,  principally  along  the  lesser 
curvature  of  the  stomach  between  the  two  layers  of  the  gastro-hepatic  omentum 
(Fig.  817),  although  a  few  also  occur  along  the  course  of  the  artery  before  it 
reaches  the  stomach  and  ethers  upon  the  left  side  of  the  cardiac  orifice  of  the 
viscus.  The  inferior  nodes  are  situated  in  the  vicinity  of  the  pyloric  end  of  the 
stomach,  partly  along  the  right  half  of  the  greater  curvature,  accompanying 
the  right  gastro-epiploic  vessels,  and  partly  on  the  posterior  surface  of  the  pylorus 
along  the  course  of  the  gastro-duodenal  vessels.  The  gastric  nodes  receive  afferents 
from  the  stomach  and  in  the  case  of  the  retro-pyloric  nodes  also  from  the  first 
portion  of  the  duodenum,  and  their  effe7-ents  pass  to  the  cceliac  nodes,  those  of 
the  superior  group  following  the  course  of  the  gastric  vessels,  while  those  from  the 
inferior  group  accompany  the  gastro-duodenal  and  hepatic  arteries. 

*  Deutsche  Zeitschrift  f.  Chirurgie,  Bd.  lxix. 


THE  LYMPHATICS  OF  THE  ABDOMEN. 


975 


The  hepatic  nodes  (lymphoglandulae  hepaticae)  are  more  or  less  clearly  arranged 
in  two  series.  One  series  accompanies  the  main  stem  of  the  hepatic  artery  along  the 
upper  border  of  the  head  of  the  pancreas  and  throughout  the  vertical  portion  of  its 
course  in  the  free  margin  of  the  gastro-hepatic  omentum,  and  the  other  accompanies 
the  superior  pancreatico-duodenal  branch  and  ascends  along  the  bile-duct  to  the 
portal  fissure.  The  afferents  of  the  nodes  come  from  the  liver,  the  head  of  the 
pancreas,  and  the  first  and  second  portions  of  the  duodenum,  and  their  effcrents  pass 
to  the  cceliac  nodes. 

The  pancreatico-splenic  nodes  (lymphoglandulae  pancreaticolienales)  accom- 
pany the  splenic  artery  throughout  the  greater  portion  of  its  course,  and  are 
consequently  situated  along  and  partly  behind  the  upper  border  of  the  pancreas 
(Fig.  8 1 8).  They  vary  in  number  from  four  to  ten,  and  their  afferents  come  from 
the  organs  supplied  by  the  splenic  artery, — namely,  the  stomach,  pancreas,  and 
spleen, — while  their  efferents  pass  to  the  coeliac  nodes. 

The  mesenteric  nodes  (lymphoglandulae  mesentericae)  are  from  one  hundred  to 
two  hundred  in  number,  and  are  arranged  along  the  superior  mesenteric  artery  and 
its  branches  to  the  small  intestine.  They  form  three  more  or  less  distinct  series, 
especially  towards  the  upper  portion   of  the  mesentery.      One  series,  in  which  the 

Fig.  SiS. 


Retropyloric  node 


Mcsoeolic  node 


Pancrealico-splenic  nodes 


Pancreatico-splenic,  retropyl 


Transverse  mesocolo 


■  . c  nodes,  new-born  child  ;   liver  drawn  upward,  stomach  and 

duodenum  laterally.     {Cuueo  and  Delaware.*) 


nodes  are  more  numerous  and  smaller  than  the  others,  lies  close  to  the  intestine, 
among  the  terminal  branches  of  the  artery  ;  a  second  consists  of  larger  scattered 
nodes  situated  along  the  primary  branches  of  the  artery  ;  while  the '  third  series 
includes  the  closely  aggregated  nodes  which  surround  its  main  stem.  Towards  the 
lower  portion  of  the  ileum  the  distinction  of  the  first  and  second  series  becomes 
less  and  less  apparent,  and  at  the  junction  of  the  ileum  and  caecum  the  nodes  form  a 
single  group,  situated  a  short  distance  from  the  intestine  between  the  two  layers  of 
the  mesentery.  These  nodes  are  sometimes  termed  the  ileo-caecal  nodes,  and 
associated  with  them  by  means  of  its  efferents  is  a  variable  group  of  small  nodes, 
the  appendicular  nodes,  situated  partly  in  the  base  of  the  mesenteriole  of  the 
appendix  and  partly  in  the  immediate  vicinity  of  the  junction  of  the  ileum  and 
caecum   (Fig.  820). 

The  various  series  of  nodes'  are  connected  with  one  another  by  vessels,  which  in 
this  region  are  known  as  lacteals,  and  the  nodes  of  the  first  series  receive  their 
afferents  from  the  walls  of  the  small  intestine,  and,  in  the  case  of  the  ileo-caecal  nodes, 
from  the  caecum  and  vermiform  appendix.  The  efferents  of  the  nodes  of  the  third 
series  pass  to  those  nodes  of  the  cceliac  group  which  are  situated  around  the  origin 
of  the  superior  mesenteric  artery. 

*  Jour,  de  l'anat.  et  de  la  physiol.,  Tome  xxxvi.,  1900. 


976  HUMAN   ANATOMY. 

The  nodes  which  are  associated  with  the  abdominal  portions  of  the  large  intestine 
are  known  as  the  mesocolic  nodes  ( lymphoglandulae  mesocolicae)  and  they  consist 
of  from  twenty  to  fifty  small  nodes  which  are  situated  close  to  the  intestine  (Fig.  818). 
Their  afferents  are  received  from  the  entire  length  of  the  large  intestine,  with  the 
exception  of  the  csecum  and  appendix  and  the  rectum,  and  the  efferents  of  the  nodes 
associated  with  the  ascending  colon  and  the  right  half  of  the  transverse  colon  pass  to 
the  lower  cceliac  nodes,  while  those  of  the  nodes  associated  with  the  left  half  of  the 
transverse  colon  and  with  the  descending  and  sigfnoid  colons  pass  to  the  median  row 
of  lumbar  nodes. 

In  addition  to  the  nodes  which  are  properly  included  in  the  mesocolic  group 
there  are  a  number  of  small  nodes  situated  upon  the  lateral  walls  of  the  upper  part  of 
the  rectum,  along  the  lines  of  the  superior  hemorrhoidal  vessels  (Fig.  821).  These 
ano-rectal  nodes  are  from  two  to  eight  in  number  on  each  side,  and  are  situated 
beneath  the  fibrous  investment  of  the  rectum,  resting  directly  upon  the  outer  surface 
of  the  muscular  coat.  They  receive  their  afferents  from  the  neighboring  portions  of 
the  wall  of  the  rectum  and,  in  the  female,  from  the  posterior  surface  of  the  vagina, 
and  their  efferents  pass  to  the  mesocolic  nodes  situated  in  the  lower  part  of  the 
mesentery  of  the  sigmoid  colon. 

The   Lymphatic  Vessels. 

The  Abdominal  Walls. — The  anterior  abdominal  wall,  as  regards  its 
lymphatic  vessels,  may  be  divided  into  a  supra-  and  an  infra-umbilical  region.  The 
lymphatics  of  the  former  area  belong  in  reality  to  the  thoracic  cutaneous  set,  passing 
upward  to  join  the  thoracic  stems  which  terminate  in  the  anterior  pectoral  nodes  of 
the  axillary  plexus.  The  vessels  of  the  infra-umbilical  region,  on  the  contrary', 
descend  to  terminate  in  the  inguinal  nodes.  Along  the  line  of  junction  of  the  two 
regions  anastomoses  occur  and  the  vessels  of  the  right  half  of  the  abdominal  wall  also 
communicate  with  those  of  the  left  half.  The  subcutaneous  vessels  of  the  posterior 
abdominal  and  lumbar  regions  anastomose  with  the  corresponding  vessels  of  the 
posterior  thoracic  region  above,  and  below  with  those  of  the  gluteal  region.  They 
form  an  extensive  net-work,  from  which  stems  pass  downward  and  forward,  parallel 
with  the  crest  of  the  ilium,  to  terminate  in  the  inguinal  nodes. 

The  lymphatic  net-work  of  the  deeper  structures  of  the  abdominal  walls  is 
drained  by  a  number  of  stems  which  follow  in  general  the  courses  of  the  blood- 
vessels. Thus,  the  stems  which  lead  away  from  the  upper  portion  of  the  abdominal 
wall  pass  upward  along  the  course  of  the  superior  epigastric  vessels  to  terminate  in 
the  lower  sternal  nodes  ;  another  set  follows  the  course  of  the  deep  epigastric  vessels 
to  terminate  in  the  lower  iliac  nodes,  after  traversing  the  epigastric  nodes  ;  another 
accompanies  the  deep  circumflex  iliac  vessels,  draining  the  lower  portions  of  the  lateral 
walls  of  the  abdomen,  traversing  the  circumflex  iliac  nodes,  and  also  terminating  in 
the  iliac  nodes  ;  while  other  sets  accompany  the  lumbar  vessels  and  terminate  in  the 
lateral  rows  of  lumbar  nodes.  Abundant  communications  exist  between  the  vessels  of 
adjacent  drainage  areas  and  from  the  region  of  the  umbilicus  the  lymph  flow  may  follow 
any  one  of  the  paths  mentioned  above.  Attention  may  be  called  to  the  occasional 
presence  of  nodes  in  the  course  of  the  vessels  arising  in  the  umbilical  region  (page  972). 

The  Stomach. — The  lymphatics  of  the  stomach  have  their  origin  in  two 
net-works,  one  of  which  is  situated  in  the  mucosa  and  the  other  in  the  muscular 
coat.  The  net-work  of  the  mucosa  occurs  uninterruptedly  throughout  the  entire 
extent  of  the  gastric  surface  and  is  continuous  with  the  corresponding  net-works  of 
both  the  oesophagus  and  duodenum.  From  its  deeper  surface  branches  pass  to  a 
more  open  net-work  situated  upon  the  outer  surface  of  the  submucosa,  and  from  this 
stems  traverse  the  muscular  coat  obliquely  to  terminate  in  a  subserous  net-work  which 
also  receives  branches  from  the  net-work  of  the  muscular  coat.  Connections  between 
the  muscular  and  mucous  net-works  occur,  but  they  are  so  indirect  that  an  extensive 
cancerous  infection  of  the  mucosa  may  reach  the  outer  layers  of  the  stomach  only  at 
limited  areas  at  some  distance  from  one  another. 

The  subserous  net-work  with  which  both  primary  net-works  communicate  gives 
origin  to  a  number  of  stems  which  pass  to  the  gastric  nodes,  and  the  course  which  they 
follow  is  such  that  the  entire  surface  of  the  stomach  may  be  regarded  as  presenting 


THE    LYMPHATICS    OF    THE   ABDOMEN. 


977 


three  more  or  less  distinct  lymphatic  areas  (Fig.  817 J.  Not  that  the  areas  are 
perfectly  separated  from  one  another  ;  on  the  contrary,  the  subserous  net-work  is 
continuous  Bover  the  entire  surface.  But  the  collecting  stems  from  each  area  follow 
a  definite  route  toward  different  node  groups.  The  largest  of  these  areas  occupies 
roughly  the  whole  of  the  upper  border  of  the  stomach  from  the  fundus  to  the 
pylorus,  and  extends  downward  on  either  surface  to  about  two-thirds  of  the  distance 
to  the  greater  curvature.  Its  collecting  stems  all  pass  to  the  superior  cardiac  nodes. 
The  second  area  occupies  about  the  pyloric  two-thirds  of  the  greater  curvature,  and 
its  efferents  pass  to  the  inferior  gastric  nodes,  while  the  third  and  smallest  area 
occupies  the  lower  part  of  the  fundus  and  the  cardiac  one-third  of  the  greater 
curvature,  and  sends  its  efferents  to  the  splenic  nodes.  It  may  be  remarked  that 
these  areas  correspond  in  a  general  way  with  the  areas  drained  by  the  principal  veins 
arising  in  the  stomach  walls.  Thus,  the  large  upper  area  corresponds  in  general  with 
the  drainage  area  of  the  gastric  vein,  the  lower  pyloric  area  to  that  of  the  right 
gastro-epiploic  vein,  and  the  lower,  cardiac  area  to  that  of  the  left  gastro-epiploic. 
It  may  further  be  noted  that  while  the  subserous  net-work  communicates  with  the 
superficial  net-work  of  the  oesophagus,  it  seems  to  be  completely  cut  off  from  connec- 
tion with  the  corresponding  duodenal  net-work,  an  arrangement  which  is  in  striking 
contrast   to   the    continuity  which 

exists    between    the    gastric    and  FlG-  Sl9- 

duodenal  mucosa  net-works  and 
explains  the  rare  extension  of  a 
carcinomatous  infection  of  the 
pylorus  to  the  duodenum  by  the 
subserous  route. 

The  Small  Intestine. — 
Throughout  the  entire  length  of 
the  intestine,  both  small  and  large, 
the  lymphatic  net  -  works  are 
arranged  in  two  sets,  one  of  which 
is  situated  in  the  mucosa  and  the 
other  in  the  muscular  coat.  The 
two  net-works  are  more  or  less 
independent,  though  communicat- 
ing branches  occur,  and  both  open 
into  a  subserous  net-work  from 
which  collecting  stems  arise. 

The  stems  which  pass  from 
the  duodenum  are  divisible  into 
two  groups  according  as  they  arise  from  the  anterior  or  posterior  surface.  Those 
coming  from  the  anterior  surface  pass  to  the  chain  of  nodes  situated  along  the 
course  of  the  inferior  pancreatico-duodenal  artery,  and  so  to  the  cceliac  nodes, 
which  surround  the  origin  of  the  superior  mesenteric  artery,  while  the  posterior 
stems  pass  to  the  hepatic  nodes  situated  along  the  course  of  the  superior  pancreatico- 
duodenal vessels  and  so  to  the  cceliac  nodes  which  surround  the  cceliac  axis.  Some 
of  the  stems  which  take  their  origin  from  the  first  part  of  the  duodenum  pass  to 
those  nodes  of  the  inferior  gastric  group  which  are  situated  upon  the  posterior 
surface  of  the  pyloric  region  of  the  stomach,  and,  since  these  nodes  also  receive 
afferents  from  the  pylorus,  they  afford  opportunity  for  the  transference  of  a  superficial 
infection  from  the  pylorus  to  the  duodenum,  a  direct  route  for  infection  in  this 
direction  being  wanting  (see  above). 

The  collecting  stems  of  the  jejunum  and  ileum  pass  to  the  first  series  of 
mesenteric  nodes,  situated  along  the  line  of  attachment  of  the  mesentery  to  the 
intestine,  and,  after  traversing  these,  are  continued  onward  to  the  second  and  third 
series  of  nodes,  whose  efferents  pass  to  the  cceliac  nodes  surrounding  the  origin  of 
the  superior  mesenteric  artery.  The  vessels  issuing  from  the  jejuno-ileum  are  usually 
spoken  of  as  the  lacteals,  on  account  of  their  contents,  especially  at  times  when 
absorption  of  food  constituents  is  proceeding  rapidly  in  the  intestine,  having  a  milky 
appearance,  owing  to  the  presence  of  numerous  fat  globules  in  the  lymphocytes. 

62 


Mesenteric  lymphatic  nodes  and  vessels ;   peritoneal  covering  of 
mesentery  has  been  removed. 


978 


HUMAN    ANATOMY. 


The  Large  Intestine. — The  two  sets  of  lymphatic  net-works  characteristic  of 
mucous  membranes  occur  in  the  walls  of  the  large  intestine,  and  they  communicate 
with  one  another  and  finally  open  into  a  subserous  net-work  from  which  collecting 
stems  take  origin.  In  the  vermiform  appendix  (Fig.  820)  these  collecting  stems  are 
from  three  to  five  in  number  and  pass  upward  in  the  mesenteriole  to  terminate  in 
the  appendicular  nodes  or,  in  the  absence  of  these,  directly  in  the  ileo-caecal  nodes. 
The  subserous  net-work  of  the  base  of  the  appendix  communicates  freely  with  that  of 
the  caecum,  whose  collecting  stems  have  essentially  the  same  course  as  those  of  the 
appendix,  passing  primarily  to  the  appendicular  nodes  situated  in  the  neighborhood 
of  the  ileo-caecal  junction  and  thence  to  the  ileo-cascal  nodes.  The  ultimate  nodes 
of  the  appendicular  and  caecal  systems  are  situated  in  the  root  of  the  mesentery  along 
the  course  of  the  superior  mesenteric  vessels  ;  they  belong  to  the  group  of  mesenteric 
nodes  and  receive  their  afferents  in  part  from  the  ileo-caecal  nodes. 

Communications  have  been  described  as  existing  between  the  appendicular  lymphatics 
and  those  of  the  broad  ligament  of  the  uterus  as  well  as  the  iliac  nodes.  The  more  recent 
observations   have  failed,  however,  to'  confirm   the  existence  of  any  direct  connection   with 

these  structures,  and  patholog- 
Fig.  S20.  ical   conditions  of   the  broad 

ligament  and  iliac  nodes  asso- 
ciated with  acute  appendicitis 
may  perhaps  be  due  to  a 
dissemination  of  the  infection 
through  the  subperitoneal  net- 
work by  way  of  the  so-called 
appendiculo-ovarian  ligament. 

The  collecting  stems 
from  the  subserous  net- 
work of  the  ascendi?ig  colon 
pass  primarily  to  some  in- 
constant mesocolic  nodes, 
r  situated  along  the  line  of 
attachment  of  the  colon  to 
the  abdominal  wall,  and 
thence  are  continued  along 
the  lines  followed  by  the 
right  colic  vessels  to  the 
superior  mesenteric  nodes. 
The  stems  from  the  trans- 
verse colon  have  a  more 
varied  course  in  accordance  with  the  arrangement  of  the  blood-vessels.  They  pass 
primarily  to  a  series  of  mesocolic  nodes  situated  between  the  layers  of  the  transverse 
mesocolon  close  to  the  intestine  ;  these  are  of  larger  size  and  more  numerous  than 
the  nodes  associated  with  either  the  ascending  or  descending  colon  and  are  especially 
well  developed  toward  either  angle  of  the  colon.  Their  efferents  pass  principally 
to  some  four  or  five  nodes  situated  along  the  course  of  the  middle  colic  vessels  and 
thence  to  the  third  group  of  mesenteric  nodes,  but  those  from  the  vicinity  of  the 
splenic  flexure  follow  the  course  of  the  branches  of  the  left  colic  vessels  and  so  pass 
to  the  nodes  of  the  median  lumbar  group  situated  in  the  neighborhood  of  the  inferior 
mesenteric  artery.  The  lymphatics  of  the  transverse  colon  communicate  somewhat 
extensively  with  those  of  the  great  omentum,  as  the  result  of  the  attachment  of  the 
latter  to  the  colon,  and  they  are  thus  placed  in  connection  with  the  inferior  gastric 
and  splenic  nodes. 

The  collecting  stems  from  the  descending  colon  and  sigmoid  flexure  pass 
primarily  to  mesocolic  nodes  situated  close  to  the  attached  surface  of  the  intestine, 
and  thence  follow  the  courses  of  the  left  colic  and  sigmoid  vessels  to  the  median 
lumbar  nodes  situated  in  the  vicinity  of  the  origin  of  the  inferior  mesenteric  artery. 


Ileo-ctecai  and  appendi 
(Polya 


des  and  vessels 


■Deutsche  Zeitschrift  f.  Chirursfie,  Bd.  lxix. 


THE  LYMPHATICS  OF  THE  ABDOMEN. 


979 


The  mesocolic  nodes  associated  with  the  descending  colon  are  less  numerous 
and  smaller  than  those  of  the  sigmoid  flexure  and  resemble  in  appearance  and 
arrangement  those  of  the  ascending  colon. 

The  lymphatics  of  the  rectum  (Fig.  821),  although  belonging  in  large  part  to  the 
pelvic  region,  may,  for  the  sake  of  completeness  of  the  account  of  the  intestinal 
lymphatics,  be  considered  here  in  their  entirety.  Of  the  two  primary  net-works  that 
of  the  muscular  coat  is  injected  only  with  difficulty,  but  it  communicates  with  the 
mucosa  net-work  and  its  collecting  stems  follow  the  same  course  as  those  of  the 
deeper  net-work.  In  the  mucosa  net-work  two  zones  may  be  distinguished,  one  of 
which  includes  the  greater  portion  of  the  net-work  and  extends  down  to  the  lower 
ends  of  the  columns  of  Morgagni,  while  the  other  includes  that  portion  of  the  mucosa 
intervening  between  that  level  and  the  anal  integument.  The  upper  zone  may  be 
termed  the  net-work  of  the  rectal  mucosa,  while  the  lower  one  may  be  designated 
as  the  net-work  of  the  anal 

mucosa,   since  the  region  in  Fig.  821. 

which  it  occurs  forms  the 
transition  between  the  mu- 
cosa and  the  anal  integument. 

The  collecting  stems 
from  the  net-work  of  the 
rectal  mucosa  traverse  the 
muscular  coat  and  enter  into 
relation  with  the  ano-rectal 
nodes  (  page  976  ).  After 
traversing  these  they  are 
continued  onward  along  the 
course  of  the  superior  hemor- 
rhoidal vessels  and  open  into 
the  lower  mesocolic  nodes, 
from  which  efferents  pass  to 
the  median  lumbar  nodes 
situated  in  the  neighborhood 
of  the  origin  of  the  inferior 
mesenteric  artery.  The  net- 
work of  the  anal  mucosa  sends 
numerous  branches  upward  to 
communicate  with  the  lower 
part  of  the  rectal  mucosa  net- 
work. These  branches  trav- 
erse for  the  most  part  the 
columns  of  Morgagni  in  which 
they  are  so  numerous  as  to  earn  for  themselves  the  appellation  of  glomi  lymphatic!, 
while,  on  the  other  hand,  the  mucosa  of  the  depressions  between  the  columns  is 
comparatively  poor  in  lymphatics.  Some  collecting  stems  from  the  anal  mucosa 
perforate  the  muscular  coat  and  pass  to  the  ano-rectal  nodes,  and  thence  along  with 
the  stems  from  the  rectal  mucosa  to  the  lower  mesocolic  nodes,  while  others  follow 
the  course  of  the  middle  hemorrhoidal  vessels  and  terminate  in  nodes  belonging  to 
the  hypogastric  group  (page  984)  situated  at  the  point  where  the  internal  iliac 
artery  divides  into  its  leash  of  branches,  or  else  at  the  level  of  the  great  sacro-sciatic 
notch,  a  little  below  the  point  where  the  obturator  vein  joins  the  internal  iliac. 

The  lymphatics  of  the  anal  integument  will  be  considered  together  with  those  of 
the  perineal  region  (page  987). 

The  Pancreas. — The  lymphatics  of  the  pancreas  take  their  origin  from  a 
perilobular  net-work  from  which  collecting  stems  pass  to  the  neighboring  nodes, 
following  the  course  of  the  blood-vessels  which  supply  the  gland.  The  great  majority 
of  them  pass  to  the  chain  of  splenic  nodes  which  extends  along  the  upper  border  of 
the  pancreas,  but  those  of  the  head  of  the  gland  pass  in  part  to  nodes  of  the  hepatic 


Lymphati 


f  rectum.    {Gerota; 


-Arcliivf.  Anat.  11.   Physiol.,  1S95. 


980 


HUMAN    ANATOMY. 


group,  following  the  course  of  the  superior  pancreatico-duodenal  vessels,  while  others 
again  accompany  the  inferior  pancreatico-duodenal  vessels  to  terminate  in  nodes 
belonging  to  the  mesenteric  group. 

The  Liver. — The  lymphatics  of  the  liver  are  arranged  in  perilobular  net-works 
from  which  stems  pass  in  two  principal  directions  ;  those  which  come  from  the  deeper 
portions  of  the  net-work  follow  the  course  of  either  the  portal  or  hepatic  venous 
branches,  while  those  arising  from  the  net-works  surrounding  the  more  superficial 
lobules  pass  to  the  surface  of  the  liver,  upon  which  they  anastomose  extensively  to 
form  a  subserous  net-work  from  which  efferent  stems  arise. 

The  deep  eflerents  which  accompany  the  branches  of  the  portal  vein  take  their 
course  in  the  substance  of  the  capsule  of  Glisson,  two  or  three  stems  accompanying 
each  of  the  larger  branches  of  the  vein  and  anastomosing  with  one  another  to  form 
a  plexus  around  the  vessel  and  the  accompanying  branches  of  the  hepatic  artery  and 
bile-duct.  As  the  branches  of  the  vein  are  followed  to  their  union  to  form  larger 
trunks,  the  accompanying  lymphatics  unite  to  a  considerable  extent,  so  that  from 
fifteen  to  twenty  stems  emerge  at  the  transverse  fissure  and  terminate  in  the  hepatic 


Lymphatics  of  postero-inferior  surface  of  liver,  a,  a,  trunks  arising  from  vicinity  of  right  border  of  liver  and 
going  to  one  of  the  nodes  surrounding  inferior  cava  (C)  as  it  enters  thorax;  b,  trunk  arising  from  inferior  sur- 
face of  right  lobe  and  emptying  at  hilum  into  nodes  resting  on  neck  of  gall-bladder ;  c,  trunks  arising  near  gall- 
bladder and  going  to  lower  hiTum-nodes;  d,  trunks  running  on  attached  surface  of  gall-bladder;  e,e,e,  trunks 
that  take  origin  from  superficial  net-works  and  disappear  in  liver  to  follow  branches  of  portal  vein  to  hilum- 
nodes;  /,/,/,  caval  nodes  receiving  vessels  from  Spigelian  lobe  (g)\  h,  A,  principal  trunks  of  left  lobe;  i,  i,  i, 
trunks  that  arise  from  superficial  net-works  and  dip  into  liver  to  join  vessels  in  capsule  of  Glisson ;  j,  trunks 
from  superior  surface  of  liver  which  follow  round  ligament  to  hilum-nodes;  i,  trunks  from  superior  surface  that 
end  in  nodes  in  posterior  part  of  longitudinal  fissure  (/) ;  m,  trunks  connecting  these  nodes  with  those  in  hilum; 
n  (14),  nodes  connected  with  terminal  part  of  cesophagus  ;  o,  o,  o  (15),  hilum  nodes  which  receive  all  trunks 
accompanying  vena  porta  and  large  part  of  those  from  inferior  surface;  />,/,  vessels  from  quadrate  lobe  (q). 
(Sappey.*) 

nodes  situated  in  the  fissure.  The  stems  which  accompany  the  branches  of  the 
hepatic  vein  also  form  more  or  less  distinct  plexuses,  and,  when  they  emerge  from 
the  liver  substance,  are  from  five  to  six  in  number.  They  continue  upward  along 
the  inferior  vena  cava,  pass  with  it  through  the  diaphragm,  and  terminate  in  the  nodes 
situated  on  the  convex  surface  of  the  diaphragm  around  the  orifice  for  the  vena  cava. 
The  superficial  vessels  have  more  diversified  courses,  and  it  will  be  convenient 
to  consider  them  as  belonging  to  two  groups  according  as  they  arise  from  the 
superior  or  inferior  surface  of  the  liver.  And  first  those  arising  from  the  net-work 
of  the  superior  surface  may  be  described.  Those  which  arise  toward  the  posterior 
portion  of  the  surface  of  both  the  right  and  left  lobes  pass  mainly  toward  the  vena  cava 
inferior  and  ascend  with  it  through  the  diaphragm  to  terminate  in  the  nodes  situated 

*  Description  et  Iconographie  des  Vaisseaux  lymphatiques,  1874. 


THE  LYMPHATICS  OF  THE  ABDOMEN.  981 

around  the  opening  for  the  vena  cava.  From  the  more  lateral  portions  of  each 
lobe,  however,  the  collecting  stems  take  a  different  course,  those  from  the  right  lobe 
uniting  to  form  a  single  stem  which  passes  backward  between  the  layers  of  the  right 
lateral  (triangular)  ligament,  and  then  passes  medially  over  the  surface  of  the  right 
crus  of  the  diaphragm  to  terminate  in  the  nodes  surrounding  the  cceliac  axis.  Those 
from  the  lateral  portions  of  the  left  lobe  pass  backward  between  the  layers  of 
the  left  lateral  (triangular)  ligament  and  terminate  in  the  nodes  of  the  superior 
gastric  group  which  are  situated  in  the  neighborhood  of  the  cardiac  orifice  of  the 
stomach. 

The  collecting  stems  of  the  anterior  portion  of  the  superior  surface  are  relatively 
small  and  are  more  conspicuous  on  the  right  lobe  than  on  the  left.  They  pass 
forward  and  downward  to  curve  around  the  anterior  border  of  the  liver,  and  join  with 
the  stems  arising  from  the  quadrate  lobe  and  gall-bladder  to  pass  with  these  to  the 
hepatic  nodes  situated  in  the  transverse  fissure.  Finally,  much  more  important  than 
these,  is  a  group  of  vessels  which  arise  from  a  rich  subserous  net-work  situated  alono- 
the  line  of  attachment  of  the  suspensory  (falciform)  ligament.  Some  of  these  vessels 
take  a  backward  course  toward  the  vena  cava  and  accompany  the  other  vessels  of 
the  superior  surface  which  terminate  in  the  caval  diaphragmatic  nodes,  and  others 
pass  forward  until  they  meet  the  upper  portion  of  the  round  ligament,  which  they 
follow  to  reach  the  nodes  situated  in  the  transverse  fissure.  The  remaining  stems  of 
the  group,  from  three  to  ten  in  number,  pass  forward  and  upward,  between  the  layers 
of  the  suspensory  ligament,  toward  the  under  surface  of  the  diaphragm,  traverse 
that  structure  near  its  anterior  attachment,  and  come  into  connection  with  a 
number  of  small  nodes  situated  behind  the  xiphoid  process  of  the  sternum.  From 
these  they  are  continued  upward  along  the  course  of  the  internal  mammary  vessels 
to  terminate  in  the  lower  nodes  of  the  inferior  deep  cervical  group,  usually  upon  the 
left  side,  rarely  upon  the  right.  This  path  is  of  importance  as  furnishing  a  direct  route 
by  which  the  metastasis  of  the  left  supraclavicular  nodes,  frequently  induced  by 
abdominal  carcinomata,  may  be  produced.  It  must,  furthermore,  be  noted  that 
both  these  vessels  and  others  which  arise  from  the  superior  surface  of  the  liver  com- 
municate somewhat  extensively  with  the  net-work  occurring  on  the  under  surface  of 
the  diaphragm,  and  since  this  net-work  communicates  abundantly  with  that  of  the 
thoracic  surface  of  the  diaphragm,  and  this  again  with  the  vessels  of  the  pleura, 
opportunity  is  afforded  for  the  development  of  pleuritis,  especially  upon  the  right 
side,  as  a  result  of  a  subdiaphragmatic  infection. 

Turning  now  to  the  stems  arising  from  the  superficial  net-work  of  the  inferior 
surface  of  the  liver,  it  will  be  found  that  they  pass  principally  to  the  hepatic  nodes 
situated  in  the  transverse  fissure,  at  least  these  nodes  form  the  termination  for  the 
vessels  passing  from  the  left  and  quadrate  lobes,  the  left  half  of  the  Spigelian  and 
the  anterior  and  middle  portions  of  the  right  lobe.  Those,  however,  which  take 
their  origin  toward  the  posterior  part  of  the  right  lobe  and  from  the  right  half  of 
the  Spigelian  pass  to  the  vena  cava  and,  ascending  along  it,  terminate  in  the  dia- 
phragmatic nodes  surrounding  its  opening  into  the  thorax. 

The  lymphatics  of  the  gall-bladder  and  common  bile-duct  have  their  origin 
in  two  net-works,  one  of  which  is  situated  in  the  mucosa  and  die  other  in  the  muscular 
coat.  Efferents  from  both  net-works  pass  to  the  surface  to  form  a  superficial 
net-work,  from  which  collecting  stems  pass,  in  the  case  of  the  gall-bladder  to  the 
nodes  situated  in  the  transverse  fissure,  and  in  the  case  of  the  duct  for  the  most 
part  to  a  chain  of  nodes  belonging  to  the  hepatic  group,  which  occurs  along  the  line 
of  the  duct  in  the  edge  of  the  gastro-hepatic  omentum  ;  those  from  the  lower  portion 
of  the  duct,  however,  associate  themselves  with  stems  from  the  duodenum  and  head 
of  the  pancreas  which  open  into  the  uppermost  nodes  situated  along  the  course  of 
the  superior  pancreatico-duodenal  vessels. 

Stated  in  brief,  the  destinations  of  the  hepatic  lymphatics  are  principally  the 
hepatic  nodes  situated  in  the  transverse  fissure  and  the  diaphragmatic  nodes  which 
surround  the  opening  of  the  inferior  vena  cava.  A  vessel  from  the  right  lobe  also 
passes  to  the  cceliac  nodes,  some  from  the  left  lobe  to  the  superior  gastric  nodes, 
and  an  important  group  passes  up  in  the  suspensory  ligament  to  communicate  with 
some  of  the  anterior  diaphragmatic  nodes  and  terminate  in  the  lower  inferior  deep 


HUMAN    ANATOMY. 


cervical  nodes.  Finally,  it  is  to  be  remembered  that  numerous  communications 
exist  between  the  superficial  hepatic  lymphatics  and  those  which  form  the  net-work 
on  the  abdominal  surface  of  the  diaphragm. 

The  Spleen. — The  lymphatics  of  the  spleen  are  arranged  in  a  superficial  and 
a  deep  set,  numerous  communications  occurring  between  the  two.  The  vessels 
of  the  superficial  set  are  subserous  in  position  and  converge  toward  the  hilus  to 
terminate  in  the  adjacent  pancreatico-splenic  nodes,  to  which  the  deep  lymphatics, 
which  accompany  the  blood-vessels  of  the  spleen,  also  pass. 

The  Kidneys  and  Ureters. — The  lymphatics  of  the  kidney  form  three  net- 
works, one  of  which  is  situated  in  the  cortical  tissue  of  the  kidney,  the  second,  whose 
meshes  are  very  fine,  is  situated  immediately  beneath  the  fibrous  capsule,  while  the 
third  occurs  beneath  the  peritoneum  in  the  superficial  portions  of  the  adipose  capsule. 
The  efferents  of  the  cortical  net-work  follow  the  branches  of  the  renal  vessels 
through  the  medullary  substance  and  emerge  at  the  hilus  in  the  form  of  from  four  to 

seven  vessels,  which  pass 
toward  the  median  line  of 
the  posterior  abdominal 
wall  along  the  course  of 
the  renal  veins,  and  termi- 
nate in  the  upper  nodes  of 
the  lateral  lumbar  groups 
(Fig.  823).  Those  which 
come  from  the  right  kid- 
ney terminate  partly  in 
nodes  which  lie  in  front 
of  the  inferior  vena  cava, 
and  partly  in  two  or  three 
large  nodes  which  are 
situated  behind  that  vessel 
upon  the  right  crus  of  the 
diaphragm.  The  efferents 
from  these  nodes  pierce 
the  crus  and  terminate 
directly  in  the  thoracic 
duct.  The  uppermost 
nodes  to  which  the  vessels 
of  the  left  kidney  pass 
are  situated  upon  the  left 
crus  of  the  diaphragm  and 
their  efferents  also  pierce 
the  crus  to  open  into 
the  thoracic  duct  ;  the  efferents  from  the  remaining  nodes  concerned  unite  with 
those  of  the  other  lateral  lumbar  nodes  to  form  the  lumbar  trunks  which  open 
into  the  receptaculum  chyli. 

The  net-work  which  lies  beneath  the  fibrous  capsule  communicates  with  both  the 
cortical  and  subserous  net-works,  and  its  drainage  is  probably  mainly  through  these  : 
a  few  stems,  however,  pass  toward  the  hilus,  beneath  the  capsule,  and  unite  with 
the  terminal  efferents  from  the  cortical  net-work,  there  being  no  direct  connection 
between  the  net-work  and  the  lumbar  nodes.  The  case  is  different  with  the  subserous 
net-work,  its  efferents  passing  to  the  upper  lateral  lumbar  nodes  quite  independently 
of  the  cortical  efferents.  As  already  noted,  it  has  abundant  communication  with 
the  net-work  beneath  the  fibrous  capsule,  and  through  this  with  the  cortical 
net-work,  so  that  infections  of  the  kidney  tissue  are  readily  communicated  to  the 
adipose  capsule. 

The  lymphatic  net-works  of  the  ureters  appear  to  be  limited  to  the  muscular 
coat  and  the  surface  of  the  ducts  (Sakata).  The  efferents  which  arise  from  the 
upper  portions  of  the  net-works,  that  is  to  say  from  the  portions  above  the  level  at 


Lymphatics  of  kidneys  and  of  ovary 


*Archiv  f.  Anat.  u.  Physiol.,  1900. 


THE    LYMPHATICS    OF    THE    PELVIS. 


983 


Fig.    824. 


which  the  ureter  is  crossed  by  the  spermatic  (ovarian)  artery,  pass  upward  to  unite 

with  the  renal   efferents  or  occasionally  to  terminate  directly  in  the  upper   lateral 

lumbar  nodes   (Fig.  824).      The  majority 

of  the  efferents  arise  from  those  portions  of 

the  ducts  intervening  between  the  crossing 

of   the  spermatic    (ovarian)    arteries    and 

the  level   at  which   the  ureters  cross  the 

common  iliac  vessels  to  enter  the  pelvis, 

and  these  vessels  pass  either  to  the  lower 

lateral  lumbar  nodes,  or  else,  in  the  case 

of    the    lower    ones,    to    the    upper    iliac 

nodes.      Finally,    the    efferents    from    the 

pelvic  portions  of  the  ureters  either  unite 

with  the  vessels  passing  from  the  bladder, 

or  else  communicate  directly  with  certain 

of  the  hypogastric  nodes. 

In  and  beneath  the  fibrous  capsule 
of  the  suprarenal  bodies  a  lymphatic 
net-work  occurs,  whose  efferents  on  the 
one  hand  join  the  renal  lymphatics,  and 
on  the  other  pass  into  the  substance  of 
the  organs  to  communicate  with  a  net- 
work situated  in  the  glomerular  portion 
of  the  cortex.  From  this  latter  net-work 
stems  pass  centrally  in  the  partitions 
between  the  cell  columns  of  the  cortex  to 
unite  with  a  rich  plexus  which  traverses 
all  portions  of  the  medullary  substance. 
The  main  stems  of  this  plexus  follow  the 
course  of  the  suprarenal  blood-vessels  and 
emerge  at  the  hilus  of  the  organ  as  four 
or  five  stems,  which  pass  to  the  upper 
lateral  lumbar  nodes.  Some  of  the  stems  are  also  said  to  pierce  the  crura  of  the 
diaphragm  and  terminate  in  the  lower  nodes  of  the   posterior  mediastinal  group. 


\ 


of  ureters.     (Based  on  several  figur 
by  Sakata.*) 


THE    LYMPHATICS   OF   THE    PELVIS. 
The  Lymph-Nodes. 

The  pelvic  lymphatic  nodes  are  arranged  along  the  courses  of  the  principal 
vessels,  and  may  conveniently  be  divided  into  three  groups,  the  iliac,  the  hypogastric, 
and  the  sacral  nodes.  In  addition  some  small  inconstant  nodes  occur  in  association 
with  the  bladder  and  these  will  be  described  in  connection  with  the  vessels  arising 
from  that  organ  (page  985).  The  epigastric  and  circumflex  iliac  nodes,  already 
described  in  connection  with  the  abdominal  region  (page  972),  are  really  outliers 
of  the  iliac  group. 

The  iliac  nodes  (Fig.  825)  are  from  fifteen  to  twenty  in  number  and  form  a 
plexus  (plexus  iliacus  externus)  along  the  course  of  the  common  and  external  iliac 
vessels,  the  uppermost  nodes  lying  at  the  level  of  the  bifurcation  of  the  aorta  and 
the  lowermost  around  the  point  of  exit  of  the  external  iliac  vessels  beneath  Poupart's 
ligament.  Three  more  or  less  distinct  linear  series  of  nodes  can  be  recognized  in 
the  plexus,  one  of  which,  along  the  course  of  the  common  iliac  artery,  is  situated 
close  to  the  outer  surface  of  the  artery  and  along  the  medial  border  of  the  psoas  muscle. 
The  second  lies  behind  the  artery,  resting  upon  the  anterior  surface  of  the  vein,  while 
the  third  unites  with  its  fellow  of  the  opposite  side  to  form  a  group  of  three  or  four 
nodes  resting  upon  the  left  common  iliac  vein  and  the  promontory  of  the  sacrum 
in  the  angle  formed  by  the  bifurcation  of  the  aorta.  Of  the  series  along  the  line  of 
the  external  iliac  vessels  one  lies  to  the  outer  side  of  the  artery  along  the  medial 

*  Archiv  f.  Anatom.  u.  Physiol.,  1903. 


9§4 


HUMAN    ANATOMY. 


border  of  the  psoas,  the  second  in  the  angle  between  the  vein  and  the  artery,  and 
the  third  along  the  lower  border  of  the  vein,  between  it  and  the  obturator  nerve. 

The  various  nodes  of  the  iliac  set  communicate  with  one  another  so  that  the 
efferents  of  one  node  are  afferents  for  the  higher  ones.  In  addition  they  receive 
afferents  from  the  inguinal  nodes  as  well  as  from  the  epigastric  and  circumflex  iliac 
nodes  as  already  stated,  and  the  group  situated  over  the  promontory  of  the  sacrum 
also  receives  afferents  from  both  the  hypogastric  and  sacral  nodes.  Furthermore, 
afferents  pass  to  the  iliac  nodes  from  the  pelvic  portions  of  the  ureters,  from  the 
bladder  and  prostate  gland,  from  the  lower  portion  of  the  uterus  and  the  upper 
portion  of  the  vagina,  from  the  glans  penis  and  clitoris,  from  the  adductor  muscles 
of  the  thigh  through  vessels  accompanying  the  obturator  artery,  and,  in  the  case  of 
the  lateral  series  of  nodes,  from  the  psoas  muscle  and  the  adjacent  subserous  tissue. 
The  efferents  pass  to  the  lower  lateral  lumbar  nodes. 

The  internal  iliac  or  hypogastric  nodes  ( lymphoglandulae  hypogastricae)  are 
from  nine  to  twelve  in  number  on  each  side,  and  are  situated  on  the  lateral  walls 
of  the  pelvic  cavity,  along  the  course  of  the  internal  iliac  vessel  and  its  branches 


Fig.   825. 


node  of 
promontory  group 


Superficial 

inguinal  nodes 


des.     {Cuneo  and  Marcille.*) 


(Fig.  825).  They  are  connected  together  to  form  a  plexus  (plexus  hypogastricus), 
and  receive  affere?its  from  most  of  the  regions  to  which  the  branches  of  the  internal 
iliac  artery  are  distributed.  Thus  branches  come  to  them  from  all  the  pelvic  organs, 
from  the  deeper  portions  of  the  perineum,  including  the  penial  portion  of  the  urethra, 
from  the  deep  portions  of  the  posterior  and  internal  femoral  and  the  gluteal  regions. 
Their  efferents  pass  mainly  to  the  iliac  nodes  situated  on  the  promontory  of  the 
sacrum,  those  which  arise  from  the  obturator  node,  situated  upon  the  obturator  artery 
as  it  passes  through  the  obturator  foramen,  passing,  however,  to  nodes  belonging  to 
the  inner  series  of  the  group  accompanying  the  external  iliac  vessels. 

The  sacral  nodes  are  situated  on  the  ventral  surface  of  the  sacrum,  partly 
along  the  course  of  the  middle  sacral  vessels,  and  partly  internal  to  the  second  and 
third  anterior  sacral  foramina,  along  the  course  of  the  lateral  sacral  arteries  (Fig.  829). 
All  the  nodes  are  small  and  they  are  united  together  by  lymphatic  vessels  to  form  a 
sacral  plexus  (plexus  sacralis  tnedius).  They  receive  afferents  from  the  neighboring 
muscles  and  from  the  sacrum,  and  their  efferents  pass  to  the  iliac  nodes  situated 
upon  the  promontory  of  the  sacrum. 

The  Lymphatic  Vessels. 
Under  this  heading  will  be  considered  the  vessels  of  the  various  pelvic  organs, 
with   the   exception   of  those  of  the  rectum,    which  have   already  been   described 
(page  979).     In  addition  there  will  be  included  the  vessels  of  the  external  genitalia, 


Bull,  et  Mem.  Socit-te'  anatom.,  1901. 


THE    LYMPHATICS    OF    THE    PELVIS. 


985 


and,  on  account  of  their  intimate  relation  with  these,  the   superficial  lymphatics  of 
the  perineal  and  circumanal  regions. 

The  Bladder. — It  was  for  a  long  time  a  matter  for  discussion  whether  or  not 
the  mucosa  of  the  bladder  was  provided  with  a  lymphatic  net-work,  but  the  general 
consensus  of  recent  observers  is  that  it  is  not.  Only  the  muscular  coat  possesses  a 
net-work,  and  from  this  stems  pass  to  the  surface  of  the  viscus  to  form  a  superficial 
net-work  beneath  the  peritoneal  or  fascial  investment.  This  net-work  is  continuous 
at  the  neck  of  the  bladder  with  those  of  the  urethra  and  prostate  gland,  and,  at  its 
base,  with  the  net-works  of  the  ureters  and  seminal  vesicles,  and,  in  the  female,  of  the 
vagina.  The  efferent  stems  which  take  origin  from  it  may  be  divided  into  two 
groups  according  as  they  arise  upon  the  anterior  or  posterior  surface. 

Those  passing  from  the  lower  part  of  the  anterior  surface  are  directed  laterally 
and  those  from  the  upper  part  pursue  a  flexuous  course  downward  and  laterally  to 
terminate  in  the  nodes  of  the  iliac  group  situated  along  the  external  iliac  vessels 
(Fig.  826).  In  their  course  they  usually  traverse  some  small  nodes  situated  in 
close  proximity  to   the   bladder 

and  divisible  according  to  their  FlG-   826- 

position  into  two  groups.  One 
of  these  is  situated  upon  the 
anterior  surface  of  the  bladder, 
and  consists  of  two  or  three 
nodes,  the  anterior  vesical 
nodes,  two  of  which  are  usually 
situated  near  the  apex  of  the  vis- 
cus in  the  course  of  the  superior 
vesical  artery,  while  the  third 
occurs  lower  down  in  the  retro- 
pubic tissue.  The  other  group 
consists  of  from  two  to  four 
nodes,  the  lateral  vesical 
nodes,  situated  on  either  side 
of  the  bladder  along  the  course 
of  the  obliterated  hypogastric 
arteries.  Both  groups  are  some- 
what inconstant,  but  occur  in  a 
large  percentage  of  cases. 

The  vessels  from  the  upper 
part  of  the  posterior  surface  of 
the  bladder  pass  downward  and 
laterally,  often  traversing  some 
of  the  lateral  vesical  nodes,  and  terminate  in  the  external  iliac  nodes  which  receive 
the  stems  from  the  anterior  surface.  Others  pass  to  the  hypogastric  nodes,  while 
others  again,  arising  from  the  base  of  the  bladder,  pass  at  first  directly  backward 
past  the  lateral  surfaces  of  the  rectum  and  then  ascend  on  the  sacrum  to  terminate 
in  the  iliac  nodes  situated  upon  the  promontory. 

The  Prostate  Gland. — The  lymphatics  of  the  prostate  have  their  origin  in 
net-works  surrounding  the  various  acini  of  the  gland.  From  these  net-works  stems 
pass  to  the  surface,  where  they  form  a  second  net-work,  and  from  this  the  efferent 
stems  pass  symmetrically  on  either  side  of  the  median  line  to  somewhat  diverse 
terminations.  One  or  two  of  the  efferents  on  either  side  ascend  in  a  tortuous  course 
upon  the  posterior  surface  of  the  bladder,  and  then  bend  laterally  over  the  obliterated 
hypogastric  arteries  to  terminate  in  one  of  the  middle  series  of  the  iliac  nodes 
which  accompany  the  external  iliac  vessels.  Another  stem  passes  backward  along 
the  prostatic  vessels  to  terminate  in  one  of  the  hypogastric  nodes  ;  others  pass  at  first 
backward  on  either  side  of  the  rectum,  and  then  ascend  upon  the  anterior  surface 
of  the  sacrum  to  terminate  in  the  lateral  sacral  nodes  or  in  the  iliac  nodes  situated 
on  the  promontory  of  the  sacrum  ;   and  from  the  anterior  surface  of  the  gland  a  stem 


Lymph 


*  Archiv  f.  Anatom.  u.  Physiol.,  1897. 


HUMAN    ANATOMY. 


passes  downward  on  either  side  of  the  membranous  portion  of  the  urethra,  and, 
accompanying  the  urethral  lymphatics  along  the  course  of  the  internal  pudic  vessels, 
terminates  in  one  of  the  hypogastric  nodes  situated  upon  these  vessels. 

The  Urethra. — The  mucous  membrane  of  the  male  urethra  is  furnished 
throughout  its  entire  extent  with  a  lymphatic  net-work,  which  is  especially  rich  in 
the  region  of  the  glans  and  diminishes  in  complexity  in  the  membranous  and 
prostatic  portions  of  the  duct.  In  the  last  region  it  communicates  with  the  net-work 
in  the  muscular  coat  of  the  neck  of  the  bladder.  The  efferents  from  the  membranous 
portion  of  the  duct  associate  themselves  with  some  of  the  prostatic  efferents  and  pass 
to  a  hypogastric  node  situated  on  the  course  of  the  internal  pudic  vessels,  and  those 
from  the  penial  portion  accompany  the  vessels  which  arise  from  the  glans  and  will 
be  described  in  the  account  of  the  lymphatics  of  the  penis.  The  net-work  of  the 
female  urethra  corresponds  with  those  of  the  membranous  and  prostatic  portions  of 
the  male  duct. 

The  External  Reproductive  Organs  in  the  Male. — The  lymphatics  of  the 
scrotum  form  an  exceedingly  rich  net-work,  especially  well  developed  in  the  vicinity 
of  the  raphe  and  thence  extending  laterally  over  the  entire  surface.      From  six  to 

eight    stems    arise    from 
FlG-   827-  this    net-work,    and    the 

uppermost  accompany 
and  eventually  anasto- 
mose with  the  superficial 
efferents  from  the  penis 
and  terminate  in  the  in- 
ner inguinal  nodes.  The 
remaining  stems  pass 
upward  and  outward  to 
terminate  in  the  inner 
superficial  subinguinal 
nodes. 

The  lymphatics  of 
the  penis  are  divisible 
into  a  superficial  and  a 
deep  set  which  correspond 
respectively  to  the  super- 
ficial and  deep  blood- 
vessels of  the  organ.  The 
superficial  set  forms  a 
net-work  in  the  integu- 
ment of  the  penis  which 
radiates  in  all  directions 
from  the  frenulum,  some 
stems  passing  forward  and 
upward  into  the  prepuce  and  some  especially  strong  stems  passing  dorsally  in  the 
furrow  behind  the  corona  of  the  glans.  As  they  approach  the  dorsal  mid-line  these 
latter  give  off  one  or  two  longitudinally  directed  efferents,  or  else  they  unite  to  form 
a  single  stem  which  runs  along  the  dorsal  mid-line.  Other  stems  arising  from  the 
more  proximal  portions  of  the  net-work  curve  upward  from  below  over  the  lateral 
surfaces  of  the  penis,  and  either  unite  with  the  dorsal  stems  or  form  independent 
lateral  stems  parallel  with  the  dorsal  ones.  Numerous  anastomoses  occur  between 
all  the  longitudinal  stems  throughout  their  courses,  and,  as  they  approach  the 
symphysis,  they  bend  laterally,  some  indeed  dividing  to  send  branches  to  either 
side,  and,  after  the  upper  stems  from  the  scrotum  have  united  with  them,  they 
terminate  in  the  inner  inguinal  nodes. 

The  deep  set  forms  a  net-work  especially  well  developed  in  the  glans,  in  which 
a  superficial  and  a  deep  layer  may  be  distinguished.  Both  these  layers  communicate 
at  the  meatus  with  the  urethral  net-work,  and  from  the  deeper  layer  a  special  plexus 


Superficial  lymphatic  vessels  of  penis  and  scroti! 
nodes.     (Brulins.*) 


'  Archiv  f.  Anat.  u.  Physiol.,  1900. 


THE    LYMPHATICS    OF    THE    PELVIS.  987 

is  developed  on  either  side  of  the  frenulum  (Pauzzsa's  plexus*),  from  which  stems 
ascend  in  the  groove  back  of  the  corona  glandis.  Into  these  stems  the  superficial 
layer  of  the  net-work  opens,  and  they  also  receive  communications  from  the  super- 
ficial vessels  of  the  penis.  From  them  one  or  two  stems  arise  which  pass  proximally 
in  company. with  the  dorsal  vein  of  the  penis' toward  the  suspensory  ligament.  Here 
they  usually  divide  to  form  a  more  or  less  distinct  plexus,  lying  immediately  over 
the  symphysis  pubis  and  provided  with  some  small  lymphatic  nodes,  and  from  it  two 
or  three  stems  pass  off  laterally  on  either  side.  These  pass  across  the  surface  of  the 
pectineus  muscle  and  beneath  the  spermatic  cord,  and  some  then  pass  either  to  the 
inner  inguinal  or  deep  subinguinal  glands,  while  others  extend  along  Poupart's 
ligament  to  the  external  abdominal  ring  and,  traversing  the  inguinal  canal,  terminate 
in  one  of  the  lower  iliac  nodes. 

It  is  to  be  noted  that  owing  to  the  anastomoses  and  bifurcations  of  both  the 
superficial  and  deep  longitudinal  stems  it  is  possible  that  a  unilateral  infection  may 
cause  enlargment  of  the  nodes  of  both  sides. 

The  External  Reproductive  Organs  in  the  Female. — The  lymphatics  of 
the  external  female  genitalia  have  essentially  the  same  distribution  as  those  of  the 
corresponding  organs  in  the  male.  In  both  the  labia  majora  and  minora  rich 
subcutaneous  net-works  occur,  from  which  numerous  stems  arise  and  pass  to  the  inner- 
most inguinal  and  occasionally  the  inner  superficial  subinguinal  nodes.  The  stems 
from  the  upper  parts  of  the  labia  ascend  at  first  directly  upward  toward  the  mons 
veneris  and  then  bend  suddenly  outward  to  reach  their  terminal  nodes  ;  those  from 
the  lower  parts  pass  either  directly  upward  and  outward  or  else  at  first  directly 
upward  parallel  to  the  outer  edges  of  the  labia  and  then  bend  suddenly  outward. 
Some  of  the  stems  coming  from  one  or  other  of  the  labia  may  pass  to  the  nodes  of 
the  opposite  side,  and,  furthermore,  communications  exist  through  the  anterior  and 
posterior  commissures  between  the  net- works  of  the  opposite  labia,  so  that  a  unilateral 
infection  may  produce  enlargement  of  the  inguinal  nodes  on  both  sides. 

The  lymphatics  of  the  clitoris  present  essentially  the  same  arrangement  as  the 
deep  lymphatics  of  the  penis.  They  form  a  rich  net-work  in  the  glans  and  from  this 
longitudinal  stems  arise  and  pass  toward  the  symphysis  pubis,  in  front  of  which  they 
form  a  plexus  which  usually  contains  some  small  nodes.  From  the  plexus  stems 
arise  which  pass  laterally,  and  terminate  either  in  one  of  the  deep  subinguinal  nodes 
or  else  in  the  lower  iliac  nodes,  which  they  reach  by  traversing  the  inguinal  canal. 

The  Perineum  and  Circumanal  Regions. — The  deeper  lymphatics  of  these 
regions  have  been  considered  in  connection  with  the  organs  to  which  they  belong 
and  there  remain  for  consideration  only  the  subcutaneous  vessels.  These  in  the 
perineal  region  form  an  abundant  net-work  from  which  stems  pass  forward,  for  the 
most  part  in  the  furrow  between  the  perineum  and  the  inner  surface  of  the  thigh, 
and,  associating  themselves  with  the  stems  from  the  scrotum  or  labia  majora, 
terminate  in  the  inner  inguinal  or  superficial  subinguinal  nodes. 

The  subcutaneous  lymphatics  which  surround  the  anal  opening  also  form  a  rich 
net-work,  which  communicates  extensively  with  that  of  the  anal  mucosa  (page  979). 
From  it  some  two  or  three  stems  pass  forward  along  the  inner  side  of  the  thigh  to 
terminate  with  the  perineal  and  scrotal   (labial)  stems  in  the  inner  inguinal  nodes. 

The  Internal  Reproductive  Organs  in  the  Male. — The  testis  possesses  an 
abundant  supply  of  lymphatics,  which  may  be  divided  into  a  deep  and  a  superficial  set. 
The  former  takes  its  origin  in  a  rich  net-work  which  surrounds  the  seminal  ducts,  and 
the  stems  which  compose  it  pass  toward  the  hilum  in  the  septa,  and,  issuing,  associate 
themselves  with  the  stems  arising  from  the  superficial  net-work.  This  is  double,  one 
layer  of  it  lying  beneath  the  tunica  albuginea  and  the  other  between  that  investment 
and  the  visceral  layer  of  the  tunica  vaginalis.  Both  layers  are  abundantly  connected  bv 
vessels  which  traverse  the  tunica  albuginea,  and  the  deeper  layer  also  receives  numer- 
ous communicating  stems  from  the  deep  lymphatics  and  from  the  lymphatics  of  the 
epididymis.  Collecting  stems  from  both  layers  converge  toward  the  hilum,  where  they 
become  associated  with  the  stems  from  the  deep  net-work,  from  six  to  eight  or  rarely 
more  trunks  which  ascend  along  the  spermatic  cord  to  the  internal  abdominal  ring. 
They  then  follow  the  course  of  the  spermatic  veins  upward,  and  terminate  in  from  two 
to  four  of  the  lateral  lumbar  nodes  (Fig.  816).     The  nodes  to  which  the  vessels  from 


988  HUMAN    ANATOMY. 

the  left  testis  pass  lie  immediately  beneath  the  level  of  the  renal  veins,  while  those 
in  which  the  stems  from  the  right  testis  terminate  are  lower,  being  situated  about 
midway  between  the  level  of  the  renal  vein  and  the  junction  of  the  common  iliac  veins. 

The  lymphatics  of  the  vas  deferens  are  probably  arranged  in  two  net-works, 
one  belonging  to  the  mucosa  and  the  other  to  the  muscular  coat,  although  so  far  only 
the  latter  net-work  has  been  demonstrated.  At  the  testicular  end  of  the  duct  the 
net-work  communicates  with  that  of  the  epididymis,  and  the  stems  which  arise  from 
it  accompany  those  of  the  testis  to  the  lateral  lumbar  nodes.  At  the  vesical  end 
the  net-work  communicates  with  that  of  the  seminal  vesicles  and  its  efferents  pass 
to  one  of  the  hypogastric  nodes. 

The  lymphatics  of  the  seminal  vesicles  are  much  more  readily  demonstrable 
than  those  of  the  vasa  deferentia.  They  arise  from  two  net-works,  one  of  which  is 
situated  in  the  mucosa  and  the  other  in  the  muscularis.  Stems  from  the  latter  form 
a  third  net-work  over  the  surfaces  of  the  vesicles  and  from  this  efferents,  two  or  three 
in  number,  pass  to  some  of  the  hypogastric  nodes. 

The  Internal  Reproductive  Organs  in  the  Female. — The  lymphatics  of 
the  ovary  are  very  abundant  throughout  the  substance  of  the  organ,  a  fine  net-work 


Lateral  lumbar  node 


Lymphatic 
Vessels  from  body  and 
cervix  of  uterus 


Lymphatic  vessels 
from  ovary  and 
upper  part  of  uterus 


-Fallopian  tube 


Lymphatics  of  internal  reproductive  organs  of  female.     (Poirier*) 


surrounding  each  of  the  Graafian  follicles.  The  stems  which  arise  from  these  net- 
works converge  toward  the  hilus,  where  they  form  a  rich  plexus  and  from  this  from 
six  to  eight  efferents  arise  and  follow  the  ovarian  blood-vessels  to  terminate  in  the 
lateral  lumbar  nodes  (Fig.  828). 

Owing  to  thinness  of  the  walls  it  is  difficult  to  distinguish  a  definitely  layered 
arrangement  of  the  lymphatic  net-work  of  the  Fallopian  tubes.  It  is,  however, 
rich,  and  communicates  with  that  of  the  fundus  of  the  uterus.  It  gives  rise  to  two  or 
three  efferents  which  accompany  the  ovarian  efferents  to  the  lateral  lumbar  nodes. 


*Progres  Medical,  1890. 


THE    LYMPHATICS    OF    THE    PELVIS. 


Iliac  node  of 
promontory 
group 


In  the  uterus  (Figs.  828,  829)  the  conditions  are  much  more  favorable  for 
determining  the  existence  of  separate  net-works  in  the  mucosa  and  muscularis  than 
in  the  Fallopian  tubes,  but,  nevertheless,  much  difference  of  opinion  exists  as  to  the 
occurrence  of  a  mucosa  net-work.  That  of  the  muscularis  can  be  injected  without 
difficulty,  but  no  conclusive  injections  have  yet  been  made  of  the  mucosa,  and  while 
some  authors  (Bruhns,  Sappey,  Poirier)  are  inclined  to  admit  the  existence  of  a 
net- work  in  it,  others  (Leopold)  deny  it.  However  that  may  be,  a  well-developed 
net-work  occurs  in  the  muscular  coat,  in  the  deeper  portions  of  which  it  becomes 
especially  rich,  and,  furthermore,  it  is  more  abundant  in  the  cervix  than  in  the  body 
or  fundus.  From  it  stems  pass  to  the  surface  of  the  organ  to  form  a  subserous 
net-work,  from  which  a  number  of  efferents  arise. 

These  may  be  divided  into  three  principal  groups  according  to  their  termina- 
tions. ( 1 )  The  efferents  from  the  fundus,  usually  two  in  number,  pass  outward  on 
either  side  in  the  upper  portion  of  the  broad  ligament,  and,  associating  themselves 
with  the  efferents  from  the  ovary,  terminate  in  the  lateral  lumbar  nodes.  (2)  Small 
stems  pass  from  the  fundus  aiong  the  round  ligament  of  the  uterus  to  terminate  in  the 
inguinal  nodes.  (3)  The 
efferents  from  the  body 
and  cervix  pass  laterally 
to  terminate  in  the  median 
iliac  nodes  situated  in  the 
angle  between  the  external 
and  internal  iliac  arteries. 
In  the  course  of  these  last 
vessels,  at  the  point  where 
they  cross  the  ureter,  a 
small  utero-vaginal  node 
is  occasionally  placed. 

Other  efferents  have 
been  described  as  passing 
from  the  cervix  to  a  hypo- 
gastric node  situated  at 
the  origin  of  the  uterine  or 
vaginal  artery,  and  two  or 
three  stems  have  been 
found  arising  from  the 
posterior  surface  of  the 
cervix  and  passing  back- 
ward on  either  side  of 
the  rectum  to  the  anterior 
surface  of  the  sacrum, 
up  which  they  pass  to 
terminate   in   the    iliac    nodes    situated   upon   the    sacral    promontory    (Fig.    829). 

In  the  vagina  there  is  no  question  as  to  the  existence  of  definite  net-works  in 
both  the  mucosa  and  muscularis.  That  of  the  mucosa  (Fig.  830)  is  exceptionally 
fine  and  communicates  abundantly  with  the  coarser  net-work  of  the  muscularis,  as 
well  as  with  the  net-work  of  the  vaginal  portion  of  the  cervix  above  and  with  that  of 
the  labia  minora  below.  From  the  muscularis  net-work  stems  pass  to  the  surface 
of  the  organ  to  form  a  third  net-work,  from  which  the  main  efferent  stems  arise, 
and  these  may  be  arranged  in  three  groups  according  to  their  destinations:  (1) 
those  which  arise  from  the  upper  portion  of  the  vagina  join  the  stems  which  pass 
from  the  cervix  of  the  uterus  (Fig.  830)  and  terminate  with  these  in  the  median 
iliac  nodes  situated  in  the  angle  formed  by  the  external  and  internal  iliac  arteries  ; 
(2)  those  arising  from  the  ?niddle  portion  accompany  the  vaginal  vessels,  passing 
obliquely  upward,  outward,  and  backward,  to  terminate  in  one  or  two  hypogastric 
nodes  situated  at  the  origin  of  the  uterine  arteries  ;  and  (3)  those  from  the  lower 
portion  associate  themselves  with  those  from  the  labia  minora  and  terminate  with  these 


Lymphatics  of  uterus.     (Cutieo 


*Bull.  et  Mem.  Socieke'  anatom.,  1902 


99Q 


HUMAN    ANATOMY. 


Lymphatic  net-work  of  vaginal 


in  the  inner  inguinal  nodes.    Certain  of  the  stems  from  the  middle  portion  also  pass  to 
the  same  middle  iliac  nodes  which  receive  the  efferents  from  the  upper  portion,  and 

stems    have    been    observed 
Fig.  830.  (Bruhns)    passing  from  the 

posterior  surface  of  the  vagi- 
na to  the  lateral  lumbar  nodes 
and  even  to  the  iliac  nodes 
situated  on  the  promontory 
of  the  sacrum,  while  others 
have  been  traced  to  the 
anorectal  nodes  (page  976). 
Finally,  it  may  be  noted 
that  the  superficial  net-work 
of  the  anterior  surface  of  the 
vagina  communicates  with 
that  of  the  posterior  surface 
of  the  bladder. 

Practical  Considera- 
tions.—  The  Lymph-Nodes 
of  the  Abdomen  and  Pelvis. 
— The  superficial  lymphatics 
of  the  wall  of  the  abdomen 
convey  infection,  if  the  pri- 
mary focus  is  above  the  level 
of  the  umbilicus,  to  the  axil- 
lary nodes  ;  if  it  is  below  that 
level,  to  the  inguinal  nodes. 
Hence,  in  cases  of  furuncle  or  carbuncle,  or  of  chancre,  or  of  epithelioma,  the  site 
of  the  lesion  would  determine  the  region  in  which  adenopathy  should  be  sought. 
The  cceliac  group  of  nodes  may  be  involved  in  diseases  of  the  greater  portion  of 
the  digestive  tract,  or  of  the  stomach,  spleen,  or  part  of  the  liver  ;  or  their  enlarge- 
ment may  follow  that  of  the  lumbar  or  of  the  mesenteric  nodes.  The  nodes  in  and 
about  the  portal  fissure,  or  between  the  layers  of  the  gastro-hepatic  omentum  may  so 
enlarge  in  cases  of  carcinoma  of  the  stomach  or  of  the  liver  as  to  compress  the  portal 
vein  (causing  ascites)  or  the  common  bile  duct  (causing  jaundice). 

The  lymphatic  relations  of  the  stomach,  liver,  spleen,  and  pancreas  have  been 
sufficiently  considered  from  the  practical  stand-point  in  connection  with  these  viscera. 
The  mesenteric  nodes  are  frequently  and  gravely  involved  in  various  intestinal 
diseases.  They  are  often  infected  and  enlarged  during  typhoid  fever.  They  are 
especially  implicated  in  peritoneal  or  intestinal  tuberculosis.  The  lymphoid  nodules 
in  the  neighborhood  of  Peyer's  patches  are  surrounded  by  lymphatic  plexuses  and 
are  a  common  site  of  tuberculous  ulceration.  The  bacilli  tuberculosis  are  carried 
directly  thence  to  the  mesenteric  glands  (tabes  mesenterica),  and  sometimes  by  way 
of  the  lymphatic  vessels  and  thoracic  duct,  may  reach  the  general  circulation  in  large 
numbers  (generalized  tuberculosis,  acute  miliary  tuberculosis).  In  some  cases  of 
tuberculous  peritonitis  associated  with  mesenteric  gland  disease,  the  mesentery 
undergoes  marked  and  extreme  contraction,  so  that  the  altered  coils  of  intestine  are 
held  closely  to  the  spine,  and  their  lumen  may  be  greatly  narrowed  (peritonitis 
deformans)  (Taylor). 

Mesenteric  cysts  (serous  or  chylous  cysts)  are  usually  of  lymphatic  origin,  and 
may  be  due  to  lymphatic  obstruction  or  to  a  degeneration  and  dilatation  of  the  mes- 
enteric nodes  analogous  to  the  varicosity  of  inguinal  nodes  in  filarial  disease.  The 
clinical  signs  of  such  cysts  are  :  1,  a  prominent,  fluctuating,  usually  spherical  swell- 
ing near  the  umbilicus  ;  2,  marked  mobility  of  the  tumor — especially  in  a  transverse 
direction  and  around  the  central  axis  ;  3,  the  presence  of  a  zone  of  resonance  around 
the  cyst  and  a  belt  of  resonance  across  it   (Moynihan).      The  symptoms  may  be 


■Progres  medical,  1890. 


THE    LYMPHATICS    OF    THE    LOWER    EXTREMITY.  991 

either  (a)  chronic,  of  the  nature  of  colicky  pain  due  to  interference  with  the  intes- 
tine and  to  gastro-intestinal  disturbance,  the  presence  of  a  tumor  distinguishing  the 
case  from  one  of  simple  gastro-enteritis  ;  or  (b)  those  of  acute  intestinal  obstruction 
(Rolleston). 

The  lumbar  nodes  may  be  enlarged  from  septic  or  malignant  disease  of  the 
lower  extremities,  the  testes,  the  fundus  of  the  uterus,  the  ovary,  the  kidneys  and 
adrenals,  the  sigmoid  or  rectum.  The  wide  area  thus  drained  by  them  exposes 
them  frequently  to  transmitted  infection  or  disease.  Their  condition  in  the  presence 
of  carcinoma  affecting  any  of  these  regions  or  viscera  has  an  important  practical 
bearing  upon  the  question  of  operative  interference,  as,  practically  without  excep- 
tion, if  they  are  involved  only  palliation  can  be  hoped  for.  With  an  empty  intes- 
tinal tract  and  a  thoroughly  relaxed  abdomen,  even  moderate  enlargement  of  these 
nodes  may,  in  thin  persons,  be  detected  by  palpation.  In  persons  with  very  mus- 
cular or  very  fat  abdominal  walls,  they  cannot  be  felt  until  they  have  formed  a  con- 
siderable mass.  Their  great  enlargement — especially  in  carcinoma — often  results  in 
swelling  and  cedema  of  the  lower  extremities  on  account  of  the  obstruction  to  the 
current  in  the  inferior  cava  produced  by  the  pressure  of  the  dense  indurated  glands 
which  may  quite  encircle  both  that  vessel  and  the  aorta  and  may  even  interfere  with 
the  circulation  in  the  latter. 

The  lumbar  nodes  often  enlarge  consecutively  to  enlargement  of  the  pelvic  nodes 
(obturator,  gluteal,  sciatic,  internal  pudic,  external  and  internal  iliacs),  some  of  which 
are  also  palpable — in  thin  persons — when  the  subject  of  carcinomatous  infiltration. 
The  external  iliac  nodes,  for  example,  lying  along  the  anterior  and  inner  aspect  of  the 
external  iliac  vessels,  may,  when  cancerous,  be  recognizable  in  this  way,  and  may 
be  found  by  their  tenderness — though  less  distinctly  felt — in  some  septic  cases.  As 
they  receive  the  lymphatic  vessels  from  the  nodes  of  the  groin,  and  the  vessels 
accompanying  the  deep  circumflex  iliac  arteries,  their  enlargement  may  follow  that 
of  the  inguinal  nodes,  or  may  result  from  septic  or  syphilitic  or  cancerous  foci  in  the 
supra-inguinal  portion  of  the  abdominal  wall.  In  cancer  of  the  testis  the  iliac  and 
lumbar  nodes  are  in  the  closest  relation  to  the  ascending  current  of  lymph,  the 
inguinal  nodes,  as  a  rule,  being  involved  later,  after  the  skin  of  the  scrotum  has 
become  infiltrated  or  ulcerated.  In  advanced  cases  of  carcinoma  of  the  rectum  or 
uterus,  the  obturator,  epigastric  and  external  iliac  groups  become  considerably 
affected.  CEdema  of  the  legs  often  results  because  (a)  the  enlarged  nodes  press 
directly  upon  the  external  iliac  vessels  ;  and  (b)  the  lymphatics  pass  both  over  and 
under  these  vessels  to  communicate  with  the  obturator  node  and  thus  compress  the 
vein  in  a  ring-like  carcinomatous  mass  (Leaf).  The  pain  felt  in  these  cases  is  due 
to  the  pressure  of  the  affected  glands  upon  the  nerve-trunks  arising  from  the  lumbo- 
sacral plexus.  Similar  pains  may  be  felt  when  any  of  the  pelvic  glands  are  involved 
as  there  is  a  similarly  close  relation  between  the  obturator  node  and  the  obturator 
nerve  ;  the  gluteal,  sciatic,  and  internal  pudic  nodes  and  the  first  and  second  sacral 
and  great  sciatic  nerves  ;  and  the  external  iliac  nodes  and  the  anterior  crural 
nerve.  The  obturator  group  of  nodes  lying  between  the  external  iliac  vein  and  the 
obturator  nerve  assume  surgical  importance  because  sometimes  the  lowest  node  of 
this  group  is  found  projecting  through  the  crural  canal.  The  relation  of  this  node  to 
Gimbernat's  ligament  shows  that  when  enlarged  it  would  appear  as  a  swelling  occu- 
pying a  position  similar  to  that  of  a  femoral  hernia  (Leaf).  Cases  are  on  record 
(White)  in  which  an  inflammation  of  this  node  has  simulated  a  strangulated  femoral 
hernia. 

THE  LYMPHATICS  OF  THE  LOWER  EXTREMITY. 
The  Lymphatic  Nodes. 

The  Inguinal  Nodes. — The  principal  group  of  nodes  of  the  lower  extremity 
is  situated  in  the  inguinal  region  over  Scarpa's  triangle,  where  they  form  a  consider- 
able mass,  placed  for  the  most  part  between  the  layers  of  the  fascia  lata,  and  consist 
of  from  twelve  to  twenty  nodes  united  by  connecting  branches  to  form  a  plexus,  the 
plexus  inguinalis.  Though  in  reality  forming  a  single  group,  they  have  been 
divided  for  purposes  of  description  into  a  number  of  subordinate  groups  which  must 
be  recognized  to  have  merely  a  conventional  value.      The  first  of  these  divisions  is  a 


y92 


HUMAN    ANATOMY. 


Fig.  831. 


separation  of  the  nodes  which  lie  respectively  above  and  below  a  horizontal  line 
drawn  through  the  point  at  which  the  long  saphenous  vein  pierces  the  cribriform 
fascia,  and  to  those  lying  above  this  line  the  term  inguinal  nodes  (lymphoglandulae 
inguinales)  is  applied,  while  those  below  it  are  termed  the  subinguinal  nodes 
(lymphoglandulae  subinguinales).  This  latter  subgroup  is  again  divided  into  a  super- 
ficial (lymphoglandulae  subinguinales  superficiales)  and  a  deep  (lymphoglandulae  sub- 
inguinales profundae)  set,  according  as  they  are  situated  on  or  beneath  the  fascia  lata. 
Finally,  by  means  of  a  vertical  line  passing  through  the  orifice  in  the  cribriform  fascia 
through  which  the  long  saphenous  vein  passes,  the  inguinal  and  superficial  subinguinal 
groups  are  each  subdivided  into  an  inner  and  an  outer  set,  a  small  central  group  of 
nodes,  surrounding  the  saphenous  orifice,  being  also  sometimes  recognizable.  It 
may,  however,  again  be  emphasized  that  these  subdivisions  are  purely  conventional 
and  cannot  always  be  clearly  distinguished,  nor  do  they  represent,  except  in  a  very 
general  way,  the  terminations  of  definite  drainage 
areas.  Indeed,  the  numerous  connections  which 
exist  between  the  nodes  of  the  various  subgroups 
cause  their  distinction  to  be  of  comparatively  little 
importance  from  the  surgical  stand-point. 

The  inguinal  nodes  are  arranged  in  a  more 
or  less  distinct  chain  over  the  base  of  Scarpa's 
triangle,  immediately  below  Poupart's  ligament. 
They  receive  as  afferents  the  superficial  lymphatics 
of  the  abdominal  walls  and  the  gluteal  region,  the 
superficial  vessels  of  the  scrotum  and  penis  in  the 
male  and  of  the  labia  majora  and  minora  in  the 
female,  as  well  as  those  from  the  perineum  and 
the  circumanal  region.  Their  efferents  perforate  the 
cribriform  fascia,  enter  the  abdomen  by  the  femoral 
ring,  and  terminate  in  the  lower  iliac  nodes. 

The  superficial  subinguinal  nodes  receive 
some  afferents  from  the  gluteal  regions  and  also 
some  from  the  perineum  and  circumanal  regions,  but 
the  principal  set  is  formed  by  the  superficial  vessels 
of  the  leg.  Their  efferents  have  essentially  the 
same  course  as  those  of  the  inguinal  nodes,  piercing 
the  cribriform  fascia  to  accompany  the  femora] 
vessels  to  the  abdomen,  where  they  terminate  in  the 
lower  iliac  nodes.  In  their  course  through  the 
femoral  sheath  some  of  them  lie  on  the  anterior 
surface  of  the  vessels,  but  the  majority  lie  on  their 
inner  side  in  the  crural  canal  and  some  of  them 
terminate  in  the  deep  subinguinal  nodes. 

The  deep  subinguinal  nodes  vary  in  number 
from  one  to  three.  They  are  placed  along  the 
course  of  the  femoral  vein,  one  occurring  immediately  beneath  the  point  of  junction 
of  the  long  saphenous  vein  with  the  femoral,  a  second  a  little  higher  up  in  the  crural 
canal,  and  the  third,  termed  by  French  authors  the  node  of  Cloquet  and  by  the 
Germans  the  node  of  Rosenmiiller,  is  situated  at  the  entrance  into  the  crural  canal 
from  the  abdomen.  Their  principal  afferents  are  the  deep  lymphatics  of  the  thigh 
which  accompany  the  femoral  vessels  and  their  branches,  but  in  addition  they  receive 
stems  from  the  superficial  subinguinal  nodes  and  the  deep  vessels  of  the  penis  and 
clitoris.  Their  efferents  pass,  like  those  of  the  superficial  nodes,  to  the  lower  iliac 
nodes. 

The  popliteal  nodes  (lymphoglandulae  popliteae)  are  some  four  or  more  in 
number  and  are  embedded  in  the  adipose  tissue  of  the  popliteal  space  (Fig.  832). 
One  or  two  occur  in  the  neighborhood  of  the  short  saphenous  vein  immediately 
after  it  has  entered  the  popliteal  space,  while  the  rest  are  situated  more  deeply  upon 
the  popliteal  vessels.  The  more  superficial  nodes  receive  as  afferents  the  superficial 
lymphatics  of  the  leg  which  accompany  the  short  saphenous  vein,  while  the  deeper 


Superficial 
izontal    line 
upper  and   low 


^uinal  lymph-nodes; 
bdivides  nodes  into 
groups ;    vertical  lit 


into  median  and  lateral  groups. 


THE    LYMPHATICS    OF   THE    LOWER    EXTREMITY. 


993 


Popliteal  1 


ones  receive  the  vessels  which  accompany  the  branches  of  the  popliteal  vessels  and 

also  those  accompanying  the  anterior  and  posterior  tibial  vessels.      Their  efferents  for 

the    most    part    accompany   the 

femoral    vessels   to  terminate  in  Fig.  S32. 

the  deep  subinguinal  nodes. 

The  anterior  tibial  node 
(lymphoglandula  tibialis  anterior) 
is  a  small  and  probably  inconstant 
node  situated  in  the  upper  part 
of  the  course  of  the  lymphatic 
vessels  which  accompany  the 
anterior  tibial  artery.  Its  effer- 
ents pass  upward  along  with 
the  anterior  tibial  and  popliteal 
blood-vessels  to  terminate  in  the 
deeper  popliteal  nodes. 

The  Lymphatic  Vessels. 

The  lymphatic  vessels  of  the 
lower  extremity  may  be  divided 
into  two  groups,  one  of  which 
consists  of  the  subcutaneous  net- 
work and  its  efferent  stems  and 
the  other  of  those  vessels  which 
accompany  the  principal  blood- 
vessels. 

The  superficial  lymphat- 
ics take  their  origin  from  a 
net-work  distributed  throughout  all  portions  of  the  subcutaneous  tissue  of  the 
extremity,  but  increasing  in  richness  and  complexity  toward  the  distal  part  of  the 
limb,  until  in  the  foot,  and  especially  in  the  plantar  region,  it  forms  a  very  close  and 
abundant  net-work.  This  plantar  net-work  extends  not  only  throughout  the  entire 
plantar  region,  but  curves  dorsally  upon  both  the  outer  and  inner  borders  of  the  foot, 
and  also  over  the  posterior  surface  of  the  heel,  and  from  these  lateral  and  posterior 
portions  of  the  net-work  as  well  as  from  the  subcutaneous  net-work  of  the  digits 
numerous  collecting  stems  arise.  These  anastomose  abundantly,  and  those  from  the 
digits,  the  whole  of  the  inner  border  of  the  foot  and  the  distal  half  of  its  outer  border 
form  an  open  plexus  upon  the  dorsum  of  the  foot.  The  stems,  several  in  number, 
which  arise  from  this  plexus  pass  upward  along  the  inner  surface  of  .the  leg 
(Fig.  833),  following  in  general  the  course  of  the  long  saphenous  vein  and  receiving 
as  they  go  communications  from  the  superficial  net-works  of  the  regions  they 
traverse.  In  the  neighborhood  of  the  knee  stems  arising  from  the  net-work  over 
the  anterior  tibial  region  become  associated  with  them,  and  above  the  knee  branches 
which  drain  the  net-work  of  the  outer,  inner,  and  posterior  surfaces  of  the  thigh  also 
curve  upward  and  inward  or  forward,  as  the  case  may  be,  to  accompany  them. 
The  numerous  stems  so  formed  are  all  situated  superficially  to  the  fascia  lata,  and 
terminate  above  in  the  superficial  subinguinal  nodes,  the  more  anterior  stems  passing 
to  the  outer  and  the  more  posterior  to  the  inner  members  of  the  group. 

The  stems  which  arise  from  the  calcaneal  portion  of  the  plantar  net-work  and 
from  that  portion  of  it  which  curves  upward  over  the  posterior  half  of  the  outer 
border  of  the  foot,  pass  upward  upon  the  posterior  surface  of  the  crus  in  company 
with  the  short  saphenous  vein.  They  receive  communications  from  the  superficial 
net-work  of  the  calf  and,  as  they  approach  the  bend  of  the  knee,  they  perforate  the 
crural  fascia  and  terminate  in  the  more  superficial  popliteal  nodes. 

Finally,  from  the  net-work  over  the  gluteal  region  a  number  of  collecting  stems 
arise,  the  majority  of  which  curve  forward  and  converge  to  terminate  in  the  outer 
inguinal  nodes,  some  from  the  more  posterior  portions  of  the  net-work,  however, 

*Poirier  et  Charpy  :  Traits  d'anatomie  humaine,  Tome  ii.,  1902 
63 


994 


HUMAN    ANATOMY. 


Fig.  S33. 


passing  forward  along  with  the  stems  from  the  circumanal    region  to  the  inner 
inguinal  or  superficial  subinguinal  nodes. 

The  deep  lymphatics  of  the  lower  extremity  take  their  origin  mainly  in  the 
muscles  and  form  stems  which  accompany  the  blood-vessels.  From  the  net-work 
of  the  plantar  muscles  one  or  two  stems  take  origin  which  follow  the  course  of  the 
plantar  arch,  ascending  to  the  dorsum  of  the  foot  between  the  first  and  second 
metatarsal  bones.  They  then  follow  the  course  of  the  dorsal  pedal  vessels,  receiving 
the  stems  which  accompany  their  branches,  and  then  accompany  the  anterior  tibial 
vessels  up  the  leg.  After  traversing  the  anterior  tibial 
nodes  they  pass  with  the  vessels  through  the  foramen  in 
the  interosseous  membrane,  and,  continuing  their  upward 
course  through  the  popliteal  space,  terminate  in  the 
deeper  popliteal  nodes. 

Other  branches  arising  in  the  plantar  musculature 
follow  the  plantar  vessels  backward,  and,  ascending 
behind  the  internal  malleolus,  accompany  the  posterior 
tibial  vessels.  Toward  the  upper  part  of  the  crus  they 
receive  the  stems  which  accompany  the  peroneal  vessels 
and  their  branches,  and  terminate,  like  the  anterior 
stems,  in  the  deeper  popliteal  nodes. 

From  these  nodes  four  large  stems  issue,  and, 
passing  through  the  hiatus  tendineus  of  the  adductor 
magnus,  continue  their  course  up  the  thigh  in  company 
with  the  femoral  vessels.  They  receive  the  stems  which 
accompany  the  various  branches  of  the  femoral  vessels 
and  terminate  above  in  the  deep  subinguinal  nodes. 
In  addition  to  these  deep  femoral  lymphatics  others 
occur  in  the  thigh  in  company  with  the  obturator  and 
sciatic  vessels,  and  the  muscles  of  the  gluteal  region  are 
drained  by  stems  which  accompany  the  gluteal  vessels. 
All  these  stems  terminate  in  nodes  belonging  to  the 
hypogastric  group,  those  accompanying  the  sciatic  ves- 
sels traversing  some  small  and  inconstant  nodes  situated 
beneath  the  pyriformis  muscle,  while  some  ten  or  twelve 
similar  nodes  occur  along  the  course  of  the  gluteal  stems. 

Practical  Considerations. —  The  Nodes  of  the 
Lower  Extremity. — The  majority  of  the  lymphatics  of 
the  sole  of  the  foot  unite  with  those  of  the  inner  side 
of  the  dorsum  and  run  with  the  long  saphenous  vein  to 
enter  the  inguinal  nodes.  A  smaller  number  run  up  the 
fibular  side  of  the  leg,  but  most  of  these  cross  over  the 
leg  or  at  the  ham  to  join  the  inner  lymphatic  vessels. 
A  still  smaller  number  run  with  the  short  saphenous 
vein  and  empty  into  the  popliteal  nodes.  The  far  more 
frequent  occurrence  of  glandular  swellings  and  abscess  in 
the  groin  than  in  the  ham  is  thus  easily  understood. 
The  popliteal  nodes  {intercondylar,  lying  on  either 
side  of  the  popliteal  artery  between  the  two  heads  of 
the  gastrocnemius,  and  supracondylar,  lying  deeper  and 
against  the  back  of  the  femur)  are  extremely  difficult  to  feel  unless  they  are 
enlarged,  and  even  then  the  only  one  which  can  be  detected  is  that  which  lies  over 
the  internal  popliteal  nerve.  This  node,  probably  from  the  constant  movement  of 
the  knee-joint,  is  very  apt  to  suppurate  as  a  result  of  superficial  sores  about  the  heel. 
The  intercondylar  nodes  cannot  be  felt ;  in  the  first  place,  because  of  their  deep 
position,  and  secondly,  because  when  pressed  they  become  still  further  forced  down 
between  the  condyles.  The  supracondylar  nodes  lie  altogether  too  deep  to  be  felt 
by  the  fingers  (Leaf).  A  small  node  beneath  the  fascia  close  to  the  point  of  entry 
of  the  short  saphenous  receives  some  of  the  lymphatics  that  accompany  that  vein. 


Superficial  lymphatic  vessel; 
of  lower  limb  ;  semidiagrammatic 
figures  of  Sappey.) 


THE    LYMPHATICS    OF   THE    LOWER    EXTREMITY.  995 

Popliteal  abscess  will  follow  pyogenic  infection  of  the  popliteal  nodes.  The 
pressure  effects  due  to  the  density  and  rigidity  of  the  popliteal  fascia  and  the  conse- 
quent necessity  for  early  and  free  incision  and  drainage  have  already  been  described 
(pages  646).  Enlargement  of  the  popliteal  nodes  has  been  mistaken  for  enlarged 
bursa; — though  the  nodes  are  deeper  and  nearer  the  median  line — for  popliteal  aneur- 
ism, and  for  neoplasms. 

The  inguinal  nodes  are  numerous  and,  on  account  of  their  frequent  involvement 
in  diseases  of  the  lower  extremity  and  of  the  genitals,  are  important.  The  arrange- 
ment into  a  superficial  and  deep  set,  and  the  division  of  the  former  into  two  groups, 
the  horizontal,  parallel  with  and  close  to  Poupart'  s  ligament,  and  the  vertical,  parallel 
with  and  close  to  the  long  saphenous  vein,  is  of  convenience.  The  deep  set  is  found 
to  the  inner  side  of  the  femoral  vein  and  may  be  said  to  include  one  group  which  is 
embedded  in  the  fatty  layer  at  the  saphenous  opening  and  bears  the  same  relation  to 
the  fascia  lata  that  the  central  group  of  axillary  glands  bears  to  the  axillary  fascia 
(Leaf)  (page  581).  The  inguinal  nodes  receive  lymph  through  the  superficial  lym- 
phatics as  follows  :  Lower  limb — vertical  set  of  superficial  nodes  ;  lower  half  of 
abdomen— middle  nodes  of  horizontal  set  ;  outer  surface  of  buttock — external  nodes 
of  horizontal  set  ;  inner  surface  of  buttock — internal  nodes  of  horizontal  set,  (a  few 
of  these  vessels  go  to  the  vertical  nodes  ;  external  genitals — horizontal  nodes,  a  few 
going  to  the  vertical  set ;  perineum-vertical  set.  The  deep  lymphatics  of  the  lower 
limb  enter  the  deep  set  of  nodes  (Treves).  The  deep  lymphatics  of  the  penis  and 
those  that  are  found  with  the  obturator,  gluteal,  and  sciatic  vessels  enter  the  pelvic 
nodes.  The  inguinal  nodes  communicate  with  the  external  and  common  iliac  nodes, 
the  pelvic  lymphatics  with  the  internal  iliac  nodes,  and  both  the  iliac  groups  with  the 
lumbar  nodes.  The  deep  node  lying  in  the  crural  canal  and  upon  the  septum  crurale 
is  variously  described  as  one  of  the  obturator  (pelvic)  group  (Leaf)  and  as  one  of 
the  deep  set  of  inguinal  nodes  (Treves).  It  should  be  remembered  that  when  it  is 
inflamed  it  may  not  only  simulate  strangulated  hernia,  but,  on  account  of  the  density 
of  the  structures  by  which  it  is  surrounded  and  their  participation  in  the  movements 
of  the  thigh,  may  give  rise  to  pain  suggesting  coxalgia. 

The  relations  of  branches  of  the  anterior  crural  nerve  to  the  inguinal  nodes 
may,  in  cases  of  inflammation  or  enlargement,  give  rise  to  pain  or  spasm  in  the  region 
supplied  by  that  nerve.  Filariasis  (elephantiasis  arabum)  of  the  femoral  lymphatics, 
which  are  obstructed  by  the  worms,  gives  rise  to  very  great  swelling  of  the  lower 
extremity  (Cochin  leg,  Barbadoes  leg). 

In  addition  to  what  has  been  stated  above  the  practical  application  of  a  knowl- 
edge of  the  lymphatics  of  the  lower  extremity  embraces  the  following  considerations  : 

(a)  The  lymphatic  vessels  may  be  inflamed  without  involvement  of  the  veins, 
when  the  course  of  some  of  the  main  vessels  can  be  distinctly  traced  under  the  skin. 
When  chronically  inflamed,  and  obstruction  exists  at  the  nearest  lymphatic  gland,  the 
vessels  may  become  thickened,  dilated,  and  tortuous.  The  lymphatic  vessels  of  the 
sheath  of  the  penis  are,  perhaps,  more  frequently  involved  in  diseased  action  than 
those  of  any  other  portion  of  the  skin  surface.  Inflamed  lymphatic  vessels  often 
co-exist  with  a  chancre.  In  cases  of  neglected  chancre,  associated  with  an  indurated 
condition  of  the  lymphatic  nodes  of  the  groin,  they  may  even  form  bulla-like  swell- 
ings which  sometimes  rupture  and  permit  the  lymph  to  escape  externally.  Rarely 
dilatation  of  the  lymphatic  vessels  occurs  without  apparent  cause. 

(6)  The  lymphatic  vessels  may,  from  causes  imperfectly  understood,  become 
filled  with  chylous  fluid.  In  one  (Petters),  remarkable  dilatation  of  the  lymphatics 
existed  in  the  right  groin  and  in  the  abdomen,  in  a  patient  the  subject  of  valvular 
heart  disease.  The  glands  were  converted  into  cyst-like  cavities  filled  with  a  yellow 
fluid.  Rosary-like  dilatations,  similar  to  those  seen  at  the  elbow,  occur  infrequently 
below  the  groin. 

The  inguinal  lymphatic  glands  are  the  common  seat  of  diseased  action  dependent 
upon  the  transmission  of  the  virus  of  syphilis,  or  of  any  other  irritant  whose  point  of 
entrance  is  through  the  external  genitals.  In  the  nonsyphilitic  infections  they 
frequently  suppurate  or  excite  suppurative  cellulitis  in  the  parts  about  them.  Acute 
inflammatory  engorgement  of  one  of  them  has  been  known  to  induce  fatal  peritonitis 
by  direct  continuity  through  the  lymphatic  vessels  of  the  abdominal  wall  (Allen). 


INDEX 


Abdomen,  examination  of,  anatomical  rela- 
tions, 536 
fascia,  superficial  of,  515 
landmarks  and  topography  of,  531 
lymphatics  of,  972 
lymph-nodes  of,  974 
muscles  of,  515 
pract.  consid.,  526 
ventral  aponeurosis  of,  521 
Abdominal  cavity,  161 5 
aorta,  794 
regions,  1 6 1 5 
hernia,  1759 

incisions,  anatomy  of,  535 
ring,  external,  524 

internal,  524 
walls,  lymphatics  of,  976 

posterior  surface  of,  525 
Acervulus,  1125 
Acetabulum,  336 
Acoustic  area,  1097 
striae,  1258 
Acromio-clavicular  articulation,  262 

pract.  consid.,  264 
Acromion  process,  250 
Adamantoblasts,  1561 
Adipose  tissue,  79 

chemical  composition  of,  83 
After-birth,  55 
Agger  nasi,  193 

Agminated  glands  (Peyer's  patches),  1641 
Air-cells,  ethmoidal,  1424 

pract.  consid.,  1429 
Air-sacs  of  lung,  1850 
Air-spaces,  accessory,  142 1 

pract.  consid.,  1426 
Ala  cinerea,  1097 
Albinism,  1461 
Alcock's  canal,  817 
Alimentary  canal,  1538 

tract,  development  of,  1694 
Alisphenoids,  186 
Allantois,  32 

arteries  of,  33 
human,  35 
stalk  of,  33 
veins  of,  33 
Alveoli  of  lung,  1850 
Ameloblasts,  1561 
Amitosis,  14 
Amnion,  30 
false,  31 
folds  of,  30 
human,  35 

cavity  of,  35 
fluid  of,  41 
liquor  of,  31 
suture  of,  31 
Amniota,  30 
Amphiarthrosis,  107 
Anal  canal,  1673 
Analogue,  4 
Anamnia,  30 
Anaphases  of  mitosis,  13 
Anastomoses,  of  ophthalmic  veins,  880 


Angulus  Ludovici,  168 
Ankle,  landmarks  of,  672 

muscles  and  fasciae  of,  pract.  consid.,  666 
Ankle-joint,  438 

movements  of,  440 
pract.  consid.,  450 
Annuli  fibrosi,  of  heart,  698 
Annulus  ovalis,  695 
tympanicus,  1493 
of  Vieussens,  695 
Anorchism,  1950 
Anthropology  of  skull,  228 
Anthropotomy,  1 
Antihelix,  1484 
Antitragus,  1484 
Antrum,  227 

of  Highmore,  1422 

pract.  consid.,  1428 
pj'lori,  1 618 
of  superior  maxilla,  201 
Anus,  1673 

formation  of,  1695 
muscles  and  fasciae  of,  1675 
pract.  consid.,  1689 
Aorta,  abdominal,  794 

branches  of,  pract.  consid.,  806 
plan  of  branches,  796 
pract.  consid.,  796 
dorsal,  721 
pulmonary,  722 
segmental  arteries  of,  847 
systemic,  723 
thoracic,  791 

prac.  consid.,  726 
valves  of,  700 
ventral,  721 
Aortic  arch,  723 

pract.  consid.,  726 
variations  of,  724 
bodies,  181 2 
bows,  847 
septum,  707 
Aponeurosis,  468 

abdominal,  ventral,  521 
epicranial,  482 
(fascia)  plantar,  659 
palmar,  606 
Appendages,vesicular,of  broad  ligament, 2002 
Appendices  epiploicae.  1660 
Appendix  epididymidis,  1949 
testis,  1949 
vermiform,  1664 

blood-vessels  of,  1667 
development  and  growth  of,  1668 
mesentery  of,  1665 
orifice  of,  1662 
peritoneal  relations  of,  1665 
pract.  consid.,  1681 
Aquaeductus  cochlea?,  1514 

vestibuli,  1512 
Aqueduct  of  Fallopius,  1496 

Sylvian,  1108 
Aqueous  humor,  1476 

chamber,  anterior  of,  1476 
997 


THIS  VOLUME  CONTAINS  PAGES  1  TO  995. 


INDEX. 


Aqueous  humor,  chamber,  posterior  of,  147 

pract.  consid.,  1476 
Arachnoid,  of  brain,  1203 

of  spinal  cord,  1022 
Arantius,  nodules  of,  700 
Archenteron,  2  5 
Arches,  visceral,  59 

fifth  or  third  branchial,  61 
first  or  mandibular,  60 
fourth  or  second  branchial,  61 
second  or  hyoid,  60 
third  or  first  branchial,  61 
Arcuate  nerve-fibres,  107 1 
Area  acustica,  1097 
embryonic,  23 
parolfactory,  1153 
pellucida,  25 
Areola,  2028 

Arm,  lymphatics,  deep,  of,  965 
superficial,  of,  963 
muscles  and  fascia  of,  pract.  consid.,  589 
Arnold's  ganglion,  1246 
Arrectores  pilorum,  1394 
Arterial  system,  general  plan  of,  720 
Artery  or  arteries,  719 

aberrant,  of  brachial,  775 
allantoic,  33 
alveolar,  741 

of  internal  maxillary,  741 
anastomoses  around  the  elbow,  778 
anastomotica  magna,  of  brachial,  778 

of  femoral,  831 
angular,  738 

of  facial,   738 
aorta,  systemic,  723 
articular,  of  popliteal,  833 
auditory,  internal,  759 
auricular,  anterior,  of  temporal,  745 
deep,  740 

of  internal  maxillary,  740 
of  occipital,  744 
posterior,  744 
axillary,  767 

pract.  consid.,  769 
azygos,  of  vaginal,  Si  2 
basilar,  758 
brachial,  773 

pract.  consid.,  776 
brachialis  superficialis,  775 
bronchial,  792 
buccal,  741 

of  internal  maxillary,  741 
to  bulb  (bulbi  urethrae),  817 
calcaneal,  external,  838 
internal,  839 
of  external  plantar,  840 
calcarine,  760 
carotid,  common,  730 

pract.  consid.,  731 
external,  733 

pract.  consid.,  733 
internal,  746 

pract.  consid.,  747 
system,  anastomoses  of.  753 
carpal,  of  anterior  radial,  788 
of  anterior  ulnar,  782 
arch,  posterior,  789 
of  posterior  radial,  788 
of  posterior  ulnar,  782 
reta,  anterior,  791 
centralis  retinas,  749 
cerebellar,  inferior,  anterior,  759 
posterior,  759 


Artery  or  arteries,  cerebellar,  superior,  759 
cerebral,  anterior,  753 

middle,  752 

posterior,  760 
cervical,  ascending,  of  inferior  thyroid, 
766 
of  transverse  cervical,  767 

deep,  764 

superficial,  766 

transverse,  767 
choroid,  anterior,  752 
ciliary,  749 

anterior,  749 

posterior,  749 
circle  of  Willis,  760 
circumflex,  anterior,  773 

external,  of  deep  femoral,  828 

internal,  of  deep  femoral,  828 

posterior,  773 
circum patellar  anastomosis,  834 
coccygeal,  of  sciatic,  815 
coeliac  axis,  797 
colic,  left,  803 

right,  802 
comes  nervi  ischiadici,  815 
communicating,  anterior,  753 

of  peroneal,  838 

posterior,  751 

of  posterior  tibial,  839 
coronary,  inferior,  738 
of  facial,  738 

left,  728 

right,  728 

superior,  73S 

of  facial,  73 S 
of  corpus  cavernosum,  Si 7 
cremasteric,  of  deep  epigastric,  820 

of  spermatic,  805 
crico-thyroid,  734 

of  superior  thyroid,  734 
cystic,  of  hepatic,  799 
dental,  anterior,  of  internal  maxillary, 
74i 

inferior,  740 
development  of,  846 

of  lower  limb,  848 

of  upper  limb,  S48 
digital,  collateral,  of  ulnar,  784 

of  ulnar,  784 
dorsal,  of  foot,  845 

of  penis  (clitoris),  Si 7 
dorsalis  hallucis,  846 

indicis,  789 

pedis,  845 

pollicis,  789 
epigastric,  deep,  820 

superficial,  82 6 

superior,  763 
ethmoidal,  749 

anterior,  750 

posterior,  749 
facial,  737 

anastomoses  of,  738 

glandular  branches  of,  737 

pract.  consid.,  738 

transverse,  745 
femoral,  821 

anastomoses  of,  831 

deep.  828 

development  of,  823 

pract.  consid.,  824 
fibular,  superior,  of  anterior  tibial,  844 
frontal,  of  ascending  middle  cerebral,  753 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


999 


Artery  or  arteries,  frontal,  of  inferior  middle 
cerebral,  753 
internal,  anterior,  753 
middle,  753 
posterior,  753 
of  ophthalmic,  750 
Gasserian,  of  middle  meningeal,  .740 
gastric,  798 

short,  of  splenic,  800 
gastro-duodenal,  799 
gastro-epiploic,  left,  801 

right,  799 
glandular,  of  facial,  737 
gluteal,  811 

pract.  consid.,  814 
hemorrhoidal,  inferior,  817 
middle,  813 
superior,  803 
hepatic,  799 
hyaloidea,  1474 
hypogastric  axis,  808 
obliterated,  808 
ileo-colic,  802 
iliac,  circumflex,  deep,  821 
superficial,  826 
common,  807 

pract.  consid.,  807 
external,  S18 

anastomoses  of,  821 
pract.  consid.,  819 
of  ilio-lumbar,  810 
internal,  S08 

anastomoses  of,  818 
pract.  consid.,  810 
ilio-lumbar,  810 

infrahyoid,  of  superior  thyroid,  734 
infraorbital,  741 

of  internal  maxillary,  741 
innominate,  729 

pract.  consid.,  729 
intercostal,   of  anterior   internal   mam- 
mary, 763 
•   aortic,  792 
of  internal  mammary,  765 
superior,  764 
internal  mammary,  pract.  consid.,   764 
interosseous,  anterior,  781 
common,  781 
dorsal,  846 
posterior,  782 
intestinal,  of  superior  mesenteric,  802 
labial,  inferior,  738 

of  facial,  738 
of  internal  maxillary,  741 
lachrymal,  749 
laryngeal,  inferior,  766 

superior,  of  superior  thyroid,  734 
lateral  cutaneous,  of  aortic  intercostals, 

793 
lenticulo-striate,  of  middle  cerebral,  752 
lingual,  735 

anastomoses  of,  736 

dorsal,  736 

pract.  consid.,  736 
lumbar,  805 

of  ilio-lumbar,  810 
malleolar,  external,  844 

internal,  of  anterior  tibial,  844 
of  posterior  tibial,  839 
mammary,  of  aortic  intercostals,  793 

internal,  763 

lateral  internal,  764 
masseteric,  740 


Artery  or  arteries,  masseteric,  of  facial,  738 

of  internal  maxillary,  740 
mastoid,  of  occipital,  744 
maxillary,  internal,  739 

anastomoses  of,  742 
development  of,  742 
median,  781 
mediastinal,  of  internal  mammary,  763 

of  thoracic  aorta,  792 
meningeal,  anterior,  748 

of  ascending  pharyngeal,  743 

middle,  740 

of  internal  maxillary,  740 

posterior,  of  occipital,  744 
of  vertebral,  758 

small,  740 
mesenteric,  inferior,  802 

superior,  801 
metacarpal,  dorsal,  789 
metatarsal,  of  foot,  845 
middle,  colic,  802 
musculo-phrenic,  763 
nasal,  lateral,  738 

of  facial,  738 

of  ophthalmic,  750 
naso-palatine,  of  internal  maxillary,  742 
nutrient,  of  brachial,-  774 

of  peroneal,  838 

of  posterior  tibial,  838 

of  ulnar,   781 
obturator,  813 

from  deep  epigastric,  814 
occipital,  743 

pract.  consid.,  744 
oesophageal,  of  gastric,  798 

of  thoracic  aorta,  792 
omphalomesenteric,  32 
ophthalmic,  748 

anastomoses  of,  750 
orbital,  of  middle  meningeal,  740 

of  temporal,  745 
ovarian,  805 

of  uterine,  813 
palatine,  ascending,  737 
of  facial,  737 

descending,  741 

of  internal  maxillary,  741 
palmar  arch,  deep,  785 
superficial,  7S4 

deep,  7S2 

interosseous,  790 
palpebral,  of  internal  maxillary,  741 

of  ophthalmic,  750 
pancreatic,-  of  splenic,  800 
pancreatico-duodenal,  inferior,  802 

superior,  799 
parietal,  of  middle  cerebral,  753 
parieto-occipital,  760 

temporal,  753 
parotid,  of  temporal,  745 
perforating,   of  anterior  internal  mam- 
mary, 763 

of  deep  femoral,  828 

posterior,  of  external  plantar,  840 

of  radial,  791 
perineal,  superficial,  817 

transverse,  817 
peroneal,  anterior,  838 

posterior,  838 

of  posterior  tibial,  838 
petrosal,  of  middle  meningeal,  740 
pharyngeal,  ascending,  743 

of  ascending  pharyngeal,  743 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


INDEX. 


Artery  or  arteries,  phrenic,  inferior,  804 

superior,  763 
plantar  arch,  840 

digital,  840 

external,  S40 

internal,  839 

interosseous,  840 
popliteal,  831 

pract.  consid.,  832 
posterior  choroidal,  760 
princeps  cervicis,  744 

hallucis,  841 

pollicis,  789 
profunda,  inferior,  777 

superior,  777 
prostatic,  812 
pterygoid,  740 

of  internal  maxillary,  740 
pterygo-palatine,  742 

of  internal  maxillary,  742 
pubic,  of  deep  epigastric,  820 

of  obturator,  813 
pudic,  external,  deep,  82S 
superficial,  826 

internal,  815 

accessory,  818 
pulmonary,  722 

valves  of,  700 
pyloric,  of  hepatic,  799 
radial,  785 

development  of,  786 

pract.  consid.,  786 

.recurrent,  7S7 
radialis  indicis,  790 

superficialis,  773 
ranine,  736 
recurrent,  of  palm,  791 

of  posterior  interosseous,  7S2 
renal,  804 
sacral,  lateral,  810 

middle,  806 
scapular,  dorsal,  773 

posterior,  767 
sciatic,  815 
septal,  of  nose,  738 
sigmoid,  803 
spermatic,  805 
spheno-palatine,  742 

of  internal  maxillary,  742 
spinal,  anterior,  of  vertebral,  759 

posterior,  of  vertebral,  758 
splenic,  800 

sterno-mastoid,  of  external  carotid,  743 
of  occipital,  744 
of  superior  thyroid,  734 
striate,  external,  of  middle  cerebral,  752 

internal,  of  middle  cerebral,  752 
structure  of,  675 
stylo-mastoid,  745 
subclavian,  753 

pract.  consid.,  756 
subcostal,  792 
sublingual,  736 
submental,  737 

of  facial,  737 
subscapular,  772 
suprahyoid,  736 
supraorbital,  749 
suprarenal,  804 

inferior,  804 
suprascapular,  767 
tarsal,  external,  845 

internal,  845 


Artery    or   arteries,    temporal,    anterior,    of 
vertebral,  760 
deep,  740 

of  internal  maxillary,  740 
middle,  745 
posterior,  of  vertebral,  760 
superficial,  745 

pract.  consid.,  745 
thoracic,  acromial,  771 
alar,  772 
long,  772 
superior,  771 
thyroid  axis,  765 

pract.  consid.,  766 
inferior,  766 
superior,  734 

pract.  consid.,  735 
tibial,  anterior,  842 

anastomoses  of,  844 
pract.  consid.,  842 
posterior,  834 

anastomoses  of,  841 
development  of,  836 
pract.  consid.,  836 
recurrent,  anterior,  844 
posterior,  844 
tonsillar,  737 

of  facial,  737 
tubal,  of  ovarian,  805 

of  uterine,  813 
tympanic,  of  internal  carotid,  748 
of  internal  maxillary,  740 
of  middle  meningeal,  740 
ulnar,  778 

accessory,  776 
development  of,  779 
pract.  consid.,  780 
recurrent,  anterior,  781 
posterior,  781 
umbilical,  54 
ureteral,  of  ovarian,  805 
of  renal,  804 
of  spermatic,  805 
of  uterine,  813 
urethral,  817 
uterine,  812 
vaginal,  812 
vertebral,  758 

pract.  consid.,  761 
vesical,  inferior,  811 
middle,  Sir 
of  obturator,  S13 
superior,  811 
vesiculo-deferential,  812 
Vidian,  742 
vitelline   32 
volar,  superficial,  788 
Arthrodia,  113 

Articulation  or  articulations,  acromio-clavic- 
ular,  pract.  consid.,  264 
carpo-metacarpal,  325 

movements  of,  326 
costo-vertebral,  160 
of  ethmoid,  194 
of  foot,  440 
of  frontal  bone,  197 
of  inferior  turbinate  bone,  208 
of  lachrymal  bone,  207 
of  malar  bone,  210 
metacarpophalangeal,  327 

movements  of,  328 
of  nasal  bone,  209 
of  occipital  bone,  atlas,  and  axis,  13  5 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


Articulation  or  articulations,  of  palate  bone, 
205 

of  parietal  bone,  199 

sacro-iliac,  338 

scapuloclavicular,  262 

of  sphenoid  bone,  190 

sterno-clavicular,  261 
pract.  consid.,  263 

of  superior  maxilla,  202 

of  temporal  bone,  184 

temporo-mandibular,  214 
development  of,  215 
movements  of,  2r5 

thoracic  anterior,  158 

of  thorax,  157 

of  thumb,  326 

tibio-fibular,  inferior,  396 
superior,  396 

of  vertebral  column,  132 

of  vomer,  206 
Arytenoid  cartilages,  181 6 
Asterion,  22S 
Astragalus,  423 

development  of,  425 
Astrocytes,  1003 
Atlas,  120 

development  of,  r3i 

variations  of,  120 
Atria  of  lung,  1850 
Auditory  canal,  external,  1487 

blood-vessels  of,  1489 
nerves  of,  1490 
pract.  consid. ,  149 1 
internal,  1514 

ossicles,  1496 

path,  1258 
Auerbach,  plexus  of,  1643 
Auricle  or  auricles,  r484 

antihelix  of,  1484 

antitragus  of,  1484 

blood-vessels  of,  i486 

cartilage  of,  1485 

concha  of,  1484 

of  heart,  693 

helix  of,  1484 

ligaments  of,  i486 

lobule  of,  1484 

muscles  of,  i486 

nerves  of,  1487 

pract.  consid.,  1490 

structure  of,  1485 

tragus  of,  1484 
Auricular  canal,  705 

Auriculo-ventricular  bundle  of  heart,  701 
Axilla,  574 

muscles  and  fascia  of,  pract.  consid.,  579 
Axis,  121 

Axis-cylinder,  1001 
Axones,  of  neurones,  997 
Azygos  system  of  veins,  893 

Bartholin,  glands  of,  2026 

Basion,  228 

Bell,  externaV  respiratory  nerve  of,  1295 

Bertin,  bones  of,  191 

columns  of,  1876 
Bicuspid  teeth,  1545 
Bile-capillaries,  171 5 
Bile-duct,  common,  1720 
opening  of,  1720 
pract.  consid.,  1731 

interlobular,  1 7 1 7 

tymphatics  of,  9S1 


Biliary  apparatus,  1718 
Bladder,  lymphatics  of,  985 
urinary,  1901 

capacity  of,  1903 
development  of,  1938 
in  female,  1908 
fixation  of,  1905 
infantile,  190S 
interior  of,  1904 
nerves  of,  1910 
peritoneal  relations  of,  1904 
pract.  consid.,  1910 
relations  of,  1906 
structure  of,  1908 
trigone  of,  1904 
vessels  of,  19 10 
Blastoderm,  22 
bilaminar,  23 
trilaminar,  23 
Blastodermic  layers,  22 

derivatives  of,  24 
vesicle,  stage  of,  56 
Blastomeres,  21 
Blastopore,  25 
Blastula,  25 
Blood,  680 

Blood-cells,  colored,  681 
colorless,  684 
development  of,  687 
Blood-crystals,  681 

lakes  of  dural  sinuses,  852 
plaques,  685 
Blood-vascular  system,  673 
Blood-vessels  of  auricle,  i486 
of  bone,  93 
of  brain,  1206 
capillary,  67S 
of  cartilage,  81 
development  of,  686 
of  duodenum,  1649 
of  Eustachian  tube,  1504 
of  external  auditory  canal,  1489 
of  eyelids,  1445 
of  glands,  1535 
of  hair-follicles,  1394 
of  kidney,  1884 
of  liver,  1709 
lobular,  of  liver,  17 13 
of  lung,  1853 

of  membranous  labyrinth,  1522 
of  nasal  fossa,  1425 
of  non-striated  muscle,  456 
of  nose,  1407 
of  pericardium,  716 
of  pleura,  i860 
of  rectum,  1679 
of  retina,  1467 
of  skin,   1387 
of  small  intestine,  1642 
of  spinal  cord,  1047 
of  stomach,  1627 
of  striated  muscle,  464 
structure  of,  673 
of  sweat  glands,  1400 
vasa  vasorum,  674 
Body-cavity,  differentiation  of,  1700 
Body-form,  general  development  of,  56 
Body-stalk,  37 
Bone  or  bones,  84 
age  of,  106 
astragalus,  423 
of  Bertin,  iqi 
blood-vessels  of,  93 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


1002 


INDEX. 


Bone  or  bones,  calcaneum,  419 
canaliculi  of,  86 
cancellated,  85 
carpus,  309 
cells  of,  89 

chemical  composition  of,  84 
clavicle,  257 
compact,  86 

development  of,  100 
cranium,  172 
cuboid,  422 
cuneiform,  310 
external,  428 
internal,  426 
middle,  427 
development  of,  94 

endochondral,  94 
intramembranous,  98 
diaphysis  of,  104 
elasticity  of,  105 
ethmoid,  191 
femur,  352 
fibula,  390 
frontal,  194 

general  considerations  of,  104 
growth  of,  1 01 
Haversian  canals  of,  88 

system  of,  86 
humerus,  265 
hyoid,  216 
ilium,  332 

inferior  turbinate,  208 
innominate,  332 
intramembranous,  101 
ischium,  336 
lachrymal,  207 
lacunae  of,  86 

lamellae  of,  circumferential,  86 
Haversian,  86 
interstitial,  86 
lymphatics  of,  93 
malar,  209 
maxilla,  inferior,  211 

superior,  199 
mechanics  of,  105 
metacarpal,  314 
metatarsal,  428 
nasal,  209 
nerves  of,  94 
number  of,  107 
occipital,  172 
os  magnum,  312 
palate,  204 
parietal,  197 
parts  of,  106 
patella,  398 
periosteum  of,  89 
phalanges  of  foot,  432 

of  hand,  317 
physical  properties  of,  85 
pisiform,  311 
pubes,  334 
radius,  287 

relation  of  to  figure,  107 
ribs,  149 
scaphoid,  309 

of  foot,  425 
scapula,  248 
semilunar,  310 
sesamoid,  104 
sex  of,  106 
shapes  of,  104 
Sharpey's  fibres  of,  87 


Bone  or  bones,  of  shoulder-girdle,  248 
skull,  172 
sphenoid,  186 
sphenoidal,  turbinate,  191 
sternum,  155 
structure  of,  85 
subperiosteal,  98 
tarsal,  419 
temporal,  176 
of  thorax,  149 
tibia,  382 
trapezium,  311 
trapezoid,  311 
ulna,  281 
unciform,  312 
variations  of,  107 
Volkmann's  canals  of,  89 
vomer,  205 
Bone-marrow,  90 
cells  of,  92 
giant  cells  of,  92 
nucleated  red  cells  of,  92 
erythroblasts,  92 
normoblasts,  92 
primary,  95 
red,  90 
yellow,  93 
Boviman,  glands  of,  141 5 

membrane  of,  145 1 
Brachium,  inferior,  1107 

internal  structure  of,  n  10 
superior,  1 1  o  7 
Brain,  1055 

blood-vessels  of,  1206 
general  development  of,  1058 
lymphatics  of,  948 
measurements  of,  119  5 
membranes  of,  1197 
pract.  consid.,  1207 
weight  of,  1 196 
Brain-sand  (acervulus),  n 25 
Brain-stem,  1056 
Brain- vesicles,  primary,  1059 

secondary,  1061 
Branchial  arches,  derivatives  of,  847 
Bregma,  228 
Bronchial  tree,  1847 

variations  of,  1849 
Bronchus  or  bronchi,  1838 
homologies  of,  1848 
pract.  consid.,  1840 
Bruch,  membrane  of,  1456 
Brunner,  glands  of,  1639 
Buccal  fat-pad,  489 
Bulb,  1063 

of  internal  jugular  vein,  861 
olfactory,  n  51 
urethral,  1968 
Bulbo-tecto-thalamic  strands,  n  16 
Bulbus  vestibuli,  2025 
Bulla,  of  ethmoid,  194 
Burns,  space  of,  543 
Bursa  or  bursa;,  1 1 1 
acromial,  586 
around  ankle,  648 
bicipito-radial,  586 
iliopectineal,  623 
of  biceps  femoris,  636 
of  gluteal  region,  630 
of  knee-joint,  406 
of  m.  obturat.  int.,  630 
of  m.  pyriformis,  561 
olecranal,  586 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


1003 


Bursa  or  bursa?,  subdeltoid,  578 

subscapular,  578 
Buttocks,  landmarks  of,  669 

muscles  and  fascia?  of,  pract.  consid.,  641 

Caecum,  1660 

blood-vessels  of,  1667 

interior  of,  1661 

peritoneal  relations  of,  1665 

position  of,  1662 

pract.  consid.,  1680 

structure  of,  1663 
Calamus  scriptorius,  1096 
Calcaneum,  419 
Camper's  fascia,  515 
Canal  or  canals,  Alcock's,  817 

alimentary,  1538 

anal,  1673 

auditory,  external,  1487 

auricular  of  heart,  705 

carotid,  184 

central,  of  spinal  cord,  1030 

of  Cloquet  (Stilling),  1474 

crural,  625 

ethmoidal  (foramina),  192 

facial,  184 

femoral,  625 

Haversian,  of  bone,  88 

Hunter's,  628 

hyaloid,  1474 

incisive,  14 13 

inguinal,  523 

naso-lachrymal,  1479 

neural,  26 

neurenteric,  25 

of  Nuck,  2006 

palatine,  anterior,  201 
posterior,  204 

of  Petit,  1476 

pterygo-palatine,  205 

reuniens,  1 5 1 5 

of  Scarpa,  201 

of  Schlemm,  1452 

semicircular  membranous,  1515 
osseous,  1 5 1 2 
structure  of,  1516 

of  Stenson,  201 

of  Stilling,  1474 

Vidian,  189 

Volkmann's,  of  bone,  89 
Canaliculi,  of  bone,  86 

lachrymal,  1478 
Canine  teeth,  1544 
Canthi  of  eye,  1442 
Capitellum  of  humerus,  268 
Capsule,  external,  11 72 

of  Glisson,  1708 

internal,  n  73 

Suprarenal  (body),  1801 

of  Tenon,  504 
Caput  medusae,  534 
Cardiac  muscle,  462 
Cardinal  system  of  veins,  854 
Carina  trachea?,  1837 

urethralis,  2016 
Carotid  body  (gland),  1809 

chromaffine  cells  of,  18 10 
sheath,  543 
Carpo-metacarpal  articulations,  325 
Carpus,  309 

pract.  consid.,  319 
Cartilage  or  cartilages,  80 


Cartilage  or  cartilages,  articular,  81 

arytenoid,  1816 

of  auricle,  1485 

blood-vessels  of,  81 

capsule  of,  80 

chemical  composition  of,  83 

costal,  153 

cricoid,  181 3 

cuneiform  of  Wrisberg,  1S17 

development  of,  82 

elastic,  81 

fibrous,  82 

hyaline,  80 

lacuna?  of,  80 

lateral,  of  nose,  1405 

matrix  of,  80 

of  nasal  septum,  1405 

of  nose,  1404 

perichondrium  of,  81 

of  Santorini,  181 7 

thyroid,  1814 

triangular,  of  nasal  septum,  224 

vomerine,  1406 
Cartilage-cells,  80 
Caruncula?  hymenales,  2016 

salivares,  1581 
Caruncle,  lachrymal,  1443 
Cauda  equina  of  spinal  cord,  1025 
Cavity,  abdominal,  161 5 

nasal,  223 

pneumatic  accessory,  226 

segmentation,  22 

synovial,  of  foot,  447 

tympanic,  1492 

of  tympanum,  183 
Cell  or  cells,  animal,  6 

of  bone,  89 

of  connective  tissues,  73 

decidual,  47 

gustatory,  1435 

mastoid,  1504 

of  Rauber,  23 

spermatogenetic,  1943 

tactile,  of  Merkel,  1016 
Cell-division,  10 

direct,  14 

indirect,  n 

reduction  division,  18 
Cell-mass,  inner,  23 

intermediate,  29 
Cementoblasts,  1563 
Cementum,  1552 

formation  of,  1563 
Centrosome,  9 
Cephalic  flexure,  1061 
Cerebellar  peduncle,  fibre-tracts  of,  1093 
inferior,  1067 

inferior,  fibre-tracts  of,  1093 
middle,  fibre-tracts  of,  1094 
superior,  fibre-tracts  of,  1094 
Cerebellum,  1082 

architecture  of,  10SS 

cortex  of,  1090 

histogenesis  of,  1 1  o  5 

development  of,  1103 

flocculus  of,  1085 

hemispheres  of,  1082 

lobus  cacuminis  of,  10S5 
centralis  of,  10S4 
clivi  of,  1085 
culminis  of,  10S4 
lingula?  of,  1084 
noduli  of,  1085 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


ioo4 


INDEX. 


Cerebellum,  lobus  pyramidis  of,  1086 
tuberis  of,  1087 
uvulae  of,  1086 

medullary  substance  of,  1093 

nuclei,  internal  of,  1088 

nucleus,  dentate  of,  1088 

emboliformis  (embolus)  of,  1089 
fastigii  of,  1089 
globosus  of,  1089 

Purkinje  cells  of,  1090 

tonsil  (amygdala)  of,  1086 

worm  of,  1082 
Cerebral  commissures,  development  of,  1194 

convolutions  (gyri),  113  5 

fissures  (sulci),  1135 

hemispheres,  1133 

architecture  of,  1155 
longitudinal  fissure  of,  1133 

lobes,  1 13  5 
.   localization,  12 10 

peduncles,  1107 
Cerebro-spinal  fluid,  1023 
Cerumen,  1489 
Cervical  flexure,  1062 
Cheeks,  1538 

lymphatics  of,  951 

pract.  consid.,  1594 
Choanal,  1413 

(bony),  224 

primitive,  1429 
Chorda  dorsalis,  27 
Chordae  tendineas,  of  heart,  697 
Choriocapillaris,  1456 
Chorion,  32 

allantoic,  33 

epithelium  of,  49 

frondosum,  38 

human,  41 

laeve,  38 

primitive,  31 

syncytium  of,  49 

villi  of,  49 
Choroid,  1455 

development  of,  1482 

plexus  of  fourth  ventricle,  1100 
of  third  ventricle,  1131 

pract.  consid.,  1459 

structure  of,  1456 
Chromaffine  cells  of  carotid  body,  i8ro 
Chromatin,  9 
Cilia,  70 
Ciliary  body,  1457 

ganglion,  1236 

muscle,  1458 

processes,  1457 

ring,  1457 
Circulation,  foetal,  929 

general  plan  of,  719 
Cisterna  magna,  1203 
Claustrum,  n 72 
Clava,  1066 
Clavicle,  257 

development  of,  25S 

fracture  of,  259 

landmarks  of,  260 

pract.  consid.,  258 

sexual  differences,  258 

surface  anatomy  of,  258 
Clinoid  process,  anterior,  189 

processes,  middle,  186 
posterior,  1S6 
Clitoris,  2024 

glans  of,  2024 


Clitoris,  nerves  of,  2025 
prepuce  of,  2024 
vessels  of,  2025 
Cloaca,  1696 
Cloquet,  canal  of,  1474 

lymph-nodes  of,  992 
Coccygeal  body,  1810 
Coccyx,  127 

development  of,  131 
Cochlea,  membranous,  151 7 
nerves  of,  1 5  2 1 
organ  of  Corti  of,  1519 
Reissner's  membrane  of,  151 7 
structure  of,  1518 
osseous,  1 513 
Coeliac  plexus,  lymphatic,  973 
Ccelom,  28 

pericardial,  1700 
pleural,  1700 
Cohnheim's  fields  of  striated  muscle-fibre,  461 
Collagen,  83 
Colles,  fascia  of,  562 
ligament  of,  523 
Colliculi  inferiores,  1107 

superiores,  1107 
Colliculus,    inferior,    internal    structure    of, 
1  no 
superior,  internal  structure  of,   n  10 
Colon,  1668 

ascending,  1668 
blood-vessels  of,  1672 
descending,  1669 
flexure,  hepatic  of,  1668 

splenic  of,  1668 
lymphatics  of,  1672 
nerves  of,  1672 
peritoneal  relations  of,  1670 
pract.  consid.,  1685 
relations  of,  1668 
transverse,  1668 
Colostrum,  2031 

corpuscles,  2031 
Columnar  carneae,  of  heart,  697 
Column,  spinal,  114 
Columns,  anterior,  of  spinal  cord,  1027 
lateral,  of  spinal  cord,  1027 
of  Morgagni,  1674 
posterior,  of  spinal  cord,  1027 
Commissura  habenulae,  n 24 
hippocampi,  n 58 
hypothalamica,  ri28 
Commissure,  anterior,  n 85 
of  Meynert,  1115 
middle,  n  19 
posterior,  112  5 
Concha,  1484 
Condylarthrosis,  113 
Conjunctiva,  1441 
bulbar,  1445 
palpebral,  1445 
pract.  consid.,  1447 
Connective    substances,    chemical    composi- 
tion of,  83 
tissues,  73 

cells  of,  73 
fixed,  74 
typical,  74 
wandering,  74 
chemical  composition  of,  S3 
granule-cells  of,  74 
ground-substance  of,  75 
intercellular    constituents  of,  74 
pigment-cells  of,  74 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


INDEX. 


1005 


Construction,  general  plan  of,  1 
Conus  medullaris,  of  spinal  cord,  1021 
Convolutions  (gyri)  cerebral,  1135 
Cooper,  ligaments  of,  2029 
Cord,  spermatic,  1960 
Corium,  1383 
Cornea,  1450 

pract.  consid,,  1453 
structure  of,  1451 
Corniculee  laryngis,  181 7 
Cornua  sphenoidalia,  191 
Corona  radiata,  1186 
Coronoid  process,  of  ulna,  281 
Corpora  cavernosa  of  penis,  1966 
mammillaria  (albicantia),  n 28 
quadrigemina,  1106 
Corpus  albicans,  1991 
Arantii,  700 
callosum,  n 55 
ciliare,  1457 
dentatum,  1088 
fibrosum,  1991 
Highmori,  1942 
luteum,  1990 

spongiosum,  of  penis,  1967 
striatum,  11 69 

connections  of,  n 72 
development  of,  1193 
structure  of,  1 1 7 1 
subthalamicum,  1 1 2  8 
trapezoides,  1079 
Corpuscles,  corneal,  1452 
genital,  1017 
of  Grandry,  1016 
of  Hassall,  1799 
of  Herbst,  1019 
of  Meissner,  10 17 
of  Ruffini,  1017 
Vater-Pacinian,  1018 
Cortex  of  cerebellum,  1090 

cerebral,  histogenesis  of,  1192 
local  variations  in,  11  So 
nerve-cells  of,  11 76 
nerve-fibres  of,  1179 
structure  of,  1175 
Corti,  ganglion  of,  1257 
membrane,  1521 
organ  of,  1 5 1 9 
Costal  cartilage,  153 
Cotyledons  of  placenta,  50 
Cowper,  glands  of,  1984 
Cranial  capacity,  230 
nerves,  12 19 

abducent  (6th),  1249 
auditory  (8th),  1256 
development  of,  1376 
facial  (7th),  1250 
glosso-pharyngeal  (9th),  1260 
hypoglossal  (12th),  1275 
oculomotor  (3rd),  1225 
olfactory  (1st),  1220 
optic  (2nd),  1223 
pract.  consid.,  1220 
spinal-accessory  (nth),  1274 
trigeminal  (5th),  1230 
trochlear  (4th),  1228 
vagus  (10th),  1265 
Cranio-cerebral  topography,  12 14 
Cranium,  172 

architecture  of,  220 
exterior  of,  218 
fossa,  anterior,  220 
middle  of,  220 


Cranium,  fossa,  posterior  of,  220 
fractures  of,  238 
interior  of,  220 

muscles  and  fasciae,  pract.  consid.,  489 
pract.  consid.,  235 
vault  of,  220 
Cretinism,  1794 
Cricoid  cartilage,  1S13 
Crista  galli,  of  ethmoid,  191 
Crura  of  penis,  1967 
Crusta,  1 1 1 5 
Cuboid  bone,  422 
Cumulus  oophorus,  1989 
Cuneate  nucleus,  1069 
tubercle,  1067 
Cuneiform  bone,  310 
external,  428 
internal,  426 
middle,  427 
Cuticle,  1385 
Cuvier,  ducts  of,  854 
Cystic  duct,  1720 

pract.  consid.,  1731 
Cytoplasm,  structure  of,  7 

Dacryon,  228 

Darwin,  tubercle  of,  1484 

Decidua,  44   _ 

capsularis,  46 

cells  of,  47 

placentalis,  48 

reflexa,  45 

serotina,  48 

vera,  46 
Decussation  of  pyramids,  1064 

sensory,  1070 
Deiters,  cells  of,  1521 

nucleus,  1076 
Demours,  membrane  of,  1452 
Dendrites,  of  neurones,  997 
Dental  formula,  1542 

papilla,  1558     ■ 
Dentine,  1550 

formation  of,  1559 
Dentition,  first  and  second,  1564 
Derma,  1383 

Descemet's  membrane,  1452 
Deutoplasm,  15 
Development  of  alimentary  tract,  1694 

of  atlas,  131 

of  auditory  nerves,  1525 

of  axis,  131 

of  bone,  94 

of  carpus,  313 

of  cartilage,  82 

of  cerebellum,  n  03 

of  clavicle,  25S 

of  coccyx,  131 

of  cranial  nerves,  1376 

of  ear,  1523 

early,  15 

of  elastic  tissue,  77 

of  ethmoid  bone,  194 

of  external  ear,  1526 

of  external  genital  organs,  2043 

of  eye,  1480 

of  face,  62 

of  Fallopian  tube,  1999 

of  femur,  3  59 

of  fibrous  tissue,  76 

of  fibula,  393 

of  frontal  bone,  197 

of  ganglia,  10 12 


THIS  VOLUME   CONTAINS   PAGES  1   TO   995. 


ioo6 


INDEX. 


Development,  general,  of  brain,  1058 
of  general  body-form,  56 
of  glands,  1537 
of  hairs,  1401 
of  heart,  705 
of  humerus,  269 
of  hyoid  bone,  216 
of  inferior  turbinate  bone,  208 
of  innominate  bone,  337 
of  internal  ear,  1523 
of  kidney,  1937 
of  liver,  1723 
of  lungs,  1 86 1 
of  lymphatic  vessels,  939 
of  lymph-nodes,  940 
of  malar  bone,  210 
of  mammary  glands,  2032 
of  maxilla,  inferior,  213 
of  maxilla,  superior,  202 
of  medulla  oblongata,  1101 
of  mesencephalon,  1 1 1 7 
of  middle  ear,  1525 
of  muscle,  non-striated,  457 
of  muscle,  striated,  465 
of  nails,  1403 
of  nasal  bone,  209 
of  nerves,  1375 
of  nervous  tissues,  1009 
of  nose,  1429 
of  occipital  bone,  175 
of  oral  cavity,  62 
glands,  1589 
of  ovary,  1993 
of  palate  bone,  205 
of  pancreas,  1737 
of  parietal  bone,  199 
of  patella,  400 
of  pelvis,  344 
of  peripheral  nerves,  ion 
of  peritoneum,  1702 
of  pharynx,  1603 
of  pituitary  body,  1808 
of  pons  Varolii,  n 03 
of  prostate  gland,  1979 
of  radius,  293 

of  reproductive  organs,  2037 
of  respiratory  tract,  1861 
of  ribs,  1  S3 
of  sacrum,  129 
of  scapula,  253 
of  skin,  1400 
of  sphenoid  bone,  190 
of  spinal  cord,  1049 
of  spleen,  17S7 
of  sternum,  157 
of  suprarenal  bodies,  1S04 
of  sweat  glands,  1404 
of  sympathetic  system,  1013 
of  teeth,  1556 
of  temporal  bone,  184 
of  thymus  body,  1800 
of  thyroid  body,  1793 
of  tibia,  3S7 
of  ulna,  285 
of  urethra,  1938 
of  urinary  bladder,  1938 

organs,  1934 
of  uterus,  2010 
of  vagina,  2019 
of  veins,  926 
of  vertebras,  128 
of  vomer,  206 


Diaphragm,  556 

lymphatics  of,  970 

of  pelvis,  1676 
Diaphragma  sella;,  1200 
Diaphysis,  of  bone,  104 
Diarthrosis,  107 
Diencephalon,  11 18 
Diverticulum  of  Meckel,  44 
Dorsum  sella?,  186 
Douglas,  fold  of,  522 

pouch  of,  1743 
Duct  or  ducts,  cochlear,  151 7 

of  Bartholin,  1585 

bile,  1720 

of  Cuvier,  854 

cystic,  1720 

ejaculatory,  1955 

Gartner's,  2001 

hepatic,  17 18 

lactiferous,  2028 

lymphatic,  right,  945 

Mullerian,  2031 

nasal  (naso-lachrymal)  1479 

pancreatic,  1736 

paraurethral,  1924 

parotid,  1583 

of  Rathke,  2040 

renal,  1894 

of  Rivinus,  1585 

of  Santorini,  1736 

spermatic,  1953 

of  Stenson,  1583 

sublingual,  1585 

submaxillary,  1584 

thoracic,  941 

thyro-glossal,  1793 

vitelline,  32 

of  Wharton,  1584 

of  Wirsung,  1736 

Wolffian,  1935 
Ductus  arteriosus  (Botalli),  723 

endolymphaticus,  15 14 

venosus  (Aarantii),  929 
Duodenal  glands,  1639 
Duodeno-hepatic  ligament,  1644 
Duodenojejunal  flexure,  1645 

fossa;,  1647 
Duodenum,  1 644 

interior  of,  1648 
Dupuytren's  contraction,  616 
Dura  mater  of  brain,  1198 

of  spinal  cord,  1022 

Ear,  1483 

development  of,  1523 
external,  1484 

pract.  consid.,  1490 
internal,  1510 

membranous  labyrinth  of,  15 14 
osseous  labyrinth  of,  1511 
perilymph  of,  1514 
lymphatics  of,  950 
middle,  1492 

antrum  of,  1508 
Eustachian  tube,  1501 
mastoid  cells,  1504 
pract.  consid.,  1504 
suprameatal  triangle,  1510 
suprameatic  spine,  1508 
tympanum  of,  1492 
Ear-point,  14S4 
Ectoblast,  23 


THIS   VOLUME    CONTAINS    PAGES   1    TO   995. 


INDEX. 


1007 


Egg-nucleus,  16 
Elastic  tissue,  76 

development  of,  77 
Elastin,  83 
Elbow-joint,  301 

landmarks  of,  308 

movements  of,  303 

pract.  consid.,  305 
Embryo,  stage  of,  56 
Eminentia  hypoglossi,  1098 

teres,  1097 
Enamel,  1548 

formation  of,  1561 
Enamel-cells,  1561 
Enamel-cuticle,  1550 
Enamel-organ,  1560 
Enarthrosis,  113 
Encephalon,  1055 
End-bulbs  of  Krause,  1016 
End-knobs   of    free   sensory   nerve-endings, 

1015 
Endocardium,  702 

Endolymph  of  membranous  labyrinth,  1514 
Endometrium,  2007 
Endomysium,  458 
Endoneurium,  1006 
Endothelium,  71 
Enophthalmos,  1439 
Ensiform  cartilage  of  sternum,  156 
Entoblast,  23 
Entoskeleton,  84 
Ependymal  cells,  1004 
Epicardium,  702 
Epidermis,  1385 
Epididymis,  1947 

appendix  of,  1949 

canal  of,  1948 

digital  fossa  of,  1947 

globus  major  of,  1947 
minor  of,  1947 

nerves  of,  1948 

structure  of,  1947 

vasa  abberrantia  of,  1950 

vessels  of,  1948 
Epiglottis,  1816 

ligaments  of,  181 7 

movements  of,  181 7 
Epimysium,  458 
Epineurium,  1006 
Epiphysis,  1124 

ossification  of,  98 
Epispadias,  1928 
Epithalamus,  n 23 
Epithelium  of  chorion,  49 

columnar,  69 

glandular,  70 

modified,  70 

pigmented,  70 

specialized,  70 

squamous,  68 

stratified,  68 

transitional,  69 
Epitrichium,  1401 
Eponychium,  1403 
Epoophoron,  2000 
Erythroblasts,  92 
Erythrocytes,  681 

development  of,  687 
Ethmoid  bone,  191 

articulations  of,  194 
bulla  of,  194 
cells  of,  192 
development  of,  194 


Ethmoid  turbinate  bone,  middle  of,  193 
superior  of,  193 
uncinate  process  of,  193 
Eustachian  tube,  1501 

blood-vessels  of,  1504 
cartilaginous  portion,  1502 
mucous    membrane  of,  1503 
muscles  of,  1503 
osseous  portion,  1502 
pract.  consid.,  1507 
valve,  694 
Exoccelom,  32 
Exophthalmos,  1439 
Exoskeleton,  84 
Extremity,  lower,  332 

landmarks  of,  669 
lymphatics  of,  991 
upper,  landmarks  of,  618 
lymphatics  of,  961 
Eye,  1436 

development  of,  1480 
lymphatics  of,  949 
plica  semilunaris  of,  1443 
pupil  of,  1459 
Eyeball,  1448 

aqueous  humor  of,  1476 
chamber  anterior  of,  1476 

posterior  of,  1476 
choroid  of,  1455 
ciliary  body  of,  1457 

processes  of,  1457 
cornea  of,  1450 
fovea  centralis  of,  1466 
iris  of,  1459 

lens,  crystalline  of,  1471 
macula  lutea  of,  1466 
movements  of,  505 
optic  nerve  of,  1469 
ora  serrata  of,  1467 
pract.  consid.,  1449 
retina  of,  1462 
sclera  of,  1449 
vascular  tunic  of,  1454 
vitreous  body  of,  1473 
Eye-lashes,  1442 
Eyelids,  1441 

blood-vessels  of,  1445 
development  of,  1483 
lymphatics  of,  1445 
nerves  of,  1446 
pract.  consid.,  1446 
structure  of,  1443 

Face,  222 

architecture  of,  228 
development  of,  62 
landmarks  of,  246 

muscles  and  fascia?,  pract.  consid.,  492 
pract.  consid.,  242 
Falciform  ligament,  1745 
Fallopian  tube,  1996 

changes  in,  1999 

course  of,  1997 

development  of,  1999 

fimbria?  of,  1997 

infundibulum  of,  1997 

isthmus  of,  1997 

lymphatics  of,  98S 

nerves  of,  1999 

pract.  consid.,  1999 

relations  of,  1997 

structure  of,  1997 

vessels  of,  1998 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


ioo8 


INDEX. 


Fallopius,  aqueduct  of,  181 
Falx  cerebelli,  1200 

cerebri,  1199 
Fascia  or  fascia?,  470 

of  abdomen,  515 

anal,  1678 

of  ankle,  pract.  consid.,  666 

antibrachial,  592 

of  anus,  1675 

of  arm,  pract.  consid.,  589 

of  axilla  and  shoulder,  pract.  consid.,  579 

axillary,  574 

of  back,  508 

bicipital  (semilunar),  586 

brachial,  58 5 

bucco-pharyngeal,  48S 

of  buttocks,  pract.  consid.,  641 

of  Camper,  515 

cervical,  542 

of  Colles,  562 

of  cranium,  pract.  consid.,  489 

cremasteric,  i960 

cribriform,  635 

crural,  647 

dentata,  n  66 

of  face,  pract.  consid.,  492 

of  foot,  pract.  consid.,  666 

of  hand,  606 

of  hip  and  thigh,  pract.  consid.,  642 

iliac,  624 

infundibuliform,  524 

intercolumnar  (external  spermatic),  524 

of  knee,  pract.  consid.,  645 

lata,  633 

of  leg,  pract.  consid.,  66s 

obturator,  559 

of  orbit,  504 

palmar,  606 

palpebral,  1438 

parotido-masseteric,  474 

pectoral,  568 

pelvic,  558 

perineal,  superficial,  562 

plantar,  659 

prevertebral,  543 

rectal,  1678 

recto-vesical,  1678 

of  rectum,  1675 

of  scalp,  pract.  consid.,  489 

of  Scarpa,  515 

temporal,  475 

transversalis,  520 
Fasciculus,  auriculo-ventricular  of  heart,  701 

posterior  longitudinal,  1 1 1 6 

retroflexus,  1124 

solitarius,  1074 
Fat,  orbital,  1437 
Fat-cells,  79 
Fauces,  isthmus  of,  1569 

pillars  of,  1569 
Femoral  canal,  625 

ring,  625 
Femur,  352 

development  of,  359 

landmarks  of,  366 

pract.  consid.,  361 

surface  anatomy,  360 

variations,  sexual  and  individual,  359 
Fertilization,  18 
Fibres,  intercolumnar,  524 
Fibrin,  canalized,  of  chorion,  49 
Fibro-cartilage,  82 
Fibrous  tissue,  74 


Fibrous  tissue,  development  of,  76 
Fibula,  390 

development  of,  393 
pract.  consid.,  393 
Fillet,  decussation  of,  1070 

median,  1 1 1 5 
Fimbria,  n  59 

hippocampi,  1165 
Fissure,  calcarine,  n 46 

calloso-marginal,  1139 
central,  of  cerebrum,  113  7 
collateral,  1139 
ethmoidal,  141 1 
of  Glaser,  178 
palpebral,  1441 
parieto-occipital,  1138 
portal,  of  liver,  1708 
pterygo-maxillary,  204 
of  Rolando,  113  7 
sphenoidal,  188 
Speno-maxillary,  222 
(sulci)  cerebral,  1135 
of  Sylvius,  1 136 
Fistula,  cervical,  61 
Flexure,  cephalic,  58 

cervical,  of  embryo,  59 
dorsal,  of  embryo,  59 
sacral,  of  embryo,  59 
Flocculus,  1085 
Foetus,  membranes  of,  30 
stage  of,  63 

eighth  month,  66 

week,  64 
fifth  month,  66 

week,  63 
fourth  month,  65 
ninth  month,  66 
seventh  month,  66 

week,  64 
sixth  month,  66 

week,  63 
third  month,  65 
Follicles,  Graafian,  1988 
Fontana,  spaces  of,  1452 
Fontanelles,  231 
Foot,  articulations  of,  440 
as  whole,  447 
bones  of,  419 

landmarks  of,  437 
pract.  consid.,  436 
joints  of,  landmarks  of,  453 
landmarks  of,  672 
muscles  of,  659 

and  fascia?  of,   pract.   consid.,    666 
surface  anatomy,  449 
synovial  cavities  of,  447 
Foramen  or  foramina,  caecum,  1574 
ethmoidal,  anterior,  192 

posterior,  192 
jugular,  220 
of  Luschka,  n  00 
of  Magendie,  1100 
mastoid,  180 
of  Monro,  1 131 
optic,  189 
ovale,  188 

of  heart,  695 
pterygo-spinosum,  190 
rotundum,  187 
sacro-sciatic,  great,  341 

lesser,  341 
sphenoidal,  187 
spheno-palatine,  204 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


INDEX. 


1009 


Foramen  or  foramina,  spinosum,  iSS 

stylo-mastoid,  182 

thyroid  (obturator),  337 

of  vena  cava,  of  diaphragm,  557 

of  Vesalius,  188 

of  Winslow,  1746 
Forceps  anterior,  of  corpus  callosum,  1157 

posterior,  of  corpus  callosum,  11 58 
Forearm,  281 

as  whole,  299 

intrinsic  movements  of,  299 

motion  of  on  humerus,  303 

pract.  consid.,  603 
Fore-brain,  1059 
Formatio  reticularis,  1076 

reticularis  alba,  1076 
grisea,  1074 
Fornix,  1158 

pillars  of,  anterior,  n  59 
posterior,  1159 
Fossa  or  fossa?, 

duodenojejunal,  1647 

glenoid,  178 

hyaloidea,  1473 

ileo-caecal,  1666 

infraspinous,  250 

inguinal,  inner,  526 
lateral,  1743 
median,  1742 
outer,  526 

interpeduncular,  1107 

intersigmoid,  167 1 

ischio-rectal,  1678 

jugular,  182 

nasal,  1409 

navicular  of  urethra,  1924 

ovalis,  695 

ovarian,  1986 

pararectal,  1744 

paravesical,  1744 

pericaecal,  1666 

pineal,  1106 

pituitary,  186 

retro-colic,  1667 

of  Rosenmiiller,  1598 

spheno-maxillary,  227 

subscapular,  249 

supraspinous,  250 

supratonsillar,  1600 

supravesical,  526 

Sylvii,  1 137 

temporal,  218 

zygomatic,  227 
Fourchette,  2022 
Fourth  ventricle,  1096 

choroid  plexus  of,  11 00 
floor  of,  1096 
,  roof  of,  1099 

Fovea  centralis,  1466 

vagi,  109S 
Frenulum  of  Giacomini,  1166 
Frenum  of  prepuce,  1966 

of  tongue,  1573 
Frontal  bone,  194 

articulations  of,  197 
development  of,  197 

lobe,  1 139 

sinus,  1423,  226  (bony) 
Fundamental  embryological  processes,  26 
Funiculus  cuneatus,  1066 

gracilis,  1066 

of  Rolando,  1067 

Furrows,  visceral,  59 

external,  61 


Furrows,  inner,  61 

inner,  second,  62 
inner,  third,  62 

Galen,  vein  of,  856 
Gall-bladder,  17 19 

cystic  duct  of,  1720 

fossa  of,  1708 

lymphatics  of,  981 

nerves  of,  1720 

pract.  consid.,  1729 

vessels  of,  17 19 
Ganglion  or  ganglia,  1007 

Arnold's,  1246 

basal,  1 1 69 

cervical  inferior  (sympathetic),  1362 
middle  (sympathetic),  1362 
superior  (sympathetic),  1359 

ciliary,  1236 

coccygeal  (impar),  sympathetic,  1367 

development  of,  1012 

of  Froriep,  1380 

Gasserian,  1232 

geniculate,  1252 

habenute,  n  23 

impar,  1367 

interpeduncular,  n 24 

jugular,  of  glosso-pharyngeal,  1263 
of  vagus,  1267 

lenticular,  1236 

Meckel's,  1240 

mesenteric,  inferior,  1373 
superior,  1372 

nodosum  of  vagus,  1268 

ophthalmic,  1236 

otic,  1246 

petrous,  of  glosso-pharyngeal,  1264 

semilunar,  sympathetic,  1369 

spheno-palatine,  1240 

spinal,  1279 

spiral,  1257 

spirale  of  cochlea,  1522 

splanchnic,  great,  sympathetic,  1365 

submaxillary,  1247 

sympathetic,  1009 

of  sympathetic  system,  1356 

vestibular,  1259 
Ganglion-crest ,  1  o  1 2 
Gartner's  duct,  2001 
Gasserian  ganglion,  1232 
Gastric  glands,  1623 
Gastro-pulmonary  system,  1527 
Gastrula,  25 
Gelatin,  S3 
Geniculate  bodies,  lateral,  1107 

median,  1107 

(internal)  internal  structure  of,  n  10 

ganglion,  1252 
Genital  cord,  2038 

folds,  2043 

organs,  external,  development  of,  2043 
female,  2021 

pract.  consid.,  2027 

ridge,  2038 

tubercle,  2043 
Genu  of  corpus  callosum,  n 55 
Germinal  spot,  16 
Gestation,  ectopic,  1999 
Giacomini,  frenulum  of,  11 66 
Gianuzzi,  crescents  of,  1534 
Gimbernat,  ligament  of,  523 
Ginglymus,  113 
Giraldes,  organ  of,  1950 
Glabella,  228 


THIS  VOLUME   CONTAINS   PAGES  1   TO  996. 


INDEX. 


Gladiolus  of  sternum,  155 
Gland  or  glands,  1531 

alveolar  (saccular)  compound,  1535 
(saccular)  simple,  1535 

anal,  1674 

areolar,  2028 

of  Bartholin,  2026 

of  Blandin,  1577 

blood-vessels  of,  1535 

of  Bowman,  141 5 

of  Brunner,  1639 

cardiac  of  stomach,  1624 

carotid,  1809 

ceruminous,   1489 

ciliary,  1400 

circumanal,  1400 

coccygeal,  1810 

of  Cowper,  1984 

cutaneous,  1397 

gastric,  1623 

of  Henle,  1445 

of  intestines,  1637 

of  Krause,  1445 

lachrymal,  1477 
ducts  of,  1477 

of  Lieberkuhn,  1637 

of  Luschka,  1810 

lymphatics  of,  1536 

mammary,  2027 

Meibomian  (tarsal),  1444 

of  Moll,  1444 

of  Montgomery,  2028 

mucous,  1534 

nerves  of,  1536 

of  Nuhn,  1577 

parotid,  1582 

prostate,  1975 

pyloric,  1624 

salivary,  1582 

sebaceous,  1397 

serous,  1534 

sexual,  development  of,  2038 

sublingual,  1585 

submaxillary,  1583 

sweat,  1398 

duct  of,  .1399 
structure  of,  1399 

of  tongue,  1575 

tubo-alveolar,  1532 

tubular,  compound,  1532 
simple,  1532 

of  Tyson,  1966 

unicellular,  1531 

of  Zeiss,  1444 
Glans  of  clitoris,  2024 

penis,  1968 
Glaser,  fissure  of,  178 
Glisson's  capsule  of  liver,  1708 
Globus  pallidus,  11 70 
Goblet-cells,  70 

Golgi-Mazzoni  corpuscles,  1019 
Gonion,  228 
Graafian  follicles,  1988 
Grandry,  corpuscles  of,  1016 
Growth,  6 

of  bone,  101 
Gudden,  inferior  commissure  of,  n  10 
Gums,  1567 

pract.  consid.,  1590 
Gustatory  cells,  1435 

Gyrus  or  gyri,  callosal  (fornicatus) ,  n 50 
(convolutions)  cerebral,  1 1 3  5 

dentate,  1166 


Gyrus  or  gyri,  development  of,  1190 
hippocampal,  1151 

Hair-cells  (auditory)  inner,  1520 

outer,  1520 
Hair-follicle,  1392 

-   blood-vessels  of,  1394 
nerves  of,  1394 
Hairs,  1389 

arrangement  of,  139 1 
developmerlt-of,  1401 
growth  of,  1402 
structure  of,  1391 
whorls  of,  139 1 
Hair-shaft,  1391 

Hamular  process  of  inner  pterygoid  plate,  189 
Hamulus  of  bony  cochlea.  15 14 
Hand,  309 

deep  fascia  of,  606 
landmarks  of,  320 
lymphatics  of,  964 
muscles  of,  606 
pract.  consid.,  613 
surface  anatomy  of,  328 
Harelip,  1589 

Hassall,  corpuscles  of,  1799 
Haversian  canals  of  bone,  88 

system  of  bone,  86 
Head,  movements  of,  142 
Heart,  annuli  fibrosi  of,  698 
annulus  ovalis,  695 

of  Vieussens,  695 
architecture  of  walls,  700 
auricles  of,  693 
blood-vessels  of,  703 
canal  auricular  of,  705 
chambers  of,  693 
chordae  tendineae  of,  697 
columnas  carneae  of,  697 
development  of,  705 
endocardium  of,  702 
epicardium  of,  702 
fasciculus  auriculo-ventricular,  701 
foramen  ovale  of,  695 
fossa  ovalis  of,  695 
general  description  of,  689 
His's  bundle,  701 
lymphatics,  703 
muscle  of,  462 
muscles,  pectinate  of,  695 
nerve-endings  in,  1015 
nerves  of,  704 
position  of,  692 
practical  considerations,  710 
relations  of,  693 
septum,  aortic,  707 
auricular  of,  694 
intermedium,  706 
interventricular  of,  696 
primum,  706 
secundum,.  70S 
spurium,  707 
Thebesian  veins  of,  694 
tubercle  of  Lower,  69  s 
valves,  Eustachian,  694 

auriculo-ventricular,  699 
mitral,  699 
position  of,  692 
structure  of,  703 
Thebesian,  695 
tricuspid,  699 
vein,  oblique  of,  695 
ventricles  of,  696 


THIS  VOLUME   CONTAINS    PAGES  1    TO  995. 


INDEX. 


Heidenhain,  demilunes  of,  1534 
Helicotrema,  1514 
Helix,  1484 

Hemispheres,  association  fibres  of,  1182 
of  cerebellum,  1082 
cerebral,  1133 
commissural  fibres  of,  n  84 
lobes  of,  1139 
projection  fibres  of,  1186 
white  centre  of,  1182 
Henle,  glands  of,  1445 

loop  of,  1 88 1 
Hensen,  node  of,  25 
Herbst,  corpuscles  of,  10 19 
Hernia,  abdominal,  1759 
diaphragmatic,  1778 
femoral,  1773 
funicular,  1768 
infantile,  1767 
inguinal,  1763 
direct,  1770 
indirect,  1766 
internal     (intra-abdominal    retroperito- 
neal), 1779 
interparietal,  1768 
labial,  1769 
lumbar,  1777 
obturator,  1777 
perineal,  1778 
sciatic,  1778 
scrotal,  1769 
umbilical,  1775 

acquired,  1776 
congenital,  1775 
ventral,  1776 
Hesselbach,  ligament  of,  525 

triangle  of,  526 
Hiatus,  aortic,  of  diaphragm,  557 
Fallopii,  181 

oesophageal,  of  diaphragm,.  557 
semilunaris,  of  nasal  cavity,  194 
of  nose,  141 1 
Highmore,  antrum  of,  1422 
Hind -brain,  1061 
Hip,  landmarks  of,  669 

muscles  and  fasciae  of,  pract.  consid.,  642 
Hip-joint,  367 

movements  of,  373 
pract.  consid.,  374 
synovial  membrane  of,  372 
Hippocampus,  1165 
His's  bundle,  of  heart,  701 
Histogenesis  of  neuroglia,  10 10 

of  neurones,  ion 
Homologue,  4 
Horner,  muscle  of,  4S4 
Howship,  lacunae  of,  97 
Humerus,  265 

development  of,  269 
pract.  consid.,  270 
sexual  differences,  269 
structure  of,  269 
surface  anatomy,  270 
Humor,  aqueous,  1476 
Hunter's  canal,  62S 
Hvaloid  canal,  1474 
Hyaloplasm,  8 
Hydatid  of  Morgagni,  2002 
Hydramnion,  42 
Hymen,  2016 
Hyoid  bone,  216 

development  of,  216 
Hyomandibular  cleft,  61 


Hypogastric  lymphatic  plexus,  984 
Hypophysis,  1806 
Hypospadias,  1927 
Hypothalamus,  n 27 
Hypothenar  eminence,  607 

Ileo-caecal  fossae,  1666 

valve,  1661 
Ilio-femoral  ligament,  369 
Iiio-pectineal  line,  334 
Ilio-tibial  band,  634 
Ilium,  332 
Implantation,  35 
Impregnation,  iS 
Incisor  teeth,  1  543 
Incus,  1497 

Inferior  caval  system  of  veins,  898 
Infundibulum,  n 29 

of  nasal  cavity,  194 
of  nose,  14 1 1 
Inguinal  canal,  523 

lymphatic  plexus,  991 
Inion,  228 
Innominate  bone,  332 

structure  of,  337 
Insula,  1 1 49 
Intersigmoid  fossa,  1671 
Intervertebral  disks,  132 

Intestine    or   intestines,    development     and 
growth  of,  1 67 1 
glands  of,  1637 
large,  1657 

appendices  epiploieae,  1660 
blood-vessels  of,  1660 
glands  of  Lieberkuhn  of,  1657 
lymphatics  of,  1660 
lymphatic  tissue  of,  1658 
nerves  of,  1660 
peritoneum  of,  1670 
pract.  consid.,  16S0 
structure  of,  1657 
taenia  coli  of,  1660 
lymph-nodules  of,  1640 
small    1633 

blood-vessels  of,  1642 
glands  of  Lieberkuhn  of,  1637 
lymphatics  of,  1643 
nerves  of,  1643 
Peyer's  patches  of,  1640 
pract.  consid.,  1652 
structure  of,  1634 
valvulae  conniventes  of,  1636 
villi  of,  1635 
solitary  nodules  of,  1640 
Involuntary  muscle,  10 15 
Iris,  1459 

pract.  consid.,  1461 
structure  of,  1460 
Irritability,  6 
Ischio-rectal  fossa,  1678 
Ischium,  336 
Islands  of  Langerhans,  1735 

of  Reil,  1 149 
Isthmus  of  fauces,  1569 
rhombencephali,  1061 

Jacobson's  nerve,  1264 

organ,  14 17 

development  of,  1432 
Jejuno-ileum,  1649 

blood-vessels  of,  1652 

lymphatics  of,  1652 

mesentery  of.  1650 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


INDEX. 


Jejuno-ileum,  nerves  of,  1652 

topography  of,  1650 
Joint  or  joints,  of  ankle,  43S 

calcaneo-astragaloid,  posterior,  445 

calcaneo-cuboid,  446 

calcaneo-scapho-astragaloid,       anterior, 

445 
capsule  of,  no 
of  carpus,   metacarpus   and  phalanges, 

pract.  consid.,  330 
costo-central,  160 
costo-sternal,  160 

motions  in,  166 
costo-transverse,  160 
costo-vertebral,  motions  in,  165 
crico-arytenoid,  181 6 
cri  co-thyroid,  1815 
of  ear  ossicles,  1498 
elbow,  301 
fixed,  107 

general  considerations,  107 
half,  108 
of  hip,  367 
interchondral,  160 
intersternal,  159 
of  knee,  400 

limitation  of  motion,  112 
metatarso-phalangeal,  447 
modes  of  fixation,  112 
of  pelvis,  337 

of  pelvis,  pract.  consid,  350 
radio-ulnar,  297 

inferior,  pract.  consid.,  308 
saddle,  113 

scapho-cubo-cuneiform,  446 
of  shoulder,  274 
synovial  membrane  of,  no 
tarso-metatarsal,  446 
of   tarsus,    metatarsus    and    phalanges, 

pract.  consid.,  45 
true,  108 

motion  in,  112 

structure  of,  109 

varieties  of,  113 
vessels  and  nerves  of,  1 1 1 
Jugular  ganglion,  of  glosso-pharyngeal,  1263 

of  vagus,  1267 
plexus,  lymphatics,  956 

Karyokinesis,  11 

Karyosomes,  9 

Kidney  or  kidneys,  1869 

architecture  of,  1875 

blood-vessels  of,  1884 

capsule  of,  1869 

cortex  of,  1876 

development  of,  1937 

ducts  of,  1S94 

fixation  of,  1871 

glomeruli  of,  1876 

hilum  of,  1869 

labyrinth  of,  1876 

lobule  of,  1875 

loop  of  Henle  .of ,  18S1 

lymphatics  of,  1885 

Malpighian  body  of,  1879 

medulla  of,  1876 

medullary  rays  of,  1876 

movable,  1888 

nerves  of,  1886 

papillae  of.  1875 

papillary  ducts  of,  1S82 

pelvis  of,  1894 


Kidney  or  kidneys,  position  of,  1870 

pract.  consid.,  1887 

pyramids  of,  1876 

relations  of,  1873 

sinus  of,  1874 

structure  of,  1877 

supporting  tissue  of,  1883 

surfaces  of,  1869 

tubule,  collecting  of,  18S2 
connecting  of,  1882 
distal  convoluted  of,  1882 
proximal  convoluted  of,  188c 
spiral  of,  1880 
uriniferous  of,  1877 
Knee,  landmarks  of,  671 

muscles  and  fascia?  of,  pract.  consid.,  645 
Knee-joint,  400 

bursae  of,  406 

capsule  of,  400 

landmarks  of,  416 

movements  of,  40S 

pract.  consid.,  409 

semilunar  cartilage  of,  402 

synovial  membrane  of,  405 
Krause,  end-bulbs  of,  1016 

glands  of,  1445 
Kupffer,  cells  of,  1717 

Labia  major,  2021 
minora,  2022 
nerves  of,  2024 
vessels  of,  2023 
Labyrinth,  membranous,  1514 

blood-vessels  of,  1522 

canalis  reuniens  of,  151 5 

cochlea  of,  1 5 1 7 

ductus  endolymphaticus  of,  151 4 

endolymph  of,  1514 

macula?  acusticae  of,  1516 

saccule  of,  151 5 

semicircular  canals  cf,  151 5 

utricle  of,  1514 
osseous,  1 51 1 

cochlea  of,  15 13 

semicircular  canals  of.  1 5 1 2 

vestibule  of,  1511 
Lachrj'mal  apparatus,  1477 

pract.  consid.,  1479 
bone,  207 

articulations  of,  207 

development  of,  207 
canaliculi,  1478 
caruncle,  1443 
gland,  1477 
lake,  1443 
papillae,  1478 
puncta,  1478 
sac,  1478 
Lactation,  2029 
Lacteals,  1643 
Lacunae,  of  bone,  86 
of  cartilage,  80 
of  Howship,  97 
Lambda,  228 

Lamina  cinerea  (terminalis),  1130 
fusca,  1450 
suprachoroidea,  1456 
Landmarks,  of  abdomen,  531 
of  ankle  and  foot,  672 
of  bones  of  foot,  437 
of  buttocks  and  hip,  669 
of  clavicle,  260 
of  elbow-joint,  308 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


1013 


Landmarks,  of  face,  246 

of  femur,  366 

of  fibula,  396 

of  hand,  320 

of  joints  of  foot,  453 

of  knee,  671 

of  knee-joint,  416 

of  leg,  671 

of  lower  extremity,  669 

of  male  perineum,  19 18 

of  neck,  554 

of  pelvis,  349 

of  radius,  296 

of  scapula,  255 

of  shoulder-joint,  280 

of  skull,  240 

of  spine,  146 

of  surface  of  thorax,  186S 

of  thigh,  670 

of  thorax,  170 

of  tibia,  390 

of  ulna,  287 

of  upper  extremity,  618 

of  wrist-joint,  330 
Langerhans,  islands  of,  1735 
Lanugo,  66 

Laryngo-pharynx,  1598 
Larynx,  1813 

age  changes  of,  1828 

arytenoid  cartilages  of,  181 6 

cornicuke  laryngis,  181 7 

cricoid  cartilage  of,  1813 

cuneiform  cartilages  of,  181 7 

development  of,  1862 

elastic  sheath  of,  1 8 1 7 

epiglottis,  181 6 

form  of,  1818 

lymphatics  of,  958 

mucous  membrane  of,  1823 

muscles  of,  1824 

nerves  of,  1827 

ossification  of,  1818 

position  and  relations  of,  1828 

pract.  consid.,  1828 

region,  glottic  of,  1820 
infraglottic  of,  1823 
supraglottic  of,  181S 

sexual  differences  of,  1828 

thyroid  cartilage  of,  1814 

ventricle  (sinus)  of,  1822 

vessels  of,  1826 

vocal  cords,  false  of,  1820 
true  of,  1820 
ligaments  of,  181 8 
Leg,  bones  of,  as  one  apparatus,  397 
surface  anatomy,  397 

framework  of,  382 

landmarks  of,  671 

lymphatics,  deep  of,  994 
superficial  of,  993 

muscles  and  fasciae  of,  pract.  consid.,  665 
Lens,  crystalline,  1471 

development  of,  14S1 
pract.  consid.,  1473 
suspensory  apparatus  of,  1475 
Leptorhines,  1404 
Leucocytes,  684 

development  of,  688 

varieties  of,  685 
Lieberkuhn,  glands  of,  1637 
Lieno-phrenic  fold,  1785 
Ligament  or  ligaments,  112 

alar,  of  knee-joint,  405 


Ligament  or  ligaments,  anterior  annular,  of 
ankle,  647 
of  wrist,  325 
arcuate,  external,  557 

internal,  557 
atlanto-axial,  anterior,  137 
atlanto-axial,  posterior,  137 
of  auricle,  1486 
broad,  of  uterus,  2004 
broad,  vesicular  appendages  of,  2002 
check,  of  orbit,  1438 
of  Colles,  523 
common  anterior  and  posterior,  of  spine, 

coraco-acromial,  256 
coraco-clavicular,  262 

conoid  part,  262 

trapezoid  part,  262 
coronary,  of  liver,  1 7  2 1 
costo-clavicular  or  rhomboid,  262 
cotyloid,  of  hip-joint,  367 
crucial,  of  knee-joint,  404 
cruciform,  of  axis,  136 
deltoid  (lat.  int.)  of  ankle-joint,  439 
denticulate,  of  spinal  cord,  1023 
dorsal,  of  foot,  442 
duodeno-hepatic,  1644 
of  epiglottis,  181 7 
external  check,  of  eyeball,  505 
falciform,  1745 
gastro-phrenic,  1747 
of  Gimbernat,  523 
of  Hesselbach,  525 
ilio-femoral,  369 
ilio-lumbar,  339 
interarticular  of  ribs,  160 
interclavicular,  262 
interosseous,  of  foot,  441 
interspinous,  134 
intertransverse,  135 
ischio-femoral,  370 

of  laminae  and  processes  of  vertebrae,  133 
lieno-renal,  1747 
of  liver,  1721 

metacarpal,  superficial  transverse,  607 
nuchae,  134 
occipito-atlantal,  accessory,  137 

anterior,  137 

posterior,  137 
occipito-axial,  137 
odontoid,  or  check,  136 
orbicular,  of  radius,  297 
of  ovary,  1987 
palpebral,  1441 

internal,  484 
patellae,  400 
pectinate  of  iris,  1452 
of  pelvis,  337 
of  pericardium,  716 
plantar,  444 

posterior  annular,  of  wrist,  325 
of  Poupart,  523 
pterygo-mandibular,  4S8 
radio-ulnar,  297 
round,  of  hip-joint,  370 

of  liver,  1721 

of  uterus,  2005 
sacro-iliac,  posterior,  338 
sacro-sciatic,  339 

great  or  posterior,  339 

lesser  or  anterior,  341 
of  scapula,  256 
of  shoulder-joint,  274 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


ioi4 


INDEX. 


Ligament  or  ligaments,  spino-glenoid,  257 
stylo-mandibular,  475 
subflava,  133 

suprascapular  or  transverse,  256 
supraspinous,  133 
suspensory,  of  lens,  1475 

of  orbit,  1438 

of  ovary,  1986 
thyro-arytenoid,  inferior,  1818 

superior,  181 7 
thyro-hyoid,  181 5 
transverse,  of  atlas,  136 
triangular,  of  liver,  1721 

of  perineum,  563 
of  vertebral  bodies,  132 
of  Winslow,  of  knee-joint,  401 
of  wrist  and  metacarpus,  320 
Limb,  lower,  muscles  of,  623 
Limbic  lobe,  n  50 
Linea  alba,  522 

semilunaris,  of  abdomen,  532 
transversa,  of  abdomen,  532 
Linin,  9 
Lips,  1538 

lymphatics  of,  951 
muscles  of,  1540 
nerves  of,  1542 
pract.  consid.,  1590 
vessels  of,  1542 
Liquor  amnii,  31 

pericardii,  714 
Littre,  glands  of,  1925 
Liver,  1705 

bile-capillaries  of,  1715 
biliary  apparatus,  17 18 
blood-vessels  of,  1709 
borders  of,  1707 
caudate  lobe  of,  1709 
cells  of  Kupffer,  1717 
common  bile-duct,  1720 
cystic  duct  of,  1720 
development  and  growth  of,  1723 
fissure  of  ductus  venosus  of,  1707 
fossa  for  gall-bladder  of,  1708 
gall-bladder  of,  17 19 
Glisson's  capsule  of,  1708 
hepatic  artery  of,  1 7 1 1 

ducts  of,  1 7 18 

veins  of,  17 10 
impression,  oesophageal  of,  1708 

renal  of,  1709 
intralobular  connective  tissue  of,  1717 

bile-ducts  of,  1717 

veins  of,  17 10 
ligaments  of,  1721 

coronary,  1721 

falciform,  1721 

round,  1721 

triangular,  1721 
lobes  of,  1706 

lobular  blood-vessels  of,  17 13 
lobules  of,  1 7 1 2 
lymphatics  of,  1711 
nerves  of,  r  711 
non-peritoneal  area  of,  1707 
peritoneal  relations  of,  1721 
portal  (transverse)  fissure  of,  1708 

vein  of,  1709 
position  of,  T722 
pract.  consid.,  1726 
quadrate  lobe  of,  1709 
size  of,  1706 
Spigelian  lobe  of,  1707 


Liver,  structure  of,  1 7 1 2 

sublobular  veins  of,  17 10 

surfaces  of,  1707 

tuber  omentale  of,  1709 

umbilical  fissure  of,  1708 
notch  of,  1707 

weight  of,  1706 
Liver-cells,  17 14 
Lobe  or  lobes,  cerebral,  113  5 

frontal,  1139 

of  hemispheres,  1 139 

limbic,  1 1 50 

occipital,  1 145 

olfactory,  1 1 5 1 

parietal,  11 43 

temporal,  1147 
Lobule  of  auricle,  1484 
Loin,  pract.  consid.,  530 
Lordosis,  144 

Lumbar  plexus,  lymphatic,  973 
Lumbo-sacral  cord,  1331 
Lung  or  lungs,  1843 

air-sacs  of,  1850 

alveoli  of,  1850 

atria  of,  1850 

blood-vessels  of,  1853 

borders  of,  1843 

development  of,  1861 

external  appearance  of,  1846 

fissures  of,  1845 

ligament  broad  of,  1858 

lobes  of,  1845 

lobule  of,  1849 

nerves  of,  1855 

physical  characteristics  of,  1846 

pract.  consid.,  1864 

relations  to  chest-walls,  changes  in,  1863 
to  thoracic  walls,  1855 

roots  of,  1838 

dimensions  of,  1840 
nerves  of,  1839 
relations  of,  1840 

structure  of,  r8si 

surfaces  of,  r843 

vessels  of,  1839 
Lunula,  of  nail,  1395 
Luschka,  foramina  of,  n  00 

gland  of,  1 810 
Lutein  cells,  1990 
Luys,  nucleus  of,  1128 
Lymphatic  or  lymphatics,  of  abdomen,  97? 

of  abdominal  walls,  976 

of  arm,  deep,  965 
superficial,  963 

of  bile-duct,  981 

of  bla.dder,  985 

of  bone,  93 

of  brain,  948 

of  brain  and  meninges,  948 

broncho-mediastinal  trunk,  968 

capillaries,  933 

of  cervical  skin  and  muscles,  958 

of  cheeks,  951 

of  diaphragm,  970 

duct,  right,  945 

of  ear,  950 

of  eye  and  orbit,  949 

of  eyelids,  1445 

of  Fallopian  tubes,  988 

of  gall-bladder,  981 

of  glands,  1536 

of  gums,  951 

of  hand,  964 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


1015 


Lymphatic  or  lymphatics,  of  the  head,  945 
of  heart,  970 
hemolymph  nodes,  936 
intercostal,  969 
of  intestine,  large,  978 

small,  977 
jugular  trunk,  958 
of  kidney,  982 
lacteals,  931 
of  larynx,  958 
of  leg,  deep,  994 

superficial,  993 
of  lips,  951 
of  liver,  980 
of  lower  extremity,  991 
mammary  gland,  968 
of  meninges,  948 
of  muscle,  non-striated,  456 
of  nasal  fossa,  1426 

region,  951 
nodes,  935 
of  nose,  1407 
of  oesophagus,  971 
of  palate,  954 
of  pancreas,  979 
of  pelvis,,  983 
of  pericardium,  716 
of  perineum,  987 
of  pharynx,  954 
of  prostate  gland,  985 
of  rectum,  1680 

of   reproductive    organs,    external,    fe- 
male, 987 

external,  male,  986 

internal,  female,  988 

internal,  male,  987 
of  retina,  1468 
of  scalp,  948 
of  seminal  vesicles,  988 
of- skin,  1388' 
of  small  intestine,  1643 
of  spleen,  982 
of  stomach,  976 
of  striated  muscle,  464 
subclavian  trunk,  963 
of  suprarenal  body,  983 
system,  931 
of  teeth,  951 
of  testis,  987 
thoracic  duct,  941 

pract.  consid.,  944 
of  thorax,  966 

cutaneous,  968 
of  thyroid  gland,  959 
of  tongue,  952 
of  tonsils,  954 
of  trachea,  958 
of  upper  extremity,  961   ' 
of  ureter,  982 
of  urethra,  986 
of  uterus,  989 
of  vagina,  989 
of  vas  deferens,  988 
vessels,  development  of,  939 
Lymph-corpuscles,  931 

Lymph-nodes  of  abdomen,  pract.  consid.,  990 
abdominal,  visceral,  974 
ano-rectal,  976 
anterior  auricular,  946 
appendicular,  975 
of  arm,  pract.  consid.,  965 
of  axilla,  pract.  consid.,  965 
axillary,  961 


Lymph-nodes,  brachial,  deep,  961 
superficial,  961 

bronchial,  967 

buccinator,  947    ' 

cervical,  deep,  inferior,  958 
superior,  957 

of  Cloquet,  992 

cceliac,  973 

delto-pectoral,  961 

development  of,  940 

epigastric,  972 

epitrochlear,  961 

facial,  947 

gastric,  974 

of  head,  pract.  consid.,  955 

hepatic,  975 

hypogastric,  984 

iliac,  circumflex,  972 
internal,  984 

inguinal,  991 

intercostal,  966 

of  intestine,  1640 

jugular  plexus,  956 

of  leg,  pract.  consid.,  994 

lingual,  947 

mammary,  internal,  966 

mandibular,  947 

mastoid,  945 

maxillary,  947 

mediastinal,  anterior,  967 
posterior,  967 

mesenteric,  975 

mesocolic,  976 

of  neck,  956 

pract.  consid.,  959 

occipital,  945 

pancreatico-splenic,  975 

parotid,  946 

pectoral,  962 

of  pelvis,  pract.  consid.,  990 

popliteal,  992 

posterior  auricular,  945 

retro-pharyngeal,  948 

of  Rosenmuller,  992 

sternal,  966 

structure  of,  937 

submaxillary,  946 

submental,  946 

subscapular,  962 

superficial  cervical,  956 

thorax,  pract.  consid.,  971 

tibial,  anterior,  993 

tracheal  nodes,  967 

umbilical,  972 
Lymph-nodules,  936 
Lymphocytes,  931 

varieties  of,  685 
Lymphoid  structures  of  pharynx,  1599 

tissue,  structure  of,  936 
Lymph-spaces,  93 1 
Lymph-vessels,  934 
Lyra,  11 58 

Macula  lutea,  1466 
Maculae  acustica?,  151 6 
Magendie,  foramen  of,  1100 
Malar  bone,  209 

articulations  of,  210 
Malleus,  1497 

Malpighian  bodies  of  spleen,  1784 
Mammary  glands,  2027 

development  of,  2032 

lymphatics,  968 


THIS  VOLUME   CONTAINS    PAGES  1    TO  995. 


ioi6 


INDEX. 


Mammary  glands,  nerves  of,  2032 
pract.  eonsid.,  2033 
structure  of,  2029 
variations  of,  2033 
vessels  of,  2031 
Mandible,  211 

Manubrium  of  sternum,  155 
Marrow  of  bone,  90 
Mast-cells  of  connective  tissue,  74 
Mastoid  cells,  1504 

pract.  eonsid.,  150s 
process,  pract.  eonsid.,  150S 
Maturation  of  ovum,  1 6 
Maxilla,  inferior,  211 

development  of,  213 
structure  of,  213 
superior,  199 

antrum  of,  201 
articulations  of,  202 
development  of,  202 
Maxillary  sinus,  1422 
Meatus,  auditory,  internal,  181 
inferior,  of  nose,  1412 
middle,  of  nose,  141 1 
superior,  of  nose,  141 1 
Meckel,  diverticulum  of,  44 
Mediastinum,  anterior,  1833 
middle,  1833 
posterior,  1833 
pract.  eonsid.,  1833 
superior,  1833 
Medulla  oblongata,  1063 

central  gray  matter  of,   1073 
development  of,  1101 
internal  structure  of,  106S 
Medullary  folds,  26 
groove,  26 
sheath,  1001 
velum,  inferior,  1099 
superior,  1099 
Medullated  fibres,  1003 
Megakaryocytes,  689 
Meibomian  (tarsal)  glands,  1444 
Meissner,  corpuscles  of,  1017 

plexus  of,  1643 
Membrane  or  membranes,  Bowman's, 
I451 
of  Bruch,  1456 
cloacal,  1939 
costo-coracoid,  568 
crico-thyroid,  1813 
of  Demours,  1452 
Descemet's,  1452 
fenestrated,  77 
foetal,  30 

human,  35 
hyaloid,  1474 

interosseous,  of  tibia  and  fibula,  396 
mucous,  1528 
obturator,  341 

olfactory  (Schneiderian),  1414 
pharyngeal,  1694 
pleuro-pericardial,  1700 
pleuro-peritoneal,  1700 
of  Reissner,  1517 
of  Ruysch,  1456 
of  spinal  cord,  1022 
synovial,  of  joint,  no 
tectoria,  1521 
thyro-hyoid,  1815 
of  tympanum,  1494 
vitelline,  15 
vitrea,  1456 


Meninges  of  brain,  pract.  eonsid.,  1208 

lymphatics  of,  948 
Menstruation,  2012 
Merkel,  tactile  cells  of,  1016 
Mesencephalon,  1105 

development  of,  1 1 1 7 

internal  structure  of,  11 09 
Mesenteries,  1 7  4 1 
Mesenterium  commune,  1697 
Mesentery,  anterior,  1744 

of  appendix,  1665 

of  jejuno-ileum,  1650 

of  large  intestine,  1670 

permanent,  1752 

posterior,  part  1st,  1746 
part  2nd,  1 75 1 
part  3rd,  1753 

primitive,  1697 
Meso-appendix,  1665 
Mesocolon,  1670 

development  of,  1704 
Mesoblast,  23 

lateral  plates  of,  29 

paraxial,  29 

parietal  layer,  29 

visceral  layer,  29 
Mesogastrium,  1697 
Mesognathism,  229 
Mesometrium,  2005 
Mesonephros,  193  5 
Mesorarium,  2040 
Mesorchium,  2040 
Mesorhines,  1404 
Mesosalpinx,  1996 
Mesotendons,  471 
Mesot helium,  71 
Mesovarium,  1987 
Metabolism,  6 
Metacarpal  bones,  314 
Metacarpo-phalangeal  articulations,  327 
Metacarpus,  pract.  eonsid.,  319 
Metanephros  (kidney),  1937 
Metaphase  of  mitosis,  12 
Metaplasm,  8 
Metatarsal  bones,  428 
Metathalamus,  1126 
Meynert,  commissure  of,  1115 
Mid-brain,  1061 
Milk,  2030 
Milk-ridge,  2032 
Mitosis,  11 

anaphases  of,  13 

metaphase  of,  12 

prophases  of,  12 

telophases  of,  13 
Molar  teeth,  1546 
Moll,  glands  of,  1444 
Monorchism,  1950 
Monroe,  foramen  of,  1131 
Mons  pubis,  2021 

veneris,  2021 
Montgomery,  glands  of,  2028 
Morgagni,  columns  of,  1674 

hydatid  of,  2002 

sinus  of,  497 

valves  of,  1674 
Morula,  22 
Mouth,  1538 

floor  of,  pract.  eonsid.,  1593 

formation  of,  1694 

pract.  eonsid.,  1589 

roof  of,  228 

pract.  eonsid.,  1592 


THIS  VOLUME   CONTAINS    PAGES   1    TO  995. 


INDEX, 


1017 


Mouth,  vestibule  of,  1538 

Mucoid,  83 

Mucous  membranes,  1528 

structure  of,  1528 
Mullerian  duct,  2038 
Muscle  or  muscles,  abdominal,  515 
abductor  hallucis,  661 

minimi  digiti,  608 

minimi,  of  foot,  662 

pollicis,  608 
adductor  brevis,  626 

hallucis,  662 

longus,  626 

magnus,  628 

pollicis,  610 
anconeus,  589 

of  ankle,  pract.  consid.,  666 
antibrachial,  591 

post-axial,  598 

pre-axial,  592 
of  anus,  1675 
appendicular,  566 
of  arm,  pract.  consid.,  589 
arytenoid,  1826 
of  auricle,  i486 
auricularis  anterior,  483 

posterior,  483 

superior,  483 
axial,  502 
of    axilla  and  shoulder,  pract.  consid., 

579 
azygos  uvuls,  496 
biceps,  586 

femoris,  636 
brachial,  585 

post-axial,  588 

pre-axial,  586 
brachialis  anticus,  586 
brachio-radialis,  598 
branchiomeric,  474 
buccinator,  48S 
bulbo-cavernosus,  565 
of  buttocks,  pract.  consid.,  641 
cardiac,  462 
cervical,  542 
chondro-glossus,  1578 
ciliary,  1458 
coccygeus,  561,  1676 
compound  pinnate,  469 
compressor  urethrae,  565 
constrictor  inferior  of  pharynx,  1606 

middle  of  pharynx,  1605 

pharyngis  inferior,  499 
medius,  498 
superior,  497 

superior  of  pharynx,  1604 
coraco-brachialis,  575 
of  cranium,  pract.  consid.,  489 
cremaster,  519 
crico-arytenoid  lateral,  1825 

posterior,  1825 
crico-thyroid,  1824 
crural,  647 

post-axial,  655 

pre-axial,  648 
crureus,  640 
dartos,  1963 
deltoideus,  578 
depressor  anguli  oris,  487 

labii  inferioris,  485 
diaphragma,  556 
digastricus,  477 
dilator  pupilla?,  146c 


Muscle  or  muscles,  dorsal,  of  trunk,  507 
of  Eustachian  tube,  1503 
extensor  brevis  digitorum,  665 
pollicis,  602 

carpi  radialis  brevior,  598 
longior,  598 
ulnaris,  601 

communis  digitorum,  599 

indicis,  603 

longus  digitorum,  655 

longus  hallucis,  656 
pollicis,  603 

minimi  digiti,  600 

ossis  metacarpi  pollicis,  602 
of  face,  pract.  consid.,  492 
facial,  479 
femoral,  633 

post-axial,  638 

pre-axial,  636 
flexor  accessorius,  654 

brevis  digitorum,  of  foot,  660 
hallucis,  660 
minimi  digiti,  609 

digiti  of  foot,  664 
pollicis,  60S 

carpi  radialis,  593 

radialis  brevis,  597 
ulnaris,  594 

longus  digitorum,  651 
hallucis,  651 
pollicis,  596  . 

profundus  digitorum,  595 

sublimis  digitorum,  595 
of  foot,  659 

post-axial,  665 

pract.  consid.,  666 

pre-axial,  659 
gastrocnemius,  649 
gemelli,  630 
genio-glossus,  1578 
genio-hyoid,  1578 
genio-hyoideus,  545 
gluteus  maximus,  630 

medius,  631 

minimus,  633 
gracilis,  626 
of  hand,  606 

pre-axial,  607 
of  hip  and  thigh,  pract.  consid.,  642 
hypoglossal,  506 
hyo-glossus,  1578 
hyoidean,  480 

variations  of,  480 
iliacus,  624 
ilio-costalis,  508 
infraspinatus,  576 
intercostales  externi,  538 

interni,  539 
interossei  dorsales  of  foot,  664 
of  hand,  613 

plantares,  663 

volares,  612 
interspinales,  513 
intertransversales,  513 

anteriores,  547 

laterales,  521 
intratympanic,  1499 
involuntary,  arrectores  pilorum,  1394 

nerve-endings  of,  1015 
ischio-cavernosus.  564 
of  knee,  pract.  consid.,  645 
of  larynx,  1824 
latissimus  dorsi,  574 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


ioiS 


INDEX. 


Muscle  or   muscles,   of    leg,    pract.    consid., 
665 
levator  anguli  oris,  487 
scapulae,  571 

ani,  560,  1675 

labii  superioris,  487 

labii  superioris  alaeque  nasi,  485 

menti  (superbus),  485 

palati,  496,  1571 

palpebral  superioris,  502 
levatores  costarum,  540 
lingualis,  1579 
of  lips,  1540  - 
longissimus,  510 
longus  colli,  548 
of  lower  limb,  623 
lumbricales,  of  hand,  610 

of  foot,  662 
masseter,  474 
of  mastication,  474 

variations  of,  477 
metameric,  502 
multifidus,  512 
mylo-hyoideus,  477 
nasalis,  486 
non-striated,  blood-vessels  of,  456 

development  of,  457 

(involuntary),  454 

lymphatics  of,  456 

nerves  of,  456 

structure  of,  455 
obliquus  capitis  inferior,  514 
superior,  514 

externus,  517 

inferior,  504 

internus,  517 

superior,  504 
obturator  externus,  629 

internus,  629 
occipito-frontalis,  482 
omo-hyoideus,  544 
opponens  minimi  digiti,  608 

pollicis,  608 
orbicularis  oris,  486 

palpebrarum,  484 
orbital,  502 

of  palate  and  pharynx,  495 
palato-glossus,  497,  1579 
palato-pharyngeus,-  497,  1571 
palmaris  brevis,  607 

longus,  593 
pectinate,  of  heart,  695 
pectineus,  625 
pectoralis  major,  569 

minor,  570 
pelvic,  559 
perineal,  562 
peroneus  brevis,  658 

longus,  657 

tertius,  656 
of  pharynx,  1604 
pinnate,  469 
plantaris,  649 
platysma,  481 
popliteus,  655 
pronator  quadratus,  597 

radii  teres,  592 
psoas  magnus,  623 

parvus '(minor),  624 
pterygoideus  externus,  476 

internus,  47 6 
pyloric  sphincter,  1626 
pyramidalis,  517 


Muscle  or  muscles,  pyriformis,  561 
quadratus  femoris,  629 

lumborum,  521 
quadriceps  femoris,  639 
of  rectum,  1675 
rectus  abdominis,  516 

capitis  anticus  major,  549 

capitis  anticus  minor,  550 
lateralis,  547 
posticus  major,  513 
posticus  minor,  514 

externus,  503 

femoris,  639 

inferior,  503 

internus,  503 

superior,  503 
rhomboideus  major,  572 

minor,  572 
risorius,  487 
rotatores,  of  back,  513 
sacro-spinalis,  508 
salpingo-pharyngeus,  1606 
sartorius,  638 
scalene,  variations  of,  547 
scalenus  anticus,  546 

medius,  546 

posticus,  547 
of  scalp,  pract.  consid.,  489 
semimembranosus,  438 
semi-pinnate,  469 
semispinalis,  511 
semitendinosus,  638 
serratus  magnus,  571 

posticus  inferior,  541 

posticus  superior,  541 
of  soft  palate,  1570 
soleus,  649 

sphincter  ani,  external,  1676 
externus,  563 
internal,  1677 

pupillae,  1460 

vesical,  external,  1925 
internal,  1925 
spinalis,  511 

splenius,  510  ,'•'■•. 

stapedius,  480,  1499 
sternalis,  570 

sterno-cleido-mastoideus,  499 
sterno-hyoideus,  543 
sterno-thyroideus,  545 
striated,  attachments  of,  468 

blood-vessels  of,  464 

bursas  of,  471 

classification  of,  471 

development  of,  465 

form  of,  469 

general  considerations  of,  468 

lymphatics  of,  464 

nerves  of,  464 

nerve-supply,  general,  473 

structure,  general  of,  458 

variations,  461 

(voluntary),  457 
stylo-glossus,  1579 
stylo-hyoideus,  480 
stylo-pharyngeus,  495,  1606 
subclavius,  570 
subcostal,  539 
subcrureus,  640 
submental,  477 
subscapularis,  578 
supinator,  601 
supraspinatus,  575 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


INDEX. 


1019 


Muscle  or  muscles,  temporalis,  475 
tensor  fascia?  latae,  631 
palati,  479,  1570 
tympani,  479,  1499 
teres  major,  577 
minor,  576 
thoracic,  538 
thyro-arytenoid,  1825 
thyro-hyoideus,  545 
tibialis  anticus,  655 

posticus,  654 
of  tongue,  1577 
trachealis,  1835 
transversalis,  519 
transverso-costal  tract,  508 
transverso-spinal  tract,  5 1 1 
transversus  perinei  profundus,  565 
superficialis,  564 
of  tongue,  1579 
trapezius,  500 
triangularis  sterni,  540 
triceps,  588 
trigeminal,  474 
palatal,  479 
tympanic,  479 
of  trunk,  507 
of  upper  limb,  568 
vago-accessory,  495 
vastus  externus,  640 

internus,  640 
ventral,  of  trunk,  515 

voluntary,  motor  nerve-endings  of,  1014 
zygomaticus  major,  485 
minor,  485 
Muscle-fibre,  structure  of,  459 
Muscular  system,  454 

tissue,  general,  454 
Myelin,  1001 

Myelocytes,  of  bone-marrow,  92 
Myeloplaxes,  of  bone-marrow,  92 
Myometrium,  2008 
Myotome,  30 
Myxcedema,  1794 

Naboth, -ovules  of,  2008 
Nail,  structure  of,  1395 
Nail-bed;  1396 
Nail-plate,  1395 
Nails,  1394  ■ 

development  of,  1403 
Nares,  anterior,  1404 

posterior,  14 13 
Nasal  bone,  209 

articulations  of,  209 
development  of,  209 
cavities,  pract.  consid.,  14 17 
cavity,  223 

hiatus  semilunaris  of,  194 
infundibulum  of,  194 
meatus  inferior  of,  225 
middle  of,  225 
superior  of,  225 
chamber,  224 

fossa,'  blood-vessels  of,  1425 
floor  of,  1413 
lymphatics  of,  1426 
nerves  of,  1426 
roof  of,  1 41 2 
fossa?,  1409 
index,  1404 

mucous  membrane,  141 3 
septum,  223,  1410 
triangular  cartilage  of,  224 


Nasion,  228 

Nasmyth,  membrane  of,  1550 
Naso-lachrymal  duct,  1479 
Naso-optic  groove,  62 
Naso-pharynx,  1598 
Navel,  37 

Neck,  landmarks  of,  554 
pract.  consid.,  550 
triangles  of,  547 
Nephrotome,  30 

Nerve    or   nerves,    abdominal,    of   vagus, 
1272 
abducent,  1249 

development  of,  1379 
aortic  (sympathetic),  1364 
auditory,  1256 

development  of,  1379 
of  auricle,  1487 
auricular,  great,  1286 

posterior,  of  facial,  1254 
of  vagus,  1268 
auriculo- temporal,  of   mandibular,  1244 
of  bone,  94 

buccal,  of  mandibular,  1243 
calcanean,  internal,  1344 
cervical,  anterior  divisions  of,    1285 
cardiac  inferior,  of  vagus,   1270 

superior,  of  vagus,  1270 
first,  posterior  division  of,  1281 
posterior  divisions  of,  1281 
second,  posterior  division  of,  1281 
superficial,  1287 

third,  posterior  division  of,  1281 
cervico-facial,  of  facial,  1254 
chorda  tympani,  of  facial,  1253 
ciliary,  long,  of  nasal,  1234 
circumflex,  1307 

pract.  consid.,  1308 
of  clitoris,  2025 

coccygeal,  posterior  division  of,  1284 
of  cochlea,  membranous,  1521 
cochlear,  of  auditory,  1256 
of  cornea,  1452 
cranial,  12 19 

crural,  anterior  (femoral),  1327 
cutaneous   internal,   of  anterior  crural, 
1328 

middle,  of  anterior  crural,  1327 
perforating,     of    pudendal    plexus, 

1347 
dental,  inferior,  of  mandibular,  1245 

superior      anterior,     of    maxillary, 
1239 

middle,  of  maxillary,  1239 
posterior,  of  maxillary,  1238 
descendens  hypoglossi,  1277 
development  of,  1375 
digastric,  of  facial,  1254 
digital  of  median,  1301 
dorsal  of  clitoris,  13  51 

of  penis,  13  51 
of  epididymis,  194S 
of  external  auditory  canal,  1490 
external   cutaneous,  of  lumbar   plexus, 

i324 
of  eyelids,  1446 
facial,  1250,  1 2  51 

development  of,  1 3  7  S 

genu  of,  1 2  5 1 

pract.  consid.,  1255 
of  Fallopian  tube,  1999 
frontal,  1234 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


Nerve  or  nerves,  ganglionic,  of  nasal, 
1234 
genito-crural,  1322 
of  glands,  1536 
glosso-pharyngeal,  1260 

development  of,  1379 
gluteal,  inferior,  1333 

superior,  1333 
of  heart,  704 

hemorrhoidal,  inferior,  1350 
hypoglossal,  1275 

development  of,  1380 

pract.  consid.,  1277 
ilio-hypogastric,  1320 
ilio-inguinal,  132 1 
infratrochlear,  1235 
intercostal,  13 14 
intercosto-humeral,  13 17 
intermedius   of   Wrisberg,   of  facial, 

1250 
internal  cutaneous,  1303 

cutaneous  lesser,  1303 
interosseous  anterior  of  median,  1300 
of  kidney,  1886 
of  labia,  2024 

labial,  superior,  of  maxillary,  1240 
lachrymal,  1233 

laryngeal,   external,   of  superior  laryn- 
geal, 1270 

inferior  (recurrent)  of  vagus,  1270 

internal,  of  superior  laryngeal,  1270 

superior,  of  vagus,  1270 
of  larynx,  1S27 
lingual,  of  glosso-pharyngeal,  1264 

of  hypoglossal,  1277 

of  mandibular,  1244 
of  lips,  1542 
of  liver,  1 7 1 1 

lumbar,  posterior  divisions  of,   1282 
of  lungs,  1855 
of  mammary  glands,  2032 
mandibular,  (maxillary  inferior),  1242 
masseteric,  of  mandibular,  1242 
maxillary  (superior),  1237 
median,  1298 

branches  of,  1300 

pract.  consid.,  1301 
meningeal,  of  hypoglossal,  1277 

of  vagus,  1268 
mental,  of  inferior  dental,  1246 
of  muscle,  non-striated,  456 
muscular  of  glosso-pharyngeal,  1264 
musculo-cutaneous,  of  arm,  1298 

of  leg,  1338 
musculo-spiral,  1308 

branches  of,  1309 

pract.  consid.,  13 14 
mylo-hyoid,  of  inferior  dental,  1245 
nasal,  1234,  1235 

anterior,  1235 

external,  1235 

fossa,  1426 

internal  (septal),  1235 

lateral,  of  maxillary,  1240 

septum,  14 10 

superior  posterior,  of  sphenopala- 
tine ganglion,  1241 
naso-palatine,    of  spheno-palatine   gan- 
glion, 1 241 
of  nose,  r407 
obturator,  1324 

accessory,  1326 
occipital,  small,  12S6 


Nerve  or  nerves,  oculomotor,  1225 

development  of,  1377 
oesophageal,  of  vagus,  1272 
of  oesophagus,  1613 
olfactory,  1220 

development  of,  1376 

pract.  consid.,  1222 
ophthalmic,  1233 
optic,  1223 

development  of,  1482 

pract.  consid.,  1470 
orbital,  of  spheno-palatine  ganglion,  1241 
of  ovary,  1993 
of  palate,  1573 
palatine,    of   spheno-palatine    ganglion, 

1241 
palmar  cutaneous  of  median,  1301 
palpebral,  inferior,  of  maxillary,  1240 
of  pancreas,  1737 
of  parotid  gland,  1583 
of  penis,  197 1 
pericardial  of  vagus,  1272 
of  pericardium,  716 
perineal,  1350 

peripheral,  development  of,  ion 
peroneal,  communicating,     of    external 

popliteal,  1335 
petrosal,  deep,  small,  1264 

superficial,    external,    of    facial, 

1253 
great,  of  facial,  1252 
small,  1264 
pharyngeal  of  glosso-pharyngeal, 
1264 
of  vagus,  1269 
of  pharynx,  1606 
phrenic,  1290 
plantar  external,  1345 

internal,  1344 
of  pleuras,  1861 
popliteal,  external  (peroneal),  1335 

internal  (tibial),  1339 
posterior  interosseous,  13  n 
of  prostate  gland,  1978 
pterygoid,  external,  of  mandibular, 

1243 

internal,  of  mandibular,  1242 
pterygo-palatine     (pharyngeal),     of 

spheno-palatine  ganglion,  1242 
pudic,  1349 
pulmonary,  anterior,  of  vagus,  1272 

posterior,  of  vagus,  1272 

(sympathetic),  1364 
radial,  1313 
of  rectum,  1680 
recurrent,  of  mandibular,  1242 

of  maxillary,  1237 
respiratory,  external  of  Bell,  1295 
sacral,  posterior  divisions  of,  1282 
sacro-coccygeal,  1352 

posterior,  1283 
saphenous,  internal    (long),  of  anteriol 
crural,  1329 

short  (external),  1342 
scapular,  posterior,  1295 
sciatic,  great,  1335 

small,  1348 
of  scrotum,  1964 
of  skin,  1389 
of  small  intestine,  1643 
somatic,  12 18 
of  spermatic  ducts,  1959 
spheno-palatine,  of  rrjaxillary,  1237 


THIS   VOLUME   CONTAINS    PAGES   1    TO   995 


INDEX. 


Nerve  or  nerves,  spinal,  1278 
spinal-accessory,  1274 

pract.  consid.,  1275 
splanchnic,  (sympathetic),  1364 
of  spleen,  1787 
stapedial,  of  facial,  1253 
of  stomach,  1628 
of  striated  muscle,  464 
stylo-hyoid,  of  facial,  1254 
of  sublingual  gland,  1585 
of  submaxillary  gland,  1585 
subscapular,  1306 
supraorbital,  1234 
of  suprarenal  bodies,  1803 
suprascapular,  1295 
supratrochlear,  1234 
sural,  of  external  popliteal,  1335 
of  sweat  glands,  1400 
of  taste-buds,  1435 
temporal,  deep,  of  mandibular,  1243 

superficial,     of     auriculo-temporal, 
1244 
temporo-facial,  of  facial,  1254 
temporo-malar    (orbital),   of  maxillary, 

123S 
of  testis,  1948 
thoracic,  13 14 

anterior,  external,  1297 
internal,  1303 

branches  of,  13 17 

cardiac,  of  vagus,  1272 

first,  1315 

lower,  13 1 5 

posterior  divisions  of,  12S2 

posterior  (long),  1295 
pract.  consid.,  1296 

pract.  consid.,  13 18 

second,  13 17 

third,  13 1 7 

twelfth  (subcostal)  13 17 

upper,  13 1 5 
of  thyroid  body,  1793 
of  thymus  body,  1800 
thyro-hyoid,  of  hypoglossal,  1277 
tibial,  anterior,  1336 

communicating,  1342 

posterior,  1342 

recurrent,  1335 
of  tongue,  1  580 

tonsillar  of  glosso-pharyngeal,  1264 
of  trachea,  1836 
trigeminal,  1230 

development  of,  1378 

divisions  of.  1232 

pract.  consid.,  1248 
trochlear,  1228 

development  of,  1377 
tympanic,  of  glosso-pharyngeal,  1264 
to  tympanic  plexus,  of  facial,  1252 
ulnar,  1303 

branches  of,  1305 

pract.  consid.,  1306 
of  ureter,  1898 
of  urethra,  1927 
of  urinary  bladder,  1910 
of  uterus,  2010 
of  vagina,  2018 
vagus,  1265 

and  spinal  accessory,  development 
of,  1380 

ganglia  of,  1267 

pract.  consid.,  1272 
vestibular,  of  auditory,  1256 


Nerve  or  nerves,  visceral,  12 18 
Nerve-cells,  998 
bipolar,  999 
multipolar,  1000 
unipolar,  999 
Nerve-endings,  motor,  1014 

of  cardiac  muscle,  1015 
of  involuntary  muscle,  1015 
of  voluntary  muscle,  1014 
sensory,  10 15 

encapsulated,  10 16 
free,  1015 

genital  corpuscles,  10 17 
Golgi-Mazzoni  corpuscles,  1019 
Krause's  end-bulbs,  1016 
Meissner's  corpuscles,  1017 
Merkel's  tactile  cells,  1016 
neuromuscular  endings,  10 19 
neurotendinous  endings,  1020 
Ruffini's  corpuscles,  1017 
Vater-Pacinian  corpuscles,  10 18 
Nerve-fibres,  1000 
arcuate,  107 1 
axis-cylinder  of,  1001 
cerebello-olivary,  1072 
cerebello-thalamic,  11 14 
cortico-bulbar,  1 1 1 5 
cortico-pontine,  1115 
cortico-spinal,  n  15 
medullary  sheath  of,  1001 
medullated,  1003 
neurilemma  of,  1001 
nonmedullated,  1003 
rubro-thalamic,  11 14 
of  sympathetic  system,  1356 
Nerve-terminations,  10 14 
Nerve-trunks,  1006 

endoneurium  of,  1006 
epineurium  of,  1006 
funiculi  of,  1006 
perineurium  of,  1006 
Nervous  system,  996 
central,  102 1 
peripheral,  121S 
sympathetic,  1353 

development  of,  10 13 
tissues,  997 

development  of,  1009 
Neurilemma,  1001 
Neuroblasts,  1010 
Neuro-epithelium,  70 
Neuroglia,  1003 

ependymal  layer  of,  1004 
glia-fibres  of,  1004 
of  gray  matter,  of  spinal  cord,  1035 
histogenesis  of,  1010 
spider  cells  of,  1004 
Neurokeratin,  1001 
Neuromuscular  endings,  1019 
Neurone  or  neurones,  996 
axones  of,  997 
dendrites  of,  997 
histogenesis  of,  ion 
Neurotendinous  endings,  1020 
Nictitating  membrane,  1443 
Nipple,  2028 

Nodose,  ganglion  of  vagus,  12 68 
Nodules  of  Arantius,  700 
Nonmedullated  fibres,  1003 
Normoblasts,  92 
Nose,  1404 

blood-vessels  of,  1407 
cartilages  of,  1404 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


1022 


INDEX. 


Nose,  development  of,  1429 

hiatus  semilunaris  of,  141 1 

inferior  meatus  of,  141 2 

infundibulum  of,  141 1 

lateral  cartilages  of,  1405 

lymphatics  of,  1407 

middle  meatus  of,  141 1 

nerves  of,  1407 

olfactory  region  of,  1413 

pract.  consid.,  1407 

respiratory  region  of,  141 5 

superior  meatus  of,  1411 

vestibule  of,  1409 
nostrils,  1404 
Notochord,  27 
Nuck,  canal  of,  2006 
Nuclein,  9 
Nucleolus,  9 
Nucleus  or  nuclei,  abducent,  1249 

acoustic,  1257 

ambiguus,  1074 

amygdaloid,  1 1 7  2 

arcuate,  1076 

caudate,  1169 

cuneate,  1069 

facial,  1 2  51 

dentate,  of  cerebellum,  1088 

emboliformis   (embolus)    of  cerebellum, 
1089 

facial,  1 2  51 

fastigii,  of  cerebellum,  1089 

globosus,  of  cerebellum,  1089 

gracile,  1069 

internal,  of  cerebellum,  1088 

of  lateral  fillet,  1258 

lenticular,  11 69 

mammillaris,  n 29 

olivary,  1071 

olivary,  superior,  1257 

red,  1 1 14 

structure  of,  8 

trapezoideus,  1257 

vago-glosso-pharyngeal,  1073 

vestibular,  of  reception,  1259 
Nuhn,  glands  of,  1577 
Nutrition,  accessory  organs  of,  1781 
Nymphas,  2022 

Obelion,  228 
Obex,  1096 
Occipital  bone,  172 

lobe,  1 145 

protuberance,  external,  174 
internal,  175 
Odontoblasts,  1558 
(Esophagus,  1609 

course  and  relations  of,  1609 

lymphatics  of,  971 

nerves  of,  1613 

pract.  consid.,  1613 

structure  of,  1611 

vessels  of,  161 2 
Olecranon,  of  ulna,  281 
Olfactory  bulb,  1151 

cells,  1 4 14 

hairs,  141 5 

lobe,  1 151 

membrane,  1414 

pits,  62 

region  of  nose,  14 13 

strias,  1 1 53 

tract,  1 1 52 

trigone,  1 1 53 


Olivary  eminence,  1066 

nuclei,  1071 

accessory,  1072 

nucleus,  inferior,  1072 
Omental  sac,  1703 
Omentum,  duodeno-hepatic,  1746 

gastro-colic,  1747 

gastro-hepatic  (les«er),  1745 

gastro-splenic,  1747 

greater,  1747 

greater,  structure  of,  1749 
Oocyte,  primary,  1 7 

secondary,  1 7 
Ooplasm,  15 
Opercula  insula;,  113  7 
Ophryon,  228 
Opisthion,  228 
Optic  commissure,  1223 

entrance  or  papilla,  1462 

recess,  1132 

thalami,  111S 

tracts,  1223 
Ora  serrata,  1467 
Oral  cavity,  development  of,  62 

glands,  development  of,  1589 
Orbit,  222 

axes  of,  222 

fascia;  of,  504 

lymphatics  of,  949 

pract.  consid.,  143S 
Organ   or    organs,    accessory,    of   nutrition, 
1781 

of  Corti,  1 519 

genital,  external  female,  2021 

Jacobson's,  141 7 

reproductive  female,  1985 
male,  1941 

of  respiration,  1S13 

of  sense,  13S1 

of  taste,  1433 

urinary,  1869 
Oro-pharynx,  1598 
Orthognathism,  229 
Os  intermetatarseum,  432 

magnum,  312 
Osseous  tissue,  84 
Ossicles  auditory,  1496 

articulations  of,  1498 
incus,  1497 
malleus,  1497 
movements  of,  1500 
stapes,  1498 

of  ear,  development  of,  1525 
Ossification,  centres  of,  94 

of  epiphyses,  98 
Osteoblasts,  95 
Ostium  maxillare,  1422 
Otic  ganglion,  1246 
Ova  or  ovum,  1 5 

centrolecithal,  22 

fertilization  of,  18 

holoblastic,  22 

homolecithal,  21 

human,  1990 

maturation  of,  16 

meroblastic,  22 

primordial,  1993 

segmentation  of,  21 

stage  of,  56 

telolecithal,  22 

zona  pellucida  of,  1989 
Ovary  or  ovaries,  1085 

cortex  of,  1987 


THIS  VOLUME   CONTAINS    PAGES   1   TO   995. 


INDEX. 


1023 


Ovary  or  ovaries,  descent  of,  2043 

development  of,  1993 

fixation  of,  1986 

Graafian  follicles  of,  1988 

hilum  of,  19S5 

ligament  of,  1987 

medulla  of,  1988 

nerves  of,  1993 

position  of,  1986 

pract.  consid.,  1995 

surfaces  of,  1985 

suspensory  ligament  of,  1986 

structure  of,  1987 

vessels  of,  1992 
Oviduct,  1996 

Pacchionian  bodies,  1205 

depressions,  198 
Palate,  1567 
bone,  204 

articulations  of,  205 
development  of,  205 
hard,  1567 
lymphatics  of,  954 
nerves  of,  1573 
pract.  consid.,  1592 
soft,  1568 

muscles  of,  1570 
vessels  of,  1572 
Pallium,  development  of,  1189 
Palmar  aponeurosis,  606 

fascia,  606 
Pancreas,  1732 
body  of,  1733 
development  of,  1737 
ducts  of,  1736 
head  of,  1732  - 

interalveolar  cell-areas  of,  1735 
islands  of  Langerhans  of,  1735 
lymphatics  of,  979 
nerves  of,  1737 
pract.  consid.,  1738 
relations  to  peritoneum  of,  1736 
structure  of,  1734 
vessels  of,  1736 
Panniculus  adiposus,  1384 
Papilla  or  papillae,  circumvallate,  1575 
dental,  1558 
of  duodenum,  1720 
filiform,  1575 
fungiform,  1575 
lachrymal,  1478 
optic,  1462 
renal,  1875 
Paradidymis,  1950 
Parametrium,  2005 
Parathyroid  bodies,  1795 

structure  of,  1795 
Parietal  bone,  197 

articulations  of,  199 

impressions,  199 

lobe,  1 143 

Paroophoron,  2002 

Parotid  duct,  1583 

gland,  1582 

nerves  of,  1583 
relations  of,  1582 
structure  of,  1586 
vessels  of,  1 583 
Parovarium,  2000 
Patella,  398 

development  of,  400 
movements  of,  409 


Patella,  pract.  consid.,  416 
Peduncle,  cerebellar,  inferior,  1067 

cerebral,  1107 
Pelvic  girdle,  332 
Pelvis,  332 

development  of,  344 

diameters  of,  342 

diaphragm  of,   359 

index  of,  343 

joints  of,  337 

pract.  consid.,  350 

of  kidney,  1894 

landmarks  of,  349 

ligaments  of,  337 

lymphatics  of,  983 

position  of,  342 

pract.  consid.,  345 

sexual  differences,  343 

surface  anatomy  of,  345 

white  lines  of,  559 

as  a  whole,  341 
Penis,  1965 

corpora  cavernosa  of,  1966 

corpus  spongiosum  of,  1967 

crura  of,  19(37 

glans  of,  1968 

nerves  of,  197 1 

pract.  consid.,  1972 

prepuce  of,  1966 

structure  of,  1968 

vessels  of,  1970 
Pericsecal  fossas,  1666 
Pericardium,  714 

blood-vessels  of,  716 

ligaments  of,  716 

lymphatics  of,  716 

nerves  of,  716 

pract.  consid.,  716 
Perichondrium,  81 
Pericranium,  489 
Perilymph  of  internal  ear,  1514 
Perimetrium,  2009 
Perimysium,  458 
Perineal  body,  2046 
Perineum,  female,  2046 

lymphatics  of,  987 

male,  1915 

landmarks  of,  19 18 

triangular  ligament  of,  563 
Perineurium,  1006 
Periosteum,  89 

alveolar,  1553 
Peritoneum,  1740 

cavity,  lesser  of,  1749 

development  of,  1702 

of  large  intestine,  1670 

parietal,  anterior,  1742 
folds  of,  1742 
fossae  of,  1742 

pract.  consid.,  1754 
Perivascular  lymph-spaces,  931 
Pes  anserinus,  1252 

hippocampi,  11 65 
Petit,  triangle  of,  574 
Petro-mastoid    portion    of    temporal    bone, 

179 
Petrous    ganglion,     of    glosso-pharyngeal, 
1264 

subdivision,    of    petro-mastoid    bone, 
181 
Peyer's  patches,  1641 
Phalanges  of  foot,  432 

of  hand,  317 


THIS  VOLUME   CONTAINS    PAGES  1    TO  995. 


xo24 


INDEX. 


Phalanges  of  hand,  development  of,  318 
peculiarities,  318 
pract.  consid.,  320 
variations  of,  319 
Pharyngeal  pouches,  1695 
Pharynx,  1596 

development  of,  1603 
growth  of,  1603 
laryngo-,  1598 
lymphatics  of,  954 
lymphoid  structures  of,  1599 
muscles  of,  1604 
naso-,  1598 
nerves  of,  1606 
oro-,  1598 
pract.  consid.,  1606 
primitive,    1694 
relations  of,  1601 
sinus  pyriformis  of,  1598 
vessels  of,  1606 
Philtrum  of  lips,  1540 
Pia  mater,  of  brain,  1202 

of  spinal  cord,  1022 
Pigment-cells  of  connective  tissue,  74 
Pillars  of  fauces,  1569 
Pineal  body,  1124 
Pinna,  1484 
Pisiform  bone,  311 

Pituitary  body,  anterior  lobe  of,  1806 
development  of,  1808 
(hypophysis),  n 29 
Placenta,  49 

basal  plate  of,  51 
cotyledons  of,  50 
discoidal,  34 
foetal  portion,  50 
giant  cells  of,  51 
intervillous  spaces  of,  51 
marginal  sinus  of,  53 
maternal  portion,  51 
multiple,  34 
septa  of,  51 
vitelline,  32 
zonular,  33 
Placentalia,  34 
Plane,  frontal,  3 
sagittal,  3 
transverse,  3 
Plasma-cells  of  connective  tissue,  74 
Plasmosome,  9 
Plates,  tarsal,  1444 
Platyrhines,  1404 
Pleura  or  pleurae,  1858 

blood-vessels  of,  i860 

nerves  of,  1S61 

outlines  of,  1859 

pract.  consid.,  1864 

relations  to  chest-walls,  changes  in,  1863 

of  to  surface,  1859 
structure  of,  i860 
Plexus  or  plexuses,  aortic,  1373 
of  Auerbach,  1643 
brachial,  1292 

branches,  infraclavirular  of,  1297 

supraclavicular^  of,  1295 
constitution  and  plan  of,  1293 
pract.  consid.,  1294 
cardiac,  1367 

carotid  (sympathetic),  1360 
cavernous,  of  penis,  1374 
(sympathetic),  13  61 
cervical,  1285 

branches  of,  1285 


Plexus  or   plexuses,    cervical,    branches, 
communicating  of,  1289 
deep,  of,  1289 
descending  of,  1288 
muscular  of,  1289 
superficial  of,  1286 
supraacromial  of,  1289 
supraclavicular  of,  1288 
suprasternal  of,  1288 
pract.  consid.,  1292 
coccygeal,  1352 
cceliac,  1370 

lymphatic,  973 
coronary,  1368 
gastric,  1370 
hemorrhoidal,  1374 
hepatic,  1370 
hypogastric,  1373 

lymphatic,  984 
iliac,  lymphatic,  983 
inguinal,  lymphatic,  991 
lumbar,  13 19 

lymphatic,  973 
muscular  branches  of,  1320 
of  Meissner,  1643 
mesenteric  inferior,  1373 

superior,  1372 
oesophageal,  1272 
ovarian,  13  71 
pampiniform,  i960 
parotid,  1252 
pelvic,  1374 
phrenic,  13  71 
pract.  consid.,  1330 
prostatic,  1374 
pudendal,  1345 

branches,  muscular  of,  1346 
visceral  of,  1346 
pulmonary,  anterior,  1272 

posterior,  1272 
renal,  13  71 
sacral,  133 1 

branches,  articular  of,  1334 
collateral  of,  1332 
muscular  of,  1333 
terminal  of,  1334 
lymphatic,  984 
posterior,  1282 
pract.  consid.,  1352 
solar,  1368 
spermatic,  13  71 
splenic,  1370 
suprarenal,  13  71 
of  sympathetic  nerves,  1367 
tympanic,  1264 
utero-vaginal,  1374 
vesical,  1374 
Plica  fimbriata,  1573 

semilunaris,  of  eye,  1443 
sublingualis,  1573 
Polar  body,  first,  16 
second,  16 
Pons  Varolii,  1077 

development  of,  n  03 
internal  structure  of,  1078 
Pontine  flexure,  1062 

nucleus,  1078 
Portal  system  of  veins,  919 
Postaxial,  4 

Pouch  of  Douglas,  1743 
pharyngeal,  61 
recto-uterine  '1743 
recto-vesical,  1743 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


1025 


Poupart,  ligament  of,  523 
Preaxial,  4 
Pregnancy,  2012 
Prepuce  of  penis,  1966 
Primitive  streak,  24 

significance  of,  25 
Process  or  processes,  ciliary,  1457 
fronto-nasal,  62 
mandibular,  62 
maxillary,  62 
nasal,  mesial,  62 

lateral,  62 
styloid,  of  petrous  oone,  183 
uncinate  of  ethmoid,  193 
Processus  cochleariformis,  1S2 

vaginalis,  2041 
Proctodaeum,  1695 
Prognathism,  229 
Pronephros,   1934 
Pronucleus,  female,  16 

male,  20 
Prophases  of  mitosis,  1 2 
Prosencephalon,  1059 
Prostate  gland,  1975 

development  of,  1979 

lymphatics  of,  985 

nerves  of,  1978 

pract.  consid.,  1979 

relations  of,  1976 

structure  of,  1977 

vessels  of,  1978 
Proteins,  8 
Protoplasm,  7 
Protovertebrs,  29 
Psalterium,  11 58 
Pseudostomata,  72 
Pterion,  228 
Pterygoid  plate,  inner,  189 

outer,  189 
processes  of  sphenoid  bone,  189 
Pubes,  334 

Pulmonary  system  of  veins,  S52 
Pulp  of  teeth,  1554 
Pulvinar,  n  19 
Puncta,  lachrymal,  1478 
Pupil,  1459 

Purkinje  cells  of  cerebellum,  1090 
Putamen,  n  70 
Pyramid,  1065 

Pyramidal  tract,  in  medulla,  1075 
Pyramids,  decussation  of,  1064 

renal,  1876 
Pyrenin,  9 

Radius,  287 

development  of,  293 

landmarks  of,  296 

pract.  consid.,  293 

structure  of,  292 

surface  anatomy,  300 
Rami  communicantes  of  sympathetic  system, 

1356 
Ranvier,  nodes  of,  1001 
Rauber,  cells  of,  23 
Recto-uterine  pouch,  1743 
Recto-vesical  pouch,  1743 
Rectum,  1672 

blood-vessels  of,  1679 

growth  of,  1680 

lymphatics  of,  1680 

muscles  and  fascia?  of,  1675 

nerves  of,  1680 

peritoneal  relations  of,  1679 


Rectum,  pract.  consid.,  1689 

structure  of,  1674 

valves  of,  1674 
Reduction  division,  18 
Reil,  island  of,  1149 

limiting  sulcus  of,  1139 
Reissner's  fibre,  1030 

membrane,  of  cochlea,  1517 
Remak,  fibres  of,  1003 
Renal  duct,  1894 
Reproduction,  6 

Reproductive   organs,    development   of, 
2037 
external,     female,     lymphatics 
of,   987 
male,  lymphatics  of,  986 
female,  1985 
internal,  female,  lymphatics  of,  gi 

male,  lymphatics  of,  987 
male,  1941 
Respiration,  organs  of,  181 3 
Respiratory  region  of  nose,  1415 

tract,  development  of,  1861 
Restiform  body,  1067 
Rete  Malpighi,  1386 
Reticular  tissue,  75 
Reticulin,  83 
Retina,  1462 

blood-vessels  of,  1467 

development  of,  1482 

lymphatics  of,  146S 

pars  optica  of,  1462 

pract.  consid.,  1468 

structure  of,  1463 
Retro-colic  fossa,  1667 
Retzius,  prevesical  space  of,  525 

space  of,  1906 

veins  of,  924 
Rhinencephalon,  n  51 

development  of,  1193 
Rhombencephalon,  derivatives  of,  1063 
Ribs,  149 

asternal,  150 

exceptional,  152 

floating,  150 

pract.  consid.,  169 

sternal,  150 

variations  of,  153 
Right  lymphatic  duct,  945 
Rima  glottidis,  1820 
Ring,  abdominal,  external,  524 
internal,  524 

femoral  (crural),  1773 
Riolan,  muscle  of,  484 
Rivinus,  ducts  of,  15S5 

notch  of,  1493 
Rolando,  fissure  of,  113  7 

funiculus  of,  1067 
Rosenmuller,  fossa  of,  1598 

lymph-nodes  of,  992 

organ  of,  2000 
Rostrum,  of  corpus  callosum,  n  56 

of  sphenoid  bone,  187 
Ruffini,  corpuscles  of,  1017 
Ruysch,  membrane  of,  1456 

Sac,  conjunctival,  1443 

lachrymal,  1478 

vitelline,  32 
Saccule,  1515 

structure  of,  1516 
Sacral  lymphatic  plexus,  984 
Sacro-iliac  articulation,  338 


THIS  VOLUME   CONTAINS    PAGES   1    TO   995. 


1026 


INDEX. 


Sacro-sciatic  ligaments,  339 
Sacrum,  124 

development  of,  129 
sexual  differences  of,  127 
variations  of,  127 
Salivary  glands,  1582 

structure  of,  1585 
Santorini,  cartilages  of,  181 7 

duct  of,  1736 
Saphenous  opening,  63  5 
Sarcolemma,  459 

Sarcous  (muscular)  substance,  459 
Scala  tympani,  1514 

vestibuli,  1514 
Scalp,  lymphatics  of,  948 

muscles  and  fasciae,  pract.  consid.,  489 
Scaphoid,  309 

bone  of  foot,  425 

development  of,  426 
Scapula,  248 

development  of,  253 
landmarks  of,  255 
ligaments  of,  256 
pract.  consid.,  253 
sexual  differences,  252 
structure  of,  253 
Scapuloclavicular  articulation,  262 
Scarpa,  canals  of,  201 
fascia  of,  515 
ganglion  of,  1259 
triangle  of,  639 
Schlemm,  canal  of,  1452 
Schwann,  sheath  of,  1001 
Sclera,  1449 

development  of,  14S2 
pract.  consid.,  1453 
structure  of,  14  50 
Sclerotome,  30 
Scoliosis,  144 
Scrotum,  1961 

dartos  muscle  of,  1963 
nerves  of,  1964 
pract.  consid.,  1964 
raphe  of,  1962 
tunica  vaginalis  of,  1963 
vessels  of,  1964 
Segmentation,  21 
complete,  22 
equal,  22 
partial,  22 
Sella  turcica,  186 
Semilunar  bone,  310 

cartilages  of  knee-joint,  402 
valves,  700 
Seminal  vesicles,  1956 

lymphatics  of,  988 
pract.  consid.,  1959 
relations  of,  1957 
structure  of,  1958 
vessels  of,  1958 
Seminiferous  tubules,  1942 
Sense,  organs  of,  1381 
Septum  or  septa,  aortic,  707 
auricular,  694 
crurale  (femorale),  625 
intermedium,  706 
intermuscular,  470 
interventricular,  696 
lucidum,  1 1 59 

median,  posterior,  of  spinal  cord,  10: 
nasal,  1410 

cartilage  of,  140  5 
placental,  51 


Septum  or  septa,  primum,  706 
secundum,  708 
spurium,  707 
transversum,  1701 
Serosa,  31 

Sertoli,  cells  of,  1943 
Sesamoid  bones,  104 
of  foot,  432 
of  hand,  318 
Sharpey's  fibres  of  bone,  87 
Shoulder,    muscles    and    fascia    of,     pract 

consid.,  579 
Shoulder-girdle,  248 

surface  anatomy  of,  263 
Shoulder-joint,  274 
bursas  of,  277 
dislocation  of,  582 
landmarks  of,  280 
ligaments  of,  274 
movements  of,  277 
pract.  consid.,  278 
Shrapnell's  membrane,  1494 
Sigmoid  cavity,  greater,  of  ulna,  281 
lesser,  of  ulna,  281 
flexure,  1669 

peritoneal  relations  of,  1671 
pract.  consid.,  1685 
Sinus  or  sinuses,  basilar,  874 
pract.  consid.,  874 
cavernous,  872 

pract.  consid.,  873 
circular,  872 
confluence  of,  868 
of  dura  mater,  867 
frontal,    i423'>   22<5  (bony) 
development  of,  1432 
pract.  consid.,  1427 
intercavernous,  S72 
lactiferus,  2030 
lateral,  867 

pract.  consid.,  869 
longitudinal,  inferior,  871 
superior,  870 

pract.  consid.,  870 
marginal,  872 

of  placenta,  53 
maxillary,  1422;   20   (bony) 
development  of,  1431 
pract.  consid.,  1428 
of  Morgagni,  497 
occipital,  872 
palatal,  1425 
petrosal,  inferior,  874 

superior,  874 
pocularis,  1922 
praecervicalis,  61 
pyriformis  of  pharynx,  1 598 
renal,  1874 
reuniens,  707 
sigmoid,  868 
sphenoidal,  1425 

pract.  consid.,  142S 
spheno-parietal,  874 
straight,  872 
uro-genital,  1939 
of  Valsalva,  700 
venosus,  705 
Skeleton,  103 

appendicular,  104 
axial,  103 
Skene,  tubes  of,  1924 
Skin,  blood-vessels  of,  1387 
development  of,  1400 


THIS  VOLUME   CONTAINS   PAGES  1   TO  995. 


INDEX. 


1027 


Skin,  end-bulbs  of  Krause,  1389 
end-organs  of  Ruffini,  1389 
genital  corpuscles,  1389 
Golgi-mazzoni  corpuscles,  1389 
lymphatics  of,  1388 
Meissner's  corpuscles,  13S9 
nerves  of,  1389 
pigmentation  of,  1387 
stratum  corneum  of,  13S7 

germinativum  of,  1385 

granulosum  of,  1386 

lucidum  of,  1386 
structure  of,  1382 
Vater-Pacinian  corpuscles,  1389 
Skull,  172 

alveolar  point  of,  228 
anthropology  of,  228 
asymmetry,  230 
auricular  point  of,  228 
capacity  of,  230 
changes  in  old  age,  233 
chordal  portion,  28 
dimensions  of,  229 
fontanelles  of,  231 
glenoid  point  of,  228 
growth  and  age  of,  230 
index,  cephalic  of,  229 

facial  of,  229 

of  height  of,  229 

nasal  of,  229 

orbital  of,  229 

palatal  of,  229 
landmarks  of,  240 
malar  point  of,  228 
mental  point  of,  22S 
occipital  point  of,  '228 
pract.  consid.,  235 
prechordal  portion,  2S 
sexual  differences,  234 
shape  of,  229 
subnasal.  point  of,  229 
surface  anatomy,  234 
weight  of,  233 
as  whole,  216 
Smegma,  1966 

Solitary  nodules  of  Intestine,  1 640 
Somatopleura,  29 
Somites,  29 

Space  or  spaces,  of  Burns,  543 
of  Fontana,  1452 
perforated,  anterior,  1153 

posterior,  1 107 
quadrangular,  of  m.  teres  major,  57$ 
of  Retzius,  1906 

subarachnoid,  of  spinal  cord,  1022 
subdural,  of  spinal  cord,  1022 
sublingual,  1581 
of  Tenon,  1437 

triangular,  of  m.  teres  major,   57s 
Spermatic  cord,  i960 

constituents  of,  i960 

pampiniform  plexus  of,  i960 

pract.  consid.,  1961 
ducts,  1953 

nerves  of,  1959 

structure  of,  1956 

vessels  of,  1958 
filaments,   1946 
Spermatids,  1944 
Spermatocytes,  primary,  1944 

secondary,  1944 
Spermatogenesis,  1944 
Spermatogones,  1944 


Spermatozoa,  1946 
Spermatozoon,  16 
Sperm-nucleus,  20 
Spheno-ethmoidal  recess,  141 1 
Sphenoid  bone,  186 

articulations  of,  190 
development  of,  190 
great  wings  of,  187 
lesser  wings  of,  188 
pterygoid  processes  of,  1S9 
Sphenoidal  sinus,  1425 
Spheno-palatine  ganglion,  1240 
Spigelius,  lobe  of,  1707 
Spinal  column,  114 
Spinal  cord,  1021 

anterior  horn,  nerve-cells  of,    1030 
arachnoid  of,  1022 
blood-vessels  of,  1047 
cauda  equina  of,  1025 
central  canal  of,  1030 
columns  of,  1027 
anterior,  1027 
lateral,  1027 
posterior,  1027 
commissure,  gray  of,  1028 

white,  anterior  of,  1028 
conus  medullaris,  102 1 
denticulate  ligaments  of,  1023 
development  of,  1049 
dura  mater  of,  1022 
enlargement,  cervical,  of,  1026 

lumbar  of,  1026 
fibre-tracts  of  white  matter,  1038 
fissure,  median  anterior  of,  1027 
form  of,  1026 
gray  matter  of,  1028 

nerve-fibres  of,  1036 
neuroglia  of,  1035 
ground-bundle,  anterior,  1046 

lateral,  1045 
horn,  anterior  of,  1029 
lateral  of,  1029 
posterior  of,  1029 
membranes  of,  1022 
microscopical  structure  of,    1030 
nerve-cells,  grouping  of,  1032 
pia  mater  of,  1022 
posterior  horn,  nerve-cells  of,  1033 
pract.  consid.,  1051 
root-line,  ventral  of,  1027 
segments  of,  1024 
septum,  median  posterior  of,   1027 
substantia   gelatinosa    Rolandi    of, 

1029 
sulcus  postero-lateral  of,  1027 
tract,   anterior  pyramidal   (direct), 
1046 

of  Burdach,  1039 

direct  cerebellar,  1044 

of  Goll,  1039 

of  Gower,  1044 

lateral     (crossed     pyramidal), 

1043 
of  Lissauer,  1042 
white  matter  of,  1036 
ganglia,  1279 
nerves,  1278 

constitution  of,  127S 

divisions,  primary,  anterior,  of,  1284 

posterior,  of,  1279 
number  of,  1279 
size  of,  1279 
typical,  1284 


THIS  VOLUME  CONTAINS    PAGES  1   TO  995. 


I02S 


INDEX. 


Spinal  nerves,  ventral  (motor)  roots  of,  1279 
Spine,  114 

articulations  of,  132 

aspect,  anterior  of,  138 
lateral  of,  138 
posterior  of,  138 

curves  of,  138 

dimensions  and  proportions  of,  141 

landmarks  of,  146 

lateral  curvature  of,  144 

ligaments  of,  132 

movements  of,  142 

practical  considerations,  143 

sprains  of,  144 

as  whole,  138 
Splanchnopleura,  29 
Splanchnoskeleton,  84 
Spleen,  1781 

development  and  growth  of,  1787 

lymphatics  of,  982 

movable,  1788 

nerves  of,  1787 

nodules   (Malphighian  bodies)   of,    1784 

peritoneal  relations  of,  1785 

pract.  consid.,  1787 

pulp  of,  1783 

structure  of,  1783 

surface  anatomy  of,  1787 
basal,  1782 
gastric,  1782 
phrenic,  1781 
renal,  1782 

suspensory  ligament  of,  1786 

vessels  of,  1786 
Spleens,  accessory,  1787 
Splenium,  of  corpus  callosum,  n  56 
Spongioblasts    10 10 
Spongioplasm,  8 
Sprains,  of  spine,  144 
Squamous  portion  of  temporal  bone,  177 
Stapes,  1498 
Stenson,  canals  of,  201 

duct,  1583 
Stephanion,  229 
Sterno-clavicular  articulation,  261 

pract.  consid.,  263 
Sternum,  155 

development  of,  157 

pract.  consid.,  168 

sexual  differences  of  156 

variations  of,  156 
Stigmata,  72 
Stilling,  .canal  of,  1474 
Stomach,  161 7 

blood-vessels  of,  1627 

curvature  greater  of,  161 7 

curvature  lesser  of,  161 7 

fundus  of,  1 61 8 

glands  of,  1623 

growth  of,  1629 

lymphatics  of,  976,  1628 

nerves  of,  1628 

peritoneal  relations  of,  1619 

position  and  relations  of,  1619 

pract.  consid.,  1629 

pylorus,  1 61 8 

shape  of,  161 8 

structure  of,  1621 

variations  of,  1629 

weight  and  dimensions  of,  1619 
Stomata,  72 
Stomodaeum,  1694 
Strabismus,  1440 


Stratum  zonale,  of  thalamus,  n  23 
Stria  medullaris,  n  19 
Strias,  acoustic,  1096 
Structure,  elements  of,  5 
Styloid  process  of  ulna,  285 
Sublingual  ducts,  1583 
gland,  1585 

nerves  of,  1585 
structure  of,  1587 
vessels  of,  1585 
space,  15S1 
Submaxillary  duct,  1584 
ganglion,  1247 
gland,  1583 

nerves  of,  1585 
structure  of,  1587 
vessels  of,  1585 
Subpatellar  fat,  405 
Subperiosteal  bone,  98 
Sub-peritoneal  tissue,  1742 
Substantia  nigra,  1109 
Sulci,  development  of,  1190 
fissures,  cerebral,  1135 
Sulcus  hypothalamicus,  n  19 
Suprarenal  bodies,  1801 
accessory,  1805 
development  of,  1804 
growth  of,  1804 
nerves  of,  1803 
pract.  consid.,  1806 
relations  of,  1801 
structure  of,  1802 
vessels  of,  1803 
body,  lymphatics  of,  983 
Suture  or  sutures,  107 
amniotic,  31 
coronal,  216 
cranial,  216 

closure  of,  233 
lambdoidal,  217 
sagittal,  216 
Sylvian  aqueduct,  nc8 
gray  matter,  1109 
Sylvius,  fissure  of,  1136 
Sympathetic  nerves,  plexuses  of,  1367 
Sympathetic  system,  1353 
aortic  nerves,  1364 
association  cords  of,  1357 
constitution  of,  1355 
ganglia  of,  1356 
gangliated  cord  of,  1355 
gangliated     cord,     cervico-cephalic 
portion,  1358 

lumbar  portion,  1366 
sacral  portion,  1367 
thoracic  portion,  1364 
nerve-fibres  of,  1356 
plexus,  aortic,  1372 
cardiac,  1367 
carotid,  1360 
cavernous,  13  61 
cavernous,  of  penis,  1374 
cceliac,  1370 
gastric,  1370 
hemorrhoidal,  1374 
hepatic,  1370 
hypogastric,   1374 
mesenteric,  inferior,  1373 

superior,  1372 
ovarian,  1372 
pelvic,  1374 
phrenic,  13  71 
prostatic,  1374 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


1029 


Sympathetic  system,  plexus,  renal,  137 1 
solar,  1368 
spermatic,  1372 
splenic,  1370 
suprarenal,  13  71 
utero-vaginal,  1374 
vesical,  1374 
plexuses  of,  1356 
pract.  consid.,  1375 
pulmonary  nerves,  1364 
rami  communicantes  of,  1356 
splanchnic  afferent  fibres  of,  1357 
efferent  fibres  of,  1357 
nerves,  1364 
Symphysis,  10S 
pubis,  339 
Synarthrosis,  107 
Synchondrosis,  108 
Syncytium  of  chorion,  49 
Syndesmosis,  108 
System,  gastro-pulmonary,  1527 
muscular,  454 
nervous,  996 
uro-genital,  1869 

Taenia  chorioidea,  1164 

coli,  1660 

fornicis,  11 63 

semicircularis,  n 62 

thalami,  11 19 
Tapetum,  11 57 
Tarsal  bones,  419 

plates,  1444 
Tarsus,  419 
Taste,  organ  of,  1433 
Taste-buds,  1433 

development  of,  1436 

nerves  of,  1435 

structure  of,  1434 
Teeth,  1542 

alveolar  periosteum,  1553 

bicuspids  (premolars),  1545 

canines,  1544 
milk,  1545 

cementum  of,  1552 

dentine  of,  1550 

development  of,  1556 

enamel  of,  1 548 

homologies  of,  1566 

implantation  and  relations  of,  1554 

incisors,  1543 
milk,  1544 

lymphatics  of,  951 

milk,  eruption  of,  1564 
(temporary),  1542 

molars,  1546 
milk,  1547 

neck  of,  1542 

permanent,  1542 

development  of,  1564 
eruption  of,  1565 
relations  of,  1554 

pract.  consid.,  1591 

pulp  of,  1554 

pulp-cavity  of,  1542 

temporary,,  relations  of ,  1536 

variations  of,  1566 
Tegmen  tympani,  1496 
Tegmentum,  1 1 1 2 
Tela  chorioidea,  1097 

subcutanea,  1384 
Telencephalon,  1132 
Telophases  of  mitosis,  13 


Temporal  bone,  176 

articulations  of,  184 
cavities  and  passages,  183 
development  of,  184 
portion,  petro-mastoid,  179 
squamous,  177 
tympanic,  179 
lobe,  1 147 
Temporo-mandibular  articulation,  214 
Tendo  oculi,  484 
Tendon,  77,  468 

conjoined,  518 
Tendon-cells,  78 
Tendon-sheaths,  470 
Tenon,  capsule  of,  504 

space  of,  1437 
Tentorium  cerebelli,  1199 
Terms,  descriptive,  3 
Testis  or  testes,  1941 

appendages  of,  1949 
architecture  of,  1942 
descent  of,  2040 
lymphatics  of,  987 
mediastinum  of,  1942 
nerves  of,  1948 
pract.  consid.,  1950 
structure  of,  1942 
tubules  seminiferous  of,  1942 
tunica  albuginea  of,  1942 
vessels  of,  1948 
Thalamic  radiation,  n 22 
Thalamus,  n  18 

connections  of,  1121 
structure  of,  n  20 
Thebesian  valve,  695 

veins,  694 
Theca  folliculi,  of  hair,  1392 
Thenar  eminence,  607 
Thigh,  landmarks  of,  670 

muscles  and    fascia;  of,   pract.   consid. 
642 
Third  ventricle,  1131 

choroid  plexus  of,  1131 
Thorax,  149 

articulations  of,  157 
in  infancy  and  childhood,  164 
landmarks  of,  170 
lymphatics  of,  966 
movements  of,  165 
pract.  consid.,  167 
sexual  differences,  164 
subdivisions  of,  1832 
surface  anatomy,  166 

landmarks  of,  1868 
as  whole,  162 
Thumb,  articulation  of,  326 
Thymus  body,  1796 

changes  of,  1797 
development  of,  1800 
nerves  of,  1800 
shape  and  relations  of,   1796 
structure  of,  1798 
vessels  of,  1799 
weight  of,  1797 
Thyroid  bodies,  accessory,  1793 
Thyroid  body,  1789 

development  of,  1793 
nerves  of,  1793 
pract.  consid.,  1794 
shape  and  relations  of,  1789 
structure  of,  1791 
vessels  of,  1792 
cartilage,  1814 


THIS  VOLUME   CONTAINS    PAGES   1   TO  995. 


1030 


INDEX. 


Thyroid   cartilage,   development   of, 
1815 
growth  of,  1815 

gland,  lymphatics  of,  959 
Tibia,  382 

development  of,  387 

landmarks  of,  390 

pract.  consid.,  387 

structure  of,  387 

variations  of,  383 
Tibio-fibular  articulation,  inferior,  396 

superior,  396 
Tissue  or  tissues,  adipose,  79 

connective,  73 

elastic,  76 

elementary,  67 

epithelial,  67 

fibrous,  74 

muscular,  general,  454 

nervous,  997 

osseous,  84 

reticular,  75 
Tongue,  1573 

foramen  caecum  of,  1574 

frenum  of,  1573 

glands  of,  1575 

growth  and  changes  of,  1580 

lymphatics  of,  952 

muscles  of,  1577 

nerves  of,  1580 

papilke,  circumvallate  of,  1575 
filiform  of,  1575 
fungiform  of,  1575 

pract.  consid.,  1594 

vessels  of,  1580 
Tonsil  or  tonsils  (amygdala),  of  cerebellum, 
1086 

faucial,  1600 

faucial,  relations  of,  1602 

lingual,  1575 

lymphatics  of,  954 

pharyngeal,  1601 

pract.  consid.,  1608 

tubal,  1503 
Tooth-sac,  1562 
Tooth-structure,  1548 
Topography,  of  abdomen,  531 

cranio-cerebral,  12 14 
Trachea,  1834 

bifurcation  of,  1S37 

carina  of,  1837 

growth  of,  1837 

lymphatics  of,  958 

nerves  of,  1836 

pract.  consid.,  1840 

relations  of,  1836 

structure  of,  1835 

vessels  of,  1836 
Tract   or  tracts,    (fibre)    rubro-spinal, 
1114 

habenulo-peduncular,  n  24 

mammillo-thalamic,  1121 

of  mesial  fillet,  1076 

olfactory,  n  52 

thalamocipetal,  lower,  1122 
Tragus,  1484 
Trapezium,  311 
Trapezoid  bone,  311 
Treitz,  muscle  of,  558 
Triangle  of  Hesselbach,  526 

rectal,  19 16 

uro-genital,  19 16 
Triangles  of  neck,  547 


Trigone  of  bladder,  urinary,  1904 
Trigonum  acustici,  1097 

habenulas,  n  23 

hypoglossi,  1097 

lemnisci,  1108 

urogenitale,  563 

vagi,  1097 
Trochanter,  greater,  of  femur,  352 

lesser,  of  femur,  3  53 
Trochlea  of  humerus,  268 

of  orbit,  504 
Trochoides,  113 
Trophoblast,  46 

Truncus    bronchomediastinalis,     lymphatic, 
968 

subclavius,  lymphatic,  963 
Tube,  Eustachian,  1501 
Tuber  cinereum,  1129 
Tubercle  of  Lower,  695 
Tuberculum  acusticum,  1097 

olfactorium,  11 53 
Tubes,  Fallopian,  1996 
Tunica  vaginalis  of  scrotum,  1963 
Turbinate  bone,  inferior,  208 

articulations  of,  208 
development  of,  208 
middle,  of  ethmoid,  193 
superior,  of  ethmoid,  193 
Tympanic  portion  of  temporal  bone,  179 
Tympanum,  1492 

attic  of,  1500 

cavity  of,  183 

contents  of,  1496 

membrane  of,  1494 

pract.  consid.,  1505 

mucous  membrane  of,  1500 

oval  window  of,  1495 

pract.  consid.,  1504 

promonotory  of,  1495 

pyramid  of,  1496 

round  window  of,  1495 

secondary  membrane  of,  149S 

tegmen  of,  1496 
Tyson,  glands  of,  1966 

"Ulna,  281 

development  of,  285 
landmarks  of,  287 
pract.  consid.,  285 
structure  of,  285 
surface  anatomy,  300 
Umbilical  cord,  53 

allantoic  duct  of,  54 
amniotic  sheath  of,  54 
blood-vessels  of,  54 
furcate  insertion  of,  55 
jelly  of  Wharton  of,  54 
marginal  insertion  of,  55 
velamentous  insertion  of,  55 
fissure  of  liver,  1708 
hernia,  1775 
notch  of  liver,  1707 
vesicle,  42 
Umbilicus,  37 
Unciform  bone,  312 
Uncus,  1 1 54 

Upper  limb,  muscles  of,  568' 
Urachus,  525 
Ureter  or  ureters,  1895 
female,  1896 
lymphatics  of,  982 
nerves  of,  189S 
pract.  consid.,  r8g8 


THIS  VOLUME   CONTAINS    PAGES  1    TO  995. 


INDEX. 


1031 


Ureter  or  ureters,  structure  of,  1896 
Ureteral  sheath,  1897 
Urethra,  1922 

crest  of,  1922 

development  of,  1938 

female,  1924 

structure  of,  1926 

fossa,  navicular  of,  1924 

glands  of,  1925 

lymphatics  of,  986 

male,  pract.  consid.,  1927 
structure  of,  1924 

meatus  of,  1924 

nerves  of,  1927 

orifice  of,  external,  1924 
internal,  1904 

portion,  membranous  of,  1923 
prostatic  of,  1922 
spongy  of,  1923 

vessels  of,  1926 
Urethral  bulb,  1968 

crest,  1922 
Urinary  organs,  1869 

development  of,  1934 
Uriniferous  tubule,  1877 
Urogenital  cleft,  2021 

sphincter,  2049 

system,  1869 
Utero-sacral  folds,  1743 
Utero- vesical  pouch,  1943 
Uterus,  2003 

attachments  of,  2004 

body  of,  2003 

broad  ligament  of,  2004 

cavity  of,  2003 

cervical  canal  of,  2003 

cervix  of,  2003 

changes  of  menstruation,  2012 
of  pregnancy,  2012 

development  of,  2010 

fundus  of,  2003 

glands  of,  2007 

lymphatics  of,  989 

nerves  of,  2010 

os,  external  of,  2003 

peritoneal  relations  of,  2004 

position  of,  2007 

pract.  consid.,  2012 

relations  of,  2007 

round  ligament  of,  2005 

structure  of,  2007 

variations  of,  2012 

vessels  of,  2009 
Utricle,  1514 

prostatic,  1922 

structure  of,  1516 
Uveal  tract,  1454 
Uvula,  1369 

Vagina,  2016 

development  of,  2019 

fornix,  anterior  of,  2016 
posterior  of,  2016 

lymphatics  of,  989 

nerves  of,  2018 

pract.  consid.,  2019 

relations  of,  2016 

structure  of,  2017 

variations  of,  2019 

vessels  of,  2018 

vestibule  of,  2022 
Vaginal    proc     ;   of    inner   pterygoid   plate, 


Vallecula  of  cerebellum,  1083 
Valsalva,  sinus  of,  700 
Valve  or  valves,  aortic,  700 

auriculo-ventricular,  of  heart,  699 
Eustachian,  694 
of  Hasner,  1479 
ileo-cscal,  1661 
mitral,  699 
of  Morgagni,  1674 
pulmonary,  700 
of  pulmonary  artery,  700 
rectal  (Houston's),  1674 
semilunar,  700 
Thebesian,  695 
tricuspid,  699 
Valvulae  conniventes,  1636 
Vasa  aberrantia  of  epididymis,  1950 
Vas  deferens,  1954 

ampulla  of,  1955 

lymphatics  of,  988 
Vasa  vasorum,  674 
Vater,  ampulla  of,  1721 
Vater- Pacinian  corpuscles,  10 18 
Vein  or  veins,  allantoic,  33 

circulation,  929 
angular,  of  facial,  864 
auditory,  internal,  869 
auricular,  anterior,  882 

posterior,  883 
axillary,  887 

pract.  consid.,  S88 
azygos,  8,93 

arch,  893 

development  of,  928 

major,  893 

minor,  895 

superior,  895 

pract.  consid.,  895 

system,  893 
basilar,  877 
basilic,  890 

median,  891 
basivertebral,  897 
brachial,  886 
brachio-cephalic,  858 
bronchial,  893 
cardiac,  854 

anterior,  S56 

great,  855 

middle,  856 

posterior,  856 

small,  856 

valves  of,  S56 
cardinal,  926 

posterior,  854 

superior,  854 

system  of,  854 
centralis  retina;,  S79 
cephalic,  890 

accessory,  S90 

median,  891 
cerebellar,  inferior,  879 

superior,  87S 

median,  878 
cerebral,  877 

great,  S77 

inferior,  877 

posterior,  869 

internal,  877 

middle,  877 

pract.  consid.,  878 

superior,  877 
cervical,  ascending,  of  vertebral,  860 


rms  VOLUME  CONTAINS    PAGES  1   TO  995. 


1032 


INDEX. 


Vein  1,1  veins,  cervical,  deep,  859 
middle,  884 
chordae  Willissi,  870 
choroid,  877 
ciliary,  anterior,  879 

posterior,  879 
circulation,  fcetal,  929 
circumflex,  iliac,  deep,  910 
superficial,  917 
of  leg,  914 
classification  of,  852 
clitoris,  909 
colic,  middle,  921 

right,  921 
condyloid,  anterior,  874 
confluence  of  the  sinuses,  868 
coronary,  of  facial,  865 
inferior,  of  facial,  86s 
left,  855 
right,  856 
of  corpus  callosum,  anterior,  878 
posterior,  877 
cavernosum,  907 
striatum,  877 
costo-axillary,  896 

crico-thyroid,   of  superior  thyroid,   867 
cystic,  923 

deep  dorsal  of  penis  (clitoris),  909 
of  forearm,  886 
of  hand,  886 
dental,  inferior,  883 

superior,  883 
development  of,  926 
diploic,  874 

anterior,  875 
occipital,  875 
pract.  consid.,  875 
temporal,  anterior,  875 
posterior,  875 
dorsal,  of  foot,  910 

interosseous,  886 
ductus  Arantii,  929 
arteriosus,  930 
Botalli,  930 
venosus,  929 
emissaries  of  foramen  lacerum  medium, 

876 
emissary,  S75 

condyloid,  anterior,  876 

posterior,  876 
of  foramen  ovale,  S76 

of  Vesalius,  876 
mastoid,  876 
occipital,  876 
parietal,  876 
pract.  consid.,  876 
epigastric,  deep,  909 
superficial,  917 

superior,  of  internal  mammary,  860 
ethmoidal,  S79 
facial,  864 

common,  864 
deep,  865 
pract.  consid.,  864 
transverse,  882 
femoral,  deep,  914 

pract.  consid.,  918 
fcetal  circulation,  929 
of  foot,  deep,  910 

superficial,  914 
foramen  lacerum  medium,  876 
frontal,  of  facial,  865 
of  Galen,  856 


Vein  or  veins,  gastric,  923 
short,  921 
gastro-epiploic,  left,  921 

right,  921 
gluteal,  905 
hemiazygos,  895 

accessory,  895 
hemorrhoidal,  inferior,  907 
middle,  908 
plexus,  908 
superior,  922 
hepatic,  902 

pract.  consid.,  904 
hepatica  communis,  900 
ileo-colic,  921 
iliac,  common,  905 

pract.  consid.,  917 
external,  909 

pract.  consid.,  918 
internal,  905 

pract.  consid.,  918 
ilio-lumbar,  906 
inferior  cava,  pract.  consid.,  900 

caval  system,  898 
innominate,  858 

development  of,  859 
pract.  consid.,  859 
intercapitular  of  hand,  889 
intercostal,  896 

anterior,  of  internal  mammary,  860 
superior,  896 

accessory  left,  896 
intervertebral,  S98 
jugular,  anterior,  884 
external,  880 

posterior,  884 
pract.  consid.,  88r 
internal,  861 

bulbs  of,  861 
prac.  consid.,  863 
labial,  inferior,  of  facial.  865 

superior,  865 
lacuna?  of  dural  sinuses,  852 
laryngeal,  inferior,  S61 

superior,   of  superior  thyroid,    867 
of  leg,  deep,  911 

pract.  consid.,  918 
of  limbs,  development  of,  929 
lingual,  deep,  of  facial,  867 

of  facial,  867 
lumbar,  901 

ascending,  901 
mammary,  external,  888 

internal,  860 
marginal,  right,  856 
marginalis  sinistra,  855 
of  Marshall,  S56 
masseteric,  of  facial,  866 
mastoid  emissary,  869 
maxillary,  internal,  882 

internal,  anterior,  of  facial,  865 
median,  890 

deep,  886 
mediastinal,  anterior,  861 
medulli-spinal,  S98 
meningeal,  middle,  883 
mesenteric,  inferior,  922 

superior,  921 
metacarpal,  dorsal,  889 
nasal,  lateral,  of  facial,  865 
oblique,  of  heart,  695 

of  left  auricle,  856 
obturator,  907 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


INDEX. 


1033 


Vein  or  veins,  occipital,  859 

ophthalmic,  anastomoses  of,  880 

inferior,  879 

pract.  consid.,  880 

superior,  8 79 
ovarian,  903 
palatine,  ascending,  of  faciai,  866 

inferior,  of  facial,  866 
palmar  arches,  886 
superficial,  890 
palpebral,  of  facial,  865 
pampiniform  plexus,  903 
pancreatic,  921 
pancreatico  duodenal,  921 
parotid,  anterior,  of  facial,  866 

posterior,  882 
parumbilical,  923 

perforating,  of  internal  mammary,  860 
pericardial,  861 
perineal,  superficial,  907 
peroneal,  911 
pharyngeal,  863 

plexus,  864 
phrenic,  inferior,  901 

superior,  861 
plantar,  910 

external,  910 
plexus,  alveolar,  882 

external,  spinal,  897 

hemorrhoidal,  venous,  908 

internal,  spinal,  S97 

pterygoid,  882 

sacral,  905 

of  Santorini,  909 

venosus  mammillae,  888 
popliteal,  911 

pract.  consid.,  918 
portal,  919 

accessory,  923 

collateral  circulation  of,  923 

development  of,  928 

of  liver,  1709 

system,  919 

pract.  consid.,  925 
pterygoid,  plexus,  882 
pudendal  plexus,  909 
pudic,  external,  916 

internal,  907 
pulmonary,  852 

anastomoses  of,  853 
pyloric,  923 
radial,  886 

superficial,  891 

accessory,  89 1 
*        renal,  902 

pract.  consid.,  904 
of  Retzius,  924 
sacral,  anterior,  plexus,  905 

lateral,  906 

middle,  905 
saphenous,  accessory,  916 

long,  916 

short,  915 
sciatic,  906 

of  septum  lucidum,  S77 
sigmoid,  922 
sinus,  basilar,  874 

pract.  consid.,  874 

cavernous,  872 

pract.  consid.,  873 

circular,  872 

coronary,  854 

of  dura  mater,  867 


Vein  or  veins,  sinus,  dural,  blood-lakes   of, 
852 
structure  of,  851 

intercavernous,  87 2 

lateral,  867 

pract.  consid.,  869 

longitudinal,  inferior,  871 
superior,  870 

pract.  consid.,  870 

marginal,  872 

occipital,  872 

petrosal,  inferior,  874 
superior,  874 

spheno-parietal,  874 

straight,  872 
small,  of  Galen,  S77 

intestine,  921 
spermatic,  903 

pract.  consid.,  904 
spheno-palatine,  882 
spinal,  897 

cord,  898 

pract.  consid.,  S98 
splenic,  921 
sterno-mastoid,    of   superior   thyroid 

867 
structure  of,  677 
subclavian,  884 

pract.  consid.,  885 
subcostal,  896 
sublingual,  867 
submental,  of  facial,  866 
superficial  of  hand,  889 
superior  caval  system,  857 
supraorbital,  of  facial,  865 
suprarenal,  middle,  903 

inferior,  902 
suprascapular,  884 
Sylvian,  deep,  878 
temporal,  deep,  883 

middle,  882 

superficial,  882 
temporo-maxillary,  882 
testicular,  903 
Thebesian,  694 
thoracic,  acromial,  890 

long,  8S7 
thoraco-epigastric,  888 
thymic,  861 
thyroid,  inferior,  860 

pract.  consid.,  861 

middle,  867 

plexus,  860 

superior,  867 
tibial,  anterior,  911 

posterior,  911 
torcular  Herophili,  868 
tympanic,  of  temporal,  S82 
ulnar,  886 

superficial,  890 
umbilical,  54 
of  upper  extremity,  886 

pract.  consid.,  891 
ureteric,  of  renal,  902 

of  spermatic,  903 
uterine,  908 

plexus,  908 
utero-vaginal  plexus,  908 
vaginal,  90S 

plexus,  908 
valves  of,  850,  851 
vena  cava  inferior,  S99 

development  of,  927 


THIS   VOLUME   CONTAINS    PAGES   1   TO   995. 


i°34 


INDEX. 


Vein  or  veins,  vena  cava  superior,  857 
development  of,  927 
pract.  consid.,  85S 
cephalica  pollicis,  889 
salvatella,  889 
supraumbilicalis,  923 
thyreoidea  ima,  861 
vense  comites,  851 
vorticosce,  879 
vertebral,  S60 
vesical,  908 

vesico-prostatic  plexus,  909 
vesico-vaginal  plexus,  909 
vitelline  circulation,  929 
Velum  interpositum,  11 62 
Ventricle  or  ventricles,  fifth,  1 1 60 
fourth,  1096 
of  heart,  696 
lateral,  1160 

anterior  horn  of,  n  60 

body  of,  1 1 6 1 

choroid  plexus  of,  1 1 62 

inferior    (descending)   horn   of, 

1 1 64 
posterior  horn  of,  1 1 68 
(sinus)  of  larynx,  1822 
third,  1 13 1 
Vermiform  appendix,  1664 
Vernix  caseosa,  66 
Vertebra  or  vertebra?,  114 
articular  surfaces  of,  116 
body  of,  115 
cervical,  116 
development  of,  128 
dimensions  of,  122 
gradual  regional  changes  of,  122 
lamina?  of,  ri5 
lumbar,  117 

mammillary  processes  of,  118 
peculiar,  119 
pedicles  of,  115 
presacral,  128 
prominens,  121 
spinal  foramen  of,  115 
spinous  process  of,  115 
structure  of,  128 
thoracic,  115 

transverse  processes  of,  115 
variations  of,  131 
Verumontanum,  1922 
Vesalius,  foramen  of,  188 
Vesicle,  germinal,  15 

umbilical,  42 
Vesicles,  seminal,  1956 
Vessels  of  clitoris,  2025 
of  epididymis,  1948 
of  Fallopian  tube,  1998 
of  gall-bladder,  1719 
of  labia,  2023 
of  larynx,  1826 
of  lips,  1542 

of  mammary  glands,  2031 
of  oesophagus,  161 2 
of  ovary,  1992 
of  palate,  1572 
of  pancreas,  1736 
of  parotid  gland,  15S3 
of  penis,  1970 
of  pharynx,  1606 
of  prostate  gland,  1978 
of  roots  of  lungs,  1839 
of  scrotum,  1964 


Vessels  of  seminal  vesicles,  1958 

of  spermatic  ducts,  1958 

of  spleen,  1786 

of  sublingual  gland,  1585 

of  submaxillary  gland,  1585 

of  suprarenal  bodies,  1803 

of  testis,  1948 

of  thymus  body,  1799 

of  thyroid  body,  1792 

of  tongue,  1580 

of  trachea,  1836 

of  ureter,  1897 

of  urethra,  1926 

of  urinary  bladder,  1910 

of  uterus,  2009 

of  vagina,  2018 
Vestibule  of  mouth,  1538 

of  nose,  1409 

of  osseous  labyrinth,  1511 

of  vagina,  2022 
Vicq  d'Azyr,  bundle  of,  1121 
Vidian  canal,  189 
Villi  of  chorion,  49 

of  intestine,  1635 
lacteals  of,  1636 
Vincula  tendinum,  471 
Vital  manifestations,  6 
Vitelline  arteries,  32 

duct,  32 

membrane,  1 5 

sac,  32 
Vitello-intestinal  duct,  37 
Vitellus,  15 
Vitreous  body,  1473 

pract.  consid.,  1474 
Vocal  cords,  false,  1820 

true,  1820 
Volkmann's  canals,  of  bone,  89 
Volvulus,  1687 
Vomer,  205 
Vulva,  2021 

Wharton,  duct  of,  1584 

jelly  of,  54 
White  lines  of  pelvis,  559 

of  anal  canal,  1673 
Winslow,  foramen  of,  1746 
Wirsung,  duct  of,  1736 
Wisdom-tooth,  1546 
Wolffian  body,  1935 

duct,  1935 
Womb,  2003 

Worm  of  cerebellum,  1082 
Wrist,  anterior  annular  ligament,  607 

movements  of,  326 

pract.  consid.,  613 

surface  anatomy  of,  328 
Wrist-joint,  landmarks  of,  330 

pract.  consid.,  329 

Xiphoid  process  of  sternum,  156 

Yolk-stalk,  37 

Zeiss,  glands  of,  1444 
Zinn,  annulus  of,  503 

zonula  of,  r  4  7  5 
Zona  pellucida,  1 5 

radiata,  15 
Zonula  of  Zinn,  1475 
Zuckerkandl,  bodies  of,  181 2 
Zygomatic  process  of  temporal  bone,  178 


THIS  VOLUME   CONTAINS    PAGES  1   TO  995. 


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